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Top-down cracking (TDC) as a severe type of cracking has been widely reported in pavements with heavy traffic loads and mixtures sensitive to rutting damages. Since the likelihood of TDC increases as a result of weak mastic, semi-flexible pavements (SFPs) grouted with cement asphalt emulsion pastes (CAEPs) were introduced in this study to evaluate its performance in prevalence or mitigation of this problem. Using laboratory tests, the material properties and rutting resistance of SFP with CAEPs were compared to the conventional asphalt mixture. Then comprehensive finite element (FE) models were employed to investigate the influence of rutting damage severity on non-uniform contact stresses and critical TDC responses. Considering various degrees of rutted surface, the critical locations of TDC were predicted based on maximum transverse and shear strain responses. The results demonstrated that the presence of a rutted surface induced the near-surface responses significantly, and the more severe rutting, the higher propensity for TDC. Besides, the location of TDC initiation was greatly influenced by the severity of the rutted surface. Finally, based on SFP performance in the surface layer, CAEP40 was recommended as the best grouting material to reduce the likelihood of TDC and rutting damage development. [ABSTRACT FROM AUTHOR]

Highway pavement construction with recycled solid waste materials had become a sustainable topic of great concern recently, due to the potential environmental and economic benefits behind. This review focused on the emerging Life Cycle Assessment (LCA) and Life Cycle Cost Analysis (LCCA) studies concerning the recycling of solid waste in highway pavement. Firstly, based on the existing studies, the application of most recycled solid waste materials (e.g. recycled asphalt pavement, steel slag and coal fly ash) in highway pavement performed satisfactorily from the environmental and economic perspectives, concretely manifested in the reduction of energy consumption, greenhouse gas emissions, costs and other indicators. However, several factors, such as lengthened transport distance of recycled waste solid materials and potential leaching of heavy metals, might hinder the recycling. Moreover, it was necessary to pay more attention to pavement use phase, allocation procedure and transport distance of recycled solid waste materials, which had significant impacts on LCA result. In terms of existing LCCAs, the importance of analysis period and discount rate was highlighted and the most practical economic indicator was Net Present Value (NPV). For future study, allocation was still an important issue for future LCA studies and further sensitivity analyses could focus on the selection of transport modes (in LCA), analysis periods and discount rates (in LCCA). Meanwhile, future research should emphasis on the recycling of solid waste in pavement maintenance and rehabilitation projects rather than new construction. A multi-criteria assessment integrated LCA and LCCA as well as other considerations (e.g. an advanced risk assessment) was recommended to determine the most sustainable recycling scenarios. [ABSTRACT FROM AUTHOR]

The interlayer bonding between pavement layers has significant effects on the pavement performance responses during the traffic loading. The insufficient bond adhesion may increase the transferred stresses and extended strains in the relevant layers when applied to traffic. Over the last 30 years, many research studies focused on these related fields and found some useful conclusions to help conduct field practices of tack coat materials. In this review, it was found that the shear mode tests were the most common methods to verify bond strength and some non-destructive tests were becoming more and more useful to investigate tack coat properties. In addition, some test parameters including shear strength, cracking resistance and fatigue performance were used to assess tack coat properties. The intrinsic factors such as tack coat type, application rate, curing time and the application conditions including temperature, moisture, and surface texture together influenced the characteristics of interlayer bonding. However, pavement failure mechanisms and the interactions between influence factors are needed to be investigated in the future. [ABSTRACT FROM AUTHOR]

In this study, the objective was to conduct an investigation of Superpave mix design characteristics of WMA technologies in terms of various high percentages of reclaimed asphalt pavements (RAPs). One PG 58-28 binder, two PG 64-22 binders, and two RAP sources were selected from South Carolina. In addition, three mix technologies (e.g. hot mix asphalt (HMA), foaming technology, and Evotherm additive) were employed to produce the mixtures. Meanwhile, four RAP contents of 20%, 30%, 40%, and 50% (by weight of total mixture) were utilized to blend with virgin materials. 36 Superpave mix designs were conducted to explore the volumetric characteristics of various mixtures. In this study, the results indicated that, all mixtures have an optimum asphalt content (OAC) less than 5.0%, and most of these values are close to a minimum OAC value of 4.5% set by South Carolina Department of Transportation (SCDOT). No noticeable increases at the mixing and compaction temperatures for these mixtures containing a higher percentage of RAP (i.e., over 40%) were found in this study. In addition, the voids in mineral aggregate (VMA), voids filled with asphalt (VFA), dust/asphalt ratios, and moisture susceptibility meet the requirements of SCDOT’s specifications. Therefore, these specific mix designs could be used as the guidelines for developing a set of specifications for a higher percentage of RAP in terms of warm mix asphalt technology. [ABSTRACT FROM AUTHOR]

