Multiscale Modeling and Experiments Reveal How Sustainable Rejuvenators Restore the Rheological Properties of Aged Asphalt

This study developed a rheological analysis toolbox, SmartRheo, and systematically investigated the multiscale rheological recovery performance of four sustainable rejuvenators─epoxidized soybean oil (ESO), waste cooking oil (WCO), waste engine oil (WEO), and naphthenic oil (NO)─on aged asphalt binders using this software. Through integrated thermogravimetric analysis, dynamic shear rheometry, molecular dynamics simulations, and microstructural characterization, the rejuvenation mechanisms and performance distinctions were elucidated. Results demonstrate superior thermal stability at 200 °C for ESO and WCO. WCO exhibited optimal compatibility, effectively dissolving asphaltene aggregates and promoting uniform dispersion, thereby significantly enhancing viscous behavior and reducing stiffness across a wide temperature range. Notably, asphalt rejuvenated with WCO surpassed the virgin binder in key performance metrics, including crossover frequency and rutting resistance. The linoleic acid chains in WCO contributed to improved low-temperature flexibility and fatigue resistance. Overall, the rejuvenators─particularly WCO─effectively restored the rheological properties of aged asphalt close to its original state by replenishing lost light components, rebalancing chemical composition, and mitigating detrimental π–π interactions. This approach offers a promising pathway for enhancing pavement sustainability while reducing the consumption of virgin materials.