Atomistic modelling of moisture sensitivity: a damage mechanisms study of asphalt concrete interfaces

Moisture-induced damage mechanisms are characterised by adhesive bond strength reduction at the aggregate–asphalt interfaces. This research examined the physicochemical phenomena that occur at the asphalt–aggregate interfaces, as well as the nanoscale effect of water molecules on the asphalt–aggregate bond using atomistic simulations. The moisture sensitivity behaviour of model asphalt, water molecules, and mineral aggregates of various components was evaluated. Steered molecular dynamics was used to study the interfacial atomic separation under dry and wet conditions. The effect of water on the bond strength between asphalt and aggregate was described through surface free energy studies. It was found that the adhesion and stripping behaviours between asphalt and aggregate were more strongly influenced by the aggregate chemistry and properties than those of the asphalt. The adhesion of different asphalt–aggregate pairs and their susceptibility to water were also validated by available experimental results and pavement engineering observations. This work provides an insight into the orientation and interaction of asphalt molecules in the wet interfaces.