Fuzzy logic and expert system techniques are effective in evaluating the flexible pavement distress. Distress classification has usually been performed by visual inspection of the surface of the pavement or from the data gathered by automated distress measuring equipment. Consistency in this process can be increased and subjectivity is minimized by using an expert system. A methodology has been developed that uses fuzzy logic for the categorization of distresses. An expert system was developed in C language using fuzzy logic for reasoning. The objective of the developed methodology was to use automated techniques for quick, efficient, and consistent classification for flexible pavement distresses using data from the automated distress measuring system. The developed expert system has been designed to be used as a module within a pavement management system. This will help to completely automate pavement condition evaluation and strategy development for maintenance and rehabilitation of pavements, thus eliminating subjectivity and inconsistency in the process. According to the experts, mostly highway officials, the differences between the actual measured data and results from fuzzy logic expert system approaches were well within acceptable ranges. [ABSTRACT FROM AUTHOR]

In many parts of the world, highway officials are utilising crumb rubber and reclaimed asphalt pavement (RAP) in order to save money, protect the environment, and improve the life of asphalt pavement. However, due to the use of these materials, the effects of moisture damage should be investigated for rubberised asphalt concrete (RAC) mixtures containing RAP. The objective of this research involved investigating the moisture susceptibility of RAC containing RAP. The testing conducted included the determination of binder viscosity, toughness and indirect tensile strength (ITS) analysis. Several mixtures containing different crumb rubber types, two different RAP sources and various percentages of rubber and RAP were evaluated. The results indicated that, in general, the additional of RAP was beneficial in improving the ITS values and reducing the moisture susceptibility of the mixture although the addition of crumb rubber had a slightly negative effect. [ABSTRACT FROM AUTHOR]

In general, crumb rubber modifier-modified binders (CRM binders) have better performance properties than base binders and thus, are becoming more widely used in pavements in a few states. However, the mechanism by which the interaction between the asphalt base binder and the CRM blends added takes place has not been fully characterised. In this study, the surface areas of CRM were at first measured using the Brunauer, Emmett and Teller (BET) tester. Second, 108 CRM binders were produced using different combinations of CRM blend variables and mixing conditions and consequently tested for their viscosity at 135°C. The influence of the surface area and the average size of the CRM blends on the viscosity of the CRM binders was statistically investigated. Results from this study indicated that: (1) the surface area of the ambient CRM is almost twice as large as that of the cryogenic CRM, leading to an increase in the viscosity up to 16-58% over cryogenic CRM binders and (2) the viscosity of the CRM binders has a moderate correlation with both the surface area and the average size of the CRM blends, but is prevailingly influenced by the average size of the CRM blends. [ABSTRACT FROM AUTHOR]

Abstract: Over the years, recycling has become one of the most attractive pavement rehabilitation alternatives, and different recycling methods are now available to address specific pavement distresses and structural needs. The objective of this study was to investigate and evaluate the engineering properties of crumb rubber size and type influences on reclaimed asphalt pavement (RAP) mixtures. The experimental design for this study included the use of three rubber sizes and two rubber types (ambient or cryogenic) in the mixture containing 25% RAP mixtures. In this study, the results of the experiments indicated that the addition of crumb rubber was helpful in increasing the voids in mineral aggregate (VMA) in Superpave mix design and improving rutting resistance of mixture regardless of rubber size and type. On the other hand, indirect tensile strength (ITS) values show no significant difference for mixtures made with three type rubber sizes. However, the increase of rubber size, regardless of rubber type, reduced the resilient modulus values but extended the fatigue life of the modified mixtures. [Copyright &y& Elsevier]

