Performance evaluation of rejuvenators in recycled asphalt mixtures based on mechanical and rheological properties

The use of recycled materials in asphalt mixtures contributes to reducing costs and enhancing the longevity of road infrastructure. However, due to the presence of aged binder in reclaimed asphalt, additives known as rejuvenators are required to restore the lost properties of the binder. This study aims to evaluate the effects of various rejuvenators on the mechanical, rheological, and chemical properties of recycled asphalt mixtures to identify the most effective option for enhancing their durability and performance. Various tests were conducted, including Gel Permeation Chromatography (GPC), Bending Beam Rheometer (BBR), Dynamic Shear Rheometer (DSR), Multiple Stress Creep Recovery (MSCR), and Field Emission Scanning Electron Microscopy (FESEM), to assess the performance of different rejuvenators. The rejuvenators studied include gasoline-engine recycled motor oil with 1 oxidation degree (WEG1), gasoline-engine recycled motor oil with 3 oxidation degrees (WEG3), diesel-engine recycled motor oil with 1 oxidation degree (WED1), diesel-engine recycled motor oil with 3 oxidation degrees (WED3), recycled cooking oil (WCO), and Cyclogen oil (CY). The BBR test results indicate that rejuvenators with lower oxidation levels and specific compositions, such as WEG1, WCO, and WED1, demonstrated better performance in maintaining stiffness and preventing cracking. Furthermore, the DSR results revealed that all the evaluated rejuvenator compositions exhibited satisfactory performance at high temperatures. The FESEM results also indicate that different rejuvenators can have varying effects on the surface structure and material behavior. Also, the MSCR results show that the best performances are observed among the WEG3 and WED2 samples. Additionally, a Multi-Criteria Decision-Making (MCDM) method was used to select the optimal rejuvenator based on test results. The results showed that WEG3 exhibited the best overall performance in improving the mechanical and rheological properties of recycled asphalt mixtures. As a conclusion, this study showed that rejuvenators, especially WEG3, significantly improve the mechanical, chemical, and thermal properties of reclaimed asphalt mixtures. The results highlight the potential of recycled motor oil-based rejuvenators to enhance durability and support environmental sustainability.