Effects of different types of acid rain on water stability of asphalt pavement

•The influence of different types of acid rain on the water stability of semi-flexible pavement is clarified.•The variation trend of water stability performance index of semi-flexible pavement under different acid rain types was obtained.•Based on molecular dynamics theory, a molecular dynamics model of acid rain corrosion of asphalt mixture was established.•Three different types of acid rain were first used for experimental simulation.•Based on experiments and supported by theory, the engineering problems are analyzed in detail. As is known to all, China is one of the countries with more acid rain in the world, and acid rain is mainly distributed in the southern humid climate area of China. However, the construction of semi-flexible asphalt pavement exposed to acid rain environment is a very realistic problem. In order to clarify the influence of different types of acid rain on the water stability of semi-flexible pavement, sulfuric acid type acid rain, nitric acid type acid rain and mixed type acid rain were prepared in this paper, and the semi-flexible specimens were soaked periodically. The water stability of semi-flexible pavement under different types of acid rain corrosion was evaluated macroscopically by standard Marshall test, immersion Marshall test, freeze-thaw splitting test and vacuum saturation test. It was concluded that the Marshall stability, immersion Marshall residual stability, freeze-thaw splitting strength ratio and vacuum saturation residual stability of semi-flexible pavement under different types of acid rain showed different degrees of decline. The reasons for the decline of water stability of semi-flexible pavement under different types of acid rain corrosion were analyzed by scanning electron microscopy and infrared spectroscopy. It was concluded that the acidification condition of rainwater was the main reason for the decrease of ductility, viscosity and plasticity of petroleum asphalt, which affected the binding force between petroleum asphalt and limestone aggregate, and ultimately led to the decline of water stability of semi-flexible pavement. Based on the molecular dynamics theory, the molecular dynamics model of acid rain corrosion asphalt mixture is established. According to the sensitivity of acid components to the main components of semi-flexible asphalt mixture, the asphalt, oil, resin and calcium carbonate with the most content in semi-flexible asphalt mixture are selected to simulate and study. The changes of bondin