During the pavement life cycle, construction and rehabilitation activities and vehicle-road interactions provoke extensive environmental, economic, and social impacts. Therefore, decision-making systems are developed to derive optimal construction and rehabilitation plans, alleviate the environmental and economic burdens, and simultaneously increase the social benefits. The past studies have developed management systems with different management approaches, optimization tools, objectives, constraints, prediction models, performance indicators, evaluation techniques, evaluation boundaries, and risk paradigms. This study presents and discusses their diverse perceptions and methodologies for these management system elements. Besides the drawbacks in the adopted perceptions, the study presents the further investigations required to develop more efficient systems that optimally achieve the environmental, economic, and social objectives. The review is limited to studies of the international journals undertaken in the past 20 years, which conferred the project-level management of construction and rehabilitation of flexible pavements. [Display omitted] • Impact of Management system on construction and rehabilitation plans. • Roles of management system objectives, constraints, models, and indicators. • Decision variables of construction and rehabiliatation plans. • Cost subsets and environmental burdens factors fostered in the management system. • Constituting risk assessment in decision-making process. [ABSTRACT FROM AUTHOR]

[Display omitted] Traffic Speed Deflectometer (TSD) is primarily capable of evaluating the pavement conditions at the network level with regard to the structural capacities. This paper mainly reviews the utilization of TSD for the pavement structural evaluations. With the Doppler lasers configured in a specific truck, TSD can measure the deflection velocity (slope) at a traffic speed. The measured deflection can be calculated by either area under the curve (AUTC) method or Euler–Bernoulli beam (EB) method. Moreover, the pavement moduli backcalculated by either 3D Move simulation or the Artificial Neural Networks (ANNs) from TSD measurements tend to well correlate those backcalculated from FWD measurements. It is noted that structural capacities derived from TSD measurement were reliable in assessing the pavement conditions. Additionally, the pavement roughness has a significant effect on TSD measurements. Therefore, Traffic Speed Deflectometer has a promising applied prospect in pavement structural evaluations. [ABSTRACT FROM AUTHOR]

Increasing aircraft loads and landing frequency are becoming challenges to airfield pavement material design. The objective of this study was to give overall performances of multiple-polymer asphalt mixtures containing anti-rutting agent (ARA), polyethylene (PE) and styrene-butadiene-styrene (SBS). A series of binder and mixture tests were conducted to investigate mechanical performances, the life-cycle assessment (LCA) was used to evaluate environmental impacts. It was found that the addition of multiple-polymer resulted in excellent high temperature performance with high rutting factor and softening point, but it led to large energy consumption and GHG emission. Also, SMA-13 mixture had larger environmental impacts than AC-20 due to higher binder content. The radar chart and rheology-environment performance ratio (REPR) were proposed to compare rheological performances and environmental impacts with respect to polymer content and test temperatures. The field practice of HMA overlay selected 0.2% of ARA and 0.5% of PE by weight of asphalt mixture as the optimal polymer content. It was found that the multiple-polymer mixture had a great resistance to permanent deformation and enough resistances to moisture damage and low temperature cracking. However, the quality control of pavement construction was not effective because air voids of cored specimens exceeded the requirement even though other properties were satisfied with the requirements. In addition, compared with HMA, the WMA compacted at 155 °C had lower air void and maximum bending strain. Therefore, the application of WMA additives in multiple-polymer modified asphalt mixture should be further studied. [ABSTRACT FROM AUTHOR]

Abstract: Surface modification of ground rubber tire (GRT) was performed by bulk polymerization of acrylic acid (AA) without using any initiator. Two different sizes of GRT were used for this project: 40 mesh (often used in Asphalt Industry), and 300 mesh which is used in other industries. The concentration of the monomer (acrylic acid), reaction temperature and the reaction time (1 and 3h) are important factors on the grafting degree – especially because our goal was not to use any initiator during the reaction (there are well known procedures for grafting of polymers by using different type of initiators). Our effort was towards simplifying the grafting process and to make it much faster and less expensive (more acceptable by the industry). The microstructural and morphological changes of the GRT particles were characterized by Attenuated Total Reflectance Fourier transform infrared spectroscopy (ATR-FTIR), scanning electron microscopy (SEM), viscosity test of the modified asphalt binder [PG 64-22 asphalt binder with virgin GRT particles (40 and 300 mesh), and PG 64-asphalt binder with AA treated GRT particles of the same size]. Dynamic shear rheometer (DSR) test of the modified asphalt binder was also performed. Thermal gravimetric analysis (TGA) was investigated on untreated and AA treated 300 mesh GRT particles. Results showed that with the addition of surface modified GRT particles increased the viscosity and failure temperature values of asphalt binder regardless of binder source and grade. [Copyright &y& Elsevier]

