Study on the Durability of Acid Rain Erosion-Resistant Asphalt Mixtures

Acid erosion can accelerate the process of early damage of asphalt pavement and decrease the durability of asphalt pavement. However, there are limited research results for asphalt mixtures that can resist acid rain erosion. To systematically evaluate the impact and action law of acid rain erosion on the durability of asphalt mixtures, three gradation schemes were used: periodic dry–wet cycle immersion test, contact angle test and road performance test. The acid rain erosion resistance of epoxy asphalt mixture, SBS-modified asphalt mixture and 70# matrix asphalt mixture were tested from three aspects of anti-aging performance, freeze–thaw cycle performance and fatigue performance. The results show that the erosion of acid rain can significantly decrease the adhesion between asphalt and aggregate, and affects the road performance of the asphalt mixture. Acid rain erosion can significantly decrease the mechanical properties, adhesion and durability of asphalt mixtures. Epoxy asphalt has better physical properties, adhesion and acid rain erosion resistance than 70# matrix asphalt and SBS-modified asphalt. Epoxy asphalt has excellent adhesion due to its polar group, high cohesion and thermosetting resin with low shrinkage, which can effectively resist moisture erosion, spalling and temperature stress cracking, thereby effectively resisting the erosion of acid rain. Epoxy asphalt mixture has the strongest acid rain erosion resistance, which can be further enhanced when used together with waste rubber powder and modified bamboo fiber. On the whole, asphalt mixture with high-density structure and thicker asphalt film can effectively resist acid rain erosion. The durability of asphalt concrete (AC)-type gradation mixture and stone mastic asphalt (SMA)-type gradation mixture are equivalent, and both are superior to open-graded friction courses (OGFC)-type gradation mixture. The gradation of asphalt mixtures and the type of asphalt binder have great influence on their acid rain erosion resistance and durability. In order to realize the directional control of the acid rain erosion resistance and durability of different asphalt mixtures, a multi-parameter comprehensive assessment indicator system between the type and property of asphalt, the gradation of asphalt mixture, and the acid rain resistance and durability of the mixture need to be established in the future.