To make pervious concrete, carefully controlled amounts of water and cementitious materials create a paste that forms a thick coating around aggregate particles. A pervious concrete mixture contains uniformed sized aggregate 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, which is 5 gal/ft²/ min or 200 L/m²/min), although they can be much higher. The low paste content and high voids reduce strength compared to conventional concrete mixtures, however, sufficient strength for heavy duty applications is readily achieved.