Proceedings of the 9th International Conference on Maintenance and Rehabilitation of Pavements—Mairepav9

Rutting in bituminous pavements predominantly depends on the aggregate gradation. In particular, for fine graded mixtures, the aggregate gradation below 2.36 mm play a critical role since more than 60% of aggregates will pass through this sieve. The present work is focused on quantifying the rut resistance of three different fine aggregate gradations. The control gradation is the well-graded gradation used in India, and the other two gradations were obtained following Bailey method. The Bailey gradations were designed in such a way that the gradation below 2.36 mm sieve size was varied while the gradation above this sieve size was kept the same as that of the control gradation. The mixtures were fabricated using an unmodified binder (binder content kept constant at 5.4%) at 6% air voids using a shear box compactor. The influence of aggregate gradation on the creep and recovery response of bituminous mixtures was investigated at two temperatures by applying 10,000 repetitions of a repeated trapezoidal loading and recovery cycles. From the resulting residual strain curve, the Bailey mixture designed towards the coarser side below 2.36 mm sieve was found to have a higher resistance to rutting when compared to the conventional bituminous concrete-middle gradation.

Pothole repairs represent a major maintenance item in the budget of many highway agencies. Currently, there are no required specifications for patching materials. Although the appearance of potholes every spring is a major public relations concern, limited experimental work has been performed on pothole repair materials to evaluate their mechanical properties. The focus of this study is to investigate relevant mechanical properties of current pothole materials. A total of six materials consisting of both summer and winter mixtures were used in this study. Several issues were encountered during the sample preparation of cold mixtures, such as the need of significant curing to gain strength and stiffness at low temperatures. For the cold mixtures, only Indirect Tensile creep and strength testing were performed, while for the other mixtures fracture energy and toughness were also determined. Experiments were also performed to evaluate if the addition of graphene nano-platelets (GNP) to patching materials improve their properties. Based on the results, several recommendations were made to improve the durability of pothole repair materials.

There are two common deficiencies of the existing cold asphalt mixtures, one is the contradiction between workability or storage and strength, and the other is the problem of low initial strength after paving. In order to solve the problems, new polymer modified patching materials with dense gradation (PADG mixtures) are recommended for durable pothole repair in cold-wet weather, based on microcapsule technology and reinforcement action. In this paper, laboratory test and field investigation were performed to assess the performance of PADG mixtures, compared with dense graded cold mixtures (DG mixtures) and open graded cold mixtures (OG mixtures). It showed that the PADG mixtures solved the contradiction between workability, storability and strength of cold mixtures, and had better cohesion, stability, freeze-thaw resistance and durability in low temperature and wet conditions. Besides, the field survey over 13 months indicated that the pothole patches using PADG mixtures met the requirements of traffic safety and ride-ability. Therefore, combined with laboratory and field text results, it can be concluded that PADG mixtures are applicable to durable maintenance in adverse conditions of cold-wet weather.

The stabilisation of granular pavement materials and/or underlying soils is accepted practice in Australasia (i.e. Australia and New Zealand). Stabilisation in this context involves the mechanical introduction of reactive agents, typically lime, cement and foamed bitumen. The reuse/recycling of aged existing pavement materials is imperative for sustainable management of finite resources. Reduction in aggregate availability has hastened the need for development of insitu stabilisation to rehabilitate the pavement alongside other performance gains. Hiway Group have commissioned laboratory research and undertaken extensive field trials in partnership with industry and academic partners to lead industry adoption and confidence in sustainable recycling. This paper will outline a variety of proven approaches ranging from hot in-place asphalt recycling through aggregate stabilisation treatments employing waste materials such as ground steel slag to innovative processes to mitigate and control deleterious subgrade soils and low ground pressure fill drying methodologies. Case studies such as exhuming 30+ year-old pavements to evaluate durability of lime stabilised layers will be outlined through to recent research and field trials that successfully incorporate substantial proportions of waste plastic, glass, steel slag and concrete blended recycled aggregates. Examples of structural benefits will be detailed that have been monitored to substantiate performance and calibrate design parameters.

Warm mix asphalts (WMAs) have gained a widespread popularity as they have reduced emissions due to lower production temperature compared to that of traditional hot mix asphalt (HMA). In Iraq, such asphalt mixture is completely new while no project of WMA has constructed in the field so far although there is a huge demand to either re-construct or construct new highways. One of the considerations that should be taken into account in this regard is to get the advantages of installing WMA in Iraq. The aim of this study is to produce a warm mix asphalt using foaming additive, Zeolite, in both types natural and synthetic. The production temperatures of WMAs were at three levels 140, 130 and 120 °C while the traditional HMA was produced at 160 °C. This study includes producing HMA and WMAs from Iraqi materials, where one binder grade (40/50 pen) from one sources, it is Durah with one type of aggregate, limestone. Hydrated lime was also used as anti-stripping additive to study its effect on improving moisture damage of WMA produced at lower temperature. To study those properties, two techniques were used Marshall properties and Indirect Tensile test. The results showed there is no significant difference between the performances of WMAs compared to that of HMA taking in account level of reduction in the production temperature compared to that of traditional hot mix asphalt. Furthermore, the result of Indirect Tensile Strength ITS has shown the enhancement in moisture susceptibility of warm mix when hydrated lime was used.

The use of reclaimed asphalt (RA) in road pavements is continuously gaining interest thanks to the technical, economic and environmental advantages guaranteed by such sustainable practice. Cold recycling techniques compared to traditional asphalt mixes allow a significant reduction of energy, fume emissions, use of natural resources, etc. In this perspective, the Task Group 1 on “Cold Recycling” of the RILEM Technical Committee on “Asphalt Pavement Recycling” (TC 264-RAP) launched an interlaboratory test program (ITP) aimed at ensuring a better understanding for cold recycled mixtures. The paper presents the results collected by a restricted group of the participating laboratories testing cement-bitumen treated materials that included a single RA source and prepared with foamed bitumen. Gyratory compacted specimens were used to evaluate the influence of curing (free, partial or restricted-surface drying for 14 days at 40 °C at a relative humidity of 55 ± 5%). Stiffness was evaluated as a function of the curing stage and the corresponding water loss; strength was tested after 14 days of curing testing specimens in both dry and wet conditions to also determine the water sensitivity. As expected, the different curing conditions clearly influenced the rate of water loss of tested samples with clear effects on mechanical properties and durability.

Cold asphalt patching mixtures are widely employed in pavement maintenance operations due to their technical and economical effectiveness. However, their selection is seldom based on the results of laboratory characterization tests, since there are no standard procedures which are recognized by the international community for such a purpose. The investigation described in this paper focused on the evaluation of the strength and stiffness properties of several cold asphalt patching products which were subjected to analysis in two characteristic compaction states: low compaction, as achieved after placement in the field, and high compaction, as reached under the action of traffic loads. Mechanical characteristics evaluated in the laboratory included indirect tensile strength, California Bearing Ratio, resilient modulus and quick shear strength. Analysis of the obtained results highlighted the existence of significant differences between the various products which were explained by referring to their composition and curing behavior.

The long-life pavements that last longer than 50 years without major structural rehabilitation and require only periodic surface renewal due to surficial distresses are known to have relatively low life cycle cost. The enhanced performances of such pavements (also known as perpetual pavements) are due to many factors such as improved structural design, better materials and construction practices. In Michigan, several long-life pavement sections were constructed in response to the Public Act 175 (2015) and the Roads Innovation Task Force (RITF) Report. The objective of this study was to evaluate the fatigue performance of one of the long-life pilot projects sections (US-131) and compare it with a standard design in Michigan. A new mechanistic-empirical analysis software (MEAPA) was used to predict the long-term performance of the pavements included in the study. The critical strains for bottom-up and top-down cracking, fatigue life (i.e., number of cycles to failure (Nf)) and predicted magnitudes of bottom-up and top-down cracking were compared. Even though it was observed that the long-life structure is expected to perform better than the standard section in terms of fatigue cracking, both sections are expected to perform well over 30-year design life.

Laboratory tests and field investigations show promising results of structural performance of warm mix asphalt (WMA). Also, the lower environmental burdens and fuel requirement in WMA production increase sustainability in the asphalt industry. However, there are challenges that significantly affect WMA performance and marketing in the future. In this paper, all these challenges are discussed, and the trend of WMA technology is evaluated. The statistics indicate that the energy market plays a pivotal role in enthusiasm for WMA. Lastly, WMA requires further investigations to meet requirements of post-modern pavement, as a new concept of pavement design in the 21st century.

Low volume roads (LVRs) play a pivotal role in the economic development of rural areas especially by providing connectivity for the communities to access markets, education and social needs in an efficient manner. They serve as the link between the local road network to the arterial and collector road network designed at providing accessibility to residential, agricultural or industrial areas. Lack of funding, subjective and ad hoc decision making has resulted in an inefficent utilization of resources in the local road agencies. Lack of a sound analytical process is a major impediment to maintain these roads in cost effective manner under the resource constraints prevalent. Existing pavement management systems (PMS) require extensive data collection and complex analysis processes, which makes them impractical to be deployed in local agencies. The core attributes of the proposed system are, reduced the data requirements, simplified the analytical tools and allowing users to customize considering the resource constraints. In this study, a relationship between International Roughness Index (IRI) and relevant distresses for LVR is established and based on that cost estimation model is developed for distress repair. Furthermore, the strategy which provide maximum condition for preventive maintenance is found by using decision tree approach in the network level optimization. A case study illustrated that the use of proposed PMS provides better overall network condition with compare to conventional decision making for same budget level.

Road asset management (RAM) is a systematic approach to maintain road network at sufficient functionality level in order to provide desirable level of services. Various strategies can be implemented within RAM but only proactive strategy ensures sustainable, optimal, and cost-effective decisions. One of the variations of the proactive strategy is reliability-centered maintenance (RCM). Integral part of the RCM framework are so called P-F curves that allow to knowingly consider the potential failure and loss of functionality of road asset. While this is not entirely new concept as comparing to models used for pavement performance, P-F curves emphasize critical stages of the development of pavement damage and concurrent continuous increase in probability of functional failure. This paper discusses several aspects of different strategies in maintenance management and associated deterioration models together with P-F curves highlighting the need for continuous improvement of processes involved in decision-making as well as verification of effectiveness and efficiency of actions applied onto road network.

Life cycle assessment (LCA) and life cycle cost analysis (LCCA) are the main pillars of pavement sustainability. LCA addresses environmental impacts of a pavement structure, and LCCA addresses life cycle costs. While both techniques go hand in hand with transportation agencies’ decision making, they are usually used separately because there are no tools or methodologies that consider both under the same framework. This study introduces a LCCA add-on to a LCA tool developed by the Illinois Center for Transportation (ICT). The tool analyzes all pavement life stages, namely, construction and materials, maintenance, use and end of life. With the new add-on, the tool can calculate agency costs and user costs associated with both work zone and normal operating conditions as well as global warming potential and energy consumption. The developed tool makes the pay item framework easier to use for agencies and contractors. At the end, a case study is presented to illustrate the tool’s capabilities.

