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Graphene Tourmaline Composite Micropowder (hereinafter referred to as GTCM) modified asphalt was prepared by the ball milling method. The effects of different temperatures and different frequencies on the high-temperature performance of composite-modified asphalt were evaluated by dynamic shear rheological test, and the viscoelastic properties of composite-modified asphalt under different stresses and different temperatures were analyzed. The low-temperature rheological properties of GTCM-modified asphalt were analyzed by bending beam rheological test, and its mechanism was analyzed by Fourier transform infrared spectroscopy (FTIR) test. The results show that the temperature sensitivity and anti-aging resistance of GTCM-modified asphalt are significantly higher than that of tourmaline-modified asphalt. The improvement effect gradually increases with the increase in graphene powder content, and its addition does not change the viscoelastic properties of asphalt. The complex shear modulus and phase angle of GTCM-modified asphalt at appropriate temperatures are more conducive to tourmaline-modified asphalt and matrix asphalt, which can improve the rutting resistance of asphalt. In the same type, with the increase in composite modified micropowder content, the rutting resistance of modified asphalt is better. The improvement of rutting resistance of GTCM-0.5, GTCM-1.0 and GTCM-1.5-modified asphalt can reach 12.95%, 10.12% and 24.25%, respectively; the improvement range is more complicated due to temperature and frequency changes. The GTCM-modified asphalt has good low-temperature crack resistance. The creep stiffness modulus of GTCM-modified asphalt decreases with the increase in load time under different types and dosages, and its stiffness modulus is smaller than that of tourmaline-modified asphalt and mineral powder asphalt mastic. The creep rate increases with the extension of load time, which is greater than that of tourmaline-modified asphalt and mineral powder asphalt mastic. When the load was 60 s, the creep stiffness modulus of GTCM-0.5, GTCM-1.0 and GTCM-1.5-modified asphalt decreased by 5.75%, 6.97% and 13.73%, respectively, and the creep rate increased by 1.37%, 2.52% and 4.35%, respectively. After adding GTCM or tourmaline to the matrix asphalt, no new functional groups were produced due to the chemical reaction with the asphalt. [ABSTRACT FROM AUTHOR]

As an effective preventive maintenance coating for asphalt pavement, the fog seal is developing from traditional waterproof coatings to multifunctional directions such as improving aging asphalt performance, catalytic degradation of exhaust gas, anticoagulant ice, etc. To promote the diversified development and application of fog sealing technology, this paper reviews the current research progress on fog sealing maintenance technology for asphalt pavements. Firstly, the main materials used in fog seals, such as emulsified asphalt, fine sand, modifiers, and functional fillers, were summarized. Then, fog seals were classified into enhanced fog seals and functional fog seals based on performance orientation, and the advantages and disadvantages of various fog sealing technologies were discussed. Furthermore, the permeability, skid resistance, waterproofing, adhesion, opening time to traffic, and stabilization of loose aggregates of fog seals were summarized. It is recommended to enhance the technical requirements for the adhesion and water permeability coefficient of fog seal and to supplement the increase amplitude in TSR and RMS as technical requirements for the waterproofing performance of fog seal. The single-side scatter loss test is recommended for evaluating the reinforcement effect of fog seals on asphalt pavements. The functional characteristics of fog seals, such as restoring aged asphalt, catalyzing the degradation of harmful gases, and anti-icing, were summarized, and corresponding technical standards were proposed. Finally, the modification mechanism of emulsified asphalt for fog seal, and the action mechanisms of restorative, photocatalytic, and anti-icing fog seal were elucidated. The durability of enhanced fog seals under complex working conditions, the long-term performance of photocatalytic and anti-icing fog seals, and the research on non-emulsified asphalt fog seals need to be thoroughly studied. The research findings contribute to the further improvement of relevant specifications for fog sealing technology and provide a reference for enhancing and diversifying the maintenance effectiveness of fog seal on asphalt pavements. • The fog sealing materials include emulsified asphalt, fine sand, modifiers and fillers. • The fog seal is divided into enhanced fog seal and functional fog seal. • It is recommended to improve the requirements for road performance of fog seal. • The functional technical requirements for fog seal are proposed. • The mechanism of bio oil modified emulsified asphalt needs to be further explored. [ABSTRACT FROM AUTHOR]

