Chloride Salt Erosion of Asphalt Based on Adhesion, Surface Characteristics, and Microsurface Energy

Abstract

To comprehensively investigate the impact of chloride salt erosion on the multiscale bonding behavior between asphalt and aggregate, atomic force microscopy (AFM) and pull-off tests were employed. A thorough study was conducted on the microsurface morphology, nanoscale surface roughness, microsurface energy, and macro pull-off strength between asphalt and aggregate under different chloride salt concentrations. Furthermore, the relationship between the microscopic structural characteristics of asphalt and macroscopic bonding performance was analyzed. The results revealed that, except for the crumb rubber (CR) modified asphalt, the surface of asphalt exhibited an alternation of peaks and valleys forming a beelike structure both before and after chloride salt erosion. The erosion caused the reaggregation of asphalt surface particles, resulting in prominent nano-protrusions and white spots, thereby increasing the surface height and roughness of asphalt. In chloride salt solutions, the infiltration of ions and water molecules into the asphalt may lead to irregular depressions and pits on the surface, consequently reducing the surface energy of the asphalt. This further diminished the effective contact area between the asphalt and aggregates, forming microscopic voids and subsequently weakening the bonding strength at the asphalt-aggregate interface.