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Intelligent compaction (IC) has emerged as a breakthrough technology that utilizes advanced sensing, data transmission, and control systems to optimize asphalt pavement compaction quality and efficiency. However, accurate assessment of compaction status remains challenging under real construction conditions. This paper reviewed recent progress and applications of smart sensors and machine learning (ML) to address existing limitations in IC. The principles and components of various advanced sensors deployed in IC systems were introduced, including SmartRock, fiber Bragg grating, and integrated circuit piezoelectric acceleration sensors. Case studies on utilizing these sensors for particle behavior monitoring, strain measurement, and impact data collection were reviewed. Meanwhile, common ML algorithms including regression, classification, clustering, and artificial neural networks were discussed. Practical examples of applying ML to estimate mechanical properties, evaluate overall compaction quality, and predict soil firmness through supervised and unsupervised models were examined. Results indicated smart sensors have enhanced compaction monitoring capabilities but require robustness improvements. ML provides a data-driven approach to complement traditional empirical methods but necessitates extensive field validation. Potential integration with digital construction technologies such as building information modeling and augmented reality was also explored. In conclusion, leveraging emerging sensing and artificial intelligence presents opportunities to optimize the IC process and address key challenges. However, cooperation across disciplines will be vital to test and refine technologies under real-world conditions. This study serves to advance understanding and highlight priority areas for future research toward the realization of IC's full potential. [ABSTRACT FROM AUTHOR]

Bulk density and porosity have great influence on the technical performance of an emulsified asphalt mixture, so in order to enhance the strength of the asphalt mixture, bulk density should be improved and porosity should be reduced. Considering the forming process of the emulsified asphalt mixture, the decrease in porosity can ensure the state of the mixture. In order to reduce the porosity of the emulsified asphalt mixture, an innovative forming process is proposed to improve the performance of the emulsified asphalt mixture, and its strength formation mechanism is explored in this paper. Three groups of emulsified asphalt mixtures (ARC-8 + SBR, SMA-5 + EVA, SMA-5 + SBR) were prepared by a conventional mixing process and novel mixing process. Marshall test of the emulsified asphalt mixture, CT scanning test of the emulsified asphalt mixture, workability test and analysis were manufactured and tested. The results show that, compared with conventional methods, the innovative forming method can increase the bulk density of the mixture and reduce the porosity, and thus improve its technical performance. The reason is that most of the water in the mixture of the innovative forming method sticks to the outer surface of the fine aggregate, and the water is more easily discharged. Secondly, the fine aggregate of the innovative forming method is directly mixed with the emulsion, and the volume is smaller. The emulsion wraps the fine aggregate in it due to the surface tension, which enhances the adhesion effect, thus improving the strength of the mixture. [ABSTRACT FROM AUTHOR]

To quantitatively evaluate the thermal stability and combustion characteristics of asphalt, the tests of constant temperature heating, oxygen index and cone calorimetry were used to obtain mass loss, oxygen index, heat release rate (HRR), total heat release rate (THR) and mass loss rate (MLR) of two asphalts of base asphalt and rubber asphalt. The results show that at the identical temperature, the mass loss, oxygen index, peaks of HRR, THR and MLR of rubber asphalt and the value of mass loss rate increased with the increasing of temperature are higher than those of base asphalt, while the thermal stability and combustion characteristics of rubber asphalt are inferior to base asphalt. Comparing three tests, the cone calorimetry test results are more reliable because of its more parameters, which is recommended to evaluate thermal stability and combustion characteristics of asphalt. [ABSTRACT FROM AUTHOR]

A polyurethane (PU) mixture was used to replace the wearing course of asphalt pavement because of its excellent mechanical properties, which necessitated the selection of suitable interlayer bonding materials between the polyurethane mixture wearing course and the asphalt mixture bottom course. Five types of tack coat materials were designed, including styrene-butadiene-rubber modified emulsified asphalt (SBREA), waterborne epoxy resin modified emulsified asphalt (WEREA), waterborne polyurethane modified emulsified asphalt (WPUEA), polyurethane, and polyurethane-stabilized fine sand (PUFS). Their cohesion performance under elevated temperature, high-temperature immersion, and freeze–thaw conditions was evaluated with tensile tests and shear tests. The results show that PUFS has the best adhesive properties, followed by PU, WPUEA, WEREA, and SBREA. WPUEA offers remarkable high-temperature stability, but is greatly affected by moisture. PU and PUFS exhibit outstanding freeze–thaw resistance, with the residual tensile strength and shear strength remaining above 75%. By incorporating fine sand into the composition, PUFS enhances interfacial friction compared with PU. However, this modification results in a slight reduction in its water stability. [ABSTRACT FROM AUTHOR]

A test model were designed in a constant-temperature laboratory to investigate the thermal conductivity and ice melting effect of pavements with embedded carbon fibre heating wires (CFHWs). The results showed that under simulated winter environmental conditions, the surface temperature of the test piece exceeded the freezing point after heating for 122 min in temperature rise test.Meanwhile,under the same conditions, the 10 mm thick ice layer on the test piece surface in the ice melting test began to melt after heating for 330 min, and all the ice layer had melted after 6 h , indicating that the pavement with embedded CFHWs has good ice melting performance. Moreover, a finite element model for transient heat transfer analysis was established. Combined with the experiments, the relevant parameters of the numerical model were corrected to obtain a more accurate numerical model. The calculations prove that the arrangement spacing significantly impacts the efficiency of the sidewalk for snow melting; the ambient temperature variation will slightly reduce the average rate of temperature rise on the surface of the model; and the ice melting effect of the CFHW with back shape is better than the U shape and the broken line shape under the same circumstances. [ABSTRACT FROM AUTHOR]

In order to meet the requirements of compatibility and timeliness of repair materials for asphalt pavement, a rapid-hardening magnesia-based cement emulsified asphalt mortar (MCAM) is prepared. The results show that high temperature or high-temperature water bath treatment reduces the stability of MCAM, and MCAM prepared from emulsified asphalt with high softening point and low water content has better high-temperature stability. Increasing the asphalt-cement (A/C) ratio decreases the dynamic stability and stiffness modulus of the MCAM-repaired asphalt mixture, but increases its failure strain, which is determined by the material properties of the asphalt and cement phases. The splitting tensile strength of MCAM-asphalt mixture specimens are all above 0.8 MPa, and the strength ratio before and after freezing and thawing is above 90%, which is significantly higher than that of traditional asphalt-based, epoxy-based and polyurethane-based pavement repair materials. When MCAM is used to repair dried surface of asphalt mixtures, its pull-out bonded strength is significantly higher than that after wet and aged treatments. In addition, the microstructure of MCAM also shows that the asphalt phase and the cement phase are mixed together, and the microstructure becomes loose as the A/C ratio increases. [ABSTRACT FROM AUTHOR]

The cross-tensioned concrete pavement (CTCP) has good bearing capacity, anti-crack ability and convenient construction characteristics due to the cross-tenioned prestressed strands placed inside the concrete. In order to study the mechanical response of pavement in construction process, an assembled monolithic structure for CTCP has been proposed and its mechanical response was analyzed through full-scale experiments and finite element model. The results of full-scale experiments show that the longitudinal and transverse compressive strain of concrete respectively exceeds 40μϵ and 20μϵ in the area of laying cross-tensioned prestressed strands with increase of the number of cross-tensioned strands. The end of CTCP is one of the weak areas, which may produce certainly transverse tensile stress. The results of finite element model show that the transverse tensile stress in ending region is mainly affected by the angle of cross-tensioned prestressed strands and its ratio. There is transverse tensile stress at the end of the pavement when the angle of cross-tensioned prestressed strands is small and its ratio is large, which can be offset by arranging transverse prestressed strands. Furthermore, an empirical formula to calculate transverse prestressed strands ratio at the end of pavement is given based on the results of finite element simulation. [ABSTRACT FROM AUTHOR]