By maintaining Uri road infrastructure, the cantonal road agency is ensuring safety, reliability and driving comfort on the roads for passengers and freight transport and thus, contributes to economic and social added value. The canton Uri has one of the first road agencies with an infrastructure division responsible for all road infrastructure objects. This includes inventory, condition inspections, maintenance planning and necessary data management. Uri maintenance and rehabilitation processes for pavements are embedded in a holistic road asset management process supported by an essential IT infrastructure.One of the key applications is a flexible decision support tool “infFaros Uri” which was customized and developed together with the infrastructure division of canton Uri to meet their needs. infFaros can handle road sections and bridge together allowing synergy effects and corridor planning. It supports various methodologies including probabilistic and deterministic deterioration, cost/benefit and cost/effectiveness decision-making as well as consideration of four-year maintenance and rehabilitation plan and evaluation of its impact. By linking short- and long-term maintenance and rehabilitation planning using existing cantonal transportation data complex questions can be answered and decision making can be efficiently supported by scenario comparisons. infFaros is a modern web-based application. The paper presents both the technical background of the software and use of it to support four-year maintenance and rehabilitation planning within new Uri road asset management process.

Reducing rolling resistance of pavement surfaces contributes to improved fuel efficiency for automobiles and reduced CO2 emissions in exhaust gases. The authors have developed actual low-rolling-resistance asphalt pavements and shown that such pavements can reduce CO2 emissions from automobiles by 1.3–6.6% through a driving test. In contrast, in order to evaluate the CO2 emissions of pavement technologies, which will contribute to the realizing of a sustainable society in the future, it is important to conduct the life cycle assessment of these pavement technologies, including CO2 emissions, due to the production and transportation of pavement materials, pavement construction work, and the recycling as well as the reconstruction of pavements. Thus, for the purpose of clarifying the environmental improvement effect of low-rolling-resistance asphalt pavements, this research paper reports on the life cycle CO2 emissions assessment conducted for studying not only CO2 emissions due to the production and transportation of pavement materials, pavement construction work, reconstruction but also reductions in CO2 emissions through the improvement in fuel efficiency of automobiles by the low-rolling-resistance asphalt pavements. As a result of the life cycle CO2 emissions assessment, it is clarified that the low-rolling-resistance asphalt pavements can reduce CO2 emissions by 70% compared to conventional pavement (porous asphalt pavement).

Weigh-in-Motion (WIM) is a primary technology used for monitoring and collecting vehicle weights and axle loads on roadways. Highway agencies collect WIM data for many reasons, including highway planning, pavement and bridge design, freight movement studies, motor vehicle enforcement, and regulatory studies. The process of weighing vehicles in motion estimates static truck weight by the wheel [single or tandem axles] or gross vehicle weight (GVW) as vehicles drive over sensors installed in a roadway or under a bridge. Two primary protocols are currently used across the globe to assess the accuracy of a WIM system, (a) ASTM E1318-09 and (b) European WIM accuracy protocols. The quality and accuracy of the data largely depend on the characteristics of the WIM equipment, calibration/validation, site characteristics, and data reporting. This paper compares the WIM sensor accuracies in the LTPP data for both protocols. The results show that there are minor differences in calculated accuracies.

The mechanistic-empirical pavement design guide (AASHTOWARE Pavement-ME) incorporates mechanistic models to estimate stresses, strains, and deformations in pavement layers using site-specific climatic, material, and traffic characteristics. These traffic characteristics include monthly adjustment factors (MAF), hourly distribution factors (HDF), vehicle class distributions (VCD), axle groups per vehicle (AGPV), and axle load distributions for different axle configurations. Site-specific traffic inputs (Level 1) were generated for each of the 41 WIM sites after extensive QC checks. The averages from nearby sites (regional) with similar traffic characteristics (groups or clusters) can be used as Level 2 data or Level 3 data when Level 1 data are unavailable. Multiple approaches were used to develop Level 2 and Level 3 traffic input levels. These developed traffic inputs at different levels need to be updated every few years due to several reasons, including the change in land use nearby the WIM locations, economic conditions resulting in the change in traffic patterns. Equations were developed to identify these changes in traffic patterns that would cause significant changes in design lives. Once these patterns are identified, the traffic inputs can be updated so that the pavement sections would not be over-designed or under-designed.

With the increasing traffic loads on National highways of India, pavements are deteriorating at a faster rate leading to premature failure. In addition to this lack of scientific road management system leads to lower levels of serviceability and unreliable road network in the long term. Therefore, in order to maintain the highway network in good condition the road administration should focus on long lasting and economical road maintenance solutions. The research study focuses on the development of road management system for high volume roads using calibrated Highway Development & Management (HDM-4) model. Long-term pavement performance under various maintenance strategies has been measured in terms of roughness progression using HDM model. Genetic Programming (GP) system has been configured to develop four distress prediction models i.e., roughness, ravelling, cracking and rutting. Adequacy of GP models has been measured using simple linear regression analysis. Statistical significance of roughness model has been evaluated using student’s t-test. Variability in the output results of the two deterministic models i.e., HDM and GP has been computed by comparing the difference between predicted and observed roughness behaviour. Prediction models play a crucial role in development of Road Maintenance and Management System (RMMS) for systematic technical as well as economic appraisal of road projects. Future modelling of pavement behaviour related to various maintenance activities will assist the highway planners and road agencies in timely monitoring and conditioning of roads by adopting suitable management framework.

Inacceptable capability and durability of joint sealing systems but also inadequate traffic performance (noise emission; overrolling comfort) up to traffic safety aspects reflect the still enormous demand for data-based description of concrete pavements performance under heavy loading conditions. Especially the deformation behavior of concrete pavement slabs in the joint region in consideration of new pavement construction types and improved concrete mixtures meanwhile established but also under the steeply rising traffic loads is not sufficiently explored. To create a data basis for advanced design rules, evaluation methods and product standards - and with it to improve quality, durability and finally sustainability of pavements - an innovative 3-D sensor system SENSO JOINT adapted to german roadworking requirements and suitable for heavy-duty operating conditions was developed. The contribution introduced describes the development of an extensive technical solution based on the analysis of decisive loads, interactions and boundary conditions. Based on calibration data, results of laboratory testing and finally field-testing on different concrete pavement construction types the outcome of a multi-level evaluation process shall introduce the potential of the new sensor system.

The service life of a road is to great extent controlled by the performance of the unbound layers. Assessing the constitutive behavior of these layers is thus imperative for a sustainable pavement design. Adequate description and measurement of unbound materials resistance to aggregate crushing is an issue, in terms of the measured response coupled to intrinsic properties of the aggregates and unbound materials gradation. In this study, a new Discrete Element Method (DEM)—based model is developed to investigate aggregate damage in unbound road materials. In order to get better insight into micro-mechanics of aggregate crushing, the developed model incorporates granular mechanics-based particle contact and damage laws. By numerical analysis with the DEM, several unbound granular materials have been examined investigating the effect of the materials gradation and aggregates toughness properties on their performance in crushing tests. The capability of the model to capture the effect of unbound material properties on its crushing performance, is evaluated based on comparison with experimental findings.

This paper describes a piezoelectric energy harvester (PEH) that uses PZT or lead zirconate titanate (Pb[Zr(x)Ti(1 − x)]O3) elements to convert mechanical energy from moving vehicles to electricity. The PEH consists of a rectangular metal housing supported by four PZT stacks located at its corners. It is sized to capture the right wheel path of the weaving traffic. Each PZT stack consists of six PZT cylindrical elements connected in parallel. Extensive laboratory tests were performed to properly characterize and model the stacks. An electromechanical model of the stacks was developed to translate its mechanical properties to electrical properties. This model was implemented into Matlab/Simulink in order to optimize the power harvesting circuitry. The output power depends on the applied stress and the loading frequency. The power output of one of the PZT stacks is in the order of 10 mW and 1.4 W for a car axle and a truck axle, respectively. In addition to generating power, the PZT stacks can be used as axle load sensors by utilizing the output voltage to back calculate the stress using the developed model.

Warm Mix Asphalt (WMA) technologies are becoming popular due to their ability to reduce mixing and compaction temperatures compared to the conventional hot mix asphalts (HMAs), with remarkable advantages of environment and costs. Moreover, WMA is considered as one of the most promising technology for increasing the re-use of Reclaimed Asphalt (RA) within the mixture although its effectiveness in recycling issues require more dedicated research activities. This paper describes a laboratory investigation aimed at optimizing a dense graded asphalt mixture for wearing course, produced with WMA technology and including up to 30% of RA. WMA mixtures were prepared by using two contents of a plain bitumen, two contents of RA and one chemical additive. A recycled HMA containing lower RA content, according to technical specifications currently applied in Italy, was selected as reference mixture. Strength and stiffness properties, water sensitivity, rutting and cracking resistance were investigated on shear gyratory compacted specimens. The result analysis on stiffness, rutting and fracture properties indicated the possibility to produce suitable WMA mixtures with higher RA contents without penalizing their performance compared to the reference one.

As the existing expressways age, structural damage including bottom-up fatigue cracking occurs in the asphalt pavement of expressways in Japan. Therefore, a detailed field study was conducted to identify the damage status of the inner pavement under heavy traffic, and the weaknesses of the existing pavement were revealed. This paper proposes new ideas that can effectively contribute to the creation of exceptionally durable pavement.

This research study focuses on results from laboratory tests on Warm-Mix Asphalt (WMA) mixtures prepared using two methods—Evotherm® 3G additive and “The Foamer” device by Pavement Technology Inc.—with varying percentages of Reclaimed Asphalt Pavement (RAP). The resulting mixture combinations were evaluated in the laboratory for their performance characteristics and compared with a control Hot Mix Asphalt (HMA) with the same amount of RAP. Tensile Strength Ratio (TSR) was used to evaluate the moisture susceptibility. Dynamic modulus (|E*|) tests were conducted to obtain master curves for all mixtures. They were also used to compute the |E*| Stiffness Ratio, i.e. the ratio of dynamic modulus values of moisture-conditioned specimens to that of unconditioned specimens, analogous to the Tensile Strength Ratio. Only the Foamer mixture with the highest amount of RAP did not pass the TSR test. No correlation was found between TSR and |E*| Stiffness Ratio. Despite lower production temperatures, WMA-RAP mixtures show similar |E*| behavior to HMA-RAP. Thus, WMA technologies can be used to help incorporate higher amounts of RAP rather than using a softer virgin binder grade in high-RAP HMA.

