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ceramics.org Keith Dorn Jesse Mefford Hunter Shealy a mixture of coarse aggregate, portland cement, water, and little to no sand. contains no fine aggregates a high porosity concrete used for flatwork applications that allows water from precipitation and other sources to pass directly through, thereby reducing the runoff from a site and allowing groundwater recharge. Structural concrete pavement with a large volume (15 to 35 percent) of empty space to allow water to filter through superhank.co.cc Uses portland or blended cements, coarse aggregates, water and admixtures. Pervious concrete is unique in that it uses little to no sand which causes it to have a open-cell structure where water can easily pass through it Since there is little to no sand, the concrete mixture is weaker than conventional concrete The increased porous structure of pervious concrete also weakens the overall strength of the material The coarse aggregates used in pervious concrete are different from conventional concrete because they use narrow aggregates to avoid particle packing. The relationship between strength and w/c ratio is not readily known unlike conventional concrete iastate.edu It takes in water at a rapid rate of 3 to 5 gallons per minute per square foot of surface area, which exceeds the flow rate needed to prevent runoff during rain events The rainwater may be stored in a coarse gravel layer underneath the pavement or allowed to percolate into the underlying soil. As the water percolates through the open cells of the pavement, aerobic bacteria in the voids help to break down harmful pollutants and chemicals. Its unlikely that a pervious surface will become totally clogged. Reducing erosion and sediment runoff onto the pavement through good design can eliminate most problems. If voids do become clogged, vacuuming or pressure washing of the pavement can restore most of the permeability. profoundit.com Parking lots Boat ramps Sidewalks Water parks Not readily used because relatively unknown durability and strength properties mto.gov.on.ca fredhillmaterials.com pbase.com utexas.edu Cost of pervious concrete is greater than conventional concrete in driveways because it is thicker (6 inches rather than 4 inches) Pervious concrete requires less finish work and maintenance which lowers installation costs. The use of pervious concrete instead of conventional concrete eliminates the needs for: curb and gutter systems, retention basins, underground piping, grading sites. It does not add water to existing sewer systems and increases land utilization. sanjuanislandscd.org Storm water runoff is a leading source of the pollutants entering our waterways and pervious concrete helps to reduce the amount of untreated runoff going into storm sewers. The three most common pollutants pervious concrete helps to prevent are sediment, heavy metals, and hydrocarbons because it acts as a filter. Reduces slickness on roads and reduces hydroplaning to an extent Eliminates standing water and prevents icing in the winter. The majority of pervious concrete pavements function well with little or no maintenance giving it a longer life span. In preparing the site prior to construction, drainage of surrounding landscaping should be designed to prevent flow of materials onto pavement surfaces. Soil, rocks, leaves, and other debris may infiltrate the voids and hinder the flow of water, decreasing the efficiency of the pavement. There needs to be further research in the durability of pervious concrete to better understand the life span with respect to everyday use of this material. Pervious-Impervious Trade-off (PIT) Model was designed at USC to support and explain the focus of using pervious concrete in parking lots in coastal areas. The purpose of the model is “a screening tool for parking lot design to evaluate the potential use of pervious pavements while considering cost, infiltration, peak runoff, and site-specific conditions.” "How Pervious Concrete Works - The Concrete Network." Concrete | Concrete Contractors | Info and Ideas - The Concrete Network. Web. 29 Nov. 2010. <http://www.concretenetwork.com/pervious/how_it_works.html>. "Pervious Concrete- List of Frequently Asked Questions about Permeable Pavement - The Concrete Network." Concrete | Concrete Contractors | Info and Ideas - The Concrete Network. Web. 29 Nov. 2010. <http://www.concretenetwork.com/pervious/faqs.html>. Pervious Concrete Pavement for Green, Sustainable Porous & Permeable Stormwater Drainage. Web. 29 Nov. 2010. <http://www.perviouspavement.org/index.html>. Pervious Concrete Pavement. Web. 29 Nov. 2010. <http://www.pervious.info/>. "Pervious-Impervious Tradeoff (PIT) Model." Department of Civil & Environmental Engineering, University of South Carolina. Web. 29 Nov. 2010. <http://www.ce.sc.edu/DeptInfo/members/faculty/harrison/PIT main web page.htm>.