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About this book

This volume on “Advancement in the Design and Performance of Sustainable Asphalt Pavements” includes a collection of research and practical papers from an international research and technology activities on Mixture Design Innovation, Structural Pavement Design, Advancement in Production and Construction, Climate Changes and Effects on Infrastructure, Green Energy, Technology and Integration. The volume constitutes an important contribution in view of the urgent need to develop materials, designs, and practices to ensure the sustainability of transportation infrastructure. This volume is part of the proceedings of the 1st GeoMEast International Congress and Exhibition on Sustainable Civil Infrastructures, Egypt 2017.

Table of Contents

Frontmatter

Development and Finite Element Analysis of Piezoelectric-Based Prototypes for Harvesting Energy from Roadway Pavement

Energy harvesting is a process that captures unused ambient energy such as heat, vibration, stress or movement that would otherwise be lost. Highway pavements infrastructure exposed to energy-potential resources from vehicle vibrations and traffic loading strains that could be harvested. Piezoelectric transducers (PZT) are potential materials for harvesting energy from pavements as they convert mechanical loading strains into electric voltage. For this purpose, this study is aimed to evaluate two types of piezoelectric prototypes integrated within asphalt mix; cylindrical disks and thin film sheet, suitable for compression and bending state of stresses, respectively. Finite element (FE) analysis was conducted to simulate prototype response in different geometry under dynamic loading. The evaluation of the prototype involves laboratory testing of their power output as a function of stress, and FE simulation of their mechanical behavior. Results suggested that power output is highly dependent on loading frequency and magnitude and PZT geometry but could be promising in powering low-watt LED traffic lights and wireless sensors embedded in pavement particularly in remote areas.
Hossein Roshani, Samer Dessouky, Arturo Montoya, A. T. Papagiannakis, Ala Abbas

A Bitumen-Based Prototype to Predict the Workability of Asphalt Concrete Mixtures

Having a reliable and repeatable method for measuring the workability of asphalt mixtures for a wide range of asphalt blends is important. The major objective of this paper is to develop a new bitumen-based prototype for the measurement of the workability of different asphalt blends. Correlation and prediction of the mixing temperature with the aid of the developed prototype have been established as a secondary objective of this study. At first, a principle was presented as a basis to develop the workability prototype. The device developed in this study utilized a commercially available motorized Vane Shear Test (VST) apparatus which is mainly used to measure the shear strength of soil. To resemble the aggregate effect while mixing, a specially designed spindle was developed. The VST has been modified to suit the present purpose of the workability test. An accurate torque meter was installed to measure the torque required to rotate the spindle in the blend at a constant revolution. The device was tested with asphalt blends of different ranges of workability. The workabilities of polymer-modified and water-foamed asphalts were evaluated at temperatures of 100, 140 and 180 °C, respectively. It was found that the bitumen-based prototype was able to differentiate the workability in light of the constituents of the studied blends. In addition, the prototype helped in roughly predicting the mixing temperatures of the studied blends based on the concept of Workability Index (WI).
Aboelkasim Diab, Zhanping You

The Use of Wastewater in Construction of Base Course Layers in Pavement Structures

Large amounts of wastewater are produced annually and treated for use in agriculture, irrigation and groundwater replenishment. The produced treated wastewater (TWW) can be used as an alternative to the millions of gallons of fresh water that are typically used in pavement construction. This study was conducted to investigate the potential of using treated wastewater in base course layer in pavements. Chemical analysis tests were conducted both on the treated wastewater samples and on tap water to determine their properties. Samples of the base course material were prepared and soaked using the two different TWW samples as well as the tap water. Proctor compaction and California Bearing Ratio (CBR) tests were conducted on the prepared samples, and the results have shown that TWW can be a suitable replacement for fresh water in base course layers in pavement construction.
Farid H. Abed, Munir D. Nazzal, Mousa F. Attom, Magdi E. El-Emam, Nouran ElMessalami, Saif Al-Dabagh

Hydraulic Conductivity of Layered Compacted Granular Materials Used as Pavement Foundation

