If you're looking into paving a new driveway or pathway for your home, or if you're digging out your old one and starting over, you've probably already heard about pervious concrete. In urban concrete jungles, meteorologists and city officials refer to the flooding risk of hard rain pounding on so much cement as “the swimming pool effect.” The water simply has nowhere to drain, so it pools. Pervious concrete is the solution to the swimming pool effect, and it can benefit homeowners in urban, rural, and suburban areas.
How Does It Work?
Pervious concrete is a paving material that is carefully constructed from a paste made of water and cement that is then mixed with aggregate particles, which are usually made of rock. This mixture, unlike the traditional variety, has little to no sand particles, which leaves space around the aggregate rather than forming a solid material. This forms a permeable substance by creating voids through which water can drain. The slight drawback to this option is that it has a reduced strength due to the voids. However, additives can be used to achieve the desired strength, depending on the project.
Flood Prevention
This material can reduce the risk of urban flooding simply by giving the water a place to go. Instead of pooling on top of the surface to create puddles or, worse, flooding, liquid can seep through the substance and into the earth beneath it. Usually, three to eight gallons of liquid can seep through each square foot of pervious concrete every minute, preventing build up.
Runoff Purification
Use of this design in paving is recognized as one of the best practices by the EPA (Environmental Protection Agency) for management of storm runoff. Not only does it reduce pooling, but the cement also acts as a filtering system when the moisture is allowed to seep through the spaces around the aggregate material. For example, the oils left behind from cars is digested by naturally occurring microorganisms as they pass through the voids in the aggregate. What seeps through hits the soil as a much cleaner substance, reducing the negative environmental impact of groundwater.
Where Can It Be Used?
Pervious cement can be used nearly everywhere that the traditional material is used, including in residential paving, roads, alleys, driveways, sidewalks, walkways, patios, foundations for open-area buildings, artificial reefs, and walls. It can even be used in parking lots and boat launch ramps. Just think about any area that you walk or drive through regularly that floods every time it rains.
This new type of paving shows that not all concrete is detrimental to the environment or to water retention management. While this option is still much more expensive than traditional concrete, it may save money in the long run through a reduction of environmentally hazardous runoff and the flooding of cars or houses.
