A novel WCO-MDI reactive rejuvenation method for aged SBS modified asphalt toward sustainable asphalt pavements

The sustainable advancement and low-carbon application of asphalt pavement significantly benefit from the reutilization of waste SBS modified asphalt (SBSMA) mixtures. However, the high-efficiency rejuvenation of aged SBSMA (ASBSMA) remains a persistent challenge. In this study, a novel reactive rejuvenator was developed using waste cooking oil (WCO) and methylene diphenylene isocyanate (MDI) to restore asphalt components and reconstruct SBS structures in ASBSMA. Temperature Sweep, Fourier Transform Infrared (FTIR) spectroscopy and Differential Scanning Calorimetry (DSC) tests were conducted to investigate the rejuvenation effect and mechanism of ASBSMA. The results indicate that the incorporation of WCO restores the low temperature performance of ASBSMA, but adversely affects its high temperature performance. Conversely, the addition of MDI enhances the high temperature performance of ASBSMA, but an excessive dose of MDI has a negative impact on its low temperature performance. Chemical composition analysis shows that the rejuvenation by WCO is a physical dissolution and softening process, while MDI can react with the SBS aged products to produce long chain products with an amide structure and reconstruct the cross-linked structure of SBS. Although the temperature stability of rejuvenated SBSMA is not fully restored to its original state, it shows significant improvement compared with ASBSMA due to the reconstruction of SBS structure. This study effectively clarifies the reactive rejuvenation mechanism of ASBSMA, achieves the synergistic restoration of asphalt components and SBS structure, and contributes to high-efficient recycling of WCO and waste asphalt materials.