Base and subbase layers form the structural platform of flexible and rigid pavements. Both layers are commonly made of selected granular material and properly compacted to provide an adequate bearing ability. Improper drainage of these two layers creates various structural defects that ultimately caused failure. Thus, it is of prime importance to evaluate the hydraulic conductivity of these two layers to avoid any structural damage of the pavements.
The current paper is an attempt to evaluate the hydraulic conductivity of several gradation of granular materials in sequences layers usually selected and commonly used as base and subbase course material in pavement construction. The selected materials confirm with SORB specifications (State Commission of Roads and Bridges) issued in Iraq in 2003 for granular base and subbase layers. The tests were performed under constant head condition within the range of validity of Darcy’s Law and laminar flow conditions in double layers sequence. Regression analysis of the test results revealed that the hydraulic conductivity is a function of the in place void ratio, mean particle diameter and degree of packing of the granular material. These parameters are presented in the form of equations and can provide approximately quick estimate of hydraulic conductivity of each granular layer.
Namir K. S. Al-Saoudi, Khawla H. H. Shubber

Extending the Service Life of Bridges Through Proper Compaction of Asphalt Decks

Bridges are major components of the highway infrastructure and play important role in the development of societies and their economic growth. The safety and performance of bridges do not depend on design and construction of its structural members alone but also on the degree of protection provided by the asphalt layer added to provide a comfortable ride as well as significant protection against penetration of water and other harming materials to the main structure of the bridge. Compaction of the asphalt deck of the bridge is done only by static rollers while vibratory rollers are not allowed on the deck. However, steel rollers, static or vibratory ones, induce hairline cracks during compaction which allows water, salt and other harmful materials to penetrate through the asphalt deck and reaching the main slab of the bridge which may be made of reinforced concrete or steel members. The presence of water and salt can speed the process of corrosion leading to earlier than expected deterioration of the bridge and in some cases failure of the entire structure. The Ministry of transportation of Ontario (MTO) has used a new asphalt compactor termed Asphalt Multi-Integrated Roller (AMIR) which provided a much tighter asphalt mat with significantly improved permeability performance, higher densities and abilities to compact thicker layers with higher efficiency and less number of passes when compared to current steel rollers. The results led the MTO to include permeability measurements into its Q/A and Q/C requirements for bridge asphalt decks. This paper presents the outline of utilizing AMIR compaction technology on three MTO bridges, the results of field permeability measurements of asphalt sections compacted side by side using AMIR and steel rollers, and laboratory test results. The results showed that the AMIR technology will provide better protection to bridge deck and its steel structure and reinforcement; leading to longer service life with less frequent maintenance. Finally, the paper includes preliminary economic analysis showing the gains and benefits resulting from adopting the new technology to the main parties involved with highway assets.
Amir Abd El Halim, Ahmed El-Desouky, Abd El Halim

Characteristics of Jointed Rigid Airfield Pavement Using Different Material Parameters and Modeling Techniques

Rigid pavements have been used broadly in airfield constructions. As the pavement design is expected to deliver acceptable performance along its service time under wide-ranging circumstances. The concept of the load transfer is crucial in pavement design procedures. Many researchers investigated rigid pavement in airfields based on the finite element method. Despite the notable enhancement, significant concerns were overlooked. These simplifications to the developed models may affect the results of the developed models and make them unrealistic.
Sensitivity studies were carried out to investigate the effect of the material parameters of the pavement layers and explore the effect of modeling techniques on the load transfer indicators. These parameters include the influence of the dynamic damping, the joined influence of aggregate interlock and dowel bars at the joint, separation between concrete and base, the bondage of the interface between the dowels and the surrounding pavement and simulation of the gap between the adjacent slabs at the joint.
The development of the three-dimensional model was guided by a set of technical requirements, all of which were met in the final model by using the finite element code ABAQUS (6.13). The verification process presented. Therefore, increases the confidence in its results. Understanding the responses of rigid airfield pavement under such conditions are essential in developing new pavement design procedure and more advanced remedial measure for the present pavements system.
Ahmed E. Abu El-Maaty, Ghada M. Hekal, Eman M. Salah El-Din, Saad El-Hamrawy

Effect of Construction Induced Cracks on Tensile Strength and Bonding Between Asphalt Concrete Layers of Pavement Under Different Temperatures

