Study of diffusion characteristics of asphalt–aggregate interface with molecular dynamics simulation

Abstract

ABSTRACT The generation and development of interfacial adhesion properties between the asphalt binder and the aggregate surface is difficult to explain at the microscale through experiments. In this research, the models of asphalt–aggregate interface were constructed using four-component molecules of asphalt overlaid on two typical minerals of aggregate, respectively. Then the diffusion law of asphalt on the surface of aggregates and interfacial behaviour at microscale were analysed through the calculations of the diffusion coefficient, the Z-axis direction relative concentration and the dipole moment. Moreover, the distribution characteristics of four components of asphalt in the Z-axis direction in the asphalt–aggregate interface were analysed. The results showed that the increase in temperature could benefit the diffusion of asphalt on the aggregate surface and promote the adhesion between asphalt and aggregate. From the energetics perspective, the Van der Waals force between molecules was found to be the main factor driving the molecular movement during the diffusion process of asphalt on the surface of aggregate. Based on the molecular orientation theory, it was concluded that the polarity of asphalt and aggregate is the fundamental cause of adsorption of asphalt on the aggregate surface, and asphaltene and gelatine play an important role in adhesion of asphalt to aggregate.