Pervious Concrete A Solution to Stormwater Runoff

Lionel Lemay, Sr. Vice President, Sustainable Development, National Ready Mixed Concrete Association. and
Colin Lobo, Sr. Vice President, Engineering, National Ready Mixed Concrete Association

Introduction

Pervious Concrete A Solution to Stormwater Runoff

Figure 1: The cement and water in pervious concrete forms a paste that uniformly coats and bonds the aggregates together when properly compacted but creates an interconnected void system that allows water to pass through it.

Pervious concrete is a mixture of hydraulic cement, coarse aggregates (stone), water and admixtures. American Concrete Institute (ACI) Committee 522 describes pervious concrete as a "near zero-slump, open-graded material consisting of hydraulic cement, coarse aggregate, little or no fine aggregate, admixtures, and water.”1 The cement and water in pervious concrete forms a paste that uniformly coats and bonds the aggregates together when properly compacted. An optimized quantity and consistency of paste is used in the mixture to allow the fresh pervious concrete mixture to flow adequately when placed and to obtain point-to-point contact of the coarse aggregates, creating an interconnected void system to allow stormwater to infiltrate through the pavement system when installed. A typical pervious concrete mixture will contain between 15 and 25% void content within the concrete. The drainage rate of pervious concrete pavement will vary with aggregate size and density of the mixture, but will generally fall into the range of 0.2 cm/s (288 in./hr) to .54 cm/s (770 in./hr)².