Pavement designers consider traffic loads and climate conditions to be the most important variables governing the long term performance of asphalt pavement. However, research conducted at Carleton University found that construction methods can also affect the long term performance by creating surface hairline cracks that allow water to penetrate the asphalt layer, which destroys bonds in the asphalt and between pavement layers. This paper presents the results and major findings of an experimental investigation performed on large scale asphalt slabs extracted from newly laid pavement. For the first time, our research included evaluating the bonds between asphalt layers built in the field. The laboratory study included testing the slabs under direct tensile stress, and subjecting them to temperatures ranging from room temperature to −20 °C. The testing included a total of 100 asphalt samples 300 mm long and 100 mm wide, with a thickness of 50 mm for single layer and 100 mm for double layers.
The results showed that construction induced cracks affect the tensile strength of new asphalt roads, and can weaken the bond between the upper and lower layers when overlays are constructed. These issues impact maintenance and rehabilitation investment, and waste the new overlay.
Graziela Girardi, Mohammad Ramezani, A. O. Abd El Halim

Effect of Wet-Dry Cycle on Durability of Cement-Stabilized Recycled Pavement Base Aggregates

Resilient Modulus (MR) is one of the most important stiffness parameter to determine the thickness of a pavement layer (AASHTO 2003 pavement design guideline). At present, the design procedure does not consider the effect of deterioration of pavement layers due to seasonal variations. Recent studies conducted by researchers on the variability of MR with wetting-drying (WD) and freeze-thaw (FT) cycles show that long-term durability is an important criterion to be considered in designing pavement base with recycled materials. However, limited study has been conducted to evaluate the effect of environmental deterioration on the reclaimed asphalt pavement (RAP) and recycled crushed concrete aggregate (RCCA) mixtures stabilized with cement. The objective of this research is to evaluate the durability of 50% RAP-50% RCCA mixtures stabilized with 4% and 6% cement subjected to 0, 4, 8, 16 and 30 wetting-drying cycles. Wetting and drying cycles were applied to the specimens after curing them for 7 days. Resilient modulus tests were then conducted on the specimens at the end of these specified number of cycles. Environmental tests were also conducted to assess the effect of WD cycles on the leachate quality. These tests included total suspended solids (TSS), total dissolved solids (TDS), turbidity, chemical oxygen demand (COD) and pH. Tests results indicated that with the increase in the number of WD cycles, the value of MR decreased by about 11% of the initial value at the end of 30 cycles. Results obtained from the environmental tests after 30 WD cycles were found to be within the permissible values provided by EPA guidelines.
Saif Bin Salah, Sahadat Hossain, Mohammad Faysal, Mohammad Sadik Khan, Carla Maria Flores

Full Depth Reclamation (FDR) to Repair Road Damaged in the Energy Sector

Rehabilitating the roadways in the energy sector is one of Texas Department of Transportation’s (TxDOT) top priority activities and is also a high profile activity attracting a lot of legislative oversight. Adding to this problem is that many of these roadways are often in remote areas where there is no access to quality paving materials. In addition, there is no detour and the roadway must be opened at end of work day. The FDR offers great potential to stabilize roadways in-place making use of existing materials and determining the optimal stabilizing agent to make these roadways structurally adequate. Although TxDOT has utilized the FDR for several decades, the performance results vary. Some FDR projects last over 10 years without any distress. However, there were several premature failure occurred within one month of trafficking. This paper presented a successful FDR project using foamed asphalt. The main reason of using foamed asphalt is its one-pass operations that can open to traffic immediately after compaction. Lab mix design was conducted to determine the optimum asphalt and cement contents. FWD tests were conducted to evaluate the change of foamed asphalt base. The determined modulus from foamed asphalt base can be used for future design purpose. The backcalculated moduli for foamed asphalt base increased from 493 ksi (2 weeks after construction) to 800 ksi (6 months after construction). District personal is very pleased with the performance of FDR using foamed asphalt.
Dar Hao Chen, Tom Scullion, Kun Li

Prediction of Strength and Stiffness Properties of Recycled Pavement Base Materials Using Non-destructive Impact Echo Test

Reclaimed Asphalt Pavement (RAP) and Recycled Crushed Concrete Aggregates (RCCA) are being used increasingly as an alternative to the conventional base materials in pavement construction. However, product variability and lack of strength-stiffness characteristics are limiting the use of recycled materials in pavement application. A non-destructive evaluation technique could provide a better quality control tool for the highway officials during the construction. Therefore, the objective of the current study is to develop a correlation between the non-destructive impact echo and Unconfined Compressive Strength (UCS) test for RAP and RCCA materials. Both impact echo and UCS tests were performed on specimens prepared with 100% RAP and RCCA. The RAP and RCCA were separately treated using four (0, 2, 4 and 6%) different dosages of Portland cement. Based on the experimental results, the range of P-wave velocity was found between 175 m/s to 475 m/s, the compressive strength varied between 67 kPa to 2860 kPa and tangent modulus range was 19 MPa to 280 MPa. Dynamic modulus of elasticity was also calculated from the P-wave velocity, density, and Poisson’s ratio. At 4% and 6% cement contents, dynamic modulus of elasticity was within 10% of the tangent modulus found from UCS test. At 0% and 2% cement content, higher variation was observed. Inadequate fines to fill the voids might be the reason of lower P-wave velocity at 0% and 2% cement contents. This could eventually have predicted lower values of dynamic modulus.
Masrur Mahedi, Sahadat Hossain, Mohammad Faysal, Mohammad Sadik Khan, Asif Ahmed

