In order to explore the effect of aggregate type on the interface interaction between rubberized asphalt and aggregate, the representative molecules of base asphalt, rubberized asphalt, limestone (calcite), basalt (augite), and granite (quartz) were modeled by a molecular dynamics method. Additionally, asphalt–aggregate interface models were constructed by using the existing molecular models. The interface interaction between rubberized asphalt and different aggregates was analyzed by the radial distribution function (RDF), diffusion coefficient and adhesion energy density, and the simulation results were verified by a surface energy test. The results show that the interaction between asphalt and aggregate exists in the form of hydrogen bond, and the polarity of asphalt and aggregate has a great influence on the interaction. Calcite has the strongest interaction with asphalt among the three crystalline molecules. This conclusion further explains the phenomenon that alkaline aggregate has better adhesion to asphalt. The interaction between augite and crumb rubber is relatively strong, which leads to the maximum enhancement of the interaction between rubberized asphalt and augite. This study provides a reference for further research on the formation and failure of asphalt–aggregate interface interactions under various conditions and environments.

The effects of ageing on the microstructure and dynamic rheological properties of three modified asphalt binders are investigated. The asphalt modifiers used comprise crumb rubber (CR), styrene–butadiene–styrene (SBS) block copolymer and a blend or combination of CR and SBS (CCR). To investigate the modified asphalts microstructure, scanning electron microscopy is applied, while for assessing rheological properties at a wide range of temperature, Bending Beam Rheometry and Dynamic Shear Rheometry are employed. Ageing of asphalt during construction and under service conditions is simulated using the rolling thin film oven test and the Pressurised Ageing Vessel procedures. It is observed that ageing makes all three modified asphalts harder, increases their resistance to deformation under high temperatures, and decreases their fatigue and cracking resistance at low temperatures. Comparatively, the CR maintains its bond with the asphalt better than the SBS and the CR-modified asphalt exhibits lower stiffness and lower degree of ageing under cold temperature, while it shows the highest resistance to high-temperature deformation and fatigue. On the contrary, the SBS-modified asphalt exhibits the worst performance in practically every respect compared to the CR- and CCR-modified asphalts.

To study the effects of aging and freeze–thaw cycles on the low-temperature performance of styrene–butadiene–styrene (SBS)/crumb rubber (CR) composite modified asphalt mixtures. Digital image correlation (DIC) technology was combined with the three-point bending test to compare the strain field changes of SBS/crumb rubber composite modified asphalt mixture (SBS/CRMA) and SBS-modified asphalt mixture (SBSMA) during loading. A new index, linear strain density ($G_E$ ), is proposed to evaluate the crack resistance of asphalt mixtures; $G_E$ is the cumulative value of linear strain from loading to failure. In addition, using the bending beam rheometer (BBR) test and asphalt–aggregate contact angle test, the cracking characteristics of two kinds of asphalt mixtures under different conditions were analyzed from two aspects: low-temperature rheological properties, and adhesion and bond failure. The results indicated that the new index ($G_E$ ) and the macroscopic index ($F_E$ ) for evaluating the cracking characteristics of asphalt mixtures have a good correlation with BBR and contact angle test results. After aging and freeze–thaw cycles, the crack resistance and adhesion of the two modified asphalts decreased, decreasing the crack resistance of SBS/CRMA and SBSMA. Under the same conditions, the cracking resistance, aging resistance, and freeze–thaw resistance of SBS/CRMA were better than those of SBSMA. SBS/CRMA could better meet the demands of pavement materials in cold regions.

To investigate the influence of methyl styrene block copolymers (SMC) modifier on the fatigue performance and damage evolution of recycled asphalt mixture (RAM), RAM with reclaimed asphalt pavement (RAP) ratios of 30%, 50%, and 70% and 90# asphalt mixture were used for four-point bending fatigue test. The fatigue performance and damage evolution process of RAM were analyzed using the stiffness attenuation rate and the relative change rate of dissipated energy (RDEC). Linear amplitude sweep (LAS) tests and atomic force microscopy (AFM) tests were carried out for mixed asphalt in the mixture. The results show that under the same test conditions, with the increase of RAP content, the damage development of RAM is faster, and the fatigue damage resistance is worse. Compared with 90# asphalt mixture, RAM has better fatigue resistance. The fatigue property of the mixed asphalt is better than that of the 90# asphalt. With different RAP contents, the modulus changes of RAM and mixed asphalt are almost the same on macro and micro scales, which proves that the difference of fatigue performance between 90# asphalt mixture and RAM probably is caused by asphalt. A fatigue failure criterion based on the peak dissipation energy is proposed for the LAS test, and the applicability and accuracy of the criterion were proved by grey correlation analysis. Under this criterion, the power function model is introduced to describe the development process of fatigue damage in LAS test, which has high fitting reliability.