Study on Water Damage of Asphalt–Aggregate Based on Molecular Dynamics

To investigate the water damage at the interface between emulsified asphalt and aggregate under the action of external water infiltration, firstly, cetyltrimethylammonium bromide was used as an emulsifier to prepare emulsified asphalt in the laboratory, and its basic properties were tested. Then, based on molecular dynamics, an emulsified asphalt–aggregate interface model with different water contents was constructed to calculate the adhesion work of the emulsified asphalt–aggregate interface. The results show that the simulated values of emulsified asphalt density, cohesive energy density, and solubility are in good agreement with the experimental values. Under the same water content, the adhesion force between asphalt and three oxides (CaO, Al2O3, SiO2) is arranged in the following order: CaO > Al2O3 > SiO2. The bonding performance of an alkaline aggregate to asphalt is better than that of an acid aggregate. The van der Waals force plays a major role in the adhesion performance of an emulsified asphalt mixture, and electrostatic force plays a secondary role. Under the action of external force, the macroscopic failure mode of the emulsified asphalt–aggregate is as follows: the alkaline oxide-emulsified asphalt system is cohesive failure; the acid and neutral oxide-emulsified asphalt system is adhesive failure; the enrichment of water molecules at the interface is the main factor causing water damage.