Predicting Performance of Flexible Pavement Using Finite Element Method

The modern vehicles having very high loads and high tyre inflation pressures are the outcome of improvements in the automobile segment. The combined effect of higher tyre pressure and excessive loading leads to premature failure of roads in the form of potholes, cracking, etc. which has drastically brought down the life of a road. One of the major cause that contributes to road accidents is deteriorated condition of roads in terms of cracking, potholes and uneven surface due to rutting. This research documents the use of finite element analysis by treating tyre-pavement interaction as an axisymmetric two-dimensional problem. For predicting performance of flexible pavement which is subjected to different inflation pressures, loading conditions, variation in thickness and material properties of different layers in the flexible pavement, modeling is done using a developed program in FORTRAN. From the analysis, it is observed that the value of ε t at bottom of BL increases by 215.33% and 254.48% by an overloading in standard axle load by 2 times and 2.5 times respectively. Also, a noticeable increase of around 252.95% and 336.40% in ε v at top of subgrade is seen due to overloading the standard axle load by 2 times and 2.5 times respectively. It is noticed that the damage caused to a pavement by an overloaded axle load of around 2 times or 2.5 times the standard axle load is much more than the damage by the standard axle load. From the analysis, it is noticed that the pavement starts deteriorating earlier as the overloaded vehicles are consuming the designed life of the pavement, so from the present work, it is concluded that the pavement should be designed considering the uncontrollable overloading of the vehicles instead of relying on the standard or legal limits.
Anand B. Tapase, M. S. Ranadive

Implementation Initiatives of the Mechanistic-Empirical Pavement Design Guide in Countries with Insufficient Design Input Data – The Case of Lebanon

The new mechanistic-empirical pavement design guide (M-EPDG) delivers a state-of-the-art and practice design procedure that eliminates the AASHTO 1993 empirical design procedure deficiencies. Huge advances with respect to traffic inputs, materials characterization and environmental impacts are integrated in its performance prediction methodology. However, achieving accurate and reliable design and performance prediction results using the M-EPDG requires extensive data collection. This presents researchers and practitioners with major challenges as they plan and work towards full adoption of the M-EPDG. Similar to the case of highway agencies in the U.S., it is imperative for highway agencies outside the U.S., such as those in the MENA region, to initiate a comprehensive and customized implementation plan for adoption of the M-EPDG. The main objective of this study is to present a methodology for facilitating the adoption of the new design guide in such countries. Firstly, the paper presents the current flexible pavement design practices in the countries lacking design input data sufficient for utilizing the M-EPDG. Then, the paper describes the efforts required to gather the necessary input data and presents an approach for utilizing the M-EPDG software. Sensitivity analyses and implementation initiatives are performed for each of the M-EPDG AASHTOWare design input modules, with Lebanon serving as a case study. Performance results are used to determine which of the design parameters require country-specific information, and proposes a plan for acquiring this information and investigates its effectiveness and reliability. Finally, the paper presents recommendations for implementation of the M-EPDG in such countries.
Ghassan R. Chehab, Rana Hajj Chehade, Lamis Houssami, Rayane Mrad

Structural Evaluation of Flexible Pavement Using Non-destructive Techniques in Low Volume Road

