Pore-structure models of hydraulic conductivity for permeable pavement

Summary Permeable pavement functions as a porous infrastructure interface allowing the infiltration and evaporation of rainfall–runoff while functioning as a relatively smooth load-bearing surface for vehicular transport. Hydraulic conductivity ( k ) of permeable pavement is an important hydraulic property and is a function of the pore structure. This study examines k for a cementitious permeable pavement (CPP) through a series of pore-structure models. Measurements utilized include hydraulic head as well as total porosity, ( ϕ t ), effective porosity ( ϕ e ), tortuosity ( L e / L ) and pore size distribution (PSD) indices generated through X-ray tomography (XRT). XRT results indicate that the permeable pavement pore matrix is hetero-disperse, with high tortuosity and ϕ t  ≠  ϕ e . Power law models of k – ϕ t and k – ϕ e relationships are developed for a CPP mix design. Results indicate that the Kruger, Fair-Hatch, Hazen, Slichter, Beyer and Terzaghi models based on simple pore-structure indices do not reproduce measured k values. The conventional Kozeny–Carman model (KCM), a more parameterized pore-structure model, did not reproduce measured k values. This study proposes a modified KCM utilizing ϕ e , specific surface area (SSA) pe and weighted tortuosity ( L e / L ) w . Results demonstrate that such permeable pavement pore-structure parameters with the modified KCM can predict k . The k results are combined with continuous simulation modeling using historical rainfall to provide nomographs examining permeable pavement as a low impact development (LID) infrastructure component.