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2022 | Book

Proceedings of the RILEM International Symposium on Bituminous Materials

ISBM Lyon 2020


About this book

This volume highlights the latest advances, innovations, and applications in bituminous materials and structures and asphalt pavement technology, as presented by leading international researchers and engineers at the RILEM International Symposium on Bituminous Materials (ISBM), held in Lyon, France on December 14-16, 2020. The symposium represents a joint effort of three RILEM Technical Committees from Cluster F: 264-RAP “Asphalt Pavement Recycling”, 272-PIM “Phase and Interphase Behaviour of Bituminous Materials”, and 278-CHA “Crack-Healing of Asphalt Pavement Materials”. It covers a diverse range of topics concerning bituminous materials (bitumen, mastics, mixtures) and road, railway and airport pavement structures, including: recycling, phase and interphase behaviour, cracking and healing, modification and innovative materials, durability and environmental aspects, testing and modelling, multi-scale properties, surface characteristics, structure performance, modelling and design, non-destructive testing, back-analysis, and Life Cycle Assessment. The contributions, which were selected by means of a rigorous international peer-review process, present a wealth of exciting ideas that will open novel research directions and foster new multidisciplinary collaborations.

Table of Contents

Correction to: Proceedings of the RILEM International Symposium on Bituminous Materials

In the original version of the book, the following belated corrections have been Incorporated in chapter 156 and chapter 226 as follows:Chapter 156: The author first name and last name has been changed.Chapter 226: The missing author L.D. Poulikakos has been included now.The chapter and book have been updated with the changes.

Hervé Di Benedetto, Hassan Baaj, Emmanuel Chailleux, Gabriele Tebaldi, Cédric Sauzéat, Salvatore Mangiafico

Technical Committee 264-RAP (“Asphalt Pavement Recycling”)

Effect of Aging on the Rheological Properties of Blends of Virgin and Rejuvenated RA Binders

The use of rejuvenators has seen a consistent increase over the years in the asphalt pavement industry. This is due to the need for maximizing the demand for incorporating a higher amount of Reclaimed Asphalt (RA) in the pavement asphalt mixtures. In order to tackle this challenge, the Task Group 3, focusing on asphalt binders and additives, of the RILEM TC RAP conducted an interlaboratory activity to evaluate the effect of aging on blends of virgin and rejuvenated RA binders. A set of conventional tests including penetration value at 25 °C, softening point temperature and rheological measurements by means of Dynamic Shear Rheometer (DSR) were selected to involve a large number of participants. A binder, recovered from field RA, was treated with a bio-based rejuvenator and blended with a virgin binder to simulate recycling at three different percentages 60, 80, and 100%. These blends, as well as the pure virgin binder, were next short and long term aged and tested to evaluate the changes in the corresponding properties. Relatively consistent results were obtained for the entire set of blends. The aging of combined rejuvenated RA and virgin binders was comparable to that experienced for the pure virgin binder. DSR data provided a more precise evolution of the impact of aging on the materials.

Di Wang, Augusto Cannone Falchetto, Martin Hugener, Laurent Porot, Atsushi Kawakami, Bernhard Hofko, Andrea Grilli, Emiliano Pasquini, Marco Pasetto, Hassan Tabatabaee, Huachun Zhai, Margarida Sá da Costa, Hilde Soenen, Patricia Kara De Maeijer, Wim Van den Bergh, Fabrizio Cardone, Alan Carter, Kamilla L. Vasconcelos, Xavier Carbonneau, Aurelie Lorserie, Goran Mladenović, Marko Orešković, Tomas Koudelka, Pavel Coufalik, Edoardo Bocci, Runhua Zhang, Eshan V. Dave, Gabriele Tebaldi
Experimental Investigation on Water Loss and Stiffness of CBTM Using Different RA Sources

Cold recycling of reclaimed asphalt (RA) is a promising technique to build or to maintain roads, combining performance and environmental advantages. Although this technique has been extensively used worldwide, there is no unique and internationally-shared method to characterize cold recycled mixtures. The previous work of the RILEM TC 237-SIB TG6 successfully attempted to characterize different RA sources with both traditional parameters (gradation, bitumen content and geometrical properties) and non-conventional properties (fragmentation and strength testing). The current RILEM TC 264-RAP TG1 mainly focuses on the influence of different RA sources on physical and mechanical characteristics of cement-bitumen treated materials (CBTM) using foam or emulsified bitumen, taking into consideration compaction and curing methods. This paper presents results from the first step of the inter-laboratory project in which foamed bitumen and cement were used as binders. The influence of two RA sources, one from Alabama (USA) and one from San Marino, were investigated through the collaboration of several laboratories. Specimens were manufactured with the same diameter by means of both Marshall and gyratory compactors and then cured following two procedures: free surface drying (FSD) and partially-surface drying (PSD). A preliminary study allowed obtaining specimens with similar volumetric properties. Along with compactability and water loss, the indirect tensile stiffness modulus was measured and analyzed. The results have shown that the RA source and curing procedure influence the CBTM mechanical properties.

Andrea Grilli, Simone Raschia, Daniel Perraton, Alan Carter, Amir Rahmanbeiki, Patricia Kara De Maeijer, Davide Lo Presti, Gordon Airey, Chibuike Ogbo, Eshan V. Dave, Gabriele Tebaldi
International Evaluation of the Performance of Warm Mix Asphalts with High Reclaimed Asphalt Content

The Task Group 2 of the RILEM Technical Committee 264-RAP on non-cold recycling identified the need to gather some insights about possible durability issues associated with the combination of Warm Mix Asphalt (WMA) and of Reclaimed Asphalt (RA) in order to prioritize the characterization or research needs for relevant damage types. For this purpose, an international inter-laboratory testing program was launched in 5 different laboratories. This was developed on the basis of the challenges which a road material designer commonly faces: reduce the temperature, add RA, but preserve the same properties. Each laboratory characterized, according to its internal protocol, two variations of the same type of mixture (similar grading curve, binder content, etc.): a Hot Mix Asphalt (HMA) without RA taken as reference and a WMA with 40% RA. The performances of all the WMA with 40% RA are then compared in order to see if common trends emerge from the different characterization methods and reveal property issues specific to WMA + RA combinations.

Paul Marsac, Edoardo Bocci, Fabrizio Cardone, Augusto Cannone Falchetto, Xavier Carbonneau, Martins Zaumanis, Alan Carter, Ma Carmen Rubio-Gámez, Miguel Del Sol Sánchez, Eshan V. Dave, Gabriele Tebaldi

Technical Committee 272-PIM (“Phase and Interphase Behaviour of Bituminous Materials”)

Interlaboratory Test to Characterize the Cyclic Behavior of Bituminous Interlayers: An Overview of Testing Equipment and Protocols

The performance assessment of multi-layered pavements strongly depends on the mechanical behavior of the interface between bituminous layers. So far, comprehensive studies have been carried out mainly using quasi-static laboratory tests focusing on the interlayer shear strength at failure. However, it is generally recognized that cyclic shear testing will lead to the determination of parameters which are more closely linked to the performance of pavements under traffic loading than the quasi-static shear tests. This paper outlines the research work that has been carried out within the Task Group 3 “Pavement multilayer system” of the RILEM TC 272-PIM. The activities focused on cyclic shear testing of interfaces in bituminous pavements involve an interlaboratory test with nine participating laboratories. The interface behavior was investigated through both direct shear and torque tests on double-layered specimens extracted from lab compacted slabs prepared by one of the laboratories. The different testing equipment and protocols used by the participating laboratories are presented, highlighting the variety of geometries, loading modes, and testing parameters.

Francesco Canestrari, Thomas Attia, Hervé Di Benedetto, Andrea Graziani, Piotr Jaskula, Youngsoo Richard Kim, Maciej Maliszewski, Jorge C. Pais, Christophe Petit, Christiane Raab, Davide Ragni, Dawid Rys, Cesare Sangiorgi, Cédric Sauzéat, Adam Zofka
Complex Bituminous Binders, Are Current Test Methods Suitable for?

The asphalt industry is constantly working to enhance the performances of asphalt materials, introducing innovative and more sustainable solutions. In this context, the incorporation of materials, such as additives, polymers, is more and more used to improve the properties of neat bitumen. This leads to even more complex bituminous binders, raising the question, are the current specifications and test methods appropriate for complex materials? To deal with this, the RILEM Technical Committee 272-PIM ‘Phase and Interphase behaviour of innovative bituminous Materials’ with its Task Group TG1 is looking at the efficiency of various test methods for complex binders with an extensive inter-laboratory program with 17 laboratories. It includes seven different binders, two neat bitumen, two polymer modified bitumen and three binders with liquid additives, emphasising on compositional and physical changes at different conditions. The focus is low temperature; while a complementary experimental program encompasses as well as testing at intermediate and high temperatures. The outcomes of the work will provide indications on how robust the current binder characterisation techniques are and establish technical recommendations for future test methods specially designed for complex binders. Some first results are presented hereby.

Laurent Porot, Emmanuel Chailleux, Panos Apostolidis, Jiqing Zhu, Alexandros Margaritis, Lucia Tsantilis

Technical Committee 278-CHA (“Crack-Healing of Asphalt Pavement Materials”)

Terms and Definitions on Crack-Healing and Restoration of Mechanical Properties in Bituminous Materials

Fatigue damage is one of the main modes of deterioration of bituminous materials that leads to the failure of flexible pavements. However, it is well known that bituminous materials have some capability of recovering inflicted damage to some extent due to their viscoelastic nature. This process has been referred to as “self-healing”. Recently, research on crack-healing of bituminous materials has gained more importance and popularity due to the development of self-healing materials by materials scientists and engineers, that have been used in several applications. The Rilem Technical Committee TC 278-CHA (Crack-Healing of Asphalt Pavement Materials) was created in 2016 to tackle the challenges related to testing and evaluating the crack-healing properties of bituminous materials. However, the committee members noticed that there is no clear agreement within the scientific community about some basic terms to use when it comes to this new area of interest. Hence, this paper aims to clarify some of the concepts related to crack-healing and propose some common terms to the researchers and pavement engineers.

Greet Leegwater, Amir Taboković, Orazio Baglieri, Ferhat Hammoum, Hassan Baaj
Testing Methods to Assess Healing Potential of Bituminous Binders

Despite the fact that ability of bituminous materials to heal damage has been largely studied and that a wide literature is available on this topic, there is still no consensus in the research community on actual factors governing healing process and methods to be used to quantitatively asses healing performance of bituminous materials. In such a context, one of the main objectives of the RILEM Technical Committee 278-CHA is to evaluate the different test methods proposed by various research teams to characterize healing in bituminous materials and come up with clear and concise recommendations regarding the evaluation of healing behavior of bituminous materials in the laboratory. To this regard, an inter-laboratory experimental program has been recently started with the specific purpose of testing a common set of selected bituminous binders by using three different protocols. This paper describes the protocols adopted in the experimental program and reports some preliminary results obtained to date.

Orazio Baglieri, Hassan Baaj, Francesco Canestrari, Chao Wang, Ferhat Hammoum, Lucia Tsantilis, Fabrizio Cardone

Other Conference Papers

A Comparative Study of RTFO, PAV and UV Aging Using FT-IRS and DSR Tests

The objective of this study was to investigate RTRO (Rolling Thing Film Oven), PAV (Pressure Aging Vessel), UV (Ultraviolet), and forced draft oven aging behavior of original binder through dynamic shear rheometer (DSR) and FT-IRS (Fourier Transform Infrared Spectrometer). Different aging equipment, namely RTFO, PAV, UV chamber, and forced draft oven, were used to age the binder until equal stiffness (same G*/sinδ) was obtained. A comparison has been performed among these four aging procedures based on their differences in chemical and rheological properties. FT-IRS was used to envisage the chemical alteration, whereas DSR was used to perceive the rheological changes. Samples were prepared in RTFO at 163 °C and were collected at different degrees of RTFO aging. PAV, UV, and oven aged samples were prepared considering conditions without RTFO aging. Results showed that carbonyl (C=O) and sulfoxide (S=O) content of different degrees of RTFO and PAV aged samples increased with duration. On the other hand, C=O and S=O content in UV and oven aged samples decreased after 36 h of aging. At similar stiffness of RTFO and PAV aged binders, C=O content was similar, but S=O content was higher in PAV aged binders. DSR results also showed a resemblance with the FT-IRS results, which indicated that these different aging procedures with different equipment could be correlated with each other.

Roksana Hossain, Shams Arafat, Delmar Salomon, Nazimuddin M. Wasiuddin
A Critical Analysis of the Standard Used to Evaluate De-icing Damage in Asphalt Materials

De-icing fluids are known to have a potential to negatively affect infrastructure materials such as asphalt. In order to evaluate the resistance of asphalt materials to de-icing fluids, the European standard method EN 12697-41 is commonly used. There are however a number of issues related to the method, such as a high variability of the results and poor correlation between test results and behavior in the field, which may be caused by some of the parameters of the test. This paper aims to identify and investigate some parameters that are of importance to the relevancy of the test. To do this, experimental tests of asphalt mastic and mixture are performed with two concentrations of a deicer and water. Additionally, to gain a better understanding of what occurs in the tested samples during the conditioning and loading, finite element simulations using a microscale model with a mesh based on an X-ray CT scan of a real sample, are performed. The results show that both the geometry and the set-up of the conditioning and mechanical testing can cause misleading results. Based on this, recommendations are made for areas for future studies to improve the test method.

Lisa Lövqvist, Jiqing Zhu, Romain Balieu, Nicole Kringos
A Laboratory Procedure for Improving the Design of Road Rehabilitation Actions: Study of a Real Case in a Highway Pavement

Pavement rehabilitation has become an issue of major concern for road administrations. In the coming years, the development of more effective strategies for improving these actions will be crucial. On some occasions, traditional methods used to define pavement rehabilitation solutions are not able to select the best alternative from a sustainable, technical and economical point of view. Given these challenges, a new methodology was developed for use as a complementary tool for optimizing road pavement rehabilitation actions. This methodology is based on a comparative analysis of the structural behaviour of different types of materials and the subsequent selection of the best alternative based on the results obtained. The present paper describes the methodology and summarises its application during the rehabilitation of a highway pavement. The results of this study indicate that the use of this procedure could optimize the consumption of natural and economical resources in rehabilitation actions, offering more competitive alternatives when the available budget cannot cover the costs associated with traditional solutions.

Fernando Moreno-Navarro, J. Sierra, M. Sol-Sánchez, Ma Carmen Rubio-Gámez
A Literature Review of Bitumen Aging: From Laboratory Procedures to Field Evaluation

Bitumen aging increases the risk of pavement cracking. A good understanding of this phenomenon is crucial for designing long-lasting pavements. In this context, this paper presents a review of the relevant literature on neat bitumen aging. A broad set of indexes often used to estimate the aging level and end-of-life criteria of bitumen are analyzed and discussed.

Rodrigo Siroma, Mai Lan Nguyen, Pierre Hornych, Emmanuel Chailleux
A Method to Reduce Occlusion While Measuring Pavement Surface Profiles Using Triangulation Based Laser Scanners

One of the considerations, in the characterization of pavement surface, includes an accurate measurement of the pavement surface profile. With the advent of modern technologies, automated methods (such as laser scanning) are being preferred over manual methods (such as the sand patch test). The laser scanning measurement method is based on the principle of active triangulation, where a camera (laser detector), a laser emitter, and the illuminated laser spot form a triangle. However, due to obstruction from other nearby parts of the profile, this triangulation may not get completed for certain points of the surface profile, leading to occlusion of some data-points. In such a situation, generally, as per the current practice for pavement surfaces, interpolation is used to estimate the height of the occluded data points. In this study, an approach is suggested where two laser emitters are used (rather than one) to reduce this occlusion. Thus, even if the camera cannot see a point illuminated by one laser emitter, it may be able to capture the same point when it is illuminated by the other laser emitter. This minimizes (in some cases, altogether eliminates) occlusion. Experimental results are presented to support this approach.

Subham Jain, Animesh Das, K. S. Venkatesh
A New Approach to Calibration and Use of Mechanistic-Empirical Design Methods

Mechanistic empirical (M-E) pavement design methods have been available for practice since the late 1970s, and many agencies use them for design and analysis of new pavement and rehabilitation projects. The mechanistic part has typically been based on mechanics and laboratory testing, sometimes validated with data from well-instrumented accelerated pavement test (APT) sections. The empirical transfer functions have traditionally been calibrated with small numbers of field sections from which materials properties have been sampled. This paper presents a new approach for calibration, that provides better compatibility with pavement management systems and future use of performance related specifications.

Rongzong Wu, John T. Harvey, Jeremy Lea
A New Approach Towards Scientific Evaluation and Performance-Related Design of Bituminous Joint Sealing Materials and Constructions

While there is a permanent improvement of concrete pavement mixtures and pavement construction types over the last decades, the state-of-the-art joint sealing materials and joint constructions seem to stagnate on an antiquated empirical level. This status has been reaffirmed in the latest European standard. The consequences in the motorway network due to unsatisfying capability and durability of joint sealing systems are unacceptable. In addition, inadequate traffic performance (noise emissions, roll-over comfort) and traffic safety losses in the joint area of concrete pavements are existing challenges. These deficits and weaknesses reflect a demand for joint sealing materials and constructions whose approval requirements take functional aspects into account. Furthermore a sufficient analysis of decisive loads and a practice-oriented method to evaluate the requirements towards performance and durability is still missed. In this contribution decisive loads to German highways are analyzed. The design of test specimen for representative functional testing of joint sealing systems is discussed. The focus is on the geometry of the test specimens and the used concrete mixture. Finally, a new approach for a function-orientated test concept that considers representative load functions is presented. The potential of this approach to validate the durability and capability of various joint sealing systems is also presented using an example.

J. Buchheim, Ch. Recknagel, P. Wolter, K. Kittler-Packmor
A New Bituminous Ballast-Less and Sleeper-Less Thin Railway Track Structure

This paper presents a new structure design for a ballast-less and sleeper-less bituminous railway track. The structure is thinner than the conventional French tracks made with granular materials. This makes it especially suited for track renovation works in tunnels and other infrastructure configurations where the respect of the accurate and durable railway track geometry is essential. The proposed structure is a system associating a high-performance bituminous mixture, called GB5®, and the edilon)(sedra Embedded Rail System (ERS) using the Corkelast® resin as rail fastening system. This paper presents details of the components of the proposed structure and of its construction methodology. The system was submitted to mechanical tests to assess its aptitude to serve as rail fastening system in Europe, according to EN 13481 part 5 and EN 13146 part 9 test methods for non-ballasted rail fastening systems. The sample manufacturing and test protocols are described in this paper. The results from two tests are presented and analyzed. The system was found to be resilient and to meet the requirements of the European standard. Further analysis and large scale tests will give more insight into the behavior of the system, especially in terms of permanent deformation of the bituminous mixture and of the supporting soil.

Diego Ramirez Cardona, Simon Pouget, G. van der Houwen, M. Vlak, S. Sénéchal, N. Calon
A New Method for Healing Quantification of Bituminous Materials

During continuous and repeated loading, bituminous materials undergo damage. These materials also exhibit healing when enough rest periods are given between loadings. In this study, a new method is proposed to quantify the healing of bituminous materials based on the recovery of viscoplastic deformation. The method considers the damage in the material as a part of the viscoplastic deformation. Later, the method is applied to the data from the creep and recovery test to capture healing on both bitumen and bituminous mastic. Experiments are conducted at three stress levels using a dynamic shear rheometer (DSR). The strains accumulated during the creep and recovery period are segregated into the viscoelastic and viscoplastic strains. It is hypothesized that the recovery of viscoplastic strain in the material when subjected to prolonged rest period can be used to relate to healing.

Remya Varma, Romain Balieu, Nicole Kringos
A Numerical Model to Predict the Thermo-Viscoelastic Behaviour of Asphalt Concrete for Electric Road System

Dynamic on-road charging of vehicles can be done by conductive means, whose implementation require the presence of elements in the pavement, potentially affecting its durability. Some prototypes tested on site and in laboratory showed different mechanisms of damage: rutting, interface debonding and thermal cracking. Including different materials in an asphalt concrete (AC) can generate differential stress fields that can lead to premature failure. A thermal test was developed to simulate the behaviour of AC under daily thermal solicitations. This paper focuses on the development of a numerical simulation able to represent the stress field evolution in the AC. A Generalized Maxwell model coupled to WLF equation represented the thermo-viscoelastic behaviour of the AC under such conditions. This model was implemented into a FEM software named Cast3m®. First results show a stress concentration in the AC just under the groove. According to the design used for implementing ERS infrastructures, stress levels remain under acceptable values as to avoid damage.

Talita de Freitas Alves, Thomas Gabet, Jean-Michel Simonin, Ferhat Hammoum
A Numerical Study of the Influence of Aggregates Shape on Creep and Recovery Tests Behavior

Different ways to include aggregates in a hot mix asphalt concrete numerical model are investigated in this paper. Some geometrical approaches are adopted in order to evaluate their precision and efficiency. Packings of platonic solids are generated randomly, considering the average dimensions of real aggregates. In a complex method, 3D-scanned particles are used to generate meshes in random positions, to represent a more realistic shape approximation. The models consider the real shape indices, sizes and volume occupations of the sample. The construction of the virtual samples is presented in this paper. Creep and recovery tests were simulated with a finite element method (FEM) software and showed good agreement with experimental results. The virtual samples were validated using experimental data, so they could be used to stablish parametric correlations. The consideration of real aggregates shapes made the model very complex, but it was possible to evaluate the influence of different shapes of aggregates on creep behavior of asphalt mixtures.

Marcone de Oliveira Junior, Márcio Muniz de Farias, Carlos Alexander Recarey Morfa
A Simpler Method for Establishing an Approximate Value of Built-in Temperature Differential in Concrete Pavement

The effective temperature differential (ETD) across the thickness of the concrete pavement slab influences the magnitude of the combined stress due to curling and the wheel load. The built-in temperature differential (BiTD) value is necessary to estimate the ETD from the temperature differential (TD) value in the concrete slab measured during the test. However, it is very difficult to establish the actual BiTD in a concrete pavement during the construction time as both the temperature differential and the moisture differential (MD) in cement concrete (CC) layer influence it. The present paper uses a simpler method for establishing the approximate BiTD value using the TD value (measured during construction) alone as the MD value does not vary significantly in the first 24 h. In the present method, the TD is measured regularly in the freshly laid CC layer at an interval of one hour and the concrete strength gain is measured using the mortar penetration resistance plunger (as per ASTM C403). The TD is measured when the penetration resistance of plunger exceeds 4000 psi. Observations made during the construction of a CC pavement in the Jharkhand state in India during January 2018 are presented here. Though the BiTD measured in this method is not the actual BiTD as the MD is not taken into account, the measured BiTD value would be close to the actual value.

Venkata Joga Rao Bulusu, Sudhakar Reddy Kusam, Amarnatha Reddy Muppireddy
A Study on Fatigue Behaviour of Bitumen Emulsion Mastic, Modified with Active Fillers

The environmental and sustainability requirements necessitate to develop green road materials. Thus, Cold Bituminous Emulsion (CBE) mixtures have been developed to meet these requirements. Nevertheless, CBE mixtures have been considered inferior to hot asphalt mixture due to its poor early mechanical strength. For this reason, different active fillers have been used to obtain high early strength. There is, however, insufficient aware about the effect of active fillers on the fatigue cracking resistance. Therefore, it is interesting to investigate the effect of filler on the fatigue behaviour of CBE mastics. The aim of this study is to assess the resulted fatigue behaviour of CBE mastic due to the active filler inclusions. To address this aim, time sweep tests using Dynamic Shear Rheometer (DSR) with 8 mm diameter and 2 mm thickness specimen were performed. Seven types of fillers were incorporated to prepare the CBE mastics. In this regard, five different approaches to define fatigue life were used. Based on the tests results, it is evident that the presence of active fillers significantly increases fatigue life of CBE as compared to the neat CBE.

Ahmed Al-Mohammedawi, Konrad Mollenhauer
A Study on the Properties of Polyurethane-Elastomer-Modified Asphalt

A new type of elastomer-modified asphalt, polyurethane (PU)-elastomer-modified asphalt, was synthesized with polytetramethylene ether glycol (PTMEG) and diphenylmethane diisocyanate (MDI) as the main agents. The R value (–NCO/–OH) was 1.15. The polyurethane-elastomer-modified asphalt was prepared by adding different amounts of a polyurethane elastomer modifier to the asphalt using a high-speed emulsification shearing machine, and the properties of modified asphalt were characterized. The experimental results indicate that the performance of polyurethane-elastomer-modified asphalt has been significantly improved. Fluorescence microscopy indicated that the modifier could disperse well in asphalt. The dynamic shear rheological test (DSR), the ductility test and the multiple stress creep recovery test (MSCR) were used to analyze the asphalt samples. The results indicate that the high- and low-temperature performance of the asphalt was significantly improved.

Peng Wang, Jian Xu, Yongchun Qin, Erhu Yan, Jie Wang, Weiying Wang
A Wear-Based Description of Mechanisms Underlying the Bitumen Removal Process

The paper presents a study aiming at understanding the wear of a dense asphalt concrete, especially the behavior of its bitumen layer. Tests are conducted in laboratory to simulate mechanical actions induced by traffic. Friction and texture analyses are completed by microscopic observations to identify involved processes. Studying the variation of wear volume with energy dissipated by friction helps to estimate wear rates. Explanations are provided in terms of damage mechanisms occurred in the bitumen layer.

Minh-Tan Do, Veronique Cerezo, Christophe Ropert
Active Mitigation of Low-Temperature Cracking in Asphalt Pavements

Asphalt pavements in cold regions are often exposed to low-temperature cracking distress. The driving mechanism for this type of damage is usually an isolated event of fast surface cooling in combination with low-temperature levels. Another common characteristic of pavements in cold regions is the need for salting or mechanical clearing operations (or both) to address ice and snow events. An emerging solution to the latter issue is embedded heating systems—comprising of electric heating elements. These are commonly installed to help melt snow or prevent the accumulation of surface ice. This paper investigated an additional potential benefit of such heating systems—the ability to mitigate the development of low-temperature cracks. Thermomechanical calculations were carried out for an idealized pavement system modeled as a linear viscoelastic half-space. First, simulated winter-weather conditions were imposed to generate a surface crack at some point in time for a pavement without heating. Then after, the simulations were repeated—but with an active heating system. For the case considered, it is found that cracking can be potentially mitigated by the heating system if activated approximately half-an-hour before the time at which crack would occur.

Quentin Adam, Gerald Englmair, Eyal Levenberg, Asmus Skar
Ageing Behavior of Porous and Dense Asphalt Mixtures in the Field

Bitumen ageing is one of the principal factors causing the deterioration of asphalt pavements. As bitumen ages, the pavement loses its ability to relax stresses during loading/unloading and thermal cooling process, thus the risk of cracking increases. Oxidation and ultraviolet (UV) radiation are believed to be the main factors that can cause bitumen ageing during pavement service life. The aim of this study is to evaluate the mechanical behavior of porous and dense asphalt pavements during field ageing. Pavement test sections were constructed in 2014 and are being exposed to actual environmental conditions since then. To investigate the effect of UV radiation on ageing, UV reflective glass-plates were utilized to cover part of the pavement surface. To study the evolution of the pavements’ mechanical properties, asphalt cores were collected from the test sections periodically (at one-year intervals). The changes in the stiffness modulus of the mixtures were determined via cyclic indirect tensile tests. The results show that the effect of mineral aggregate packing, and hence of air-void distribution and connectivity, on the ageing sensitivity (both thermal and UV ageing sensitivity) of the pavements with time was found to be significant, as the changes of the stiffness of the porous mixtures were greater than that of dense mixtures.

Ruxin Jing, Aikaterini Varveri, Xueyan Liu, Athanasios Scarpas, Sandra Erkens
An Attempt to Characterize the RAP Material for Hot Recycled Mix Design Purposes

The design of bituminous mixes with high Reclaimed Asphalt Pavement (RAP) content requires the determination of aggregate gradation and the properties of recovered bitumen from RAP. However, in addition to requiring sophisticated equipment, it has been stated by many researchers and practitioners that the current recovery methods have certain other limitations. Hence, the present study focuses on the simple and practical tests from which the properties of the RAP material can be reasonably estimated. The fragmentation test protocol, which was recommended by the RILEM TC264 committee, was evaluated using six sources of RAP of varying properties. Based on test results, it was observed that the fragmentation value determined at 5 °C in combination with the black aggregate curve can be used to predict the percentage fines (<4 mm) in the extracted RAP aggregate (white aggregate curve). It was also observed that the rate of change of fragmentation value with temperature can be correlated to the physical properties of the bitumen extracted from the RAP material.

Gurunath Guduru, Kranthi Kuna
An Attempt to Distinguish Thermal from Oxidative Ageing of Asphalt Binders by NRTFOT

The ageing of asphalt pavements in the field is a thermo-oxidative degradative process that occurs over the pavement service life resulting in increase of stiffness and brittleness and thus, a decrease of resistance to fatigue and thermal cracking. Asphalt ageing can be separated into two phases, short-term (STA) and long-term ageing (LTA), respectively. STA occurs during the production and construction of the asphalt mixture. The high temperatures considered in those processes culminate in loss of volatile compounds and oxidation of the asphalt binder. The subsequent incorporation of oxygen into the asphalt binder is a slow oxidation mechanism related to the LTA during the service-life of a pavement. This study aims to understand and distinguish the effect of temperature and oxygen in the STA of a paving grade bitumen 70/100. For this purpose, the sample was short-term aged considering two distinct ageing procedures, the rolling thin film oven test (RTFOT) and a modified version of nitrogen rolling thin film oven test (NRTFOT). NRTFOT test considers the same procedure adopted in the RTFOT test, except that instead of air, nitrogen is blown into the oven to prevent any oxidative ageing. Fourier transform infrared spectroscopy (FTIR) and mass loss were considered to evaluate the ageing undergone by the asphalt binder during RTFOT and modified NRTFOT procedures. The asphalt binder aged in a nitrogen atmosphere has presented a reduction of its mass after the modified version of NRTFOT procedure. Standard RTFOT resulted in the increase of the material mass. The reduction in mass indicated that the binder only lost volatiles during the ageing in the modified version of NRTFOT; however, according to the infrared spectra, formation of carbonyl and sulfoxides compounds linked to oxidation was observed.

Ingrid Camargo, Bernhard Hofko, Johannes Mirwald, Hinrich Grothe
An Interlaboratory Test Program on the Extensive Use of Waste Aggregates in Asphalt Mixtures: Preliminary Steps

In view of increasing social and environmental consciousness, a circular approach in waste materials management in order to convert them into new secondary resources is becoming more necessary. Given this context, an interlaboratory testing program (ILTP) focusing on maximizing the use of waste aggregates replacing conventional virgin ones has been launched in the framework of the RILEM Technical Committee on “Valorisation of Waste and Secondary Materials for Roads”. Construction and demolition wastes, recycled concrete aggregates and steel slags were selected as waste aggregates to be investigated. A reference mixture prepared with natural virgin aggregates was also considered for comparison purposes. This paper describes the results achieved during the first steps of the ILTP concerning: (i) the basic characterization of the selected marginal aggregates; (ii) the Marshall mix design of different asphalt mixtures prepared with one or more waste aggregates. Overall, the experimental results collected during these preliminary steps seem to confirm that the selected marginal aggregates can be considered as valid alternatives for the traditional road materials, while not jeopardizing their performance.

Marco Pasetto, Emiliano Pasquini, Giovanni Giacomello, Fernando Moreno-Navarro, Raul Tauste-Martinez, Augusto Cannone Falchetto, Michel Vaillancourt, Alan Carter, Nunzio Viscione, Francesca Russo, Marta Skaf, Marko Orešković, Ana Cristina Freire, Peter Mikhailenko, Lily Poulikakos
An Investigation on Longitudinal Unevenness Indicators and Their Potential on Surface Characterisation

In the new European standard, EN 13036-5, several methods have been introduced in order to quantify the longitudinal unevenness. International roughness index (IRI), waveband analysis (NBO) and the weighted longitudinal profile (BLP) are the methods which are mentioned in the European standard. These methods have been introduced in the Swiss standard in 2017 in addition to the previous Swiss method, known as angle value W. The main objective of this paper is to utilise these indicators with real measured profile data in order to assess each of the aforementioned methods. For this purpose, the measured profile data from different road network types were chosen for the analysis. Initially, the results of analysis of road unevenness from these different sources are compared statistically. The results of this study show that no strong correlation between different longitudinal unevenness indicators exist since these indicators measure different wavelength range, and thus describe different physical phenomena. Therefore, different indicators should be used in order to characterise the surface of the pavement.

Parisa Rossel-Khavassefat, Jacques Perret, Mehdi Ould-Henia, Marc Delaby
An Overview of Black Space Evaluation of Performance and Distress Mechanisms in Asphalt Materials

Black space diagrams (BSD) representing rheological data of bituminous materials in the form of dynamic modulus (|G*| or |E*|) versus phase angle (δ) have been successfully used for interpretation of material behavior. Previous studies have used BSD for identification of testing geometry compliance errors when testing over multiple temperatures and loading times (frequencies); the screening of the “thermo-rheological simplicity” of various binders and mixtures, particularly with regards to the effect of polymer modification, wax content and oxidative ageing; and the detailed evaluation of the performance balance in term of “stiffness” versus “relaxation” needs. This overview paper details how these concepts and the Black space characterization of bituminous materials now include concepts of damage and healing (along with the effects of non-linearity, thixotropy and localized heating); the influence of the increased use of recycled asphalt pavement (RAP) proportions (along with effects of ageing and rejuvenation); and finally the fracture behavior and susceptibility limits for thermal, fatigue and durability cracking. New concepts such as the Glover-Rowe parameter that are based around BSD and linked to other forms of rheological indices such as the low temperature stiffness and relaxation rate parameters are introduced. Black space now provides a critical means of rheological characterization to investigate and evaluate the properties and performance of both binders and mixtures, particularly at a time when alternative binders (bio-binders, plastic modified binders, etc.) and increased pressures on re-use and recycling of materials in asphalt mixtures are becoming more prevalent.

Gordon Airey, Jo E. Sias, Geoffrey M. Rowe, Hervé Di Benedetto, Cédric Sauzéat, Eshan V. Dave
Analysis of a New Approach for Characterizing the Performance of Asphalt Binders Through the Multiple Stress Creep and Recovery Test

This research provides an efficient procedure for selecting and ranking binders to prevent rutting on asphalt pavements. Widely used to analyze asphalt binder permanent deformation, the Multiple Stress and Recovery (MSCR) test provides the non-recoverable compliance (Jnr). To evaluate the relation between Jnr from 6 different binders with the behavior of corresponding asphalt mixtures, this paper analyzes the Flow Number (FN) of 8 distinct mixtures. The MSCR standard protocol was compared to a new protocol (based on 30 loading cycles of 3.2 kPa) to verify Jnr and to obtain the non-recoverable strain rate (εnr). Different testing temperatures are considered. Correlations between Jnr from both MSCR test methodologies indicate a similar binder classification. The uniformity of the Jnr for the new test protocol with 30 constant loading cycles provides a more consistent average. For mixtures using the same binder with different aggregates and different grading curves, Jnr was a proper parameter to identify the potential for permanent deformation. However, an adequate choice of aggregate distribution enhances mixture mechanical behavior, which was evidenced when analyzing mixtures with distinct gradation but with the same binder.

Aline Vale, Juceline Bastos, Jorge B. Soares
Analysis of High Temperature Performance of Composite Asphalt Rubber Mixture

Asphalt rubber mixture is often described as an environmentally friendly mixture due to its usage of recycled rubber gotten from used tires and the subsequent improved service life. It has been established that adding SBS to rubber asphalt can further improve the performance of rubber asphalt mixture. In order to evaluate the performance improvement of the asphalt rubber mixture, several related high temperature performance and mechanical properties tests were conducted. The influence trend was obtained and evaluated based on the analysis of dynamic stability, relative deformation, and shear strength. For both SMA-13 and SMA-16 mixture, CR/SBS composite modified asphalt had better high temperature performances than asphalt rubber, but worse than SBS asphalt. In addition, the CR/SBS composite modified asphalt had larger internal friction angle, which could give better cohesive force for aggregate gradation. Moreover, it provided a wider range of applications for asphalt rubber mixture in road construction, which realized the waste cyclic utilization and environmental protection.

Haibin Li, Mingming Zhang, Ahmed Abdulakeem Temitope, Hongjun Jing, Guijuan Zhao, Qingwei Ma
Analysis of Low Temperature Cracking Behavior at Binder, Mastic and Asphalt Concrete Levels

In 2008, performance oriented methods for conformity testing of asphalt mixtures were introduced in the European standard series EN 13108. These standards establish primary performance properties like low temperature resistance, stiffness, resistance to fatigue and permanent deformation. However, these tests are complex and require enormous testing efforts making it difficult to implement them in routine testing. The research project VEGAS (Vereinfachte Ansprache des Gebrauchsverhaltens von Asphalt), a collaboration between 3 research institutions from Germany Austria and Switzerland, aimed therefore to simplify the testing system, but keeping the valuable information about the material performance. Testing effort was reduced to the determination of the volumetric properties and carrying out tests only on the binder and mastic using multiscale models. This paper focuses on some of the experimental efforts carried out by Empa in Switzerland, related to low temperature cracking of different types of bitumen and mastic and fatigue experiments on asphalt samples and slabs. Within this work a new testing procedure using the Double Torsion Testing method is proposed to evaluate low temperature crack propagation in mastic. Further, the testing on asphalt slabs was performed with a scaled traffic simulator and the results were used for validating laboratory scale test on cylindrical specimens. The focus of the paper is providing results and discussion of certain test methods, a comprehensive overview of the whole project is not intended.