Digital image processing technology has been widely applied in various fields, and it is also increasingly used in pavement distress detection in recent years. The objective of this review article is to help researchers to select the most appropriate digital image processing technology (image acquisition equipment, processing, recognition technology and etc.) to study the pavement distress detection. Firstly, a proper application of the current image acquisition equipment is presented, and the advantages and disadvantages are compared. Secondly, the problems encountered in the practical application of image processing technology in pavement detection are presented. Further, the problems need to be solved in the future research are suggested, including cracks detection, pavement texture detection, temperature segregation detection, rutting detection, pothole detection, and joint faulting detection. In conclusion, the state of the art in pavement detection by digital image processing technology is summarized and proves that the digital image processing technology has become a promising method for pavement detection and materials analysis. [ABSTRACT FROM AUTHOR]

To solve the frequent urban flood problems, China has put forward a novel city strategy-Sponge City. It is a kind of water resource management strategy and method, which can adapt to the changes of rainwater like a sponge, so as to reduce the occurrence of flood problems. This paper reviewed the initiative and development of sponge city. It analyzed the problems faced by sponge city construction and possible solutions. In addition, pavement material was an important part of sponge city construction. This paper also reviewed the application and development of pavement materials in sponge city. Firstly, the commonly used permeable pavement materials were introduced including permeable asphalt concrete, permeable cement concrete, permeable brick, and novel pavement materials. To meet the requirements of "infiltration, retention, purification, evaporation, and drainage", the pavement materials were designed to be porous. The pore characteristics were studied, including but not limited to porosity and pore size, etc. In addition, environmental assessment and economic analysis were conducted. It was found that the permeable pavements were not necessarily more environmentally friendly than traditional pavement, but they did have some obvious benefits such as water purification, traffic noise reduction, Urban Heat Island (UHI) mitigation, and waste materials recycling. There was a controversy about whether permeable pavements were more economical than traditional pavements. Finally, this paper looked forward to the future development of pavement materials in sponge city, which called for better hydrological performance and wider application range. • The sponge city strategy has good application value and development prospect. • Sponge city uses permeable asphalt concrete, permeable cement concrete, permeable brick, and novel permeable materials. • Pore characteristics have a significant impact on mechanical and hydrological properties of permeable pavements. • Permeable pavement has obvious environmental benefits, including the purification of water and air, noise reduction etc. • The future studies of pavement materials in sponge city are recommended to focus on better hydrological performance. [ABSTRACT FROM AUTHOR]

• The pavement sensible heat accumulation is a more suitable index to thermal behavior. • Reflectance degradation and long-term performance should be concerned in the pavement. • The urban canyon effect has a negative consequence on the advective turbulence. • The evaporation release increases the air relative humidity of pavement surface. • The application of heat-harvesting pavement requires detailed scrutiny. With the rapid expansion of urbanization around the world, the urban heat island effect embraced an enormous negative impact on megacities, including energy, environment and health conditions. Unfortunately, constructive geometry and human activities of megacities severely intensified the urban heat island phenomenon. Giving the contributions of pavement on the deterioration of urban heat island in megacities, this literature review synthesized the state-of-the-art potential strategies of pavement cooling technologies and applications to mitigate the urban heat island effect. Firstly, the optical-thermal balance on surface and the interior thermal behavior of pavement were comprehensively analyzed. Afterwards, this paper redefined the cool pavement technologies as the passive mitigation strategies, involved the application of reflective pavement, evaporation pavement, heat-induced pavement and phase change materials. Especially, urban canyon impact and urban design were emphasized, which tended to be neglected on the implementations of cool pavement. In addition, the solar collector technologies on the pavement were proposed to sustainably reuse solar energy, acting as active strategies and renewable sources. Typically, representatives of solar collectors, including heat collection and thermoelectric pavement, were described and investigated. Existing research results presented the promising potential of pavement cooling technologies to mitigate the urban heat island impact and renewable energy sustainability. Moreover, prospects were also summarized to show the opportunities and avenues for future study. [ABSTRACT FROM AUTHOR]

