AbstractThe main objective of this research is to develop a sustainable and environment-friendly asphalt binder based on the reutilization of waste engine oil (WEO) alongside crumb rubber (CR), two major waste materials of the automobile industry. This composite modification eliminates the limitations and the negative effects of solo application of these waste modifiers, including the poor workability and pumpability of the CR-modified binder, as well as compromised rutting resistance of the biobinder modified with WEO. Besides investigating the high-temperature properties of the composite-modified binder with CR and WEO, for the first time, a new method is presented to analyze the influence of the preparation parameters on the performance of the binder and optimize the whole production process. For this purpose, the design of experiment was conducted with the aid of the central composite design (CCD) method, and the rheological properties of the binders were evaluated by rotational viscosity (RV), dynamic shear rheometer (DSR), and multiple stress creep recovery (MSCR) tests. Based on the results of rotational viscosity at 135°C and the unaged and RTFO-aged rutting factor values at 58°C, regression models were established and analysis of variance was carried out on the preparation parameters. Overall, test results indicated that the addition of 5%–10% blending content of WEO in the composite-modified binder could achieve a satisfactory rutting resistance while improving its workability and pumpability. On the other hand, although the content of WEO had the most significant influence on the rheological properties of the binder samples, other parameters including preparation temperature and time also had influence to some extent. Additionally, optimum values of the preparation parameters were determined, and the production process was optimized.