Molecular dynamics study of oxidative aging effect on asphalt binder properties

The oxidative aging effect of asphalt binder was investigated using molecular dynamics simulation in this study. Representative molecular models of aged asphalt were built by introducing ketone and sulfoxide function groups into virgin asphalt. The asphalt molecular models were validated in terms of thermodynamic properties such as density, surface energy, viscosity, and cohesive energy density. The molecular structures of virgin and aged asphalt were analyzed by mean square displacement (MSD) and radial distribution function (RDF) of molecules and diffusion coefficient. The aging effect on self-healing potential and moisture damage susceptibility of asphalt were investigated. Results show that the molecular structure of asphalt is in agreement with the colloidal theory. Aging weakens the nano-aggregation behavior of asphaltene molecules and reduces the translational mobility of asphalt molecules. Compared to virgin asphalt, aged asphalt has the higher activation energy barrier for self-healing. Inclusion of water molecules in the asphalt-aggregate interface causes degradation of work of adhesion and this effect is more significant for aged asphalt. The research findings provide insights to better understand the chemo-physical and chemo-mechanical relationships of asphalt-based materials.