• NCRW materials for unconventional joint to reduce water damage to airport pavement. • NCRW materials are polymeric polymers with excellent tensile and bonding properties. • Three typical aging methods were selected to treat the material. • Thermal oxygen, hydrothermal and photothermal effects on the material properties. • Microscopic deterioration in terms of molecular structure and functional groups occurred after aging. A frequent condition of cement concrete pavement at civil airports is slab cavity caused by surface water infiltration, which is a significant safety risk in the regular operation of airports. Mitigation methods to lessen surface water penetration is strongly required. This study examines the tensile and adhesive properties of custom-designed non-oil permeable creep rubber waterproofing (NCRW) material. Direct tensile tests were used to assess the tensile characteristics of NCRW material aged in various modes. Pull-off-healing tests were used to assess the adhesive and self-healing abilities of NCRW material treated with various aging modes to various slabs under various test situations. Fluorescence tests and infrared spectroscopy were also used to explore the aging mechanism of NCRW material. The results showed that NCRW material can offer good self-healing and anti-aging capabilities, as well as great tensile and adhesive properties, so it can meet the needs of airport pavement use. As a result, NCRW material is advised to be used in the airport pavement joints. [ABSTRACT FROM AUTHOR]

[Display omitted] • Optical fiber sensors have better corrosion, electromagnetic interference resistance and signal-to-noise ratio. • Optical fiber sensors can measure the strain, temperature and pressure information of pavement in real time. • The applications of optical fiber sensors in pavement are more and more extensive. Optical fiber sensor (OFS) is a commonly used tool to monitor the serviceability and integrity of pavements. The earliest application of optical fiber sensors in the road can be traced back to the early 21st century, and development of this technique has been extensively studied after that. In view of the increasing demand for pavement nondestructive testing and the rapid development of optical fiber sensor technology, this work summarizes the optical fiber sensors commonly used in road engineering and the classification methodologies. After that, the basic principle of fiber Bragg grating (FBG) sensor and the application of this sensor in the pavement were discussed. Finally, the principle and application of distributed optical fiber sensors (DOFS) in the pavement were included as well. Overall, this review found that FBG sensors can accurately measure and monitor road strain, temperature, pressure and WIM measurement by employing analytical-based methods. Distributed optical fiber sensors can measure pavement crack width, identify the void under the concrete slab, and obtain vehicle load (load size, load moving speed, axle type) and other data. Currently, it has been proved that the installation of the installation of fiber optic sensors on the road surface is an effective method to monitor the integrity of the road structure under traffic, but further tests in real traffic environment to further improve the survival rate of fiber optic sensors and evaluate the accuracy of the measured results are still needed. [ABSTRACT FROM AUTHOR]

The quality of paving binders is of great importance that affects the performance of asphalt pavements. In this study, a rapid performance characterization method was proposed for paving asphalt binders based on the multi-spectra data fusion and chemometrics, with the purpose of quality inspection. Firstly, a data set of paving binder samples considering multiple origins was collected, and various binder performance indicators were obtained with standard tests. Meanwhile, ultraviolet-visible (UV–Vis) and mid-infrared (MIR) spectra of binders were measured and fused at the data level; Secondly, the chemometric method, partial least squares regression (PLSR), was employed to extract information hidden in the fused spectra for the establishment of binder performance prediction models. The quality of most calibrated PLSR models was affirmed, and a good agreement between the measured and predicted performance indicators was observed. In particular, the rapid spectra measurements could save a lot of testing time, and the data fusion of UV–Vis and MIR spectra could provide more satisfactory outputs in most cases; Finally, the repeatability and reproductivity of the proposed method were validated, with standard deviations and coefficients of variation far below limits specified in the specification. The automated spectra measurements, appropriate spectra pretreatments, and the ease of sample preparation and instrument operation could account for this. Above all, the integrated spectra-chemometrics method proposed in this study had the potential of rapid binder performance inspection and quality assurance in practice, especially with more samples from different origins and production technologies collected to extend the existing dataset in the future. [Display omitted] • Spectra measurements of paving asphalts generally took <1 min. • Spectra techniques saved testing time and achieving rapid characterization. • Data fusion of UV–Vis and MIR spectra integrated informative data from both spectra. • Data fusion provided accurate prediction of asphalt performance via chemometrics. • The repeatability and reproductivity of the proposed method and models satisfied the requirements. [ABSTRACT FROM AUTHOR]