In order to meet the requirements of compatibility and timeliness of repair materials for asphalt pavement, a rapid-hardening magnesia-based cement emulsified asphalt mortar (MCAM) is prepared. The results show that high temperature or high-temperature water bath treatment reduces the stability of MCAM, and MCAM prepared from emulsified asphalt with high softening point and low water content has better high-temperature stability. Increasing the asphalt-cement (A/C) ratio decreases the dynamic stability and stiffness modulus of the MCAM-repaired asphalt mixture, but increases its failure strain, which is determined by the material properties of the asphalt and cement phases. The splitting tensile strength of MCAM-asphalt mixture specimens are all above 0.8 MPa, and the strength ratio before and after freezing and thawing is above 90%, which is significantly higher than that of traditional asphalt-based, epoxy-based and polyurethane-based pavement repair materials. When MCAM is used to repair dried surface of asphalt mixtures, its pull-out bonded strength is significantly higher than that after wet and aged treatments. In addition, the microstructure of MCAM also shows that the asphalt phase and the cement phase are mixed together, and the microstructure becomes loose as the A/C ratio increases. [ABSTRACT FROM AUTHOR]

The cross-tensioned concrete pavement (CTCP) has good bearing capacity, anti-crack ability and convenient construction characteristics due to the cross-tenioned prestressed strands placed inside the concrete. In order to study the mechanical response of pavement in construction process, an assembled monolithic structure for CTCP has been proposed and its mechanical response was analyzed through full-scale experiments and finite element model. The results of full-scale experiments show that the longitudinal and transverse compressive strain of concrete respectively exceeds 40μϵ and 20μϵ in the area of laying cross-tensioned prestressed strands with increase of the number of cross-tensioned strands. The end of CTCP is one of the weak areas, which may produce certainly transverse tensile stress. The results of finite element model show that the transverse tensile stress in ending region is mainly affected by the angle of cross-tensioned prestressed strands and its ratio. There is transverse tensile stress at the end of the pavement when the angle of cross-tensioned prestressed strands is small and its ratio is large, which can be offset by arranging transverse prestressed strands. Furthermore, an empirical formula to calculate transverse prestressed strands ratio at the end of pavement is given based on the results of finite element simulation. [ABSTRACT FROM AUTHOR]

This study investigated the feasibility of applying a polyurethane-bonded mixture (PUM) on the pavement overlay for construction or maintenance. Styrene butadiene styrene (SBS) asphalt and epoxy asphalt, the two most common and widely adopted mix designs for highway steel bridge pavement, were selected for a comparative study. First, the performance evaluations and failure analysis of the asphalt mixture and PUM were investigated comprehensively, in terms of low-temperature property, rutting, fatigue, and freeze-thaw resistance. The results showed that the dynamic stability of PUM was over 30,000 cycles/mm and fatigue life was over one million cycles under 800 με. The tensile strength ratio (TSR) value was higher than 90%, which also indicated an excellent freeze-thaw resistance. Then, bond and shear strengths between the steel plate and the mixture were evaluated for the interlayer of the steel bridge pavement structure. X-ray CT scan analysis was adopted to visualize the internal structure of various mixtures, and the average void diameter of PUM was 0.569 mm. Finally, a statistical analysis was conducted for Kendall consistency and Grey correlation. This research established that PUM is a cost-effective and long-lasting solution for pavement overlay on highway steel-bridge. [ABSTRACT FROM AUTHOR]

This study assessed the fundamental physical properties and chemical composition of three specific waste engine oil residue (WEORs) asphalt regenerants. Through dynamic shear rheometer and rolling thin-film oven tests, the performance of aged asphalt was evaluated using three key indicators. Thin-layer chromatography investigations probed the WEOR-induced changes in the aging asphalt components, leading to the creation of two novel asphalt regenerants, WEOR-H and WEOR-G. WEOR-G was developed from WEOR-1, liquid rubber, ultraviolet absorber, light shielding agent, and antioxidant, while WEOR-H was formulated from WEOR-2, aromatic oil, and liquid rubber. The study employed differential scanning calorimetry and conventional laboratory tests to analyze the road performance attributes of Ingevity J type regenerant (J), WEOR-G, and WEOR-H. The results indicated that WEORs increase the saturate and aromatic content in asphalt and partially replenish the missing lightweight components of aged asphalt, moderately improving the three key indicators, though the regenerative effect is restricted. Achieving a full restoration of component proportions within aged asphalt to their initial levels proved unattainable, and direct application of any of the three WEORs as asphalt regenerants is impractical. WEOR-H and WEOR-G demonstrated potential in enhancing aged asphalt binder road performance, outpacing three other WEORs. At a 14% dosage, WEOR-G and WEOR-H could increase the 10 °C ductility to 23.5 and 21.4 cm, respectively, effectively counterbalancing the insufficient ability of WEOR-1 and WEOR-2 to restore the low-temperature performance of aged asphalt. Among the regenerants, WEOR-G, possessing superior regenerative effects, the lowest glass transition temperature, and optimal low-temperature deformation resistance, emerged as the most efficacious. This inquiry furnishes vital data support for future applications of WEOR-G asphalt regenerant. [ABSTRACT FROM AUTHOR]

The southern tropical coastal areas of China are high-temperature and high-humidity salt environments, which hinder the durability and service life of ordinary asphalt pavement. To enhance the durability of asphalt pavement in these areas, modified bagasse fiber combined with nano-TiO2 was used to improve the corrosion resistance of asphalt pavement in high-temperature and high-humidity salt environments. The micro-morphology, high-temperature oil absorption, high-temperature heat resistance, and hygroscopicity of bagasse fiber modified using three silane coupling agents combined with NaOH were compared, and the best silane coupling agent/NaOH modification scheme for bagasse fiber was found. Based on conventional physical tests (penetration, softening point, ductility), rheological property tests (rotational viscosity, dynamic shear rheological test, multi-stress creep recovery test, linear amplitude scanning test), and a four-point bending fatigue test of the asphalt mixture, the properties of modified bagasse fiber asphalt binder and mixture after cyclic dry–wet erosion under pure water and salt solution (NaCl, Na2SO4) were determined, and the effects of the erosion environment and fiber ratio on the basic physical and rheological properties of the asphalt were clarified. Compared with the silane coupling agents KH550 and KH590, the bagasse fiber modified with KH570/NaOH had a better high-temperature oil absorption capacity, heat stability capacity, and matrix asphalt compatibility. The worst erosion environment was Na2SO4, but the increase in test temperature and fiber content weakened the sensitivity of the asphalt binder performance in different erosion environments. The erosion capacity order was as follows: Na2SO4 > NaCl > pure water. In the worst erosion environment, 0.5% modified bagasse fiber/Nano-TiO2 asphalt binder (Bn−570−0.5) had the best corrosion resistance in a high-temperature and high-humidity salt environment. The penetration, softening point, creep recovery rate R3.2, non-recoverable creep compliance Jnr3.2, and fatigue life after long-term aging (with 5% strain) of Bn-570-0.5 were, respectively, increased by −16.9%, 37.5%, 37.95%, −27.86%, and 38.30% compared with unblended base asphalt binder (B). In addition, the four-point flexural fatigue life of Bn-570-0.5 was 169.2% higher than that of the unblended base mixture. [ABSTRACT FROM AUTHOR]

Porous asphalt concrete (PAC) is an open-graded asphalt concrete with a high air void, which functions as permeable pavement with high surface frictional resistance. PAC typically requires a high amount of coarse aggregate to provide the required porous structure. An expensive high-quality polymer-modified asphalt (PMA) is commonly required to prevent draindown issues and to improve the performance of PAC. Bottom ash (BA), a high-porosity byproduct from coal-fired power plants, is used as a greener product to improve the quality of traditional asphalt cement penetration grade 60/70 (AC 60/70) for producing low-cost PAC in this research. The effect of the BA replacement ratio (0%, 10%, 15%, 20%, and 25% by total weight of fine aggregate) on the draindown, loss of particle, Marshall properties, indirect tensile strength (ITS), indirect tensile resilient modulus (IT Mr), indirect tensile fatigue life (ITFL), permanent deformation (PD), rut depth, and skid resistance of BA-AC60/70-PAC were measured and compared with PMA-PAC. The draindown and particle loss values of BA-AC60/70-PAC were found to decrease with an increase in the BA replacement ratio. The BA replacement improved the Marshall properties, strength index, ITS, IT Mr , ITFL, PD, rut depth, and skid resistance of PAC up to the highest value at the optimum BA replacement ratio of 20%. The improved ITS is associated with the improved IT Mr in a linear relationship for all BA replacement ratios. The change in ITFL was found to be linearly related to IT Mr at a specific stress level. At the same design criteria, the 20% BA replacement ratio yields the reduction of total construction cost of BA-AC60/70-PAC surface course by 33% benchmarked to the conventional PMA-PAC surface course. [ABSTRACT FROM AUTHOR]

