Surface-Roughness-Induced Control of the Interfacial Failure Mode and Bonding Strength: Atomistic Case Study in an Asphalt–Aggregate System

The surface roughness prior to adhesive bonding plays an important role in enhancing the durability of composite materials. To obtain deep insight into the effect of aggregate surface roughness on the interfacial properties of the asphalt–aggregate system, molecular dynamics simulations were carried out. Different surface nanostructure patterns, including groove, grid, and pillar, were generated with predefined roughness ratios in both acidic mineral (quartz) and weak alkali mineral (calcite) models. The influences of surface nanostructure on interfacial interaction energy, tensile bond strength, and the interlocking effect were investigated. In general, the van der Waals energy dominates the interaction energy between asphalt and aggregate surfaces at a low roughness ratio, whereas electrostatic interaction dominates the interaction energy in surfaces at a high roughness ratio because of the unsaturated atoms introduced by the surface nanostructure. Moreover, the presence of surface nanostructures results in the adsorption of more asphalt chains, strengthening the interlocking effect. By increasing surface roughness, the interfacial failure mode under tensile stress gradually transfers from adhesive failure to cohesive failure. In light of the aforementioned observation, a schematic illustration of the bond strength along with surface roughness was obtained.