Effect of water molecular behavior on adhesion properties of asphalt-aggregate interface

Abstract

Asphalt-aggregate interfaces are prone to damage by moisture, leading to a decrease in interfacial adhesion. However, the precise mechanism governing water molecule behavior at these interfaces remains poorly understood. To address this, we employed molecular dynamics simulation to investigate the interaction of water molecules with aggregates and asphalts, as well as the adhesion properties of the interfaces. Simulations revealed that thin water films formed on SiO2, CaO, and MgO surfaces, while water molecules aggregated on Al2O3, Fe2O3, and CaCO3 surfaces due to hydrogen bonding and physical adsorption. Aged asphalt would adsorb more water due to more hydrogen bonds of water molecules with sulfoxide and carbonyl. Furthermore, the adhesion between asphalt and aggregates followed the order: alkaline aggregates > neutral aggregates > acid aggregates under dry conditions. However, in moist environments, the adhesion between asphalt and alkaline aggregates decreased sharply due to stable occupancy of water molecules in the interfacial gap, limiting the interaction between asphalt and aggregates. Additionally, the adhesion of interfaces decreased with increasing temperature due to higher mobility of water molecules, which pushed asphalt molecules further away from the aggregate layer. Conclusively, the molecular behavior of water is the key cause of adhesive damage at asphalt-aggregate interface under moisture condition. Type of aggregate, aging state of asphalt, water content, and temperature all affected the water molecular behavior, ultimately affecting interfacial adhesion.