Interfacial adhesion between recycled asphalt binder and aggregates considering aggregate surface anisotropy: A molecular dynamics simulation

Abstract

In this study, the interfacial adhesion properties between reclaimed asphalt binder and aggregates were investigated using the molecular dynamics (MD) simulation method. Surface free energy theory (SFE) was applied to analyze the changes in adhesion properties before and after asphalt binder reclamation. The asphalt binder model was constructed from the four components of asphalt binder and validation of the model was carried out. The five common crystalline surfaces of two types of aggregates were sliced. The asphalt binder-aggregate interface was modelled to investigate the effect of the anisotropic surface of the aggregates on the adhesion of the asphalt binder. The adhesion properties of the recycled asphalt binder-aggregate interface were characterized from micro and multiscale simulations using the work of adhesion and relative concentration. Results showed that the rejuvenators enhanced the adhesive properties of the asphalt binder by rebalancing the components and adding the light components lost from aging. Surface anisotropy had significant effect on the bonding at the asphalt binder-aggregate interface because α-SiO2 bonded to acid surfaces less strongly than CaCO3 linked to alkali surfaces. Van der Waals forces dominated the adhesion energy in the α-SiO2-asphalt binder interfacial model system. In the CaCO3-asphalt-binder interface model system, the combined effect of van der Waals forces and the CaCO3 surface void reduced the adhesion energy of the aggregate surface to the asphalt binder.