Christiane Raab, Martin Arraigada, Hamza Ibrahimi
Analysis of Ovalization Measurements on Flexible Airfield Pavement Under HWD Dynamic Impulse Load

Non-destructive techniques (NDT) have emerged for the last decades to in-situ evaluate the pavement materials and interface conditions. These techniques turn out to be valuable tools to evaluate pavement bearing capacity, but present limitations to provide, on their own, reliable information about the interface bonding conditions. Developed in the 70’s, the ovalization test aims at evaluating the interface bonding condition between pavement layers over the cross of a rolling wheel loads. It consists in measuring the diameter variation of a cavity at different depth levels and in three horizontal directions (longitudinal, transverse and at 45° related to the loading direction). The French civil Aviation technical center (STAC) launched a research project to evaluate this device for flexible airfield pavement submitted to dynamic loadings. This paper presents some of the first multi-height tests that have been performed using the Heavy Weight Deflectometer (HWD) impulse loading at the STAC’s full-scale airfield pavement test facility constructed on the Centre d’Expérimentations Routière (CER) site at Rouen in France. The results lead to propose the design of new ovalization devices for airfield pavements.

Maissa Gharbi, Michaël Broutin, Ichem Boulkhemair, Mai Lan Nguyen, Armelle Chabot
Application of Activated Carbon on Induced Heating-Healing Characteristics of Aged Mixes

Aging phenomenon reduces the flexibility of asphalt pavements. Excessive loading and environmental conditions make asphalt mixes more prone to cracks/micro-cracks initiation and propagation. Cracks/micro-cracks in asphalt mixes can be healed through an induced healing process. Flowing and crack filling capability of asphalt binders play an important role in induced healing efficiency. This paper investigates the effects of different aging level on induced heating-healing characteristics of asphalt mixes under microwave radiation. Asphalt mixes were modified applying activated carbon to enhance its electromagnetic sensitivity. To compare heating absorption, cubic samples were fabricated at different aging levels. In addition, breaking-healing cycles through indirect tensile (IDT) test was applied to evaluate the effect of aging on induced healing process. Results revealed that microwave heating rate of asphalt mixes decreased as the aging level increased. In addition, aging has adverse effects on induced healing efficiency of asphalt mixes. The experimental testing results indicated that the devastating influence of breaking healing cycles was increased as the aging levels increased, which was more pronounced at higher aging levels.

Saeed Amani, Amir Kavussi, Mohammad M. Karimi
Application of the Synthetics Geo-Composites in the Arid Zones for Rehabilitation of the Flexible Pavements Road Experimental Analysis

The zones of the south Algerian, as the zone of Ouargla, are among the hottest zones, that are characterized by a stern and elevated temperature that can reach the 50 °C and a very big thermal gradient, without forgetting the aridity and dried it that provoke the loads and solicitations on the layer of rolling, of the pavements of the linear infrastructures (roads, aircraft pavements). What gives birth to cracks and the permanent distortions to small scale. Indeed, the downward propagation of these cracks has ominous effects on the lower layers and decrease the lift of the whole considerably especially to the presence of water, that major the damages and accelerate the deteriorations of these last. This work enters in the setting of the contribution for the understanding of these phenomena and therefore to find the adequate solutions that converge toward the safeguard of the body of pavements and the structural capacity of its infrastructures. One will proceed, on the basis of a data base to establish a state of the places that allows to lead an experimental companion to the laboratory and in situ. The integration of the composites geogrides can give satisfactory results and can increase the 1–4 times lasted it of life of the road infrastructure. The results of the dynamic tests by HWD, on road sections reinforced by geo-composites, will be the subject of analysis and reading in this analysis, in order to wedge the other found experimentally results.

Mouloud Abdessemed, Rabéa Bazzine, Said Kenai
Applying the Grid Method to Study the Mechanical Behavior at Micro Scale of Asphalt Mixtures Containing Reclaimed Asphalt Pavements

The objective of this study is to characterize the mechanical performances of reclaimed asphalt pavements (RAP), at different percentages in asphalt mixtures. Six formulations R0, R10, R20, R30, R40 and R50 of the same asphalt mixture formula, a semi-coarse asphalt concrete, with a 35/50 pen bitumen were produced in Colas scientific and technical center, in Magny-les-Hameaux, by introducing 0, 10, 20, 20, 30, 40 and 50% RAP, respectively. Indirect tensile strength tests were carried out on three of these specimens (R0, R30 and R50). Stain fields were calculated using a full field measurement method, named the Grid Method (GM) to compare the behavior of the specimens. This method consists in determining and analyzing both displacement and strain fields on the surface of the specimen. Results highlight the difference in behavior between samples both at the micro- and macro-scales.

Ali Moukahal, Mathilde Morvan, Julien Van Rompu, Evelyne Toussaint
Asphalt Aggregate Adhesion: Study of the Influence of the Morphological, Chemical and Mineralogical Properties of Different Aggregates from Southern Brazil

The proper characterization of the materials is therefore paramount for the adequate selection and use in design and execution of paving projects. One important property of the asphalt concrete is the binder-aggregate adhesion, consequence of the physical-chemical interaction between the bitumen and the aggregate surface, which keeps the elements together under traffic loads and water flow. A study was conducted to evaluate the morphological, chemical and mineralogical properties of aggregates from 12 quarries used in the production of dense asphalt mixtures in southern Brazil, as well as the interaction of the aggregates with the respective bituminous binders. The rock samples were evaluated and classified employing various methods, including Petrography, X-ray Fluorescence, Digital Image Processing (DIP) using the AIMS 2 system, traditional aggregate characterization tests, and adhesion to the bituminous binder. It was observed that acid rocks, with high Silicon content and less rough, with larger mineral size and lower AIMS values, exhibit worse performance in the visual adhesion test. The Fe/Si and Ca/K ratios were also identified as good indicators to anticipate the aggregate behavior when evaluating the adhesion to the bituminous binder. Comparative analyses based on the results from Petrography, XRF, AIMS2 and adhesion to the bituminous binder culminated in development of a scale ranking that can be used to classify the visual adhesion from terrible to excellent. Thus, it is presented as a good indicator of the behavior of the materials when evaluated the variations in the degree of adhesion allowing the correct selection of materials by the designer.

Chaveli Brondani, Cléber Faccin, Karine W. Kraemer, Fernando D. Boeira, Luciano Pivoto Specht, Andrea V. Nummer
Asphalt Layers Thickness Determination for Top Down Cracking Initiation and a Case Study

Top-down cracking (TDC) is a deterioration mechanism where cracks initiate at the pavement surface and propagate downwards with time. It is caused by horizontal tensile strains generated at the tire-pavement contact area. This paper presents a methodology for determining the thickness of the asphalt layer above which TDC will be the predominant deterioration mechanism in comparison to the bottom up cracking. The methodology covers two scenarios: one when all asphalt layers have the same stiffness modulus and the other when the asphalt layers have two different stiffness moduli. i.e. stiffness of surface layer (40 mm thick), S1, and stiffness of the rest of asphalt layers, S2. The findings concluded that in flexible and semi-flexible pavements with uniform asphalt stiffness layers, when the thickness of the asphalt layers is above a value within the range 100–210 mm (for ESAL80 axle loading), the pavement will most probably fail due to top-down cracking and not due to bottom up cracking. The exact thickness above which TDC will occur depends on the magnitude of Foundation Surface Modulus (FSM) and the asphalt stiffness. Similar range of thicknesses was found (100–230 mm) above which TDC will occur in flexible pavements with non-uniform asphalt stiffness values (S1/S2 is up to 1.13). A case study along a motorway section of 16 km long confirms the findings of the methodology developed.

A. Nikolaidis, E. Manthos
Asphalt Permeability In-service: How Can It Be Evaluated Before and After Moisture Damage?

The first bituminous road surface was purportedly placed in Paris, France, more than 150 years ago. The primary purpose of a surfacing layer was to protect the underlying pavement from moisture ingress, confirming the innate cognisance of waterproofing and low permeability to enhance pavement performance. Over the decades various methods have been implemented to evaluate asphalt permeability, including volumetric properties e.g. voids in mix, field testing e.g. using a falling head permeameter and laboratory tests on specimens or cores e.g. air or water permeability (constant or falling head). The evaluation methods each have elements of empiricism e.g. overlooking lateral versus vertical permeability or underestimating hydrostatic pressures in-service. This paper describes the development of a laboratory permeameter that evaluates vertical permeability at high pressures i.e. representative of traffic induced hydraulic pressures. The apparatus, termed “High Pressure Permeameter” HPP, is able to sustain pressures above 200 kPa. The research is based on specimens retrieved from surfacing seals and asphalt. Cores were acquired from different sources all over South Africa, including different designs and climates. Testing includes laboratory Marvil (low pressure) permeability and HPP tests at 100, 150 and 200 kPa, correlated with volumetric mix properties and CT scans. In addition, moisture damage using the Moisture Inducing Simulating Test (MIST), induces representative hydrostatic pressures over sustained periods. Findings reveal inconsistent correlation between Marvil and HPP asphalt permeability values at 100 and 150 kPa testing pressure; however, at 200 kPa higher variability is apparent. The range of mixes that have been evaluated allows for preliminary guideline limits for HPP permeability method to be developed, which can pre-empt identification of mixes with unacceptably high permeability.

C. Venter, K. J. Jenkins, C. E. Rudman, O. R. Grobbelaar
Assessing Geometric Features Impact of Laboratory Specimens on ITS Variation

The research focuses on Indirect Tensile Strength variation by changing Height and Diameter of bituminous specimens related to AC16 dense-graded binder course with limestone aggregates and neat bitumen at 4.5% following SUPERPAVE procedure. 70 specimens were prepared by using gyratory compactor by fixing hmin/D ratio equals 0.68. A total of 20 specimens whose diameter is 100 mm were prepared and the other 50 specimens were made according to a 150 mm diameter. Then, 30 of 50 specimens with a 150 mm diameter were cut in two different ways: 10 specimens were cut from the centerline and 20 specimens were cut both from the bottom and upper part to obtain a final height falling a range of 35 and 75 mm in compliance with UNIEN12697-23. Then second step refers to H0 hypothesis test as follows: could ITS values resulting from specimens prepared with 150 mm in diameter and cut by using different procedures be equal to ITS values (mean 3.47 MPa) of specimens prepared with 100 mm in diameter and different height (mean height 69.5 mm) with a significance level of 0.05? The results showed that no statistical difference exists between the 100 mm in diameter specimens and 150 mm in diameter specimens that were cut both from the upper and bottom part. However, in the other scenarios statistical differences were founded. Overall, according to the results it can be concluded that 100 mm in diameter specimens can be used for ITS evaluation of AC specimens instead of 150 mm, which consequently resulted in less materials and simplified lab-scale asphalt manufacturing procedures.

Nunzio Viscione, Francesca Russo, R. Veropalumbo, C. Oreto
Assessment of Tensile Strength Reserve of Asphalt Mixtures at Low Temperatures

During winter conditions, low-temperature cracks develop at the surface of the asphalt pavement when tensile thermal stress induced in the asphalt layer during cooling equals and exceeds the tensile strength of the material. The paper presents the results of tensile strength reserve assessment of asphalt mixtures with neat and SBS-polymer modified bitumen application. The tensile strength reserve was calculated as difference between the tensile strength βt(T) obtained from the uniaxial tension stress test (UTST) and the cryogenic (thermal) stress σcry(T) obtained from the thermal stress restrained specimen test (TSRST) at the same temperature T. It can be useful factor assessing the low-temperature properties of asphalt mixtures. It was found that the highest values of tensile strength reserve were obtained for the asphalt mixture with SBS-polymer modified bitumen.

Marek Pszczola, Cezary Szydlowski
Assessment of the Behavior of Emulsified Asphalt Mixes During Curing

To investigate the behavior of an emulsified asphalt mix during curing, the mechanical behavior and water loss of the material were studied in laboratory. The mechanical behavior of the mix was evaluated using the oedometric modulus. The dependence of the material to seasonal curing was highlighted obtaining higher stiffness values for warm conditions rather than cold ones. The influence of the water content was also observed through the temporary decrease of modulus during induced peaks of humidity. However it is concluded that the decrease of water content during curing is not sufficient by itself to account for the behavior of emulsified asphalt mixes since they continue to evolve even after full drying.

Amélie Thiriet, Vincent Gaudefroy, Jean-Michel Piau, Frédéric Delfosse, Emmanuel Chailleux, Christine Leroy
Characterization of Aluminosilicate-Based Warm-Mix Asphalt Additive Using Experimental Techniques

In this study, an aluminosilicate-based water containing warm-mix asphalt (WMA) additive was developed using: sodium aluminate, tetraethyl ammonium hydroxide (TEAOH), montmorillonite (MMT K10), and water referred to as STEAM. Further, the STEAM additive and raw MMT K10 material were characterized using experimental techniques that included particle size analyzer (PSA), zeta potential, scanning electron microscopy coupled with energy dispersive X-ray analysis (SEM-EDX), thermogravimetric analysis combined with differential scanning calorimeter (TGA-DSC), and powder X-ray diffraction (XRD). The PSA and zeta potential results confirmed the exchange of sodium (Na+) ions and adsorption of water molecules (H2O) in the chambers of crystal structure. SEM images revealed STEAM particles to be larger and layered with fibrous look. The XRD images of MMT K10 and STEAM additive synthesized using one-step hydrothermal reaction showed similar high peaks at 2θ of 26.58°, and 12.24, 24.79°, which correspond to quartz and Kaolin, respectively, indicating no alteration in the crystal structure. The thermal analysis of STEAM additive confirmed the presence of water molecules (both physically and structurally bonded) with the loss in mass of about 10.52% between the temperature range of 80–260 °C similar to the mass loss in the commercially available standard zeolite A (SZA). Thus, the newly synthesized STEAM belongs to the group of synthetic zeolites. The approach taken in this study would help reduce the viscosity of asphalt binder during asphalt mixture production at lower temperatures making it suitable as a WMA technology.

Rituraj Patel, Vinay Hosahally Nanjegowda, Jagadeesh Mahimaluru, Krishna Prapoorna Biligiri
Characterization of Layer Index in Bituminous Pavement Using Mechanistic-Empirical Approach Based on Concentration Factor in a Layered System

The deflection bowl data from FWD has been extensively used to back-calculate the layer modulus of pavement structure. In this context, detailed analysis of shape of deflection bowl has been made in this paper to evaluate the extent of damage and distress of respective layers. Transformation of multilayer system has been made in this paper to determine deflection of pavement at different layer interface by using the concept of concentration factor based on modular ratio. The deflection bowl parameters like Base Layer Index (BLI), Middle Layer Index (MLI), and Lower Layer Index (LLI) have been determined using the proposed analytical approach and comparative analysis has been made with other relevant field investigation.

S. Purakayastha, P. P. Biswas, M. K. Sahis, G. C. Mondal
Characterization of Rejuvenated Asphalt Binders Using FTIR and AFM Techniques

This study investigates the chemical and morphological behavior of rejuvenated asphalt binders. A TFOT aged PG 58-28 binder was mixed with three different types of rejuvenators that include waste cooking oil/untreated used cooking oil (UT), treated used oil (TR), and Hydrolene (HL) at 3, 6, and 9% by the weight of the total binder. To understand the characteristics and the performance of these rejuvenators, three sets of characterization tests were conducted: rheological, chemical, and morphological. This paper presents a summary of the results from our chemical and morphological studies. Gas Chromatography-Mass Spectroscopy (GC-MS) was conducted to identify the chemical composition of rejuvenators, while Fourier Transformed Infrared Spectroscopy (FTIR) was conducted for obtaining chemical functional group information. Furthermore, an Atomic Force Microscopy (AFM) was employed to obtain the micro-morphological properties of rejuvenated asphalt binders. The collected data showed that rejuvenation changes the chemical composition and alters the micro-structures of binders significantly, which impacts the overall performances of binder. In fact, this experimental study showed a good correlation between chemical compositional and morphological features with the rheological performance of the binder. The research findings are expected to contribute to the performance evaluation and characterization of rejuvenated asphalt mixes.

Rayhan Bin Ahmed, Kamal Hossain
Characterization of the Lateritic Soil of Kamboinsé (Burkina Faso)

Laterite is a very common material in tropical countries. Good quality lateritic deposits are becoming increasingly rare. This material is used as a base course for most roads built in tropical Africa. These materials are selected on the basis of geotechnical test results in accordance with current standards. However, these materials do not perform well in situ after a short period of time, causing premature pavement degradation. This poor behavior can be ascribed to insufficient geotechnical testing to justify the choice of these materials in road construction. In this work, in addition to traditional geotechnical tests (particle size analysis, Atterberg limits, modified Proctor, CBR Index), compression tests were performed in addition to traditional geotechnical tests to determine compressive strength and elasticity modulus. Geotechnical tests carried out on the laterite of Kamboinsé according to the lithology of the quarry reveal that the characteristics decrease with depth and that the first layer can be used as a base layer. Cement improvement for small percentages (1, 2 and 3%) shows a clear improvement in mechanical characteristics. An addition of 2% cement allows the use of the second base layer, improvement of 3% allows the use of the first layer as a base layer. An addition of granite crushed granites of class 0/31.5 improved the physical properties of materials for additive percentages varying from 20, 25, 30 and 35% by weight of dry materials. This improvement allows the use of layers 1, 2 and 3 as a base layer for low traffic, layer 4 can be used as a base layer.

Marie Thérèse Marame Mbengue, Adamah Messan, Abdou Lawane, Anne Pantet
Circular Accelerated Surfacing Tester (CAST) for Evaluating Chip Sealing Binders

Development of a laboratory scale device for testing chip seal road surfacing performance at realistic loading rates and under controlled temperatures is described. A variety of sealing binders have been tested, and the forces applied to the seal quantified. The damage produced in the seal surface by the CAST (Circular Accelerated Surfacing Tester) machine was quantified by a stereo-photographic method which captured damage arising from chip loss, displacement and reorientation. As part of a study into a performance related bitumen specification for chip seal binders, the CAST machine was used to verify seal performance against the viscosity at 45 °C. A correlation was found between viscosity and seal performance at 45 °C. The results are presented here to illustrate the operation of the CAST machine.

Lia C. van den Kerkhof, Jeremy P. Wu, Shaun R. Cook, Philip R. Herrington
Coefficient of Thermal Expansion and Thermally Induced Internal Cracking of Asphalt Mixes

The coefficient of thermal expansion/contraction (CTE) is an important factor influencing the low temperature thermal cracking of asphalt pavements. The typical CTE of asphalt mixture decreases as the temperature drops, showing a sigmoidal form of gradual transition. The objectives of this study were to determine the effects of CTEs of asphalt binder and aggregate on the mixture CTE, to determine the effects of the mixture CTE on the low temperature performance of the asphalt mixture, and to investigate the transition behavior of the mixture CTE at low temperatures. Two limestone aggregates and four asphalt binders with different CTE values were used to prepare eight asphalt mixture combinations. The mixture CTE values were determined using a custom-made CTE device where the thermally induced deformations were measured in two diametral directions. The low temperature performance was determined using the Asphalt Concrete Cracking Device (ACCD), a concentric thermal stress restrained specimen test. Based on the test results, it was concluded that the measured asphalt mixture CTE values were significantly smaller than the values predicted by the current AASHTOWare Pavement ME model. The cracking temperature measured by ACCD became colder as the mixture CTE became smaller. The transition of the mixture CTE appeared to be caused by internal cracking and could be modeled with the isochronal stiffness of asphalt binder. The mixture CTE transition temperature was highly correlated with the ACCD cracking temperature.

Sang Soo Kim, Moses Akentuna, Munir Nazzal
Combined Recycling of RAS and RAP: Experimental and Modeling Approach

The use of Reclaimed Asphalt Pavement (RAP) and Recycled Asphalt Shingles (RAS) in combination with new materials in asphalt mixes appears to be a good solution to achieve economic and environmental benefits while maintaining or increasing the performances. The main objective of this work is to verify the application of the two blending laws for the prediction of conventional, physicochemical and rheological parameters at the binder scale. After extraction and recovery operations of RAP and RAS binders, the recovered binders were mixed with a virgin bitumen (PG 58-34) in several recycled bitumen ratios (RBR) up to 40% wt. The blends were characterized by conventional (penetration and Ring and Ball softening point), rheological (shear complex modulus) and physicochemical (Infrared spectroscopy (FTIR), Differential Scanning Calorimetry (DSC)) tests to compare the rheological behavior, the oxidation levels and the glass transition temperature. The 2S2P1D model was used to fit experimental shear complex modulus data. The proposed models describe well the experimental data from conventional, rheological and physicochemical tests.

Abdeldjalil Daoudi, Anne Dony, Alan Carter, Layella Ziyani, Daniel Perraton
Combined Use of Natural Rubber, Biomass and Plastic Wastes in Bitumen Modification and Flexible Pavement Construction

A novel bitumen modification process has been developed using lower grade natural rubber-ribbed smoked sheet (NR-RSS) and soda lignin (SL) isolated from waste green coconut fiber. At first, natural rubber along with rubber additives was mixed in toluene and then soda lignin was added. Obtained mixture was characterized by rotational viscometer, Fourier transform infrared spectrometer, universal testing machine, simultaneous thermal analyzer, etc. The mixture was then blended with 60–70 penetration grade bitumen (B). Physical, spectral, microscopic and thermal properties of modified bitumen (MB) were evaluated. It was shown that the prepared natural rubber-lignin mixture significantly improved the physical properties of bitumen as required for flexible pavement construction in tropical countries. Marshal stability was improved by 25% in comparison to 60–70 penetration grade bitumen. Based on the result obtained, an experimental pavement was constructed using modified bitumen and waste polyethylene-coated aggregates (Pav-MB-PCA). For comparison, another pavement of similar size was constructed with 60–70 penetration grade bitumen and non-coated aggregates (Pav-B-NCA). More than two years observation showed better performances of the pavement made with modified bitumen and waste polyethylene coated aggregates. All findings have been discussed in detail.

Swapan Kumer Ray, Riyadh Hossen Bhuiyan, Muhammad Saiful Islam, Md. Jaynal Abedin, Zahidul Islam, Rashed Hasan
Comparative Evaluation of Different Methods for Assessing the Glass Transition Temperature of Bituminous Binders

Glass transition is a second order transition that takes place within a relatively narrow temperature range in amorphous or semi-crystalline materials as they become glassy and brittle. The glass transition temperature (Tg) is the temperature selected to represent this transition and is an important indicator of the low temperature properties of materials. In the case of bituminous binders, no standard protocol is currently available for the determination of Tg, so various techniques have been proposed by researchers. The objective of the work presented in this paper is to compare different methods for the determination of Tg of bituminous binders. A set of selected materials was evaluated by means of a dynamic shear rheometer by imposing various test conditions. Different criteria involving both rheological and volumetric parameters were used to analyze experimental data. Obtained results showed a strong dependency of Tg on the adopted testing parameters and criteria.

Ezio Santagata, Chiara Tozzi, Orazio Baglieri, Davide Dalmazzo
Comparative Study of the Mechanical Behaviour of Bitumen- and Cement-Dominated Mixtures with Reclaimed Asphalt

The bitumen emulsion-based recycling is a commonly used maintenance treatment in the rehabilitation of low-and medium-volume roads in Europe. Nevertheless, the wide range of climatic conditions across the continent resulted in the variety of mixture concepts and the requirements being adopted for various local conditions. In this regard, the most commonly used parameter to distinguish between the main mixture concepts is bitumen to cement ratio. This article presents the comparison of the results of mechanical properties for different approachest to design of cold recycled mixtures with either bitumen or cement having the dominant role in the mechanical behaviour. In both cases, bitumen emulsion C60B5 and Portland cement CEM I were used as binding agents, and the considered cold recycled mixtures were designed to contain at least 70 % of reclaimed asphalt. The combinations of binding agents were selected based on the respective requirements. Mechanical properties were expressed by the indirect tensile strength, failure strain, and stiffness modulus, while the tests were conducted at the temperatures of 5 and 20 °C and the curing periods of 7 and 28 days. The comparison showed that the mixtures with the higher content of cement reached much higher stiffness and, from the aspect of the kinetics of mechanical properties development, they almost resembled cementitious materials. In contrast to this, the behaviour of bitumen-dominated mixtures, especially at earlier curing stages, was within the common requirements but also tended to have much higher strains at failure.

Miomir Miljković, Bohdan Dołżycki, Mariusz Jaczewski, Cezary Szydłowski
Comparing Compressive and Flexural Dynamic Asphalt Modulus by Statistical and Neural Network Modelling

Asphalt modulus is the key material characteristic for asphalt layers in layered elastic pavement thickness design. The value of modulus selected by the designer has significant influence on the critical strains calculated in the pavement and consequently the predict life of the structure. Traditionally, a typical modulus value was used for all mixtures and all design scenarios within a given jurisdiction. Importantly, the modulus value used for thickness design is intended to be representative of the asphalt mixture, but because of the impact of vehicle speed and temperature, the actual asphalt modulus changes in the field. This paper compares compressive and flexural modulus values and trends for a range of a typical Australian airport asphalt mixture. In addition, statistical and neural network modelling were used to develop equations for predicting the compressive and flexural moduli of asphalt. The implication of the typical difference in values is estimated and further work is recommended.

Ali Jamshidi, Greg White
Comparing Laboratory Curing and In-Pavement Curing of a Foamed Bitumen Stabilized Base Course Material
ISBM Lyon 2020

Foamed bitumen stabilization is well-established as a beneficial technology for the improvement of existing pavement materials and for expedient pavement construction or rehabilitation. Laboratory curing indicative of in-pavement conditions is crucial to effective foamed bitumen stabilized material characterization for pavement design, with significant project and pavement lifecycle cost implications resulting from laboratory mix design that does not represent actual pavement behavior. This research compares Australian foamed bitumen base laboratory curing practice to a simulated in-pavement condition and concludes that the accelerated laboratory curing was more representative of 20–30 days of in-pavement curing, rather than the intended medium (3–6 month) term curing condition. It is recommended that new laboratory curing protocols be developed to better represent typical in-pavement curing conditions.

Thomas Weir, Greg White
Comparing Wet Mixed and Dry Mixed Binder Modification with Recycled Waste Plastic

Recycled plastic is now recognised as a potential bituminous binder extender and modifier, with various studies demonstrating the potential to improve asphalt mixture properties, including resistance to cracking and resistance to deformation. Many waste plastic products are intended to be dry-mixed into the asphalt production plant, but wet mixing into the bituminous binder is also possible. Laboratory tests for fracture resistance, moisture damage resistance and deformation resistance were used to compare otherwise identical wet-mixed and dry-mixed recycled plastic modified asphalt, as well as comparison to nominally identical control (unmodified) asphalt. The binder was also extracted from tested specimens and compared using common index properties, including elastic recovery, softening point and penetration. The effect of recycled plastic on the asphalt mixture properties and the binder properties was a generally significant improvement in deformation resistance, with no reduction in fracture resistance. Importantly, the wet-mixed and dry-mixed results were generally not significantly different, indicating that the two mixing processes are equally effective. Further research should focus on the practical issues of distribution and digestion of recycled plastic through the asphalt mixture during dry-mixing, as well as digestion and storage stability of wet-mixing into bituminous binder.

Greg White, Finn Hall
Comparison Between Rheological Behavior of a Neat Asphalt Binder and a Bio-Binder from Renewable Source

Binders produced from biomass are turning on an attractive alternative to construct sustainable roadways, replacing partially, or even totally, the asphalt binder content—petroleum-based—of the asphalt mixtures. This paper presents a comparison between a neat asphalt binder and a wood-based bio-binder in terms of their rheological behavior at different aging stages. For both binders, the dynamic shear modulus, │G*│ and the phase angle, δ, at different frequencies and temperatures was determined using the Dynamic Shear Rheometer (DSR). The permanent deformation susceptibility and the fatigue behavior were also investigated through the Multiple Stress Creep and Recovery (MSCR) test and the Linear Amplitude Sweep (LAS) test, respectively. Results showed that the bio-binder used in this study has higher dynamic shear modulus than the asphalt binder studied, which is also observed in the MSCR results, where the bio-binder presented a better resistance to permanent deformation when compared to the asphalt binder. Regarding to fatigue, LAS results suggest that the neat asphalt binder has a better response when compared with the bio-binder. Besides, a Performance Grade classification was carried out for both binders, however, it was not possible to determine the lowest temperature for the bio-binder, as the results observed for this material did not meet the established limits by the method. One reason for that could be that these limits, and the method itself, were specified for asphalt binder and might not be suitable for other types of binders (not petroleum based). As a conclusion, the wood-based bio-binder displayed characteristics that could be used in the construction of roadways, but it is necessary to develop characterization methods that allow its proper classification.

Leidy V. Espinosa, Fernanda Gadler, Rafael V. Mota, Kamilla L. Vasconcelos, Liedi L. B. Bernucci
Comparison of Alternate Binder Aging Methods

In the Superpave™ binder specification system, long-term aging of bituminous binders is simulated by treatment for 20 h in a pressure aging vessel (PAV). In some North American jurisdictions, 20 h PAV aging has been supplemented with 40 h PAV as it has been suggested that more severe laboratory aging is necessary to screen some of the current blended binders. As extending already lengthy laboratory aging impacts refinery and terminal logistics, in this work, several alternate aging methods to shorten test time while providing equivalent extent of aging to 40 h PAV were evaluated. For this study two PG 64-22 binders (one straight-run, and one softened with a bio-oil) were aged through multiple cycles of the rolling thin-film oven test, 20 h PAV at three temperatures, or 40 h PAV. The properties of the aged binders were compared and initial results indicate that 20 h PAV aging at 110–120 °C mimics 40 h PAV aging at 100 °C, but that changing temperature can change the relative ranking of binders.

John A. Noël, M. Rezwan Quddus, Payman Pirzadeh, Pavel Kriz, Ralph Shirts
Comparison of Different DSR Protocols to Characterise Asphalt Binders

The use of Dynamic Shear Rheometer (DSR) has become a standard tool to characterise bituminous binders, either for research or specifications purposes. Testing with the DSR enables to cover a wide range of temperature and frequency conditions in a fast way by using limited amount of materials. Depending of the test type, DSR measurements provide different rheological parameters to characterise physically the materials either at low, intermediate or high temperatures. At the same time, different test protocols have emerged. While the preferred mode is running in frequency sweep at different temperatures, the test can also be run with a temperature ramping at a fixed frequency. In order to evaluate the validity of the DSR testing mode, four different test protocols were run, including a frequency sweep test at different temperatures and temperature ramping at a fixed frequency with different temperature rates. This experiment was applied to three different bituminous binders, two non-modified binders, soft and hard, and a standard Polymer modified Bitumen (PmB). The analysis was conducted on shear modulus and phase angle versus Temperature. The outcomes showed a reasonably good correlation between the different protocols in the common range of temperatures and demonstrated instrument limitations regarding geometry and control parameters.

Laurent Porot, Johannes Büchner, Michael Steineder, Sjaak Damen, Bernhard Hofko, Michael P. Wistuba
Comparison of the Effects of Hydrated Lime on the Moisture-Induced Damage of Stone Mastic Asphalt (SMA) Mixtures

Moisture-induced damage is one of the most prominent distresses affecting pavement structures worldwide. As a consequence, various strategies for mitigating this phenomenon have been proposed, including the use of additives to improve bitumen-aggregate bonding, engineered to mitigate/counteract the moisture damage effects. Among these, the reported benefits of various lime forms, such as hydrated lime (HL), have propelled its use (mainly in the United States from the early 70s) as widely reported in scientific literature. However, very few studies have been conducted in the United Kingdom with locally available materials, specifications and testing methods suitable for that purpose. Therefore, this study investigates the effects of HL on the moisture damage resistance of stone mastic asphalt (SMA) mixtures designed, produced and tested under local UK conditions. A set of asphalt slabs with a target 4.0% air voids content and two bitumen contents (5.6 and 6.2%) using granite aggregates were manufactured using a roller ‘slab’ compactor consisting of control mixtures (0% HL) and those with 1, 2 and 3% HL by weight of total mixture. Characterisation of the mixtures was done via the saturated ageing tensile stiffness (SATS) test to account for both the effects of ageing and moisture damage. The SATS test results showed a positive effect of the addition of HL on the moisture damage resistance, however increasing HL contents only produced marginal additional improvements. The influence of the reduction in bitumen content was negligible. Furthermore, the results indicated an optimum dosage of 1% HL for enhanced moisture damage resistance.

Amar Badal, Juan S. Carvajal-Munoz, Gordon Airey
Comprehensive Model for the Prediction of the Phase Angle Master Curve of Asphalt Concrete Mixes

Viscoelastic analysis of asphalt concrete pavements requires information on dynamic modulus, |E*|, and phase angle, ϕ. While several efforts have been directed at developing predictive models for |E*|, predictive models for phase angle ϕ have received much less attention. This paper presents a comprehensive predictive model for phase angle master curve based on the Lorentzian equation. The model was estimated using 6742 observations of 262 specimens from three different data sets, two from Hawaii and the other from Costa Rica, containing variables in common such as frequency, temperature, air voids, binder content, binder type, and gradation and variables about mix characteristics and testing conditions not available in some data sets, such as confinement level, number of freeze-thaw cycles (as a surrogate of moisture susceptibility), antistripping agents, and fibers. The predictive equation incorporates the effects of these variables on the three parameters of the Lorentzian function as well as on the parameters of the temperature shift factor function. The model parameters were estimated using joint estimation to identify the effects of variables with variations in only some datasets but simultaneously considering variables common to all data sets, and mixed effects to account for unobserved heterogeneity between specimens. All the previous factors were found to be statistically significant and to affect one or more of the parameters of the Lorentzian function. The paper shows that the model provides an excellent fit to the data and discusses briefly the effects of some variables.

Adrián Ricardo Archilla, José Pablo Corrales-Azofeifa, José P. Aguiar-Moya
Crack Evolution of Bitumen Under Torsional Shear Fatigue Loads

This study aims to model crack evolution in bitumen under a torsional shear fatigue load by dynamic shear rheometer (DSR). Fatigue crack length in the bitumen was predicted using a damage mechanics-based DSR cracking (DSR-C) model. The crack evolution is modelled using a pseudo J-integral based Paris’ law. Frequency weep tests and time sweep fatigue tests were conducted on an unmodified bitumen 40/60 and a polymer-modified bitumen X-70 at different temperatures, frequencies and loading amplitudes. Results demonstrate that the pseudo J-integral Paris’ law can accurately predict the crack evolution in the bitumen under the torsional shear fatigue load. A stiffer bitumen due to decreasing temperature has a smaller Paris’ law coefficient A and a greater exponent n, which proves that the fatigue crack grows faster at a lower temperature. The Paris’ law coefficients A and n are temperature-dependent fundamental material properties, which are independent of loading frequency or loading amplitude.

Yangming Gao, Linglin Li, Yuqing Zhang
Crack Self-healing in Asphalt as a Flow Process

Asphalt has the ability to restore diminished properties caused by damage. This ability is known as self-healing and in case of asphalt it is conferred upon by the competent bitumen. Bitumen is a viscoelastic liquid and has self-healing abilities due to is viscous part. Hence, the healing of cracks in asphalt is mainly influenced by rheological properties of bitumen. The viscosity of bitumen, which affects the self-healing rate, is affected by the filler content. In this research, the effect of porous aggregates in asphalt and the filler content in asphalt mortar is investigated. The absorption of bitumen by porous aggregates further reduced the self-healing efficiency beside the drainage of bitumen occurring at higher temperatures. This effect is reduced by increasing the bitumen content. However, the porous aggregates reduced the mechanical resistance of the asphalt beams, resulting in a lower breaking force. The contribution of flow to the self-healing was determined by material drainage into an artificial gap during the healing process on asphalt mortar beams. The material flowing into the gap had a similar composition as the mixture, though it had an increased filler and bitumen content. The filler content had no effect on the maximum healing efficiency or the breaking force, though influence the flow speed. The flowing material also consists of smaller aggregate particles, indicating the fundamental relationship between mixture design and self-healing.

