Investigation of Water Drainage Capability for Porous Asphalt Material with Varying Slope and Porosity Based on Laboratory Experiment

This study assessed the water drainage capability of porous asphalt material (PAM) based on laboratory rainfall simulator tests. A series of tests were conducted using a range of slopes and rainfall intensities. The results showed that as the rainfall intensity increased, the water subsurface drainage steadily decreased. When the slope increased, the subsurface outflow of the porous asphalt decreased. Nevertheless, the slope of PAM insignificantly affected the water subsurface drainage. For the PAM specimen with a porosity of 15%, at a rainfall intensity of 2.5 L/min, when the slope increased from 0% to 8%, the subsurface outflow reduced by 2.8%. The investigation of the effect of porosity on subsurface drainage showed that the porous asphalt with a higher porosity displayed a higher subsurface drainage. At the slope of 4%, at a rainfall intensity of 4.9 L/min, for the PAM specimen with porosity of 10% and 15%, the subsurface outflow was 72.3% and 79.1%, respectively. It could be seen that the porosity had a strong effect on the drainage capability of PAM. The above results imply that the utilization of PAM depended more on the porosity than the slope. In the future, further experiments evaluating the water drainage of PAM should be adopted.