Laboratory evaluation of permeability of porous asphalt concrete

The permeable features of porous asphalt concrete (PAC) depends on the porosity of pavements; however, the functional life of PAC might gradually decrease due to clogging. Dust and debris could fill the void structure, causing the PAC layer to become clogged. In order to design porous asphalt concrete that is less susceptible to clogging, it is important to evaluate the influence of pavement thickness, bonding materials and air void reduction on the functionality of PAC. Experimental tests conducted in this study included constant head, variable head, horizontal, and vertical permeability, and pore clogging. Results indicated PAC made of various types of asphalt showed no significant difference in the coefficient of permeability. The addition of fibers in PAC had little impact on its permeability. The increase in specimen thickness led to an increase in the amount of water permeable into PAC. The horizontal permeability (K_H) was greater than the vertical permeability (K_V). When the K_H value was lower than the K_V value, it was likely to result in clogging. The permeability coefficient of PAC decreased with the increasing content of clogging materials. The greater the PAC specimen thickness, the higher reduction in the permeability coefficient. After several clogging and cleaning periods of testing, the permeability of PAC gradually reached a stable value.