Roads are the essential transport modal worldwide since it facilitates the movement of people and goods. Therefore, it is a concern to reduce costs and be sustainable for maintenance and rehabilitation. So self-healing has been studied. The self-healing properties of the asphalt mixtures had already been studied. It is previously known that asphalt mixtures can recover its strength entirely autonomously, or just with a small external stimulus such as heat. The main objective of this paper is to study the recovery of asphalt mixtures only by heating them. After heating, the complex modulus and fatigue resistance were assessed, and the capacity of recovering each mixture was evaluated. AC14 asphalt mixtures (14-mm maximum aggregate size) were produced with conventional bitumen, varying the asphalt content, namely 3.7, 4.0, 4.3, and 4.6%. Fatigued beams were heated from 90–150 °C after fatigue failure. Fatigue resistance tests were conducted at 20 °C temperature and 10 Hz frequency. It was verified that certain conditions of the heating process allow the mixtures to recover some of the initial resistance. Also, it was noted that the higher the temperature and the percentage of asphalt content, it was higher the values of complex modulus and fatigue resistance as well.

Surface-initiated cracking with top-down propagation (TDC) is one of the most frequent and important failure modes of asphalt pavements. In order to achieve long-lasting pavements, it is necessary to control the evolution of these cracks and so repair them before they become deeper and deteriorate the lower layers. Self-healing of asphalt mixtures is possible if the temperature is raised near the softening point of the binder, thus allowing the fusion of the cracks. For this purpose, conductive additions can be used to promote induction heating when applying electromagnetic fields. This laboratory work shows the self-healing results of TDC on bituminous mixtures after microwaves exposure. Different mixtures (semi-dense asphalt concrete AC-S, gap-graded asphalt concrete for very thin layers AC-VTL and porous asphalt PA) with diverse types, sizes and proportions of metallic additions from industrial waste were tested. Three aspects were studied: (a) analysis of the type, particle size and content of each addition on the heating speed; (b) temperature increase with the specific energy; (c) monitoring of the healing process by using ultrasounds. Microwave exposure allowed the total closure of cracks using an industrial waste, with reduced exposure times and applied energies. The results validate the microwave healing capacity, as well as the use of ultrasounds for tracking the crack depth.

Moisture damage is mainly characterized by the loss of adhesion between asphalt binder and aggregate and the loss of cohesion within the asphalt binder. The binder holds the aggregates firmly together and acts as a sealant against moisture ingress. Additives are added to enhance the performance-related properties of asphalt mixtures under different climatic and environmental conditions. In this study, warm mix additive was used to modify the asphalt binder PG-64. The asphalt binder modified with chemical surfactant based additive was tested against pull-off tension force using limestone aggregate substrates. The specimens were conditioned using accelerated laboratory vacuum saturator (ALVS). The results showed that the percent adhesion failure increased when specimens were subjected to moisture conditioning. Furthermore, adhesion failure also increased with binder aging and enhanced further when the binders were long term aged.

In today’s time, plastic materials (which otherwise pose great threat to environment), can be alternatively and smartly utilized in civil engineering as a soil stabilizing material (apart from the more traditional cement and lime) to achieve economy and reduce waste impact on environment. In present study, effect of addition of plastic fibres (shredded wrappers) on the strength characteristics of flexible pavements have been studied. Available literature after been reviewed, and then experiments were performed to compute the liquid limit, plastic limit and plasticity index of soil to categorize type of soil. OMC (Optimum moisture content) and MDD (Maximum dry density) were computed at various plastic contents (by % of dry weight of soil). The CBR (California bearing ratio) test has been performed at different percentage plastic contents. The maximum value of CBR was obtained as 4.01% at 1.5% plastic content. The design of pavement section have been carried out for different traffic volumes to find the most efficient and economical traffic condition for which this method could be most advantageous. Thickness of pavement for each layer (as per CBR corresponding to 0 and 1.5% plastic content) was determined using IRC-37:2018 design plates. The theoretical values of vertical compressive and horizontal tensile strains at critical locations have been determined. The theoretical value of modulus of elasticity (with 0 and 1.5% optimum plastic addition) were calculated using IRC 37:2018. Trial sections filled with virgin soil and reinforced soil at various percentages of waste plastic content were compacted manually to 250 mm thickness and the subgrade modulus were determined experimentally by using a Light Weight Deflectometer. The theoretical and experimental modulus values were compared, and the most optimized pavement thickness has been designed with IIT PAVE.

In recent decades, modifying the binder with various additives for improving its behavior has been very noticeable by researchers. Crumb rubber is one of the additives which increases the rutting resistance of binder. The main objective of this study is to identify the factors affecting the resistance characteristics of binder regarding rutting and modeling its behavior at 64 °C using crumb rubber. For this purpose, one of the Design of Experiments (DoE) methods, i.e. Response Surface Methodology (RSM) was utilized taking into account four factors, including mixing temperature, mixing time, mixing speed and content percentage (by weight) of crumb rubber, as well as one response, rutting parameter. As a result, 30 modified binder samples were produced and Dynamic Shear Rheometer (DSR) test was conducted on the samples. Modeling was done and performance of the model was evaluated. Results show that developed model has a good prediction accuracy and the content of crumb rubber is more effective factor rather than other factors and the interaction of them. In addition, in a certain content percentage of crumb rubber, considering the mixing temperature and mixing speed at a low level and mixing time at a high level, the maximum rutting parameter could be achieved.

This paper presents a unique self-healing system for asphalt pavement which employs compartmented calcium-alginate fibres encapsulating an asphalt binder healing agent (rejuvenator). This system presents a novel method of incorporating rejuvenators into asphalt pavement mixtures. The compartmented fibres are used to distribute the rejuvenator throughout the pavement mixture, thereby overcoming some of the problems associated with alternate asphalt pavement healing methods, i.e., spherical capsules and hollow fibres. The healing system performance, when embedded in Porous Asphalt (PA) mix was tested by employing: (i) Indirect Tensile Stiffness and Strength test (ii) 4 Point Bending Fatigue test. The Semi Circular Bend (SCB) test was adopted to study crack propagation and its closure (healing) in an asphalt mix. The findings demonstrate that compartmented alginate fibres have capacity to survive asphalt mixing and compaction process. The fibres can efficiently repair damage (close the cracks), increase asphalt mix stiffness and strength. However, when the asphalt mix is subjected to fatigue loading the system does not significantly improve healing properties of the asphalt mix. Nevertheless, the findings indicate that, with further enhancement, compartmented calcium alginate fibres may present a promising new approach for the development of self-healing asphalt pavement systems.

Due to economic and environmental benefits, Recycled Asphalt Pavement (RAP) has been commonly used in the asphalt pavement construction. However, the capability of existed mixing plants to incorporate a high percentage of RAP restrict the use of a high RA content. In this study, the possibility of recycling a RA binder content of 80% is experimentally investigated. First, an unmodified 50/70 binder is selected as the reference material; then, an extracted RA binder was blended with the optimal rejuvenator, and the rejuvenator content determined based on the penetration test to restore the original penetration value close to the reference material. Next, both materials are artificially aged to short- and long-term aging conditions. Rheological tests are performed with the Dynamic Shear Rheometer (DSR) and the Bending Beam Rheometer (BBR). Finally, the experimental results are used to evaluate the performance property of virgin and rejuvenated asphalt binders under different aging levels. Results indicate that the properties of the blend of RA and virgin binder can be only partially restored by the action of the rejuvenator.

Environmental protection is also pursued by promoting the saving of oil reserves and the proper management of waste through a circular economy. Following this objective, the present study encourages the use of recycled and by-product materials for the production of bituminous binders. The powdered rubber (R) from end-of-life tyres and the re-refined engine oil bottom (REOB), i.e. the by-product of refining mineral waste oils, were used to replace a certain amount of standard bitumen. The experimental program aims to characterize the interaction between R and REOB in order to use them as virgin bitumen extenders. The multiple variables of the production process that may affect the R-REOB blends and in turn the binders’ final properties were evaluated. The R-REOB mixes were prepared by varying the type of REOB, the R content and the mixing temperature. The rheological analysis was performed by means of dynamic shear rheometer (DSR) tests with the aim to define the variables that strongly influence the response of the R-REOB compound. As a result of this preliminary study, the second phase will focus on extended bitumens that will be prepared considering some of the studied extenders.

Waste concrete is one of the most highly produced types of waste in the urban environment and finding a means for its re-use is crucial to making infrastructure sustainable. Semi-Dense Asphalt (SDA) is a type of asphalt mixture, which is commonly used in Switzerland to reduce pavement noise. This study examined the use of various fractions of Recycled Concrete Aggregates (RCA) into SDA mixtures. The virgin aggregates were replaced by RCA in selected fractions of 2/4 and 0.125/2 at 100% and 50%, with only one fraction being replaced for any single mixture. The mixtures were evaluated by volumetrics, indirect tensile strength and water sensitivity (EN 12697-12) in order to assess the effects of each RCA fraction. The results showed that RCA coarse aggregates absorb high amounts of binder, which is not the case for the RCA sand. The ITS results showed increase peak load for the RCA replacement samples but also increased brittleness. The ITSR% was similar to the control for lower fraction of RCA replacement samples, but significantly lower with higher replacement.

The study reported here aims to precise the combined effect of warm mix processes and multi-recycling on the main criteria of the French asphalt mix design method. Asphalt concretes (AC) 0/10 mm are produced at a semi-industrial scale for a combination of 3 recycling cycles, 3 production processes (hot, warm with additive and warm with foamed bitumen) and 2 recycling rates (40 and 70%). This combination is completed by a cycle without recycling for the 3 production processes, giving a total of 21 modalities. Compactibility, water sensitivity, stiffness modulus and fatigue tests are performed on the 21 AC produced. A principal component analysis (PCA) is then performed on the set of data obtained to extract the main trends.No drastic change is detected in the properties as all the AC produced comply with the French requirements for water sensitivity, stiffness modulus and fatigue. The main significant trends observed through PCA are a decrease of the workability and the compactibility and an increase of the water sensitivity with reclaimed asphalt (RA) addition and multi-recycling. It is also observed that high recycling rate (70% RA) tends to increase the constant of the fatigue line but also its slope, reflecting an increased sensitivity of the fatigue resistance to the strain level.

Cold recycled asphalt mixtures (CRAM) are sustainable solutions for maintenance and rehabilitation of road pavements. Notwithstanding the environmental benefits, CRAM may exhibit lower performances compared to traditional hot mix asphalt. Besides, CRAM require a curing period to reach their long-term properties, and thus, they are usually employed in base courses. This work investigates the mechanical behaviour of CRAM with bitumen emulsion and high strength cement to verify if they are suitable for binder courses. Six CRAM were produced using 80% of reclaimed asphalt, modified emulsion and two high strength cement: sulfo-aluminous and Portland-slag cement. For comparison, two additional mixtures were produced using traditional emulsion. The CRAM had an emulsion content of 4.2% or 5.0%, and residual bitumen to cement ratio of 1.0 or 1.2. After curing periods from 6 h to 1 year, the indirect tensile stiffness modulus (ITSM) and indirect tensile strength (ITS) were assessed. Their thermal sensitivity was evaluated as well, measuring ITSM at different temperatures. Results indicate that high strength cement leads to satisfactory mechanical behaviour in the long-term. Compared to Portland-slag cement, sulfo-aluminous cement increases the rate of development of ITS and ITSM in the early stage of about 50% and 25%, respectively.