Daniel Grossegger, Alvaro Garcia, Gordon Airey
Cracked Asphalt Pavement Behaviour Under Thermal and Load Cycles – Laboratory Investigation Using Accelerated Loading System

Although the mechanism of thermal cracking and the factors affecting the occurrence of this type of cracks are already well documented, the influence of this phenomenon on the structural capacity and the freezing behavior of the roadway near the cracks, as well as the consequence for the pavement of these localized effects is still poorly documented. The objective of the project is to improve the state of knowledge on the effects of cracking on pavement performance and to develop effective approaches for the mitigation of this degradation. Therefore, a pavement structure was built in the experimental pit of Laval University. The structure is composed of a reference section and a section in which an idealized crack has been created. These two sections are dynamically loaded using the Accelerated Transportation Loading System (ATLAS). Mechanical response of the pavement structure has been monitored via various strain and stress sensors, with particular interest for the area around the crack. A quantitative comparison of the two sections shows how the presence of a crack affects the different strain and stress levels measured around the idealized crack area. Results also show the pavement structure’s behavior under different temperature and saturation conditions.

Youness Berraha, Daniel Perraton, Guy Doré, Michel Vaillancourt
Cracking Healing Evaluation of HMA Using Indirect Tensile Stiffness Modulus Test

Crack healing is characterised by the recovery of stiffness in asphalt concrete after a period of rest. Micro damage occurs in asphalt pavement layers when there is continuous reduction in its stiffness modulus, which causes the formation of micro-cracks. This paper presents an evaluation into the healing potential of coarse and fine dense-graded asphalt mixes. The binders investigated were Modified Bitumen (MB) and two types of Trinidad Lake Asphalt (TLA) having penetration values of 60/70, 60/75 and 40/55 respectively. Evaluation of asphalt healing through the Indirect Tensile Stiffness Modulus (ITSM) were done, before cracking, after cracking and after healing periods of 1, 4 and 8 hrs at healing temperatures of 35 °C and 60 °C. Greater healing was exhibited in TLA-60/75 fine graded mixes at the lower temperature of 35 °C, while greater healing was seen in the MB-60/70 fine grade mixes at 60 °C, however, for the TLA coarse mixes greater healing was observed at 60 °C. TLA-60/75 specimens showed increased healing for greater rest periods while MB-60/70 and TLA-40/55 mixes varied with rest periods. The reduction of micro-damage in a pavement, greatly defers the propagation of macro cracks, extends serviceability, reduces maintenance costs and increases the sustainability of the pavement.

Lee P. Leon
Creep Properties of Asphalt Binder, Asphalt Mastic and Asphalt Mixture

For designing asphalt materials resistant to permanent deformation and rutting, a low creep deformation at high temperature is the crucial performance property. Usually, creep deformation is assessed through static or cyclic compression tests at elevated temperature, both for asphalt mixtures as well as for asphalt binders. For asphalt mixtures, static and cyclic compression tests are specified in the European Technical Standards. For asphalt binders, creep tests are usually performed by means of a Dynamic Shear Rheometer (DSR), such as Multiple Stress Creep and Recovery Test (MSCRT) developed for Polymer-modified asphalt binders. However, different author questioned the control parameters and significance of the MSCRT, especially for plain asphalt binders. In this paper, creep properties of asphalt binders and asphalt mastics (binder-filler-mixtures) are tested in the DSR using increased loading and recovery times to ensure steady-state flow conditions. These tests are performed on a set of 10 different asphalt binders and 18 corresponding asphalt mastics. The same material combinations are used in asphalt mixtures produced in the laboratory and then subjected to a cyclic compression test to assess the creep properties of the asphalt mixture. Finally, the creep properties resulting from asphalt binder tests, asphalt mastic tests, and asphalt mixture tests are correlated. The results show reasonable correlations over the different scales. It is concluded, that the asphalt binder has a significant impact on the creep behavior of the corresponding asphalt mixture.

Johannes Büchner, Michael P. Wistuba, Thilo Hilmer
Critical Reclaimed Asphalts Binders’ Properties from Empirical and Functional Point of View

Due to ageing processes bituminous binders undergo significant changes in terms of viscoelastic behavior. Generally, binders become harder, stiffer, more brittle and more elastic. Such materials are then, as a part of reclaimed asphalt (RA), reused during the production of new asphalt mixtures (in an ideal case). The presence of RA, however, can in turn negatively influence the properties of the final mixture. More often than not aged bituminous binder properties are tested in terms of empirical properties, e.g. softening point or needle penetration. However, the functional properties or critical parameters are normally overlooked especially in Europe. Therefore, the article’s aim is to describe the behavior of various reclaimed binders via functional approach. The characterization of extracted binders was carried out by using dynamic shear rheometer as well as bending beam rheometer. Critical low and intermediate parameters were evaluated. The results indicated that the behavior of reclaimed binders is quite variable. Moreover, it was found out that the needle penetration test might overestimate the degree of aging which can potentially lead to excluding some materials from recycling purposes.

Tomas Koudelka, Ondrej Dasek, Michal Varaus
Degree of Binder Activity on 100% Recycled Mixtures and Its Linear Viscoelasticity Behavior

To increase the content of Reclaimed Asphalt Pavement (RAP) in new recycled mixes, it is necessary to have a better understanding of the activation phenomena of the Reclaimed Asphalt binder, so it can better interact with the recycling agent in Recycled Asphalt Mixtures (RAM). Studies have reported temperature as an important influencing factor related to the RAP binder activity. This paper analyzed the influence of three mixing and compaction temperatures: 100, 140 and 170 °C, in the Degree of Binder Activity (DoA) of two different RAPs. One of them has neat asphalt binder (penetration 50–70) on its composition, and the other one has Polymer Modified Binder (PMB) (60/85, softening point/elastic recovery limits, respectively). To this comparison, artificial RAP mixes with similar characteristics to those of the original RAP (including the same conditions such as binder, grading curves, aggregate types and binder content) were produced in the laboratory. The DoA was estimated using the ratio between the indirect tensile strength result from 100% RAM and artificial RAM, for the same temperature. The type of RAP and the temperature influenced in DoA, since the first RAP presented short ratios, 8.9, 32.0 and 10.2% for 100 , 140 and 170 °C respectively, and the second RAP, presented 54,4 88,2 and 95.8% ratios for respective temperatures. The 100% RAP mixtures were furthermore evaluated with respect to their complex modulus; the rheological model 2S2P1D was used and it was possible to relate DoA to the linear viscoelastic behavior of the analyzed mixes.

Pablo Menezes Vestena, Pedro Orlando Borges de Almeida Junior, Luciano Pivoto Specht, Débora Tanise Bordin, Helena Leitão Pinheiro, Kamilla L. Vasconcelos, Gustavo Menegusso Pires
Determination of Epoxy Resin Concentration in Epoxy Modified Bitumens

Recently open graded mixes using epoxy modified bitumen have begun to be used in New Zealand for general road surfacing applications. To reduce cost and potential risk to plant and machinery, commercially available epoxy bitumen is commonly diluted with standard grade bitumen. To ensure that the specified concentration of epoxy resin is being used and detect possible quality control problems in plant operation, some means of measuring the resulting epoxy resin concentration is desirable. This work describes two test methods based on Fourier Transform Infrared Spectroscopy (FTIR) and elemental oxygen content measured by Fast Neutron Activation Analysis (FNAA), that have been developed for this purpose.

Lia C. van den Kerkhof, David Alabaster, Philip R. Herrington
Determination of Thermal Stresses in Asphalt Layers as a Problem of Thermo-elasticity and Unsteady Heat Flow

The paper presents solutions for thermo-elasticity problems with an unsteady heat flow for various layered systems typical for Polish traffic categories KR4 and KR7. The tasks were solved assuming a plain strain case for material parameters, which in most cases were determined in a laboratory tests, under thermal type of loading, which simulates an extremely unfavorable weather condition. For the selected structural variants, the resulting stress state was analyzed in relation to the determined tensile stress limits for individual mixture materials. In half analyzed cases, exceeding the material tensile strength in second layer (L2) was observed only as a result of the decreasing temperature.

Marcin Gajewski, Wojciech Bańkowski, Beata Gajewska
Determining the Prominence of Texture Scales on Road Skid Resistance

The work described in this paper contributes to the physical separation and systematic identification of the role of the small and large scales on skid resistance. A new signal processing technique termed Empirical Mode Decomposition (EMD) and a skid resistance model named Dynamic Friction Model (DFM) are synergized to evaluate the effects of the small and large road surface texture wavelengths on skid resistance data measured using current technologies (Dynamic Friction Tester (DFT) and Circular Track Meter (CTM)). The influences of the different wavelengths are investigated by first; applying the EMD to separate and synthesize the intrinsic texture scales to gradually and smoothly decompose the original surface textures, and second; to utilize the DFM with the synthesized texture profiles to analyze and discover their relative effects on measured friction. The obtained results show that for two road surfaces (in controlled wet conditions) with the same nominal large-scale texture range, the higher the small-scale texture is, the better the skid resistance will be at low speed. Furthermore, for two wet road surfaces with the same small-scale texture, the higher the large-scale texture is, the better the skid resistance is with increasing speed. In summary, on wet road surfaces, the small-scale texture is key to achieving good skid resistance at low speeds and large-scale texture is crucial to maintaining it when the speed increases.

Malal Kane
Development of Permanent Deformation Models with the Inclusion of AIMS Coarse Aggregate Angularity

Permanent deformation is a critical failure mechanism and a serviceability performance indicator in flexible pavement that can be influenced by the potential of coarse aggregate stone-to-stone interlocking properties. Interlocking is dependent on coarse aggregate angularity and this has an effect on rut susceptibility of mixtures. Although research into the effects of angularity on mixes has been ongoing for over six decades, this study aimed to investigate and develop a permanent deformation model that includes the description and effects due to changes in coarse aggregate angularity. The aim was accomplished by conducting laboratory aggregate test using Aggregate Imaging System (AIMS) and Repeated Load Axial Test (RLAT) of four mixes (rounded, sub-rounded, sub-angular, angular) designed and classified with different combinations of AIMS coarse aggregate angularity index (CAI). The results revealed that there is a correlation between coarse aggregate angularity and laboratory-measured axial permanent deformation strains. Most empirical deformation prediction models do not account for the direct inclusion of an angularity parameter. The study explores the use of multiple non-linear regression (MNLR) and gene expression programming (GEP) as unconventional approaches to predict, simulate and evaluate the effects of particle angularity on permanent deformation behaviour of asphalt concrete (AC). The soft computing approach had satisfactory outcomes of the estimation of permanent deformation (R2 = 0.957) with an inclusion of an angularity parameter over that of the regression estimations (R2 = 0.891). Observations concluded that with some improvements the laboratory model could be used to predict and rank mixes base on the permanent deformation behaviour.

Lee P. Leon
Discrete Modelling of 2PB Complex Modulus Test of Hot Asphalt Mixes Using Irregular Aggregates

Asphalt mixtures are complex multiphase materials showing a viscoelastic behavior. In order to assess the mechanical response under traffic of these materials, a typical practice is to perform a complex modulus test. An alternative to laboratory characterization is to simulate numerically the complex modulus test by means a discrete approach. Classical discrete approaches are able to reproduce the mechanical performances of asphalt mixtures, but show some difficulties to model non-spherical particles. In this work, the complex modulus test is reproduced numerically for an asphalt mixture by 3D simulations carried out with the LMGC90 code. A viscoelastic contact law is used to handle the interaction between particles with irregular shapes. The numerical aggregates were generated using the particle size distribution (PSD), the flakiness index (FI), and statistic data of actual aggregates, without using complex imaging technics. Experimental and numerical testing campaigns were conducted for the complex modulus test on trapezoidal samples in a two-point bending (2PB) configuration. The numerical model was able to reproduce the mechanical performances obtained during the experimental tests, regarding the viscoelastic properties of the material. The influence on the mechanical performances of particle shape considering irregular aggregate was analyzed. The proposed model can be used to simulate the mechanical response of road structure under traffic loading concerning rutting, crack propagation and fatigue damage.

Juan Carlos Quezada, Cyrille Chazallon
Effect of Ageing Kinetics on the Rheological Properties of Bituminous Binders and Mixes: Experimental Study and Multi-scale Modeling

The oxidative ageing of hot mix asphalt (HMA) and foamed warm mix asphalt (WMA), performed through laboratory accelerated ageing processes is investigated in this study. 50/70 pen-grade bitumen was used to produce the mixes. Four ageing durations (0, 3, 6 and 9 days) were considered to investigate the kinetics of long-term ageing based on a RILEM ageing procedure. The binders of the aged mixes were extracted and characterized. Moreover, RTFOT and PAV tests were carried out on fresh bitumen to simulate the long-term ageing of HMA. These procedures were adapted to simulate the long-term ageing of WMA for which no standardized ageing procedure exist. Rheological tests were performed to determine the stiffness modulus of binders and mixes. The results show that the stiffness modulus increases with the ageing kinetic for both binders and mixes. This increase is more pronounced for WMA and their binders than HMA. Furthermore, the equivalence between the RTFOT and RTFOT + PAV ageing procedures performed on bitumen and the RILEM procedure carried out on loose mixes was discussed for both HMA and WMA. Finally, a multi-scale model was implemented to predict stiffness moduli and phase angles of the mixes based on bitumens’ and aggregates’ properties. The results show a relatively good agreement between the multi-scale model and the experimental data curve-fitted with the well-known modified Huet-Sayegh model.

C. Somé, J.-F. Barthélémy, V. Mouillet, Ferhat Hammoum
Effect of Fiberglass Geogrid Reinforcement to Fatigue Resistance of Bituminous Mixtures

This work aims at verifying the fiberglass geogrid contribution to the fatigue resistance of bituminous mixtures. To conduct the research, two different configurations of slabs were fabricated. The first one was composed of two mixtures layers glued by emulsion. The second one was identical to the first one but reinforced by fiberglass geogrid in the interface. This geogrid was fabricated at Afitexinov and has 100 kN/m of maximum resistance. Tests were performed on cylindrical samples horizontally cored into slabs. Interfaces were thus vertical. Cyclic tension/compression tests in controlled strain mode were carried out. Seven samples from each type of specimen were tested at frequency of 10 Hz and temperature of 10 °C. Four strain amplitudes were targeted: 80, 90, 100 and 110 μm/m. An increase in fatigue resistance was observed for high strain levels, for sample with the geogrid reinforcement. However, obtained ε6, parameter from Wohler curves, which is used in the French design method, were similar for both specimens configuration.

Reuber Freire, Hervé Di Benedetto, Cédric Sauzéat, Simon Pouget, Didier Lesueur
Effect of Filler Type and Content on the Rheological Properties of Asphalt Mastics

This study investigated the influence of various fillers on the rheology and performance of asphalt mastics. Mastics were prepared by mixing a PG70-XX binder with two waste fillers (limestone sludge waste, glass powder) and conventional stone dust filler in three different proportions. Firstly, physical and chemical properties of fillers were determined and then asphalt concrete mixes were designed. Based on their optimum bitumen contents, the filler bitumen ratios were determined and mastics were prepared. The multiple stress creep and recovery (MSCR) test and linear amplitude sweep (LAS) analyses were performed to analyze the behavior of asphalt mastics against rutting and fatigue. In general, the use of waste fillers improved the rheological behavior of mastics in comparison to conventional stone dust mastic. The stiffness of all mastics increased with the filler bitumen ratio. The glass powder mastic displayed superior stiffness at all temperatures and exhibited higher elastic recovery and lower creep compliance.

Jayvant Choudhary, Brind Kumar, Ankit Gupta
Effect of RAP and Binder Properties on Indirect Tensile Strength and Dynamic Modulus of Cold Recycled Foamed Asphalt Mixtures with High RAP Content

Cold recycling with foamed asphalt is a sustainable pavement rehabilitation technology and becomes more widely applied in many countries. However, there are still some ongoing scientific debates on the issues such as cold recycling mix design, pavement structural design and analysis. Many popular mix design methods adopted indirect tensile strength (ITS) as the most important design criterion. Dynamic modulus (|E*|) representing the viscoelastic behavior which has been found in the cold recycled foamed asphalt mixtures also become a helpful parameter for accurate pavement structural analysis. For cold recycled foamed asphalt mixtures with only reclaimed asphalt pavement (RAP), RAP and virgin binder used for producing foamed asphalt may govern the performance test results. The objective of this study was to determine the effects of RAP and virgin binder properties on the ITS and |E*| of the recycled mixtures. Three RAP materials (i.e., fine, medium, coarse) and two virgin binders (i.e., PG 58-34 and PG 67-22) were selected to produce six recycled mixtures. The effects of RAP properties (i.e., gradation, fineness modulus, F-E ratio) and virgin binder performance grade (PG) on the two performance test results were evaluated. The ITS results of the mixtures with finer RAP or higher PG virgin binder tended to be higher. The |E*| result was remarkably affected by RAP gradation at most of the testing frequencies and temperatures. Mixtures with the same RAP material but different virgin binder can achieve similar |E*| results.

Wangyu Ma, Di Wang, Fan Gu, Adam Taylor, Randy West
Effect of RAP Gradation on Fracture Tolerance of Asphalt Mixtures

This study investigated the effect of RAP gradation on the fracture tolerance of asphalt mixtures in terms of fracture energy density (FED). Experimental factors included two RAP sources, one virgin binder and four RAP contents of 0, 20, 30 and 40%, resulting in a total of seven mixtures. Binder fracture energy tests were conducted to determine the FED of blends of virgin and extracted RAP binders. Moreover, interstitial component direct tension (ICDT) tests were employed to measure the FED of the interstitial component, which is the fine portion of a mixture that governs cracking performance. Finally, Superpave IDT tests were performed to obtain the FED of RAP mixtures. Increasing RAP content led to reductions in FED at binder, IC and mixture levels. More importantly, the reduction in FED was almost identical for mixtures and IC, whereas a less pronounced drop was observed for binders. This finding substantiates that full blending between RAP and virgin asphalt as artificially created in binder specimens did not occur in the actual RAP mixtures. Coarse RAP yielded greater IC and mixture FED values than fine RAP despite the lower RAP binder stiffness of the latter, substantiating that RAP gradation controls the distribution of RAP binder in mixtures and consequently, high RAP binder content in IC portion reduces the fracture tolerance of a mixture. A new design guideline that considers RAP binder content and properties along with RAP gradation is proposed to determine the maximum allowable RAP content, so that cost savings and environmental benefits can be maximized by reducing the need for virgin pavement materials and landfill space.

Yu Yan, David Hernando, Bongsuk Park, Gabriele Tebaldi, Reynaldo Roque
Effect of Soybean Oil Derived Additives on Improved Performance of Polymer-Modified Asphalt Binder and Mix Containing 50% Fine-Graded RAP

Recent work has shown that epoxidized plant oil materials work well as rejuvenators in recycled asphalt pavement (RAP) and as enhancers of polymer modification of neat binders. Earlier work using a small-angle x-ray scattering (SAXS) device (Xenoncs Xuess 2.0 UHR) with asphaltenes modified and unmodified with a rejuvenator called epoxidized methyl soyate (EMS) showed a decrease in asphaltene particle size by up to 20% when the rejuvenator was used at a dosage of 2.75% by total weight of the binder for modification. In addition, past work also showed epoxidized plant oil materials when used with sulfur eliminated phase separation of SBS polymers from the asphalt matrix and promoted improved elastic recovery. For this work a series of experiments were undertaken in rheology, and mix performance with a interlayer mix design containing 50% RAP to better understand why epoxidized plant oil materials have these effects. Two epoxidized plant oil materials and a commercial rejuvenator derived from corn oil were used for comparison purposes. In this work it was shown that the two epoxidized plant oil materials made significant improvements to beam fatigue and low temperature mix performance as well as low temperature binder performance. However, only one of them sub epoxidized soybean oil (SESO) did not degrade the elastic recovery of the base polymer modified binder as shown through multiple stress creep recovery (MSCR) testing of the rejuvenated binders.

Joseph Podolsky, Austin Hohmann, Conglin Chen, Zahra Sotoodeh-Nia, Nicholas Manke, Barrie Saw, Nacu Hernandez, Paul Ledtje, Michael Forrester, R. Christopher Williams, Eric Cochran, Theodore Huisman
Effect of Temperature on Self-healing Properties of Bituminous Binders

Healing properties of bituminous binders are commonly evaluated by subjecting test specimens to oscillatory shear loading with inclusion of single or multiple rest periods. In almost all protocols adopted by researchers, during both loading and rest phases the same constant temperature is imposed to the specimen. However, it is widely recognized that temperature may have a great impact on healing mechanisms taking place in the binder. In order to address this issue, this paper investigates the healing properties of bituminous binders by means of a test procedure which consists of two time sweep tests conducted at the same temperature and by an intermediate rest period whose temperature is set at different values. Response of the material is quantitively assessed by introducing two healing indicators based on stiffness and strength recovery, respectively. Discussion of the experimental results presented in this paper underlines the relevance of temperature which needs to be taken into account to correctly rank bituminous binders in terms of their self-healing potential.

Ezio Santagata, Fabrizio Miglietta, Orazio Baglieri, Lucia Tsantilis
Effect of Thermal Ageing on the Mechanical Properties and Cracking Behaviour of Asphalt Concrete

This article assesses the impact of ageing on the properties of asphalt concrete (AC) by combining experiments and numerical simulations. Rheological tests were performed at four thermal ageing durations (0, 3, 6 and 9 days). The results show an increase in the complex modulus and a decrease in phase angle with ageing time. For each ageing time, semi-circular bending tests were carried out under two loading rates (1 and 5 mm/min) and three temperatures ( $$-20$$ - 20 , 0 and 20 $${}^{\circ }$$ ∘ C). The results shown an increase of the peak load when the loading rate increases for each thermal ageing time and temperature. No meaningful variation of the peak load with respect to the ageing time was observed at low temperatures. However, it was found that at $$20\,{}^{\circ }$$ 20 ∘ C, the peak load increases with ageing duration. A finite element modelling was implemented, coupling viscoelastic behaviour and crack growth criterion. The results show a similarity between numerical and experimental results.

B. Kouevidjin, J.-F. Barthélémy, C. Somé, H. Ben Dhia, A. Feeser
Effects of Adding a Geotextile into a Pavement Structure on FWD Experimental Data and Estimated Pavement Remaining Service Life

Impregnated geotextiles are commonly used in road construction or rehabilitation to minimize water infiltration into the pavement structure. However, the effects of such waterproofing membranes on the mechanical behavior of the pavement structure are difficult to predict. In this paper, Falling Weight Deflectometer (FWD) measurements were used to highlight differences between pavement structures with and without geotextile. The FWD measurements were performed on two recently rehabilitated roadways where a bitumen impregnated non-woven geotextile was placed between the surface layer and the base layer for some sections. The FWD measurements were performed on both sections rehabilitated with and without the geotextile and the deflection basins were compared. The surface curvature index (SCI), the base damage index (BDI) and the base curvature index (BCI) were also compared. The measurements were then used to predict the remaining service life (RSL) of the pavement structures. The results of this study suggest that traditional approaches used to interpret FWD measurements are not suitable when a bitumen impregnated geotextile is present between two asphalt layers.

Jean-Claude Carret, Alan Carter
Effects of Aggregate Shape Parameters and Gradation on High-Modulus Asphalt Mix Performance

Studying the performance of an asphalt concrete mix generally focuses on parameters such as the volumetrics of an asphalt mix, asphalt binder type, and content. However, the aggregate source and morphology can also significantly contribute to the performance of asphalt mixes. This paper investigates the influence of aggregate shape parameters (roundness, concavity, shape factor, and elongation) and gradation on the performance of low air-void high-modulus asphalt mix or Enrobé à Module Élevé (EME). Two high modulus mixes based on nominal maximum aggregate sizes of 12.5 and 19 mm were developed using two sources of mineral aggregates. The shape parameters of aggregate fractions were determined using an aggregate image analyzer. Thermo-mechanical tests were performed to evaluate performance of the developed mixes. The compactability of EME mixes was assessed using the Superpave Gyratory Compactor (SGC). The rheological properties of the mixes were evaluated by conducting complex modulus test at a range of temperatures (−10 to 54 °C) and loading frequencies (0.1–25 Hz). Furthermore, Hamburg wheel tracking and four-point bending beam fatigue tests were conducted to assess the rutting and fatigue performance of EME mixes, respectively. The aggregate image results indicated a considerable difference in roundness and concavity parameters of the aggregates. It was also concluded that the difference varies by changing the aggregate source and size. In addition, the performance test results showed that changes in the aggregate shape parameters along with the gradation can affect the performance of the mixes.

Taher Baghaee Moghaddam, Hassan Baaj
Effects of Binder Content, Filler Content, Air Void and Modification on Damage Characteristics of Asphalt Mix Under Fatigue Loading

Evaluating the behavior of asphalt mixtures under repetitive loading is essential to understand the fatigue performance of flexible pavements over the service life. Fatigue loads cause damage in asphalt mixture medium, which results in the reduction of the mix stiffness. In this study, 21 types of asphalt mixes with different aggregate sources, asphalt binder contents, filler contents, air void levels, modifiers, and aging levels were evaluated for damage evolution due to repetitive loading. All mixtures were tested in unaged and long-term aged conditions. The dynamic modulus and the cyclic fatigue (Push-Pull) tests were performed on each mix to obtain mix stiffness, fatigue life, and the damage characteristics (C-S curves). The preliminary statistical analysis of the test results revealed that the shape of the damage function, modulus of the mix, and slope of relaxation are highly affected by the aging, asphalt binder content, and mix modification.

Hamidreza Sahebzamani, Mohammad Zia Alavi, Orang Farzaneh, Serge Krafft
Effects of Chemical and Microstructural Constituents on the Healing Characteristics of Asphalt Binders

Self-healing of asphalt binders and mixtures during rest periods of cyclic loads is a topic that has been studied more carefully recently. To better understand the effects of the chemical characteristics on the healing behavior, this paper characterizes the chemical composition of binders based on the following tests: chemical fractionation (SARA), gel permeation chromatography (GPC), nuclear magnetic resonance (NMR), and chemical elemental analysis. In addition, the microstructural composition of the binders is also evaluated based on testing results obtained in an atomic force microscope (AFM). In such tests, the area fractions of the three main binder microstructural components, i.e., catanaphase, periphase, and paraphase, are determined. The chemical and microstructural compositional results are then compared to linear amplitude sweep (LAS) test results obtained with and without rest periods for the eight asphalt binders investigated. These comparisons indicate that the overall self-healing characteristics of the binders are related to their microscopic characteristics and this understanding may be useful for the selection and even for the fabrication of materials that are more resistant to fatigue.

Leni F. M. Leite, Francisco T. S. Aragão, Thaísa F. Macedo, Patrícia H. Osmari, Margareth C. C. Cravo, Luis A. H. Nascimento, Luciana N. Dantas
Effects of Water Saturation and Freeze-Thaw Cycles on Fatigue Behavior of Bituminous Mixtures

The effects of water saturation and freeze-thaw (FT) cycles on fatigue behavior of the bituminous mixtures were studied in this research. Three different types of specimen conditioning were applied. Cyclic tension-compression tests on cylindrical specimens were performed. Sinusoidal loading in controlled axial strain mode was applied at 10 Hz at 10 °C. Fatigue test results are analyzed by using three different fatigue life criteria. The resistance to fatigue is then analyzed by using the Wöhler curves. Water saturation and FT conditioning do not significantly affect the fatigue performance of the tested material.

Duc Thang Tran, Cédric Sauzéat, Hervé Di Benedetto, Bertrand Pouteau
Efficiency of Ultrasonic Pulse Velocity Test in the Determination of Residual Asphalt Mix Pavement Properties

This paper presents the result of an experimental study based on propagation wave velocities measurements with P and S-waves performed on a laboratory asphalt mix plate. Three methods for the Time Of Flight (TOF) determination are proposed, taking into account the Signal-to-Noise Ratio (SNR) influence. The shift from the wave velocities to mechanical properties is made within the framework of a linear, isotropic and elastic material and by using the gamma rays test results. The data is presented in form of cartographies. Furthermore, a statistical analysis was conducted from the cartographies in order to determine the nominal values and confidence interval.

S. Benaboud, M. Takarli, F. Allou, F. Dubois, A. Nicolaï, Bertrand Pouteau, A. Beghin
Elasto-Plastic Model for Bitumen Stabilized Materials Using Triaxial Testing and Finite Element Modelling

Cold recycling with BSMs is becoming a very common technique, nevertheless there are minimal constitutive models available that can fully characterize their mechanical response in pavement systems. The aim of this research project was to identify the intrinsic material properties through a finite element simulation of triaxial tests performed in laboratory for BSMs with different mix designs. The main differences between the mechanical behaviors of BSM with respect to foam bitumen content (1.5% and 3%) are determined. All mixes discussed herein contained same active filler amount of 1.5% Portland cement. The triaxial tests were performed on cylindrical specimens at different confining pressures (0, 100, 200 kPa) in a displacement control configuration (3 mm/min). The triaxial tests at the different confining pressures were simulated using a 3D finite element model to determine plasticity parameters. The input values for an elasto-plastic model (Young’s modulus, Poisson’s ratio, cohesion, friction angle and dilatation angle) have been calibrated to match experiment results with simulations, mainly in terms of strain and stress levels corresponding to onset of plastic deformation. The parameters obtained by these simulations are very useful to predict the rutting behavior of bituminous stabilized materials in a multilayer pavement structure. This study provides an insight on how bitumen content affects constitutive BSMs properties.

Francesco Preti, Beatriz Chagas Silva Gouveia, Elena Romeo, Gabriele Tebaldi, Eshan V. Dave, Jo E. Sias
Empirical, Rheological and Chemical Properties of Aged Binder with Rejuvenators at Different Ageing Levels

The use of Reclaimed Asphalt (RA) into new asphalt mixtures becomes an inevitable step for sustainable infrastructure. Saving natural, non-renewable materials, such as bitumen and aggregates, the asphalt industry is moving forward with more recycling. Although asphalt is a 100% reusable material, high recycling rates are not yet easily achievable due to many limitations, going from technical specifications through RA properties to asphalt plant capabilities. The rate of RA, which may be used within a new asphalt mixture, depends on many aspects: variability, moisture and fines contents, presence of polymers, brittleness of aged binder, etc. The latter is directly linked to the degree of the RA binder ageing. As higher RA content increases the asphalt mixture stiffness, the material becomes more brittle and prone to cracking. The use of recycling additives is taking recycling to the next level by solving these issues. With the growing need of the industry for asphalt recycling agents, many products have appeared on the market with different effects. In this study, three asphalt recycling agents (two industrial and one alternative) were used as rejuvenators. Blends with 50% of rejuvenated RA binder (RAb) and virgin binder were subjected to different ageing levels: short (RTFOT), long (PAV for 20 h) and prolonged (PAV for 60 h). After each ageing level, physical, rheological and chemical properties were evaluated addressing the ageing behaviour of the additives used. Testing results showed that one industrial additive lost almost all its properties after prolonged ageing, whereas the other additives showed comparable results with the second industrial product.

Marko Orešković, Laurent Porot, Stefan Trifunović, Goran Mladenović
Enhanced Models for Vehicle Fuel Consumption for Life Cycle Assessment of Pavements

A life cycle assessment (LCA) of pavements provides a comprehensive approach to evaluate the potential environmental impacts associated with all stages of a pavement’s life: material production, pavement design, construction, use phase, maintenance/preservation, and end of life. The use phase stage is influenced by the pavement’s structural and material properties as well as its surface characteristics. Pavement surface characteristics such as roughness can influence the vehicle operating costs (VOCs). This paper presents specific examples of the newly developed FHWA fuel economy models using full vehicle dynamic simulations while taking into consideration vehicle speed profiles, roadway properties (e.g., grade, curvature, roughness), and vehicle types. Physics-based full vehicle simulation models were implemented to estimate vehicle fuel economy over a range of synthetically optimized (SO) driving cycles. The SO driving cycles were determined based on a collected sample of Strategic Highway Research Program 2 (SHRP 2) Naturalistic Driving Study (NDS) and American Transportation Research Institute (ATRI) time series data. Thirty different vehicle types were considered and comprised six different vehicle categories: small light duty vehicles (SLDVs), large light duty vehicles (LLDVs), two-axle trucks, busses, single-unit truck, and combination trucks. Different engine types were also considered such as gasoline, diesel, hybrid-electric, ethanol (E85), and liquefied natural gas (LNG). Reduction in fuel economy due to roadway curvature (RFEC) prediction models along with pavement condition adjustment factors (PCAFs) for a range of pavement roughness conditions in terms of International Roughness Index (IRI) were also developed for the various modeled vehicles.

Rami Chkaiban, Elie Y. Hajj, Gary Bailey, Muluneh Sime, Hao Xu, Seyed-Farzan Kazemi, Peter E. Sebaaly
Enhanced Self-healing Properties in Stone Mastic Asphalt with Encapsulated Bitumen Rejuvenators

The extensive use of asphalt is generating a special interest in increasing the durability of this material. The development of encapsulated bitumen rejuvenators for self-healing asphalt is a sustainable and automated alternative to prolong the lifespan of asphalt. This paper presents an experimental study about how the strength and size of the encapsulated bitumen rejuvenators affect the mechanical properties of the material. In addition to that, this paper shows how optimum sizes and strengths of encapsulated bitumen rejuvenators are found to maximize the healing properties without compromising the fatigue resistance. Three types of asphalts containing encapsulated bitumen rejuvenator with different sizes and strengths were manufactured for this study. Each type of capsule was mixed in stone mastic asphalt to analyze their influence on fatigue durability and self-healing properties. The encapsulated rejuvenators performance was assessed by carrying out wheel tracking tests in the laboratory. Different loads were applied over the asphalt samples with and without capsules. The results showed that encapsulated bitumen rejuvenators, besides improving the healing properties of the material, are able to maintain and improve, depending on the type of capsule, the asphalt fatigue resistance.

Nilo Ruiz-Riancho, Tahseen Saadoon, Alvaro Garcia, Robin Hudson-Griffiths
Establishing Correlations Between Force Ductility and DSR Parameters of Asphalt Emulsion Residues

DSR based rheological tests of 5 non-polymer modified and 5 polymer modified asphalt emulsion residues were performed and its relationships with force ductility parameters (AASHTO T300) were investigated. Some results are presented in this paper. One of the observations from temperature sweep test is that as temperature increases, phase angle of an emulsion residue increases, reaches a maximum and then decreases. Polymer modified asphalt emulsions have comparatively lower phase angle than non-polymer modified asphalt emulsions and the maximum phase angle of all the polymer modified asphalt emulsion residues falls below 81° whereas the maximum phase angle of all the non-polymer modified emulsion falls above 87°. MSCR at 58 °C, 70 °C and equal stiffness (2.2 kPa) temperature clearly demonstrates that percent recovery of polymer modified residues are significantly higher than non-polymer modified emulsion residues. In case of 58 °C and 0.1 kPa creep stress, maximum average percent recovery is 7.7 for non-polymer modified asphalt emulsions while the minimum average percent recovery is 29.7 for polymer modified emulsions. Three force ductility parameters namely, f2 (force at 30 cm), f2/f1 and force at 35 cm were correlated with two DSR-based parameters, phase angle and percent recovery at different temperatures. Based on the analyses of linear coefficient of determination values, it is recommended that phase angle and percent recovery of MSCR be used for polymer identification and to replace force ductility requirements (AASHTO T300) for asphalt emulsions. At 58°C, a maximum phase angle of 81° and a minimum MSCR percent recovery of 30 (at 0.1 kPa creep stress) are recommended.

Nazimuddin M. Wasiuddin, Mohammad Islam
Estimation of Complex Shear Modulus of Binder Blends Produced with RAP Binder and Rejuvenator

The linear viscoelastic behavior of various blends of a fresh binder (a straight-run 50/70 penetration grade binder) and a RAP-extracted binder, with and without rejuvenator (a mixture of vegetal oils), was studied. The experimental plan includes a total of 9 binders: fresh binder, RAP binder, 3 blends of RAP binder and rejuvenator and 4 blends of fresh and RAP binders with and without rejuvenator. The rejuvenator content used for blends was 0%, 5%, 10% and 15% by mass of RAP binder within the blends. Complex shear modulus of all blends was obtained by means of Dynamic Shear Rheometer (DSR) tests at temperatures ranging from 25 to 85 °C and for frequencies ranging from 0.1 to 10 Hz. Two different approaches were proposed in order to estimate the norm of complex shear modulus of different binder blends from experimental results obtained for the base constituents. Good correlations with experimental data were observed.

A. Forton, Salvatore Mangiafico, Cédric Sauzéat, Hervé Di Benedetto, Paul Marc
Estimation of Fatigue Damage in Bituminous Mixes Using Digital Image Processing

Fatigue cracking, a major type of failure in bituminous mixes, is caused by the accumulation of damage due to the repeated application of traffic loads. To understand this phenomenon clearly, it is necessary to quantify material damage in terms of an appropriate parameter. Crack length is typically used as a measure of damage. This study explores the suitability of crack area as a damage parameter and examines the crack area growth patterns of two different bituminous mixes prepared using VG40 and PMB40 binders. Indirect tensile fatigue test (ITFT) was conducted on the specimens of mixes at three different stress levels and two different test temperatures, 25 and 35 °C, to characterize their fatigue behavior. Digital image processing (DIP) approach was used to estimate the progression of the crack area with the number of load repetitions. It is observed that the crack area grows exponentially with the number of load repetitions. The crack area growth models developed in this study indicate that the rate of damage accumulation is affected by the characteristics of mix components. These models can be used to calculate the consumed fatigue life based on the crack area measurement. Results also show that the crack area growth rate is higher at a higher temperature and the crack area in mixes with unmodified binder increases at a faster rate than in mixes with modified binder.