To ensure the effective bonding of each structural layer of pavement and improve the service quality and durability of pavement, the waterborne epoxy resin (WER) emulsified asphalt (WEREA) tack coat binders were prepared by using polyurethane-epoxy resin. The basic properties of WEREA, such as tensile strength, adhesion to aggregate, high temperature heat resistance and low temperature impact resistance were studied. Its composition and ratio were optimised. The waterproof, bonding and durability performance of WEREA used in pavement tack coat were evaluated. The results show that WEREA prepared by polyether polyurethane modified E-51 epoxy resin (PUD-E51) has higher early and late strength. Its tensile strength was 1.75 MPa after curing for 7 days. The basic properties of WEREA, including adhesion to aggregate, heat resistance and impact resistance were better than those of SBS modified asphalt and crumb rubber modified asphalt binder. The tack coat of WEREA cannot seep under the dynamic water pressure of 0.6 MPa for 30 min. According to the interlaminar shear strength, the recommended spraying amount of the WEREA tack coat was 1.0 kg/m2. The WEREA could guarantee the effective bonding of each structural layer of the pavement, and improve the durability of the tack coat and pavement. [ABSTRACT FROM AUTHOR]

To explore the influence of water on the multiscale adhesive behavior between asphalt binder and aggregate, the nanosurface morphology and microsurface energy of asphalt binder and the macrobonding force between the asphalt binder and aggregate over different soaking times were examined using atomic force microscopy (AFM) and the pull-off test. Relationships between the macrobonding and the nanosurface roughness as well as the microsurface energy were analyzed. The results demonstrated that the effect of water on the surface morphology of asphalt binder was important. After immersion in water, water-induced bulges occurred on the asphalt binder surface, which further changed the nanosurface roughness and the surface energy of asphalt. As per the sensitivity results, it can be concluded that the surface energy of asphalt and the effective contact area between asphalt and aggregate were reduced because of moisture, thus resulting in the failure of adhesion. [ABSTRACT FROM AUTHOR]

Dynamic modulus is a key evaluation index of the high-modulus asphalt mixture, but it is relatively difficult to test and collect its data. The purpose is to achieve the accurate prediction of the dynamic modulus of the high-modulus asphalt mixture and further optimize the design process of the high-modulus asphalt mixture. Five high-temperature performance indexes of high-modulus asphalt and its mixture were selected. The correlation between the above five indexes and the dynamic modulus of the high-modulus asphalt mixture was analyzed. On this basis, the dynamic modulus prediction models of the high-modulus asphalt mixture based on small sample data were established by multiple regression, general regression neural network (GRNN), and support vector machine (SVM) neural network. According to parameter adjustment and cross-validation, the output stability and accuracy of different prediction models were compared and evaluated. The most effective prediction model was recommended. The results show that the SVM model has more significant prediction accuracy and output stability than the multiple regression model and the GRNN model. Its prediction error was 0.98–9.71%. Compared with the other two models, the prediction error of the SVM model declined by 0.50–11.96% and 3.76–13.44%. The SVM neural network was recommended as the dynamic modulus prediction model of the high-modulus asphalt mixture. [ABSTRACT FROM AUTHOR]

To further improve the emission reduction effect on asphalt smoke and mitigate environmental pollution, a novel emission reduction agent (TBD) combined with physical adsorption and chemical degradation was synthesized with tourmaline, biochar, and diatomite. The testing and evaluation method for the emission reduction efficacy of TBD has been established. The optimal preparation method and parameter of TBD were selected based on macroscopic performance and microscopic analysis. The results indicated that TBD had the highest emission reduction rate and most stable storage under the ball milling process. According to XRD, FTIR, SEM, and BET, TBD with the multistage porous structure and spontaneous polarization effect was synthesized by the ball milling parameter of 200r-2 h. The emission reduction efficiency of TBD on the asphalt smoke effect was enhanced by a synergistic interaction of the physical adsorption and chemical degradation. The emission reduction rate was up to 65.84% for 3 h. This laid the foundation for the development and promotion of low-pollution asphalt. [ABSTRACT FROM AUTHOR]

