Interfacial interaction behavior between asphalt and solid waste fillers: Atomic-scale debonding mechanism and experimental investigation

Understanding the interfacial interaction behavior between asphalt and solid waste fillers is critical for developing low-carbon pavements. In this research, five types of solid wastes, including iron tailings (IT), waste cement, steel slag (SS), desulfurization gypsum, and blast furnace slag, were selected as fillers of asphalt mixture, and their interfacial interaction behaviors with asphalt were investigated through the molecular dynamic (MD) simulation and experimental characterization. Compared to conventional mineral fillers, solid waste fillers demonstrate enhanced interactions and adhesion with asphalt, especially SS and IT, leading to asphalt mastic with higher resistance to cohesive failure, greater adhesion energy, and improved bonding strength at the macroscopic scale. The mineralogical characteristics of the fillers provide a reliable molecular-scale explanation for these advantages, as the rock-forming minerals in solid waste fillers demonstrate substantially higher peak stress and fracture energy when interacting with asphalt molecules. Molecular models of the asphalt–filler interface under tensile loading exhibit a consistent cracking pattern: as the tensile rate decreases, interfacial failure gradually shifts from adhesive to cohesive cracking, and the interface models corresponding to solid waste fillers show greater resistance to adhesive failure. These findings advance insights into interfacial interactions of asphalt-filler, thereby promoting sustainable, low-carbon pavement development.