Insight into the compatibility behaviors between various rejuvenators and aged bitumen: Molecular dynamics simulation and experimental validation

The compatibility potential of rejuvenators plays an important role in improving the blending degree of rejuvenated bitumen. This study aims at estimating the efficiency of molecular dynamics (MD) simulation in predicting the compatibility between rejuvenators and aged bitumen, and exploring the influence of rejuvenator type, aging degree of bitumen, and temperature on the compatibility potential. The thermal storage stability of rejuvenated binders is evaluated to validate the compatibility prediction. Afterward, the underlying mechanism for the storage stability difference between rejuvenators and aged bitumen is explained with the atomic-scale parameters. The results revealed that the ranking on predicted compatibility and experimentally measured thermal storage stability for four rejuvenators is the same as AO > BO > NO > EO. Furthermore, the thermodynamic parameters of solubility parameter difference Δδ, Flory-Huggins parameter χ, and mixing free energy ΔGm are efficient for estimating the compatibility potential of various rejuvenators with aged bitumen. Moreover, the separation index (SI) parameters based on rheological and chemical indices are available to assess the phase stability of rejuvenated bitumen. At the molecular scale, the compatibility and phase stability issues between rejuvenators and aged bitumen are complicated and related to different aspects of intermolecular interaction, dispersion degree, and molecular mobility.