Shubham Modi, Tejaswini Lakshmi Tavva, Priyadarshini Saha Chowdhury, Sudhakar Reddy Kusam
Estimation of Glassy Modulus and Differences Between Analysis Methods with Consideration of Aging

As a binder is aged in laboratory procedures such as Rolling Thin Film Oven (RTFOT) and Pressure Aging Vessel (PAV) the stiffness characteristics change. In a series of studies, an extended PAV condition of 40 h, standard PAV, RTFOT and Orginal conditions have been tested with binders used in Africa, Asia and the USA including those graded by Penetration, Viscosity and Performance Graded (PG) specifications. In all conditions of aging Bending Beam Rheometer (BBR) tests have been conducted to carefully define the low temperature rheology whereas isotherms of stiffness collected with a Dynamic Shear Rheometer (DSR) has been used to define the intermediate and high stiffness properties. The parameters calculated from the BBR data include the glassy modulus and the shape parameters of the master curve including the delta Tc. The BBR data is combined, via an interconversion process, with the DSR and the complete master curve is obtained. Various parameters have been determined such as the R-value (rheological index), glassy modulus, Glover-Rowe parameter and the cross over modulus. The changes observed in Glassy Modulus also correlates to the R-value which supports the view that this characteristic changes with aging. Glassy Modulus has been calculated using six different methods and is compared to other methods developed over the past 50-years. In all cases the value determined relies upon some extrapolation. This suggests that the oxidation products effect the value of glassy modulus as well as the overall shape of the master curve. The choice of analysis method will affect other binder parameters that are dependent of the Glassy Modulus and the consequence of this is discussed.

Geoffrey M. Rowe
Evaluate the Impact of the Reclaimed Asphalt Pavement (RAP) Binder Activation on its Shape Properties

The degree of binder activation of reclaimed asphalt pavement (RAP) is one of the main points that affects the design of the recycled asphalt mixture (RAM). Most previous works concentrate effort analyzing the degree of binder activity (DoA) from the asphalt binder point of view. However, there is lack of existing information about the impact of the DoA on the aggregate’s properties. Assuming DoA less than 100%, which is the most used assumption on the literature, means that part of the RAP binder will be inactive, so it is unclear which RAP aggregate properties, such as gradation and shape, should be used to design the RAM. In this context, the main objective of this work is to understand the impact of the DoA on the RAP’s aggregates properties. Stages of binder extraction were performed in two RAPs in order to simulate different DoAs. After each stage of binder extraction, the RAPs were analyzed using digital image processing (DIP). The results indicate that RAPs with the same gradation present distinct size distribution after each stage of extraction mainly due to the clusters present on the RAP. RAP angularity is affected by the DoA, especially for coarse aggregates. Thus, the DoA affects not only the binder available to be blending with the virgin binder but it also can affect the aggregate mineral skeleton of the RAM.

Wellington L. G. Ferreira, Verônica T. F. Castelo Branco, Kamilla L. Vasconcelos, Amit Bhasin
Evaluating the Cracking Performance of Asphalt Mixes Using Four-point Beam Fatigue and Semicircular Beam Testing

This paper studies the relationship between fracture resistance and fatigue performance of conventional asphalt mixtures, asphalt mixtures with reclaimed asphalt pavement (RAP), and rubberized asphalt mixtures. The four-point beam (4PB) test has been widely used to assess the fatigue performance of asphalt pavements; however, long testing time and difficulty of specimen preparation are the major drawbacks of this test which limit it from being applied as a routine mix design and quality control/quality assurance (QC/QA) method. The semi-circular beam (SCB) test has been developed to serve as a simple and fast surrogate test for QC/QA or even mix design method of asphalt pavement for routine projects. SCB measures the fracture resistance of asphalt mixes at intermediate temperatures. In this study, fracture parameters, including fracture energy, flexibility index, stiffness, fracture toughness, and strength were obtained from the SCB test. The correlation between fracture parameters from the SCB test and the fatigue behavior as measured by the 4PB test has been explored. The simple linear regression results indicated that the stiffness and fracture toughness from the SCB test have good correlations with the initial stiffness from 4PB tests. It was also shown that the fracture toughness from the SCB test correlates moderately well with the strain at 1-million fatigue cycles normalized by the stiffness, both from the 4PB test.

Liya Jiao, John T. Harvey, Mohamed Elkashef, Rongzong Wu, David Jones
Evaluation of Aging Processes in Binders Stabilised from Cationic Bituminous Emulsion

The application of cold mix recycling technology in the construction of road subbase layers by using bitumen stabilised materials (BSMs) is a cost-effective and sustainable solution, as it allows to substitute raw material with a significant amount of recycled materials: both RAP and construction demolition waste (CDW). The use of recycled materials in road construction should not negatively affect the durability of a pavement structure. Consequently, further reduction of aging processes is necessary. The objective of this study was to evaluate the aging processes of binders stabilised from cationic bituminous emulsions by comparing their basic and rheological properties with those of binders derived from laboratory aging simulation (RTFO). RTFO tests simulating short-time aging were applied to original bitumen binders used in the process of bituminous emulsion production both modified and unmodified. Evaluation of the results of the research was carried out on the basis of aging indexes and rheological properties of the binders in a wide temperature range. The research has shown that the technological processes of bitumen emulsion production cause the reduction of the aging processes of the bitumen binder compared to the RTFO test which simulated the hot process. Therefore, the use of BSMs based on the cationic bitumen emulsion not only preserves the environment due to the protection of natural resources, but also leads to a measurable decrease in the aging process in contrast to hot mix asphalt (HMA) production.

Wojciech Sorociak, Katarzyna Konieczna, Jan B. Król, Dawid Żymełka, Karol J. Kowalski
Evaluation of Cracking Performance Indices from Disk-Shaped Compact Tension Testing

Performance-engineered mix designs and performance-based specifications for asphalt mixtures rely on not only establishing performance properties but relevance and representation of field performance of asphalt mixtures. This paper presents a comparative evaluation of various performance indices from fracture tests with respect to asphalt mix properties and field reflective cracking performance of asphalt overlays. Fracture energy (Gf) is currently the primary index used when evaluating the disk-shaped compact tension (DCT) test results. However, Gf does not directly take into consideration the behavior of the post peak region of the load-displacement curve, which may indicate the mixture’s ability to resist crack propagation and provide insight into fracture processes (e.g., crack growth velocity). It is possible to have two DCT specimens with similar Gf values but significantly different load-displacement responses. This study evaluates Gf in addition to three other indices that consider the full load-displacement behavior: fracture strain tolerance (FST), rate-dependent cracking index (RDCI) and a newly proposed DCTIndex. A total of 5 asphalt mixtures and corresponding reflective cracking performance of these mixtures from 4 full-scale pavement test sections (asphalt overlay on Portland cement concrete) are used to compare field performance and equivalent Gf, FST, RDCI and DCTIndex values for the various overlay sections. Results from this study provide insight into the applicability of the various indices from DCT testing in performance-engineered mix design approaches.

Katie E. Haslett, Eshan V. Dave, Jo E. Sias
Evaluation of Engineered Crumb Rubber (ECR) Performance Characteristics, Including Warm-Mix Equivalence with Polymer, Draindown Prevention, and Release Enhancement

Ground-tire rubber (GTR) has been shown to enhance asphalt mixture performance, much like polymer modification, but with the added advantage of utilizing a recycled material source as the modifier. Recent rubber-modifiers being used in the asphalt industry have been modified, for instance, by adding chemically-engineered coatings, with the intent of improving one or more mixture performance characteristics. In this study, a finely-ground, chemically-modified, dry-process Engineered Crumb Rubber, or ECR mix was evaluated and compared to polymer-modified mixture, with an added variable of Warm Mix Additive (WMA). First, the mixtures are compared in terms of various mixture performance tests. Second, the effect of ECR modification on draindown of a mix is investigated. Finally, the study evaluates the effect of ECR modification of workability and compact-ability of the asphalt mixture via a thorough volumetric study, supported by the inferred stiffness of the mixtures from the Superpave Gyratory Compactor (SGC) data. The results show an overall superior performance by ECR mixtures in comparison to polymer-modified mixtures. Further, ECR modification is shown to have similar effects as WMA additive for the mixture type investigated, eliminating the need to use WMA additive. Additionally, ECR modification is shown to mitigate draindown in the gap-graded mixture investigated, eliminating the use of cellulose fibers. Finally, ECR modification showed similar or improved mixture compact-ability, and workability.

Punyaslok Rath, J. Meister, B. Jahangiri, H. Majidifard, W. Buttlar
Evaluation of Epoxy Asphalt Binders for Open-Graded Friction Course (OGFC) Application

Epoxy asphalt (EA) binder is an asphaltic material modified with thermosetting polymer. Compared to binders containing thermoplastic elastomers, EA binder has better thermal stability, rigidity, and resistance to deformation. The real breakthrough of EA binder is its superior resistance to aging and embrittlement, which are two major contributors to raveling of open-graded friction course (OGFC) mixtures. Therefore, EA has a potential to improve durability of OGFC mixtures and extend their service lives. Despite advantages, EA binder has limitations, most notably its high cost compared to styrene-butadiene-styrene (SBS) modified and rubberized asphalt binders. A cost-effective solution to reduce material expense is to dilute EA with unmodified asphalt binders, which in turn reduces the epoxy dosage rate in the resultant binder. The objective of the study was to evaluate curing behavior and rheological properties of EA binders produced with epoxy resins from two sources, based on their performance grade, multiple stress creep recovery, linear amplitude sweep, and Glover-Rowe parameter results. The following conclusions were made: Curing rate of EA binder is highly dependent on epoxy dosage rate and temperature; Superpave test methods are not suitable to EA binder with epoxy dosage rate of 40% due to the thermosetting polymer nature of epoxy resin; Diluted EA binders showed improvement in resistance to rutting, fatigue, and aging in comparison to neat binder but did not outperform SBS-modified binder; An epoxy dosage rate above 8% is needed for diluted EA binders to have comparable or better performance than SBS-modified binder.

Raquel Moraes, Fan Yin
Evaluation of Fracture Resistance of SMA Mixtures with Various Percentages of TLA-RAP Through the Semi-circular Bend (SCB) Test

Flexible pavements during their life experience different distresses such as deformation and cracking. To minimize the damages more durable mixes such as Stone Matrix Asphalt (SMA) were developed. However, this came with additional construction cost which influenced the growing trend of having economical, sustainable and durable pavements. Aggregates manufactured from Recycled Asphalt Pavement (RAP) are considered to be a suitable sustainable aggregate to blend in new asphalt mixes. The study aimed to evaluate the fracture behaviour of SMA surface mixes designed with various percentages of Trinidad Lake Asphalt (TLA) recycled aggregate contents (10–50%) using the semi-circular bend (SCB) under different notched depths and temperature. The effects of notched depths and temperatures on the ultimate fracture strength and fracture energy were analysed. The results indicate that the notch depth has no significant effects on the fracture toughness and the fracture energy, but the RAP content has relatively obvious effects on the fracture energy, which shows that the optimum RAP ranges are between 30 and 35%. The temperature (5–25 °C) has significant effects on the ultimate loads, fracture energy, and fracture toughness. The results showed that SMA mix with optimized RAP had better resistance to fracture behaviour when compared to conventional SMA mix.

Lee P. Leon, Karla Bovell
Evaluation of Laboratory and Field Performance of Cold In-Place Recycling (CIR) Asphalt Mixtures

The objective of this research study is to evaluate both laboratory and field performance of Cold In-Place Recycling (CIR) asphalt mixtures in terms of rutting and cracking resistance. A balanced CIR mixture prepared with foamed asphalt at 2.5% foaming water was selected to construct three full-scale CIR sections at Rowan University’s Accelerated Pavement Testing Facility (RUAPTF): (1) a rut-resistant section (i.e., containing 2% binder content), (2) a crack-resistant section (i.e., containing 4% binder content), and (3) a performance-based section (i.e., containing 3% binder content). Once cured, one inch Hot Mix Asphalt (HMA) was placed on top of the CIR Layer. An accelerated pavement testing (APT) was then performed on each section using Dynatest Mark IV Heavy Vehicle Simulator (HVS) to apply repeated truck tire loading magnitudes for 150,000 passes. Pavement mechanistic responses were recorded by asphalt strain gauges, pressure cells, and thermocouples embedded at the bottom of each CIR layer. Rutting and cracking performance of each section was assessed and compared to the laboratory performance of foamed asphalt CIR mixtures compacted with 30 gyrations and subjected to a three-day curing at 10 °C. The results showed that the rut-resistant section presented lower rutting susceptibility, while all three section showed a similar cracking resistance under accelerated truck loading.

Ahmed Saidi, Ayman Ali, Yusuf Mehta, Ben C. Cox, Wade Lein
Evaluation of Long Term Performance of High Modulus Bituminous Mixes

Recent studies on flexible pavements signify that it may be advantageous to use High Modulus Bituminous Mixes (HiMB) in bituminous base layer to enhance the life of pavement. HiMB mixes are produced with hard grade bitumen and designed at lower air voids to incorporate high bitumen content. Hard grade bitumen is usually produced in refineries by propane-de asphalting (PDA) method or air blowing technique. An alternative method of producing HiMB mixes is by using Reclaimed Asphalt Pavement (RAP) material as it consists of aged bitumen which is stiff in nature. Bituminous mix was prepared with viscosity grade (VG) 40 bitumen is blended with 33% RAP to target the HiMB mix prepared using PDA pitch that results in equivalent resilient modulus (Mr) and fatigue life. It is important to understand effect of addition of aged bitumen on long term performance of the mix. The present study focuses on the evaluation of laboratory long term aged properties of HiMB mixes produced by both PDA pitch and VG 40 blended with 33% RAP using Dense Bituminous Macadam (DBM-II) aggregate gradation. HiMB mixes were subjected to long term aging and evaluated for mechanical properties and performance. The results of Indirect Tensile Strength, resilient modulus and fatigue performance reveal that the mix prepared using PDA pitch is more susceptible to brittle failure in long term aged condition.

B. Anil Kumar, Ashish Kesharwani, Arun Kumar Goli, M. Amaranatha Reddy, K. Sudhakar Reddy
Evaluation of Pavement Damage Through the Analysis of Asphalt Layer Modulus and Strain Evolutions During an Accelerated Pavement Test

Accelerated Pavement Tests (APT) have been proved as a reliable methodology to evaluate pavement performance within a short period. However, the evolution of damage of such full-scale pavements, which are similar to actual pavements, is still not fully understood. In this paper, deflection measurements, asphalt strains and surface cracking measurements are used to evaluate the evolution of pavement damage with traffic, during an APT experiment. The combination of these three indicators leads to a better understanding of the damage mechanisms of the pavement.

Xuan Quy Le, Mai Lan Nguyen, Pierre Hornych, Quang Tuan Nguyen
Evaluation of Service Level of Emulsions Used in Surface Treatments in Different Stages of Ageing

The application of asphalt emulsions in pavement construction is common in courses that do not require heating. Among those, it is possible to highlight chip seal (CS) treatments. In this type of pavement, it is essential to consider the performance of the binder. This paper aims to propose a study of emulsions used in CS, focusing in acquiring rheological properties that might correlate to the performance of emulsions over the service life, regarding to defects like aggregate loss and bleeding. For this purpose, it was selected a type of emulsion frequently used in this field (rapid-setting cationic emulsion). The residue of the emulsion was recovered and then it was proceeded simultaneously both the long-term ageing by means of the Pressure Aging Vessel (PAV) and ageing in UV chamber. After that, it was performed two different tests. The samples were subjected to the Dynamic Shear Rheometer (DSR), in which it was performed a frequency sweep and it was obtained the complex modulus (G*) of the materials and the MSCR test. Based on the tests developed in this study it was possible to describe the modifications occurred in the binder properties by ageing and its effects on CS pavements. Furthermore, it was possible to give predictions of bleeding during service life of the emulsion and its performance over this time, mostly relating to this defect.

Gledson Silva Mesquita Junior, Carla Marília Cavalcante Alecrim, Lilian Medeiros Gondim, Suelly Helena de Araújo Barroso
Evaluation of the Performance of Cold In-Place Recycled Base Layer Supported with Geogrid

The research presented in this study sought to determine the overall performance benefit of utilizing geogrid reinforcement in cold in-place recycled (CIR) pavement layers. A Superpave mixture with nominal maximum aggregate size of 9.5 mm was used as the control mixture while eight CIR mixtures were also evaluated. A balanced mix design approach was used to produce the eight CIR mixtures in which binder content varied (3 and 4% of CSS-1h emulsion), compaction level varied (30 and 70 gyrations) and use of geogrid reinforcement varied (with and without reinforcement). The cement and water contents of all mixtures were 1 and 3% of total mixture weight, respectively. All test specimens with and without geogrid were allowed to cure for three days at 60 °C. The approach adopted involved: performing the dynamic modulus (|E*|) tests on all mixtures and conducting a layered elastic analysis using KenLayer. The results of the layered elastic analysis were then used to compare the relative rutting and cracking performance of the CIR mixtures (geogrid reinforced and –unreinforced). The CIR mixture that contained 3% binder, compacted at 70 gyrations with no geogrid reinforcement, was found to be the best performing CIR mixture.

Ahmed Saidi, Andrae A. Francois, Ayman Ali, Yusuf Mehta
Evaluation of the Properties of Bituminous Binders Recovered from Various Sites in Europe

Binders were recovered from various sites in Europe; including locations in Belgium, Croatia, France, and UK, with a service life varying between 8 and 21 years. The asphalt cores, obtained from these sites, were first cut into thin slices, and binder recovery was conducted separately for each slice. These binders were evaluated rheologically, including parameters such as delta Tc, Glover-Rowe (G-R), and cross-over frequency. Chemically-related properties were investigated by Fourier transform infra red (FTIR) spectroscopy, and for some of the sites this was completed by a SARA separation analysis. As the original binders were not available, two approaches were followed to allow a comparison between field and laboratory aging. In a first approach, properties of recovered binders were compared to the behavior of a reference collection of bitumen, collected in the European market. This set was evaluated extensively before and after standard short- and long-term aging. In a second approach, the binders recovered from the bottom slice, which in some cases were less aged compared to the top parts, were further aged using the pressure aging vessel (PAV) standard procedure. In this way the bottom slice binder served as a reference binder for the top slices. The same trends were observed in rheological as well as in chemical properties during field and accelerated aging. In the field, binders seemed to age more than predicted by the PAV under standard conditions. For one of the PmB sections more differences were seen. The aging profile in the wearing course was dependent on the void content of the pavement.

Hilde Soenen, Xavier Carbonneau, Xiaohu Lu, Carl Robertus, Benoit Tapin
Evolution of the Thermo-rheological Indices of Asphalt Binders with Aging

Reliable characterization of asphalt binder properties with aging, as a function of pavement service life, is crucial to improving asphalt binder specifications as well as modification and formulation methods. The objective of this study is to evaluate how the thermo-rheological indices of asphalt binders change over time, and explore their potential correlations. Binders from five different mixtures are subjected to various conditioning protocols (20 h PAV on original binder as well as short-term, 5 and 12 days aging at 95 °C on loose mixtures). Binder testing is conducted using a dynamic shear rheometer (DSR) with 4 mm parallel plate geometry over a wide range of frequencies and temperatures. Numerous thermo-rheological parameters are calculated to evaluate changes with aging. The results of this study indicate that the softer binders (as described by lower performance grade high and low temperatures) and the binders with the largest difference between high and low temperature performance grades show higher aging susceptibility. However, the softer binders and those extracted from virgin mixtures (without recycled asphalt) retain better cracking performance after aging. Results also indicate that binder transition temperatures (glassy transition temperature (Tg), viscoelastic transition temperature (Tt) and magnitude of the intermediate region temperature range (ΔTIR)) generally show moderate to strong correlations with binder rheological indices (e.g. binder R-value and Glover-Rowe parameter). Binders with ΔTIR greater than 60 °C should be avoided because of poor relaxation and cracking resistance performance. The observations from this study provide insights on the relationships between an asphalt binder’s fundamental thermo-rheological properties.

Runhua Zhang, Jo E. Sias, Eshan V. Dave
Examining the Effects of a Self-healing Elastomer on the Properties of Bitumen

The development of crack healing asphalt pavements has been a growing area of research in recent years. Methods that involve external stimuli or capsules have been previously tried but have drawbacks. In order to overcome these drawbacks, the use of a thermoreversible, self-healing elastomer modified bitumen was explored. Testing thus far has indicated that the self-healing elastomer which has been chosen for this study has shown some promise. The use of the Linear Amplitude Sweep (LAS) test and Simplified-LASH (SLASH) test have indicated there may a positive effect on the restoration of mechanical properties and fatigue properties of the bitumen. Black space diagrams have indicated that the elastomeric properties have improved despite there being no significant change in the complex modulus. The change in elasticity is similar to the observed changes in styrene-butadiene-styrene (SBS) modified bitumen.

Mike Aurilio, Hassan Baaj
Experimental and Numerical Study of Low Noise Porous Asphalt Pavement

To control and reduce noise pollution in heavily frequented urban areas, the urbane community of Limoges commissioned the use of a porous asphalt. This type of asphalt is characterized by its high void content (>20%) that confers numerous advantages like its swift drainage during wet weather in addition to its noise reduction properties. However, such material presents certain limitations regarding its durability and strength compared to a conventional one. This paper aims at determining the complex modulus of the porous asphalt commissioned using an experimental method and studying the influence of the variation of voids in numerical models. The numerical approach consists of a heterogeneous multiscale modeling of the studied material. The heterogeneous scales ranging from smallest to largest are mastic and HMA (hot mix asphalt). The models are treated in ABAQUS finite element code. It can perform the numerical calculations of the complex modulus and the phase angle at various frequencies. The experimental method consists of the tension/compression test using specimens that have been cored from slabs provided by the asphalt’s mixture manufacturer. The tests are conducted for various frequencies (0.1, 0.3, 1, 3, 10 Hz) and temperatures (−10, 0, 10, 15, 20 °C). The experimental results obtained showed that the complex modulus of the studied porous asphalt is almost 30% smaller than that of a BBSG (semi-coarse asphaltic concrete) for a temperature of 15 °C and a frequency of 10 Hz.

Christina El Sawda, Fateh Fakhari Tehrani, Jérôme Dopeux, Philippe Reynaud, Joseph Absi, Christophe Petit
Experimental Evaluation of Swelling and Absorption of Crumb Rubber Aggregates

Rubber from end-of-life tires can be recycled by incorporating them into bituminous mixtures as a replacement of a part of the mineral aggregates (dry process) or as a bitumen modifier (wet process). Even in the dry process, interactions between Crumb Rubber (CR) aggregates and bitumen may occur during the mixing process and beyond, causing CR aggregates to swell and absorb aromatic fractions of bitumen at the same time. This study focuses on the experimental evaluation of swelling and aromatic oil absorption of CR aggregates. CR aggregates with a continuous 4/8 mm grain size distribution were immerged in a pycnometer full of aromatic oil whose composition is close to aromatics in bitumen. The volume of oil absorbed by CR aggregates, the grading curve and the volume of CR aggregates were determined both immediately after the immersion and after 48 h of immersion. Experimental data show that CR aggregates swell and absorb aromatic oil.

Yasmina Mahmoudi, Salvatore Mangiafico, Cédric Sauzéat, Hervé Di Benedetto, Simon Pouget, Frédéric Loup, Jean-Philippe Faure
Experimental Investigation on Ultraviolet Aging Properties of Silica Nanoparticles-Modified Bitumen

The research was carried out to explore the effect of silica nanoparticles (NPs) on the ultraviolet aging properties of bitumen. In this study, characterization of NPs-modified Bitumen using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), and ultraviolet-visible spectrophotometer were investigated. In addition, the properties of the modified bitumen considered by conventional mechanical tests. The results of this study indicated that the bitumen physical properties were influenced by silica NPs additives. Comparing oxidation degree and carbonyl in index NPs-modified bitumen samples indicates that the resistance of bitumen to ultraviolet aging is considerably improved with increase nanoparticles content, which led to the improvement in the reflection property in bitumen. Further, NPs improved the rutting resistance, viscosity, and threshold temperatures of aging bitumen, while decreasing the viscosity aging.

Goshtasp Cheraghian, Di Wang, Yun Su Kim, Michael P. Wistuba
Experimental Study on the Grading Distribution of Cold Recycled Asphalt Mixtures Produced with Bitumen Emulsion and High Strength Cement

Cold recycled asphalt mixtures (CRAM) can lead to real economic advantages only if their performance is comparable to that of traditional hot mix asphalt. This experimental study aims to investigate the effect of the grading distribution on the volumetric and mechanical properties of CRAM produced with high reclaimed asphalt dosage (>70%), bitumen emulsion and high strength cement. Four grading distributions were analysed: two continuously graded curve (derived from the Fuller-Thompson maximum density curve) with nominal maximum aggregate size (NMAS) 16 and 10 mm. The third was obtained increasing the filler dosage, and the fourth grading distribution was a gap-graded type, with NMAS 16 mm. Workability and compactability of the fresh CRAM were evaluated using the gyratory compactor. CRAM long-term complex modulus was measured using cyclic compression tests. Results showed that the gap-graded and the high-filler grading distributions allowed obtaining the lower voids in the mixture. Having fixed the number of voids in the mixture, the gap-graded CRAM showed a higher stiffness modulus and lower phase angle if compared to CRAM produced with the continuously graded curve.

Chiara Mignini, Fabrizio Cardone, Andrea Graziani
Experimental Tests on Diffusion Phenomenon Between Two Different Bitumens

A better understanding of the interaction between old and new bitumen is considered of key importance in the production of new hot asphalt mixtures with high percentages of reclaimed asphalt pavement. This improvement could potentially avoid shorter service life of the material and failure due to reduced performance in rutting and fatigue. This study is part of an on-going research in the framework of a PhD thesis. The aim of this paper is to present the experimental results focussed on the characterisation of the diffusion phenomenon between two different bitumens. A DSR has been used to experimentally measure the changes in shear complex modulus during time at 50 °C of a double-layer specimen. The main hypothesis is that a changing in the measurements of the shear complex modulus is stemmed from a changing in the structure of the sample: this implies that a blending phenomenon between the two bitumens is going on, mainly driven by diffusion between the two materials.

Stefano Noto, Salvatore Mangiafico, Elena Romeo, Cédric Sauzéat, Hervé Di Benedetto, Gabriele Tebaldi
Experimental Validation of the Dual-Oxidation Routes in Bituminous Binders

Oxidative ageing in bituminous materials is considered to be one of the most important factors for distress types in road applications. The increasing interest in oxidative ageing has highlighted the need for a thorough understanding of the oxidation mechanisms at molecular level. This paper offers some insight in the validity of the proposed hypotheses about the oxidation routes of bitumen, the fast- and the slow-rate route, reflecting on previous studies. Fourier-Transform Infrared (FTIR) and Electron Paramagnetic Resonance (EPR) spectroscopy were utilised for this verification. To elucidate the uncertain formation of sulfoxides, an additional surface investigation with Time-of-Flight Secondary Ion Mass Spectrometry (TOF-SIMS) was performed. The findings of the aforementioned techniques reveal the existence of the oxidation products reported previously and contribute to the understanding of the oxidation mechanisms. Overall, this research strengthens experimentally the hypotheses of the dual-oxidation routes of bitumen.

Georgios Pipintakos, H. Y. Vincent Ching, Uwe Mühlich, Hilde Soenen, Sabine Van Doorslaer, Peter Sjövall, Aikaterini Varveri, Christophe Vande Velde, Xiaohu Lu
Extending the Use of RAP in Airport Asphalt Resurfacing

Traditionally, airports in Australia have resisted the incorporation of recycled asphalt pavement (RAP) in resurfacing works. However, in 2018 an airport allowed RAP from the temporary construction ramps and the existing surface millings to be incorporated. These RAP materials were considered to be low-risk and medium-risk sources. Statistical analysis of the mixture design, RAP production testing and asphalt production compliance testing were undertaken to determine the potential impact of extending RAP use to include these low- to medium-risk sources in airport asphalt surfacing. It was found that the minor changes associated with the incorporation of RAP were unlikely to be detrimental. However, it was concluded that the mixture design must characterise and reflect the RAP sources, and the asphalt production must monitor the RAP, similar to other raw materials such as virgin aggregate and bituminous binder. Future work should consider extending these findings to other airport surfacing projects in Australia, allowing specification changes in the future.

Greg White, Ali Jamshidi
Factors Affecting Mortar Thickness Distribution and Its Relationship to Cracking Resistance of Asphalt Mixtures

This study introduces a novel method to determine the asphalt mortar thickness distribution through two-dimensional image processing techniques. It is claimed that in asphalt mixture design, there exists a potential optimal mortar thickness distribution, which can be used as metrics for quality control of durability. Gradation analysis from images was performed to verify the reliability of the analysis based on known gradation curve of mixtures and potential limitations for analysis are introduced. Image-based calculated gradation of asphalt mixtures is compared with gradation calculated from sieve analysis to verify accurate propotions of mixtures from images. Mixtures produced with modified and unmodified asphalt binders were utilized to compare the mortar distribution and the analysis of results is provided. In addition, three compaction temperatures were selected to investigate the temperature influence on mortar thickness distribution. The results indicate that there could be significant effects of binder modification and compaction temperature on mortar thickness distribution. Furthermore, the relationship between the mortar thickness distribution and the cracking resistance from the Semi-Circular-Bend test were analyzed. The relationships obtained verify that thinner mortar thickness, with a wider distribution, could cause the asphalt mixture to be more sensitive to aging, which is detrimental to the durability of the mixtures. The method used can be utilized for better mixture design and quality control to optimize binder content and durability.

Hussain U. Bahia, Jiwang Jiang, Ying Lia
Fatigue and Moisture Damage Resistance of Bituminous Mixtures for Railway Trackbeds

This paper focuses on the fatigue resistance properties and susceptibility to moisture damage of different bituminous mixtures used as sub-ballast layers in French railways. The analysis is made taking into account the specific working conditions and service life requirements of trackbeds. Three different road base-course mixtures used as sub-ballast layers in France were studied. A new moisture-conditioning procedure was proposed and used to induce moisture damage in the samples. Tension-compression fatigue tests were carried out on cylindrical samples at the Laboratory of Civil Engineering and Construction (LGCB) of the ENTPE, University of Lyon. All the tested mixtures were found to present satisfactory fatigue resistance properties. Low voids content and the use of polymer-modified bitumen were found to improve the resistance to moisture damage.

Diego Ramirez Cardona, Hervé Di Benedetto, Cédric Sauzéat, N. Calon
Fracture Characterization of Stone Mastic Asphalt (SMA) with Hydrated Lime Through the Semi-circular Bending Test Approach

Hydrated lime (HL) use as an active filler is due to its ability to increase the stiffness of asphalt mixtures as well as the mechanical and physicochemical performance through improved rutting resistance, reduced aging, and enhanced moisture-induced damage resistance. However, understanding of the effects of HL on fatigue or more specifically on the fundamental fracture properties of asphalt mixtures still requires further investigation. As a result, this research study assessed the fracture toughness characteristics of stone mastic asphalt (SMA) mixtures with locally available materials and testing procedures in the UK context. SMA cores were subjected to semi-circular bending (SCB) testing. The experimental matrix comprised various factors for assessing and comparing the fracture toughness of the manufactured mixtures with 0, 1, 2, and 3% hydrated lime by weight of total mixture as well as a control without hydrated lime. These factors included the effects on the fracture of (1) testing temperatures (0, 10, and 20 °C), (2) aggregate type (granite and limestone), (3) environmental conditioning (ageing combined with moisture damage), and (4) the effects of filler type and content. From the SCB experimental results, it was found that the fracture is highly factor-dependent. 2 and 3% HL improved the fracture strength of the manufactured cores, whereas 1% exhibited relatively low or negligible effects on the fracture strength. Finally, the use of granite aggregates substantiated a superior fracture resistance with a 40% increase compared to mixtures produced with limestone.

Abdallah M. Ahmed, Juan S. Carvajal-Munoz, Gordon Airey
Friction Properties of Asphalt Surfacings Containing Sintered Lightweight Aggregate

Friction properties of a natural aggregate of known good polishing characteristics and a manufactured lightweight aggregate have been determined by means of the friction after polishing test. The friction of a blend of 75% w/w natural aggregate and 25% w/w lightweight aggregate was also estimated based on the friction values of the individual components and the blend ratio. Asphalt surfacings were then designed by replacing 25% w/w of the coarse natural aggregate with lightweight aggregate. Two types of thin surfacing mixtures, SMA and AC, typically used in low speed and high speed roads, were produced and evaluated. Friction characteristics of the asphalt surfacings were determined in the laboratory using the friction after polishing test. It was found that the lightweight aggregate had superior friction and polishing characteristics to that of natural aggregate. Laboratory results also indicated that thin surfacing materials containing lightweight had better friction and skid resistance than those without lightweight aggregate.

Ignacio Artamendi, Bob Allen, Phil Sabin, Neil Leake
From Laboratory Mixes to Full Scale Test: Rutting Evaluation of Bio-recycled Asphalt Mixes

The present paper describes the rutting behavior of innovative mixes incorporating 50% of Reclaimed Asphalt (RA) with bio-materials. They were assessed in the laboratory and in a full-scale accelerated experiment. The innovative mixes studied here contained bio-materials especially designed to help recycling by re-activating the aged binder from RA. Four mixes were evaluated: three of them are manufactured with bio-materials, (two bio-rejuvenators and one bio-binder) and one was a control mix, which was a high modulus asphalt mix (EME2). In this study, the rutting resistance of the four mixes was first evaluated in the laboratory with both European and US methods. The full-scale test was then performed in order to evaluate the rutting resistance of the bio-recycled asphalt mixes under heavy traffic (200,000 load cycles loaded at 65 kN) and compared with the control one. A simplified analysis leads to the conclusion that, with the Nantes climate, a daily traffic of 150 heavy vehicles per day applied over 20 years corresponds to approximately 200,000 heavy vehicle loads when the surface temperature exceeds 30 °C. Therefore, it can be considered that the rutting evaluation made on the carrousel represented almost 20 years of traffic during hot-day periods. The results obtained on the test track were consistent with the laboratory rutting tests showing good performance for all the mixes. The materials presenting the best performance on the test track also presented the best performance in the laboratory.

Juliette Blanc, Emmanuel Chailleux, Pierre Hornych, Chris Williams, Zahra Sotoodeh-Nia, Laurent Porot, Simon Pouget, François Olard, Jean-Pascal Planche, Davide Lo Presti, Ana Jimenez del Barco
Full-Scale Pavement Testing of a High Polymer Modified Asphalt Concrete Mixture

Asphalt concrete (AC) mixtures with high polymer (HP) content (i.e., >6% polymer content) may offer additional advantages in flexible pavements subjected to heavy and slow-moving traffic loads. The objective of this effort was to evaluate the structural response of an HP AC mixture using full-scale pavement testing. Two experiments were conducted: Experiment 1 consisted of a PMA AC layer on top of a crushed aggregate base (CAB) and a subgrade (SG), and Experiment 2 consisted of an HP AC layer with a reduced thickness on top of the same CAB and SG. Both pavements were subjected to dynamic loads applied at the pavement surface simulating falling weight deflectometer (FWD) loading conditions. Pavement surface deflections along with critical pavement responses at different depths and locations within the pavement layers were monitored during testing through embedded instrumentations. Field-produced mixtures were sampled during construction and evaluated for performance properties. At the end of each experiment, cores were cut from the AC layer for in-place density measurements. In general, at the centerline of the load, the reduced thickness of the HP AC layer resulted in higher vertical surface deflections and vertical stresses at the middle of the CAB layer and at 15.2 cm below the surface of the SG layer. The mechanistic analysis of the built pavement structures showed that the HP pavement would result in better AC fatigue and rutting performance, higher rutting in the unbound layers, but similar total pavement rutting.

Jhony Habbouche, Peter E. Sebaaly, Elie Y. Hajj, Murugaiyah Piratheepan
GLOBE: An Innovative Technical Solution to Ensure Waste Free Cold Logistic of Bituminous Binders

GLOBE is a French acronym for “Granulés pour la LOgistique des Bitumes d’Enrobage” literally meaning «Bituminous granulates for the logistic of coating binders». This project supported by ADEME (French Environment & Energy Management Agency) focuses on the development of an innovative technical solution to ensure a logistic of bituminous binders from refineries to asphalt mix plants which is cold, waste free and thus cleaner and safer. The main challenge is to modify a material such as bitumen, usually handled hot in liquid form, in order to be able to produce a granular form of it, which stays stable over time. In order to do that, it is required to overcome in-depth its typical binder characteristics, especially its creep behavior and its exceptional adhesiveness properties. This implies to modify the rheology of the binder and to take into consideration the granulation technology. The final product should avoid agglomeration phenomena, while taking into account the mechanical and thermal stresses associated with the handling, storage and transport of the pellets.