To investigate the effect of freeze-thaw cycles on the moisture susceptibility of asphalt mixtures, the changes of adhesion work and exfoliated work between asphalt aggregate interface under different freeze-thaw cycles were analyzed based on the surface free energy theory, and the moisture stability of asphalt mixture was evaluated. The effects of water saturation and freeze-thaw on the water stability of asphalt mixture were further explored by splitting test and Logistic model. The results show that with the increasing of freeze-thaw times, the surface energy and cohesive work of asphalt are decreased with decreased adhesion work between asphalt and aggregate, while the exfoliated work is increased with decreased moisture susceptibility of asphalt mixture. The void fraction of asphalt mixture is increased with the increasing of freeze-thaw times, while the splitting strength is decreased. The greater the saturation of asphalt mixture during freeze-thaw is, the greater the damage degree and damage rate are. When the saturation of asphalt mixture is greater than 50.00%, the effect of freeze-thaw on the performance of asphalt mixture becomes more obvious. Therefore, it is recommended that the freeze-thaw splitting test of asphalt mixture should be carried out under the condition of saturation higher than 50.00%. [ABSTRACT FROM AUTHOR]

The percentage of voids in mineral aggregates (VMA) is an important consideration in the design of asphalt mixtures. Accurate and precise prediction of VMA is critical in pavement engineering. This study reviewed and evaluated current VMA prediction methods. From the perspective of treating aggregate gradation, the methods were classified into four categories: the overall gradation prediction method (OGPM), gradual gradation prediction method (GGPM), indirect parameter prediction method (IPPM), and theoretical derivation method (TDM). Fifty-four groups of published test data from previous studies were used to evaluate the prediction results of the models, and the precision and accuracy of the prediction results were compared. From the perspective of the completeness of the modeling parameters and the theoretical foundation, the reasons for the differences in prediction results with different methods were analyzed. It was concluded that the TMD has a solid theoretical basis, especially the Yu method in TMD exhibited the best prediction precision and accuracy. Some modifications to the current methods were suggested, such as incorporating other factors affecting VMA and optimizing the particle shape indicators. [ABSTRACT FROM AUTHOR]

Pavement compaction is an important index to evaluate the construction quality of rubber asphalt pavement. The spreading temperature segregation of mixture will affect the pavement compaction degree. To study the relationship between temperature segregation of crumb rubber-modified asphalt (CRA) mixture and pavement compactness, the 40-mesh crumb rubber powder was used to prepare CRA, and the Superpave design method was adopted to design the CRA mixture in the laboratory. Based on the infrared thermal imaging technology, the segregation of CRA mixture was quickly detected, and the pavement compactness was measured by coring at the temperature detection point. On this basis, a numerical analysis model of temperature–pavement compactness was established. The results show that the temperature data detected by the infrared thermal imager are reliable after comparison with the measured data of the thermometer. The temperature segregation of the mixture in direct contact with the atmosphere and the car body during transportation is serious. When the temperature segregation difference of CRA mixture is increased by 5 °C, the bulk specific gravity difference of coring specimen increases by 0.012. According to the field measured data, the relationship between paving temperature and compactness of rubber asphalt mixture is a quadratic function. [ABSTRACT FROM AUTHOR]

Cold-recycling technology with foamed asphalt is used widely because it has the incomparable advantages of environmental protection and resource conservation. In this study, cold-recycled mixtures with foamed asphalt were prepared with different gradation types, mixing water contents, and curing times to study the distribution characteristics of residual moisture. An optimum foaming water content of 2.5% and foaming temperature of 165°C were determined for producing the foamed asphalt that was used for the cold-recycled asphalt mixtures. Hyperspectral imaging tests and spectral processing technology were used to obtain the image information and spectral information of residual moisture from 44 specimens; the moisture content of all specimens ranged from 0.25% to 4.70%. Pseudocolor-coding technology was utilized to realize visualization of moisture distribution. In addition, the residual moisture content prediction model was established based on the partial least-squares regression (PLSR) model. Correlations of the residual moisture distribution characteristics and moisture damage resistance evaluation indicators were developed. The residual moisture distribution characteristics and moisture damage resistance are affected significantly by aggregate gradations, mixed water content, and curing time. After 3 days of curing, the strength of the recycled mixture tends to be stable, and the moisture damage resistance can reach the specification requirements, and is suitable for open traffic. It was confirmed that there is a certain correlation between the internal residual moisture content value distribution range and the moisture damage resistance of the cold-recycled mixtures with foamed asphalt. This study could contribute to a better application of cold-recycled asphalt pavement for environmental protection and carbon stabilization. [ABSTRACT FROM AUTHOR]

This work addressed the issues of poor bonding and low forming strength of emulsified type cold-mix asphalt (CMA). The aim of this study was to improve the pothole repair effect. Accordingly, waterborne epoxy resin (WER) was adopted as an emulsifier, and samples of WER-emulsified CMA reinforced with polypropylene fiber were prepared in the laboratory. First, the mixing ratio of WER and curing agent was optimized through three indexes and storage stability tests. Second, fluorescence microscopy, dynamic shear rheology (DSR), and bending beam rheometer (BBR) tests were conducted to determine the ratio between WER and curing agent, called WERC, in emulsified asphalt binder. After that, pavement performance and bonding characteristics of asphalt mixes produced by this binder were evaluated to analyze the feasibility of using WER-emulsified type CMA in pothole repair and to determine the optimal WERC content. The results show that the best mixing ratio of E-44 and EH-05 is 1.5:1, and WER-emulsified type CMA mixes have shown improved strength, high-temperature rutting resistance, water stability, low-temperature crack resistance, and interfacial bonding characteristics. With the increase of WERC, the performance influence range gradually slows down. Considering overall performance improvement and cost, best WERC content is finally determined as 6.5%. The newly developed emulsified type CMA can be applied to the rapid repair of pavement potholes. [ABSTRACT FROM AUTHOR]

This paper focused on ice processing and snow melting on urban pavement during the winter time in South China under the emergent situation. A kind of electrothermal cushion with carbon fber was developed to improve resistance to skidding of pavement in winter and help melt ices and snows on the surface of pavement to ensure driving safety. This special cushion is composed of multilayer materials and structures. Laboratory tests for the cushion were conducted to analyze its electrothermal performance, heating uniformity, efect of ice melting, skidding resistance and frictions. At the same time, the durability of the ice melting cushion was evaluated. The results indicate that the developed anti-skidding electrothermal ice melting cushion with carbon fber is stable in heating ability, high in heating speed, and the surface and bottom temperature of the ice melting mat during operation is not more than 30 ℃ without burning pavements and wheel tires, and the melting rate can reach 78.7% for one hour. The cushion can achieve excellent skid resistance and interlayer friction performance. The cushion can completely meet the requirements such as repeated rolling compaction under vehicle load, abrasion, bursting, etc., and have good durability. Therefore, the cushion is recommended to directly be placed on the pavement surface without interrupting trafcs to improve the anti-skidding performance and short-term ice and snow melting in winter. The cushion has lower heating and deicing cost and has a better deicing efect and better economic benefts. Moreover, the cushion only needs to be used in winter, which extends its service life and can be reused without adverse impact on road performance. [ABSTRACT FROM AUTHOR]

To establish a new gene database and asphalt mixture evaluation method, coarse aggregate contact characteristics from the meso perspective serve as a reference for the improvement of fine design and asphalt mixture performance. In this study, a rapid analysis and evaluation software for coarse aggregate contact software was developed. An optimization calculation method for voids in coarse aggregate of asphalt mixture was proposed based on digital image processing techniques. In addition, the meso characteristic gene of coarse aggregate contact for eight different asphalt mixtures was investigated, and the relationship between coarse aggregate contact mesogenetic parameters and the corresponding macrorutting resistance was established. The results indicate that number of contact points is not appropriate as the mesoparameter for evaluating the skeleton of the asphalt mixture; average coordination number, skeleton ratio, and "free" coarse aggregate content can be used to evaluate the mesostructure of the asphalt mixture. Skeleton ratio is the most sensitive mesogenetic parameter affecting rut depth, which can be used as the main control parameter for fine design of asphalt mixture. The limit standards of the skeleton ratio and "free" coarse aggregate content values are 41.32% and 82.89%, respectively, and the range of average coordination numbers is 0.5–1.72. However, the mesodesign parameters cannot reach the standard theoretical value due to the inhomogeneous granular material characteristics of the asphalt mixture. In the asphalt mixture design process, average coordination number is ≥1.50 , skeleton ratio is ≥23.48% , and "free" coarse aggregate content is ≤24.94% ; these values can be used as the mesoparameter standard for the fine design of skeleton asphalt mixtures. [ABSTRACT FROM AUTHOR]

