Study on interfacial adhesion properties of different coarse aggregate asphalt mixtures: Experiment and molecular simulation

The physical and mechanical properties of asphalt mixtures are predominantly influenced by the interfacial adhesion properties between the aggregate and asphalt. Elucidating the mechanism of interfacial adhesion is crucial in comprehending the performance enhancement of recycled aggregate asphalt mixtures. Therefore, this paper uses a certain concentration of silane coupling agent (SCA) solution to strengthen the surface of recycled coarse aggregate (RCA), modifies the interface between the aggregate and asphalt, and determines the optimal aggregate substitution rate to prepare recycled aggregate asphalt mixture. The performance of the prepared mixture is tested through a series of macroscopic experimental methods such as Marshall, wheel tracking test and low temperature small beam bending test. It establishes an aggregate asphalt interface model before and after SCA modification using molecular dynamics software, simulate asphalt contact angle tests, and calculate the relative concentration of asphalt molecules, radial distribution function, and interface energy to characterize the modification effect of SCA. The test results show that the performance of the mixture prepared with 5% concentration of SCA and 75% aggregate substitution rate meets the pavement use standards. The simulation results show that the hydrolyzed SCA reacts with the aggregate asphalt through two different functional groups, attracting a large amount of heavy asphalt components to approach the aggregate surface and form chemical bonds, thereby improving its adhesion performance by 61.86%. The interface energy between the modified RCA and asphalt is calculated to be 51.63 mJ/m 2 based on the contact angle simulation.