Evaluation of the interface adhesion mechanism between SBS asphalt and aggregates under UV aging through molecular dynamics

Abstract

The bonding characteristics between asphalt and aggregates have an important role in influencing the strength of asphalt mixtures. To clarify the bonding mechanism at the interface between SBS asphalt and aggregates under UV aging conditions, this research developed molecular models of the interface between SBS asphalt and representative aggregates including quartz (granite), augite (basalt), and calcite (limestone). Subsequently, dynamic simulations were performed on the interface models to assess the adhesive properties. Adhesion work was employed to assess the interfacial adhesion performance between SBS-modified asphalt and various types of aggregates. The results demonstrated that SBS asphalt exhibited significantly higher adhesive work with alkaline aggregates, following the order of limestone > basalt > granite in terms of adhesive strength. The dominant contributor to adhesive work was van der Waals interactions, with electrostatic interactions playing a crucial role in influencing variations in adhesive work among different aggregates. After the aging-induced fracture of SBS materials, there was a noticeable increase in the gap between them and the aggregates, resulting in a significant reduction in the adhesion effectiveness between SBS and aggregates. Aged asphaltene and colloid exhibited heightened polarity, resulting in enhanced electrostatic interactions between asphalt and aggregates, thus reducing adsorption distances and elevating adhesive work. This research provides comprehensive evaluation of the bonding mechanism between asphalt and aggregate under UV aging conditions at the molecular level, and provides guidance for the design of durable asphalt pavements.