Adhesion failure mechanism of asphalt-aggregate interface under an extreme saline environment: A molecular dynamics study

The extreme saline environment seriously threatens the service life of asphalt pavement. The interface adhesion failure between asphalt and aggregate is fundamental to pavement diseases. Therefore, the interface of asphalt-NaCl solution-mineral was simulated by molecular dynamics to investigate the adhesion failure mechanism between asphalt and aggregate in an extremely saline environment. The results show that the polarization-inducing effects of sodium and chloride ions promote the cross-sectional diffusion of the NaCl solution at the interfaces and contribute to the redistribution and rediffusion of asphalt components, and the formation of hydrogen bonds between water and asphalt components. The NaCl solution prevents the accumulation of saturates, resins, and asphaltenes on the SiO2 surface, and strips aromatics from the SiO2 surface due to the interaction. Sodium ions can be attracted to the oxygen atoms on CO32– to occupy active sites on the CaCO3 than asphalt, which makes it easier for chloride ions to penetrate the asphalt molecule and asphalt components to detach from CaCO3. These behaviors effectively impair the adhesion at the asphalt-mineral interface. The 3 wt% and 20 wt% NaCl solutions have the greatest effect on the adhesion work of the asphalt-SiO2 and asphalt-CaCO3, reducing them by 55.93 % and 66.03 %, respectively.