A molecular insight into asphalt-aggregate interfacial debonding: The role of hydrogen bonds in water molecule migration

Abstract

In this study, molecular dynamics were employed to compare the angles, lengths, and numbers of hydrogen bonds between water molecules and different aggregates. Compared to quartz, calcite has shorter bond lengths, larger bond angles, and a greater number of bonds with water molecules. The differences in hydrogen bonds lead to the formation of a three-layer structure on the calcite surface by water molecules: ordered, relatively ordered, and disordered, while a two-layer structure—relatively ordered and disordered—is formed on the quartz surface. In the ordered layer, water molecules experience the strongest hydrogen bonding, are neatly arranged, and have low diffusion coefficients. In contrast, the disordered layer is characterized by weaker hydrogen bonding, random arrangement, and higher diffusion coefficients. The movement path of water molecules shows that the debonding of asphalt and aggregate is jointly influenced by the migration behavior of both the underlying and upper-layer water molecules. These findings reveal the microscopic mechanism of water molecules forming a wedge shape at the asphalt-aggregate interface from the perspective of hydrogen bonds, explaining why the constraint of water on the Calcite {214} and Calcite {018} surfaces is stronger compared to Calcite {1 0 4}, but the bonding energy with asphalt decays more rapidly.