Research on the mechanism of low-temperature fracture behavior of phosphogypsum-waste engine oil-modified asphalt mixtures

This study aims to explore the impact of waste motor oil on modified asphalt mixtures based on phosphogypsum on their characteristics at low and medium temperatures. The asymmetric semi-circular bending test was used to assess modified asphalt mixtures with varying waste engine oil (WEO) dosages, and the applicability of different fracture codes to asphalt mixtures is discussed. The findings demonstrated that anhydrous calcium sulfate whiskers (ACSW) and WEO combined significantly increased the fracture toughness of asphalt mixtures at low temperatures. Compared to base asphalt mix, the combination of 2% WEO and 3% ACSW also demonstrated higher fracture toughness than the control group, and the WEO effectively made up for the reduction in low-temperature flexibility caused by the modification of ACSW. The fracture toughness of asphalt mixtures declined with increasing temperature. The inclusion of WEO increased the value of the crack resistance index, demonstrating its efficacy in fortifying asphalt mixes. Therefore, 3% ACSW and 2% WEO composite modified asphalt mixtures can be selected for construction in cold winter areas to improve the low-temperature cracking resistance of the pavement. The engineering experience criterion is in good agreement with the experimental data, the generalized maximum circumferential stress criterion has high accuracy in predicting the low temperature crack angle of modified asphalt mixtures, the MTS criterion has a bias, and Eq. (27) is suggested as a criterion for evaluating the low-temperature fracture characteristics in modified asphalt mixtures.