The circular use of resources (i.e., reuse and recycling of materials) aiming for zero waste is also gaining increasing attention in pavement engineering. In this regard, the possible use of waste plastics in asphalt materials is of strategic importance since a considerable amount of plastic waste from construction and demolition waste and municipal solid waste is generated every year. Given this background, this experimental study aimed to investigate the feasibility of recycling waste polyethylene (PE) into asphalt mixtures. For this purpose, the dry addition of plastic shreds was evaluated to overcome the drawbacks observed in a previous interlaboratory research on PE-modified bituminous binder (i.e., instability/inhomogeneity of blend as well as the need for PE grinding). A comparative laboratory study was carried out on dense graded asphalt mixtures containing different amounts of waste plastics (i.e., 0%, 0.25%, and 1.5% by weight of the mixture). The selected asphalt mixes were investigated in terms of workability, linear visco-elastic characteristics, stiffness, strength, resistance to permanent deformation, and moisture sensitivity. Overall, the experimental findings show that the mixes prepared with the dry addition of plastic wastes were able to guarantee almost the same workability and moisture resistance as the reference material while leading to enhanced performance in terms of stiffness and permanent deformation resistance, with better responses for the higher investigated PE dosage. [ABSTRACT FROM AUTHOR]

To investigate the influence of coarse aggregate morphologies on the performance of asphalt mixture, three discrete element models with different coarse aggregate morphologies were proposed in this study. Skeleton contact characteristics, skeleton contact stress, coarse aggregate movement characteristics, interfacial stress distribution, and micro-crack development characteristics with different coarse aggregate morphologies were compared and analyzed. The results indicate that there is often 40 %–50 % of compressive stress at the coarse aggregate contact point, 10 %–20 % of tensile stress, and 30 %–40 % of tensile and compressive mixed stress. Aggregate morphology has a more significant impact on the contact area than it does on the type of stress at the contact point or the number of main skeleton contact points. Contact stress, coarse aggregate movement, and crack development in the asphalt mixture are all greatly influenced by coarse aggregate morphologies. More needle-flake aggregates result in less contact stress, more coarse aggregate movement displacement, and faster asphalt mixture cracking. Shear stress makes up the majority of the micro-cracks that are caused by induced stress in asphalt mixture; tensile stress micro-cracks are quite minor, making up around 10 % of the total number of micro-cracks. In order to increase the aggregate–asphalt interface qualities and the crack resistance of the asphalt mixture, it is important to avoid using too much needle-flake coarse aggregate. The findings can provide guidance for the choice of raw materials and mix ratios for asphalt pavement design, improving the asphalt mixture's meso-mechanics and macroscopic road performance. • Three discrete element models with different coarse aggregate morphologies were developed. • The influence of coarse aggregate morphologies on the skeleton contact characteristics was investigated. • The development characteristics of micro-cracks with different coarse aggregate morphologies were investigated. • Indices for improving the properties of coarse aggregates were proposed. [ABSTRACT FROM AUTHOR]

The fatigue resistance of an asphalt mixture is crucial to the pavement's durability and serviceability of pavement. The pavement structure is in a three-dimensional (3D) stress state. However, the conventional fatigue-resistance design index mostly considers a one-dimensional stress state, which is different from the field conditions. In this paper, the unconfined compression test (UCT), direct tension test (DTT), and splitting test (SPT) were selected to conduct the strength and fatigue tests. Based on the Ayyagari Vural yield criterion, the strength damage surface under various loading rates was established. Furthermore, a normalized fatigue equation was developed in a 3D stress state by determining the fatigue-damaged path based on the yield criterion. Finally, the fatigue-resistance models for the structural design were proposed by combining the strength models (including the octahedral shear stress model and the Ayyagari Vural model) and the normalized fatigue equation. The results indicate that the strength damage surface model is in an elliptic form, and the surface is abducent as the loading rates increase, and the Ayyagari Vural yield criterion can describe the fatigue failure process. Both fatigue-resistance design methods for pavement resistance take the interaction among three principal stresses into consideration and comply with the failure characteristics of actual pavement structures; the equivalent stress as a design index is more feasible in its actual application. This study could provide a reference for the fatigue-resistance design of asphalt mixture layers in a complex stress state and improve the reliability in the pavement structure. [ABSTRACT FROM AUTHOR]

In order to overcome the significant settlement difference between the road and the bridge and to essentially solve the bridge head jumping problem, a five-layer system three-dimensional finite element model was established by ABAQUS through the stiffness coordination analysis method, and the change law of the road and bridge transition section surface pavement performance under the action of single and multi-factor was analyzed based on fracture mechanics, and then a multi-factor fatigue life prediction model was established for the structural combination and mechanical control index. The results show that the stress intensity factor KⅡ decreases with the decrease of the stiffness difference between the surface layer and the subgrade, the surface layer and the lap layer, and the surface layer and the soil base. The fatigue life of surface layer decreases with the increase of surface layer modulus and axle load, and increases with the increase of surface layer thickness, base layer thickness, base layer modulus, lap layer thickness, lap layer modulus, soil base modulus and vehicle speed. the order of sensitivity to fatigue life of pavement is surface layer thickness > vehicle speed > soil base modulus > axle load > lap layer thickness > base layer thickness > surface layer modulus > base layer modulus > lap plate modulus. The research results can provide the corresponding theoretical support for the rational design of asphalt pavement at the bridge head lap in China, and also provide a new method for the fatigue life research in China. [ABSTRACT FROM AUTHOR]

Pavement-based piezoelectric power-generation technology converts mechanical energy generated by traffic loads into electricity by embedding piezoelectric transducers in the pavement. However, existing piezoelectric transducer structures are mostly the direct-impact type and the piezoelectric ceramic materials can be easily damaged. To reduce the risk of damage, a box-type bending piezoelectric energy transducer was designed and prepared in this study. The transducer is composed of 27 fixed piezoelectric sheets connected at both ends in parallel. The external casing uses a box-type structure with upper, middle and lower components. Under typical traffic load conditions, an excitation frequency of 10 Hz and displacement of 2 mm, the maximum output voltage was 30.17 V, the maximum output current was 10.01 mA and the maximum output power was 303.4 mW under load resistance of 3 kΩ. The output power of the transducer increases with loading frequency and displacement. Finally, the output power of the proposed transducer is much higher than that of existing transducers. This new piezoelectric transducer has good prospects for use in energy-generating pavement engineering applications. [ABSTRACT FROM AUTHOR]

The objective of the study is to investigate the effect of castor seeds oil-based bio-oil on the thermal-oxidative aging characteristics and mechanisms of asphalt. Castor seeds oil-based bio-asphalt (COBA) was prepared by mixing bio-oil with petroleum asphalt. Short-term and long-term aging simulations of COBA were performed by the rolling thin film oven test (RTFOT). Firstly, the dynamic shear rheological (DSR) test, bending beam rheometer (BBR) test, and basic physical property test were conducted to evaluate the macroscopic properties of COBA before and after aging. Secondly, the changes of oxygen content in COBA and the number of oxygen-containing functional groups caused by aging were quantitatively. Finally, the two-dimensional morphology of COBA was observed, and the size of "bee-like structure" and roughness were analyzed. The results demonstrated that the low-temperature performance degradation of COBA mainly occurs during the short-term aging period, while the high-temperature performance degradation mainly occurs during the long-term aging period. Microscopic analysis shows that the addition of bio-oil renders a lower oxidation rate of COBA than matrix asphalt in the long-term thermal oxidation period. However, the growth of O elements and Carbonyl functional group index (I C O) and the decrease of H/C ratio in COBA are more obvious in short-term thermal oxidation period, exhibiting a favorable correlation between macro and micro properties. Moreover, C O functional group is mainly contributed by the added bio-oil. The COBA aging is related to a large amount of C O and root-mean-square roughness (Rq) changes in bio-oil, which can be better used to characterize the aging of COBA. • The low- and high-temperature performance of COBA decays quickly during the short- and long-term aging period, respectively; • The added bio-oil renders a lower oxidation rate of COBA than matrix asphalt in the long-term thermal oxidation period; • Functional group C O is mainly contributed by the added bio-oil, and the S O originates from the matrix asphalt; • Aging of COBA is related to a large amount of C O and Rq changes in bio-oil; • Functional groups of C O, S O are better used to characterize the aging of COBA than the content of O element. [ABSTRACT FROM AUTHOR]

