Unraveling the nano-cracking mechanism in aged asphalt binder with consideration of rejuvenation effects

Abstract

For achieving the sustainable utilization of reclaimed asphalt pavement, a popular approach is to incorporate rejuvenators to restore the cracking resistance of aged asphalt. However, research on the nanoscale rejuvenation mechanisms and the relationship with the cracking behavior is limited. To address this challenge, this study utilizes molecular dynamics simulations to explore the fundamental cracking mechanism in aged asphalt and elucidate how rejuvenators affect this process. A multiphysics analysis, including mechanical response, morphology relationship, energy evolution, deagglomeration and lubrication behavior is developed to comprehend the nano-cracking mechanism. Computational findings reveal that the cracking failure originates form cavitation, and the process primarily includes nanovoid formation, enlargement, filamentation, and separation. Oxidation enhances the aggregation of asphaltene molecules and reduces intermolecular rearrangement and mobility, which fundamentally accelerates the nano-cracking process. Owing to the diffusion of rejuvenators and their disturbances to asphaltene π-π stacking, rejuvenators can penetrate into aged asphalt molecules, lubricate and reduce intermolecular friction. This facilitates molecular rearrangement during the cracking process, thereby improving the cracking resistance and energy performance of aged asphalt binder. The finding from this study contributes to elucidating the fundamental cracking mechanism in rejuvenated asphalt binder and promoting the sustainable utilization of recycled pavement materials.