Multi-scale method for investigating the mechanism of water effect on asphalt/aggregate interface adhesion and the enhancement role of oxides

Water infiltration at asphalt-aggregate interfaces compromises pavement structural stability, increasing maintenance requirements and resource consumption. This study employs a multi-scale approach integrating surface energy theory, fluorescence tracer method, and molecular dynamics simulation to investigate water-induced adhesion degradation mechanisms. Results show significant variability in asphalt stripping rates dependent on aggregate mineralogy and type: limestone surfaces exhibited rates below 10 % with 70# asphalt, while granite surfaces reached 43.01 %. With 90# asphalt, granite and basalt surfaces showed 31.42 % and 30.81 % stripping rates, respectively. SBR-modified asphalt maintained stripping rates below 10 % on limestone, diabase, and quartzite surfaces. SBS-modified asphalt demonstrated superior water resistance, with stripping rates below 10 % for most aggregates due to its block copolymer structure, enhancing elasticity and adhesion. Molecular dynamics simulations revealed that water forms a hydration layer on aggregate surfaces, causing asphalt molecules to detach and reaggregate. This effect is more pronounced with acidic aggregates (SiO2) than alkaline aggregates (CaCO3), as water molecules form hydrogen bonds with hydroxyl groups on SiO2 surfaces, occupying asphalt adsorption sites. Binding energies for asphalt on CaCO3 (−65.3 kcal/mol) were significantly stronger than on SiO2 (−42.8 kcal/mol). Pearson correlation analysis confirmed strong relationships between stripping work (from surface energy theory), experimentally measured stripping rates, and interfacial energy weakening (from molecular simulation), validating the multi-scale approach. These findings provide fundamental understanding of water-induced failure mechanisms at asphalt-aggregate interfaces, guiding the development of more durable pavement materials that extend service life and promote resource conservation.