Pervious concrete is a special type of concrete with a very high porosity. This provides a more environmentally friendly hardscape surface by capturing stormwater and reducing the runoff from a site, allowing a gradual groundwater recharge. Pervious concrete is traditionally used in parking areas, areas with light vehicular traffic, residential streets, pedestrian walkways, driveways and greenhouses. It is fast becoming the material of choice for sustainable and ‘green’ construction projects and is one of many low impact development techniques used by builders to protect water quality. Just like regular concrete, pervious concrete is available is a variety of aggregate sizes, colors and can even be stamped.
The pervious concrete mix is composed of cementitious materials, coarse aggregate and water with little to no fine aggregates. A lower water content gives greater structural strength, fewer cracks and a longer working life between 20 and 40 years with little o no maintenance.
Typically pervious concrete has a water to cementitious materials (w/cm) ratio of 0.25 to 0.35 with a void content of 14-25%. This should be poured over an open-graded compacted base, allowing for full water retention and minimal runoff.
The proper utilization of pervious concrete is a recognized Best Management Practice by the U.S. Environmental Protection Agency (EPA) for providing first flush pollution control and stormwater management. Pervious concrete reduces the runoff from paved areas, which reduces the need for separate stormwater retention ponds and allow the use of smaller capacity storm sewers. This allow property onwers to develop a larger area of available properties at a lower cost; all this while naturally filtering stormwater and reducing pollutant loads entering waterways.
Pervious concrete can also reduce the impact of development on trees. A pervious concrete pavement also the transfer of both water and air to root systems allowing trees to flourish even in highly developed areas. This tree to the right had heaving roots, forcing the owner of the project to use a permeable solution - she chose pervious concrete. To see how well it drains, click here.
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