Low volume roads (LVR) are most accessible road network in India, and it contains thin asphalt surface (less than 100 mm). For this type of roads, a light weight deflectometer (LWD) may be useful for structural evaluating the pavement layer moduli and overlay design. In some parts around the globe, still uses conventional Benkelman beam deflectometer (BBD) method for structural evaluation purpose. In this paper, an experimental stretch 550 m length and width 7 m was considered for structural evaluating the pavement using LWD and BBD. Pavement deflection response data collected using a Benkelman Beam deflectometer (BBD) and lightweight deflectometer used to identify structural integrity of pavement. Deflections collected by LWD using 20 kg falling weight with radial geophone spacing 300 mm and 600 mm are used in this study. The proposed methodology for overlay design using LWD, LWDmod, and KENLAYER software’s results was discussed. Obtained backcalculated layer moduli results are used to calculate critical stresses and strains generated by standard axle load of 8 tons by using KENLAYER software. The LWDmod overlay thickness analysis ranges from 28.00 to 180 mm, and BBD based calculated overlay thickness ranges 10 to 210 mm were observed. The correlation of deflection values between LWD and BBD was found with R2 value of 0.741. The practical shortcoming of deflection correlation between BBD and LWD may be overcome by using more data points of LWD in Indian conditions for further research.
Vinod Kumar, Sunny Deol, Rakesh Kumar

Application of Artificial Neural Networks for Hot Mix Asphalt Dynamic Modulus (E*) Prediction

The hot mix asphalt (HMA) dynamic modulus (E*) is a fundamental mechanistic property that defines the strain response of asphalt concrete mixtures as a function of loading rate and temperature. It is one of the HMA primary material inputs for the Pavement ME Design. The laboratory testing of dynamic modulus requires expensive advanced testing equipment that is not readily available in the majority of laboratories in the Middle Eastern countries, yet some of these countries are looking for implementing new pavement design methods such as Pavement ME Design. Thus, many research studies have been dedicated to develop predictive models for E*. This paper aims to apply artificial neural networks (ANNs) for E* predictions based on the inputs of the models most widely used today, namely: Witczak NCHRP 1-37A, Witczak NCHRP 1-40D and Hirsch E* predictive models. It also aims at investigating the effect of the different hierarchical binder input levels of the Pavement ME Design on the E* prediction accuracy. A total of 25 mixes from the Kingdom of Saudi Arabia (KSA), and 25 mixes from Idaho state were combined together in one database containing 3720 E* measurements. The database also contains the volumetric properties and aggregate gradations for all mixes as well as the binder complex shear modulus (Gb*), phase angle (δ), and Brookfield viscosity.
The results of this study show that using the same input variables of the three models, the ANNs models generally yielded more accurate E* predictions. Finally, there is a strong evidence of the influence of binder input level on the dynamic modulus E* prediction accuracy of both regression and ANNs.
Sherif El-Badawy, Ragaa Abd El-Hakim

Potentials for Using Mechanically Activated Concrete Powder in Stabilized Granular Pavement Mixtures

Stabilization of granular materials is a common practice in transport infrastructure structures. It is used mainly for improving the roadbed or for achieving higher performance of base layers. The traditional approach is to use cement, lime hydrated, hydraulic road binder or standard fly-ash in mixing with soil or granular material (gravel) to get a hydraulically bond mixture which then shows improved bearing capacity and better resistance to water immersion or frost impacts. However, most of the binders (especially cement) show higher carbon footprint and represent therefore increased socio-economic cost of the structure. On the other hand, yearly many old structures are demolished and waste is created often containing huge volume of concrete material, which can be crushed and reused as a granular material. At the same time this material can be treated by high-speed milling (disintegration) process and it is possible to achieve a partial reactivation of the cement components in the concrete. This paper presents some of the achievements in soil stabilized materials and cold recycling mixtures where activated micromilled concrete powder/fine ground recycled concrete (FGRC) was used as an active filler or a binder substitute. The effect of the micromilled concrete powder with respect to its content or combination with other binders or additives is described further. Regular tests like Proctor Standard, CBR or compressive strength, indirect tensile strength or stiffness determination are done. The effect to act as an alternative binder is studied not only it terms of used content, but also with respect to its impact during test specimen curing. Finally, some recommendations are given in this paper with respect to the practical application of such material.
Jan Valentin, George Karráa, Jan Suda, Jakub Šedina, Pavel Tesárek, Zdeněk Prošek

Pavement Modification Using Enzymatic Lime

Soil samples containing different clay fractions were subjected to lime stabilization, enzyme stabilization and enzymatic lime stabilizations in the laboratory. Unconfined Compressive Strength Tests were conducted to determine the optimum dosages of stabilizing agents. California Bearing Ratio Tests were then performed on samples stabilized with optimum dosages of lime, enzyme, and enzymatic lime respectively. These stabilized samples were tested at different periods of curing and showed that enzymatic lime stabilized soils delivered comparatively higher strengths. Based on the results of CBR tests, the modified thickness of flexible pavement is also discussed.
Greeshma Nizy Eujine, S. Chandrakaran, N. Sankar

