Multi-scale analysis of virgin/aged/recycled asphalt self-healing performance based on molecular simulation and micro-macro tests

Conventional macro-micro experiments have not fully elucidated the thermal self-healing mechanism of virgin, aged, and recycled asphalt at the molecular level at different temperatures. Molecular dynamics and macro-micro experiments were used to investigate the multi-scale mechanism of thermal self-healing of nano-cracks in three asphalt types. The molecular characteristics (concentration, energy changes, and molecular diffusion properties) of the three asphalt types were simulated during self-healing using molecular dynamics simulations Macro-micro experimental tests were conducted to validate the simulation results. The self-healing process was analyzed at multiple scales, and correlation analysis between the self-healing parameters and the macroscopic healing characteristics was performed at nano- and microscopic scales. The results showed that the relative concentration increased significantly from 0 mol/L to 0.6 mol/L in the 60–80 Å range during the long-distance self-healing phase (0–40 ps), promoting the rapid reorganization of molecules around cracks and the formation of self-healing networks. The van der Waals forces were the dominant forces affecting self-healing, and the transition from repulsive to attractive forces promoted the self-healing of cracks. This study clarifies the thermal self-healing mechanism of asphalt cracks at multiple scales, ensuring the sustainable use of asphalt materials.