A lightweight PCSNet-based segmentation model is developed to efficiently overcome insufficient performance in feature extraction and boundary loss information resulting from sampling operations. The proposed approach incorporates two key components: an enhanced shuffle unit and an improved inverted residual architecture to effectively reduce model parameters and enhance inference time. Additionally, introducing the generalized Dice loss (GDL) aims to address the prediction accuracy issue caused by category imbalance. Finally, this study employs gradient-based class activation mapping to visualize and interpret the learned features. To enhance model interpretability, experiments were conducted on three publicly available datasets and compared with existing popular segmentation models. The findings demonstrate that including the GDL in the lightweight PCSNet model leads to a significant improvement in prediction performance, with the highest mIoU reaching 78.93%. Additionally, the visualization of class activation mapping (CAM) further enhances PCSNet interpretability in terms of feature extraction. • A customizable and lightweight segmentation model improves inference time. • The improved inverted residual of the encoder reduces the model's parameters. • The enhanced shuffle unit structure improves the model's prediction accuracy. • The GDL loss function is introduced to address the category imbalance issue. • The interpretability of CNNs is explained from the perspective of feature extraction. [ABSTRACT FROM AUTHOR]

Following the extensive research on piezoelectric technology and the increasing popularity of intelligent transportation during the past few years, the harvesting of pavement vibration energy has attracted increased research attention. At present, most innovations in the direction of the road piezoelectric energy are focused on the materials and structures of the transducers. However, few transducers meet the road requirements. Therefore, in this study, a hemispherical piezoelectric transducer was developed for road applications. We also analyzed the effects of different sizes and structures of transducers on energy harvesting efficiency based on laboratory tests, and the outcomes were compared with those from plane transducers. Under the excitation frequency of 10 Hz and the load of 0.7 MPa, the maximum output power of the planar transducer was 0.422 mW, while the power of the hemispherical transducer at the same load was 0.765 mW. Based on the dynamic load test, the ultimate load of the hemispheric transducer was 1900 N, which was 2.66 times that under standard axial load. Subsequently, a dynamic fatigue test was conducted for 24 h at the excitation conditions of 10 Hz and 0.7 MPa, wherein the voltage attenuation of the plane transducer exceeded 60%, while that of the hemispheric transducer was <20%. The experimental results show that the structure had a stable performance and good durability, and its strength and acquisition efficiency met the requirements of road transducers. [ABSTRACT FROM AUTHOR]

In many application areas such as pavement engineering, the phenomena are complex, and as a result, we do not have first-principle models describing the corresponding dependencies. Luckily, in many such areas, there is a lot of empirical data and, based on this data, many useful empirical dependencies have been found. The problem is that since many of these dependencies do not have a theoretical explanation, practitioners are often hesitant to use them: there have been many cases when an empirical formula stops being valid when circumstances change. To make the corresponding empirical formulas more reliable, it is therefore desirable to look for theoretical foundations of these formulas. In this paper, we show that many of such dependencies can be naturally explained by using invariances. We illustrate this approach on the example of pavement engineering, but the approach is very general, and can be applied to other systems as well. [ABSTRACT FROM AUTHOR]

Electric arc furnace (EAF) aggregates, by-products of the homonymous steelmaking process, represent an ideal solution for asphalt mixtures, above all for wearing courses where skid resistance and durability are essential functional requirements. Their use, which is subordinate to the compliance of chemical specifications, finds some practical interest limits mainly related to transportation (extremely high bulk specific gravity) and placement (unsatisfactory compaction) operations. Thus, the aim of this experimental study was to determine an ideal artificial to natural aggregates replacement rate, also identifying the most suitable particle size range, for dense-graded asphalt wearing courses. The results highlighted how the best balance between compaction and mechanical performances was registered by a mix which was formulated considering a partial replacement of 54% (v/v%), distributed only in the coarsest fraction. The introduction of limestone as "excipient" in the coarse-fine and finer size ranges reduces the weight of the mixture, guaranteeing at the same time an optimum compaction degree, high levels of stiffness in the viscous-elastic region and Marshall stability and extended fatigue life. [ABSTRACT FROM AUTHOR]

The reliability and cost-effectiveness of pavement maintenance and rehabilitation (M&R) decisions are highly dependent on the quality of pavement performance data which are regularly collected and stored in the Pavement Management System (PMS) of a state highway agency. Frequently, pavement performance evaluation relies on the precise and accurate measurements of the surface conditions of pavements. This study aims to statistically check the accuracy and precision of using a state of practice automated technology in place of the manual or semi-automated (semi-manual) rating method to collect pavement cracking data. In the study, the classification evaluation indicators were first employed to quantitively evaluate the two kinds of errors which may occur during the automated crack detection process. Second, the systemic errors of the automated method were quantitively evaluated by a t-test to check the accuracy of the automated method, and the variation pattern of the systemic errors was verified with the Pearson correlation test. Finally, the random errors of the automated method were quantitatively evaluated with the Levene's test to check the precision of the automated method. The study results indicated that the state of practice automated survey method is still not yet ready to provide reliable pavement cracking measurement data. It seemed the automated method in the study could not accurately detect pavement cracking features from the background and an under-estimation tendency of cracking measurement was observed. The automated data also showed varying measurement performance when surveying different types of pavement cracking. While the collected transverse cracking data were relatively precise, obvious measurement errors were present in longitudinal cracking data. In addition, the systemic errors in the automated data were highly correlated with the surveyed pavement distress condition. A greater systemic error was frequently associated with a more deteriorated pavement condition. [ABSTRACT FROM AUTHOR]

[Display omitted] • Steel slag can be used in asphalt pavement for its superior material property as coarse aggregates. • Steel slag aggregates have a rougher surface, more contact points, and more durable wear resistance. • A method for evaluating the abrasion resistance performance of steel slag based on micro-morphology is proposed. • Sa, Spd, and Spc are reliable indicators for investigating the long-term skid resistance of asphalt mixtures. Steel slag can be utilized in the wearing course of highway asphalt pavement. However, further research is needed to explore the impact of steel slag on the wear resistance of asphalt pavement. This study aimed to evaluate the wear resistance of two steel slag samples and compare them with three stone aggregates based on morphological characteristics. The Los Angeles abrasion test was conducted at different revolution levels, and the micro-morphology characteristics of the aggregates were analyzed through image analysis using six morphology parameters. The results showed that the steel slag samples had the lowest Los Angeles abrasion rates, indicating their superior hardness and wear resistance compared to limestone and granite aggregates. The steel slag aggregates also exhibited higher values in morphological indices of arithmetic mean height Sa , peak apex density Spd , and arithmetic mean curvature of peak apex Spc , indicating a rougher surface, more contact points and more durable wear resistance. Fluctuations were observed on variation curves of the maximum height Sz , surface skewness Ssk, and surface sharpness Sku of the steel slag during the abrasion process, suggesting the presence of numerous pits and spikes that contribute to the skid resistance of the steel slag asphalt mixture. The arithmetic mean height Sa, peak density Spd, and arithmetic mean curvature of peak apex Spc showed a consistent decrease over the number of revolutions, making them reliable indices for future research on the wear resistance of steel slag asphalt mixtures. Overall, this study provides a basis for further research on investigation the correlation between the morphology changes of steel slag aggregates and the anti-skid performance of pavement wearing courses. [ABSTRACT FROM AUTHOR]