This study evaluated the mixture of Hot Mix Asphalt (HMA) containing Electric Arc Furnace (EAF) slag and Reclaim Asphalt Pavement (RAP). The first design contains 30% EAF slag and the second hybrid design contains mixed EAF slag and RAP, each 20%. Compared to the control group, EAF slag and EAF slag + RAP have lower stability in Marshall Test, but perform better in rutting resistance and moisture sensitivity. In the second part of the study, there are three designs mixture on the test road. The test piece was drilled for the Hamburg wheel test (HWT) after paving, showing better creep performance on EAF; hybrid EAF slag + RAP showed the best stripping results. On the Stripping Inflection Point (SIP), EAF slag has better results of the corresponding ruts and times. Besides, EAF slag + RAP does not show asphalt stripping. EAF slag and EAF slag + RAP have similar results from the performance of the rut depth of 12.5 mm. From the above study, adding one or even mixing two kinds of recycled materials can still meet the design requirements, and it is worthwhile for further study of different recycled materials using in the pavement.

This study compared the performance of rutting and fatigue resistance of asphalt mastics and mixes prepared with waste fillers (limestone sludge (LS) and glass powder (GP)) to the conventional stone dust (SD) filler counterparts. Physical and chemical properties of fillers were determined. Asphalt concrete mixes were prepared at three different filler proportions (4, 5.5 and 7%) and their optimum asphalt contents (OAC) were determined. The asphalt mastics for all mixes were prepared at their respective filler binder ratio and their rutting and fatigue analysis was conducted using multiple stress creep and recovery (MSCR) and linear amplitude sweep (LAS) analyses. At their OAC’s, indirect tensile strength, Marshall quotient, resilient modulus and fatigue lives of asphalt concrete mixes were analyzed. Both LS and GP mixes displayed superior rutting resistance and fatigue resistance than conventional mixes due to their tendency to display higher stiffening and crack pinning behavior caused by the finer particle size and lower specific gravity. This trend was more or less similar in the case of mastics as well. Overall, mastics and mixes prepared with GP and LS displayed superior performance than standard SD filler and hence they could be utilized as alternative fillers.

Environmental concerns are conditioning all processes that use hydrocarbons products, building awareness for a more sustainable environment through products called bio. In this scenario, it is also the production of bitumen, where the substitution of part of the bitumen by bioproducts is a contribution to the sustainability of the environment. Bio-oil, which is currently used for burning with the purpose of producing energy, can be used to modify the bitumen, producing a bio-asphalt. Trying to contribute to sustainable development, this paper presents an initial analysis of the feasibility of using bio-oil in the production of pavement bitumen. One base bitumen was used, namely, residue of asphalt. The tests were carried out for physical characterization of the bio-bitumen, namely the penetration, the softening point, and the Brookfield viscosity, as well as its rheological characterization in which the dynamic shear modulus and the phase angle were evaluated. The bio-oil content, by weight, varied from 2 to 10% for the residue of asphalt. It was verified that the base bitumen, namely the residue of asphalt, can be softened significantly due to the bio-oil. The bio-oil content of 6% added to the residue of asphalt produces a bio-binder with physical behaviour similar to a conventional 35/50 pen asphalt.

This research study evaluated the characteristics of crumb rubber modified (CRM) asphalt binders produced with neat bitumen. Two different percentages of crumb rubber (CR); 10 and 15% and one bitumen type with penetration (Pen) grade 60/70 were evaluated. The evaluated characteristics included viscosity, ductility, Penetration, and softening point of the produced asphalt binders. Additionally, images obtained by Scanning Electron Microscopy (SEM) were used to investigate the surface topographies and compositions of the neat and produced CRM binders. SEM images were used to check for separation between the crumb rubber and the bitumen. Furthermore, the Multiple Stress Creep Recovery (MSCR) test was conducted in order to evaluate the rheological properties of the produced CRM asphalt binders. MSCR results showed that the addition of CR to the neat bitumen significantly improved the performance grade (PG) of the produced binder as per AASHTO M332 standards. The traffic loading level for both 10 and 15% CRM asphalt binder increased from “Heavy” for neat to “Extreme” level. Both 10 and 15% CRM binders passed local Kuwaiti requirement for modified binders. Based on AASHTO M332 standards, the 15% CRM binder is said to be not modified with an elastomeric polymer, unlike the 10% CRM binder, which was found to be modified with an acceptable elastomeric polymer. This can be attributed to the lack of full blending between the CR particles and the binder’s bulk due to the increase in CR percentage as shown by the SEM images

Recycling of Construction and Demolition Waste (CDW) with the purpose of re-using these in construction projects has substantial benefits for the environment and for conservation of natural aggregates resources. Recycled Concrete Aggregates (RCA) that are derived from buildings, concrete structures or distressed PCC pavements can be used in various applications. This paper reports results of the experimental study on the application of demolished concrete aggregates in preparing Hot Mix Asphalt (HMA). RCA materials were used both in their original form; and, treated before that these were added to HMA mix. Two treatment methods were applied to coarse RCA materials. Treatments were consisted of; one, a two-stage treatment of RCAs, using acid and a pozzolan material (calcium metasilicate, named Wollastonite); two, applying hydrated lime solution to RCAs. Physical and mechanical characteristics of the treated/untreated RCAs were determined. Various asphalt mixtures with different amounts of RCAs were prepared. Moisture susceptibility and fracture properties of mixes were determined, using Indirect Tensile and Semi-Circular Bending (SCB) testing methods. Results indicated that although treating RCAs might require more effort in production processing, significant benefits will result in reducing moisture susceptibility and increasing fracture resistance of HMA mixes containing treated RCA materials. It was also found that replacing natural aggregates with RCA, improved fracture properties of asphalt mixes appreciably.

Recycling waste materials is a key issue in sustainable road pavements construction. This is the reason why the efforts of the scientific and technical community are addressed in studying sustainable solutions for producing bituminous mixtures. As a result of these efforts, the use of Reclaimed Asphalt (RA) is becoming a standard practice, even if in Italy the use of RA is limited to a certain content. So the increase of RA content appears to be the new border of the research in this field. At the same time, the scientific literature demonstrates that other recycled materials, such as Steel Slags Aggregates (SSAs), can be used with satisfactory results. To go a step further, the research herein described focused on the evaluation, at the laboratory scale, of the effects of both high amounts of RA (from 15 up to 60% by weight) and RA plus SSAs (from 55 up to 71% by weight). Compaction properties, volumetric characteristics and mechanical performances were investigated. Even if the obtained results are at the laboratory scale and keeping in mind that the research needs an on-site validation, the investigated mixtures seem to be promising for a future development of bituminous mixtures with high environmental compatibility.

The current paper investigates the characteristic properties of three crumb rubber modified bitumens (CRMBs) of Greek origin with different crumb rubber (CR) contents, i.e. 5, 10 and 15%, before and after aging. The virgin bitumen used for the production of the three modified bituminous binders, was a 50/70 paving grade bitumen. The characteristic properties examined were penetration, softening point, dynamic viscosity, storage stability and force ductility. Temperature sweep test was also performed, and certain rheological properties were determined. Additionally, results of characteristic and rheological properties of CRMB which was designed in the Czech Republic, by using activated rubber powder (10 and 15%), were presented. Results showed that although CR addition (5, 10 and 15%) affects the characteristic properties, only 10 and 15% of CR affects the rheological properties before and after aging. The overall effect is mainly hardening of the bitumen, rather than improvement of elastic behavior before aging. Only after aging and with respect to phase angle measurements CRMBs seem to present a more elastic behavior than the virgin bitumen. Activated rubber addition seems to lower the viscosity of the modified bitumen and at some cases (with respect to activation agent content and CR content) improves significantly the storage stability of the CR modified bitumen.

This paper illustrates the results obtained in a study which focused on the mix design and performance-related characterization of rubberized dense-graded mixtures containing a viscosity reduction additive and different percentages of reclaimed asphalt. Following preliminary mix design, plant-produced mixtures were employed for the construction of full-scale trial sections and were subjected to standard quality assurance tests and to advanced mechanical characterization tests. Analysis of results was performed by referring to typical acceptance thresholds and to the outcomes of simplified viscoelastic continuum damage modelling. It was concluded that reclaimed asphalt can have a non-negligible effect on performance properties and that the considered rubberized mixtures, which can be compacted at reduced temperatures, are suitable for paving applications.

This study examines the properties of asphalt concrete modified with crumb rubber using Marshall test. In this study, 5 different mixtures containing 3, 5, 7, 9 and 11% crumb rubber by total mix were considered. The Marshall samples were prepared, tested in the Marshall stability and flow equipment and analysed. The results from the Marshall tests indicate that the stability of the asphalt concrete increases with increasing bitumen content up to 6.2% bitumen content with the mixture containing 7% crumb rubber having the highest stability. The flow initially increased with the addition of crumb rubber up to 7%, but decreased gradually as the percentage of the crumb rubber was further increased to 9 and 11%. Generally, the study indicates that crumb rubber can be used to modify typical asphalt concrete used in Nigeria. This implies that economic gains could be derived by generating wealth from the use of discarded tyre and job creation for those who will be responsible for collecting and processing the discarded tyres and construction of roads that will stand the test of time. Also, successful utilisation will solve the problem of disposing the tyres.

Bitumen of penetration grade 50/70 is the most commonly used binder in asphalt pavements of Europe. This research attempts to differentiate between three bitumen of penetration grade 50/70 that have been acquired from three sources. The rheological properties, fatigue and rutting resistance were analyzed and compared using the results of Dynamic Shear Rheometer (DSR) tests. The rheological test data acquired were modelled and further approximated using the 2S2P1D model. Additionally, to understand the changes in performance due to ageing, all the DSR tests were repeated for Rolling Thin Film Oven Test (RTFOT) aged and Pressure Aging Vessel (PAV) aged bitumen. Finally, the tests results were summarized in a performance diagram to aid in overall ranking of the bitumen taking into consideration relevant parameters.

One of the major parameters which influence the performance of bituminous mixtures is a packed aggregate skeleton with minimum particle rearrangement during traffic loading. The current practice of aggregate design for bituminous mixtures is mostly based on the Fuller-Thomson model to achieve maximum density. However, this approach does not explicitly take into account the volumetric requirements of the bituminous mixture in terms of rutting and fatigue. This study investigates the mechanical behavior of bituminous mixtures prepared using aggregate gradations, designed based on binary particle packing model of Powers (1964) extended to multicomponent packing by Lees (1970). One control sample and two designed gradations are analysed, in which the first one is a continuous gradation, whereas the second one is a gap gradation. A binder content of 5% is used for the three bituminous mixtures. Samples are subjected to dry rut wheel testing and repeated creep and recovery test with a modified test protocol to quantify their rutting performance. Test results indicate superior rut resistance of the gap-graded aggregate mix. Also, the link between aggregate gradation, compactability, and rut resistance of bituminous mixtures is established for a given binder content.

