Sustainable asphalt rejuvenation with sub-epoxidized soybean oil: A microscale-to-macroscale investigation

Bio-based rejuvenators offer a sustainable alternative to petroleum-derived products. The performance of bio-rejuvenated asphalt is strongly governed by the epoxide value and dosage, yet the optimal formulation have not been established. This study evaluates sub-epoxidized soybean oil (SESO) with varying epoxide values and dosages as asphalt rejuvenators through molecular dynamics (MD) simulations and rheological tests. At the molecular level, MD analyses including radial distribution function (RDF), cohesive energy density (CED), fractional free volume (FFV), and mean square displacement (MSD). They demonstrated that SESO disrupts heavy-component aggregation, enhances molecular mobility, and strengthens intermolecular interactions with increasing epoxide value. At the macroscale, rheological tests of Dynamic Shear Rheometer (DSR), Bending Beam Rheometer (BBR), and Linear Amplitude Sweep (LAS) were conducted. The results indicated that SESO reduces stiffness and improves thermal and fatigue cracking resistance, though high-temperature rutting resistance declines. Higher dosages further enhanced low-temperature and fatigue performance, while higher epoxide values promoted better aggregate dispersion and elasticity. Overall, 6 % SESO with a high epoxide value provided the most effective rejuvenation of aged asphalt. This findings could help in the design and formulation of epoxidized vegetable oil-based rejuvenators. ● PESO enhanced the thermal and fatigue cracking resistance of aged binders. ● High-epoxy PESO rejuvenated binder demonstrated improved elasticity. ● High-epoxy PESO effectively dispersed agglomerates of asphaltenes and resins. ● High-dosage PESO showed a stronger softening effect on aged binder. ● 6 % high-epoxy PESO exhibited the best rejuvenation effect on aged binder.