• The utilization of RCA as a granular material has proven to be a suitable solution to control waste management and protect natural resources. • RCA has a more porous and rougher structure than crushed limestone aggregate. • RCA particles contain cement mortar phase, a more hollow and heterogeneous structure than crushed limestone aggregate. • Because of the shape and surface texture properties of the RCA, the M R of the RCA mixtures was higher than that of the LA mixtures. Construction and demolition wastes (CDW) have become uncontrollable due to population expansion, fast urbanization, ongoing technological advancements, and changing building materials throughout time, as well as the storage of these wastes and the environmental degradation they create. In addition, recently, the depletion of natural resources and rising expense of waste disposal have increased the importance of recycling and reuse of waste. Recycling and reuse of CDW can reduce the rate of depletion of natural aggregate resources, landfill area and carbon footprint. However, the lack of knowledge about parent concrete's qualities, such as compressive strength, is one of the most significant barriers to using these waste materials. In addition, further research is needed on the use of high-strength building waste that was devastated by earthquakes and floods as aggregates. The study aimed to investigate the quality of waste concrete and assess the usability of mixtures prepared using recycled aggregates obtained from waste concrete with a predetermined strength of 35–40 MPa in combination with crushed limestone aggregate in granular road base and sub-base layers. The engineering performance of RCA will be evaluated, along with a comparison to natural aggregate, and its compliance with the limit values given in the Turkey Highways Technical Specifications (THTS) will be examined. 5 different mixes were created by replacing RCA with LA at 0%, 25%, 50%, 50%, 75%, and 100%. The strength, durability and hydraulic properties of the prepared mixtures were investigated. It was concluded that the use of RCA had no negative effects on the mixture's properties, with the exception of permeability, and even outperformed natural aggregate in terms of soaked and unsoaked CBR, CBR strength after a freeze–thaw cycle, and modulus of elasticity. Additionally, it was established that RCA satisfies the standards set in the THTS for the materials to be used in granular road base and sub-base layers. [ABSTRACT FROM AUTHOR]

The goal of this paper is to reveal the influence of temperatures on the triaxial strength of asphalt mixtures. The triaxial compression and triaxial tensile tests, as well as plane tensile and compression/axial tensile tests, which were developed by the self-developed triaxial test equipment to carry out the complex stress state under different temperatures (5°C, 10°C, 15°C, 20°C, and 25°C), were performed on the asphalt mixture. The ultimate failure strength of the material shows that the temperature and stress state significantly affect the triaxial strength characteristics of the asphalt mixture, and the three-dimensional strength decreases by the increase in temperature. Under the triaxial compression and triaxial tensile stress state, the resistance of the octahedral shear stress increases with the hydrostatic stress. A three-dimensional strength calculation model is established based on the influence of temperature and characterization by the tensile meridian, compression meridian, and failure strength envelope. It reveals the change of failure strength envelope with increasing temperatures and decreasing hydrostatic stress under complex stress state. It provides experimental and theoretical references to the design of asphalt pavement structure of different temperature conditions according to the three-dimensional stress state. [ABSTRACT FROM AUTHOR]

• Majority of solid waste has no potential threat to environment and human health. • Utilization of RAP reduces both greenhouse gas emissions and water withdrawals. • Utilization of rubber reduces greenhouse gas emissions and dust particles. • Substitution virgin binder with polystyrene can enlarge the life expectancy. • Environmental and economic effects of waste materials are demanded. Solid waste materials refer to those municipal or industrial or even domestic wastes that are massively produced during manufacture as well as daily life. A wide variety of solid wastes are generated, but only a few of them are employed in pavement structures. To achieve the task, papers between 2014 and 2019 from top journals which address waste management, waste characterization, and economic and environmental assessment were collected at first. Then, the scope of solid waste materials was narrowed down based on their applications, In the end, six most popular solid waste materials were selected for further study and for the review, namely recycled concrete aggregates, reclaimed asphalt pavement, fly ash, bottom ash, waste rubber, and waste plastics. The reason why only these six solid waste materials are selected is that the rest are neither massively produced not can they be directly used in pavement structures. This review article contains structural properties, treatments, novel researches, environmental analysis, and economic analysis of each solid waste material. The objective of this review article is to provide future researchers with the latest research findings, limitations and improvements in this subject. In conclusion, quite a few novel researchers in terms of workmanship, construction methodology, and treatments are collected for all six materials. Furthermore, an increasing number of findings have proven that most solid waste materials have both environmental and economic benefits when applied in field. Future researchers are encouraged to implement researches on solid waste materials in pavement engineering with consideration of both material properties and environmental/economic effects. [ABSTRACT FROM AUTHOR]

The traditional asphalt mixture surface texture measurement methods cannot provide the distributions of the texture, which is necessary for studying the influence mechanism of texture on tyre/pavement interaction performance. A non-destructive 3-dimensional image-based texture analysis method (3D-ITAM) is developed based on the 3D surface reshaping and spectral analysis techniques. Mixture 3D surface is reshaped based on the photometric stereo method using the acquired tricolour digital images. Spectral indicators representing mixture surface texture distribution properties are calculated from 3D-ITAM software. Additionally, the traditional texture indicator (i.e. mean texture depth) is also calculated. The 3D-ITAM results are confirmed with both macro and micro-texture indicator values from the sand patch method (SPM) and hand-push friction tester (HFT), which are two widely used in practice though they cannot capture the distribution property of surf ace texture. It was demonstrated that the 3D-ITAM results correlate well with SPM and HFT and can be considered as an effective method to characterise the mixture surface texture. [ABSTRACT FROM AUTHOR]

• The relationship between structure and properties of polyurethane is introduced. • Polyurethane modified asphalt has good compatibility and high-temperature stability. • The application of polyurethane in asphalt pavement maintenance is presented. • The polyurethane mixture has excellent properties and is suitable for functional pavement applications. • The application of polyurethane waste in asphalt pavement is a new research field of its recycling. Asphalt pavement often suffers from rutting, aging, cracks, and pits during the life cycle. Although traditional polymer modifiers can improve asphalt properties to some extent, its storage stability and aging resistance still need to be improved. Polyurethane (PU) has been used in asphalt pavement engineering because of its high mechanical properties, durability and fatigue resistance. This paper introduces the relationship between the structure and properties of PU and describes possible optimization of the raw materials of PU suitable for modified asphalt according to the pavement performance. The applications of PU in modified asphalt, pavement maintenance, foamed asphalt, and its mixture are reviewed. The results show that modified with PU asphalt has good deformation resistance, aging resistance, fatigue resistance, and high-temperature storage properties after physical and chemical modification. At the same time, PU can also improve the temperature stability and mechanical properties of emulsified asphalt. The PU mixture has excellent properties and can be used to prepare functional pavement such as water penetration, noise reduction, and anti-skidding. The application of PU waste materials in asphalt pavement opens up a new direction for its recycling. [ABSTRACT FROM AUTHOR]

• Combining microcapsules with epoxy resin can solve the leakage of PCMs. • The heat exchange system was developed to give real-time temperature recording. • The specific heat capacity of EPC-PCM varied significantly with temperature. • Pentadecane caused slight decrease in thermal conductivity of EPC-PCM with temperature increasing. • The specific heat capacity and thermal conductivity of EPC-PCM were recommended. To obtain the phase change materials (PCMs) with good stability in the asphalt mixture, the epoxy resin composites shape-stabilized phase change material (EPC-PCM) was prepared by encapsulating the pentadecane microcapsule, which was prepared with pentadecane, nano-silica, and ethyl cellulose by physical compounding, with epoxy resin (EP). The prepared EPC-PCM had good thermal storage performance, thermal stability and mechanical properties. The specific heat capacity and thermal conductivity of EPC-PCM were respectively measured by heat exchange system and Kemtherm QTM-D3 thermal conductivity meter. Studies showed that the specific heat capacity of EPC-PCM varied significantly with temperature due to the phase change properties of pentadecane and it could be divided into solid-state region, fuzzy region (phase transition region) and liquid-state region. According to the correlation between specific heat capacity and temperature, the regression equation between the specific heat capacity of EPC-PCM with temperature was established. The thermal conductivity of EPC-PCM decreased slightly with the increase of temperature, which was similar to that of pentadecane, but opposite to that of epoxy resin. [ABSTRACT FROM AUTHOR]

