Rheological Performance of Asphalt Modified with Coal–Oil Co-Processing Residue

To address high-temperature stability demands and promote resource utilization, this study investigates coal–oil co-processing residue (COCR) as an asphalt modifier. Penetration, softening point, ductility, rheological, and aging/storage evaluations were conducted on asphalt with varying COCR contents. Modification mechanisms were analyzed using FTIR, GPC, and SARA fractionation. The results revealed that COCR significantly enhanced high-temperature performance while slightly reducing low-temperature performance, showing good storage stability. At a 10% COCR content, the rutting factors of 70# and 90# asphalt increased by 44.8% and 46.2%, respectively, at 52 °C. Increased asphaltene content indicated that COCR reinforced the colloidal structure, thus improving the deformation resistance. At a 15% COCR content in mixture, the dynamic stability of asphalt mixtures increased by approximately 53.5% and 59.7% for 70# and 90# base asphalt, respectively. Considering overall performance balance, 10% COCR in 90# base asphalt would be recommended for regions with hot summers and warm winters.