Numerical Modeling of Heat Production for a Snow-Melting System Using Geothermal Energy in North Dakota

This paper is focused on heat production modeling for a proposed snow-melting system using shallow geothermal energy in North Dakota. The paper presents computations for the heat that is required for a pavement snow-melting system based on averaged climatic and precipitation data and using Chapman and Katunich’s equation. Based on seasonal heat requirements, finite element analysis using COMSOL was performed to simulate the heat extraction process whereby heat is transferred between the soil and the heat collection pipes in a constant subsurface temperature zone. In addition to the thermal properties of the soil, both the fluid in the pipes and the characteristics of the pipes themselves are shown to be significant factors for the heat extraction process. The results of the numerical analysis also indicate that a high level of thermal conductivity of the soil is desirable for a successful heat collection system. Compared to costly studies that involve full-scale prototypes, simulations via numerical modeling can provide cost-effective insights into the important components of a successful snow-melting system.
I-Hsuan Ho

Assessment of Interlayer Bonding Properties with Static and Dynamic Devices

Although static interlayer bond testing has been established for quality control during recent years its significance has been questioned and in the wake of this discussion several more realistic dynamic testing devices have been proposed with the purpose of determining the interlayer bond properties not only at failure but also during service life. The Germany testing device developed at the University of Dresden even found entrance into the European test standards and the device has been commercially available for a couple of years. The paper presents an investigation dealing with the importance of interlayer bond testing for performance evaluation and focuses on a comparison of results from static and dynamic interlayer bond testing. Based on the comparison of static and dynamic bond testing the benefits from dynamic testing will be evaluated and a recommendation for the dynamic testing procedure will be presented.
Christiane Raab, Elise Fourquet, Omar Abd El Halim, Manfred N. Partl

Wavelet-Spectrogram Analysis of Surface Wave Technique for Quick NDT Measurement on Surface Layer of Pavement

Reliable assessment of in situ pavements stiffness is an important aspect in effectively managing a pavement system. The aim of this paper is to propose the new procedure, namely the wavelet-spectrogram of surface wave (WSSW) technique for non-destructively measurement of elastic modulus on surface layer of a pavement system. Using two receivers, surface wave propagation on pavement surface was recorded and transformed into in frequency domain by wavelet analysis. For this analysis, a derivative Gaussian wavelet was selected as an appropriate mother wavelet for seismic waveform propagating along pavement surface. Thus, an interactive 2-D plot of time-frequency spectrogram consisting of wave-energy spectrum was simultaneously generated. CWT-filtration method was implemented in order to reduce the effect of noisy signal recorded during measurement. From selected wave spectrogram, the unwrapped phase different spectrum was generated to obtain phase velocity which was performed by least-square linear regression. Finally, the elastic modulus of pavement surface layer was calculated from a modified relationship between phase velocity, Poisson ratio and density of pavement surface layer. The results show that the proposed technique is able to measure in situ elastic stiffness of the surface layer. In addition, the change of the surface layer stiffness is also able to be monitored. The stiffness (elastic modulus) produced by the WSSW technique is classified as a modulus at very low strain level.
Sri Atmaja P. Rosyidi

Thermal Energy Harvesting from Asphalt Roadway Pavement

This study is aimed at developing energy harvesting system for electrical power generation from asphalt pavement roadways. Energy harvesting technologies from roadways is a new research arena which involves technologies that capture the wasted heat energy in pavements, accumulate and store it for later use without depletion of natural resources. The temperature of pavement surface rises up to 50 °C to 55 °C in the summer (depends on geographic location) due to the effect of the solar radiation. Soil temperature is consistently stabilized at 27 °C creating a thermal gradient profile across pavement layer structure. This Thermal gradient is a potential source of energy that can be harvested. The proposed system collects heat energy from the pavement surface and transfers to thermoelectric generators module along the pavement side. Field demonstration, laboratory testing and finite element simulation suggested that electric energy is approximately 10 mW per thermoelectric module (6.4 cm × 6.4 cm dimension). At scalable system, the produced energy can be used for LED street illuminating or empowering roadway monitoring devices inserted within the pavement in off-grid areas. Furthermore. Changes in the response of these sensors can be used as a means of monitoring the health of the pavement layers, where these sensors are installed. This paper demonstrates finite element simulation on the capability of the proposed system and preliminary findings on the output power generation.
Utpal Datta, Samer Dessouky, A. T. Papagiannakis

