Q: I’m considering pervious concrete for the driveway on an upcoming project. What exactly is pervious concrete? Does it require extra maintenance to keep it functioning?
A: Peter Zoni, sales manager at Cape Cod Ready Mix, in Orleans, Mass., responds: Pervious concrete is a mix of Portland cement, coarse aggregate, water, and admixtures. Because there is little or no sand in the mix, the concrete contains bigger voids than ordinary concrete. These voids let water and air pass through, allowing pervious concrete to drain huge amounts of runoff for long periods of time.
Pervious concrete is not a new product, but recently it’s been gaining popularity because of its unique properties. First off, it’s a great solution to many federal stormwater-management requirements regarding paved surfaces such as driveways. Because water percolates naturally through the material into the water table, using pervious concrete may eliminate the need for water-retention ponds and complex drainage systems, saving all the associated costs of engineering and installation.
Pervious concrete is also strong and durable. Our company has developed a pervious-concrete product, called Perk-Crete, that we recently installed on a 200-foot driveway that runs up a 15-degree slope to a horse farm. The driveway produces zero runoff and is strong enough for any traffic it will see.
Installation of pervious concrete must be done by trained and certified professionals following specific placement guidelines, including those for preparing the base to drain the water that passes through the concrete.
Because of its strength and durability, pervious concrete is resistant to damage from freezing and thawing. It’s at risk for freeze-thaw damage only when the voids in the concrete become clogged and water no longer drains through. If this happens, pressure washing or vacuuming may be needed. But anecdotally, I’ve had a pervious-concrete driveway for years and have never pressure-washed or vacuumed it, and water still drains through it like the day it was installed.
