This research explores the effects of using waste engine oil bottom on physical, rheological properties and composite modification mechanism of SBS-modified asphalt. The SBS asphalt binder was modified by WEOB with different concentrations (2, 4, and 6wt). The GC-MS and FTIR spectrometry were conducted to evaluate the chemical compositions of WEOB- and WEOB-modified asphalt. RV, DSR, and BBR were tested to evaluate high- and low-temperature pavement performance. Fluorescence microscope (FM) test, bar thin layer chromatograph (BTLC) test, and AFM test were performed to evaluate the micromorphologies and modification mechanism. The test results showed that a new characteristic peak appeared in the infrared spectrum of the WEOB-modified SBS asphalt, indicating a chemical reaction in the modification process. Incorporation of WEOB improves both the high-temperature and low-temperature properties of the SBS asphalt binder. It was confirmed that with the increase of WEOB concentration, the content of colloid gradually increases, which promotes the swelling and compaction of SBS polymer network structure. Furthermore, WEOB promotes the polarity of SBS and forms graft product MAH-g-SBS with asphalt, thus inhibiting the thermal movement of asphalt molecules. On the contrary, light components have a good correlation with the surface roughness of modified asphalt; the results show that the modified asphalt has good rutting resistance.

Bitumen’s self-healing capability is critical to the bitumen industry’s sustainable development. This work attempts to examine the self-healing property and fatigue behavior of bitumen using waste cooking oil (WCO) and polyphosphoric acid (PPA) in bitumen modification. Different components of WCO were mixed with PPA and bitumen for the initial modification. The linear amplitude sweep (LAS) test was used to evaluate the fatigue behavior of the modified bitumen. To assess the extent of bitumen healing after a fatigue-healing test, evaluation indicators, including fatigue life recovery (FLR), modulus recovery (MR), and dissipated energy recovery (DER), were selected. Meanwhile, a radar chart was used to analyze the integrated performance of WCO/PPA (WP)-modified bitumen. Lastly, the SARA fractions were separated from the bitumen to evaluate the modification mechanism. It was observed that the inclusion of PPA and WCO enhanced fatigue behavior. For 2% PPA and an intermediate component (IC) of WCO, the fatigue life of the LAS prediction model showed extreme values, with an increase of 669% over virgin bitumen. Regardless of the PPA concentration, a considerable increase in FLR, MR, and DER was seen in the bitumen processed with IC compared to virgin bitumen. Additionally, as the healing time was extended, the increment in the virgin bitumen’s healing indicators was higher than that of the modified bitumen. SARA results indicated that adding PPA changes the bitumen from a soluble state to a gel state. An innovative approach has been proposed to promote sustainable development within the bitumen industry.