Mouhamad Mouazen, Yvong Hung, Olivier Moglia, Pauline Anaclet, Alice Ngo, Serge Krafft, Flavien Geisler, Vincent Gaudefroy
Healing Characterisation of Waste-Derived Bitumen Based on Crack Length

This study aims to characterise the fundamental healing behaviours of waste-derived bitumen based on crack length. A first waste-derived bitumen was fabricated using bio-oil pyrolysed from the organic fraction of municipal solid waste and mixed with a control bitumen (X70) at a concentration of 5wt.%. A second waste-derived bitumen was fabricated by blending waste plastics (6wt.% LDPE) with X70 at 180 °C using high shear mixer at 900 RMP. The healing tests were designed as a fatigue-rest-fatigue procedure using DSR, where the fatigue load was strain-controlled (5%) at a frequency of 10Hz. The healing tests were performed at different rest start times (5 min, 10 min and 20 min), rest durations (10s, 0.5 min, 1 min, 5 min, 10 min, and 20 min), and temperatures (15, 20, and 25 °C). Results show that the normalised healing index defined by crack length can provide a fundamental and accurate characterisation of the healing properties of different types of waste-derived bitumen. Bio-oil and LDPE can enhance the healing capacity and healing rate of the control bitumen. High temperature speeds up healing. The healing evolutions are modelled by Ramberg-Osgood model and it was found that the LDPE modified bitumen heals faster than the control or the bio-oil modified bitumen in a short term. However, the bio-oil modified bitumen heals the most among the three.

Linglin Li, Yangming Gao, Yuqing Zhang
High Temperatures Characterization of Polymer Nanocomposite Modified Asphalt Binder

The performance asphalt binders modified with Copper Oxide nanoparticles (CuO) and Calcium Carbonate nanoparticles (CaCO3) was investigated. The base asphalt was blended with 5% of Acrylonitrile styrene acrylate (ASA) copolymer and different concentrations of nanoparticles were added by 3% and 5% of CuO and CaCO3 by weight of bitumen. The dynamic shear rheometer was used to investigate the rheological characteristics of modified asphalt binders. The evaluation indicates that the modified asphalt binders have a greater resistance to rutting, better durability, and lower susceptibility to high temperatures. Besides, the rheological properties also improved, as the master curve of the modified asphalts with CuO and CaCO3 drawn increasingly viscoelastic behaviour compared to base asphalt. Moreover, the modification shows that the failure temperature of the asphalt binder increased with addition increment of modifiers, regardless of the modification type while the permanent deformation of modified samples reduced compared to base asphalt. The 3% CaCO3 exposed better characteristics of modified asphalt among all the blends.

Shaban Ismael Albrka Ali, Rebaz Yousif Ahmed, Peshawa Sediq
How to Improve the Miscibility of Asphalt Binder and Polyolefins by Phosphoric Acid

As it is known, the bitumen has excellent adhesive and waterproofing properties, but if used alone, it hasn’t good mechanical properties, for example, it becomes brittle at low temperatures (Fawcett et al. in J. Elastomers Plast. 31:334–352, 1999). In order to increase the mechanical properties of bitumen such as adhesion, elasticity, thermo-mechanical resistance, usually it is possible to add some polymer such as polyolefinic plastomers or styrenic plastomers (Fuentés-Audén et al. in Polym. Testing 27:1005–1012, 2008). However, polyolefinic plastomers are easily available, they have a low cost and display a higher stability than styrenic plastomers (Porto et al. in Appl. Sci. 9:742, 2019). The addition of polyolefins to bitumen leads to the creation of a biphasic structure, which is composed by a dispersed phase and a continuous phase. Unfortunately, polyolefin modified bitumen suffer from lack of storage stability and the polymer separates from bitumen gradually. This is due to a low compatibility between polymer and bitumen. The phase inversion (high compatibility) should occur in the modified bitumen depending mainly on the density, molecular weight, polarity and solubility (Zhu et al. in Eur. Polymer J. 54:18–38, 2014). The phase inversion often is not observed due to poor affinity between Polymer/Bitumen. The main goal of the present research is to improve the miscibility of polyolefinic plastomers and bitumen through phosphorus compounds which can change the bitumen structure in particular the asphaltenes aggregation pattern thanks to polar-polar interactions.

Paolino Caputo, Valeria Loise, Francesca R. Lupi, Emanuela Lombardo, Ines Antunes, Cesare Oliviero Rossi
Humidity Damage Index (HDI) of Recovered Asphalt from Reclaimed Asphalt Pavement-RAP Using Different Aggregates

Use of high amount of reclaimed asphalt pavement (RAP) in roadway construction brings considerable environmental and economic benefits. However, these gains are accompanied by challenges in design and construction to ensure the pavement quality is not compromised. Among the factors to consider is to determine how the RAP aged binder affects the adhesion between the binder and aggregate. This study was undertaken to address the preceding question using different aggregates when brought in contact with the RAP binder. The Atomic Force Microscopy (AFM) for recovered binders and one of the original ones were made, in order to understand their chemical composition and its relationship with the adhesion. Adhesion was evaluated using the bond strength test (BBS), wettability test, and surface free energy. The results were used to establish the Humidity Damage Index (HDI). This index is defined as the relationship between the work of adhesion asphalt-aggregate and the work of debonding or reduction in the system´s surface free energy, Results indicated that (Z)Recovered RAP(CO) is highly resistant to moisture damage in field combined with Sandstone SDM(CO) and medium resistance with Limestone(CO) and Sandstone SDA(CO). The different mineralogy’s aggregates showed a significant influence of the HDI result. The combination of aggregates and the Colombian 60–70 dmm asphalt P indicated high susceptibility to moisture damage. The combination of Silica (US) with PG 64-22 asphalt showed the highest resistance to moisture damage. The AFM and SARA results show the huge difference between recovered binders from Colombia and the USA, in fact the (Z) Recovered RAP(US) had better colloidal distribution than the original binder pen 60–70 dmm (CO).

Ana Figueroa, Mansour Solaimanian
Impact of Different Fillers on the Properties of Asphalt Mixtures

Different mineral fillers from various sources in Portugal were compared as such, in mastics and in asphalt mixtures. The materials included recovered mineral fillers of varying petrographical origin (limestone, granite or rhyolite) obtained from the dedusting system of local asphalt plants, and commercial fillers, active or not, such as limestone filler, hydrated lime, natural hydraulic lime and Portland cement. All fillers were compared using standard filler tests, including dry porosity (Rigden air voids—EN 1097-4), bitumen number (EN 13179-2) and delta Ring and Ball (EN 13179-1). The impact of the filler on the chemical ageing of the binder was also studied using the Pressure Aging Vessel (PAV) test. Finally, dense and porous asphalt mixtures were manufactured with some selected fillers. Their resistance to moisture damage was evaluated using respectively the Indirect Tensile Strength Retained (ITSR - EN 12697-12) and the Cantabro test (EN 12697-11 and NLT-362). From this thorough study, the effect of the different fillers can be compared on all aspects of their potential impact on mixture properties: resistance to moisture damage, aging and mechanical properties. The benefit of using an active filler is clearly demonstrated, especially in the case of hydrated lime.

Adriano Teixeira, Didier Lesueur
Impact of the Performance of the Asphalt Concrete and the Geogrid Materials on the Fatigue of Geogrid-Reinforced Asphalt Concrete—Experimental Study

Geogrids are used in asphalt layers in transportation infrastructure since 1980s. Various authors describe this kind of interlayer systems that are used to reduce reflective cracking and increase fatigue life. A recent research work published by Arsenie in 2013 focused on the impact of the fatigue life of asphalt concrete reinforced with geogrid. Part of this study consists in the laboratory study of the impact through 4 points bending fatigue tests and demonstrate a better fatigue performance due to the use of geogrid. The initial aim of the work presented here was to reproduce this results and correlate increase of fatigue performance to the property of the geogrid. However, the experimental results were unexpected and leads to completely new conclusions. The paper presents the key references of the literature. Then, the authors present the careful preparation of samples. The results are presented and analyzed. Finally, the conclusion discusses and compares the new results with the literature and draw some perspective upon the evolution of the fatigue criteria to be used for further study.

Bertrand Pouteau, Antoine Martin, Kamal Berrada, Jacques-Antoine Decamps, Patrice Diez
Impact of Viscoelastic and Fatigue Behavior of Asphalt Mixtures Made with RAP and Asphalt Shingle on the Life Cycle Assessment Results

The use of reclaimed asphalt pavement (RAP) and recycled asphalt shingles (RAS) for the production of new asphalt mixtures has significant effect on their viscoelastic and fatigue properties. Experimental results show that addition of RAP (up to 40%) and asphalt shingle (up to 5%) in asphalt mixtures increased the stiffness and improved the fatigue properties (ε6 parameter). This paper investigates the influence of the viscoelastic and fatigue properties on the environmental performance of a secondary road operated for 20 years over its whole life cycle. Results showed that the use of asphalt mixtures with higher proportion of RAP and RAS had lower global warming potential (GWP), primarily due to the lower use of raw materials and secondarily due to changes to the use phase impacts. Longer road lifecycles and higher levels of road traffic are expected to considerably increase the contribution of the road service phase and in particular that due to pavement deflection at locations experiencing high temperature climates.

Nikolaos Vlasopoulos, Duc Tung Dao, Nouffou Tapsoba, Hervé Di Benedetto, Cédric Sauzéat, Mohsen Ech, Nicolas Miravalls
Implementing Crumb Rubber Gap-Graded and Open Graded Asphalt Technologies—The Australian Experience

Approximately 48 million tyres reach the end of their lives in Australia each year and a substantial proportion of these end up in land fill sites. Although crumbed rubber modified bitumen is used extensively worldwide, the application has been very limited in asphalt mixes in Australia. The paper summarises the performance assessment of the crumb rubber gap-graded asphalt—GGA14(CR)—and open graded asphalt—OGA10(CR) which were trialed in 2018/19. Both asphalt mixes were designed and manufactured with warm mix technology, allowing lower mixing and compaction temperatures, resulting in significant energy saving and emission reduction. The paper discusses the crumb rubber binder blend properties and its storage stability over time. The benchmarking of the rheological properties were carried out by means of the dynamic shear rheometer. Details on the volumetric mix design and performance based mix design such as moisture sensitivity, Hamburg wheel tracking and particle loss tests are provided in the paper for the relevant mix type. The paper also provides details of the manufacturing and construction and field procedures.

Laszlo Petho
Improved Testing Setup for Real-Time Monitoring of PMBs During Manufacturing and Rotational Viscosity Measurements

Polymer modified binders (PMBs) are a practical solution to design asphalt mixtures with superior performance. Although these polymers often improve bitumen properties to some extent, their final performance are linked to the accurate control of the properties during manufacturing and storage. However, some of the common procedures used to characterise neat bitumen are not suitable with these binders making their characterisation challenging. This study presents a novel laboratory procedure to produce SBS-MB through a real-time monitoring of the rotational viscosity, as well as an attempt to understand the suitability of current testing geometries to measure viscosity of such a complex bituminous binder. The proposed innovation lies in the adoption of a Dual Helical Ribbon (DHR), as a novel mixing/measuring device for rotational viscometers. The laboratory tests were undertaken by using the DHR and a standard coaxial cylinder configuration with a spindle geometry (SC27) as a control to record eventual differences in viscosity measurements of PMBs. As a result, the real-time monitoring procedure improved the governing of the modifications process, furthermore, it was proven that when blends with high polymer content and no cross linker are tested, the conventional coaxial cylinder setup for rotational viscosity measurements might not be adequate and spindle geometries should be replaced with the DHR.

G. Giancontieri, Simon Pouget, Davide Lo Presti
Improving the Durability of Asphalt Mixtures with Hydrated Lime: Field Results from Recent French Sections

Although known for a long time, hydrated lime (HL) still attracts a strong technical interest as an asphalt additive. This presentation describes recent field results obtained in France in two different contexts: • First, we describe the 7-years experience obtained on 20 sections with and without HL in the mountainous Vosges department. This eastern part of France is characterized by cold winters and significant elevation, making it a pretty challenging environment for asphalt mixtures. The types of mixtures were essentially semi-dense Asphalt Concrete (French BBSG). The results after 7-years of monitoring are described. • Second, we describe the 5-years experience obtained on 5 sections with and without HL in the oceanic climate of Highway A84 in Normandy. The types of mixtures were also semi-dense Asphalt Concrete (French BBSG) and a thorough testing program was established from the beginning. The results after 5-years of monitoring are described. As a result, the results allow quantifying the impact of HL in terms of durability improvement.

Didier Lesueur, Pierre Métais, Patrick Pibis, Samyr El Bedoui, Hervé Ruat, Stéphane Bouron, Ferhat Hammoum
Improving the Modulus Master Curve of Bituminous Mixes Using Ultrasonic Measurements

The stiffness of bituminous mixtures varies with temperature and frequency of load due to its viscoelastic nature, and this behavior is represented by the modulus master curve. This curve can be constructed using laboratory test results and models based on known material properties. This approach uses material specifications to provide a good estimation of the modulus over a range of frequencies. This estimated curve should be corrected with respect to a measured reference value; which can be obtained by non-destructive ultrasonic methods. Once the dynamic modulus at high loading frequencies is measured with the ultrasonic test, the predictive master curves can be calibrated as to represent the materials properties in the linear viscoelastic domain. In this study, Ultrasonic Waves Velocity (UWV) tests are conducted on specimens of two laboratory prepared mixes to correct the conventional modulus master curves. Moreover, the variability introduced by ultrasonic receiver type and coupling in the UWV measurements are examined, and a practical testing configuration is proposed. The measured dynamic moduli are found consistently higher than the conventional master curves; which underestimate the modulus of bituminous mixture. Finally, the method is verified by shifting the moduli measured at different frequencies and temperatures to the reduced frequencies at the reference temperature of 20 °C.

Pejoohan Tavassoti, Taher H. Ameen, Hassan Baaj, Giovanni Cascante
Influence of Aggregate Gradation on the Permanent Deformation of Asphalt Mixtures

The following study aims to measure the resistance to permanent deformation of mixtures with varying aggregate gradation and correlate these results to the performance predicted by the Marshall stability test. The experimental study is performed on 6 mixtures designed with the Marshall mix design method and measured using the wheel tracking test. The total rut depth obtained with the wheel tracking test shows a high correlation to the Marshall flow values, as higher rutting corresponds to mixtures with higher flow. The study has shown the ability of Marshall flow value to predict the resistance to permanent deformation, independent of asphalt mixture type, as well as a close correlation between aggregate gradation and stability.

Bernardita Lira, Robert Lundström, Jonas Ekblad
Influence of Binder Properties on Dynamic Shear Response of Asphalt Mixture

For predicting the shear-related rutting potential of asphalt pavement, it is important to understand the shear response of asphalt mixture and find the link between the mixture response and component material properties. Using controlled aggregate gradation, this paper investigates the influence of bituminous binder on the response of asphalt mixture under dynamic shear loading. Four asphalt mixtures, with two different grades of bitumen, were analysed by a simple shear test apparatus with dynamic loading. The binders, both original and after short-term aging, were characterised using a dynamic shear rheometer. The modulus and phase angle of both the asphalt mixture and bitumen samples were measured. Master curves were constructed. The results revealed that the asphalt mixture phase angle maximum, where a rutting performance indicator can be obtained, appears in a relatively narrow range of shear modulus. This range corresponds to a certain level of bitumen complex shear modulus (G*) and phase angle. By temperature sweep, a temperature value can be interpolated at the specified bitumen G* level. This temperature provides a possibility to predict the frequency of phase angle maximum for a given asphalt mixture type. It is noted that the asphalt mixture phase angle maximum corresponds to a relatively high bitumen modulus level compared to other high-temperature criteria.

Jiqing Zhu, Abubeker Ahmed, Xiaohu Lu, Safwat Said
Influence of Confinement Pressure on the Viscoelastic Response of Bituminous Mixtures

This investigation reports the use of stress-strain-time data for different frequencies at a given temperature for computing the retardation spectra. While the existing attempts use a master curve based approach with continuous relaxation spectra, the use of a discrete retardation spectrum at a given temperature directly computed from the model parameters can be useful and is devoid of the associated approximations. Such an approach also amplifies the difficulties related to identifying a unique Prony series parameters for a wide range of frequencies at any given temperature. A dense graded bituminous mixture prepared with an unmodified binder was used for the study. The tests were performed on cylindrical specimens with 100 mm diameter and 150 mm height. The specimens were tested at six frequencies, ranging from 25 to 1 Hz, for two temperatures, 5 and 35 °C, in unconfined condition as well as at a confinement pressure of 200 kPa. The stress-strain response at these frequencies and temperatures were used in the estimation of material parameters for a generalized Voigt-Kelvin model. Depending on the temperature, frequency of loading, and confinement pressure, a Prony series with a spectrum of retardation time was selected. The results show that at a given temperature, a single set of model parameters is not sufficient to describe the strain response at multiple frequencies. In addition, the Prony series coefficients are shown to vary significantly at 35 °C for the confined tests, while the difference between unconfined and confined tests are insignificant at 5 °C.

B. S. Abhijith, S. P. Atul Narayan, J. Murali Krishnan
Influence of Linear Viscoelastic Behaviour of Pavement Layers Interface for Heavy Weight Deflectometer Test

This paper presents a study in which an advanced constitutive model the viscoelastic behaviour of pavement layer interfaces is implemented in a pavement structure simulation. In particular, the study focuses on the effects of frequency and temperature-dependent behaviour of pavement layer interface. The airfield pavement response under Heavy Weight Deflectometer (HWD) load is investigated through a simulation performed using the Spectral Element Method (SEM). The numerical model includes dynamic effects and viscoelasticity for bituminous mixtures as well as interface between them. Results show the importance of taking into account the real behaviour (viscoelastic) of interfaces rather than a simplified one (sliding or bonded).

Jean-Marie Roussel, Hervé Di Benedetto, Cédric Sauzéat, Michaël Broutin
Influence of Natural Aggregates’ Mineralogical Composition on the Adhesiveness and Affinity of Bitumen

The paper presents the studies and the laboratory researches performed on two important factors that influence the durability of the asphalt mixture, namely the adhesiveness and affinity of bitumen to aggregates. To highlight the two characteristics, one bitumen grade (50/70) and natural quarry aggregates from five different sources were used. The experimental program consisted of determining the adhesiveness through the qualitative method (spectrophotometric method, nondestructive method) and the affinity through the rolling bottles method (destructive method), the main purpose of this study being to draw the attention to a possible link between these two methods. The results obtained vary from one aggregate source to another given the morphology and the physical-chemical properties of the aggregates. The research findings complete the picture of the factors that influence the adhesiveness and affinity of bitumen to aggregates and highlight the susceptibility to the stripping of binder under the humidity effect of the aggregate-binder bond.

Adelin Stirb, Paul Marc, Anda Belc, Florin Belc, Gheorghe Lucaci
In-Situ Cold Recycling Solutions for Roads Maintenance at the National Roads Network in Romania

As a response to the negative impact of private companies on the quality of works and deadlines that carry out maintenance works for the National Roads, of the fluctuations of the economic growth in EU and Romania, with the correlation with the public funds allocated, National Company for Road Infrastructure Administration has decided to buy machinery and prepare its own staff for carrying out works of roads based on cold recycling solutions. The recycling solutions were mainly based on in place recycling with bitumen emulsion or foamed bitumen with Wirtgen recyclers type WR 240i. This paper presents the laboratory tests for the mix design and a few comparison for road layers that have been made by cold recycling in place with bitumen emulsion.

Marian Peticila, Marius Muscalu, Ioan Stetco, Marian Raicu
In-Situ Measurements of Variations of RAP Contents in Hot Mix Asphalt by a Handheld FT-IR Spectrometer

Excessive use of reclaimed asphalt pavement (RAP) in hot mix asphalt (HMA) has a detrimental consequence on the performance of asphalt pavement. Continuous quality control is crucial during the production phase, but it remains challenging to do so. Handheld Fourier Transformed Infrared Spectrometer (FT-IRS) has an advantage over other test methods with respect to mobility and faster processing time which makes it a potential candidate for being a quality control tool. In this study, RAP mix from ten selected projects were investigated during the production phase using a handheld FT-IRS to determine the RAP content in the fresh mix. Carbonyl index of unaged binder (varies from 0.0166 to 0.0283) and RAP binder (varies from 0.0577 to 0.0924) were measured before the mixing began. Assuming a linear increase in carbonyl index with addition of RAP, the amount of added RAP in the mix was determined. Attenuated total reflectance (ATR) FT-IR spectrum was collected utilizing a small amount of binder which can be extracted in the field in 15 min by the quick extraction method developed in this study. At least five samples from each mix were collected at different intervals to investigate the amount of RAP in the mix. Plant samples showed the variation in RAP content within ±5% range which can be attributed to either inadequate blending or addition of variable amount of RAP. This study with ten field projects indicates that handheld FT-IRS has the potential to be used as an effective quality control tool.

Shams Arafat, Nazimuddin M. Wasiuddin, Delmar Salomon
Interlaminar Mode-I Fracture Characterization Underwater of Reinforced Bituminous Specimens

In order to investigate the interlaminar mode I fracture behavior of pavements, Wedge Splitting Tests (WST) have been developed for specimens extracted directly from field sections. As part of the French SolDuGri project focusing on bituminous pavement reinforced by glass fiber grids, WST are applied under static loads and different climatic conditions. This paper highlights the impact of water on such an interlaminar bond characterization. Results derived from samples of five to ten specimens (unreinforced or reinforced with two types of grids) tested under each type of conditions are reported here. The Digital Image Correlation (DIC) technique has been used herein. Depending on the glass fiber grid used, the observation of fractured interfaces and splitting force-crack mouth opening displacement (CMOD) curves does reveal differences. The presence of water in the bituminous emulsion influences on the dispersion of results depending on some type of interfaces. These interlaminar mode-I fracture characterizations should yield greater insight into results recently obtained from accelerated pavement tests conducted on the IFSTTAR fatigue carousel.

Maissa Gharbi, Armelle Chabot, Jean-Luc Geffard, Mai Lan Nguyen
Interphase Relations in the Characterisation of Bitumen Emulsion-Cement Composites

Strategic research on bitumen emulsion-based materials is substantial for addressing numerous environmental effects of road infrastructure. The present specifications for bitumen emulsions are based on properties that are insufficient for a fundamental understanding of their relation to the physicomechanical behaviour of realistic coarse-graded materials for structural layers. The aim of the interlaboratory testing (ILT) of RILEM TC 280-CBE Task group 1 is to investigate the link between the intrinsic interphase relations and macroscopic physicomechanical behaviour of bitumen emulsion-cement composites. Thus, the objective of this individual research was creating the basis for the above ILT by experimental and analytical evaluation of mortar-based model systems, by investigating their physicomechanical behaviour, and by conducting the sensitivity analysis of the relations between phases. The experimental evaluation comprised compactability and volumetric evaluation of fresh mixtures, indirect tensile-based testing at different stages of curing, as well as the temporal measurement of the evaporation of water from specimens.

Miomir Miljković, Andrea Graziani, Chiara Mignini
Introducing an Improved Testing Method to Evaluate the Fatigue Resistance of Bituminous Mortars

An improved test is proposed to determine the fatigue resistance of bituminous mortars by applying time-sweep cyclic (oscillatory) tests using a dynamic shear rheometer (DSR). To evaluate its applicability, a bituminous mortar mixture derived from a dense asphalt concrete (AC) mix was utilized. The objectives of this study were twofold; firstly, to design a new geometry that ensures higher repeatability of measurements and failure at a predefined zone. Secondly, to provide a methodology to evaluate the fatigue resistance of a mortar sample including the theoretical design of the mortar composition and the actual fatigue test protocol. The findings of this study present an efficient test procedure for the estimation of the fatigue life of bituminous mortars, with a consistent fracture zone, reproducible mortar samples and high coefficient of determination (R2) for the fatigue curves. Reflecting on other fatigue testing approaches, this theoretical and empirical study provides additional value towards standardization of fatigue testing in bituminous mortars.

Alexandros Margaritis, Georgios Pipintakos, Li Ming Zhang, Geert Jacobs, Cedric Vuye, Johan Blom, Wim Van den Bergh
Investigating Fatigue Characteristics of Asphalt Binder Modified with Phase Change Materials Using Dynamic Shear Rheometer

This paper aims to evaluate fatigue properties of asphalt binder modified with different percentages of phase change materials (PCM) using dynamic shear rheometer. Phase change materials (PCM) are materials that absorb, store, and release thermal energy during the thermal cycle process. Even though this property can be used to create a self-temperature controlling pavement, very limited studies have been conducted to investigate the effect of using PCMs on binder and mix performance, and therefore the pavement performance. In this study, Linear Amplitude Sweep (LAS) tests were performed to evaluate the fatigue characteristics of an asphalt binder that contains two percentages (by weight) of PCM; 3 and 6%. The results were then compared with virgin asphalt binder. Moreover, the asphalt binder with different percentage of PCM was tested under the Environmental Scanning Electron Microscope (ESEM) and results show a significant difference in the microstructure comparing with the virgin asphalt binder.

Haya Almutairi, Dandi Zhao, Hassan Baaj
Investigating the Creep and Fatigue Properties of Recycled Asphalt Concrete Containing Waste Engine and Waste Cooking Oil

This study attempts to investigate the viability of using waste engine oil (WEO) and waste cooking oil (WCO) as rejuvenator in asphalt concrete containing reclaimed asphalt pavement (RAP). Different percentages of the waste oils, namely 0, 5, 10 and 15% (by the weight of total binder) have been added into an asphalt concrete containing, 25, 50 and 75% of RAP and the effects on creep and fatigue properties have been investigated. The rutting resistance was found to increase with adding RAP, with lower increase for adding 50% RAP than 25 and 75%, and decrease with adding WEO and WCO, with lower decrease for adding 10% than adding 5 and 15%. Stress controlled fatigue tests showed that the fatigue resistance of non-rejuvenated mixtures grows with increasing RAP content, and, in general, the increase of WEO/WCO dosage results in the decrease of fatigue life. At the same dosage of rejuvenator, WEO results in more fatigue life than WCO, indicating that higher WEO is allowed to be used in recycled mixtures.

Hasan Taherkhani, Farid Noorian
Investigating the Nonlinear Behaviour of Neat and Modified Binders Through Large Amplitude Oscillatory Shear (LAOS) Testing

Asphalt Cements (ACs) are typically characterized within their Linear Viscoelastic (LVE) range, where they are treated as thermo-rheologically simple materials. Such assumption simplifies characterization of asphalt behaviour over a wider range of time- and temperature-varying conditions by applying time-temperature superposition principle. However, the LVE-based tests cannot capture the nonlinear behaviour of binders under larger strains, which is an important aspect towards proper characterization of flexible pavement materials. Nowadays, various modification techniques are employed to engineer the desired rheology of asphalt cements, which also signifies the need for better understanding the nonlinear behaviour of modified binders. Therefore, the Large Amplitude Oscillatory Shear (LAOS) testing and Fourier Transform (FT) analysis, originally rooted in polymer science, were utilized in this study to characterize the nonlinearity of neat and modified ACs. To this end, the neat asphalt cements were treated with either 0.5% of a warm mix asphalt (WMA) additive or 4.0% of an elastomer. The elastomer used is Styrene-Butadiene-Styrene (SBS) based polymer. The specimens were then aged in the laboratory to simulate the short- and long-term aging process prior to performing the LAOS strain testing. The results obtained at the intermediate temperature were used in the FT Analysis to quantify the nonlinearity of the ACs. This technique can be successfully used to distinguish the contribution of nonlinearity from other factors such as damage.

Pejoohan Tavassoti, Roberto M. Aurilio, Dandi Zhao, Hassan Baaj
Investigating the Use of a Binder Cohesion Test to Evaluate Cracking Resistance of Asphalt Mixtures

A number of different factors influence the overall performance of asphalt binder and consequently asphalt mixtures. These include intrinsic factors such as the use of modifiers, additives, reclaimed asphalt pavement (RAP) and other extenders. In particular, the fracture resistance of the asphalt binder is of importance because of the role of asphalt binder in resisting the tensile stresses in an asphalt mixture. Existing tests and metrics commonly used to quantify the cracking resistance of the asphalt binder suffer from some drawbacks. Specifically, most commonly used tests are based on rheological measures that do not induce damage in the test specimen and/or tests that subject the asphalt binder to a stress state that is not representative of the stress state that the binder experiences in an asphalt mixture. It was hypothesized that the poker-chip test geometry and parameters obtained from conducting a tensile strength test using this geometry could be used as an indicator for the cracking resistance of asphalt binders. A test protocol was developed in order to validate the efficacy of this method. Crack resistance tests were performed using two different mixture performance tests, the overlay test (OT) and the indirect tensile strength (IDT) test, on 16 different asphalt mixtures. The binders extracted and recovered from these mixtures were evaluated using the poker-chip test method. This study demonstrates that a tensile strength test conducted using the poker-chip geometry can be used as an indicator of cracking resistance of asphalt binders.

Angelo Filonzi, Ramez Hajj, Satyavati Komaragiri, Amit Bhasin
Investigation of Cold Regions Dense Graded HMAC (EME) Sensitivity to Bitumen and Filler Content

High modulus asphalt concretes (HMACs), enrobés à module élevé (EMEs) in French, improve asphalt pavement durability due to their high rigidity, high resistance to rutting and fatigue and in some cases very good low-temperature behaviour. The goal of the current study is to perform a sensitivity analysis of HMAC (EME) developed specifically for cold regions. This sensitivity study is based on laboratory experimentation. From the control mix, four bituminous mixes were tested according to a two-level full-factorial experimental design, thus varying amounts of bitumen and filler according to the most critical cases that may occur in the plant and allowed by quality standard. Stiffness, low temperature, and rutting resistance were investigated in the current study. The results show that a variation of the bitumen content will not significantly affect the stiffness, the rutting resistance and the low temperature cracking of HMAC mixes. Moreover, the results show that the filler content does not have a significant impact on the measured properties. HMAC studied appears very promising from a manufacturing point of view since it does not require more attention during the manufacturing process than conventional hot mix asphalt (HMA).

Charles Neyret, Sébastien Lamothe, Daniel Perraton, Alan Carter, Marc Proteau, Hervé Di Benedetto, Bertrand Pouteau
Investigation of Cracking Potential of Modified Asphalt Mixes Composed of Synthetic Fibers by Performing 4-point Bending Test

Fatigue cracking on Hot Mix Asphalt (HMA) affects the serviceability and quality on roads. Past studies have shown that synthetic fibers have the potential to enhance the fatigue properties of asphalt concrete, which motivated the present work to evaluate the effectiveness of adding polymer fibers to hot mix asphalt, to increase the resistance of HMA to fatigue cracking at intermediate temperatures. For this purpose, three different types of polymer fibers, including aramids, polyethylene terephthalate (PET) and polyacrylonitrile (PAN), in different sizes and at different concentrations, were added to conventional hot asphalt mixes. The impact of different parameters such as strain level and fiber content were evaluated on reinforced and unreinforced mixes by the four-point beam fatigue test. Finally, the output of the bending fatigue test was compared with the results of the IDEAL CT test to evaluate the correlation between these tests.

Luis Alberto Perca Callomamani, Leila Hashemian
Investigation of Different Design Methods for Determining the Appropriate Binder Ratio on Recycled Asphalt Mixtures

With the current concern about environmental issues and scarcity of raw materials, the production of recycled asphalt mixtures with high contents of reclaimed asphalt pavement (RAP) has been established as a sustainable and cost-effective solution. However, the increase of RAP content in recycled mixtures without loss in field performance is still a challenge. Among the reasons for that is the lack of a well-accepted and recognized mix design method to calculate the appropriate blending ratio between virgin binder and RAP binder. Blending charts are usually applied to determine this ratio, but different parameters can be used to construct them. In Europe, binder penetration is traditionally used, while performance-based parameters are preferred in the United States. In the present paper, different methods are applied to determine the appropriate ratio between RAP binder and virgin binder in different asphalt mixtures, for different types of RAP. The objective was to determine how the use of different parameters in the blending charts affects the blend design for the recycled mixture. Results showed that using penetration may promote the use of higher RAP contents in recycled mixtures, while using the performance grade parameters may result in lower RAP contents. The Jnr parameter of the MSCR test was also applied, and showed mixed results depending on the material analyzed. The results highlight the need for studies that correlate blend design and field performance, in order to improve mix design methods and ensure adequate performance for high-RAP mixtures.

Matheus S. Gaspar, Gustavo S. Pinheiro, Kamilla L. Vasconcelos, Liedi L. B. Bernucci
Investigation of Fracture Behavior of Recycled Asphalt Mixtures Using a Discrete Element Computational Model

A discrete element computational model is used to simulate the fracture behavior of asphalt mixtures, containing different RAP proportions, at low temperatures. In this model, coarse aggregates are explicitly represented by rigid spherical particles. The bonds that connect these particles represent the fine aggregate matrix (FAM), which is defined as the combination of asphalt binder and fine aggregates. The model is used to investigate the fracture behavior of four asphalt mixtures with different RAP contents. Semi-circular bend (SCB) fracture tests are performed on the asphalt mixtures and bending beam rheometer (BBR) strength tests are performed on FAM at low temperatures.

Meng Xu, Jia-Liang Le, Tianhao Yan, Mugurel Turos, Mihai Marasteanu, Decheng Feng
Investigation of the Performance of Warm Mix Asphalt Additives on 50/70 Penetrated Bitumen and Pre-cost Study

Efforts to improve flexible and rigid pavement technologies are continuing rapidly in road pavement applications that are renewed and developed day by day. This improvement can be achieved by optimizing energy, environment, worker health and cost. The production of WMA is related to increasing the aggregate-bitumen composition and achieving the proper viscosity of the bitumen to ensure that the mixture is compacted and applied at low temperatures. In this study, WMA additives added to bitumen which is the binding material of flexible road pavement were evaluated depending on bitumen viscosity, penetration and softening point. Two of the additives used are PAWMA and SASOBIT additives known in the market. Three of them are and MGB additives which are still under development by us. Bitumen viscosity was measured at 110 °C, 135 °C, and 150 °C included SASOBIT, MGB, and were tested by adding 3% by weight of bitumen and PAWMA was tested by adding 0.3% by weight to bitumen. The performance of pure bitumen and bituminous mixtures was supported by the penetration and softening point values depending on the viscosity results. As a result of the experiments, it has been observed that SASOBIT and MGB additives can be used as WMA additives by showing similar values. The pre-cost calculation of these two additives was completed based on the estimated market value of the MGB and the current price of SASOBIT. It has been observed that the MGB as a bituminous mixture, has significant values in terms of cost and performance.

Süleyman Nurullah Adahi Şahin, Metin İpek
Investigations of Electrical Conductivity of Graphite Nano-platelet (GNP)-Taconite Modified Asphalt Binders

This study investigates the electrical conductivity of graphite nano-platelet (GNP)-taconite modified asphalt binders and its application for damage sensing. The GNP-taconite modified asphalt binders are prepared using a high-velocity shear mixer. Different combinations of GNP and taconite are added to the binder, and the electrical conductivity is measured by a four-probe conductivity test. It is shown that the addition of GNP and taconite could effectively enhance the electrical conductivity of asphalt binders. Meanwhile, the results also demonstrate the influence of humidity on the conductivity measurement, which adds a new consideration of applying this material for damage sensing.

Jia-Liang Le, Mihai Marasteanu, Jhenyffer Matias De Oliveira, Mugurel Turos
Laboratory and in Situ Damage Evaluation of Geogrid Used in Asphalt Concrete Pavement

We present in this paper, the damage evaluation of 9 different types of geogrids which have been recovered from laboratory asphalt compacted slabs and in situ test sections of asphalt concrete pavements. After pavement construction, the geogrids have been recovered from different locations on the field sections, and their residual mechanical properties have been evaluated in the laboratory. The same tests have been performed for recovered grids from laboratory compacted slabs. Different compaction processes have been applied for a simulated semi-coarse asphalt concrete made with a petroleum oil to the same hot mixed asphalt which has been used in situ. For the compaction, a wheel tracking device which provides a free rolling and mimics the rubber tired rollers or a compaction damaging device being more representative of on site steel rollers has been used. The tensile strength, stiffness modulus and fatigue strength of each yarn of the grids recovered from test sections have been measured. The main results are that, if the tensile strength is decreased by the compaction process, the stiffness modulus remains practically unaffected and we can observe a clear influence of the grid coating on the tensile strength and modulus. Finally, tensile fatigue tests on recovered warp or filling yarns have been carried out, proving that, even if the grid is damaged during the compaction process, its endurance limit, even if it is decreased compared to virgin warp yarns, remains over the asphalt concrete fatigue limit.

