Regeneration mechanisms of aged bitumen by rejuvenators: Insights from interfacial diffusion and structural deagglomeration

To realize the efficient recycling of aged bitumen, it is of great significance to reveal the regeneration mechanisms of aged bitumen for the selection and design of rejuvenators. First, the physical properties and microstructure of mineral rejuvenators and biomass rejuvenators were investigated. Then, the diffusion behavior at the interface between the rejuvenator and aged bitumen and the deagglomeration behavior of the rejuvenator on the agglomerates of aged bitumen were quantitatively characterized based on mechanical properties and structural characteristics of recycled bitumen. Finally, the regeneration mechanisms of rejuvenators on aged bitumen were analyzed based on molecular dynamics simulations of colloidal interfacial diffusion behavior and colloidal structural deagglomeration behavior. The results showed that mineral rejuvenators demonstrated better ability to accelerate the diffusion at the colloidal interface of aged bitumen and virgin bitumen due to their small molecular weight and non-polar properties. However, the deagglomeration of aged bitumen colloid structure was limited, mainly because the small moleculars could only fill the free volume of aged bitumen, but could not effectively achieve the deagglomeration of asphaltene nanoclusters. Biomass rejuvenators exhibited weak diffusion performance due to their macromolecular structure. However, they could effectively exert the steric hindrance effect to realize the deagglomeration of asphaltene nanoclusters, which was attributed to the fact that the functional group branched chain of biomass rejuvenators could exert pullout and intercalation effect to deagglomerate the asphaltene nanoclusters. The regeneration efficiency of aged bitumen is jointly determined by the diffusion rate and the deagglomeration effectiveness of the base oil in rejuvenator. Therefore, balancing both diffusion capability and deagglomeration performance constitutes a critical consideration in the design and development of high-performance rejuvenators.