Thermal Conductivity of Pervious Concrete for Various Porosities

Thermal conductivity (K) of pervious concrete specimens was measured using the heat-flow meter and the thermal needle probe methods. The two test methods were first conducted on 285.75 mm (11.25 in.) dry square slabs with varying porosities (f) from 19 to 36%. Strong linear K-phi relationships were obtained based on both methods. On average, K for the slabs was 0.50 W/(mK) using the heat-flow meter, and 0.62 W/(mK) by the needle probe. Using the needle probe, 4% water in the slabs resulted in a 20% increase in K. One-hundred millimeter (4 in.) diameter cylinders were saw cut in half and were tested for K at the top and bottom. K-phi were obtained for the cylinder halves using the needle probe. The mean geometric model showed a near-perfect fit for the slabs in dry conditions. The model fit reasonably well to the top cylinders' K and overestimated K for bottom cylinders with a mean square error of 0.012 W/(mK).