Cyrille Chazallon, Julien Van Rompu, Mai Lan Nguyen, Pierre Hornych, S. Mouhoubi, D. Doligez, L. Brissaud, Y. Le Gal, E. Godard
Laboratory Assessment of Low Temperature Resistance of High Modulus Asphalt Concrete in Relation to Climatic Conditions in Poland

The paper presents the assessment of the properties of high modulus asphalt concrete in low service temperature range. Such an assessment is particularly important due to the climatic conditions of Poland and the problem of the occurrence of thermal cracking in recent years. The scope of laboratory tests included both resistance to low temperature cracking according to TSRST method, but also other methods to characterize its strength properties and behaviour at low temperature. The indirect tensile strength characteristics and the thermal expansion coefficients were investigated. The analysis of the results included both the comparison of different mixtures, as well as the analysis of the probability of occurrence of pavement cracks, taking into account the minimum temperature in the layer defined on the basis of climatic data. Two mixture types were chosen for analysis: conventional asphalt concrete and High Modulus Asphalt Concrete. Either of them contained different bitumen types, including standard pen-grade bitumens, polymer-modified binders (PMB) and so-called highly-modified binders.

Wojciech Bańkowski, Marcin Gajewski, Renata Horodecka, Krzysztof Mirski
Laboratory Comparison of In-Situ, Ex-Situ and Laboratory Produced Foamed Bitumen Stabilized Base

Foamed bitumen stabilisation of granular base course materials is well established as a beneficial technology for the improvement of existing materials and for expedient pavement construction or rehabilitation. Foamed bitumen base (FBB) can be produced in-situ, by a specialised stabilizing train, or ex-situ, in a pugmil. It is most common for existing pavements to be stabilized in-situ while new materials are usually stabilized ex-situ. However, this is not always the case and regardless of the field production method, FBB is usually characterized and designed using material produced in a small laboratory mixer. Consequently, an objective comparison of the three production methods is warranted. This research produced otherwise nominally identical FBB using laboratory, in-situ and ex-situ processes and identified significant differences in the resulting material properties and the achieved modulus. Further research should focus on adjusting laboratory production protocols to ensure that field production conditions are adequately represented by common laboratory mixture design processes.

Thomas Weir, Greg White
Laboratory Evaluation of Rolling Resistance

This paper presents a laboratory test method to characterize the relationship between rolling resistance and macrotexture of road surfaces. Description of the testing (machine, samples, protocol) is provided. Results are comparable to those obtained by instrumented trailers on road surfaces with similar macrotexture. Effects of test speed and temperature are evaluated. Using an analytical model based on the energy dissipated by the rubber when it is deformed by the surface asperities, discussions are made on the importance of rubber hysteresis loss and surface enveloping.

Ebrahim Riahi, Christophe Ropert, Minh-Tan Do
Laboratory Investigation of Permanent Deformation of Modified Asphalt Mixes Using Nanocellulose

Permanent deformation, or rutting, is one of the major distresses associated with flexible pavements. The tendency to use low-performance grade (or softer) asphalt binders to prevent thermal cracking results in severe rutting during the summer (or high temperature) months. Asphalt modification has been identified as one of the methods to improve pavement performance in these temperature extremities. However, prevailing techniques—polymer modification—have resulted in significant cost increase, operational difficulties, incompatibility with the asphalt binder, and poor aging resistance. This research introduces nanotechnology (nanocellulose) as one promising possibility to modify the asphalt binder, or mix, and improve asphalt pavement performance at high pavement service temperatures. Consistent with the Superior Performing Asphalt Pavement (SuperPave) asphalt mixture design and analysis system, the rheology of the modified asphalt binder, as well as the mechanical properties of the modified asphalt mix, were evaluated and the results show that the mechanical properties, including resistance to rutting and moisture susceptibility, can be improved when compared with the unmodified asphalt binder, or mix, at a reduced cost.

Thomas Johnson, Leila Hashemian
Laboratory Performance of Stabilized Base with 100% Reclaimed Asphalt Pavement (RAP) Using Portland Cement, Bitumen Emulsion and Foamed-Bitumen

While substantial research has focused on incorporation of Reclaimed Asphalt Pavement (RAP) in hot-mixed asphalt mixtures, there is a knowledge gap related to performance of stabilized base courses. This study evaluated the laboratory performance of stabilized base courses with 100% RAP and total stabilizing agent amount of 3% (by weight of RAP). Three stabilizing agents (Portland cement, foamed bitumen, and bitumen emulsion) are evaluated individually and in combination (1.5% Portland cement with 1.5% foamed bitumen, and 1.5% Portland cement with 1.5% bitumen emulsion) to determine the optimal stabilization method using laboratory performance tests and pavement design analysis. Performance evaluation was conducted using the resilient modulus (Mr) test to determine the structural contribution and semi-circular bend (SCB) test for cracking resistance. Pavement designs were done using measured Mr values to compare pavement structures with equivalent structural capacity. Semi-circular bend (SCB) test indicates intermediate temperature cracking resistance of materials using various performance indices (fracture energy, fracture strength, flexibility index and rate-dependent cracking index). The use of Portland cement results in considerably higher stiffness and consequently a thinner pavement structure, but with a significant increase in cracking susceptibility. Mixtures stabilized with foamed bitumen tend to be stiffer than those stabilized with bitumen emulsion but have comparable cracking properties.

Chibuike Ogbo, Eshan V. Dave, Jo E. Sias
Large Scale Characterization of Crumb Rubber Modified Asphalt Mixtures Using Dry Process

In Switzerland, every year tons of waste tyres are produced and transported mostly to the cement industry for incineration or exported for further processing. The cement industry receives this waste material (whole tyres) and charges a fee to tyre collectors whereas in many other countries the cement factory pays for the tyres. Waste tyres are a significant global problem. At the same time waste tyres are a source of useful raw materials that are in the country and could be used to enhance the performance of road pavements. It has been shown that crumb rubber from tyres can be used in asphalt concrete as a performance enhancing additive. Many countries mandate its use as an important waste reduction measure. The primary barrier for its use is lack of knowledge by the practicing engineers, as the use of CR requires additional steps in the preparation method. In this paper, we demonstrate that using the dry process it is possible to achieve the required performance. Semi-dense and dense asphalt mixtures modified with crumb rubber were produced in two different asphalt plants. The overall objective of this paper is evaluating selected plant produced mixtures, but in a controlled quasi-laboratory environment, focusing on their mechanical response. A number of compacted slabs in meter scale replicating surface and base layers are loaded with the MMLS3 (simulating traffic loads). The influence of CR on the rutting behaviour was analysed and compared with conventional asphalt mixtures.

Moises Bueno, Lily Poulikakos
LCA of an Asphalt Mixture Produced in a Southern Italian Plant: Analysis and Perspectives

In recent years, a growing attention on environmental issues affecting all fields and procedures of the productive sectors has raised, aiming to reduce energy and raw-material consumptions and pollution effects on environment. Due to the involved volumes and to the nature of the related materials and productive processes, the civil and road sectors have been strongly invested by this change of perspective. Therefore, a proper estimation of the environmental impacts for the entire life cycle of the asphalt mixtures for road construction and maintenance activities is extremely important. For performing similar investigations, Life Cycle Assessment (LCA) has become one of the most reliable and effective methodologies, assuring the possibility to include in a comprehensive analysis all the relevant processes and products, such as raw material extraction, production, use and final recycling. In this paper, a specific LCA analysis, based on the international standards of the ISO 14040 series, of an asphalt mixture is performed, based on primary data, i.e. through data collected or measured directly at a production plant in Sicily. The results, presented in terms of aggregated environmental indicators, are useful for better understanding the overall impact of the productive process, as well as the contribution of its single phases. The results of this research can provide a more reliable and exhaustive analysis on the environmental impacts of an asphalt mixture, assuring a useful numerical reference to producers, contractors and designers that can assume more conscious, informed and sound decisions.

Giuseppe Sollazzo, Sonia Longo, Maurizio Cellura, Clara Celauro
Life Cycle Assessment of Asphalt Pavements Using Crumb Rubber: A Comparative Analysis

Using crumb rubber (CR) as a performance enhancing additive to asphalt mixtures is an increasingly popular method to improve pavement properties and recycle waste tires. However, the ecological benefits/losses of CR asphalt pavements have not yet been assessed in Switzerland. This study investigates the climate change impacts and cumulated energy demand as two indicators of environmental impacts for CR modified wearing courses in Swiss semi dense asphalt pavements. Mechanical tests are conducted to estimate the lifetime of wearing courses. CR comes from the waste tires otherwise incinerated in cement kilns. Life cycle assessment is employed to compare the environmental impacts of scenarios with varying amounts of CR use (from waste tires) in pavements and the current situation of conventional pavements and co-processing of waste tires in cement kilns. Inventory data are collected from previous scientific works, reports, industrial partners and the ecoinvent v3.5 database. The results show that the CR wearing courses have comparable energy demands to conventional pavements, while emitting less greenhouse gases compared to the reference system that is polymer modified. It can be preliminarily concluded that using CR in the SDA wearing course of pavement is a potentially environmentally promising option compared to conventional materials to enhance pavement performance, and it provides a viable option to recycle waste tires in Switzerland.

Zhengyin Piao, Moises Bueno, Peter Mikhailenko, Muhammad Rafiq Kakar, Davide Biondini, Lily Poulikakos, Stefanie Hellweg
Life Cycle Assessment of Self-healing Versus Traditional Maintenance Road Techniques

Self-healing roads are a new generation of pavements whose materials are capable of recovering their original properties after having suffered breakages or failures. This innovative technology aims to reduce the consumption of natural resources and non-renewable energy in the whole life-cycle of roads, due to the potential achievement of increasing their lifespan compared to traditional maintenance operations. Several previous tests have demonstrated the possibility of achieving new asphalt mixtures that could be self-healing by means of microwaves or induction when the pavement reaches deterioration, so the traditional maintenance technique could be postponed. As self-healing technology is still under study, there is a lack of rigorous environmental and economic studies. This study presents the quantification of the advantages and shortcomings of this novel technique when compared to traditional rehabilitation activities, since it is currently one of the priority research lines for paving materials nowadays. Analyses have been done by the application of the Life Cycle Assessment methodology. Results show a clear influence of self-healing in the comparative environmental performance in the majority of the impact categories. In fact, climate change impact could be reduced up to 15%, while the acquisition of extra abiotic materials is reduced by 50%.

Ana M. Rodríguez-Alloza, Daniel Garraín, Juan Gallego, Federico Gulisano
Long-Term Modelling of Composite Pavement Performance

The rehabilitation of rigid (concrete) pavements with the placement of an asphalt overlay is a common maintenance technique which results in a structure known as a flexible composite pavement. The most common form of distress in this type of pavement is reflection cracking which can be due to traffic and/or climatic loading and it is considered as a very complex deterioration mechanism. A simplified mechanics-based approach identified from the literature has been developed to model the progression of reflective cracking. To demonstrate the model, results have been compared with data from the Long-Term Pavement Performance (LTPP) database, which contains performance and traffic data from monitored in-service road sections in North America. Results reveal the development of reflective cracking at different periods after the placement of the asphalt overlay and with different rates of cracking depending on the structure and material properties of a section as well as the specific traffic axle loading of each pavement section. The results help in identifying those factors which have a greater influence on the progression of reflection cracking in flexible composite pavements.

Evangelia Manola, Nick Thom, Andy Collop
Mechanical Assessment of Recycled Bituminous Mixtures

Bituminous mixtures have a key attribute that they can be 100% recycled without downgrading its functionality. This represents the highest value application and has significant economic and environmental benefits. Every year billions of euros are spent on road construction and maintenance globally. These operations produce a considerable amount of reclaimed asphalt pavement (RAP), which is a valuable waste. Its re-use reduces the depletion of quality resources in landfilled. RAP recycling is a step forward in the direction of sustainable approaches as defended by the recent policies yearns. RAP incorporation in new bituminous mixtures can be associated with different techniques, rejuvenators and additives. This incorporation represents the first cycle of the material’s life. The circular economy presupposes that materials have several cycles during them life. Therefore, the multi-recycle capacity of the bituminous mixtures needs to be evaluated. The main objective of the paper is to analyze the short- and long- term mechanical capacity of RAP in new bituminous mixtures. For that, a laboratory study involving a surface dense bituminous mixture will be described. One RAP incorporation percentage was evaluated (25%) and to take advantage of the binder properties a commercial vegetable rejuvenator was used. The long-term oven ageing protocol was used to simulate the in-service ageing. The stiffness modulus, resistance to fatigue, water sensitivity and permanent deformation resistance were assessed for different compositions. The study showed that bituminous mixtures have potential to be recycled due to the results obtained even in terms of long-term performance. Test results confirmed that recycled bituminous mixtures had at least an equivalent performance over the primary material.

Vítor Antunes, José Neves, Ana Cristina Freire
Mechanical Behavior of Asphalt Mixtures Applied in Field in the Southern Brazil

This work aimed to comprehensively verify the behavior against permanent deformation and fatigue in order to obtain an overview of the situation of field mixtures in Rio Grande do Sul, state in south of Brazil. In this way, the study proposes evaluate eleven mixtures used in the field. These mixtures consist of different mineralogical aggregates, different nominal sizes, different granulometric compositions and asphalt binders. The linear viscoelastic characterization (LVE) behavior, the resistance to permanent deformation, and to fatigue was evaluated for establish a global classification against the two main defects in asphalt concrete pavements. The results show differences in LVE behavior. The Flow Number showed that the Polymer Modified Binder (PMB) and TLA modified asphalt have greater resistance to permanent deformation, whereas mixtures with conventional 50/70 penetration binder showing worse results. As for fatigue, mixtures with PMB and rubber asphalt show significantly better results than mixtures with 50/70 binder and TLA modified asphalt.

Silvio Schuster, Cléber Faccin, Fernando D. Boeira, Luciano Pivoto Specht, Deividi da Silva Pereira
Mechanical Properties of Bitumen and Asphalt Mixture Modified with Polymer Additives

This paper presents an investigation into the mechanical properties of bitumen and asphalt mixture modified with polymer additives. Two polymer additives used in the study are SBS (Styrene-Butadiene-Styrene) and EVA (Ethylene-Vinyl Acetate). Penetration test, softening point test and elastic recovery test were performed on the base bitumen and the SBS polymer modified bitumen with different additive contents. In addition, the complex modulus tests were conducted in order to characterize the linear viscoelastic behaviour of the base bitumen, SBS polymer modified bitumen and the EVA modified asphalt mixture. The experimental results showed that the polymer modification improved the hardness and the elastic recovery of bitumen. The extent of the improvements varied as a function of polymer content. The changes in the complex modulus (both norm and phase angle) of polymer modified bitumen and asphalt mixture were observed. The Time Temperature Superposition Principle (TTSP) was shown to be applicable for the complex modulus of the base bitumen. But the polymer modified bitumen and asphalt mixture respected only the Partial Time-Temperature Superposition Principle (PTTSP). The PTTSP was also verified for the complex Poisson’s ratio of an EVA modified asphalt mixture. Despite the changes in the rheological properties, the shift factors used to build the complex modulus master curves of both original and polymer modified bitumen were very similar.

Quang Tuan Nguyen, Thi Thanh Nhan Hoang, Xuan Cay Bui, Van Cham La, Thi Kim Dang Tran, Quang Phuc Nguyen, Nhu Hai Nguyen
Methodology for Evaluating the Performance of Bituminous Binders Based on Rheological Indicators: Impact of the Use of a Rejuvenator

In order to increase further the recycling rates of reclaimed asphalt (RA) while maintaining performance, road contractors use more and more additives called rejuvenators. The desired effects include a regeneration of the aged RA binder properties and an improvement of the asphalt mixture performance containing a high RA content. At present, no standardized procedure applicable to a bituminous binder exists to evaluate the impact of different commercial rejuvenators. Therefore, within the framework of the Re-RACE (Rejuvenation of Reclaimed Asphalt in a Circular Economy) research project, the Belgian Road Research Centre aims to develop a screening procedure in order to evaluate the effectiveness of additives to rejuvenate bituminous binders from rheological indicators. To establish an appropriate selection, each indicator is evaluated on its representativity in terms of asphalt mixture performance (cracking, rutting …), on its precision, on its sensitivity to ageing and on its potential correlations with the other indicators. To support this study, rheological measurements were performed on a 50/70 grade bitumen at different ageing stages and two bituminous blends of fresh and long-term aged bitumen with or without rejuvenator corresponding to 70% RA. This article presents the results related to rheological indicators evaluating the risk of cracking at intermediate temperature. This investigation is part of a broader methodology to assess the performance of bituminous binders and will provide in the future a screening procedure for evaluating the effect of rejuvenators while using high RA rates.

Nathalie Piérard, Stefan Vansteenkiste, Ann Vanelstraete, Philippe Peaureaux
Microwave Crack-Healing Capability on Asphalt Mixtures with Silicon Carbide

The application of microwave radiation is an effective technique to promote the crack-healing of asphalt mixtures. The heat increases the bitumen temperature and reduces bitumen viscosity, flowing and sealing the open cracks. Normally, these types of asphalt mixtures contain metal additives that promote microwave heating. However, the literature reports different materials heat efficiently with microwave radiation. Silicon Carbide (SiC) is a semiconductor ceramic and low-cost material, like an aggregate, with good dielectric properties that efficiently absorb microwave radiation and release the absorbed energy in the form of heat. This article reports the study of the efficacy of SiC as a potential additive for asphalt mixtures to promote asphalt crack-healing. Asphalt mixtures with constant SiC content and SiC uniform particle size of #12 (1.68 mm), #120 (0.125 mm), and #1200 (0.038 mm) were prepared. For the measurement of the crack-healing, the authors conducted three-point bending tests on semi-circular samples. Results showed that some mixtures increased the healing with the number of healing cycles; which is the opposite trend of results reported in the literature. Additionally, the healing of asphalt mixtures with #12 and #120 was higher than for #1200 SiC mixtures. Overall, the study indicates that asphalt mixtures with SiC can be crack-healed by microwave radiation.

Alvaro González, Jonathan Valderrama, José Norambuena-Contreras
Modeling of T/C Complex Stiffness Modulus Test and Non-linearity of Asphalt Concrete Mixes

The work described in this article is part of the French national project ANR MoveDVDC. One of the objectives of this project is to evaluate the influence of aging and damage of asphalt concrete materials on the lifetime of road pavements. In this context, modeling the behavior of aged or not asphalt mixes in fatigue is planned. At the moment, the first researches focused on the development of a phenomenological model reflecting the viscoelastic nature of asphalt mixtures to facilitate numerical modeling of structures. With this objective and relying on experimental T/C complex stiffness modulus test data, a viscoelastic non-linear model with variable parameters, abbreviated “VENoL model”, was developed in frequency domain. It consists of two elements in parallel, which represent the real and imaginary parts of the complex stiffness modulus, such that their respective parameters named $$R_{E}$$ R E and $$I_{\eta }$$ I η vary according to temperature, pulsation and amplitude (for non-linearity) of sinusoidal loading. To allow a numerical implementation, $$R_{E}$$ R E and $$I_{\eta }$$ I η follow a Carreau-Yasuda law as a function of the reduced pulsation, associating the effects of temperature and pulsation. In homogeneous conditions, this model can reproduce T/C complex stiffness modulus tests on cylindrical specimens. The future work will consist in evolving this model to use it with Discrete Element Method (DEM) and in time domain.

Léo Coulon, Georg Koval, Cyrille Chazallon, Jean-Noël Roux
Modeling of T/C Fatigue Test with Boundary Element Method and Linear Fracture Mechanics

This work presents the simulation of 3D crack propagation in samples in order to determine fatigue life. The modellings have been achieved by using MBEMv3.0: a fast software based on the Symmetric Galerkin Boundary Element Method (SGBEM) accelerated with the Fast Multipole Method (FMM) in 3D elasticity. Fatigue crack propagation has been simulated with Paris law. We present the simulations of a tensile/compression fatigue test on cylindrical samples of a semi-coarse asphalt concrete considered as homogeneous, containing very small cracks. When the number of cycles increases, the cracks propagate, and we can observe a loss of rigidity of the sample. Parametric studies of the modelling parameters have been performed where the damage evolutions exhibit a typical shape that proves that, for asphalt concrete materials subjected to T/C fatigue test, the shape of the fatigue test curve is mainly governed by biasing effects at the beginning then by mechanical damage at the end.

A. Dansou, S. Mouhoubi, Cyrille Chazallon, M. Bonnet
Modelling of Oxidative Ageing in Bitumen Using Thermodynamics of Irreversible Processes (TIP): Potential and Challenges

Diffusion-reaction models derived within the frame of thermodynamics of irreversible processes (TIP) for mixtures enjoy a number of advantages over purely phenomenological models. Potential and challenges of the TIP approach are discussed exemplary by means of a particular model focusing on spurt oxidation in bitumen. More specifically, film ageing experiments are simulated considering different bitumen compositions in terms of SARA fractions. The saturation times predicted for different compositions are contrasted, for instance, with initial asphaltene content and Gaestel index. The model predicts a decrease in saturation time for increasing asphaltene content, which is in line with experimental results.

Uwe Mühlich, Georgios Pipintakos, Christos Tsakalidis
Monitoring of Railway Structures of High-Speed Line Bretagne-Pays de la Loire with Bituminous and Granular Sublayers

Tamping and ballast wear, due to dynamic stresses, lead to frequent and costly maintenance operations. To mitigate this problem, an innovative track structure with an asphalt concrete layer under the ballast was built on the Bretagne-Pays de la Loire High-Speed Line (BPL HSL). It is intended, among other things, to reduce the amplitude of the accelerations produced at the passage of High-Speed Trains (HST), which are a major cause of ballast settlements. BPL HSL includes 105 km of asphalt concrete sub-layer under the ballast and 77 km of granular sub-layer. In order to study the dynamic responses of these different structures, four track sections were instrumented using, among others, accelerometers, strain gauges and temperature probes. In this paper, we present the track instrumentation, the acquisition system installed to collect all the measurements, and the comparative results of dynamic and mechanical behavior between structures since July 2017, when the BPL HSL was opened to commercial traffic.

Diana Khairallah, Juliette Blanc, Pierre Hornych, Louis-Marie Cottineau, Olivier Chupin, Jean-Michel Piau, Diego Ramirez Cardona, Alain Ducreau, Frederic Savin
Monitoring Stiffness Evolution of Asphalt Concrete Through Modal Analysis

The stiffness of asphalt concrete, which is used for thickness design of pavements, is known to increase with time due to age hardening of the binder. Therefore, aging models to account for the stiffness evolution over time are in some applications considered with the aim to improve pavement life predictions. Modal analysis is an economic test method with a verified precision for characterizing the complex moduli of asphalt concrete. In this paper, the stiffness evolution of asphalt concrete has been monitored through modal analysis. The simplicity of the modal test set-up facilitates accurate repeated testing under identical conditions. Therefore, modal testing was performed repeatedly at the temperatures of 20 and −20 °C over a period up to around 300 days. The testing was performed on samples in a controlled laboratory environment and does not intend to provide a measure of the age hardening of real pavements. The aim of this paper is to characterize the stiffness evolution of asphalt mixes with modified and unmodified binders in a controlled environment. Cyclic indirect tensile tests were performed in addition to modal analysis to characterize the stiffness evolution under different loading configurations. Results from the modal analysis clearly showed that the rate of the stiffness evolution is initially slower for the modified binder in comparison to the unmodified binder.

Anders Gudmarsson, Abubeker Ahmed
Multi-criteria Framework to Evaluate the Oxidative Aging Resistance of Bitumen Binders

A multi-criteria framework, using both traditional and specially-designed long-term aging protocols, were utilized in order to discriminate binder formulations with respect to aging resistance due to oxidation. Two protocols were explored: a more traditional type of extended PAV under standard temperature and pressure conditions for durations up to 72 h, and an ambient pressure precision oven test developed by the Western Research Institute (WRI) under work with the Federal Highway Administration (FHWA). This second protocol ages 100 µm thick films at 70 °C for durations up to 84 days. By utilizing thin films, various complications due to oxygen diffusion effects are nearly eliminated. The methodology uses several indicators from infrared spectroscopy and rheology to fit an advanced oxidation kinetics model, also developed by WRI with the FHWA. This oxidation model allows determination of rate constants for the first (fast) and secondary (slow/constant) reactions, and also the amount of reactive material in bitumen. In this study, the overall aging resistance methodology relied heavily on changes in rheological behavior on the whole bitumen temperature range. Special emphasis was put on the mid- to low-temperature rheology, to determine if the modifiers reduce the non-load related surface cracking potential through the determination of various rheological aging sensitive parameters including ΔTc, the rheological index (R), Black space parameters and crossover frequency and temperature. Overall, the impact of binder formulation on oxidative ageing resistance was clearly observed and confirmed through this multi-criteria approach which allowed clear discrimination between various formulations and the efficiency of modification with respect to given oxidation indicators. Results showed that it was possible to differentiate between additives that chemically retard oxidation from additives that merely act to soften the bitumen.

Jeramie J. Adams, Michael D. Elwardany, Jean-Pascal Planche, Yvong Hung, Jeanne Zhu, Soenke Schroeder, Mouhamad Mouazen
Multiphysics Simulation and Validation of Field Ageing of Asphalt Pavements

Long-term field ageing of asphalt pavement plays a vital role in limiting the pavements’ service life. Models have been established to represent the multiple physics that contribute to the ageing of asphalt pavement, including: (1) heat transfer to determine pavement temperature profile, (2) diffusion of oxygen from the air into the connected air voids of the asphalt pavement, (3) diffusion of oxygen from the air void channels to the inside of the asphalt mastic coating films, and (4) the growth of oxidation products in the asphalt binders. These four ageing-related physics were mathematically modelled individually in the literature; however, they were not effectively integrated and coupled into a comprehensive computational model. The challenge lies in that the ageing-related physics are circularly dependent and time-dependent. Another challenge results from the complexity in numerical modelling of the high nonlinearity caused by the circular dependency between the four physics. This study uses weak-form partial differential equation (PDE)-based finite element (FE) program to efficiently couple the physics into one integrated model. The model inputs include the available site-specific hourly weather data, binder oxidation kinetics, mixture design properties, and thermal characteristics of pavement materials. The model was validated using the field measurements of the oxidation products (carbonyl) from The Federal Highway Administration (FHWA) reports. Results show that the model can effectively address the circular dependency between the ageing-related multiphysics and reliably predict the oxidation products along pavement depth for asphalt pavement road section.

Eman Omairey, Yuqing Zhang
Multiscale Analysis of Pavement Texture—Effect on Skid Resistance

The surface properties (skid resistance, rolling noise and rolling resistance) of the road are closely related to the surface texture. Several scales of texture intervene in the interaction between a tire and the road pavement. However, the influence of each scale on these properties is little or not known. During lifetime, the texture of road evolves under the wear induced by road traffic (polishing) and climate changes. This texture change affects pavement surface performances. This paper presents a laboratory study, which aims at developing a multiscale approach to identify the relevant texture scales, which can explain skid resistance values. For multiscale decomposition, a wavelet-based multiscale analysis method is selected owing to its flexible time-frequency resolution. After comparing several functions, the Morlet wavelet is used. Then, laboratory tests are performed on various bituminous mixtures. Polishing tests are done with Wehner & Schulze machine to assess skid resistance evolution under traffic and 3D-cartographies of the surface are realized at different stages of polishing to assess surface texture evolution.

Wiyao Edjeou, Veronique Cerezo, Hassan Zahouani, Ferdinando Salvatore
Multi-scale Evaluation of Asphalt Binders Containing Different Proportions of Reclaimed Asphalt Pavement (RAP)

This study aimed to evaluate the nano-mechanical properties of RAP blended binders and investigate their relationship with the bulk (macro-scale) properties. The tests were conducted on asphalt binders with different RAP contents (0, 15, 25, 35, 100% RAP). In the nanoindentation test, a trapezoidal loading waveform was applied using the Berkovich tip. The indentation depths during loading, holding and unloading were analyzed using a linear viscoelastic model. Consequently, the storage and loss viscoelastic moduli were determined and compared with those obtained at the macro-scale using the dynamic shear rheometer. With the addition of RAP content, the macro-scale modulus increased at a faster rate than the nano-scale modulus. The paper recommends an approach for studying the interaction between RAP and virgin binders using the nanoindentation method. This approach is valuable to determine the optimum amount of RAP that can be used in a mixture without adversely affecting its fracture resistance.

K. Lakshmi Roja, Bhaskar Vajipeyajula, Eyad Masad
Novel Modified Recycled Mastic for Demanding and Sustainable Asphalt Mixtures

New recycled mastic asphalt is been under development, highly modified, for use in asphalt mixture with a strong effect in its properties related with pavement performance. That mastic incorporates different products (among which are industrial by-products) that enhance/improve mechanical performance of the asphalt mixture, namely by: increasing the binder/aggregate affinity; reducing new added binder’ oxidation; increasing binder’ cohesion (ductility strength); improving permanent deformation resistance and increasing fatigue life. At the same time, it reduces the consumption of new added binder (up to 3% less than the usual 5–6%) and does not require the addition of any filler or fine aggregates (#  0/2 mm). Finally, the new mastic asphalt reduces the temperature required during compaction of asphalt mixture and offers a contribution to the circular economy framework, not reducing its mechanical performance and almost without increasing the final construction cost.

Fernando C. G. Martinho, Luís G. Picado Santos, Francisco M. Silva Lemos
Numerical Simulation of Two-Point and Four-Point Bending Fatigue Tests on Asphalt Mix Using Intrinsic Material Parameters Calibrated from Digital Image Correlation Data

According to current interpretations, fatigue properties of asphalt mixes vary depending on the type of test performed. The aim of this work is therefore to model and simulate numerically different fatigue tests using intrinsic material parameters. The modeling of the fatigue tests proposed in this work is based on linear elastic fracture mechanics and the Paris law. This modeling is used to simulate four-point bending (4PB) and two-point bending (2PB) fatigue tests performed on the same asphalt mix using similar values of the model parameters. The results obtained are satisfying and attest that the same set of parameter values would be able to predict the mechanical response of different tests. 2PB fatigue tests are then carried out on a sand asphalt with digital images acquisition. The images recorded are processed by Digital Image Correlation (DIC) to provide the displacement and strain fields in the material as well as the crack paths. These are found not systematically identical for different samples of the same material undergoing similar test conditions because of heterogeneity of the material at local scale. The 2PB fatigue tests are then numerically simulated considering the crack paths determined from the DIC data. The results show that the scatter of the fatigue curves can be explained in part by the difference in crack path observed for the different samples.

Ibishola Santos, Paul Marsac, Olivier Chupin, Ferhat Hammoum
On the Assessment and Optimisation of the Processing Conditions of Tyre-Rubber Modified Bitumen

The current study aims at understanding the effect of the variables associated with manufacturing rubberised bitumens in order to develop rubberised bitumen with superior mechanical properties and identify optimised processing conditions for its production. The experimental work covered extensive laboratory testing of several rubberised bitumen blends. The rubberised bitumen was manufactured using four paving grade bitumens (180/240, 160/220, 70/100, 80/100), three tyre rubber types (mechanical ground, waterjet powder, ambient ground powder), and various processing conditions (shear levels, temperatures, processing times). Characterisation of the manufactured blends included rotational viscosity, softening point, and Fraass breaking point. The findings derived from the experimental programme relate to optimised processing conditions for the tyre rubber blends. Overall, this research showed that simple, relatively quick, and inexpensive test methods can be used for comprehensive characterisation of recycled tyre rubber blends. Similarly, it was found that the properties of rubberised bitumen were highly factor dependent, including effects of the: source of base bitumen (physicochemical properties), source of rubber particles, and processing conditions (shear mixing, temperature, and time). The impact of rubber pre-treatment on the performance was found to be negligible for the studied combinations. Clear bitumen-specific effects were observed from the soft and hard bitumen types considered. Furthermore, temperature and shear processing conditions had the paramount effects on the level of bitumen modification. Optimised conditions for rubberised bitumen production suggested a range of temperature of 180–210 °C, up to 180 min for high shear, and up to 30 min for ultra-high shear.

Juan S. Carvajal-Munoz, Ayad Subhy, Davide Lo Presti
Organic Compounds Evaluation from Fumes Generated in Laboratory by Bio-recycled Asphalt Mixtures

Using bio-binder and bio-additives as recycling agents for asphalt mixtures with high-content of reclaimed asphalt (RA) is proving to be feasible. It is still not clear whether this combination might provide new hazardous emissions from airborne binder fumes. The health hazard related to airborne bitumen fume generation is primarily relevant for paving crews while there is little opportunity for exposure related to asphalt plant workers. In this study, measurements of gaseous organic compounds from airborne binder fumes of selected bio-asphalt mixtures have been measured during the laboratory mixing process, by using a thermo-mixer equipped with a chimney at Univ Gustave Eiffel. Parameters studied are the binder nature, mix formula and mixing temperatures. Results show that generally combining bio-binders and RA is as safe as using conventional bitumen and RA, however thanks to this approach it was possible to identify a strong link between bituminous material composition and their emission potential.

Vincent Gaudefroy, Davide Lo Presti, Laurent Porot, Simon Pouget, Jean-Pascal Planche, Chris Williams, Emmanuel Chailleux
Parametric Study of Binder Properties on Thermomechanical Performance of Bituminous Mixtures

This paper aims at understanding the influence of several binder properties on various mixture performances through a parametric approach. Hot-Mix Asphalts with varying binder origin, with or without polymer modification and with different binder content for a given porphyry aggregate were studied in a full factorial plan. Thermomechanical performance of all mixtures were tested with French method: Stiffness (2-Point Bending apparatus, 2-PB), Fatigue resistance (2-PB), Water sensitivity (Indirect Tensile Stress Ratio, ITSR). A statistical regression including cross effects between parameters was made. The potential biasing influence of air void content scattering has been limited. Bitumen origin and binder content are the main parameters influencing complex modulus results. The parametric study shows that fatigue performances are influenced by all three parameters with very limited cross effects. High ITSR values seem correlated with good fatigue performance in this study, and ITSR is mostly influenced by binder origin and polymer modification, but with important cross effects.

Gabriel Orozco, Cédric Sauzéat, Hervé Di Benedetto, Simon Pouget, Stéphane Dupriet, Simon Baudouin
Pavement Evaluation Method Using MMS

In recent years, 3D point clouds have become utilized to grasp objects shapes in the civil engineering field. Each 3D point cloud has an accurate 3D coordinate, thus, the shape of object can be obtained in 3D.Therefore, we paid much interest in 3D point cloud data, because it is able to capture road pavement conditions comprehensively, and then we have developed the pavement evaluation method using MMS. This method has made the automatic detection possible by spatial frequency analysis of 3D point cloud data acquired by laser scanners mounted on MMS. Thus, we detect; rutting and flatness (IRI) and places of local damages like potholes. In addition, the method also has made it possible to detect cracks automatically by AI technology with high resolution images acquired by line sensor cameras mounted on MMS. Useful results also can be obtained by loading road pavement condition surveys data into the system based on the method, such as replacement targets by visible coloring and calculate replacement cost.

Hinari Kawamura, Yoshifumi Nagata, Tomoaki Tokuno, Tetsuya Ishida, Tsukasa Mizutani, Junko Yamashita
Performance Testing of Hot Mix Asphalt Containing Biochar

In recent years, researchers have been able to identify asphalt binder additives such as polymers and bio-binder that can enhance the rheological and mechanical properties of asphalt binders. Utilizing Bio-binder as a partial replacement for asphalt binder was shown to be promising in both mechanical and sustainability aspects. Biochar which is a byproduct of producing bio-binder has shown similar results on asphalt binder. Cracking is one of the major distresses occurring in asphalt pavements. Researchers and practitioners have employed different test methods to characterize the fracture properties of Asphalt. The Semi-Circular bending test (SCB) proved to be a suitable test method to analyze the fracture properties of asphalt mixtures. This study focused on adding Rubber and Biochar to the asphalt mixtures to analyze their effect on fracture resistance; individually, combined, and the effect of aging them. The results suggested that the effect of adding Biochar evidently helped attain higher strain energy values after aging.

Shadi Saadeh, Yazan Alzubi, Basel Zaatarah, Ellie H. Fini, Pritam Katawal
Predicting the Master Curve of Bituminous Mastics with Micromechanical Modelling

The performance of asphalt mixtures is significantly affected by the viscoelastic properties of their mastic phase. The analytical approaches used to predict the mastic’s properties from its composition and constituents are limited in their accuracy as well as potential to handle non-linear material behaviour. An alternative micromechanical finite element modelling approach to calculate the mastic’s master curve from the binder and filler phase properties is presented in this paper. In the model, the mastic’s representative volume element is generated and it consists of a linear viscoelastic bitumen matrix and elastic spherical filler particles. In order to validate the model, shear relaxation moduli of bitumen and bitumen-filler mastics are measured at temperatures between −10 to 80 °C. For the two mastic materials characterized experimentally, micromechanical models are set-up and their capability to capture the measured response is evaluated and compared with the existing analytical solutions. The obtained results indicate that the proposed finite element modelling approach is advantageous as compared to the analytical solutions, as it both allows predicting mastic’s properties over wider temperature, frequency and material range as well as results in a better agreement with the measurements.

