Effects of waste engine oil and cooking oil on the chemical, rheological, and permanent deformation of bitumen and asphalt mixtures

In recent decades, the production of waste engine oil (WEO) and waste cooking oil (WCO) has risen, primarily attributed to shifts in human lifestyles and advancements within the automotive industry. In light of growing environmental concerns and efforts to enhance asphalt mixtures, researchers have investigated integrating these waste materials into traditional bitumen formulations. Thus, this study examines the laboratory investigation of varying proportions of WCO and WEO on the rejuvenation effect, including chemical, rheological, performance grading (PG), and resistance to permanent deformation of asphalt. A total of 7 blends were prepared, consisting of the base bitumen and different proportions of WEO (7%, 10%, and 13%) and WCO (3%, 6%, and 9%) by weight of bitumen. The rheological properties of high-temperature PG bitumen and the rutting depth of asphalt mixtures were evaluated using the Dynamic Shear Rheometer and Cooper Wheel Tracker Test. The research outcomes confirm that incorporating an appropriate dosage of WCO and WEO meets the criteria for conventional bitumen physical properties. Furthermore, the lower dosage of the WCO blend exhibited adequate tensile properties, thermal susceptibility, PG, and resistance to permanent deformation compared to WEO blends. Meanwhile, introducing WCO and WEO does not trigger additional chemical changes. However, excessive incorporation of waste oil can result in an undesirable reduction in the bitumen phase angle, thereby prolonging the construction timeframe. Therefore, based on rigorous statistical analyses, it is recommended that WCO and WEO be incorporated at dosages of 3% and 7%, respectively. This study highlights the potential of recycling WEO and WCO by incorporating them into bitumen for use in the asphalt pavement sector, thereby expanding the utilization of waste oils.