Study on multiple aging behaviors of high-viscosity asphalt based on the rheology approach

In order to simulate the actual aging conditions of high-viscosity asphalt (HVA), this study investigated the influence patterns of rheological properties under varying degrees of aging through multiple thermal-oxidative aging tests and ultraviolet (UV) aging tests. The rheological characteristics and microstructural features of high-viscosity asphalt subjected to multiple aging tests were analysed using Brookfield viscosity, dynamic shear rheometer (DSR), and bending beam rheometer (BBR) tests. The findings of the study demonstrate that as multiple short-term thermal-oxidative aging and UV aging intensify, the complex modulus, rutting factor, and strain recovery rate of both asphalts exhibit distinct upward trends. Multiple thermal-oxidative aging cycles have been shown to result in a significant increase, while UV aging has been observed to exhibit a gradual increase. Concurrently, the non-recoverable creep plasticity decreases, indicating that the ageing process enhances high-temperature stability but simultaneously compromises its viscoelasticity. Furthermore, an increase in the number of short-term thermal-oxidative aging cycles resulted in higher stiffness modulus, reduced creep rate, and significantly degraded low-temperature crack resistance in asphalt, with aging severity markedly exceeding that of UV aging. The results of the microstructural analysis demonstrated that the progressive accumulation of multiple aging processes resulted in the gradual decomposition of the HVA network structure. Combined infrared spectroscopy analysis confirmed that multiple thermal-oxidative aging caused rapid decomposition of butadiene, with a significantly higher rate of increase in the sulfoxide index compared to UV aging. This finding suggests that multiple thermal-oxidative aging is the primary cause of performance degradation in high-viscosity asphalt.