Diffusion Influence Mechanism of Virgin and Aged Asphalt Binder System Based on Molecular Dynamics

During the production and transport of reclaimed asphalt pavement (RAP), the diffusion of recycled aged asphalt binder and virgin asphalt binder can significantly affect the mechanical properties of the virgin and aged asphalt binder system. Therefore, a thorough understanding of the diffusion behavior of virgin and aged asphalt binder system is essential for the production of RAP. In this study, a diffusion model of the virgin and aged asphalt binder system was established based on the Fick’s law to calculate the complex shear modulus ($|{\mathrm{G}}_{\mathrm{T}}^{*}|$) of the system. The calculated $|{\mathrm{G}}_{\mathrm{T}}^{*}|$ values were then compared with the measured values ($|{\mathrm{G}}_{\mathrm{D}}^{*}|$) obtained from the dynamic shear rheological (DSR) test. molecular dynamics (MD) simulations were also carried out to investigate the diffusion behavior of the virgin and aged asphalt binder system and to compare the simulated and calculated values of the diffusivity (D). The influence of different asphalt binder layers and saturates, aromatics, resins, and asphaltenes (SARA) on the diffusion behavior of the system was also analyzed. The results show that the $|{\mathrm{G}}_{\mathrm{T}}^{*}|$ values calculated by the diffusion model are in good correlation with the $|{\mathrm{G}}_{\mathrm{D}}^{*}|$ values measured by the DSR test at different temperatures and times. Furthermore, the diffusivity of virgin asphalt binder was found to be smaller than that of the four individual components, suggesting that the colloid structure and intermolecular interactions of asphalt binder play a crucial role in its diffusion behavior.

Asphalt pavement is a common form of pavement, but it can be seen in life that asphalt pavement often has diseases such as cracks and potholes. The cause of some pavement diseases is the decrease of the performance of asphalt binder in the pavement. Under the action of natural factors, the phenomenon that the performance of asphalt binder gradually changes with time is called asphalt aging. Therefore, if the principle of asphalt aging can be mastered, the influencing factors of asphalt aging can be clarified, and a rejuvenator that can restore the performance of aged asphalt binder to the greatest extent can be designed. It can delay the aging rate of asphalt binder and improve the durability of asphalt pavement, conversely, it can also effectively recycle and renovate old asphalt pavement, reuse waste asphalt concrete, and reduce the waste of resources. This article mainly uses molecular dynamics simulation to achieve the preceding purpose. The result is helpful in providing guidance for the production of RAP in practical application.