The use of reclaimed asphalt pavement (RAP) is a hot research topic in the field of road engineering, as there are still many issues to overcome so as to become standard engineering applications. The diffusion of virgin/aged asphalt binder is a key process to improve RAP performance. In this study, the asphalt binder diffusion models were developed by molecular dynamics (MD) simulation. Two kinds of bio-rejuvenators (BR-1 and BR-5) were chosen to represent the straight-chain and aromatic structures, respectively. The method of relative concentration, radial distribution function (RDF), and microstructure morphology were used to evaluate the effect of bio-rejuvenators on the diffusion process of virgin/aged asphalt binder. The results showed that bio-rejuvenators had a positive effect on the fusion process between virgin and aged asphalt binder. The volume diffusion coefficient based on asphalt binder diffusion models indicated that the bio-rejuvenators accelerated the fusion process between the virgin and asphalt binder. After adding bio-rejuvenators to the aged asphalt binder, the agglomeration intensity in the SARA fractions was reduced to different degrees. Due to the aging of asphalt binder, asphaltenes formed different types of micro-stacking phenomena such as “T-shaped stacking,” “Face to Face stacking,” and “Offset Face to Face stacking.” The bio-rejuvenators of BR-1 and BR-5 exerted different regenerative effects during the diffusion process of aged asphalt binder. For BR-1, the “Pull-Out” and “Intercalation” effect can be observed in the process of asphaltene deagglomeration. “Pull-Out” is the main regenerative effect of BR-5 in aged asphalt binder. A strong electrostatic interaction occurs between BR-5 and PAHs in asphaltenes. Thus, BR-5 achieves the goal of aged asphalt binder regeneration by attracting PAHs.

Sustainable and resilient pavement infrastructure is critical for current economic and environmental challenges. In the past 10 years, the pavement infrastructure strongly supports the rapid development of the global social economy. New theories, new methods, new technologies and new materials related to pavement engineering are emerging. Deterioration of pavement infrastructure is a typical multi-physics problem. Because of actual coupled behaviors of traffic and environmental conditions, predictions of pavement service life become more and more complicated and require a deep knowledge of pavement material analysis. In order to summarize the current and determine the future research of pavement engineering, Journal of Traffic and Transportation Engineering (English Edition) has launched a review paper on the topic of “New innovations in pavement materials and engineering: A review on pavement engineering research 2021”. Based on the joint-effort of 43 scholars from 24 well-known universities in highway engineering, this review paper systematically analyzes the research status and future development direction of 5 major fields of pavement engineering in the world. The content includes asphalt binder performance and modeling, mixture performance and modeling of pavement materials, multi-scale mechanics, green and sustainable pavement, and intelligent pavement. Overall, this review paper is able to provide references and insights for researchers and engineers in the field of pavement engineering.