Investigation on the permeability of porous asphalt concrete based on microstructure analysis

Drainage is an important function in porous asphalt concrete (PAC); however, permeability is decreased gradually due to pores clogging. The aim of this paper is to evaluate the influence of microstructures of pores on anti-clogging performance of PAC. To create different types of pore structures, aggregates with different sizes and shapes were used to form specimens, and a self-designed equipment was employed to measure the permeability and anti-clogging performance of PAC. X-ray CT device scanned specimens before and after clogging test, so the influence of aggregates on pores can be determined, and the relationship between pore characteristics and anti-clogging performance was investigated. The results show that aggregates with different shapes affect pore states obviously, including volume, number and effective porosity, and the permeability of PAC decreases if effective pores are clogged. Clogging happens shortly, and PAC constructed by aggregates with regular shape presents excellent anti-clogging performance. Aggregates with irregular shape cause more tortuous drainage channel compared with regular aggregates, and tortuosity coefficient is an effective indicator that quantifies the complexity of pores and evaluates the anti-clogging performance of PAC.