Internal structure change of porous asphalt concrete under coupled conditions of load, moisture and temperature

Abstract

In the actual working environment, the pore water pressure generated by wheel loading may accelerate the damage accumulation to the internal structure of porous asphalt concrete (PAC), resulting in the performance deterioration. In this study, a modified immersion wheel tracking test was developed by incorporating the image processing and analysis method to capture the internal structure change of the PAC at the different loading time. The varying temperatures and moisture conditions were also considered to evaluate the effect of the coupled condition. According to average rutting depth rate, the loading process was divided into three stages of condensation, transition and stabilization. The change of mesoscopic indices corresponding to each stage were analyzed. Based on void area change under wheel loading, it has been found that the rising temperature may worsen failure development and moisture damage may promote the condensation of the specimen. In comparison to a single-layer specimen, a strong constraint of the bottom layer inside a two-layer specimen on the top layer may limit void expansion. The change of aggregate skeleton was evaluated based on contact length. The loss of contact length could be due to filling failure, rheological failure and over-compaction failure. Because of the negative effect of increased temperature and moisture on asphalt mortar, wheel loading may cause more extensive skeleton degradation, leading in more contact length loss. The findings of this study reveal important information about the rutting resistance deterioration of PAC from a mesoscopic viewpoint.