Monitoring the Impact of Micro Cracks Healing Cycles on the Deformation of Asphalt Concrete Under Repeated Loading

The micro cracks healing property in asphalt concrete is considered as a good start for understanding and controlling the durability issue of the pavement. However, the impact of repeated micro crack healing cycles have not been investigated thoroughly. In this work, cylindrical asphalt concrete specimens of 100 mm diameter and 63 mm height have been prepared in the laboratory using Marshall method. Specimens were divided into two groups. The first group was subjected to repeated indirect tensile stresses, while the second group was subjected to repeated double punch shear stresses (both at 25 °C) to initiate micro cracks within the specimens using controlled stress mode of loading for 0.1 s followed by rest period of 0.9 s for specified load cycles. Afterword, Specimens were subjected to external heating in an oven at 60 °C and allowed to heal for two hours, conditioned at 25 °C for two hours, then subjected to another course of repeated tensile or shear stresses. The healing process was continued for two successive courses of loading and heating. The deformation of the specimens was monitored through continuous video capture. The impact of asphalt content, type of test, and healing cycles on the permanent deformation have been analyzed. It was concluded that higher deformation of 16% could be detected under tensile stresses as compared to that under shear stresses. The healing cycles causes (7–30) % and (16–37) % reduction in permanent deformation under repeated (ITS) and repeated (PSS) respectively.
Saad Issa Sarsam, Hanan Kadim Husain

A State-of-the-Art Review of Different Conditions Influencing the Behavioral Aspects of Flexible Pavement

The paper provides a state-of-the-art review of different conditions influencing the behavioral aspects of flexible pavement. The conditions which influence the pavement behavior are loading intensities and tyre pressure intensity, environmental conditions, surface and subsurface temperature, seepage, thickness combinations of different component layers, material properties, etc. Current pavement design and analytical procedures are discussed and questioned. The life of the road is theoretically designed for repetition of standard axle load, wherein, negligence in consideration of overloaded vehicles and high tyre inflation pressures even up to 1 MPa is noticed. The latest developments in the design and analytical procedures of pavements are highlighted. An overview of finite element modeling efforts involving different aspects is also presented. A combined effect of various actual conditions in the field affecting the pavement performance needs to be studied in details, therefore, there is a demand for an application of analytical tool which can accommodate the details of the complex system. In this connection, it should be noted that the versatile finite element solution technique holds a bright promise. Therefore, it is proposed to discuss at length the application of the finite element method towards the design of the flexible pavements.
Piyush G. Chandak, Anand B. Tapase, Sabir S. Sayyed, Abdulrashid C. Attar

Performance Testing of Paving Mixes for Libya’s Hot and Arid Conditions, Using Marshall Stability and SUPERPAVE Gyratory Compactor Methods

Asphalt Concrete Pavements (ACP) in Libya’s southern desert regions suffer two major challenges: the hot and arid climate, with road surface temperatures reaching 65–70 °C, and air humidity below 50%. As such, ACP in Libya develops excessive deformation. The lack of modern testing methods and in-situ monitoring during the use-phase make predicting the performance of new mix designs difficult. This paper aims to provide comparative performance data on paving mixes of different Libya-sourced bitumen grades under simulated climate conditions, and to compare the usefulness of empirical testing methods (Marshall) to Performance Graded methods. Two mixes, one using Bitumen 60/70 (B 60/70) and the other using PG70-10, are assessed with Marshall Stability and Super Gyratory Compactor tests, using modern equipment at the laboratory of the ETS (École de technologie supérieure) faculty of engineering of the University of Québec, Canada. The performance of PG70-10 mixes is found to be superior to that of the performance of the mixes using B 60/70. The PG70-10 mix performed within the requirements of lower-volume roads (≤300 vehicles per day). Also, the results of the Super Gyratory Compactor tests are found to be a better indicator of in-service performance than those given by Marshall Stability tests. These results provide a foundation for performance-testing of different paving mixes that varied in sand and filler content; these are available for applications in similar arid climates, and may provide significant savings by allowing engineers to substitute local materials, such as the abundant rounded sand in southern Libya, for more scarce and costly materials, such as manufactured aggregate.
Fathi S. Almadwi, Gabriel J. Assaf

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