• A total of 600,000 wheel passes was conducted on three indoor test pavements. • Rutting and strain characteristics of three pavements were thoroughly analyzed. • Correlations between rutting depth and maximum underlayer strain were investigated. • Semi-flexible pavement presented the highest pavement condition index. • Semi-flexible mixture showed great potential as future airfield pavement material. This study aimed to investigate the rutting and strain characteristics of flexible, semi-flexible (SF) and rigid pavement under the same accelerated loading condition. Specifically, flexible pavement was rubberized asphalt rejuvenated reclaimed asphalt pavement (RAP) pavement (RARR), semi-flexible pavement consisted of Styrene-Butadiene-Styrene modified porous asphalt concrete (SBS-PAC) and cement-based modified grouting material, while rigid pavement was polyurethane (PU) mixtures. An indoor test field was constructed and accelerated pavement tester (APT) was employed to apply continuous wheel loads. Twelve embedded fiber grating strain sensors were placed at the bottom of the surface layer with four in under each type of pavement. In total, 600,000 wheel passes were applied. Results revealed that no rutting hump was discovered for RARR while it was not until the completion of 150,000 wheel passes that PU and SF pavement saw evident rutting humps. As total rutting depth and rutting area increased, the fact that hump depth ratio decreased while hump area ratio increased indicated that rutting humps tended to spread outwards. When it came to maximum micro-strain underneath the pavement layer, it was found that with increasing number of accumulated wheel passes, RARR pavement presented the largest transverse micro-strain while SF pavement presented the largest longitudinal strain. Correlation analyses indicated that maximum micro-strain was in good exponential correlation with maximum rutting depth for RARR, SF and PU pavement. Finally, SF pavement presented the best PCI among the three pavements while PU pavement presented the worst, mainly because of its poor rutting resistance. [ABSTRACT FROM AUTHOR]

Smoother pavement provides a comfortable, safe and economical riding experience to the public and prolongs the life of the pavement with low maintenance costs. Hence, obtaining a smooth pavement is considered a necessity by many transportation agencies around the world. In order to achieve a smooth pavement, smoothness specifications are developed. Smoothness specifications mainly consist of four parts: smoothness measuring equipment, smoothness indices and analysis method, acceptance limits, and incentive/disincentive payment schemes. This paper summarizes smoothness specifications in the United States and various countries around the world and provide an overview on the comparison of smoothness measurement. The smoothness measuring devices, indices, limits and payment schemes vary from country-to-country International Roughness Index is the most used smoothness index in the US and around the world. Inertial profilers are used to measure the pavement profile for smoothness. [ABSTRACT FROM AUTHOR]