Hassan Fadil, Denis Jelagin, Manfred N. Partl
Predicting the Potential Impact of Geopolymers on the Creep Recovery Properties of Asphalt Binder

Asphalt binder is the world’s most commonly used pavement materials. However, it is produced through complex industrial process that contributes to global pollution and escalates climate change. Production of polymer-modified asphalt is associated with lower CO2 emissions compared to production of virgin asphalt binders. Moreover, it can enhance asphalt mixture performance and extend the pavement service life. This study aimed to investigate the potential usage of geopolymers based on by-product material such as fly ash to enhance the high-temperature performance of asphalt binders. An experimental matrix of laboratory testing was conducted to study the properties of the PG 58–28 asphalt binder; with different percentages of geopolymer-based on fly ash (GF), 4, 8, and 12%. Frequency sweeps test and Multiple Stress Creep Recovery (MSCR) test was conducted using the Dynamic Shear Rheometer (DSR). The results indicated that the geopolymer modified asphalt binder has significant effects on performance grading, traffic level, and recovered strain. Moreover, modified asphalt binder with 8% of GF has a good rutting resistance compared with 4 and 12% of geopolymer, at low and high-stress levels.

Abdulrahman Hamid, Hassan Baaj, Mohab El-Hakim
Prediction of Fatigue Behaviour of Asphalt Mix from Tests on Asphalt Mastic

With the introduction of the EN 13108-xx in 2008, it became possible to use performance-based test methods for the assessment of asphalt mixtures also in contracts. There are various test methods for addressing the performance characteristics of asphalt mixtures (i.e. low temperature cracking resistance, stiffness, resistance to fatigue and to permanent deformation). They are specified in the EN 12697-xx. However, these rather complex test methods require a large test effort compared to empirical tests; in the special case of fatigue tests, a substantial amount of material and time for specimen preparation is needed. Therefore, it is the main goal of an on-going research project to assess fatigue resistance on the mastic level by Dynamic Shear Rheometer (DSR), since mastic is the relevant binding component in asphalt mixtures. In this research, asphalt mixes with ten different types of bitumens and three different types of aggregates were produced and tested for fatigue on the four-point bending beam (4PB). The mastic components of each asphalt were mixed and tested for fatigue in the DSR. The results and analyses show a good correlation between the fatigue tests on both levels. With the shear stress level for 106 fatigue load cycles and the initial stiffness on mastic level, the strain level at 106 fatigue load cycles (ε6) for the respective asphalt mix can be assessed with a very small deviation.

Michael Steineder, Valentin Donev, Lukas Eberhardsteiner, Bernhard Hofko
Preliminary Investigation of Using Nanocellulose in Bituminous Materials

In Canada, the three most costly modes of pavement distresses are thermal cracking, fatigue cracking, and permanent deformation. The unpredictable increase in heavy-vehicle traffic and extreme fluctuations in temperature play a major role in the acceleration of pavement deterioration. Numerous studies on innovative bitumen modification have been carried out in order to improve pavement performance. Some of these studies have focused on using nanomaterials to modify bitumen to mitigate deterioration and to extend pavement service life. Cellulose is a green material that has been successfully used for concrete reinforcement due to its excellent mechanical properties and biocompatibility. Therefore, Nano-crystalline cellulose (CNC) is being evaluated as a bitumen modifier in the present study. The Dynamic Shear Rheometer test (DSR) is used to determine the rheological properties of the bitumen based on the Superpave system. The preliminary results of the investigation into using nanocellulose as a bitumen modifier, demonstrate that nanocellulose has a moderate impact on the rheological properties of bitumen, especially at high temperatures. Moreover, the nanocellulose concentration increases the complex modulus which can help with permanent deformation resistance. Nevertheless, the results support the need for further testing of the modified mixtures in order to have a better understanding of the impact of nanocellulose on the performance of bituminous mixes.

Ali Qabur, Hui Liao, Dandi Zhao, Hassan Baaj
Properties at Low Temperatures of Warm Mix Containing High Content of Multi-recycled RAP

Within the framework of the French national project “Innovation for Materials and Processes for Improving the Multi-Recycling of Mixtures” (IMPROVMURE), founded by the French National Research Agency (ANR), a research work including an experimental campaign on the thermomechanical behaviour of bituminous materials at low temperatures was performed. Three types of bituminous mixtures were produced following a warm process with foamed bitumen. The first mixture contained 0% Reclaimed Asphalt Pavement (RAP). The second mixture contained 70% RAP coming from milling. A third mixture was prepared, containing 70% of the second mixture aged artificially in the lab. Therefore, the fourth mixture was made of 70% of the third mixture subjected to the same aging process. Thermal Stress Restrained Specimen Test (TSRST) on the three bituminous mixtures were performed on cylindrical samples at the University of Lyon/ENTPE. The failure temperature (TF) and failure stress (σF) were used to compare the behaviour of mixtures at low temperature. Influence of RAP content and air void content was studied. The air void content showed an effect inversely proportional to the failure stress.

A. Pedraza, Hervé Di Benedetto, Cédric Sauzéat, Simon Pouget
Proposal for Aging Quantity Model for Estimating Binder Aging Level of HMA Mix

This study investigated for the aging quantity (AQ) modeling of asphalt in the mixes after various short-term aging (SA) treatments. AQ was defined as a mediator of SA level of binder in HMA mix as a function of temperature (T) and time (t) when the material source was limited. Three loose HMA mixes were aged artificially at two temperatures for four-time lengths: 160 and 180 °C for 1, 2, 4 and 8 h. The best-fit mathematical model was selected using exponential function to quantify the SA by T and t for an AQ model for predicting absolute viscosity (AV). It was found that the R2 between measured AV and estimated AV (EAV) by AQ was over 0.95. Therefore, it was concluded that the AQ, which was quantified by T and t, was possible to use to estimate AV of asphalt in HMA mixes under various SA.

Sungun Kim, Kyongae Ahn, Kwang W. Kim
Quantification of Compactability of Bituminous Mixtures with Different Aggregate Gradations Using Superpave Gyratory Compactor and Shear Box Compactor

Bituminous mixtures offer varying compactive resistance due to gradation, binder type, its content, and temperature. Most of the attempts to quantify laboratory-scale compaction resistance have used Superpave Gyratory Compactor (SGC). However, SGC has criticism related to poor spatial uniformity of air voids, whereas the Shear Box Compactor (SBC) is reported to have less spatial variation in air voids. The focus of this study is to investigate and document the sensitivity of SGC and SBC on the variation in aggregate gradation during compaction. In this work, two aggregate gradations designed based on particle packing theory for achieving optimum packing, and a control sample with Bituminous Concrete mid-gradation as per the current Indian Specifications are used. Compaction curves obtained from both the compactors are analyzed in terms of various compaction indices and their correlation to laboratory rutting performance is investigated. It is identified that certain indices of SGC and SBC are sensitive to the rutting performance of the mixtures prepared with different aggregate gradation.

V. T. Thushara, J. Murali Krishnan
Reduction of Bitumen Content and Production Temperature of Hot-Mix Asphalt Incorporating RAP Using Dune Sand and Lime

Using Reclaimed Asphalt Pavement RAP allows monetary savings with reduction of the quantity of greenhouse gases and consumption of natural resources (aggregates and bitumen). Dune sand is an abundant material in many worldwide regions. Due to its mineralogical composition and fineness, it has many interesting mechanical characteristics. In addition, lime has been increasingly used in asphalt mix formulations because it contributes in resisting rutting and aging problems of asphalt mixes by limiting the oxidation of bitumen. The paper discusses the effects of incorporating dune sand and lime on the bitumen content and production temperature of bituminous mixtures incorporating (RAP). The main objective is to increase the (RAP) rate to increase the level of the cited benefits. Different percentages of RAP (10–50%), dune sand (5–10%) and lime (0.5–1%) were evaluated. Mixtures’ gradations have been carefully studied in order to respect existing specifications. Results showed that the addition of 10% dune sand reduces the bitumen content by 0.3%. The addition of lime has improved the binder/aggregates adhesion, while the gain in bitumen content and mechanical performances were established. The addition of dune sand and lime have reduced the production temperature to approach that used when manufacturing warm-mix asphalt. The complex modulus tests, carried out at different temperatures and frequencies, have shown that the new formulated mixes perform better than conventional mixtures.

Jamel Neji, Ahmed Siala, Saloua El Euch Khay, Amara Loulizi
Relationship Between Fatigue Damage of Asphalt Binders and Corresponding Mixtures

The performance of asphalt mixtures is affected by different factors, the type of binder being an important one. Mixture and binder behave as linear viscoelastic (LVE) materials when subjected to small strain and a small number of loading cycles. However, when the number of cycles is greatly increased, fatigue damage accumulates. In the linear domain, for the characterization of such materials, complex modulus is evaluated, and its change in fatigue tests may be used as an indicator of fatigue damage evolution. With damage growth, one of the major distresses in pavements appears: fatigue cracking. The loss of stiffness occurs as damage accumulates with the eventual coalescence of macrocracks. The objective of this work is to relate fatigue damage properties of asphalt binders and the corresponding asphalt mixtures. The materials used in the research are: three binders and their corresponding asphalt mixtures, considering the same aggregate skeleton. The results suggest that fatigue damage in the binders presents good correlation with fatigue damage in the corresponding mixtures.

Letícia S. de Oliveira, Jorge L. O. Lucas Júnior, Lucas F. A. L. Babadopulos, Jorge B. Soares
Relationship Between Linear Viscoelastic Properties of Asphalt Binders and Corresponding Mixtures

Many factors affect asphalt mixtures performance, such as aggregates and binder type. Both binder and mixture have linear viscoelastic (LVE) behavior under small strain and small loading cycles number. For the characterization of the LVE behavior of such materials, complex modulus measurements can be used (sinusoidal loading tests). The LVE properties depend on time and temperature. The 2S2P1D (two springs, two parabolic elements, 1 dashpot) rheological model is capable of representing the complex modulus of asphalt materials at different scales (from binders to mixtures). The SHStS (Shift-Homothety-Shift in Time-Shift) method experimentally describes the relationship between the behavior of different scales of asphalt materials, and can be used in association with the 2S2P1D model. The objective of this work is to demonstrate the relationship between the LVE properties of binders and mixtures. The materials used in the research are: three binders and their corresponding asphalt mixtures, considering the same aggregate skeleton. The 2S2P1D model proved to be satisfactory for the modeling of the tested mixtures and binders. Out of the nine constants of the 2S2P1D model and WLF Equation fitted to the binder complex modulus results, six could be maintained for their respective mixtures. The variation of the other constants is well described by the SHStS transformation, which appears as a useful approach to obtain mixture behavior from binder behavior. By using the referred modeling approach, it was possible to relate the LVE behavior of mixtures and binders.

Letícia S. de Oliveira, Lucas S. V. da Silva, Lucas F. A. L. Babadopulos, Jorge B. Soares
Relaxation Spectrum: Why It Matters and How to Correctly Develop One?

One of popular models to describe mechanical behavior of asphalt binder is the Generalized Maxwell Model (GMM), which is analogized as a large number of springs and dashpots connected in a parallel fashion. Theoretically, the continuous relaxation spectrum of GMM of a particular asphalt binder is unique and reflects its fundamental physicochemical characteristics. The commonly used approach is to search the relaxation spectrum from dynamic modulus test data. However, the calculation of the relaxation spectrum from dynamic modulus test data is an ill-posed problem. Although different approaches have been developed for the conversion of the dynamic modulus test data to relaxation spectrum, their validity remains unknown. In this research, a new determination of relaxation spectrum, which obtained by considerations of both static modulus test, such as relaxation modulus test, and dynamic modulus test is proposed and it is found the obtained spectrum is more realistic when one compare both data of relaxation modulus test and dynamic modulus test.

Kin-Ming Chan, Yuhong Wang
Rheological Characterisation of Modified Bitumens with Biodiesel-Derived Biobinders

Growing environmental concerns and scarcity issues of petroleum-derived bitumen have motivated the search for alternative and renewable sources to be used in asphalt mixtures. The concept of biobinders (binders manufactured from biomass) are becoming more popular in the field as a potential solution. In particular, waste biomass products are of interest due to their availability and impact on sustainability. Biobinders have shown great potential to reduce bitumen demand and have exhibited good performance in terms of resisting common distresses affecting roads. However, they are still relatively unknown and detailed characterisation in terms of their engineering properties is needed before they can be used in practice. This paper describes the bio-modification of two penetration grade bitumens with a vegetal-derived biodiesel residue. Three modified bitumens were produced and the rheological characteristics were analysed using a dynamic shear rheometer (DSR). The results indicate that the addition of biobinder ‘softens’ the bitumens by decreasing the complex modulus and increasing the viscous response, except for the higher content modified blend which at high temperatures exhibits a more elastic behaviour. Similar to aged conventional binders, laboratory ageing of the blends increases the elastic response and stiffness.

Ana I. Weir, Gordon Airey, Colin Snape, Ana Jiménez del Barco Carrión
Rheological Investigation on the Rutting Characteristics of Nanoclay Modified Asphalt Binders

This study is aimed at evaluating the rutting potential of a conventional viscosity graded (VG-30) binder modified with different percentages (2–6%) of nanoclay. Rheological investigations, including performance grading (PG) of the binder, frequency sweep (FS) test and multiple stress creep recovery (MSCR) were carried out using a dynamic shear rheometer (DSR). FS and MSCR were done at four different temperatures ranging from 40 to 70 °C. Master curves plotted at a reference temperature of 60°C using FS data indicated better performance of nanoclay modified binders, especially at lower frequency range. Increase in percentage recovery (R) and reduction of unrecoverable creep compliance (Jnr) from MSCR test proved the efficacy of nanoclay as a positive reinforcing agent. At the reference temperature, R value for 2, 4 and 6% nanoclay increased from 0.47% (for VG-30) to 1.71, 3.34, and 5.3% respectively. The corresponding reduction in Jnr was about 12, 14, and 29%. Cole-Cole plots for each binder obtained from frequency sweep test at different test temperatures were modelled using a 3rd-order polynomial. The h-parameter calculated using the Cole-Cole plots at different temperatures were found to appreciably correlate with the values of Jnr and R for all the asphalt binders. In addition to the positive effect of nanoclay modification, it is concluded that h-parameter from the frequency sweep test can be used to explain the rutting potential of asphalt binders.

Mayank Sukhija, Nikhil Saboo
Rheological Modelling of the Bitumen from Reclaimed Asphalt with Rejuvenation and Re-ageing

Hot recycling of reclaimed asphalt (RA) in new asphalt concrete (AC) allows achieving large environmental and economic benefits. However, the aged bitumen in RA has a stiff and brittle behaviour, which may lead the AC to premature fatigue, thermal and reflection cracking. In the last years, many researches aimed at studying the effect of ageing on bitumen rheological properties to model the mechanical behaviour of RA. However, how these properties changes in the AC including hot-recycled RA and rejuvenator during its service life is still an object of investigation. The present paper aims at analysing the evolution of the rheological behaviour of the bitumen extracted from RA with rejuvenation (40/60 blending of virgin and RA bitumen, with addition of a rejuvenator) and re-ageing (simulating the service life of the hot recycled AC). RTFOT and PAV devices were used to reproduce bitumen ageing in the laboratory and DSR allowed determining the complex modulus of the binders. The ageing and rejuvenating effects were characterised through the variation of the 2S2P1D model parameters and apparent molecular weight distribution (AMWD). Results proved the efficacy of the rejuvenation process in reducing stiffness and raising the viscous properties of the RA bitumen. After long-term re-ageing (RTFOT + PAV), the rejuvenated RA bitumen showed comparable rheological behaviour with respect to the bitumen initially recovered from RA. However, AMWD analysis showed that the rejuvenator did not adequately disrupt the asphaltene clusters in the aged bitumen.

Edoardo Bocci, Emiliano Prosperi, Paul Marsac
Rheological Properties and 2S2P1D Modeling of Seven Bituminous Mixtures with Different Brazilian Bitumens

The characterization of the linear viscoelastic behavior of bituminous mixtures is imperative to analyze and design pavements. The objective of this research is to evaluate the rheological behavior of bituminous mixtures originated from seven different modified and conventional bitumens, representing the Brazilian production. In order to develop the knowledge about the influence of the bitumens on the bituminous mixtures properties, it is essential to know the stiffness of the bituminous mixture when subjected to different loads, temperatures and loading frequencies. The influence of these bitumens on the stiffness of the bituminous mixtures was measured in the compression complex modulus test. From the experimental results, the 2S2P1D modeling was performed by the calibration of seven elements, which consider the mechanical analog of 2 Springs, 2 Parabolic elements, 1 Dashpot and the constants C1 and C2 of time-temperature superposition. The seven bituminous mixtures were produced with the same aggregates according to the grain size distribution “C” of DNIT/BR and were designed by the Superpave methodology with 5 conventional and 2 modified bitumens: four 50/70 penetration bitumens from different Brazilian regions, one 30/45 penetration bitumen, one rubber-modified bitumen, and one SBS polymer modified bitumen. The mathematical modeling allows continuous spectrum analysis in the isotherms, isochronous, Black and Cole-cole diagrams and master curves of norm of complex modulus and phase angle, which is possible evaluate the viscoelastic linear behavior over a wider range of frequencies and temperatures than the experimentally employed. It was verified that all the mixtures had similar values of the constants E0 (glassy modulus) and E00 (static modulus), however, they were not identical as expected, reinforcing the influence of the different bitumens. In general, the mixtures presented different behaviors in terms of stiffness.

Évelyn Paniz Possebon, Luciano Pivoto Specht, Hervé Di Benedetto, Silvio Schuster, Deividi da Silva Pereira
Rheological Properties and Rutting Characterization of Natural Rubber Modified Bitumen

From the early nineties, Thailand has been the world's largest producer and exporter of natural rubber latex (NRL). However, the current unbalances in demand/supply has led to a sharp reduction of NRL prices, which has required the Thailand government to boost NRL prices by encouraging domestic consumption and promoting its use as an alternative material for road infrastructure applications. Aiming at selecting and optimizing a suitable percentage of natural rubber latex able to improve the rheological and rutting resistance performance characteristics of natural rubber modified bitumen (NRMB), this research assesses the application of high ammonia concentrated natural rubber latex, which incorporates 60% Dry Rubber Content (DRC) and 40% water by total weight. This NRL was used as a modifier of AC60/70 bitumen at 0, 3, 5, 8% of DRC concentrations. The experimental programme comprised two stages that assessed: (1) the rheological properties by means of the Dynamic Shear Rheometer (DSR) test; and (2) the rutting performance through the Multiple Stress Creep Recovery (MSCR) test. The results indicated that NR increased the complex modulus and reduced phase angle at high temperature, while also providing significant improvement in the rutting resistance. Altogether, the main laboratory results proved that NR latex containing 8% of DRC to be the optimum NR dosage that induces improvements on the rheological properties and rutting performance of NRMB blends.

Jarurat Wititanapanit, Juan S. Carvajal-Munoz, Chakree Bamrungwong, Gordon Airey
Rheological Properties of Asphalt Binder Compound Modified by Bio-oil and Organic Montmorillonite

In recent years, the waste cooking oil (WCO) based bio-asphalt is developed as a potential alternative binder for the traditional petroleum asphalt. Several previous studies demonstrate that the WCO based bio-oil modification generally enhance the binder cracking resistance but has an adverse effect on high temperature performance. This paper aims to improve the rutting resistance of WCO based bio-asphalt by a further compound modification of Organized Montmorillonite (OMMT). Two neat asphalt binders with penetration grades of 70 and 90 are selected in this study. The WCO based bio-oil is firstly added into the neat binders followed by further modified with the OMMT additive. The neat binders, bio-binders and Bio/OMMT binders are then characterized by rheological performance tests in this study. The frequency sweep, multiple stress creep recovery (MSCR) and linear amplitude sweep (LAS) tests are respectively conducted for linear viscoelastic properties, rutting resistance and fatigue performance evaluations. Experimental results indicate that the fatigue resistance of bio-binders at intermediate temperature are improved compared to the neat binders whereas the addition of bio-oil obviously reduces the binder rutting resistance at high temperature. Furthermore, adding the OMMT into the bio-binders is found to effectively enhance the rutting resistance when increasing the OMMT content without compromising the fatigue performance. Therefore, it can be preliminary concluded in this study that the Bio/OMMT compound modification approach can be utilized to address the rutting potential concern of WCO based bio-binders at the high temperature condition.

Tingting Xie, Yifang Chen, Chao Wang
Rheological Properties of Bituminous Mastic with Different Filler Content

Bituminous mixture is widely used for pavement construction. It is made of coarse aggregates, fine aggregates and mineral filler, and mixed with bitumen. The coarse aggregates form a skeleton structure in mixture and the fine gravel with bitumen form a mortar. The mineral filler with bitumen forming a mastic, which determines the rheological characteristics of bituminous mixture. This study focuses on rheological properties of bituminous mastic with different content of mineral filler and with different types of bitumen such as base bitumen, SBS modified bitumen and warm bitumen (modified by Evotherm or Sasobit). By measuring the penetration, ductility and softening point of different mastics, and by applying the Brookfield test and DSR test, the viscosity-temperature curve and viscoelastic property are analyzed. The contribution of mineral filler content in mastic is discussed. The difference of rheological property among different mastic is emphasized, and the effects of warm mixing are analyzed. The results show that the technical parameters of bituminous mastic (penetration, ductility, softening point and viscosity) change linearly with the mineral filler content in normal or semi-logarithmic coordinates. The warm bituminous mastic has a larger phase angle in dynamic viscoelastic analysis and SBS bituminous mastic has a smaller phase angle. The warm additive of type “surfactant” doesn’t change the technical parameters of bitumen, but increases dynamic shear modulus, the warm type of “bitumen viscosity reduction” changes the technical parameters of bitumen.

Xi-li Yan, Peng Li, Qing-long You, Xi-juan Xu
Rheological Properties of Derived Fractions Composed of Aromatics, Resins, and Asphaltenes

The chemical makeup of the asphalt binder determines its rheological and mechanical properties. The objective of this study is to reveal the rheological properties of various fractions composed of aromatics, resins, and asphaltenes. First, asphalt binder (pen grade 60/80) was separated into four fractions and then resins and asphaltenes were respectively doped into aromatics to fabricate four derived fractions. The frequency-temperature sweep was conducted by a dynamic shear rheometer (30–80 °C, 0.01–20 Hz, and 0.01% shear strain). The complex shear modulus master curves of various fractions were developed based on measured data. The test results showed that the increase in the content of resins or asphaltenes resulted in the increased complex shear modulus, stated that an increase in polarity leaded to higher stiffness. Meanwhile, various fractions had different sensitivity to temperature. Resins showed the most sensitivity to temperature change among all the fractions. The synergy of resins and aromatics resulted in the different master curve shapes of derived fractions. Furthermore, the predicted model of the master curve based on composite material idea showed a good fitting trend within a frequency over 0.1 Hz. Future work should focus on the interaction of aromatics/resins and aromatics/asphaltenes to fully determine the effect of SARA fractions.

Feipeng Xiao, Jiayu Wang
Rheometrics Framework Analysis to Capture Self-assemblies Organization in Bitumen Matrix

In this work, the liquid to solid transition of self-assemblies into bitumen matrix obtained with gelator additives is studied through rheometrics framework analysis. A very small amount of these organic compounds is able to harden bitumen and to shift the temperature range where they display solid-like behavior. Current test methods such as the softening point, the penetration needle test or the indentation depth are not sufficient to describe the gelling process of such soft matter. Rheometrics analysis are found to be more appropriate to rigorously determine the liquid to solid transition of the system as well as their mechanical properties. In opposite to the classical methods of characterization, the rheological experiments require a very small volume of sample, they are more sensitive and they give more information. Thanks to the sensitivity of rheometrics analysis, different temperatures can be identified such as the temperature of the Newtonian/viscoelastic transition and the temperature of the liquid/solid transition of pure or modified bitumen. Another advantage of rheometrical test is the characterization of the different viscoelastic behaviors of these materials with enlarged time spectrum.

Caroline Bottelin, Marc Chardonnet, Philippe Marchal, Lazaros Vozikis, Yvong Hung
Roles of Exogenous Cationic and Endogenous Bitumen Surfactants in the Stability of Bitumen/Water Interfaces

Bitumen-in-water emulsions are often used for paving applications but some of them lack long-term stability. The relative importance of the cationic surfactant added to the aqueous phase to favor emulsification and the endogenous ones contained in bitumen is investigated by measuring the visco-elastic properties of three different bitumen-water interfaces as a function of time. We observe that the long-term emulsion stability correlates well with high values of the interfacial storage (G′) and loss (G″) moduli. Since these parameters become significantly weaker when an emulsamine cationic surfactant is added to water, we emphasize that the use of exogenous surfactants may be detrimental to long-term emulsion stability from interfacial behavior point of view.

Shweta Jatav, Patrick Bouriat, Pauline Anaclet, Yvong Hung, Francis Rondelez, Christophe Dicharry
Rubber-Bitumen Interaction of Plant-Blended Rubberized Bitumen Prepared Under Various Blending Conditions

Rubberized bitumen produced from waste tyre rubber has been widely used as a sustainable paving material around the world. However, different production conditions may lead to rubberized bitumens with different performances. This study aims to understand the mechanism of physicochemical interaction between rubber particles and virgin bitumen of plant-blended rubberized bitumen prepared under various blending conditions. To achieve this objective, samples of plant-blended rubberized bitumen prepared under four conditions were first collected, including blending at 170 °C for 1 h, and blending at 170 °C for 1 h followed by blending at 183 °C for 1, 3, and 5 h. Then the microstructure, viscosity, storage stability, and rheological properties of these samples were characterized. Microstructural results indicate main crosslinking structures of rubber particles remain stable and undamaged with the occurrence of chemical reactions including oxidation, decarboxylation, and devulcanization during the whole production period. The storage stability results state the rubberized binder exhibits no obvious phase separation after storage at 163 °C for 48 h, and becomes more stable as the blending time prolongs. The rheological results indicate the rubber-bitumen interaction is mainly composed of early-stage absorption and swelling of rubber particles, continuous emission of volatile bitumen fractions, and late-stage partial degradation of fully swollen rubber particles.

Xiong Xu, Zhen Leng, Jingting Lan, Rui Li, Zhifei Tan, Anand Sreeram
Rutting Performance Analysis for Pavements with Bituminous Stabilized Mixtures as Base Layers

Cold recycling techniques are becoming more and more popular everywhere in the world, as it is well proven that bituminous stabilized mixtures (BSM) are sustainable both from an environmental and economical point of view. There have been limited studies focusing on the performance of BSMs with respect to the service lives of pavement structures with in-place recycled layers. For this reason, this research focuses on the modelling of multilayer structures with different layer combinations and thicknesses. The aim is to compare structures with different base layer solutions, such as BSM, typical granular unbound base layer, and combinations of those two. Finite element analysis software has been used to construct axisymmetric elasto-plastic 2D models of various pavement cross-sections. The modelled structures were subjected to a cyclic loading of 0.1 s with 0.9 s of rest period. The load applied on the structures has been calibrated in order to have a comparable effect to the real tire pressure experienced by the structures under traffic. Rutting evolution curves until a failure threshold value of 20 mm have been developed and the results have clearly shown how the BSM as a base layer can provide superior or comparable performance in terms of rutting as compared to granular virgin material.

Beatriz Chagas Silva Gouveia, Francesco Preti, Elena Romeo, Eshan V. Dave, Gabriele Tebaldi, Jo E. Sias
Sensitivity Analysis for Rheological Determination of Glass Transition and Crossover Temperatures at Various Reference Frequencies

Accurate and relevant rheological characterization is critical for the improvement of current binder specification, modification and formulation strategies, and ultimately the pavement performance. Significant changes have affected the binder quality since the Superpave specification development due to various economic, technical, and environmental motives. This paper assesses the effect of some of these changes on binder rheology. The rheological behavior of binders was investigated by plotting the data in isochronal plots. In these plots, the rheological behavior at a reference frequency is classified into three regions: (1) near glassy region at temperatures below the glass transition temperature (Tg), (2) terminal region at temperatures above the crossover temperature (Tx), and (3) an intermediate “transition” region in between. The intermediate temperature range (TIR) parameter is the difference between Tx and Tg. In this study, Tg and Tx of 30 binders were obtained using 4-mm parallel plates geometry on a Dynamic Shear Rheometer (DSR), and using isochronal plots calculated at various reference frequencies. Additionally, modulated differential scanning calorimetry (MDSC) was used as a widely accepted technique to determine Tg of the binders. In the paper, DSR-calculated Tg at various reference frequencies is compared with MDSC-measured Tg. Tg obtained at a reference frequency of 10 rad/s shows promising correlations with DSC-measured Tg and low-PG temperature based on stiffness (Tc(S)), while Tx at 10 rad/s correlates with low-PG temperature based on stiffness slope, m-value (Tc(m)). Furthermore, TIR correlates with ΔTc, an empirical parameter considered for future specifications in the USA related to cracking. The aforementioned correlations are very promising and provide insights related to the fundamental meaning of the ΔTc parameter and guidelines to formulate binders that meet future specifications. In-depth analysis is ongoing to evaluate how isochronal parameters (Tg, Tx, and TIR) are affected by the reference frequency, and how they relate to binder composition.

Michael D. Elwardany, Jean-Pascal Planche, Jeramie J. Adams
Shear Fatigue Cracking Analysis of Pavement with Thick Asphalt Layers Induced by Traffic Load

Top-Down cracking is one of the major distresses induced by traffic load for the pavement with thick asphalt layers. In this paper, an analytic model of pavement with thick asphalt layers is established in which four types of base layers are considered corresponding to the different combinations of semi-rigid and granular materials. The shear stress intensity induced by the traffic load in thick asphalt layer is calculated by the analytic model firstly. Then many beam specimens of asphalt mixture are made in laboratory and the shear fatigue test were conducted. According to the test results, the fatigue cracking parameters in Paris equation were regressed. Finally, the shear fatigue life of thick asphalt layers was evaluated basing on shear stress intensity and Paris Law. The research results show that the shear fatigue life increases with the increasing of asphalt layers thickness. The structure I (thick asphalt layer with semi-rigid base and semi-rigid subbase) has the longest fatigue life and structure IV (thick asphalt layer with granular base and granular subbase) is weakest in resisting shear fatigue cracking.

Shan Jingsong, Han Lujia, Guo Zhongyin, Li Feng
Solar and Permeable Road: A Prototypical Study

A solar road is a pavement infrastructure able to generate electricity exploiting the solar radiation. Notwithstanding the progress of the research, several issues still hinder these typologies from getting an outstanding role, among which their uncertain durability, surface performance, and permeability. In the light of this, a novel permeable and solar road is here proposed. An innovative top layer was designed, taking into account hydraulic and transport-related issues. The basic idea was to improve the wet friction by setting up and advancing a water drainage system. The pavement was validated in terms of hydraulic and friction properties, in order to assess its ability to perform satisfactorily in dry and wet conditions. A system to simulate rainfall was designed and constructed. The results demonstrate the feasibility of coupling energy harvesting and premium surface properties (such as permeability). The contributions of this study aim to improve from a draining point of view the typical solar pavement package. Results can benefit both practitioners and researchers.

Domenico Vizzari, Pierfabrizio Puntorieri, Filippo G. Praticò, Vincenzo Fiamma, Giuseppe Barbaro
Statistical Analysis of the AIGLE 3D Crossover Trial Campaign: Experimental Design, Methods and Results

These ever-increasing needs for road maintenance and the willingness to optimise its maintenance works with a long-term approach leads Cerema to develop new tools and methods for road survey. Based on Pavemetrics Laser Crack Measurement System (LCMS) sensors and a precise GNSS localization system, Cerema has designed two new inspection vehicles called AIGLE 3D. To make the measurements campaign more reliable, we implemented an optimized organization and significant improvements such as remote maintenance and a merged tool controlling all sensors in vehicles. Pavemetrics, a partner of Cerema, developed the LCMS system and new 3D functionalities allowing measurements up to 130 km/h. LCMS sensors can measure the roadway with an accuracy of 1 mm in the directions of the roadway and 0.5 mm in height up to a speed of 130 km/h. This set (LCMS sensors, localization) provide a 3D model of the road surface instead of considering it as a single wire. Thus, we obtain a true representation of the data collected with the system. The data processing system developed at Cerema makes it possible to precisely geo-locate all degradations, deformations, geometry and objects on the roadway. With this new technology, it becomes necessary to set up a new method of exploitation and analysis for the auscultation of roadway. Cerema performed a cross-testing campaign in order to evaluate the quality of the data produced by AIGLE 3D inspection vehicles. The purpose of this article is to resume the crossover trial campaign and set up an analysis method. Results of this measurement are then presented and analyzed.

Pierre Gayte, Marie Delaye
Study of the Shear Stiffness of Bituminous Mastics Incorporating Recycled Glass Fillers

This paper studies the effect of recycled glass (RG) filler on the shear stiffness of mastics (mixture of bitumen and filler) in the linear viscoelastic domain (LVE). The research project was carried out at the Laboratory of Roads and Bituminous Materials (LCMB) of the École de technologie supérieure (ÉTS) using a new experimental device called the annular shear rheometer (ASR). The complex shear modulus G* of bitumen and mastics were measured under various temperatures and frequency conditions (from −25 to 45 °C and from 0.03 to 10 Hz). Two types of RG fillers (crushed glass and micronized glass) and a reference limestone filler were used to manufacture the PG70-28 based mastics. The complex coefficient of reinforcement $${{{{R}}}_{{{M}}}}^{{*}}$$ R M ∗ was used to compare the shear stiffness of RG mastics with a limestone-based mastic. Results indicate that the RG filler effect is important at high temperature and/or low frequency where no significant effect was observed at low temperature and/or high frequency. Moreover, the filler size gradation seems to have most influence on the viscoelastic properties of the mastics at high temperature. Overall, it was shown that RG fillers are suitable for improving mastic shear stiffness in a pavement structure.

Mohamed Mounir Boussabnia, Michel Vaillancourt, Daniel Perraton
Study on Aging Resistance of Bitumen Rejuvenated with Various Rejuvenators for Hot Recycling

In this study, oxidized bitumen blend was rejuvenated with five rejuvenators, namely Tall oils, two fatty acids (FA 1 and FA 2), two paraffinic oil (PO 1 and PO 2). A relationship was developed between the viscosity of aged bitumen and target rejuvenator content for all the rejuvenator types considered in the study. The aging of bitumen was simulated by conditioning the VG40 bitumen in Rolling Thin Film Oven (RTFO) and Pressure Aging Vessel (PAV) for different conditioning periods. The relationship between viscosity of artificially aged bitumen and the target rejuvenator content was verified using recovered bitumen from Reclaimed Asphalt Pavement (RAP) material from two different sources. An error percent of 1–13% was observed in achieving target viscosity. To study the effectiveness of the rejuvenator w.r.t to the aging of rejuvenated bitumen blends, target rejuvenator content derived from the developed relationships was added to RAP bitumen blend, and the resulting bitumen blends were subjected to short term and long term aging. The aging indices were then calculated as the ratio of complex modulus at aged state to unaged complex modulus, which indicates the aging susceptibility of rejuvenated blends. The aged bitumen blended with Paraffin Oils category rejuvenator showed the least resistance to aging.

Chetan Kumara, Gurunath Guduru, Bharath Gottumukkala, Kranthi Kuna
Study on Reversibility of Aging and Recycling of Bitumen Based on Rheology, Adhesion and Chemical Properties

The reversibility of aging and recycling of bitumen directly influences the recycling efficiency and durability of recycled pavement. Rolling thin film oven (RTFO) and pressure aging vessel (PAV) were conducted to simulate the different degrees of aging process. The rheology, adhesion and chemical properties of bitumen samples at different aging and recycling stages were characterized by dynamic shear rheometer (DSR), contact angle test and Fourier transform infrared spectroscopy (FTIR). The results reveal that the complex modulus of short-term aged bitumen can be completely recovered to the level of virgin bitumen. The complex modulus of long-term aged bitumen can also be recovered, but higher than that of virgin bitumen. Aging reduced the adhesion between bitumen and limestone. The anti-stripping agent can increase the adhesion of both short-term aged bitumen and long-term aged bitumen by 19.0% and 44.8%, respectively. The carbonyl index and sulfoxide index increased by 3614.6% and 441.9% after long-term aging, and decreased by 54.0% and 40.5% after being recycled, respectively. The revelation of reversibility of aging and recycling of bitumen can help to understand the mechanism of aging and recycling and improve the recycling technology.

Meng Guo, Haiqing Liu, Yubo Jiao, Yiqiu Tan
Superpave 5: Improving Asphalt Mixture Performance

The traditional Superpave mixture design method selects optimum asphalt binder content to yield 4% air voids content in asphalt mixtures, while anticipating approximately 7% air voids content at the time of construction. This approach can produce mixtures with high ageing and moisture damage potential. A recently developed mixture design method named “Superpave 5” is nearly identical to the traditional Superpave mixture design method, except that optimum binder content is selected to yield 5% air voids content with the expectation that when field compacted, the mixture will also yield 5% air voids content. The objective of this study is to assess the viscoelastic, cracking, and rutting properties of Superpave 5 mixtures and compare them with a traditionally designed Superpave mixture. Four plant-mixed Superpave 5 and one laboratory-mixed traditional Superpave mixtures were evaluated using complex modulus testing, the Illinois Flexibility Test, and the Hamburg Wheel Track Test. The results indicate that Superpave 5 mixtures exhibit improved laboratory rutting performance. However, the Flexibility Index does not seem to be an appropriate cracking indicator, as it appears unable to distinguish between air voids contents.

