Evaluating Impact of Thermo-Oxidative and Ultraviolet Aging on Performance of Hot In-Place Recycled Asphalt Mixtures

Hot in-place recycling (HIR) is a sustainable pavement rehabilitation method. However, it is susceptible to aging processes that can compromise its mechanical properties and long-term performance. This study investigates the effects of thermo-oxidative (TO) and ultraviolet (UV) aging on HIR mixtures. Basic performance tests were conducted on the aggregate gradation, moisture content, and asphalt content of the reclaimed asphalt pavement (RAP) to assess the aging level. Simulations of long-term and short-term oxidative aging of the HIR mixture, along with 12 months of UV irradiation, were performed to evaluate its high-temperature stability, low-temperature crack resistance, and water stability. The Verhulst model was employed to establish a predictive equation for performance attenuation under UV aging. To quantify the photoaging effect, indicators for UV aging degree were proposed to characterize the road performance of the HIR mixture, including the aging rate and the aging residual index. Results indicate that the improvement in high-temperature performance after aging is limited, but cracking resistance decreases substantially. Notably, the flexural tensile strain was reduced by 129.25 με for 10 years of TO aging compared to 12 months of UV exposure, underscoring the importance of considering environmental factors in performance predictions. This study emphasizes the need for enhanced aging mitigation strategies to improve the sustainability and reliability of HIR mixtures in practical applications.