Molecular-Atomic Scale Insight on Asphalt–Aggregate Interface Interaction and Seawater Erosion with Different Aging-Resistant Materials Using Molecular Dynamics Simulations

The durability of asphalt pavement in coastal regions has been a widely discussed topic due to the coupling effect of complex climate environment and seawater erosion. Aging-resistant materials (ARMs) significantly enhance the environment resistance of high-viscosity modified asphalt (HiMA), but their impact on the asphalt–aggregate interface interaction and seawater erosion-induced failure remains unclear. In this study, molecular dynamics simulation was employed to investigate the molecular-atomic scale interactions at the HiMA–aggregate interface and the evolution mechanism of seawater erosion with different ARMs. An analysis of the interface adhesion mechanism in different aging-resistant HiMAs was conducted based on molecular polarity, component distribution, and nanostructure evolution. The seawater erosion mechanism at the interface and the impact of ARMs were further investigated. The research indicates that ARMs interact extensively with asphalt components and polymers, altering the molecular spatial arrangement and nanostructure characteristics of HiMA at the aggregate interface. ARMs promote the free volume and diffusion ability of asphalt molecules and accelerate their aggregation at the aggregate interface. With the addition of ARMs, highly polar asphaltene and resin molecules intensify their movement toward the aggregate interface, exhibiting directional adsorption with aggregates. Simultaneously, weakly polar polymer and light components detach from the aggregate interface, vacating the active adsorption sites of aggregates. Consequently, ARMs enhance the interaction at the HiMA–aggregate interface. Seawater erosion induces water movement pathways at the aggregate interface, leading to the intrusion of ionic solutions into asphalt molecules and the occupation of aggregate active sites, thereby diminishing the direct interaction between polar asphalt components and aggregate. The addition of ARMs reduces the deterioration of asphalt nanostructure at the interface and the ion dissolution of asphalt polar components under seawater erosion, thus improving the interaction at the HiMA–aggregate interface. Light shielding material exhibits the most effective enhancement of the asphalt–aggregate interface stability under seawater erosion.