Particle Separation and Hydrologic Control by Cementitious Permeable Pavement

Cementitious permeable pavement (CPP) has the potential to provide in situ particulate, chemistry, and hydrologic control for storm water. The specific aspects of this control that have been the subject of significant interest and discussion are filtration, hydrologic control, and the potential for clogging. This study investigated the behavior of CPP subject to particle loadings for a constant particle size gradation, a sandy silt gradation. Recovered from an 1-75 Cincinnati, Ohio, site subject to runoff loadings, these CPP specimens had similar pore size distributions and effective porosities. The total mass removal efficiencies for the particles were significant, ranging from nearly total removal for medium and coarse sands to greater than 60% removal for fine silt-size particles. With an engineered surface matrix, total phosphorus reductions exceeded 80%. The commensurate turbidity reductions were significant, and the turbidity of the effluent was generally reduced from 50% to 90% of the influent values. In situ hydrologic restoration was significant, generating peak flow reductions and storage within the pore space that represented approximately 25% of the CPP volume, and the temporal aspects of the influent hydrograph were attenuated compared with that for conventional impervious pavement. The initial hydraulic conductivity was in the range of 10(-2) cm/s and followed a first-order exponential decline, and restoration of this hydraulic conductivity required some form of pavement cleaning approximately once every 6-month period. Cleaning by pavement vacuuming restored more than 95% of the initial hydraulic conductivity.