Self-healing characteristics of asphalt during oxidative ageing evolution from the molecular scale

The asphalts were aged at different ageing levels to simulate oxidative ageing evolution. The changes in the four components and chemical functional groups of the asphalts at different ageing stages were analysed, and their corresponding asphalt molecular models were established. Then, the self-healing molecular models during ageing evolution were established based on the asphalt molecular models. The self-healing characteristics of the virgin, fast-aging, slow-aging and full-aging stages were studied using the density, radial distribution function (RDF), energy, relative concentration and diffusion coefficients. The results show that the characteristic peak values of RDF curves at the same distance increase with ageing. The bond energy increases less in the fast-ageing stage but greatly in the slow-ageing stage, due to limited sulphur atoms in the asphalt molecule, while the non-bond energy increases greatly in the fast-ageing stage, and less in the slow-ageing stage, due to the stronger polarity of sulphoxide. The relative concentration of saturate changes most, and asphaltene changes less, aromatic and resins change evenly during ageing. The decrease rate of the diffusion coefficient of saturate, aromatic, resin and asphaltene is 12.6%, 11.12%, 10.42% and 9.2% in the fast-ageing stage and 0.62%, 0.60%, 0.55% and 0.62% in the slow-ageing stage.