Reyhaneh Rahbar-Rastegar, M. Reza Pouranian, Dario Batioja-Alvarez, Mohammad Ali Notani, Miguel Montoya, John E. Haddock
Surface Dressing Treatment for Applications on Solar Roads

The solar road concept is a pavement system able to harvest energy from the solar radiation. This paper is part of a wide project for the design of a multilayer system able to harvest energy through the road. In this technology, the top layer plays a fundamental role because it has to support the traffic load, guarantee the vehicle friction and protect the solar cells. For this purpose, the authors proposed a novel approach for the construction of a semi-transparent layer made of glass aggregates bonded together through a transparent polyurethane, inspired from surface dressings. The procedure consists on spreading a first layer of polyurethane binder on the solar cells in order to obtain a uniform surface. Once the polymerization is completed, a second layer of binder is laid down and the aggregates are spread and compacted immediately. For the samples manufacturing, three different thermosetting polyurethanes and a 2/4 mm fraction of glass aggregates were used. The samples were compared in terms of optical and mechanical performances. The authors studied also the packing density of the aggregates in order to quantify the optimum amount of binder. The results show the potential of this novel top layer in terms of optical and mechanical performances, demonstrating the feasibility of the surface dressing treatment for applications in full scale solar roads.

Domenico Vizzari, Eric Gennesseaux, Stéphane Lavaud, Stéphane Bouron, Emmanuel Chailleux
Sustainability Assessment of Novel Performance Enhancing Chemical Bitumen Additive

Increasing traffic, changing climatic conditions and new safety requirements during construction, as well as the pursuit of sustainable road construction generate the need for new pavements solutions (materials). A novel reactive chemical bitumen additive (B2Last®) can be such a solution, because B2Last®-modified asphalt has the capability of being produced and paved at reduced temperatures. In this investigation, data collected from field tests, together with stiffness and fatigue tests carried out in the laboratory, were compiled to study the service life of asphalt layers with and without B2Last® following the German Standards (RDO Asphalt 09). The results of these tests were combined with data gathered from past field trials in order to perform an extensive service life analysis. Based on these results, a sustainability assessment was done to point out three main aspects: (i) ecological aspects by a life cycle assessment (LCA) according to ISO 14040; (ii) economic aspects conferring to life cycle costs; (iii) social aspects like occupational exposure to vapors and aerosols. The results obtained so far are major sustainability requirements which are fulfilled by using B2Last®. This study is illustrating that better performances of pavement can still be achieved nowadays by providing innovative solutions to the asphalt industry.

Christian Holldorb, Amina Wachsmann, Sonja Cypra, Markus Oeser, Nicolás Héctor Carreño Gómez, Michael Zeilinger
Temperature and Loading Rate Susceptibility of Bituminous Mixtures on Monotonic Testing

The loading rate and temperature susceptibility of bituminous materials is of great importance. Their modulus and phase angle are strongly affected by any change of these two variables. For that reason, many researchers have explored the time-temperature superposition principle that assumes a thermo-rheologically simple behavior, i.e., all curves have the same characteristic time variation law with temperature. Nowadays it is common to obtain the so-called master curve of any bituminous material (binder, mastic or mixture) using dynamic testing. A side from that, several monotonic test methods have been proposed recently to obtain the cracking resistance of asphalt mixtures at low and intermediate temperatures. Many of them are focused on extracting ductility related parameters at temperatures close to 20 °C. Since the cracking resistance of the mixtures is strongly related with their stiffness and phase angle, it is also dependent on the loading rate and the test temperature. Joining these two concepts, this paper presents the efforts to analyze the influence of loading rate and test temperature in the different parameters that can be extracted from a monotonic test, such as the Fenix test. By testing different mixtures at different temperatures and different loading rates, the influence of these three variables in the different parameters that characterize the stiffness and ductility of the mixtures was analyzed. Finally, the possibility of obtaining a sort of master curve or an absolute reference value for each mixture in terms of any of the parameters considered was explored.

Ramon Botella, Félix E. Pérez-Jiménez, Rodrigo Miró, Adriana H. Martínez, Teresa López-Montero
Temperature Dependency of the Stiffening Effect of Hydrated Lime in Stone Mastic Asphalt (SMA) Mixtures

The effect of hydrated lime (HL) on the stiffening effect of bituminous mixtures is mainly driven by a physical phenomenon derived from the higher Rigden Air Voids (RAV) of HL in contrast to other filler types commonly used in bituminous mixtures such as granite and limestone. The stiffening effects of HL at room temperature for some mixture types have been reported in the literature but the knowledge of the effects on Stone Mastic Asphalt (SMA) mixtures is still limited. Similarly, the temperature-dependency has been theorised in the literature but scarce experimental evidence is currently available. As a consequence, this research focuses on studying the effects of a wide range of temperatures on the stiffening effect of SMA mixtures with HL. Indirect Tensile Stiffness Modulus (ITSM) testing was used in order to assess the stiffness properties of SMA mixtures manufactured with limestone aggregates, a conventional 30/45-penetration grade bitumen, and the addition of HL as a partial replacement of limestone filler (LF). The bitumen to filler ratio was kept as 1:1 for all manufactured mixtures. The results indicated: (i) a clear temperature-dependency of the stiffening effect of HL, which is more prominent at intermediate temperatures (20 and 30 °C). (ii) The percentage of added HL and the average stiffness of the specimens had an approximately linear correlation. (iii) The stiffening effect is less prominent at the lower and higher temperatures considered. (iv) The partial replacement of LF by HL produced stiffer mixtures than those without replacement, which suggests improved mechanical response of these SMA mixtures.

Mariella Cardenas, Juan S. Carvajal-Munoz, Gordon Airey
Testing of Reclaimed Asphalt Model Systems for the Evaluation of the Effectiveness of Rejuvenators

This paper presents the results of a preliminary study on the use of a novel approach for the evaluation of the effectiveness of rejuvenating agents used in asphalt mixtures containing reclaimed asphalt (RA). Such an approach is based on the mechanical testing of model systems constituted by a single-sized RA material, in its original state and after pretreatment with rejuvenators, compacted to a target volumetric condition. Model systems were prepared by making use of two rejuvenators and by also considering a reference combination of virgin binder and aggregates extracted from the RA. Tests were carried out for the evaluation of stiffness modulus and indirect tensile strength as a function of curing time. Experimental results showed that the proposed approach can capture the changes occurring in the aged RA binder as a consequence of the effects induced by rejuvenators. Quantification of the rejuvenating effects was carried out by analyzing recorded stiffness and strength variations, and by referring to a ductility toughness index, introduced to better describe stress-strain response after failure.

Davide Dalmazzo, L. Urbano, P. P. Riviera, Ezio Santagata
The Bitumen Related Problems Observed on Soft Asphalt Concrete Pavements: Case Study

Four roads paved with soft asphalt concrete during the autumn of 2017 by one contractor in a Nordic country, damaged during the following winter. The road users reported that bitumen detached from the surface and was sticking to the fur of pet animals, as well as to the surfaces of the vehicles. The article discusses aspects connected with production and paving, which may have affected the performance. In addition, the material analysis of the samples collected from the field was performed. The core samples were tested by Indirect Tensile Strength (ITS). Because of the low strength of the soft asphalt concrete the ITS is not routinely performed for this material. Therefore, the results of ITS were inconclusive due to the lack of reliable references. The gradation was analyzed after the bitumen extraction and recovery, and no abnormalities were discovered. The Zero Shear Viscosity at multiple temperatures and fractional composition was performed on both extracted and reference binders type V1500 and 650/900 (EN 12591) after evaluation of bitumen purity with infrared spectroscopy. The bitumen extracted from the most questionable pavement expressed comparable rheological behavior to references, but was characterized by the exceptionally high content of saturates. The short research project was unable to determine if the damage was a result or the reason for the altered binder composition. Nevertheless, the link between abnormal performance observed in the field and abnormal chemical characteristic of bitumen is reported.

Michalina Makowska, Katri Eskola
The Chemistry Behind Rheological and Thermal Transitions of Oxidized Bitumen

Chemical functional groups such as carbonyls, sulfoxides and unsaturations are considered the most significant changes that occur in bitumen molecules with oxidation. Such transformations influence the mechanical and thermal responses of the material. This study aims to analyze the topic by means of producing highly oxidized bitumens to correlate oxidation indexes to rheological and thermodynamic parameters. The results showed that the chemical changes largely influence the rheological and thermal responses. It was found that the stronger interactions that bond the oxidized molecules cause the bitumen to exhibit a more glassy-like behavior, which is translated into higher crossover and lower glass transition temperatures. These findings highlight the importance of knowing the chemical composition of bitumen and how it changes through the materials’ service life to determine the temperatures at which the material is more susceptible to fatigue cracking.

Alejandra Baldi, Rafael Ernesto Villegas-Villegas, José P. Aguiar-Moya, Luis G. Loria-Salazar
The Effect of a Chemical Warm Mix Additive on the Self-Healing Capability of Bitumen

Warm mix asphalt (WMA) technologies reduce the production temperature of hot mix asphalt (HMA) allowing for mixing and paving at lower temperatures. As a result, the use of WMAs reduces emissions and allows for longer transport times. Due to the recent increase of chemical warm mix additives in industry, the effect of a chemical warm mix additive (cWMA) on the intrinsic self-healing ability of the bitumen was investigated. Bitumen specimens containing three concentrations of cWMA were evaluated at four aging levels (unaged, RTFO-163 °C, RTFO-130 °C, and PAV aged) using the Simplified-LASH (linear amplitude sweep with a single rest period) fatigue-healing test. Results indicate that oxidative aging of bitumen is reduced with increasing cWMA concentration but may be more heavily influenced by the aging temperature. It was also observed that PAV aged bitumen samples demonstrate greater fatigue restoration ability compared to RTFO and unaged binders. This trend is counter to our current understanding of bitumen self-healing warranting further research on the factors that affect LAS-based fatigue healing tests.

Roberto M. Aurilio, Mike Aurilio, Hassan Baaj
The Effect of Additives on Water Vapor Condensation on Bituminous Surfaces

Ice formation and adhesion on bituminous asphalt concrete are responsible for many accidents in winter and have caused an overreliance on deicing treatments such as anti-icing chemicals, which are costly, environmentally damaging, and increase maintenance frequency. Bitumen is mainly a combination of various kinds of hydrocarbon-based chemicals and exhibits complex material behavior and properties. However, bitumen makes up only ca. 5 wt.% of the asphalt concrete mixture. Owing to its binder role and coating function of the aggregates, bulk mechanical properties and surface properties of the mixture are dominated by bitumen. In this study, we investigate the phenomenon of condensation from humid air and, eventually, ice formation from condensate on bitumen as the first step toward understanding the freezing of road surfaces. We report first results on these phenomena as they develop on various regions of the complex bitumen surface featuring different wettabilities due to their chemistry. Furthermore, in this study, we show the effect of different additives: polyethylene terephthalate (PET), polyamide (PA 66), polyacrylonitrile (PAN), and Sasobit wax on bitumen water affinity.

F. Tarpoudi Baheri, M. Rico Luengo, T. M. Schutzius, D. Poulikakos, L. D. Poulikakos
The Effect of Mix Constituents in the Permanent Deformation Resistance of Asphalt Mixtures

This study evaluated 28 asphalt mixtures with respect to the relationship between the results of their uniaxial repeated load test and tests of their corresponding binders: Multiple Stress Creep and Recovery (MSCR), G*/sinδ, softening point, and Brookfield viscosity at 135 °C. The following parameters were considered: binder content, aggregate mineralogical origin, Nominal Maximum Aggregate Size, and type of filler. It was found a low relationship between the binder Performance Grade (PG) and the mixture Flow Number (FN). Non-recoverable compliance (Jnr) at 3.2 kPa−1 and 64 °C, G*/sinδ at 70 °C, and softening point were found to be better indicators of mixture resistance to rutting. The relation Jnr × FN was better expressed by a potential curve, which calls attention for linear regressions commonly used in the literature. Based on the results, the binder parameters were insufficient to predict the behavior of the corresponding mixture with respect to its resistance to rutting. This work also suggests that FN values are better governed by the characteristics of the binders when they are modified. When pure binders are used, the responsibility becomes greater for parameters such as skeletal stone structure and mix volumetrics. Finally, additional evaluation is suggested including other properties related to permanent deformation, such as aggregate interlocking and morphology.

Otávio José de Freitas Gomes, Jorge B. Soares, Juceline Batista S. Bastos
The Heating and Compaction of Asphalt Mixtures as a Self-healing Mechanism

Asphalt mixtures can recover their strength completely autonomously, or only with a small external stimulus, like heat. Therefore, this paper aims to investigate the recovery of asphalt mixtures by heating and recompacting them. Asphalt mixtures AC25 (maximum aggregate size 25 mm) were produced with conventional bitumen, varying asphalt content, ie 3.7, 4.0, 4.3, and 4.6%. In order to evaluate the self-healing mechanism, prismatic beams were heated to 120 °C and recompacted with 300kPa dynamic pressure. The complex modulus and fatigue strength were evaluated at 20 °C. Fatigue tests were conducted at 10 Hz frequency. The recoverability of each asphaltic mixture was assessed by the Healing Potential Index (HPI). The proposed index was calculated in two different ways, both using fatigue laws, one obtained with dissipated energy at failure and other obtained using the tensile strain. It has been found that the heating and compaction process allows the mixtures to recover part of their initial strength.

Caio R. Santos, Marina M. Cabette, Jorge C. Pais, Paulo A. Pereira
The Impact of Binder Type on Pavement Design: A Comparative Study

Rutting is one of the failure modes in flexible pavements and is associated with reduced pavement serviceability since it results in aquaplaning, reduced skid resistance and increased roughness. Variations in material characteristics influence significantly the rutting resistance of asphalt mixes. Dynamic modulus (E*) is a fundamental property of Hot Mix Asphalt (HMA) and as such it is associated with mix properties, loading time and temperature. Thus, dynamic modulus is a critical input parameter for the computation of the induced stresses and the developed strains within the pavement structure. The present paper investigated the impact of different types of asphalt binders on E* values, as well as on predicted permanent deformation. Three different asphalt binders were utilized for the scope of the investigation: one pure and two modified. A comparative analysis was performed in terms of pavement design varying the thickness of asphalt layer. Analysis results showed that asphalt mixes with modified binder can achieve better performance in terms of permanent deformation compared to those with pure asphalt provided that there is an equilibrium for the increased cost of using additives for the modification.

Konstantina Georgouli, Christina Plati, Andreas Loizos
The Influence of Cement Type on Early Properties of Cold In-Place Recycled Mixtures

Cold in-place recycling is a commonly used maintenance treatment in rehabilitation of low and medium volume roads in Poland. Typically, two types of binding agents are used—cement and bituminous emulsion (or foamed bitumen). Due to the harsh Polish climate with many freeze/thaw cycles and frequent occurrence of saturated conditions, the used amounts of cement are higher than those commonly used in warmer parts of Europe. While there is usually only one type of bituminous emulsion dedicated for cold recycling on the market, there are numerous types of cements, which differ in chemical composition and properties. The conducted research presents possible development of cold recycled mixture properties over curing time, taking into account the type of cement used. Two types of cement were tested in laboratory investigation—common Portland CEM I 32.5 R cement and Portland-fly ash CEM II 32.5 B-V cement with longer setting time. Cold recycled mixtures were designed with the same composition and amount of binding agents, but differed in the type of cement used. For both mixtures, indirect tensile strength and modulus were tested after 7, 28 and 90 days of curing in laboratory conditions. The laboratory tests confirmed lower values of strength and modulus for the fly ash cement after 7 and 28 days in comparison to the typical cement, but after 90 days the properties of both tested mixtures presented similar values. If the overall predicted fatigue life and long-term mechanical properties are the same, the use of slow-setting cements may result in reduction of reflective cracking on the surface of the pavement. In the case of low and medium volume roads, where there is no need for fast paving of the asphalt layers and more time may be allowed for the cold-recycled mixture to achieve the required initial strength, slow-setting cements should be considered as a viable treatment for reduction of the risk of reflective cracking.

Bohdan Dołżycki, Mariusz Jaczewski, Cezary Szydłowski
The Influence of the Mastic Coating of Untreated Reclaimed Asphalt Pavement on the Permanent and Resilient Behaviours

Asphalt aggregates arise from the demolition of asphalt road layers. The ORRAP (Optimal Recycling of Reclaimed Asphalts in low-traffic Pavements) Project concerns the cold recycling of 100% Reclaimed Asphalt Pavement (RAP) without binder addition in base and subbase layers of low-traffic roads. In this context, a test program was performed with Rhine Region materials to evaluate the impact of the mastic coating of untreated RAP. A source of reclaimed asphalts with 4.4% of bitumen is tested before (RAP) and after binder extraction (RAP-BE), then is compared to an unbound granular material (UGM) with a similar particle size distribution. Repeated Load Triaxial (RLT) tests were conducted to study the permanent and resilient behaviours. The results show that the RAP before binder extraction and the UGM present similar permanent behaviours, while the aggregates without binder reveal low strains. Concerning the resilient phase, the RAP and the RAP-BE show similar levels of strains, but the resilient moduli of the UGM are significantly lower than those of the RAP.

Laura Gaillard, Cyrille Chazallon, Pierre Hornych, Juan Carlos Quezada, Jean-Luc Geffard
The Influence of Wax Model Compounds on the Surface Topography of Bitumen

In literature, microscopy techniques including atomic force microscopy (AFM), scanning electron microscopy (SEM) and recently also confocal laser scanning microscopy (CLSM) have been used to study the microstructure of bitumen. Especially by AFM, various surface morphologies have been observed. Well-known are the so-called bee structures, related to a regular height profile of lower and higher regions. The appearance of these microstructures has been linked to the presence of crystallizing waxes. In addition to this, other regions surrounding, or in between the bee structures have been described. These have been referred to as the perpetua or peri structures, and very little is known about the origin or formation of these phases. In this study, straight, saturated hydrocarbons of specific chain lengths, were added to a wax-free naphthenic bitumen, and the air-bitumen interfaces were investigated by AFM. As expected, the unmodified bitumen did not display any topological microstructure, and by adding waxes to this binder, bee structures could be generated. However, not only bee structures were obvious, but the intermediate phases could also be generated under certain conditions. The chain length of the waxes, as well as their blending ratios were the determining parameters for the type of structures that were formed. So, in conclusion, this study demonstrates that not only the bee structures, but also the intermediate and/or surrounding structures are related to the presence of waxy hydrocarbons, and no other molecular structures are needed or involved in the formation of these structures.

Johan Blom, Niko Van den Brande, Hilde Soenen
The Low Temperature Performance of Rubberized Bituminous Mixture Using the Dry Process

The paper evaluated the low temperature performance of the bituminous mixtures, which were produced in the plant using the dry process and compacted in the laboratory. ElastikoR crumb rubber was chosen to modify the bituminous mixture. Four types of bituminous mixtures, including leveling layer and surface layer gradation with and without crumb rubber, were produced in a plant in Iron Mountain, MI. The volumetric design of the mixture followed the Superpave mixture design. The leveling layer and surface layer mixture used 25 and 17% recycled asphalt pavement (RAP) (by weight of bituminous mixture). To improve the moisture resistance, dosages of 0.125 and 0.08% anti-stripping agent (by weight of bitumen) were selected for the leveling layer and surface layer. The low temperature cracking properties of four types of bituminous mixtures were evaluated using the Disk-shaped Compact Tension (DCT) test. The RAP content, bitumen content, and nominal maximum aggregate size (NMAS) influenced the low temperature cracking performance of the bituminous mixture. The fracture energy of the surface layer bituminous mixture was higher than that of the leveling layer bituminous mixture. The cracking resistance of the leveling layer and surface layer bituminous mixture were improved after the addition of rubber. The maximum CMOD was linearly correlated with the fracture energy of different types of bituminous mixtures.

Dongdong Ge, Xuelian Li, Zhanping You
The Use of Direct Shear Test for Optimization of Interlayer Bonding Under a Poroelastic Layer

Poroelastic Road Surfaces (PERS) are characterised by porous structure with air void content of 20% or higher and stiffness almost 10 times lower than that of a standard asphalt course. Such properties enable noise reduction by up to 12 dB in comparison to SMA 11 mixture. However, the disadvantage of a poroelastic pavement is its low durability, which partially results from delamination from the lower layer. The paper aims to investigate the effect of type and amount of tack coat used as well as the texture of the lower layer on interlayer bonding, to better recognise the issue of bonding under the poroelastic layer. For this purpose, direct shear test with monotonic and cyclic load was performed for 44 types of layer interfaces. The effect of type and amount of bituminous emulsion used for tack coat as well as the impact of lower layer surface were distinguished. The results of the analysis indicated that tack coats made from softer residual bitumen (70/100) exhibited better fatigue resistance, while polymer modification had minor effect. Moreover, milling of the lower layer resulted in a significant increase in shear strength. Finally, several types of layer interfaces were selected to be constructed in the full-scale test sections.

Piotr Jaskula, Marcin Stienss, Cezary Szydlowski, Dawid Rys
Time and Storage Dependent Effects of Bitumen—Comparison of Surface and Bulk

Bitumen is a product obtained from crude oil refinement. Its complex nature demands for a sophisticated approach to thoroughly assess it and link chemical composition, mechanical behavior and microstructure. Besides conventional mechanical testing, performance based test methods like dynamic shear rheometer (DSR) or bending beam rheometer (BBR) are gaining importance since they describe the actual viscoelastic behavior versus time and temperature. Furthermore, Fourier-Transformation-Infrared (FTIR) spectroscopy has recently become one of the most used analytical methods in bitumen research. The method give information regarding chemical composition in terms of functional groups and can distinguish between different ageing states and different kinds of modification. The presented study shows time and storage dependent effects on the surface and in the bulk of bitumen. It focuses on three main questions: (a) Is the surface and bulk affected by exposition to visible light within a timespan of up to 20 days? (b) Do the changes on the surface correlate with changes in bulk properties? (c) Does the surface of bitumen passivate, preventing further atmospheric oxidation? To answer these questions, two different unmodified binders were prepared and measured with FTIR and DSR. Half of the samples were exposed to visible light, while the others were stored in the dark at a controlled laboratory atmosphere. The results of FTIR spectroscopy show that the surface, when stored in visible light, passivates significantly with increasing storage time. When stored in the dark, no relevant changes are measured. The results from bulk (DSR) show the same trends but to a much lesser extent, compared to the surface. An overall sample storage in the dark is recommended. FTIR measurements should be conducted within an hour after preparation, while DSR measurements can be done up to one day after preparation.

Johannes Mirwald, Stefan Werkovits, Ingrid Camargo, Daniel Maschauer, Bernhard Hofko, Hinrich Grothe
Top-Down Cracking in Airfield Pavement Structures—An In-Situ Test Survey

A new type of distresses, not taken into account in the frame of the French airfield flexible pavement design method, has appeared for some years on several pavement structures: this is top-down cracking, under the pass of heavy aircraft landing gears. It is actually considered in the design methods that the cracking is supposed to initiate at the bottom of the bituminous layers, where the tensile stresses are the highest, and then opens progressively up to the surface (bottom-up cracking). This phenomenon has been observed in recent years on several flexible airfield pavements in France. Toulouse airport (ATB) noticed this type of distresses on the 14R-32L runway, which is a rigid pavement reinforced with a layer of bituminous materials. An experiment has been conducted by Toulouse airport, CEREMA, Airbus and the STAC, to study the pavement behavior and the evolution of this phenomenon. Ovalization measurements, deflection basins monitoring by means of inclinometers and vertical displacement of the concrete slabs measurements were performed under an Airbus A319 trafficking. In parallel, Heavy Weight Deflectometer (HWD) tests were carried out on several test points over underlying concrete slab center, slab edge and slab corner. A mechanical model was developed, based on a 2D finite element (FE) technique. It enables to consider either static or dynamical impulse HWD loading, and includes viscoelasticity properties for the surface bituminous materials.

Amir Sadoun, Michaël Broutin, Ichem Boulkhemair, Alexandre Duprey, Arnaud Mazars, Marc Huault
Tracking Degree of Blending Between Recycled and Virgin Binder Through Asphalt Mix Phase Angle

Performance of Reclaimed Asphalt Pavement (RAP) in a new mix depends on the degree of blending between the aged asphalt binder of the RAP and the new virgin binder. The extent of blending determines the homogeneity of the new mix and thus its performance. A recent study by ExxonMobil and University of Waterloo has indicated that silo storage improves homogeneity of RAP-containing mixes post manufacturing. Samples were collected at selected silo storage durations. Resistance to rutting, fatigue and low temperature cracking exhibited improvement. However, the complex modulus mastercurves exhibited a reduction in |E*| values at lower frequencies up to 12 h of storage, which was unexpected. In addition to lower |E*| values, the slopes of mastercurves were changing with silo storage time. Literature suggests that the slope of a log-log plot of |E*| versus frequency is an estimate of the phase angle of the material. Therefore, deriving phase angle from the mix mastercurves, the evolution of blending between RAP and virgin binder could also be tracked. Data suggests that the derived phase angle is also sensitive enough to detect the aging that would happen as a result of a prolonged silo storage or incompatible binder chemistry.

Payman Pirzadeh, Hassan Baaj
TSRST Heterogeneous Modeling for Understanding Failure Depending on Asphalt Mix Design and Experimental Conditions

The Thermal Stress Restrained Specimen Test (TSRST) is used to determine the low temperature cracking susceptibility of asphalt mixture. In this test, a specimen is subjected to a constant temperature decrease rate. Due to the prohibited thermal shrinkage, cryogenic stress is built up in the specimen. The progression of stresses imposes failure in the specimen. There is certain experimental limitation to measure the real value of the stress. This paper aims to develop the numerical approach permitting to estimate the local stress and strain value in the specimen. This approach consists of the heterogeneous multiscale modeling of the asphalt mixture. The heterogeneous scales ranging from smallest to largest are mastic, mortar and HMA (hot mix asphalt). Each scales’ length is made out of a viscoelastic matrix and an elastic aggregates skeleton. Granular skeletons are generated using a Random object modeler software or MOA (Modeleur d’Objet Aléatoire). These models correspond to a specific aggregate grading curve. Thereafter the heterogeneous geometries are imported into ABAQUS finite element code. The coupled thermal and mechanical numerical simulations are realized at different temperatures. The intensity of local stress and strain values will be compared to the ones found from the experimental measurement. The aim of this modelling is to try to understand the failure strength not depending only on the material but also on environmental parameters, cooling system, specimen size and also formulation of mixes.

Fateh Fakhari Tehrani, Christophe Petit, Joseph Absi
Understanding of Structural and Surface Tension Properties of Asphalt Model Using Molecular Dynamics Simulation

The objective of this study is to characterize the molecular structural and surface tension properties of asphalt model using molecular dynamics (MD) simulation. The previously proposed 12-component asphalt model (AAA-1) was used in the MD simulation to evaluate the surface tension and structural properties in the molecular level of asphalt at different temperatures. The calculated densities from the asphalt models were in good agreement with the reference data. The asphalt model was validated with this comparison. The surface tension was predicted from the MD models and compared with the with the pendant drop test methods. The results showed the reasonable comparison. The molecular structural properties of asphalt model mainly on the radial distribution function (RDF) was also investigated. The first peaks and the highest peaks between groups of molecules identified the most contributed atom pairs in the asphalt group models which have general agreement with references. Based on these, the proposed MD simulations provide insights to understand the molecular structural and surface tension properties of asphalt at different temperatures.

Lingyun You, Theodora Spyriouni, Qingli Dai, Zhanping You, Jaroslaw W. Drelich, Ashok Khanal
Use of Modified Reclaimed Asphalt in Warm Mixtures

Warm Mix Asphalt (WMA) has the advantage over conventional Hot Mix Asphalt (HMA) of reducing pollutant emissions and energy costs. The use of WMA technologies can be fruitfully coupled with the addition of Reclaimed Asphalt (RA) improving asphalt mixture performance. However, this aspect needs to be investigated in more detail. In this regard, this paper focused on the optimization and performance investigation of a dense graded modified asphalt mixture for wearing courses, produced with WMA technology and percentages of RA up to 25%. Two WMA mixtures with two contents of RA were prepared by using a chemical additive. The results were also compared with an HMA control mixture produced with a lower RA content. Shear gyratory compacted specimens were used for a series of laboratory tests to evaluate the performance. The study of stiffness, water sensitivity, permanent deformation and fracture characteristics pointed out that appropriately designed WMA mixtures with RA can be produced without penalizing the performance with respect to the control mixture.

G. Ferrotti, Francesco Canestrari, J. Xiaotian, Fabrizio Cardone
Use of Multiple Stress Creep Recovery Test to Evaluate Viscoelastic Properties of Asphalt Mastic

Asphalt mastic is regarded as a bonding agent within the asphalt mixture and has a significant impact on asphalt mixture performance. Multiple stress creep recovery (MSCR) test are performed in this study to evaluate the effect of filler on high-temperature performance of asphalt mastic. In addition, the creep-recovery response of asphalt mastic with a wide range of creep stress levels was modeled using the Burgers model. It was found from the non-recovery compliance and percentage recovery results obtained from the MSCR test that the addition of filler can significantly improve the elastic and recoverable response of the asphalt mastic, and hence enhances the rutting potential of asphalt mastic. The Burgers model parameters including Em, ηm, Ek and ηk were obtained for asphalt mastic with different filler contents and creep stresses. Through correlating these parameters and MSCR test indicators, it was found that the parameter ηm has the highest correlation to the MSCR test results.

Song Li, Ghim Ping Ong, Fujian Ni
Use of Recycled Asphalt Pavement (RAP) in Airport Pavements

Federal Aviation Administration (FAA) currently does not allow use of recycled asphalt pavement (RAP) on Airport Improvement Program (AIP) funded airport runway and taxiway pavement projects, and is allowed for use only in pavement shoulders. FAA’s National Airport Pavement and Materials Research Center (NAPMRC) was established to evaluate performance of new and sustainable asphalt material technologies (such as WMA, RAP, etc.) under heavy aircraft loading at high pavement temperatures. As part of Test Cycle 2 (TC2), six test lanes were constructed – four outdoors and two indoors, each encompassing three different test sections. In two indoor lanes, RAP was added to the warm mix asphalt (WMA). Lane-1 is the control section with FAA standard P401 specification hot mix asphalt (HMA). Heavy weight deflectometer (HWD) tests were performed on the constructed test lanes to characterize the pavements. Extensive laboratory tests are planned on RAP/WMA and HMA (field cores and loose mixes). The test lanes will be subjected to accelerated pavement tests (APT) using custom designed airport heavy vehicle simulator (HVS-A) to study rutting performance (at high pavement temperatures) and fatigue behavior. This paper presents construction of test lanes, asphalt mix designs (with and without RAP), results from HWD tests on test lanes with RAP/WMA, and results from laboratory tests on pavement materials..

Navneet Garg, Hasan Kazmee, Lia Ricalde
Using Linear Elastic Layer Analysis Based Method for Back-Calculating the Layer Moduli of Small Paneled Thin White Topping Pavements

In the case of rigid pavement, the cement concrete (CC) layer is assumed to be resting on a Winkler foundation defined by the modulus of subgrade reaction (k) value. So, the back-calculation of moduli for rigid pavements is mainly based on the AREA parameter and the radius of relative stiffness (l) value of the slab as calculated from the defection bowl data. In this paper an attempt has been made to back-calculate the layer moduli values of a small paneled thin white topping (SP-TWT) pavement using the linear elastic layer analysis similar to the one used for a flexible pavement. A concrete overlay with 200 mm thick CC layer of M50 grade concrete over an existing bituminous pavement with a 100 mm thick dense bituminous (DB) layer and a 450 mm thick granular layer was evaluated using FWD. The average back-calculated moduli values for CC, DB and combined lower (unbound) layers are 37800 MPa, 2500 MPa and 250 MPa respectively. The moduli values obtained by this back-calculation method are very close to the actual values found from testing the cores of CC and DB layers collected from the field. The reason for exploring this option, for back-calculation, is the presence of a sufficiently strong pavement layer system of existing flexible pavement below the CC layer with a bonded/rough interface between CC and DB layers and a near continuous surface (CC) layer with very narrow joints having an average load transfer efficiency (LTE) of 97% and a minimum value of 93%.

Venkata Joga Rao Bulusu, Sudhakar Reddy Kusam, Amarnatha Reddy Muppireddy
Validation of the Time-Temperature Superposition Principle (TTSP) in the Non-linear Domain for Bituminous Mixtures with Reclaimed Asphalt Pavement (40% RAP)

The test campaign was carried out on cylindrical samples of bituminous mixtures with 40% RAP. This percentage of RAP is still considered to be the maximum in most study cases. The generalization of the TTSP is first proposed when considering small strain domain (for strain amplitudes below about 100 µm/m). We had measured the complex Young’s modulus (E*) and complex Poisson’s ratio (ν*) during cyclic loadings, performed with ENTPE’ experimental device. The analog model 2S2P1D (2 “Springs”, 2 “Parabolic elements”, 1 “Dashpot”), developed by ENTPE, was used to simulate the three-dimensional linear viscoelastic behavior of the tested material. The 3-directional (3D) thermo-mechanical behavior is then totally characterized with a master curve (plotted at a reference temperature) and a shift factor (aT), function of the temperature. The Time-Temperature Superposition Principle (TTSP) is then verified with a good approximation. Then, we had performed specific experiments (direct tensile test) on the same material to generalize the behavior in the nonlinear domain (ε ≈ %) of the TTSP considering the 1-directional (1D) and the 3-directional (3D) thermo-mechanical behavior. The time-temperature superposition principle (TTSP) was validate with the same shift factor (aT).

Mohamed Amine Bradai, Nouffou Tapsoba, Cédric Sauzéat, Hervé Di Benedetto, Jamel Neji
Viennese Aging Procedure (VAPro): Adaption for Low-Temperature Testing

As for all organic materials, bitumen ages due to anthropogenic and natural influences. The aging process changes the properties of the material. It becomes stiffer and more brittle. This leads to a deterioration of low-temperature and fatigue performance and limits the life span of road pavements. A distinction is made between short-term aging (STA) during production and long-term aging (LTA) during service-life. For simulating aging in the laboratory on bitumen scale, RTFOT for STA and PAV for LTA are used. On asphalt mix scale, various methods have been developed in the past for either loose material or compacted specimens. Many of these methods use unrealistic boundary conditions concerning temperature and pressure, which do not occur in the field. A lately developed method, Viennese Aging Procedure (VAPro), conditions specimens at close-to-field conditions, i.e. a temperature of + 60 C and a pressure of about 0.5 bar. To accelerate aging, VAPro perfuses specimens with a gas mixture consisting of compressed air and traces of reactive oxygen species (ROS). These ROS, such as ozone (O3) or nitrogen oxides (NOX) can be found in the atmosphere as well, just in lower concentration. Due to the current layout of VAPro, only cylindrical specimens could be conditioned up until now. However, for investigating the effects of LTA on the low-temperature performance of asphalt mixtures, prismatic specimens are needed for TSRST and UTST. This paper presents the development of a new VAPro version to obtain prismatic specimens and it shows a first comparison of unaged and long-term VAPro aged specimens tested in TSRST with respective DSR results of the extracted binder. With the VAPro method at hand, asphalt mixture can be optimized regarding not only their short-term performance but also their long-term performance including relevant impacts of aging on the performance.

Daniel Maschauer, Johannes Mirwald, Bernhard Hofko, Hinrich Grothe
Viscoelastic Analysis of Top-Down Crack in Geosynthetic Reinforced Asphalt Pavements Using FEM

The Top-Down crack (TDC) initiates at the pavement surface and propagates downward. One of the major causes of TDC is due to stress resulting from the interaction between truck tires and the pavement surface. Various factors such as tire pressure have a significant effect on the tire-pavement contact area and can lead to the initiation and propagation of TDC. The reinforcement of pavement by geosynthetic can increase the resistance against cracking. However, the geosynthetic performance depends on some parameters such as their elastic modulus. A 3D finite element model utilizes to evaluate the influence of different tire pressures and geosynthetic modulus (that placed at the bottom of the asphalt layer) on TDCs and Bottom-Up cracks (BUCs) in geosynthetic reinforced and unreinforced pavements. In this study, the HMA layer was characterized as a viscoelastic material. The result shows that the variation of geosynthetic modulus has more effect on BUC than TDC. The study also indicates that the timing of the appearance of the cracks be latter as the geosynthetic modulus is increasing. It’s also found that the interval of initiate between BUC and TDC is reduced with increasing the geosynthetic modulus. In addition, the effect of variation of tire pressure on BUC is more than TDC.

Masoud Jalali, Hasan Taherkhani
Proceedings of the RILEM International Symposium on Bituminous Materials
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