PerviousConcrete - Pervious Concrete 2008 Page 1 PERVIOUS...

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Pervious Concrete 2008 Page 1 PERVIOUS CONCRETE PAVEMENT Pervious concrete pavement is a unique cement-based product whose porous structure permits a free passage of water through the pavement into the soil without compromising the pavement’s durability or integrity. This concrete also goes by other names including “permeable” and “enhanced porosity.” As a generic material, all have been recognized by the U.S. Environmental Protection Agency as a storm water pollution prevention (SWPP) Best Management Practice device. Pervious concrete pavement is a mixture of Portland cement, pea gravel, and water. It is ordinary concrete without the sand. Because of the absence of sand, the void space is between 15% and 30%, which makes the material look a bit like a rice cake. This allows water to percolate through the pavement to the subsoil beneath. Pervious concrete is not a proprietary product ; it is a "recipe" for concrete which can be made to order by any concrete batch plant. Pervious concrete is installed without rebar; the thickness is minimum 6 inches for most applications. Pervious concrete has a 15-30% void structure, allowing for 3-8 gallons of water per minute to pass through each square foot. There are five advantages of pervious pavement: Water treatment by pollutant removal. Less need for curbing and storm sewers. Provides a means to recharge local aquifers. Less mass grading is required to create drainage gradients; pervious concrete is ideal for flat areas. Reduced retention/detention pond volume requirement.
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Pervious Concrete 2008 Page 2 The U.S. EPA requires that the first ¾” of rain each day (called the “ first flush ”) be kept on site until treated. Much like a grassy swale or retention pond, pervious concrete paving mitigates first flush pollution and manages storm water via infiltration. The large surface area captures and aerobically degrades much of the hydrocarbon residue – soil bacteria degrade the remainder. Long-term studies of pollutant removal in Rockville, MD and Prince William, VA reported removal efficiencies of 85-92% for sediment, 65% for total phosphorous, and 80-85% for total nitrogen. High removal rates were also reported for zinc, lead, and chemical oxygen demand at the Rockville, MD site. Pervious concrete pavement has a voids content of 15 – 25% equating to a flow rate of 3 – 8 gal/in/sq ft or 270 – 450 in/hr. When pervious concrete paving is used as an infiltration alternative to the more traditional SWPPs such as grassy swales and drain invert filtration systems, the pervious concrete pavement can also reduce or eliminate the need for expensive sewer tie-ins while providing the inherent durability, safety, and low life-cycle cost expected of concrete pavement. A 6-in pervious pavement section with 15% voids will hold 5 gal/sq yd.
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  • Spring '11
  • Stroh
  • American Concrete Institute, pervious concrete, Concrete Pavement Webb Bridge Park, National Ready-Mix Concrete Association

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PerviousConcrete - Pervious Concrete 2008 Page 1 PERVIOUS...

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