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

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 bonding energy and diffusion coefficient of asphalt mixture under different types of acid rain are calculated and analyzed. It is concluded that sulfuric acid acid rain has the greatest influence on the water stability of semi-flexible specimens, followed by mixed acid rain, and the influence of nitric acid rain is relatively small.

众所周知，中国是世界上酸雨较多的国家之一，酸雨主要分布在中国南方湿润气候区。然而，处于酸雨环境下的半柔性沥青路面的建设是一个非常现实的问题。为了明确不同类型酸雨对半柔性路面水稳定性的影响，本文制备了硫酸型酸雨、硝酸型酸雨和混合型酸雨，并定期浸泡半柔性试件。通过标准马歇尔试验、浸水马歇尔试验、冻融劈裂试验和真空饱水试验从宏观上评估了不同类型酸雨腐蚀下半柔性路面的水稳定性。得出结论：不同类型酸雨作用下半柔性路面的马歇尔稳定度、浸水马歇尔残留稳定度、冻融劈裂强度比和真空饱水残留稳定度均出现不同程度的下降。通过扫描电子显微镜和红外光谱分析了不同类型酸雨腐蚀下半柔性路面水稳定性下降的原因。得出结论：雨水的酸化条件是石油沥青延性、粘性和塑性降低的主要原因，这影响了石油沥青与石灰石集料之间的结合力，最终导致半柔性路面水稳定性下降。基于分子动力学理论，建立了酸雨腐蚀沥青混合料的分子动力学模型。根据酸性成分对半柔性沥青混合料主要成分的敏感性，选取半柔性沥青混合料中含量最多的沥青、油分、树脂和碳酸钙进行模拟研究。计算并分析了不同类型酸雨作用下沥青混合料结合能和扩散系数的变化。得出结论：硫酸型酸雨对半柔性试件水稳定性的影响最大，其次是混合型酸雨，硝酸型酸雨的影响相对较小。