• Effects by aggregates on asphalt demulsification rely on its chemical compositions. • Magnesium oxide significantly accelerated the demulsification of emulsified asphalt. • Correlation between chemical compositions and demulsification rate were revealed. Emulsified asphalt as an indispensable raw material for pavement engineering construction is subjected to various combinations of aggregates and varying environmental conditions leading to uncontrollable demulsification speed. In this respect, this research examined the influence of chemical composition of aggregate on emulsified asphalt demulsification speed. Three representative types of domestic road limestone aggregates with various appearances were studied by chemical analysis method. Experimental results indicate that the Magnesium oxide, alumina, calcium oxide, ferric oxide and silicon oxide were the main chemical compositions of limestone aggregate and their contents varied significantly among different types of aggregate. Ultraviolet spectrophotometry was used to evaluate effects of each chemical component on the demulsification speed of emulsified asphalt. Results indicate that mixing ratio of chemical components has a significant effect on demulsification speed of asphalt emulsion. Magnesium oxide accelerated the demulsification speed of emulsified asphalt, while calcium oxide showed an opposite trend. Iron oxide, alumina and silica had little effect on the speed of demulsification. Finally, grey correlation analysis was performed, and a clear relationship was established. The results which are expressed as the magnesium oxide, alumina, iron oxide and silicon dioxide content with differing ratio in the aggregate affected significantly on the demulsification speed of emulsified asphalt. However, there is no clear relationship between the demulsification speed and emulsified asphalt when the ratio of the calcium oxide content is changed. [ABSTRACT FROM AUTHOR]

Cold central-plant recycling (CCPR) is a technical method for the repair and maintenance of old asphalt pavement. However, this method lacks a complete evaluation system. In this study, various influencing factors were investigated and analyzed to establish a comprehensive and systematic evaluation system for CCPR pavement. A full-life staged evaluation system for CCPR pavement was established from perspectives of old pavement investigation and design, construction technology, management, and pavement performance and benefits. This evaluation system covered 5 level-1 indexes, 19 level-2 indexes, and 30 level-3 indexes, which were introduced in the present study. Weights of different indexes were determined by combining various evaluation methods, such as improved analytic hierarchy process and fuzzy comprehensive evaluation, and mutual influences of indexes. The CCPR pavement was evaluated based on the G316 repair and maintenance projects in Hanzhong of Shaanxi Province of China in 2017. Results demonstrate that the performance and benefits of CCPR pavement have the highest weight. Three level-1 indexes, namely, old pavement investigation and design, construction technology, and pavement performance, are evaluated to be good, while benefits and management are excellent. The overall evaluation score is 84.8, and the overall grade is good. The evaluation results conform to practical engineering situations. The proposed evaluation system can provide references to evaluate CCPR pavement. [ABSTRACT FROM AUTHOR]

• The use of Solution Road RomixSoilfix in granular base material is evaluated. • Deformation performance of SRX-GBM in different stress states is analyzed. • Field application and evaluation of SRX-GBM are performed in highway. Granular base material (GBM) is widely used as a base course in flexible pavement, since it has good performances to disperse stress and resist deformation. However, due to the increasing cost of pavement construction resulted by the low stiffness of GBM, the application of flexible pavement was rarely reported in Chinese expressways. This paper aimed to investigate the effect of Solution Road RomixSoilfix (SRX) on deformation performance of GBM and to evaluate the feasibility of SRX modified GBM (SRX-GBM) as a flexible base in expressway structure. A series of experimental tests were performed to analyze the influence of SRX content on curing process, stability and deformation performance of SRX-GBM. Subsequently, a flexible pavement was constructed using the SRX-GBM base course at the field sections on Tengchong to Longchuan Expressway in Southwest China. Results show that the use of SRX improves the California bearing ratio (CBR) of GBM, which raises from 145% to 417%. The dry shrinkage resistance and water stability of SRX-GBM are obviously better than cement-stabilized macadam. The results of triaxial tests demonstrate that the resilient behavior of SRX-GBM is dependent on the stress characteristics and curing times. The existing stress-related model is available for evaluating the changes of stress contribution to the Mr with the increase of SRX content. Since the base course has a high residual moisture content in a humid climate, the CBR of 250% was proposed by field CBR and deflection tests as a criterion for controlling curing time. [ABSTRACT FROM AUTHOR]

• A cold patching asphalt liquid is developed with high performance and easy storage. • Effect of asphalt components on its performance is statistically analyzed. • The diesel plays a key role in properties of cold patching asphalt liquid. The cold patching asphalt liquid (CPAL) is an environment-friendly paving material, which is more preferable in pavement construction and has lower energy consumption than the hot mix asphalt. However, the CPAL is mainly applied in the quick repair of potholes because of the limitation in its cost and storage stability. This study primarily investigates the effect of the compositions and contents of CPAL on its road performance through the multivariate analysis to develop a low-cost and storable CPAL. In this study, the CPAL was synthesized by base asphalt, diesel, diethylene glycol (DG), oleic acid (OA), and coconut oil acid diethanolamine (COAD). Orthogonal experiments with four factors and four levels were performed to optimize the mechanical properties of CPAL. The microstructure and characteristic functional groups of different CPAL schemes were analyzed to further understand the influence of different components of CPAL on its pavement performance. Results show that the proposed multivariate evaluation method in this study can accurately evaluate the significant relationships between different functional components and properties of CPAL. Furthermore, the dosage of diesel should be strictly controlled in the productions considering that only the t value of diesel passes the inspection. The optimal design scheme of CPAL in this study is 20% diesel, 0.6% DG, 6% OA, and 6% COAD, and its mixture has high adhesion, strength, and good storage stability in pavement engineering. The multivariate evaluation method is also conducive for scientifically developing a green and high-performance road material. [ABSTRACT FROM AUTHOR]

[Display omitted] • 3D porous graphene (3DPG) as reinforced additive was investigated in SBS/crumb rubber blend-modified asphalt. • 3DPG can significantly improve high and low-temperature performance and fatigue life of SBS/crumb rubber blend-modified asphalts. • The nanopores in 3DPG can effectively enhance the compatibility of SBS and crumb rubber in asphalt system by virtue of its unique amphiphilicity. • 3DPG as a new synergist presents a promising solution for the critical issue of wide adoption of crumb rubber modified asphalt for high-performance pavement. Styrene-butadiene-styrene (SBS)/crumb rubber (CR) blend-modified asphalt is a desirable binder for pavement engineering with both environmental and economic benefits. However, the inherent incompatibility of SBS and CR in asphalt is still a critical issue. Herein, 3D porous graphene (3DPG) with high surface area and rich micropores as reinforced additive was investigated in SBS/CR blend-modified asphalt for the first time. The experimental results demonstrate that incorporating 3DPG can effectively improve the compatibility of SBS and CR in asphalt and thus significantly enhance the high and low temperature performance and fatigue resistance of the modified asphalt, compared with that without 3DPG. Theoretical calculations further reveal that the nanopores in graphene can endow graphene with electrophilic property, providing a capability of absorbing nonpolar molecules in asphalt while the non-pore part in graphene can interact with polar molecules by conventional π − π stacking. The two forces within graphene can break the original colloidal structures of asphalt, which is conductive to the homogenous formation of SBS network and swelling of CR in asphalt, significantly promoting the pavement performance of the modified asphalt. This work presents the great potential of 3DPG as new additive to solve the inherent incompatibility of SBS/CR blend-modified asphalt for high-grade pavement engineering. [ABSTRACT FROM AUTHOR]

• A piezoelectric energy harvester with both ends fixed piezo-transducers is designed. • The 50 cm × 20 cm module generates 2080 mW max and 20.79 mW/cm3. • Optimized device installed on the rest area successfully operated LED indicators. • The harvesters have produced stable output performance and durability for 5 months. The purpose of this research was to demonstrate a road-compatible piezoelectric energy harvester (RPEH) that uses the energy to power self-powered sensors and vehicle indicators. The demonstrated RPEH (20 × 50 × 10 cm3) with 80 piezoelectric devices can efficiently convert mechanical energy stemming from the small vertical displacement (1.45 mm) from vehicles into electrical power. The maximum voltage is 113.5 V, the maximum current is 25.71 mA, and the maximum power is 661 mW (6.61 W/m2) at an impedance resistance level of 0.9 kΩ under a z-axial load. The high-power RPEH was initially installed at a highway rest area. The measured output performances of the installed module on the actual roadway in the test setup area were a maximum voltage of 196 V and output power of 2080 mW (20.79 W/m2) at a vehicle speed of 30 km/h. Tests of the RPEH module demonstrate its ability to measure temperature, strain, and leakage values in real time and the generated energy provides sufficient power to illuminate LED indicators. It was also found that the z-axial loaded piezoelectric devices with a two-end fixed beam provide high output power with low levels of vertical displacement, making it highly efficient and durable for actual highway energy-harvesting applications. [ABSTRACT FROM AUTHOR]

