Performance Evaluation of High-RAP Asphalt Mixtures with Compound Bio-Based Rejuvenators

The use of reclaimed asphalt pavement (RAP) in road construction offers significant environmental and economic advantages. However, asphalt mixtures with high RAP content can lead to reduced performance compared with conventional asphalt pavement. This study investigated the potential of compound bio-based rejuvenators, derived from waste cooking oil (WCO), to improve the road performance of recycled hot-mix asphalt (RHMA) with high RAP content. The effects of different rejuvenators at three dosages (4.8%, 6.0%, and 7.2% for 30% RAP and 8%, 10%, and 12% for 50% RAP, by mass of recycled binder) on the high-temperature performance, moisture susceptibility, and medium- and low-temperature cracking resistance of RHMA containing 30% and 50% RAP were evaluated. The degree of blending (DoB), voids in mineral aggregate (VMA), and voids filled with asphalt (VFA) were used to represent changes in volumetric characteristics. A comprehensive evaluation of the rejuvenator’s effectiveness was conducted using principal component analysis (PCA). The results indicated that bio-based rejuvenators effectively activate aged asphalt, and optimal dosages vary based on RAP content. The addition of compound bio-based rejuvenators with SBS-repairing capabilities partially mitigates the reduction of high-temperature performance of RHMA caused by adding WCO, and also restores moisture resistance compromised by RAP. Increasing rejuvenator content improves midtemperature flexibility and overall low-temperature cracking resistance, though it may reduce low-temperature fracture toughness. PCA results indicated that at a 50% RAP content, the comprehensive rejuvenation effect of compounded bio-based rejuvenators is superior to that of conventional bio-based rejuvenators in RHMA with high RAP content. However, at a 30% RAP content, the compounded rejuvenator did not exhibit a comprehensive advantage compared with traditional bio-based rejuvenators. Compound bio-based rejuvenators demonstrate significant potential in improving the road performance of RHMA with high RAP content, promoting sustainable pavement construction practices.