Green Concrete

Posted on Monday, April 18, 2005 in Construction

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Green Concrete

Green Concrete

Paved surfaces, which are so widespread and common that few of us think much about its effect on water quality and the environment. The reality is that as more land is paved, more rainwater falls on the pavement instead of bathing in the soil. Traditional techniques paving to create "impervious" surfaces, ie surfaces that can not be penetrated by water. The results of an increasing amount of impervious surface, erosion, flooding, groundwater depletion and pollution.

The obvious solution to these problems would be to simply stop installing surfaces waterproof. If only it were that easy. But wait! What if there was a material that was as durable as traditional paving techniques that capture rain water and allow to percolate to the ground below? What if there was a material that would really help percolation instead of preventing it? This material exists really. It's called pervious concrete, also known as porous or permeable concrete.

Pervious concrete is a mixture of coarse aggregate, cement and water. Contains little or no sand. The cement and water create a thick paste binding the aggregate particles together, but with many gaps and spaces between them. This creates a system of high permeability, connected voids, usually 15% to 25% of the structure, that drain very quickly. Pervious concrete allows 3 to 8 liters of water to pass through each square foot of material per minute, although the wording may be changed to double that amount if necessary.

The strength of pervious concrete is limited due to the high porosity, but strong enough for many applications such as hardscaping, low volume pavements, alleys and driveways, low water crossings, parking lots, sidewalks and paths, patios, etc.

Pervious concrete has the capability to help recharge groundwater and reduce stormwater runoff. In so doing, it reduces the need for retention ponds, grooves and other techniques for stormwater management.

An excellent example of the use of pervious concrete is City of Chicago. The city has 1.900 miles of public streets, the equivalent of 3,500 hectares. Most have neither drainage structures or a connection sewerage network. After years of degradation, localized flooding became a problem. As a result, the city developed the Chicago Green Alley Program to use and promote best management practices in stormwater management. The aim was to address drainage problems and no improvements of sewerage infrastructure expensive.

To achieve is objective, the Green Alley Program combined sustainable building techniques, such as recycled materials, reflective pavements, efficient lighting and permeable paving to reduce the amount of stormwater runoff put into the system of storm drains by 80%, reduce localized flooding, and reduce the effect urban heat island.

Light colored pervious concrete, made with recycled materials, was chosen as a component of this program for durability and environmentally sustainable properties. In this situation, pervious concrete allows stormwater runoff to percolate into the soil and reduce the burden of stormwater entering the sewer system of the city.

Engineers and architects are beginning to view pervious concrete as the preferred method of managing rainwater. The ability to manage stormwater on confined commercial sites without retention or detention centers, also offers developers an advantage. Residential developers are also beginning to find ways to use pervious concrete for environmental projects, while reducing costs. Instead of paying for the infrastructure to move to facilities stormwater retention, these developers can allow nature to replenish the water table directly. The reduction or even elimination of retention facilities allows these developers to reduce costs while providing additional space for green space.

In Michigan, a homeowner had a poorly constructed road which caused minor flooding in the garage. The traditional solution would be to start the journey complete upgrading and reinstalling. The contractor involved however, suggested removing only 1 / 6 of the driveway near the garage and putting in concrete permeable to solve the problem. The water has flooded the garage now flows through the pervious concrete on the floor below. This solution cost only a fraction the cost of the alternative.

Acceptance of pervious concrete has become widespread. The EPA now recommends pervious concrete as a best management practice for manage stormwater runoff at the regional and local levels. In addition, the National List Mixed Concrete Association (NRMCA) now has a nationwide program in place to certify contractors in the installation of pervious concrete.

About the Author:

Mary Smith is a freelance writer. She heard about pervious concrete from the talented design team at Florida Engineering Solutions. They do structural engineering design, not construction. When you need prestressed / precast concrete design, remember FES smart structural design.

Article Source: ArticlesBase.com – New Eco-Friendly Concrete Leaks In a Good Way

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