This study aims to optimize the bonding performance between the wearing course and the used pavement or the underlying layer and further improve the service quality and durability of the open-graded friction course with small particle size aggregate (ultrathin OGFC). The ultrathin OGFC including waterborne epoxy resin emulsified asphalt (WEA) bonding layer and open-graded asphalt concrete with 9.5 mm nominal maximum aggregate size gradation was optimized. The construction timing of the open-graded asphalt mixture was determined. The road performance, wear resistance, and interlaminar bonding durability of the ultrathin OGFC were comprehensively evaluated. The results show that, based on the basic properties of the open-graded asphalt mixture, its asphalt aggregate ratio is recommended to be 5.0–5.5%. Based on interlaminar shear strength, it is recommended that the open-graded asphalt mixture is paved immediately after WEA bonding material was sprayed, and the bonding layer does not spread aggregate. The WEA containing 20% waterborne epoxy resin (WER) is recommended as bonding layer for the ultrathin OGFC, and the optimized spraying amount is 1 kg/m2. The ultrathin OGFC has good antisliding, drainage, and wear resistance properties. The interlaminar bonding performance, water stability, and durability of WEA bonding layer are obviously better than those of high viscosity asphalt (HVA) and SBS-modified asphalt. The WEA bonding layer can better resist interlaminar shear failure and improve the service quality and service life of the ultrathin OGFC. [ABSTRACT FROM AUTHOR]

The extreme learning machine (ELM) algorithm optimized by genetic algorithm (GA) was used to quickly predict the low-temperature rheological properties of styrenic block copolymer (SBS) modified asphalt through the properties of the raw materials. In this work, one hundred groups of survey data and test data were collected and analyzed. Fourteen vital raw material parameters, such as chemical composition indexes of matrix asphalt and technical indexes of SBS modifier, were selected as the input parameter. The stiffness modulus and m-value of SBS modified asphalt were taken as the output parameter. Then, the GA-ELM prediction model of low-temperature rheological properties was established. According to comparison and analysis with other prediction models, the accuracy and output stability of the GA-ELM prediction model were verified. The results show that the GA-ELM model had obvious accuracy and efficiency. It can be used to predict the low-temperature rheological properties of SBS modified asphalt. Compared with the traditional prediction models, the error of the GA-ELM model was reduced by 68.97–81.48%. [ABSTRACT FROM AUTHOR]

The purpose is to improve performance of asphalt by synergistic enhancement of graphene and tourmaline. Graphene/tourmaline composite modified asphalt was prepared. The basic properties and rheological properties of graphene/tourmaline composite modified asphalt were analyzed systematically. The results indicate that the basic viscoelastic properties of asphalt were not destroyed after graphene/tourmaline composites added into asphalt. The rutting resistance of graphene/tourmaline composite modified asphalt was superior than tourmaline. And the larger the composite material content, the superior the rutting resistance of modified asphalt. The rutting resistance was increased by 10.12%. [ABSTRACT FROM AUTHOR]

To further improve the emission reduction efficiency and enhance the road performance of emission reduction modified asphalt. A low-pollution asphalt (TBD-A) was prepared with tourmaline, biochar, and diatomite (TBD). A testing and evaluation method for the emission reduction efficacy of TBD-A has been proposed. The road performance of TBD-A was evaluated based on DSR, MSCR, BBR, and LAS. The evolution law of the emission reduction effect of TBD-A was clarified. Based on DSC, FTIR, and TG, the improvement mechanism of the road performance and emission reduction mechanism of TBD-A were revealed. The results show that the high-temperature performance, creep recovery ability, and fatigue life of TBD-A increase with TBD content rising. The low-temperature performance of TBD-A is superior to that of asphalt slurry. Controlling the TBD content and temperature can ensure the excellent low-temperature performance of TBD-A. The emission reduction efficacy of TBD-A increases as temperature and adsorption time rise. The comprehensive emission reduction rate of TBD-rubber-powder asphalt is the highest, reaching 64% at 190 °C. TBD and asphalt are physically blended. TBD increases asphalt's glass transition temperature while decreasing the thermal decomposition rate. The temperature stability and sensitivity of asphalt have been improved. Asphalt harmful substances are adsorbed by the multi-level pore structure of TBD, as well as are reduced and degraded by the spontaneous polarization effect. • The road performance of low-pollution asphalt was evaluated. • The emission reduction efficacy of low-pollution asphalt was clarified. • The modification mechanism of low-pollution asphalt was revealed. [ABSTRACT FROM AUTHOR]