Unbound granular materials are widely used in the base and subbase layers of pavement systems. Currently, the compaction quality assurance (QA) of unbound granular base is mostly density-based with many drawbacks and is to be replaced by modulus-based QA. The Light Weight Deflectometer (LWD) test, which is often used to determine the stiffness of unbound granular materials, is a promising tool for modulus-based compaction QA but needs a more fundamental understanding of its experimental configuration and data interpretation. We build a digital model that adopts a discrete element method to model LWD field tests and account for the effects of moisture and finer particles by adopting a modified Hertz contact model which includes a component of attractive force. We investigate the relations between microscopic parameters and macroscopic material properties qualitatively, finding that the LWD modulus increases with model suction which is reversely related to moisture content, or interparticle friction which is reversely related to fine content. We calibrate this model using test results from field LWD tests. From the modeling results, we observe a trend of decreasing stiffness with increasing moisture or fine particle content, which agrees with existing experimental data. With the quantitative relations obtained from calibration, the model can be used to predict the LWD modulus of unbound granular base. [ABSTRACT FROM AUTHOR]

Highlights • A energy harvesting device with a group of piezoelectric transducers is designed. • Optimal device dimensions for light and heavy traffic loading are identified. • Device material configurations are optimized by mechanic-electric responses test. • The 15 cm × 15 cm device achieves output power of 50.41 mW with the loading of 4 kΩ. Abstract This study designs a compression-based pavement energy harvesting device with a group of piezoelectric transducers and investigates the selection of the component materials based on four technical device requirements for enhanced the electric energy output of power-generation pavements. The external dimensions of the proposed devices are optimized based on vehicle wheelpath distribution, tire trace patterns, and vehicle roller compaction conditions. The array pattern of the piezoelectric device is designed based on the driving characteristics. Various device material configurations are examined using different cover plates, rubber pad thicknesses, protective pads, and transducer specifications for optimal mechanic-electric response characteristics. A 150 mm × 150 mm type device is tested as an example and its electrical output performance is evaluated under typical road loading environments. Subsequently, a comparative analysis of various disclosed piezoelectric harvesting device technology were conducted and further research plan was developed. The selected modified polypropylene or aluminum plate, steel plate, modified polypropylene bar, and fiber heat insulation plate are suitable for the device which meets the application demands. The optimum device dimensions under light and heavy traffic conditions are 100 mm × 100 mm and 150 mm × 150 mm, respectively. The optimum configuration of the device includes a modified polypropylene upper cover plate, 1 mm rubber pad, ball-type protective pad, and eight laminated transducers. In addition, parallel connection of stacked transducers is more suitable for energy collection and reuse from traffic-induced pavement vibrations. Under the loading of 0.7 MPa and 15 Hz, the 150 mm × 150 mm device with nine parallel transducers achieves a maximum output power of 50.41 mW, and the corresponding optimum loading is 4 kΩ. Under the loading of 0.2 MPa and 10 Hz, the device achieves a maximum output power of 2.92 mW, and the corresponding optimum load is 10 kΩ. The performance of piezoelectric device designed in this paper excels that of many other available devices. [ABSTRACT FROM AUTHOR]

The use of a broad range of asphalt additives is a well-established practice in road pavement engineering for the production of high-performance hot-mix and warm-mix asphalt mixtures. The study aimed to verify and to assess, though an analytical-sensory approach based on artificial olfactory system (AOS), the effects of five different asphalt additives (chemical additives, odor suppressant agent and wax modifiers) on the odorous patterns of asphalt emissions at typical mixing and laying temperatures. The AOS has made possible to identify a specific odor fingerprint of each additive. However, once added to asphalt, these agents did not establish with binder effects of synergy, additivity or antagonism, but appear to be as neutral elements by an odorous point of view. The odorous patterns of emissions generated by heating neat asphalt at various temperatures in laboratory scale tend to coincide with those of asphalt/additive mixtures, underlining how the bituminous binder odor resulted to be hiding or masking compared to that of only-additives. [ABSTRACT FROM AUTHOR]

• The compaction process of asphalt mixture was simulated in the laboratory. • The migration and rotation characteristics of aggregate particle was analyzed during asphalt mixture compaction. • The development of surface texture was explored during asphalt mixture compaction. • The compaction mechanism of asphalt mixture was discussed in combination with the Stribeck curve. Pavement performance is not only affected by materials and production but also by compaction quality. This paper investigates the migration and rotation law of coarse aggregate during asphalt mixture compaction using the statistical means based on 2D image analysis. The variation of surface texture during compaction was extracted by laser scanner, and its anti-sliding performance was tested. The compaction mechanism was then discussed in combination with the Stribeck curve. The results show that mixtures with different gradations required different compaction energy during compaction, the AC-13 mixture was easier to compacted than the SMA-13. The aggregate contact developed rapidly in the early compaction stage in the horizontal direction but increased gradually in the vertical direction. With the compaction, the radial angle of the aggregate tended to be consistent in the horizontal direction and the major axis of the aggregate approached to the horizontal axis in the vertical direction. At the same time, the aggregates on the surface of the mixture were embedded with each other with compaction, and the surface structure gradually decreased. Combined with the aggregate contact, asphalt mortar viscosity and the Stribeck curve theory, the compaction process of asphalt mixture could be divided into pre-mixed lubrication dominated by asphalt lubrication and post-mixed lubrication dominated by aggregate contact. The research results offer a reliable basis for studying the compaction mechanism and improving the construction quality control of the asphalt pavement. [ABSTRACT FROM AUTHOR]

In performing pavement life cycle assessment (LCA), users are facing various reports of energy intensity coefficient (EIC) of pavement materials which differ considerably among data sources and therefore alter the LCA results significantly. Instead of selecting a certain EIC without or of little explanation for the current pavement LCA practices, this study proposed a methodology to build probability density function (PDF) for EIC based on available data-set and their qualities. Each data was first evaluated about the data quality indicator (DQI) through data quality pedigree matrix and converted to PDF in modified Beta distribution form. Three weighting methods, the DQI one, coefficient of variation (COV) one and analytical hierarchy process (AHP) one, were developed to assign weightings for different data. Monte Carlo simulation was run with the weighted PDF of each data as input to obtain the ultimate PDF for EIC. A case study to estimate the bitumen’s EIC with eight data samples were performed using the proposed methodology. It is found (1): the estimates by the proposed methodology is of higher reliability (lower COV) compared to any single data due to utilisation of information of the overall data samples; (2) the AHP weighting method is most favoured despite the results of the three weighting methods are close; (3) the central estimates of bitumen’s EIC are between5.4~5.8 MJ/kg. The proposed methodology is helpful in aiding calculating EICs for pavement materials and capturing uncertainties in LCA results in a statistical sense. [ABSTRACT FROM AUTHOR]

Although piezoelectric power generation for pavements is technically feasible, harvesting energy in a stable and efficient manner still presents several challenges. This paper designs and assesses stacked piezoelectric energy-harvesting power generation devices for pavements, in which energy output and road coupling are considered. Following corresponding technical specifications, the dimensions of the proposed power generation device are determined, and the unit is assembled for subsequent testing in terms of its electrical energy outputs. The energy outputs are analyzed in various series and parallel configurations of the units, different loads, and frequency conditions. Results indicate that power generation device with the dimension of 100 mm × 100 mm achieves optimal power generation outputs. The electrical output is positively correlated to the number of parallel piezoelectric energy-harvesting units, the magnitude of load, and the frequency of traffic action. The maximum output at the 0.2 MPa load magnitude and 10 Hz load frequency is 0.88 mW, and the corresponding optimum load is 20 kΩ. The maximum output at the 0.7 MPa and 15 Hz load level can reach up to 11.67 mW, and the corresponding optimum load is 10 kΩ. Subsequently, Mechanical Testing and Simulation (MTS) is performed with 40,000 load cycles, and the overall deformation of the power generation device is minimal and the electrical outputs of the piezoelectric energy-harvesting units remain stable. Finally, future research plan is discussed. [ABSTRACT FROM AUTHOR]