Study on the Disintegration Mechanism of the Asphalt–Aggregate Interface Bonding System Based on Salt-Spray Ions Invasion Behavior

To study the potential impact of the coastal salt-spray environment on asphalt pavement performance, a salt-spray ion invasion test, microscopic tests, and molecular dynamics (MD) simulation can be combined to reveal the disintegration mechanism of the asphalt–aggregate interface bonding system caused by salt-spray ion invasion behavior. First, through the salt-spray ion invasion test, the samples of the asphalt–aggregate interface bonding system invaded by salt-spray ions were obtained, and the corresponding microscopic models can be established. Subsequently, the behavior characteristics of salt-spray ions invading the asphalt–aggregate interface were observed by atomic force microscopy (AFM), and the evolution law of the microscopic morphology for the asphalt surface can be discussed. Finally, scanning electron microscopy (SEM) and MD were used to investigate the behavior characteristics and disintegration mechanism of the asphalt–aggregate interface bonding system invaded by salt-spray ions. It can be found that the asphalt on the aggregate surface can be invaded by salt-spray ions and form intrusion cavity structures, through which the asphalt–aggregate interface bonding system can be invaded. As the concentration increases, the diffusion ability of Na+ and Cl– in the invasion cavity structure decreases, making it easier to form NaCl crystals. Meanwhile, the invasion of the asphalt surface, the competitive adsorption on the aggregate surface, and the reduction of interface interaction energy can jointly constitute the disintegration behavior of the asphalt–aggregate interface bonding system. The study has revealed the behavior mechanism of salt-spray ions invading the coastal asphalt pavement and provided a theoretical basis for enhancing the sustainable service of coastal transportation infrastructure.