• Thermal resistance aggregates wrapped with organosilicon resin are prepared. • The surface wrapping effect of different thermal resistance aggregates are evaluated. • The indoor sunlight simulation device is designed to test the heat resistance performance. To improve the road performance and heat resistance of thermal resistance aggregates, thermal resistance aggregates wrapped with organosilicon resin were prepared. The optimal surface treatment process of different thermal resistance aggregates was determined. The surface wrapping effect of different thermal resistance aggregates were evaluated based on the macropore structure and microsurface morphology. In addition, the road performance of different thermal resistance aggregates before and after surface treatment were compared and analyzed. The heat resistance performance of different thermal resistance asphalt mixtures was tested by an indoor sunlight simulation test. Furthermore, the effect of surface treatment on road performance and heat resistance of a thermal resistance asphalt mixture was evaluated. The results showed that the surface treatment of shale ceramsite with organosilicon resin achieved the best result. The 24 h oil absorption decreased to 2.05%. The surface pore sealing rate was as high as 78.3%, and the opening pores could hardly be seen in the SEM images. After being surface treated with organosilicon resin, the water absorption, crushing value and abrasion value of three kinds of thermal resistance aggregates decreased by 82.87%–94.50%, 6.8%–22.07% and 10.87%–28.56%, respectively, and their adhesion increased to grade 5. The surface treatment of thermal resistance aggregates could significantly improve the high temperature performance and water stability of thermal resistance asphalt mixtures. There was little effect on the low temperature performance, while the heat resistance performance of the thermal resistance asphalt mixture was improved to varying degrees. [ABSTRACT FROM AUTHOR]

Highlights • Based on two mixing methods, the road performance of tourmaline modified asphalt mixture were analyzed. • A comprehensive performance evaluation system for tourmaline modified asphalt mixture was established. • Performance of tourmaline modified asphalt mixture was evaluated based on grey target decision method. Abstract Tourmaline modified asphalt mixture has the air purification effect and is an excellent low-carbon road material. However, previous studies mainly focused on the improvement of road performance for tourmaline modified asphalt mixture. There were few studies on its comprehensive performance evaluation. In order to further promote the application of tourmaline in the field of modified asphalt mixtures, tourmaline modified asphalt mixture was prepared. The comprehensive performance evaluation system for tourmaline modified asphalt mixture was established based on the grey target decision method. Based on two mixing methods, the road performance of tourmaline modified asphalt mixture were systematically analyzed, the comprehensive performance of tourmaline modified asphalt mixture was evaluated, the suitable content of tourmaline in the modified asphalt mixture was determined. The results show that the comprehensive performance evaluation system based on grey target decision method has good reliability and practicability. The comprehensive performance of tourmaline modified asphalt mixture achieves its best with 10% tourmaline. [ABSTRACT FROM AUTHOR]

Abstract This study addresses the difficulty in systematically and scientifically evaluating the comprehensive performance of low-carbon modified asphalt. Sixteen technical indexes were selected as evaluation indicators. The corresponding weight of each evaluation index was determined by the coefficient of variation method. The fundamental performance, environmental protection effect, and economic effect of low-carbon modified asphalt were analyzed systematically. A comprehensive performance evaluation system for low-carbon modified asphalt was established based on the efficacy coefficient method. Low-carbon modified asphalt using tourmaline anion powder was selected as an example for inspection. Its comprehensive performance was evaluated, and the optimal content of tourmaline anion powder was determined. The results showed that the comprehensive performance evaluation of low-carbon modified asphalt using tourmaline anion powder reflects well the actual situation, meaning that a comprehensive performance evaluation system for low-carbon modified asphalt based on the efficacy coefficient method is relatively reliable and useful. This study lays the foundation for the comprehensive performance evaluation and further application of low-carbon modified asphalt. Graphical abstract Image 1 Highlights • Sixteen evaluation indexes. • Comprehensive performance evaluation system for low-carbon asphalt. • Low-carbon asphalt using tourmaline anion powder. [ABSTRACT FROM AUTHOR]

