By: Erin Ashley, PhD
Director of Codes and Sustainability, NRMCA
As appeared in Concrete InFocus, a publication of NRMCA, Winter 2008
“Pervious concrete is a unique and innovative means to manage stormwater. When pervious concrete is used in building site design, it can aid in the process of qualifying for LEED Green Building Rating System credits.”
“Pervious pavements function like storm water retention basins and allows the stormwater to infiltrate the soil over a large area, thus facilitating recharge of precious groundwater supplies.
Pervious concrete has been used successfully in many types of construction on applications such as parking lots, streets, plazas, nature trails, and walkways. While pervious concrete can be used for a surprising number of applications, its primary use is in pavement. Pervious concrete is a performance-engineered concrete made with controlled amounts of aggregates, water and cementitious materials to create a mass of aggregate particles cover with a thin coating of paste. A pervious concrete mixture contains little or no sand, creating a substantial void content. Using sufficient paste to coat and bind the aggregate particles together creates a system of highly permeable, interconnected voids that drains quickly. Typically, between 15% and 25% voids are achieved in the hardened concrete, and flow rates for water through pervious concrete are typically around 480 in./hr (0.34 cm/s), although they can be much higher. Both the low mortar content and high porosity also reduce strength compared to conventional concrete mixtures, but sufficient strength for many applications is readily achieved.”