Half Warm Asphalt Mixtures (HWAM) with bitumen emulsion are a relative new, cost effective and environmental friendly emerging technology. HWAM are produced using a combination of aggregates heated up to approximately 120 °C and a percentage of a bitumen emulsion heated to a temperature around 60 °C in order that the mixing and compaction temperature results between 80 to 90 °C. Hence, this procedure involves great savings of energy and low harmful emissions. Although there are recommendations for the formulation of this type of mixtures and references to their conventional mechanical properties, there is a lack of information regarding their rheological properties. This paper presents preliminary results concerning the design and performance of a Half Warm Asphalt Mixture using bitumen emulsion with the aim to evaluate the linear viscoelastic behaviour of this kind of materials. A HWMA was formulated using a cationic super stabilized bitumen emulsion and the Dynamic Modulus (E*) and the Phase Angle ($$\upphi$$) at different temperatures and loading frequencies were measured to produce experimental data for pavement design procedures based on mechanistic principles. It is considered that those findings could encourage greater confidence in promoting the use of these types of sustainable asphalt mixes.

On mature road networks, there is a constant need for long-term pavement preservation solutions. In the 1980s, SBS polymer brought a breakthrough technology with superior performance for surface layer. In more recent years, highly modified asphaltic binder, HiMA, took a step further for structural layers with fatigue resistance. At the same time, circular economy enhances the valorisation of Reclaimed Asphalt. However, its reuse in top layers is challenging, as RA may deteriorate cracking resistance. This paper presents results of laboratory evaluation of an asphalt mix combining 25% RA and the use of highly modified bitumen with 7.5% specific SBS polymer and compared with a same mix using a normal Polymer modified Bitumen 25/55-55. The evaluation was carried out with compactability, rutting resistance, complex modulus, fatigue and low temperature cracking susceptibility. From the mixes, binders were extracted and recovered for further evaluation similarly to the asphalt mixes. This study demonstrated the benefits of both standard PmB and highly polymer modified bitumen to achieve high performance asphalt mix combined with RA. The HiMA binder was able to restore, to a greater extend, the lost properties against cracking and still maintaining the benefits in terms of rutting resistance. This emphasises the benefit for PmB usage for both structural and surface layers, even when using Reclaimed Asphalt, for sustainable modern asphalt pavements.

Recycling asphalt technology is a technology that reuses of aged asphalt pavement that has been damaged and recycled as a new asphalt mixture material which in using it requires a modifier to restore the performance of aged asphalt. Bio-asphalt which is a fraction of bio-oil derived from biomass containing lignin has the potential as a modifier/rejuvenator for aged asphalt. The objective of this study is to determine the potential of the bio-asphalt as a modifier. Bio-asphalt modified aged asphalt binder is tested and evaluated based on AASHTO requirements. Best bio-asphalt content is suggested for modifying aged asphalt binder. Bio-asphalt modified aged asphalt binder were tested to know the mechanical properties by dynamic shear rheometer (DSR) temperature sweep test and frequency sweep test. In this study, the bio-asphalt used are coconut shell bio-asphalt (BioCS) and BitutechRAP, each of which was mixed with Aged asphalt binder from recycled asphalt pavement (RAP) extraction and controller asphalt binder use pen 60/70 (PG 64). The result showed that bio-asphalt can improve the mechanical performance of aged asphalt binder close to pen 60/70 as a controller.

The weak subgrade soil is one of the major challenges for civil engineering applications such as roads and foundations. This study aims to find out the influence of fly ash-based geopolymer on the strength of weak soil to fulfill the requirements of the subgrade layer in the pavement structure. Fly ash particles of class F was used as a raw material for geopolymer synthesis. The alkaline liquid consists of the Sodium hydroxide (NaOH) at 8 molars solution and Sodium silicate Na2Sio3 in liquid form and the ratio of NaOH:Na2Sio3 remained constant at 60:40 by weight. Low plasticity sandy silt was utilized in the study and stabilized using various proportions of fly ash (5, 10, 15, 20, 25, and 30%). Laboratory investigation involves the compaction properties of soil-fly ash mixtures in addition to the mechanical properties including the Unconfined Compressive Strength (UCS) test and the Indirect Tensile Strength (ITS) test. The UCS test results revealed that the compressive strength of the soil greatly improved after adding the fly ash-based geopolymer and 20% of fly ash content achieved the highest UCS at 28 days of curing time. The ITS test results exhibited a progressive increase in the tensile strength of the soil with fly ash geopolymer, which corresponds to a great resistance for cracking in the soil. Geopolymer gel was observed in the stabilized soil, as confirmed by the SEM analysis.

Natural asphalts are often used as stiffeners to obtain hard bitumens. With the decrease of the global production of hard bitumens, the use of natural asphalts as stiffeners becomes increasingly interesting. The main concern when natural asphalts are used as modifiers, is the behavior at low temperature (LT). Studies have shown a brittle behavior in the LT domain, especially when high-content-asphaltene natural asphalts, like the Gilsonite, are used. In the context of a wider study, carried out in IFSTTAR, we have tested the low-temperature behavior of asphaltite modified bitumens (AMB) and that of corresponding asphalt concretes. The Selenizza® asphaltite is used at 5, 10 and 15% to modify a pure petroleum bitumen of 50/70 penetration grade. Asphalt concretes of type EME were then produced. 3P bending tests on notched bitumen bars were performed in order to assess the cracking temperature of binders. On the asphalt concrete scale, thermal stress restrain tests and traction resistance tests at low temperatures were carried out in order to assess the low temperature behavior. Equivalent materials (pure refinery binders and EME produced with hard petroleum binder) were also tested in order to have references. Compared to these equivalent materials, the asphaltite stiffened materials (AMB and corresponding asphalt concretes) present comparable, and in some cases, better LT behavior.

Cold recycled materials are mixes with high percentages of reclaimed asphalt (RA), while the binding phase is commonly composed of Portland cement and bitumen (emulsion or foam). The reproduction of such materials in the laboratory is an important issue for an accurate mix design, even more when applying a volumetric approach. Particularly, the lack of a specific control on the reliability of the foaming bitumen machine seems to hinder the potentiality of these mixtures. Hence, the goal of this study is to assess the composition variability of several batches produced in the laboratory starting from a specific cement-bitumen treated materials (CBTM) recipe and production procedure. An ignition oven was used to measure RA binder and the effective foamed bitumen amounts in produced specimens and a comparison between maximum dry density and theoretical maximum dry density was carried out. The results have shown that the volumetric approach is a suitable tool to obtain the desired volumetric properties in CBTM produced with foamed bitumen. A certain variability between the theoretical maximum dry density and the measured value can be caused by the variability of bitumen content in the mixture.

Digital image processing of the X-ray computed tomography images involves the crucial step of image segmentation which affects the subsequent pore structure quantitative analysis. The main objective of this study is to investigate the effect of ten different global thresholding algorithms based on the grey scale histogram, clustering, entropy and laboratory volumetric characteristics on the internal pore structure properties of the pervious concrete. The key microstructural parameters of the pervious concrete air voids such as porosity, tortuosity, throat number, pore coordination number and distributions of pore volume, throat area, pore sphericity, shape factor and throat eccentricity were analyzed for different thresholding algorithms. It was found from the analysis that the nine histogram, clustering and entropy based algorithms are found to be either under or over estimating the air void voxels compared to the volumetric segmentation method. And as the threshold value increases, effective porosity and number of throats increases and isolated porosity and tortuosity decreases due to the increase of air void voxels and pore connectivity. Overall, it is expected that the present study will help in understanding the importance of threshold segmentation in the field of pavement image processing.

The growing need for high quality paving materials has aroused an increasing interest in innovative reinforcing agents, such as those characterized by nanometric dimensions. The experimental study presented in this paper focused on the use in asphalt mixtures of nanoclays and multiwall carbon nanotubes as bitumen modifiers. The performance characteristics of asphalt mixtures containing these nano-sized additives and those of a reference neat mixture were compared in a wide array of temperature and loading conditions. The testing program included the assessment of linear viscoelastic characteristics, anti-rutting potential and crack propagation resistance, by means of stiffness modulus, flow number and semi-circular bending tests, respectively. Results highlighted that both types of nano-additives have the potential to improve the performance properties of neat asphalt mixtures, with nanoclays yielding a superior reinforcing action.

Physical and rheological properties of asphalt binder modified with Styrene-Isoprene-Styrene (SIS) were investigated through the rotational viscometer (RV), the dynamic shear rheometer (DSR), and the bending beam rheometer (BBR). In order to have a depth understanding on the SIS binder at micro level, morphological observations were conducted using optical microscopy. The result of this study showed that (1) the addition of SIS modifiers increases the viscosity and has positive effect on rutting resistance of the binder; (2) the higher the SIS content, the better the cracking resistance of the binder.

Asphalt binder is the driving economical factor in asphalt pavement design. As a result, it is a good target to optimize the design by minimizing the overall cost while maximizing the performance. Modifying asphalt binders with polymers has been historically a successful method of optimization of pavement design. However, fluctuations in polymer prices and concerns related to sustainability lead many engineers to consider scrap tire rubber as a full or partial replacement of the polymers. Polymer coated rubber (PCR), a hybrid blend of crumb rubber and polymer, is a relatively new alternative material to improve asphalt mixture performance. The objective of the study reported in this paper is to investigate the relative performances of the neat asphalt binder, polymer modified (PM) binder and PCR modified binder using the wet process (PCR-Wet). The influence of the modifications on the viscosity, stiffness and rutting performance were explored. The experimental program included rotational viscosity measurements, linear viscoelastic characterization using frequency sweep (|G*|) test and rutting resistance using multiple stress recovery (MSCR) test on the base binder and the PCR modified binder. Findings from this study suggest that the more sustainable and rut-resistant asphalt binders can be achieved by using the PCR-Wet process.

The performance of the Cold Bitumen Emulsion (CBE) mixture is strongly controlled by the bituminous binder (bitumen emulsion) and the hydraulic binder (active filler). CBE mixture behavior, based on the mastic (both earlier mentioned binders) properties, may vary from a stiff behavior (hydraulic binder) to an asphalt like behavior with viscoelastic deformation failure (bitumen emulsion). This research aims to assess the impact of different fillers on the viscoelastic characteristics of CBE materials and also to evaluate the suitability of the sigmoid model to describe the rheological properties of CBE mastic. To address this aim, bitumen emulsion was mixed separately with eight fillers/blended fillers. The rheological properties of the prepared mastics were evaluated by conducting oscillating temperature-frequency sweep tests, utilizing the Dynamic Shear Rheometer (DSR). The raw data were shifted to the reference temperature and modelled using the sigmoid model to get a smooth master curve. Results showed that most of the active fillers exhibited stiff behaviour. Among the eight fillers, two of them own balanced rheological characteristics while only two fillers reduced the neat CBE binder complex modules. It was found that the sigmoid model was able to satisfactorily describe the rheological properties of CBE binder and mastic over a range of temperatures and frequencies.

