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Welcome to Charger's World of Pervious Concrete! We are different! We specialize in installing pervious concrete, we don't sub contract it! We don't just write or talk about it, we have over 25 years experience working with pervious concrete! We were the first to put our widely accepted pervious concrete specification on the internet! We are not just builders who occasionally work with concrete. We specialize in pervious and with our experience, we can offer a 10 year warranty on it!
What is Pervious Concrete? Pervious concrete is a porous concrete paving material which permits rain and storm water runoff to percolate through it rather than flood surrounding areas or storm drains. It is usually a mixture of 3/8" to 1/2" average diameter aggregate, hydraulic cement, other cementitious materials, admixtures and water. When properly placed pervious slabs will contain voids that would be filled by sand. Like a honeycomb these voids are held together cement. These irregular voids thus add great strength to the slab. Our designed pervious mixture is the result of over 25 years experience. When cured it resembles popcorn slabs. Pervious Concrete (PC) is not to be confused with Roller Compacted Concrete (RCC). Roller Compacted Concrete is an Impervious Concrete pavement using recycled concrete, local aggregates, Portland cement and water. (RCC) prevents storm water from reaching the aquifer.
Though it is available from many concrete plants, the engineered mixture is only one key ingredient to a porous paving system. Other key factors are: having a suitable base of soil, sand or crushed stone. Having a drainable water table, sufficiently below the pavement is important. Other factors are the proper preparation of an appropriate compacted, sub-base free of all organic matter, the correct concrete mixture, the designed mixing procedure, prompt placement, finishing and proper curing.
Pervious concrete is usually delivered to the site in Ready Mix trucks and mixed at a specified mixing speed to result in 75 to 100 rotations of the mixing drum before discharge. After the closely controlled amount of water is added, one hour is usually the maximum time allowed for discharge. The batch must be placed, rolled, sprayed and covered quickly. This closely monitored process produces a pavement with unique characteristics. This allows it to recharge the aquifer beneath, to prevent puddles, to reduce drainage into storm sewers, streams and adjacent properties. Depending upon base and sub soils some of our competitors claim Pervious Concrete will allow 8 to 12 gallons per square foot per minute to pass through it. This will depend on the sub base and size and type of aggregate. Our tests with a 3/8 aggregate indicate that it will allow 3 to 6 gallons of water to pass through it compared to 2.5 to 4 gallons for Bahia grass. Larger aggregate in an appropriate mix design will drain better.
The demonstration above is a flow of about 6 gallons per minute. Total percolation is also dependent upon base construction, aggregate size and existing soil and water table conditions. Base preparation includes testing existing soil for its ability to percolate. If the water table is at least 4 ft. below grade and septic fields work in the area, probably the permeability of the sub soil will be adequate. The base soil should be appraised by a site engineer. Again we stress All organic materials such as roots, grass, trash must be thoroughly removed. Then compactable, porous sub base should be installed, and compacted with a vibratory compactor to a level of 98% compaction or better. A properly compacted sub base will not be damaged by ready-mix trucks delivering the pervious concrete.
Pervious Concrete resists degradation from stress during curing. Since the Pervious mixture dries with much less shrinkage than most paving concretes, our experience has demonstrated that control joints are needed much less than with conventional concrete. Once cured it does not distort under traffic as does asphalt which often develops ruts and ripples under the hot sun, and the friction from vehicle tires. For more information about Charger’s Pervious work see Better Roads Magazine, April 2002. We are discussed in the second half of the article beginning with the subheading “Opening it up.” Http://www.betterroads.com/articles/apr02c.htm
Because of its open cell structure, Pervious Concrete reduces the reflection of heat into the atmosphere. Unlike asphalt it also absorbs much less heat from the sun (50% to 75%). When it rains it does not heat the storm water runoff like asphalt, which eventually heats the bodies of water into which it is discharged. The rain water retained also cools the air above the concrete, because it acts like perspiration evaporating to cool your skin. When oil or grease drips on to pervious that same open cell structure enables volatiles to evaporate, and remaining solids to pass into the soil below, where microbial activity may consume or convert them. Because of the heavy, strong, Portland cement paste component, it forms strong molecular bonds that grow during hydration. Since most aggregate is porous it forms a mechanical bond as well and creates a pavement with greater strength and durability. If compaction by vibrating screed and rolling is not done quickly this mechanical bond will not be achieved and raveling will occur under traffic. The appropriate thickness for most pavements is 4" to 6". However thicker pavements may be designed for heavy loads. The skills of concrete engineers should be put to use in designing heavy use pavements.
Pervious concrete is an environmentally friendly building material which is quickly gaining recognition as a green building component. Even the Federal and County Governments appreciate it. Two examples are below: A PERVIOUS PARKING LOT WE INSTALLED IN OAKRIDGE, TENNESSEE, AND A NEW PARKING AREA AT TAMPA INTERNATIONAL AIRPORT
Why is Pervious Concrete a better paving material than porous paver Blocks?
UNLIKE PERVIOUS CONCRETE, PERVIOUS PAVER BLOCKS SETTLE AFTER A FEW YEARS.
REFERENCES: California Nevada Cement Promotion Council
Cool Communities Rome, GA
Concrete Promotion Council
Georgia Concrete & Products Association
Mississippi Concrete Association
National Ready Mixed Concrete Association
National Ready Mixed Concrete Association
Pennsylvania Concrete Promotional Council
Rinker Materials -- Pervious Pavement
Southeast Cement Association (PCA)
Southwest Florida Management District Resource Regulation Training Memorandum Pervious Pavement and Underground Vault Surface Water Management Systems by Charles H Miller, P.E Tarmac Ready Mix Concrete (What The Experts Are Saying About Pervious Concrete)
Washington Aggregates & Concrete Association
For More Information Contact:
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