Analysis of Microstructure and Self-Healing Characteristics of Asphalt Under Freeze–Thaw Cycle

In order to study the self-healing behavior of asphalt under freeze–thaw cycles, a molecular dynamics (MD) model of asphalt was developed to simulate the self-healing behavior of 70# matrix asphalt after undergoing freeze–thaw cycles in four states: low-temperature freezing state (253k), room temperature state (298k), high-temperature melting state (333k), and refreezing state (253k). In this paper, the volume and shear modulus of asphalt after healing were used as evaluation indexes to evaluate the self-healing ability of asphalt after the freeze–thaw cycle. The self-healing ability of asphalt after freeze–thaw damage was verified by dynamic shear rheological experiment. The results show that as the number of freeze–thaw cycles increases, water enters the asphalt, and the molecular structure of the water changes during low-temperature freezing. As a result, the cohesive energy density of asphalt decreases, the free volume increases, the bulk modulus and shear modulus decrease, and the self-healing property of asphalt decreases; when asphalt transitions from a low-temperature frozen state to a high-temperature state, the freeze–thaw effect at high temperatures has a relatively small impact on the healing performance of asphalt; When asphalt transitions from a high-temperature melting state to a low-temperature freezing state, the freeze–thaw effect in the low-temperature state has a significant impact on the healing performance of asphalt. The increase in freeze–thaw cycles is more unfavorable for the healing of asphalt.