Study on the Adhesion Performance of Asphalt-Calcium Silicate Hydrate Gel Interface in Semi-Flexible Pavement Materials Based on Molecular Dynamics

The interface between an asphalt binder and a calcium silicate hydrate (C-S-H) gel is a weak point of semi-flexible pavement material. In this study, the adhesion performance of asphalt-C-S-H gel interface in semi-flexible pavements at a molecular scale has been investigated. Molecular dynamics (MD) simulations were applied to establish three asphalt binders: 70# asphalt binder (the penetration is 70 mm), PG76-22 modified asphalt binder (a kind of asphalt binder that can adapt to the highest temperature of 76 °C and the lowest temperature of −22 °C), and S-HV asphalt binder (super high viscosity). The effects of different temperatures and SBS modifier contents on interfacial adhesion were explored. The obtained results showed that temperature variations had little effect on the adhesion work of the asphalt-C-S-H gel interface. It was also found that by increasing the content of SBS modifier, the adhesion work of the asphalt-C-S-H gel interface was increased. The molecular weight of each component was found to be an important factor affecting its molecular diffusion rate. The addition of SBS modifier could regulate the adsorption of aromatics by C-S-H gel in the four components of asphalt binder and improve the adsorption of resins by C-S-H gel.