Mechanisms of the Interaction Behaviors of Asphalt Mastic–Mineral Interface Structures

The interfacial structure between adhesive and mineral constitutes a critical determinant of asphalt pavement durability and stability. Current research on interfacial interaction (adhesion and stripping) behavior, derived from the asphalt binder–mineral interfacial system, demonstrates systematic biases from actual asphalt mixtures where asphalt mastic serves as the functional adhesive medium. This study investigated two sets of two-phase interface structures: asphalt mastic–mineral and asphalt binder–mineral. Through systematic application of improved stripping rate test, pull-off tensile strength (POTS) characterization, and surface energy theory, differences in the interaction behavior between two sets of two-phase interface structures were identified, and the underlying mechanisms responsible for these differences were elucidated. The results demonstrated that the evaluation of interfacial properties using asphalt binder as the adhesive in asphalt mixtures exhibits significant systematic bias. Significant discrepancies (up to 58.7%) were observed in interfacial properties (stripping rate, POTS, and surface energy parameters) between the two sets of structures. Notably, the governing mechanisms by which hydrodynamic conditioning, asphalt modification, and mineral lithology influence the binder–mineral interface remain applicable to the mastic–mineral system. Crucially, the distinct interaction behaviors between these two interfacial systems arise primarily from filler incorporation, which exerts dual effects: positively, fillers induce colloidal structure reorganization in asphalt, enhancing interfacial intermolecular forces and adhesion property at the interface; negatively, fillers simultaneously amplify localized stress concentration and elevate water affinity within the interface, thereby reducing POTS and water-induced damage resistance. This study elucidates the differences in interaction mechanisms between mastic–mineral and binder–mineral interfaces. The findings provide insights into the interaction behaviors of asphalt mixture interface structure.