Permeable Pavement as a Hydraulic and Filtration Interface for Urban Drainage

Permeable pavement, specifically cementitious permeable pavement (CPP), is a passive structural low impact development material and green infrastructure system for rainfall-runoff control. Multifunctional engineered CPP can fulfill requirements as a load-transmitting surface while serving as a more environmentally conscious infrastructure material that functions to restore the in situ hydrology while also functioning as a passive treatment unit operation and process. As an infrastructure material; CPP reduces runoff, filters, and treats infiltrating runoff, reduces thermal pollution and temperature, provides the load-carrying capacity of conventional rigid concrete pavement, and leaches environmentally beneficial Ca and alkalinity, as compared to flexible asphalt. In this study, pore characteristics of CPP, including effective porosity (ϕe), pore size distribution and tortuosity (τ) are examined using x-ray tomography and gravimetric-geometric methods. Total porosity (ϕt) is measured and utilized as a comparative index. Results provide insight when modeling CPP as an infiltration and evaporation interface, a conveyance/storage medium for liquid and gas, and with admixtures or coatings an adsorptive-filtration medium for pollutants such as phosphorus and metals. Results indicate that high particle separation and significant hydraulic conductivities can be achieved with CPP. The effectiveness of CPP for particle removal also requires that these particle deposits are managed on a periodic basis through practices such as pavement cleaning.