Study of cohesion and adhesion properties of asphalt concrete with molecular dynamics simulation

Abstract

The objectives of this study is to develop a molecular modeling approach for studying cohesive and adhesive properties of asphalt concrete and evaluate the accuracy of modeling through comparisons with experimental data. Fully atomistic models were built for molecular dynamics (MD) simulation considering two representative asphalt models and two types of aggregate mineral. MD simulations were performed to study thermodynamic and cohesive properties of asphalt binder, such as density, solubility parameter, cohesive energy density, and surface free energy. The adhesion properties were investigated by calculating the interaction energy and the work of adhesion at asphalt–aggregate interface for the first time. The bond energy parameters in dry and wet conditions were used to evaluate moisture sensitivity of interface adhesion. The results show that van der Waals force plays critical role for cohesive properties of asphalt binder; while the adhesion bonding between asphalt to aggregate is largely dependent on the type of aggregate mineral (silica or calcite) in both dry and wet surface conditions. The effect of asphalt type was found significant for the adhesion between asphalt and silica at the relatively small moisture content. The simulation results agree well with experimental measurements reported in the literature. This work illustrates MD can help in understanding fundamental chemo-mechanics relationship of asphalt concrete at an atomistic scale, which can be used as a useful tool for material design and performance prediction.