Failure mechanisms at asphalt/aggregate interfaces: coupled effects of interfacial heat conduction and molecular diffusion

The interfacial adhesion between asphalt and aggregate is critical to pavement performance, yet the dynamic visualisation of molecular detachment processes remains insufficiently explored. This study combines pull-off tests and molecular dynamics simulations to develop a model visualising asphalt molecule desorption from aggregate surfaces. A multiple regression model quantitatively analyses relationships among the interfacial failure force, critical energy, oxide composition and temperature. The key findings include: (1) Highly polar oxides (CaO, MgO) restrict molecular diffusion with coefficients as low as 1.2 × 10⁻⁵ cm²/s and activation energies of 34.8 kJ/mol, while low-polarity oxides (Fe₂O₃, SiO₂) exhibit lower diffusion barriers (15.6 kJ/mol), resulting in faster diffusion. (2) High-thermal-conductivity oxides (MgO at 2.4 W/m K and Al₂O₃ at 2.1 W/m K) facilitate rapid heat transfer, enhancing diffusion-thermal conduction coupling (r = 0.87) compared to low conductivity oxides (r = 0.42). (3) Elevated temperatures weaken asphalt–oxide interactions, with interfacial energy decreasing by 200 kcal/mol for Al₂O₃ between 0 °C and 40 °C. Asphalt residue is higher (~10%) on highly polar oxide surfaces. (4) Critical interfacial energy values range from -1300 kcal/mol (Al₂O₃) to −300 kcal/mol (CaCO₃), with highly polar oxides showing greater temperature sensitivity. (5) Temperature significantly affects the interfacial pull-off strength, decreasing peak values from 1.4 MPa at 0 °C to 0.4 MPa at 40 °C. For every 1 °C increase, the limestone interfacial failure force decreases by approximately 112.37 N, while granite decreases by 119.33 N. This study provides a framework for visualising asphalt molecular pulling and uncovering mechanisms underlying interfacial failure.