Geotextiles are permeable fabrics that can separate, filter, strengthen and drain when used in association with the soil. Natural geotextiles are more advantageous than artificial geotextiles because of its cost and environmental concern. Coir geotextiles have a life of 3 to 5 years depending on the type of coir geotextile. Many roads have been built and are being built in India using coir geotextiles as reinforcement. The main aim of this study is to study the strengthening aspects of woven coir geotextiles in weak subgrades. For this study, Sobanapuram to the Uppiliyapuram road in the district of Tiruchirappalli was selected. Two different varieties of coir geotextiles H2M5 and H2M6 were used in the study. PLAXIS 3D finite element analysis software was used for analyzing the sections with and without coir geotextile with varying GSB layer thickness under static loading. It was found that the section with H2M5 has lower displacement and strain on the subgrade than the other sections.

In this study, usual asphalt mixtures are tested using known and established performance testing methods. In a second step, the asphalt mastics (mastic considered as composite of asphalt binder and aggregate filler) that correspond to the asphalt mixtures are investigated with regard to their rheological properties. All asphalt mixtures and corresponding asphalt mastics are subjected to (i) creep tests in the high temperature range, (ii) fatigue tests in the intermediate temperature range, and (iii) relaxation tests in the low temperature range. Hence, test results are obtained on both scales, the asphalt mixture scale and the corresponding asphalt mastic scale. At the mastic scale, a new set of rheological tests is composed. This set covers the full temperature range, but all results are obtained from the same Dynamic Shear Rheometer (DSR). In the last step, data from both scales are correlated, and finally, sound regressions are identified between asphalt mixture performance parameters and asphalt mastic rheological parameters. It is concluded, that the identified set of rheological tests at the asphalt mastic scale provides a rapid and significant estimate of asphalt mixture performance.

The conventional method for rehabilitation of cracked asphalt pavements is the installation of new asphalt layers. This resurfacing is often not an effective solution, as the existing cracks in the old asphalt layers can propagate rapidly to the top of the new overlay. In order to delay the development of reflective cracking, asphalt reinforcement grids have been used all over the world for many years, showing outstanding results. The grid changes the response of the pavement to loading, increasing the resistance of the asphalt overlay to high tensile stresses and distributing them over a larger area. Thereby the peak shear stresses are reduced at the edges of the existing cracks and thus the crack propagation can be retarded. Nevertheless, the performance of reinforced pavements depends strongly on the adhesion between the interlayer and the asphalt courses. The purpose of this paper is to report shear bonding performance verified in laboratory and in the practice by using a high modulus polyester grid as asphalt reinforcement. Shear bonding tests according to Leutner method have been carried out for different core samples, produced in laboratory as well extracted from test sections or from pavements in operation. The results show that a high bond strength between the asphalt layers can be reached when using an asphalt reinforcement grid, inclusive considering the long-term performance. In this way, the condition of repaired roads can be maintained at high levels over extended periods of time.

This paper studies the fatigue damage of asphalt concrete (AC) under strain controlled load. The 3-phase fatigue life is reproduced by the proposed simulations combining a 2-phase fatigue damage law and the discrete element method (DEM) characterized by discrete force and displacement on each contact. The simulation results present good agreements with experiments after the parameter calibrations. The reinforcement effect of fiberglass grids on the fatigue life of asphalt concrete is studied with 4-point bending (4 PB) fatigue test. These preliminary results comparing simulations and experiments show the consistency of the proposed 2D model on describing part of the interactions between grids and asphalt concrete.

Sustainable road management asks for reliable and economic investigation methods to assess the surface and the structural substance of roads. A connection exists between properties of mixture, binder, carrots, surface texture and acoustic parameters. Noise emission and surface texture are particularly sensitive to minor variations in road engineering properties. Among the later grain size distribution is the most important quantity. Time series of drill cores, in situ surface and acoustical measurements draw a consistent picture of the process of top asphalt layer aging, including grain movements and void clogging. Georadar allows for fast microwave acquisition and mapping of electromagnetic properties as function of wave travel time. Ultrasonic measurements take more time but provide elastic parameters of road material which relate to structural substance. Measurements of mechanical road properties are sensitive to the temperature distribution inside the road body yielding temperature-dependent layer models. Depth profiles should be corrected to standard temperatures. Linear velocity-temperature relationships for ultrasonic waves yield gradients around 11 m/s/°C in a four-year old semi-dense asphalt top layer and for a temperature range between −17 and 65 ℃. Heated asphalt displays strong wave absorption particularly at high frequencies which limits penetration depths and resolution.

The Wheel Tracking Device (WTD) has been widely used for laboratory characterisation of permanent deformation or rutting in Hot Mix Asphalt (HMA), however, the conventional setup of the device has limitations in terms of capturing the tertiary zone of the permanent deformation curve, and subsequently, the Flow Number (FN). This makes the Hot Mix Asphalt (HMA) characteristics related to the permanent deformation resistance difficult to analyse. Hence, a newly modified setup of WTD has been proposed for better characterisation of HMA mixes. The study focuses on the investigation of the repeatability of the new test-setup to eliminate any arbitrary calculations. The study utilised three different kinds of mixes with Nominal Maximum Aggregate Size (NMAS), and Void in Total Mix (VTM) as the factors, each with three replicates. For the experimental part and analysis, both confined and unconfined setup of the device will be used for each kind of mix. For the unconfined setup, the Flow Number (FN) was used as the parameter for the analysis. For the confined setup, the rut depths at 12000, 25000, and 50000 wheel passes or the final rut depth were utilised. This study is expected to give an insight to the modified Wheel Tracking Device and its repeatability for the purpose of robust characterisation of asphalt concrete mixes, which will in turn be helpful in developing precision estimates required for making it a standard practice in the near future.

The Heavy Weight Deflectometer (HWD) is a nondestructive testing device widely used for airfield pavement assessment. The HWD test consists in applying a wheel-representative load, generated by a falling mass, at the pavement surface. Deflections time histories are recorded by geophones located at several distances from the applied load. Inverse analysis procedures are needed to estimate layers mechanical properties, such as Young’s moduli for Linear Elastic (LE) materials or complex moduli for Linear Viscoelastic (LVE) materials. Most of inverse analysis processes consider (i) LE behaviour for pavement layers and (ii) static HWD loading. However, it has been shown that these hypotheses are leading to misestimate bituminous layers modulus and, in most cases, to poorly optimized maintenance. In order to better take into account bituminous layers behaviour, it is required to use LVE constitutive model and adapted numerical methods. This study presents a comparison between measured deflections and deflections computed using the Spectral Element Method (SEM) which was implemented during this work. The tested pavement was built within the test facility of the French Civil Aviation Technical Center (STAC). It is equipped with temperature probes at several depths within bituminous layers. The Spectral Element Method is a semi-analytical method in frequency domain. The pavement response is computed for unit load and for each frequency (from 1–200 Hz, every 1 Hz) at each geophone location, which leads to the Frequency Response Function (FRF). Then, frequency-domain deflections are obtained by weighting the FRF when calculating the Fast Fourier Transform (FFT) of the measured HWD load. This method is numerically efficient and shows good potential to solve axisymmetric multilayered problems. In particular, it allows to take into account frequency-dependent complex modulus analytical expressions. Spectral Element Method results have been validated with time-domain Finite Element Method data computed on a common pavement structure. SEM which is much faster than FEM shows great potential for further backcalculations application.

Crack patterns in continuously reinforced concrete pavements (CRCPs) traditionally have been controlled by continuous longitudinal reinforcement steel. This passive crack control has resulted in the formation of an unfavorable crack pattern with a high probability of clusters of closely spaced cracks, which has eventually led to premature distresses such as spalling and punch-out in the later age of CRCP. In an effort to eliminate the cluster cracking and crack meandering, the standard design concept for CRCP in Belgium underwent several changes over time, mainly addressing the longitudinal reinforcement rate, depth of the reinforcement steel, and thickness of the concrete slab. In the current design concept, the active crack control method in the form of partial surface saw-cuts on side of the concrete slab perpendicular to the axis of the road within 16–24 h after the placement of concrete is being employed to facilitate the formation of a regular spaced crack pattern in CRCP. However, this area needs further investigation and validation. The present study investigates the early-age crack pattern induced by active crack control method under typical Belgian conditions. Therefore, a 3D finite element model of CRCP with induced partial surface saw-cuts is developed using FE tool Diana 10.2. Findings show that active crack control method exhibits the cracking sooner than passive crack control method. Moreover, a more controlled and regular spaced crack pattern is produced.

An array of four synchronized single-axis accelerometers was fixed to the surface of an asphalt pavement. Vertical acceleration traces triggered by several nearby passes of a truck with known characteristics were recorded. The work focused on presenting and demonstrating an interpretation method for inferring the mechanical properties of the pavement system based on the recorded accelerations. In general terms, the method was based on careful low-pass filtering the field-measured acceleration traces, and then best-matching them with a corresponding set of calculated acceleration traces. For this purpose, the pavement system was modeled as a two-layered linear elastic half-space, and a model-guided signal filtering approach was devised to ensure that irrelevant signal content is removed prior to the matching. Based on the analysis of six separate truck passes it was noticed that the inferred upper layer modulus exhibited medium variability (coefficient of variation of 45%) while the lower (subgrade) modulus showed little variability (coefficient of variation of 8%). The moduli values displayed fair agreement with those independently estimated from non-destructive and semi-destructive tests. By analyzing many more passes inferred moduli are expected to become more representative. Overall, the method seems workable and scalable, with capacity to handle any number of acceleration sensors as well as other sensor types.

The application of an asphalt mix overlay over old rigid pavement is a way to extend the service life of a pavement construction up to 10 years. The effectiveness of this maintenance measure strongly depends on the bonding conditions between the asphalt and the concrete layer and the effective transfer of the stresses and strains from the upper to the lower layer under traffic loads. The bond characteristics were investigated using laboratory tests and numerical simulations. Static testing equipment was used for the determination of the shear and tensile adhesion strength of cores from six sections of one highway. All six sections include three different pre-treatment methods and two types of asphalt mixtures. To evaluate resulting stresses and strains in the pavement construction under traffic load, finite elements simulations were carried out. Thereby, a simulation of the laboratory shear test setup provides information about the bond conditions as defined in the finite element model, which is used as input to simulate stresses and strains under different loading conditions. This approach is not only used to identify significant resulting stresses and strains due to traffic load but also to derive threshold values for future laboratory shear adhesion tests.

As state Departments of Transportation (DOT) continue to adopt the Mechanistic-Empirical Pavement Design Guide (MEPDG), the ability to readily obtain higher quality input parameters becomes an ever-growing need. One such parameter is the Resilient Modulus (MR), which is defined as the ratio of cyclic deviatoric stress to recoverable strain. The ensuing investigation was conducted in an attempt to replace the use of the repeated load triaxial test in determining the MR of soils with modulus estimations obtained from Light Weight Deflectometer (LWD) and Ground Penetrating Radar (GPR) testing. The constructed test setup consisted of a test pit subdivided into six sections containing an elastic silt (MH) at different water content and density levels. LWD and GPR testing was conducted at each of the six test sections, and the results were correlated to the different soil water content and density levels. Through a regression analysis, the preliminary model was developed the ELWD of fine-grained soils was estimated using the soil’s water content, bulk density, and the measured dielectric constant. A strong correlation was observed (R2 of 0.858) between the predicted and measured ELWD values, indicating its potential for future use in predicting stiffness of fine-grained soils using GPR.

