Using Crude Vegetable-Based Oils and Antioxidants to Improve the Performance of Asphalt Binders

Vegetable-based oils have been the center of attention in research on reclaimed asphalt pavement in recent years, since they are sustainable sources of recycling agents (RAs). However, there could be concern about the long-term performance and the resistance to moisture damage of asphalt binders modified by these oils. Crude corn oil (CO) and crude soybean oil (SO) have been studied as RAs for aged asphalt binder to improve their physical and rheological performances. It is hypothesized that the efficacy of vegetable-based RAs can be improved by the simultaneous addition of these RAs and an antioxidant to the binder. This study evaluates the synergy between vegetable-based RAs (i.e., CO and SO) and two antioxidants (zinc diethyldithiocarbamate [ZnDEC] and dilauryl thiodipropionate [DLTDP]) using physical and rheological characterization at high, ambient, and sub-zero temperatures. The results show that CO and SO improved the high-temperature rutting and mid-temperature cracking index of asphalt binders while worsening their low-temperature cracking index. The efficacy of CO and SO was improved by the simultaneous addition of ZnDEC. However, the asphalt binders modified by CO or SO with ZnDEC had lower resistance to moisture damage. The results also show that the simultaneous addition of DLTDP and CO or SO did not improve the efficacy of CO and SO and even resulted in inferior asphalt binders.