This study presents a comprehensive pollutant reduction rating system for hot mix asphalt (HMA) with three Level I indices and ten Level II indices, covering various aspects in HMA pollutant emissions, energy consumption, and exhausts from construction equipment. The pollutant emission reduction effects are investigated not only in the laboratory for modified asphalt mixtures with various mixture gradation and binder types but also in the field for several warm mix asphalt (WMA) projects. Furthermore, energy consumption and emission data during pavement construction are obtained from 58 in situ highway projects in 10 provinces of China. Based on the hierarchical clustering method and Bayesian discriminant analysis, individual ranking systems are developed to quantify pollutant emission reduction effects and energy consumption. Subsequently, a comprehensive reduction rating system is established based on the analytic hierarchy process and approximation methods. A case study is demonstrated to implement the proposed system for the assessment of emission reduction effects. [ABSTRACT FROM AUTHOR]

Three novel asphalt modifiers with pollutant emission reduction effects and new emissions measurement equipment compatible with several preexisting asphalt production systems are developed in this paper. The effects of various modifier, asphalt binder type, and gradation of hot mix asphalt (HMA) on pollutant emissions are evaluated in the lab through a comprehensive experimental design. Furthermore, road performances are monitored to evaluate the emissions reduction of modified HMA mixture for production. With increasing modifier content, the emissions reduction performance is improved markedly, with maximum reduction of 70.5%. However, the impact of modifier content on pollutant emissions reduction tends to be insignificant for dosages greater than 20% of the initial asphalt weight. Changes in asphalt type and asphalt mix gradation are found to moderately impact the emissions reduction effect. Finally, the mechanisms of emissions reduction are investigated, primarily attribute to their physical and chemical adsorption and pollutant reductive degradation characteristics. [ABSTRACT FROM AUTHOR]

• The modified asphalt was classified based on the content of crumb rubber. • The modification effect of crumb rubber on asphalt was clarified. • Excessive crumb rubber content will damage some properties of modified asphalt. • The performance grades of the crumb-rubber asphalt and its mixture were proposed. The crumb-rubber-modified asphalt has attracted considerable attention owing to its excellent road service performance and low-carbon environmental protection characteristics. As studies focusing on expanding the applications of crumb-rubber-modified asphalts are limited, in this study, we systematically investigated the research trends of crumb-rubber-modified asphalts and their mixtures, different types of crumb rubber modified asphalts divided based on crumb rubber content. The preparation technology, modification mechanism and comprehensive performance of different types of crumb-rubber-modified asphalts and their mixtures were compared and evaluated, and based on the obtained mathematical statistics and relevant specifications, the performance grades of crumb-rubber-modified asphalts and their mixtures were divided. The results showed that the preparation of crumb-rubber-modified asphalt was mainly based on the high-speed shear method. With the increase in the crumb rubber content, the basic and rheological properties of the modified asphalt were significantly improved. However, problems emerged in the preparation of high-content crumb rubber asphalts, such as excessive viscosity and insufficient stability, excessive crumb rubber content can also hinder the compaction of the mixture and reduce its water stability. In view of the current traffic development focused to environmental protection and quality improvement, increasing the content of crumb rubber and improving the workability and storage stability of crumb rubber asphalt or using crumb-rubber- and resin-polymer-composite-modified asphalts are further research directions of crumb-rubber-modified asphalt-related technologies. [ABSTRACT FROM AUTHOR]

