Enhancing fatigue resistance and low-temperature performance of asphalt pavements using antioxidant additives

Ageing results in significant performance deterioration of asphalt, especially in relation to its fatigue and low-temperature performance. This performance deterioration can theoretically be lowered by incorporating antioxidants in asphalt mixtures. Although there are several promising studies that have shown the potential efficacy of antioxidants such as zinc diethyldithiocarbamate (ZDC), no work has comprehensively evaluated its performance. In this regard, ZDC was employed to evaluate its effect as an antioxidant to slow down the ageing related performance deterioration of bitumen and asphalt mixtures. Both ZDC-modified (3% and 5%) and unmodified bitumen and asphalt mixtures were subjected to short-term and long-term ageing. Afterwards, linear amplitude sweep (LAS) tests and low-temperature frequency sweep tests were carried out on the bitumen samples using a dynamic shear rheometer (DSR). Four-point bending (4PB) fatigue tests were carried out at 25 °C, and indirect tensile asphalt cracking tests (IDEAL-CT) were carried out at 25 °C and −10 °C on the various asphalt mixtures. It was seen that properties of long-term aged bitumen and asphalt mixtures measured at low temperature and intermediate temperature could be improved by 13–69% for mixtures and 1–44% for bitumen with the addition of ZDC, compared to the unmodified samples. The ageing-mitigation efficiency of ZDC was more pronounced for the low-temperature performance-based metrics since its performance deterioration rate was significantly reduced. Overall, a comprehensive performance evaluation of the effectiveness of antioxidants at different scales provided robust evidence for the potential extension of this technology to field trials and application.