Purification performance of zeolite-modified porous asphalt mixtures for pavement runoff treatment

Stormwater runoff has been a major non-point source of urban water pollution due to the widespread expansion of impervious surfaces. Porous asphalt pavement is recognized as an effective technology for mitigating this problem with both environmental benefits and functional features. As one of the most commonly used overlays of asphalt pavement, porous asphalt mixture plays a critical role in filtering and absorbing pollutants in pavement runoff. This study evaluated the feasibility of using zeolite in porous asphalt mixture to improve its purification effectiveness, for removing and absorbing the pollutants. The effect of zeolite on optimum asphalt binder content and its influence to performance of porous asphalt mixture were investigated. Test results indicated that zeolite increased the optimum asphalt content of porous asphalt mixture due to its strong oil adsorption capacity. Based on the performance test results and specification criterion, zeolite content was determined as 50 % of the limestone filler volume used in porous asphalt mixture. The filtration test and immersion adsorption test confirmed that zeolite can improve the purification capacity of both porous asphalt mixture and asphalt mortar. Moreover, the purification performance of zeolite modified porous asphalt mixture were further analyzed with respect to other factors such as suspended solid (SS) particle, pollutant concentration and rainfall intensity. Removal effectiveness increased with SS size and concentration but decreased for COD, Zn, and Pb under high pollutant concentrations or intense rainfall, due to saturation and shortened filtration time. These findings highlight the potential of zeolite-modified porous asphalt mixture as a sustainable and multifunctional solution for urban stormwater management.