During the high-temperature construction of hot mix asphalt mixture, a large number of harmful emissions such as asphalt smoke are produced, which seriously endangers the workers' health and pollutes the surrounding environment. The object of this study is to reduce the emission of asphalt smoke and improve the construction environment. Tourmaline (T), graphene oxide (GO), KH 550 silane coupling agent (K) were used to prepare GO/KT-modified asphalt and the influence of modifier content on the asphalt basic performance was studied. The micromorphology and chemical constituents of the modified asphalt were analyzed, and the asphalt smoke adsorption effect of the modified asphalt was evaluated. It provides a useful reference for the green and sustainable development of road infrastructure. The results show that GO/KT composite powder can improve the asphalt basic performance. GO/KT has an excellent adsorption effect on asphalt smoke, and the emission reduction rate of GO/KT-modified asphalt can reach 41.11%. Considering the asphalt basic performance, asphalt smoke adsorption performance, and economic benefits, the recommended GO/KT and GO appropriate contents are 20 wt% and 1.0 wt%, respectively. [ABSTRACT FROM AUTHOR]

A large number of harmful components are produced during asphalt pavement construction under high-temperature conditions, causing heavy environmental pollution. Adding emission reduction agents to asphalt as an effective emission reduction technology has been widely used in different nations. However, few studies have attempted to compare the used emission reduction agents and their performances, resulting in the difficulty of the selection of emission reduction agents to reduce volatile organic compounds effectively and purposely. The objective of this review paper is to systematically summarize and analyze the state-of-the-art studies on asphalt volatile organic compounds emission reduction. In this study, the components in asphalt volatile organic compounds were summarized and the restrictions on asphalt volatile organic compounds emission in different nations are reviewed and summarized firstly. Then, the commonly used emission reduction agents of asphalt volatile organic compounds were completely investigated and sorted. Afterward, the emission reduction effect and engineering performance were compared in detail. Finally, the emission reduction mechanisms of different emission reduction agents were illustrated. The main findings show that the asphalt volatile organic compounds contain nearly ten categories of main components. The emission reduction effect of inorganic porous materials is superior to others. The organic polymer materials and the appropriate amount of inorganic materials can improve asphalt's engineering performance. The emission reduction mechanisms of emission reduction agents were divided into crosslinking reaction, adsorption, and piezoelectric/thermoelectric effect according to the interaction between asphalt volatile organic compounds and emission reduction agents. [ABSTRACT FROM AUTHOR]

• UHMWP were selected to prepare UHMWP modified asphalt and its high modulus mixture. • The change laws of the dynamic modulus of the UHMWP high modulus mixture with temperature and frequency were clarified. • Rubber powder were recommended to improve the performance of UHMWP high modulus asphalt mixture. High modulus asphalt mixtures are increasingly being applied owing to their excellent high temperature performance and fatigue resistance. Currently, they are mainly prepared with admixtures. Aiming at problems of complex processes and poor performance-cost ratios of admixture, Ultra-high molecular weight polymer (UHMWP) was selected as basic material, and cross-linked UHMWP was prepared by a crosslinking reaction. The performances of the UHMWP modified asphalt and cross-linked UHMWP modified asphalt were then compared. UHMWP was determined as modifiers. Through dynamic shear rheometer (DSR) and bending beam rheometer (BBR), the influences of UHMWP content on the basic performance and rheological performance of asphalt were investigated, and their microscopic modification mechanisms were revealed by Scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). The change laws of the dynamic modulus of the UHMWP high modulus mixture with temperature and frequency were clarified, and the change characteristics of their dynamic modulus master curves at different temperatures in different frequency ranges were analyzed. Subsequently, the performances of the different mixtures were evaluated. The results indicate that the performances of UHMWP modified asphalt were better than that of cross-linked UHMWP modified asphalt. As the UHMWP content increases, the high temperature performance of asphalt improves significantly. The rut factor of UHMWP-6 is 79.88% higher than that of UHMWP-4 at 70 ℃. On account of performance and cost, the recommended UHMWP content is 6%. The UHMWP is evenly bound by asphalt and has excellent compatibility. The content of UHMWP has a little effect on the phase change of asphalt. UHMWP mixtures have excellent mechanical performance, and their dynamic modulus reaches 21835 MPa at 15 ℃ and 10 Hz. As the temperature rises, the sensitivity of the dynamic modulus to frequency changes increases. [ABSTRACT FROM AUTHOR]

