Molecular Mechanisms of Interfacial Adhesion Between Asphalt and Mineral Aggregates Based on Molecular Dynamics and Density Functional Theory

Asphalt mixtures often suffer from weak adhesion between asphalt and aggregates, leading to moisture damage and pavement deterioration. This study investigates the impact of molecular structural characteristics and functional groups on the interfacial adhesion between asphalt and mineral aggregates using molecular dynamics and density functional theory (DFT). Various asphalt molecules and functional groups were analyzed in relation to their interaction with quartz and calcite, as well as the interaction energies and contact angles between three types of asphalt and aggregates. The results show that van der Waals interactions are strongest with aromatic rings and aliphatic chains because of the large contact area, while the limited deformability of naphthenic rings and adjacent long side chains reduces their contact area with aggregates. In asphalt molecules, the negative electrostatic potential (ESP) around benzene carbon and heteroatoms attracts acidic sites on aggregates, while the positive ESP around hydrogen atoms attracts basic sites on aggregates. Electrostatic interactions are enhanced by significant differences between positive and negative ESP values, with carboxyl, hydroxyl, and sulfoxide groups exhibiting the strongest effects. The asphalt with a higher aromatic carbon ratio, lower naphthenic carbon ratio, and higher oxygen content demonstrates superior adhesion performance, which can be optimized through these compositional adjustments.