Understanding the True Asphalt Rejuvenation Mechanism at the Molecular Level: From Interface Diffusion to Component Compatibility and Depolymerization

The rejuvenation of aged asphalt by rejuvenators is a complex, multistage process involving interfacial diffusion, component compatibility, and asphaltene depolymerization. However, these key stages are rarely investigated simultaneously. In this study, molecular dynamics and quantum chemical simulations were employed to systematically elucidate the interfacial diffusion behavior, compatibility characteristics, and asphaltene depolymerization mechanisms of representative rejuvenators. Based on these results, a comprehensive evaluation framework integrating diffusion, compatibility, and depolymerization was established to assess overall rejuvenation efficiency and identify optimal rejuvenator types and molecular structures. The results indicate that furfural oil (FO) exhibits the strongest interfacial diffusion ability, attributed to its low molecular weight and strong interactions with polar asphalt components, followed by aromatic oil (AO). In contrast, soybean oil (SO) shows inhibited diffusion due to its larger molecular size and steric hindrance. Compatibility analyses reveal that AO, with low polarity and small molecular size, displays the best compatibility by effectively infiltrating nonpolar asphalt components, whereas FO and SO exhibit reduced compatibility due to higher polarity or structural complexity. Furthermore, the long-chain aliphatic and carboxyl functional groups of SO disrupt asphaltene aggregation through steric hindrance and competitive adsorption, resulting in a comparatively stronger depolymerization effect. Overall, FO demonstrates the highest rejuvenation efficiency, followed by AO, while SO exhibits the lowest. These findings clarify the structure–activity relationships between rejuvenator molecular characteristics and their microscopic interactions with aged asphalt, providing theoretical guidance for the molecular-level design of high-efficiency asphalt rejuvenators. Moreover, they contribute to reducing the consumption of virgin asphalt resources and mitigating the environmental impacts of waste asphalt pavements, thereby promoting the green, low-carbon, and sustainable development of reclaimed asphalt pavement recycling. • Investigation of asphalt rejuvenation mechanisms using molecular dynamics and quantum chemical simulations. • Comprehensive study of the rejuvenation process from interfacial diffusion, component compatibility, and depolymerization perspectives. • Furfural oil exhibits the strongest interfacial diffusion capability. • Aromatic oil shows the best component compatibility capability. • Soybean oil achieves the most effective asphaltene depolymerization capability. • Considering overall rejuvenation performance, furfural oil demonstrates the highest rejuvenation efficiency.