Molecular-Scale Analysis of the Interfacial Adhesion Behavior Between Asphalt Binder and Aggregates with Distinct Chemical Compositions

The asphalt–aggregate interface is the weakest yet most critical component in asphalt mixtures, directly governing the pavement performance. In this study, the interfacial adhesion behavior between asphalt binder and aggregates with different chemical compositions (Al2O3, CaCO3, and SiO2) was investigated under varying conditions using molecular dynamics simulations. The effects of aggregate composition, environmental temperature, and asphalt aging were quantitatively assessed using key metrics, specifically interfacial adhesion energy and molecular concentration profiles near the interface. Results demonstrated that the chemical composition of aggregates fundamentally governed the asphalt–aggregate interfacial adhesion strength. Al2O3 exhibited the highest interfacial adhesion strength with asphalt binder, followed by CaCO3, with SiO2 showing the lowest strength. In terms of asphalt fractions, resins and aromatics were found to dominate the interfacial adhesion behavior due to their high molecular concentrations at the interface, with the contribution ranking as: resin > aromatic > saturate > asphaltene. The interfacial adhesion strength exhibited a non-monotonic temperature dependence. It increased with rising temperature and reached a peak value at 25–45 °C, and therefore declined because of excessive softening of asphalt binder. Furthermore, oxidative aging enhanced interfacial adhesion through strengthened electrostatic interactions. These molecular-level insights provide a fundamental understanding crucial for optimizing asphalt mixture design and enhancing pavement durability.