Several isolated premature failures on the rehabilitated portion of the Lahore-Islamabad M-2 Motorway were observed, within a year of opening to traffic. Based on the visual evaluation of the distresses, failure causes could be attributed to poor in-pavement and surface drainage on the rehabilitated sections, segregation of HMA mixture, HMA mix-design, and the presence of heavy axle loads in the outer lanes. Cores in the distressed and normal areas were taken in different sections along the south and north bounds direction and several destructive tests were conducted on the HMA materials to determine the field compacted air voids. Also, field permeability in-situ tests were conducted on the same locations where cores were taken. Results showed that the mix segregation occurred in the fast lanes resulted in higher field air voids than the plant mixed-lab compacted samples. Thus, the permeability of mixes in these locations was significantly higher than expected, which caused water to seep through the surface mixes in all lanes. Additionally, due to the cross-fall of the HMA and aggregate base layers, the moisture entering in the fast and middle lanes accumulated under the outer lanes in both directions.

Permanent deformation of asphalt mixes is caused as a result of several parameters, including; asphalt mix characteristics, climatic conditions, and traffic loading extent and configuration. For evaluating this distress mode, international institutions and standard codes of practices suggest different processes and testing methods. However, each of these investigates rutting resistance of asphalt mixes at specific conditions. The aim of this research was to investigate the effects of different loading configurations on Hot Mix Asphalt (HMA) in laboratory, applying Repeated Load Permanent Deformation (RLPD) testing method. With this purpose, various loading configuration and load durations and rest periods were applied. In order to simulate the impacts of both light and heavy weight traffic loading on permanent deformation resistance of mixes, two different stress levels of low and high extents were applied in RLPD testing. Based on the findings of this research, it resulted that asphalt mixes under low stress level (which corresponds with light weight loading traffic) in RLPD testing, do not get to “Flow Number” values. In addition, it resulted that performance characteristics of asphalt mixes cannot properly be evaluated applying one loading condition only. Among the various testing parameters, it resulted that “Flow Number” is the best indicator of resistance of asphalt mixes against permanent deformation.

The pavement performance prediction models are key components of pavement management systems. Predictions models are used for determining the future condition of pavement as well as types of maintenance and rehabilitation actions needed to keep the operation of transportation systems continuous. Accordingly, maintenance and rehabilitation actions must be prioritized due to limited budget allocations. Mississippi Department of Transportation (MDOT) utilizes Hidden Markov probability models. However, varying traffic conditions and unusual events in the operation are not reflected in these models due to the nature of probabilistic modeling. A new model using a more inclusive and powerful approach to predict the future condition of the pavement is needed. In this study, the distress data from Continuously Reinforced Concrete Pavement (CRCP) sections in Mississippi was used to develop a performance prediction model using Artificial Neural Networks (ANNs) approach. Additionally, rehabilitation actions were included as part of the model inputs to study the impact of rehabilitation actions on the model. The performance of all the developed models showed a good agreement between observed and predicted condition measures. However, only one model with the best statistical accuracy was selected to be utilized as the best performing model, which can be used for the prediction of CRCP performance within the allowable time range.

Pavements generally demand necessary maintenance and rehabilitation to maintain their service performance in the whole lifespan. The maintenance and rehabilitation strategies are usually formulated based on the results of non-destructive testing, in which the traffic speed deflectometer (TSD) test is an efficient tool for pavement structural evaluation at network level. In this paper, the TSD test on asphalt pavements is simulated by a spectral element method-based theoretical model, which is further combined with a nonlinear minimisation algorithm to achieve parameter identification. After conducting parameter sensitivity analysis, a case study is used to demonstrate the ability of the proposed parameter identification technique. The results show that this technique is able to deal with TSD measurements to effectively identify the structural parameters of asphalt pavements. The presented TSD test-based parameter identification technique is a promising tool for asphalt pavement structural evaluation at network level, which is beneficial to formulate cost-effective maintenance and rehabilitation strategies.

This paper presents the results of field studies of hot mix asphalt pavements compaction using conventional compaction technologies (train of vibratory steel drum, pneumatic tired roller) and the Asphalt Multi-Integrated Roller (AMIR) to examine the effects of different compaction methods on the water permeability of asphalt concrete pavements as a surrogate measure of durability and eventual long-term performance. Nine different pavement construction projects were used in this paper where laboratory and field properties of pavements compacted using conventional and AMIR compaction were measured and evaluated. Field measurements of water permeability showed higher mean value and higher variation of the permeability coefficient for conventional compaction than the AMIR-compacted pavements, even though the air voids and relative compaction were almost the same. Compared to the conventional compaction, statistical analysis showed that AMIR compaction reduced water permeability of compacted surfaces on stiff bases (such as an overlay on top of a milled asphalt concrete pavement) and also reduced the rate of permeability increase due to increase in air voids.

In repairing asphalt pavements of busy airports or highways carrying heavy traffic, a common constraint encountered is tight time windows available for the repair work. A consideration is to provide sufficient cooling time before opening to traffic. Opening too soon to traffic with insufficient cooling time may lead to early damage to the repaired pavement. This is due to the relatively high temperatures in the asphalt layer as well as the interfacial bonding layer, resulting in insufficient strength in both layers not strong enough to resist heavy wheel loads. This paper applies a validated finite-element simulation model to analyze the time history of temperature cooling in a newly compacted asphalt pavement layer. The simulation model makes use of the thermodynamics and heat transfer theory to predict the temperature changes with time after a newly paved pavement section has been compacted. This information will enable the maintenance team to determine the appropriate time that the repaired pavement section can be opened to traffic. This paper analyzes two common thicknesses of pavement repairs, predicts time variations of temperature within the newly paved asphalt pavement materials for different weather conditions. A summary of the cooling time needed for each case of pavement repair under different weather conditions is presented. The results highlights that the commonly adopted practice of relying on the top surface temperature to open a newly repaired pavement section to traffic is inappropriate and may lead to early damages to the repaired section.

To guarantee the smooth transportation of goods and passengers over a highly loaded road network, more efficient and even innovative maintenance and rehabilitation measures are needed. During the last decade, the Federal Highway Research Institute (BASt) has accompanied in a rehabilitation project on a federal roadway with different cold recycling construction types and has regularly monitored it with non-destructive test methods. In recent years, different aspects of the technology have also been investigated on laboratory scale through different research programs. In view of the current positive international experience with bitumen-stabilized materials (BSM), foamed bitumen mixtures in particular have been met with great interest in Germany. In the first phase of a new research project in cooperation of BASt and Wirtgen GmbH, a 100 m long test section will be tested in the demonstration, investigation and reference areal of BASt (duraBASt) in order to extract further experience with the method and adopt it for Germany. After completion of the construction process, one cold-recycling and one reference pavement type will be analyzed with the standardized BASt Accelerated Pavement Testing Program and further laboratory tests. The collected findings of the test section in the network as well as on duraBASt will be utilized in design procedures and further development of national regulations and specifications in Germany.

Distributed fiber optic strain sensors represent a powerful tool for gathering continuous strain data along an optical fiber within engineering structures under loads. On the other hand, pavements represent a harsh environment for optical fibers, in particular during construction process. Hence, optical fibers which are adequately protected by a robust cable sheath were used in this project for the purpose of measuring strains within a pavement. Strains were measured along the sensor cables with high spatial resolution while an aircraft was placed on the instrumented area, subjecting the pavement to static loads. The procedure was carried out in warm and cold conditions in order to study the effect of temperature conditions on the strains measured in the pavement. The measurements gave a detailed insight into the strain distribution in the loaded pavement section. The fiber optic sensors proved to be robust enough to be applied on a real construction project. Furthermore they may provide, in general, useful strain data e.g. for testing new pavement materials, assessing new design methods or investigating structural health of existing structures.

Stresses and strains within a road structure are affected not only by the amount and distribution of tire contact pressures as well as speed and rest periods between load passings but also by the lateral position of the wheels within the traffic lane. In this work, the effect of channelized and lateral wandering of 65 kN half axle loads on the performance of a newly constructed asphalt pavement section for low traffic volume has been studied by means of a Mobile Load Simulator MLS10 accelerated pavement loading facility. 250,000 super single wheel passings at 18 km/h were applied in each case and evaluated with visual inspections plus rutting and Falling Weight Deflectometer (FWD) measurements. Pavement response was monitored with strain gauges, accelerometers and thermocouples. The combined analysis of the results showed that channelized loading created longitudinal surface cracks in the pavement, whereas non-channelized loading did not produce any visible sign of cracking or other damage. Rutting in both loading locations showed similar depths, although the non-channelized rutting basin was wider and smoother than in the channelized case. Accelerometer and strain gauge results demonstrated the importance of the load position on the pavement’s response.

The determination of frost penetration is one of the main requirements in considering environmental effects in pavement design in cold regions. At the present time, the frost depth of pavements in Sweden is estimated computationally using computer software which approximates the heat equation by finite difference. Due to the geographical positioning of Sweden, a wide range of air freezing index and frost penetration depths were observed with lower values in the south and higher values in the north. This paper introduces a simplified design chart which is obtained by empirically correlating the air freezing index estimated from temperature measurements by 44 local meteorological stations to the maximum frost penetration depth obtained by 49 RWIS Road Weather Information Station data. The results are classified depending on their location and the climatic zones defined by the Swedish pavement design codes. Nonlinear prediction intervals are implemented to provide a range of possible frost penetration depths since local site conditions are not taken into account. Further research is required to consider local on-site effects such as frost susceptibility of pavement materials, the thermal conductivity of layers, access to water and snow covering.

The falling weight deflectometer (FWD) has been the principal equipment used for accurate assessment of pavement structural condition for well over 30 years and back-calculation techniques are well established. In recent years however different types of rolling wheel deflectometer have been developed and they have the potential to allow the collection of structural information on a routine basis. The challenge is to interpret the data from these devices in the most meaningful way, since it is necessary that the deflections take place in different locations compared to the FWD. This paper describes an analytical approach that allows prediction of deflections in a jointed rigid pavement on a line offset from the wheel path. It outlines the assumptions that have to be made and the refinements that are potentially possible. Comparisons with both real measurements and finite element analysis are presented and it is found that the proposed approach is adequate in terms of accuracy and sufficiently rapid for practical back-calculation. The issues of vibration and noise in the deflection measurements are discussed and possible ways of handling these are put forward. Additionally, the sensitivity to model parameters of the rolling wheel deflectometer passing a joint are assessed, which can lead to strategies on back-calculation of load transfer. The conclusion reached is that the technique outlined in this paper opens the door to effective use of rolling wheel deflectometer (RWD) equipment for evaluation of load transfer efficiency in joints.

