Pervious concrete pavement is a unique and effective means to address important environmental issues and support green, sustainable growth.
By capturing stormwater and allowing it to seep into the ground, porous concrete is instrumental in recharging groundwater, reducing stormwater runoff and meeting U.S. Environmental Protection Agency stormwater regulations. This pavement technology creates more efficient land use by eliminating the need for retention ponds, swales and other stormwater management devices. In doing so, pervious concrete has the ability to lower overall project costs on a first-cost basis.
Recently, Peter Doyle, owner of the Alpine Butcher Shop in Lowell, Mass., chose to use pervious concrete for a 15,000 square-foot parking lot at the company's new retail building project. Doyle chose Kingston Ready Mix for the project after salesman Tim Latham approached Doyle with the Pervious Concrete concept.
The next step for Latham was to introduce pervious concrete to the project engineer, as well as the City of Lowell.
"We developed a presentation to give to the Conservation Group in the City of Lowell," Latham said. "We had a small test cylinder of pervious concrete that we poured water through."
That was proof enough. One conservation official thought it was "too good to be true."
In order to keep to the construction schedule, the parking lot was placed in a series of strip placements which allowed open access to the project. In order to save time, pervious concrete was also placed up against curbs and edges to make pervious placements easier and more uniform.
Ready mix trucks delivered the pervious concrete to the job site and finishers then screened out and floated the material and then rolled it with a weighted roller to compact the surface. The final step was to cover the pervious with a light gauge plastic and wet cure the material for a period of seven days.
When pouring pervious concrete, carefully controlled amounts of water and cementitious materials are used to create a paste that forms a thick coating around aggregate particles. The mixture contains little or no sand, 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. Both the low mortar content and high porosity also reduce strength compared to conventional concrete mixtures although sufficient strength for many applications is readily achieved.