Decay pattern of self-healing temperature susceptibility of bitumens at various ageing states. (21st March 2022) - Sun, Guoqiang
Graphical abstract: Highlights: Decay pattern of self-healing temperature susceptibility of bitumens at various ageing states is examined. Self-healing rate parabola evolution with temperature of bitumen is related to the frequent phase transition. Superposition impacts of temperature and ageing on phase structures elicit the healing transition phenomena. All-weather ageing causes more serious impact on self-healing temperature susceptibility than long-term ageing. RA bitumen undergoes smaller ageing impact on self-healing temperature susceptibility than pure bitumen. Abstract: Understanding the evolution law of the self-healing ability of bitumen under actual service environment is conductive to optimizing the design of self-healing bituminous pavement, while the changing temperatures and variety of ageing states complicate this issue. In this study, the decay pattern of self-healing temperature susceptibility of pure bitumen and rock-asphalt (RA) modified bitumen at the simulated ageing states of thermal oxidation and all-weather is analyzed by the dynamic shear rheometer based fatigue-healing-fatigue experiment. Through the thin layer chromatography, differential scanning calorimeter and rheological characterizations, the chemical composition, colloidal stability and macro phase transition (PT) behavior of bitumens with various ageing levels are examined. Results show that the self-healing rate parabola evolution with temperature of bitumen has to do with its frequent PT behaviors. The shift of self-healing curves and the appearance of healing inert temperature zone are the results of the growth of heavy components and decays of colloidal structure and phase structure caused by ageing. Notably, the superposition impacts of temperature and ageing on bitumen phase structures elicit the healing transition phenomena in the viscoelastic zone and viscous flow zone. Moreover, the multi-scale analysis reveals that the decay of self-healing temperature susceptibility with ageing is consistent with the deterioration tendency of the macro PT property, chemical composition and colloidal stability. Especially, all-weather ageing causes more serious impact on the self-healing temperature susceptibility of bitumens than thermal oxidative long-term ageing. RA bitumen with greater ageing resistance undergoes smaller ageing impact on self-healing temperature susceptibility than pure bitumen.