Accelerated pavement testing (APT) is an effective method in evaluating pavement performance by applying wheel loading and speed under controlled conditions. This study aims to investigate the effects of wheel loading, speed and ambient temperature on the pavement responses at different directions and depths of pavement structure. A two-layer asphalt pavement structure was constructed on a base layer constructed 10 years ago. Strain gauges were installed both in the transversal and longitudinal directions of motion on the bottom of both layers. The response of the asphalt layers was monitored and the developed strains were recorded. The results show that maximum compressive strain increases with wheel load. In contrast, the maximum tensile strain decreases as load increases; this is probably due to the high confining pressure that occurs within the pavement structure when higher wheel load is applied. The maximum compressive and tensile strains decrease with wheel speed, because the asphalt mixture becomes stiffer at high wheel speed (frequency). The maximum compressive and tensile strains in the transversal direction increase with ambient temperature, because of the low stiffness of asphalt materials at high temperature, which appears to be the cause of rutting.

Asphalt Concrete (AC) overlay is one of the typical pavement maintenance strategies on Portland cement concrete (PCC) pavements that enhances its service life. However, reflection cracking is one of the common distresses due to the cyclic expansion and contraction of the joints or cracks in the PCC layer that attributed to the variations in environmental conditions. The current overlay tester (OT) protocol in Texas suggested a single maximum opening displacement (MOD) in PCC pavement types. However, the displacement magnitude varies accordingly. As such, this study focuses on the field quantification of Jointed Concrete Pavement (JCP) and Continuously Reinforced Concrete Pavement’s (CRCP) discontinuity movements with respect to the application of asphalt overlay and seasonal changes. Crackmeters were installed at the JCP and CRCP sections and measurements were recorded during winter and summer. Preliminary results have shown that the PCC pavement joint/crack movements significantly reduced after overlay placement. Furthermore, variations of the movement relative to PCC pavement types and seasonal variations are distinct and significant. Hence, the magnitudes of MOD according to pavement types are suggested to be modified when performing reflection cracking resistance evaluation using the asphalt overlay tester.

Electric mobility scooters (EMSs) which are solely battery-operated personal small vehicles are becoming an increasingly common way for a walking aid. To ensure the accessibility of EMS users, pavement surface condition of sidewalks is one of the important factors in terms of traveling safety and comfort. This study examines the requirements of evaluating sidewalk pavements by focusing on the interaction between surface properties and vibration responses of an EMS. As a result, the EMS consists of two distinctive resonance frequencies of 8 and 30 Hz associated with the megatexture and microtexture in the surface properties, respectively, at a constant speed of 3 km/h. This finding proves that the EMS vibration highly correlates with the Mean Profile Depth (MPD) inducing axle excitations but not the International Roughness Index (IRI). According to the pavement-vehicle interaction analysis, this study finally suggests that measuring acceleration of an EMS is capable of estimating MPD which is a good estimator of surface friction.

A so-called semi-dense asphalt (SDA) is widely used in Switzerland as a low noise pavement. During 2018, our preliminary grinding tests on small SDA sections and subsequent broader tests have shown that grinding is an effective way to regain −3 to −5 dBA, measured with the close-proximity (CPX) method. The main purpose of this paper is to put forward a large-scale maintenance process which is effective in regenerating the acoustic performance of aged SDA wearing courses for entire road sections. A secondary purpose is to observe the effect of the same grinding method on dense pavements like AC, ACMR and MA. Several roads at different locations and environmental conditions have been tested in early 2019. At each location the treatment was evaluated by the measurements of grinding depth, mean texture depth and CPX rolling noise. Acoustic effectiveness of the grinding method depending on the pavement characteristics are examined. Our first results indicate that all the treated surfaces become less noisy, regardless of grain size or pore volume. The incidence of grinding on reshaping the surface texture in a way that facilitates air pumping and diminishes tyre vibration will be discussed.

Potholes in flexible asphalt pavement systems are one of the major distresses for fatal accidents. Ingress of water through the pothole disturbs the integrity of the pavement system. Delayed maintenance of potholes will adversely affect safety of road users and health of the road pavements. Therefore, detection, quantification, and maintenance of potholes are three indispensable tasks in pavement asset management. Manual collection of pothole data is time-consuming and laborious. Hence, the use of cutting-edge artificial intelligence techniques has become popular in the recent times. The major objective of this study was to develop a framework for pothole detection, quantification, and maintenance system (PDQMS) to detect and quantify potholes using pavement images collected by an automated survey vehicle; the system was also incorporated with a mechanism that calculates the amount of patching material required for maintenance. The state-of-the-art multiple-object detection algorithm, You Only Look Once version 3 (YOLOv3) was selected to detect potholes from the images. One of the salient characteristic features of the PDQMS developed in this study was to use severity-based pothole classification approach, a first-of-its-kind novel framework, which helped group the pavement sections based on severity of potholes for maintenance operations. The proposed framework is envisioned to assist the agencies in making decisions to patch potholes and reduce fatal accidents, if not maintained.

Pavement friction significantly affects the road safety. Over years, researchers have developed multiple models in an attempt to estimate pavement friction performance. The present study aims at developing a stochastic model for the prediction of short-term friction loss based on field-friction data, which adapts the survival probability analysis in terms of a Kaplan - Meier survival curve. The traffic volume expressed through the Annual Average Daily Traffic (AADT) is the main variable of the developed model, assumed to affect more the friction loss within the short-term period of the investigation. The friction level of the preceding year is the second variable of the model that is assumed to embody other factors affecting short-term friction deterioration in the field. Following the assumptions made, the impact of other factors are deemed to be incorporated in the variable of the friction level of the preceding year. However, this assumption is discussed in the constraints of the proposed methodology. All in all, the results of the study are encouraging and can be a useful tool for timely scheduling future maintenance actions in the framework of proactive asset management.

Tire—road surface contact is a complex combination of stresses and deformations that depend on tire and road factors, such as vehicle speed, weight, tire material and type, tire pressure inflation, camber and texture of the surface layer. In this paper, the problem of the tire-pavement contact is studied using a realistic description in normal section and corner. Mechanical field is validated with a press system under different inflation pressures and loads. The model requires precise tire geometry and an equivalent Young’s modulus. For this purpose, an optical method based on a photogrammetry method provided a 3D field of displacement. The estimation of the equivalent Young’s modulus is also proposed as a function of the inflation pressure resulting from the press load tests. Finally, a comparison is made between the measured footprint of the tire, the result of the semi-analytical calculation as well as the effect of tire inclination (corner/turn) on the distribution of surface stresses that is demonstrated.

The assessment of the structural and functional pavement condition is nowadays a fully machine based non-destructive procedure in which equipment covers all the data input required for a modern PMS approach. A LCMS (Laser Crack Measurement System) is a high-resolution transverse profiling system based on 3D Sensors capable of real time continuous measurement of condition data in a single run. One of the images produced by a LCMS is the intensity image, which expresses the reflective properties of the pavement surface. As quality control of road marking often retro-reflectometers are used. A limitation of retro-reflectometers is that they can only measure for instance a single edge marking at any time whereas the road surface can have multiple markings. The LCMS captures the reflective properties of the surface over the total width of a lane and as such can measure the reflective properties of all road markings at any transverse location. This paper discusses the results of the correlation of the retroreflectometer measurements with the reflective properties measured by the LCMS-2. This first time study resulted in a very promising correlation showing that the LCMS-2 collected data is very useful in rating the quality of road markings and predicting the need for maintenance.

Milling is an indispensable process in recycling of asphalt pavements. The process involves the fracture and removal of asphalt mix under high stress and rapid loading conditions. An understanding of milling induced stress is important for avoiding or reducing the impact on pavements below the milling line and to optimize the milling process. The objectives of this research were to develop a finite element model of the milling process and estimate stress distributions under different milling conditions. Milling of a fine and a coarse graded Hot Mix Asphalt (HMA) and a Stone Matrix Asphalt (SMA) were modeled for different milling speeds and depths. The results indicate significantly high milling induced stresses below the milling line. Gradation of mixes, interface and milling speeds have significant effect on stiffness and hence stress distributions and maximum stresses. The inference is that the depth of milling should be decided on the basis of existing conditions which include layer depths, location of interface, strength of bond between the layers, type of mix, temperature of mix and milling speed (drum rotation speed). To avoid high stress related damage to remaining pavement layers, milling to partial depth of a layer should be avoided. Research is needed to evaluate changes to the structural condition of remaining pavement due to milling.

Road Markings are an important safety feature for directing and guiding traffic without distracting its drivers. The erosion of the marking material as a result of prolonged exposure to rain and traffic actions, greatly reduce their performance. In this paper, results from field and laboratory investigations on innovative preformed thermoplastic road markings sheet with 3D impressions are presented. An immersion wheel tracking test was conducted in the laboratory for evaluating material effectiveness against stripping in long-term exposure to water and traffic loading. The results showed that preformed sheet installed on pre-heated and non-heated asphalt surfaces are capable of withstanding long (20,000 cycles) exposure of continuous traffic while submerged in water. Overall, the thermoplastic sheet installed in both conditions, demonstrated excellent performance against stripping, although the performance was relatively better when installed on the pre-heated surface. Furthermore, one-year field observations showed that preformed marking installed on asphalt and concrete surface retains their macrotexture, maintains excellent dry and wet frictions. The 3D impression was also found beneficial on drivers’ behavior for speed reduction. Depending on the vehicle type, the reduction was 20–31% immediately after installation and 9–17% after one year. Overall, this study suggests that preformed thermoplastic road marking is not only a durable product but also 3D illusion that provides some traffic calming benefits.

Asphalt surface damage due to water pumping from moving traffic is underexplored. A laboratory test has been developed to simulate the impact of moving traffic on submerged surfaces. In total 36 tests were conducted on Hot Rolled Asphalt (HRA), open-graded Stone Mastic Asphalt (SMA) and Porous Asphalt (PA). The specimens were submerged in shallow water while 5 kN repeated loading was applied at 5 and 10 Hz frequencies until failure. It was observed that irrespective of surface type, cracking, and rutting occurs simultaneously, although their magnitudes were different on different types of surfaces. The experimental data were then used to develop multi-input deterioration prediction models using regression analysis. The experimental parameters such as asphalt surface type, aggregate size, weather conditions, void contents, load magnitude and load frequencies were used as model inputs. The measured cracking and rutting were used to compare with the predicted cracking and rutting. The models yield 84 and 71.6% correlation with measured rutting and cracking respectively. Furthermore, combined distress (cracking and rutting) model for all HRA and SMA variations was developed and found 52 and 39% correlation respectively. The low correlation was believed to be due to the measurement difficulty of narrow cracks during testing. Despite this, the models showed promising results for overall distress prediction and with further development, it could be used as a screening tool to evaluate the performance of asphalt surfaces when subject to both prolong rain and traffic loading.