• Graphene could improve the adsorption properties of tourmaline. • Graphene/tourmaline composite powder could replace mineral powder. • Pavement performance of asphalt mixture is improved by adding composite powder. • Composite powder could reduce asphalt smoke emission effectively. This study addresses how to reduce the emission of asphalt smoke in the construction process of traditional hot mix asphalt mixture. The graphene/tourmaline composites were prepared based on tourmaline having the effect of adsorbing pollutants. The basic properties of composites and their adsorption effect on asphalt smoke were analyzed. Then, the composite powder was added into the environment-friendly asphalt mixture as filler. And the pavement performances and emission reduction performance of asphalt mixtures were studied. The results indicated that the basic properties of composite powder meet the requirements of specifications about filler in asphalt mixtures. Composite powder could be used to replace part of mineral powder, and the optimum replacement content was 17–20 wt%. The environment-friendly asphalt mixtures can effectively reduce asphalt smoke emission. The reduction rate of emission can reach 76.9–80.5%. [ABSTRACT FROM AUTHOR]

[Display omitted] • Optimal preparation parameters of nano-SiO 2 modified microcapsules are recommended. • The core content in nano-SiO 2 modified microcapsules is up to 85.39 %. • Nano-SiO 2 modified microcapsules improve strength at least 1.4 times and thermal stability 2.9 times. This paper presents nano-SiO 2 modified microcapsules prepared by in-situ polymerization to improve their performance. Low-quality vegetable oil was selected as the main material and Melamine Urea Formaldehyde (MUF) modified by nano-SiO 2 was selected as the shell material. Firstly, the optimal preparation parameters of the nano-SiO 2 modified microcapsules were determined, including the emulsifier type, emulsifier concentration, emulsifier shearing speed, the core-shell ratio, reaction pH, reaction temperature, and nano-SiO 2 content, respectively, by using the Scanning Electronic Microscope (SEM), Fourier Transform Infrared Spectroscopy (FTIR), Thermo-Gravimetric analysis (TGA) and nanoindentation test, etc. Secondly, the properties of the prepared microcapsules were evaluated. The particle size of the prepared nano-SiO 2 modified microcapsules was ∼ 78–96 μm, and the average size was 88.16 μm. The average core content was 85.39 %, which exceeds the upper limit of 80 % of existing microcapsules. The nano-hardness and Young's modulus were 0.33 and 2.63 GPa, respectively, improved by at least 1.4 times compared to existing microcapsules. The mass loss of microcapsules was 0.95 % at 182.73 °C, which is at least 2.9 times higher than the thermal stability of existing microcapsules. The results showed that the addition of nano-SiO 2 can obviously improve the performance of microcapsules. [ABSTRACT FROM AUTHOR]

• The solar radiation simulation test was developed to measure the field temperature of asphalt pavements. • The pavement performance of thermochromic material modified asphalt mixtures was evaluated. • The thermochromic material modification mechanism was revealed. The thermal effect of asphalt pavements on the surrounding environment in summer is of increasing concern since they absorb a great deal of heat from solar radiation and contribute greatly to the urban heat island effect. A novel thermochromic material modified asphalt binder is proposed to modulate pavement temperature by reversibly changing colors and reflectivity to solar radiation in response to temperature variations. In this study, an attempt is extended into the mixture scale. The cooling effect and pavement performance of thermochromic material modified asphalt mixtures are evaluated using a proposed solar radiation simulation test and various mechanical tests. The thermochromic material modification mechanism is revealed from the physical and chemical points of view. It is found that the addition of thermochromic additive to base binders has a significant cooling effect on asphalt pavements in summer. The maximum temperature reduction is observed at the bottom of the top asphalt layer and the top of the middle asphalt layer. Two types of thermochromic additives show positive and negative effects on rutting resistance. Thermochromic material modification has little effect on low-temperature cracking resistance and all thermochromic material modified mixtures exhibit good moisture stability. Preliminary recommendations on the optimum additive type and content of thermochromic material are proposed. The characteristics of coating, dispersion, and intactness of thermochromic additives in base binders significantly affect the pavement performance of asphalt mixtures. The particle size of the thermochromic additive and the chemical composition of shell material are critical to binder modification. [ABSTRACT FROM AUTHOR]