Molecular interaction of Asphalt-Aggregate interface modified by silane coupling agents at dry and wet conditions

This study investigated interfacial behavior of asphalt-aggregate system modified by silane coupling agents (SCA). Molecular dynamics (MD) were used to simulate the interface between asphalt binder and silica grafted with three SCAs with different functional groups. At dry condition, the transition zone thickness and contact angle between asphalt binder and modified aggregate surfaces were compared. At wet condition, the effects of SCAs on interaction energy and hydrogen bond were analyzed. The simulated results are in good agreement with experimental measurements reported in the literature. It was found that the SCA modification could improve the adhesion between asphalt and aggregate at both dry and wet conditions. The thicker transition zone between asphalt and aggregate after SCA modification could enhance the compatibility and improve the force transfer between asphalt and aggregate. In addition, the wettability of asphalt binder on the SCA-modified aggregate surface was found better from the simulated contact angle. The grafted SCA on aggregate surface increased the resistance of asphalt-aggregate interface to moisture damage through increased interaction energy and less potential of hydrogen bonds. Although all three types of SCAs had positive benefits on interfacial bonding of asphalt-aggregate systems, the SLA with amino group showed superior performance.