As a kind of organic binder, the asphalt emulsion was encouraged to be applied on the highway and airport pavement surface as a preventive maintenance approach. However, the colloid stability and interaction of the thermodynamically unstable coating was not fully investigated and thus resulted in limited application. This research attempted the waterborne acrylate as a novel modifier for emulsified asphalt coating, and investigated the colloid stability and interaction of emulsified asphalt during the phase separation. Firstly, the viscous flow behavior of the asphalt emulsion with waterborne acrylate was evaluated with viscosity test, with the consideration of the droplets interactions between waterborne acrylate and asphalt. Then laser particle size analyzer was employed to evaluate the particle size of dispersed asphalt particles in the dispersion system. Spectrophotometric analysis was conducted to evaluate the sedimentation rate of asphalt particles with a three-dimensional sedimentation kinetics model of absorbance area. The thin film of emulsified asphalt supernatant after demulsification was observed by the digital microscope. Finally, a three-stage model of curing progress in asphalt emulsion was proposed and statistical analyses were conducted to reveal the correlation between various indices. This study proved that the curing process of different emulsion systems were inconsistent. It was promoted that stability and compatibility investigation of waterborne polymer in asphalt emulsion should be taken into consideration and a substantial incorporation would cause colloid coalescence and droplet aggregation, which ultimately affected the properties and microstructure of asphalt coating. [Display omitted] • Morphology of emulsions exhibited fuzzy interface, enlarged droplet sizes distribution. • Flow behavior of emulsion affected the colloid stability before demulsification. • Skeleton polymer structures in asphalt phase formed obviously after incorporation of waterborne acrylate. • Flocculated microstructure in emulsion would affect its flow index. • Various molecular structures of polymers in asphalt emulsion resulted in different absorption sensitivity. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the rutting and strain characteristics of rubberized asphalt rejuvenated reclaimed asphalt pavement (RARR). Accelerated pavement tester (APT) was employed to apply wheel load and tire pressure on the instrumented test field. Seven embedded fiber grating sensors were placed at the bottom of the RARR surface layer to collect strain data. In total, 700,000 wheel passes were applied on RARR pavement in 25 loading cycles. Data on rutting deformation was collected after each loading cycle while strain data was collected throughout the test. Results revealed that RARR pavement presented rapid rutting depth and rutting area increase in the first 100,000 wheel passes. After 450,000 wheel passes, the rut area directly contacted with the wheel load presented an almost constant increasing rate with additional wheel passes, while the influence rut area remained unchanged. As regard to strain at the bottom of the RARR surface layer, it was found that the maximum strain after 100,000 wheel passes reached more than 70% of the maximum strain occurred during the final loading cycle. Large strain differences were found after 300,000 wheel passes and the worst case scenario occurred after 700,000 wheel passes. For strain right under the wheel tracks, results revealed that horizontal strain recovery ability was better than that of vertical strain. Moreover, it was found that wheel loadings actually enhance the strain recovery ability of RARR pavement. This was believed to be caused by the further densification of RARR while loading, which enhanced the elastic recovery ability of RARR asphalt mixture as a whole. [ABSTRACT FROM AUTHOR]

[Display omitted] • The PU prepolymers can chemically react with the base asphalt. • The PU has superior high-temperature stability, adhesion strength, and durability to asphalt. • The anti-aging performance of PU sealants is always a great concern. • High-density PU foam injection has been implemented as an alternative to the conventional cement. • PU-bonded mixture can improve the performance and extend the service life of pavements. In the past decades, Polyurethane (PU) as an emerging polymer material has been widely used to construct, repair, reinforce, and protect civil engineering infrastructures. Meanwhile, various PU-based materials are increasingly employed in pavement engineering for new construction and maintenance, due to their excellent physical and chemical properties. In this review paper, the synthesis method, chemical structure, and engineering properties of PU materials were first introduced briefly. Secondly, the practical applications of PU materials in pavement engineering at present were summarized, mainly including PU-modified asphalt, PU-bonded mixture, PU sealant, and PU foam injection. Finally, the potential economic benefits and environmental impacts of utilizing PU materials in pavement engineering were further discussed towards sustainability. [ABSTRACT FROM AUTHOR]

• The suitable devices should be selected to characterize the image information. • Applications of digital image technologies in micro-analysis, meso -analysis and macro-analysis were reviewed. • Angularity, size, shape, and texture of aggregate could be characterized by imaging systems. • Air void detection of asphalt mixture and cement concrete by various image technologies. • The most common methods for image acquisition devices were CT, digital camera, and scanner. Digital image processing technology has been widely applied in various fields, and it is also increasingly used in pavement material analysis in recent years. The objective of this review article is to help researchers to select the most appropriate digital image processing (DIP) technology (image acquisition equipment, processing technology etc.) to study the pavement materials in multiscale in the laboratory. Firstly, a summary of the current image acquisition equipment (both the micro image acquisition equipment and the macro image acquisition equipment), their suitable ranges are presented, and the advantages and disadvantages are compared. Secondly, the problems encountered in the practical application of image processing technology in the study of pavement materials are summarized. Finally, the problems need to be solved in the future research are suggested, including microscopic analysis, mesoscopic analysis, such as air voids distribution analysis, aggregate shape characteristics etc., and macroscopic analysis, such as gradation detection and crack detection. In conclusion, the state art of pavement material analysis in multiscale by digital images processing technology are summarized. Moreover, more and more studies have proved that the digital image processing technology has become a promising method for pavement materials analysis. [ABSTRACT FROM AUTHOR]