Shear Mechanical Behavior of Virgin and Aged Asphalt-Aggregate Interfaces

This study investigated the shear strength and failure mechanism of the asphalt-aggregate interface with both virgin and aged asphalt based on reclaimed asphalt mixtures. Test devices and methodology were developed to consider factors such as the degree of blending (DoB), asphalt film thickness, aggregate surface roughness, and loading angles, while interfacial mechanics, fracture mechanics, and viscoelastic mechanics were used to evaluate the interfacial shear performance. At the same time, the influencing factors and variation characteristics of multiangle shear tests were passed. A gray correlation model was constructed to explore the relationships between these influencing factors and interface properties. The results showed that the interfacial shear stiffness increased with DoB for 60° and 70° loading angles, with average increases of 10.4% and 16.9%. The peak value of shear stress was affected by the loading angle, with an average increase in peak shear stress of 18.8% at 50° loading angle, 26.3% at 60°, and 44.0% at 70°. The asphalt film thickness affected the interfacial properties, and the peak displacements of the shear test results for the three asphalt film thickness specimens of 15±3 μm, 70±5 μm, and 140±10 μm increased sequentially to 0.4130 mm, 0.5787 mm, and 0.7177 mm, respectively. The gray correlation rankings of the degree of influence of each factor on the shear fracture energy were roughness (0.8753) > DoB (0.8461) > shear-compression ratio (0.8063) > asphalt film thickness (0.7400). These rankings further refined the understanding of the interfacial shear strength mechanism. The findings provided valuable insights for improving evaluation methods of asphalt-aggregate interface properties with aged and virgin asphalt.