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Grasscrete: Sustainable Urban Drainage Product

| Friday December 7th, 2007 | 0 Comments

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Grasscrete, the green alternative to standard concrete surfaces for parking lots, driveways, and access roads for vehicles or fire trucks. The benefit to Grasscrete for businesses and developers is that it drains at about the same rate as would an ordinary lawn in the same location. The presence of concrete has little effect on the drainage; the soil and the slope are the controlling factors which makes it beneficial for erosion control as well.
The idea is a simple one, the surface area of Grasscrete is 47% concrete and 53% holes (to be filled with Grass). Grasscrete is a pervious reinforced concrete structure for all types of areas that require traffic, either foot or wheel. Grass will generally spread and cover much of the concrete in areas not subject to regular vehicle traffic. Holes may also be filled or covered with crushed stone, seashells, and a wide variety of other drainable materials in cases where grass is not desired.


Grasscrete is made by pouring concrete over “Formers” which is a mold that leaves voids in the concrete. Grasscrete Formers come in two types. A re-usable plastic tool that is used only for fully grassed or concealed installations or the more common single-use Molded Pulp Former used for all Grasscrete types.
The Molded Pulp is made up of 100% recycled paper sourced from both post industrial and post consumer waste streams. The pulp is suspended in a water slurry and vacuum formed to a mold. The mold is then air dried to form a solid product. This material is based on the same biodegradable material commonly found at nurseries that plant pots are made from. Individual Grasscrete Formers are 24″ x 48″ in outside dimension and are 5 ¬Ω” deep and every square foot of properly installed Grasscrete is connected with steel reinforcement.
Grasscrete is installed over a sub-base of gravel at a depth determined by the load bearing capacity required for the project. On site re-cycled fill materials are used in the sub-bases together with the use of topsoil in paving and retaining wall systems: as this is often available surplus from the excavation work it helps to avoid the unnecessary off-site disposal of waste materials.
Grasscrete can also be installed over native soils saving money on excavation and gravel. The subsurface all depends on the needs and the water runoff requirements, from thick beds of stone to water piping systems. Grasscrete, as with many other “green” products generally costs 30% higher than traditional concrete pavement. At times however, using Grasscrete can eliminate or minimize the need for storm water collection systems which may in turn lead to substantial savings.
Contrary to convention, the structural advantages that Grasscrete offers over pre-cast can make significant savings in both the “construction” and “lifetime” costs of a project. Sub-base depths are reduced and curb edge restraints can often be eliminated. The construction process is much faster than for precast and the forms can be delivered by the truckload to cover 7200 sq m which is the equivalent to fifty truckloads of pre-cast. This is a serious statistic that saves both money and polluted transportation waste.
SUDS, better known as ‚ÄòSustainable Urban Drainage ‘is becoming an increasingly used term with planners and developers seeking to mitigate the implications of handling surface water run-off on the local storm water network. Although the use of pre-formed tanks is a fairly recent innovation, grasscrete has developed and pushed “on-site” solution to storm water management. Pre-formed tank water management often involves the use of self-draining paving layers together with the installation of pre-formed sub-ground retention tanks, to store surface water for a controlled release into the drainage network. Grasscrete believes that a more uniform percolation process will create a more natural balance thereby reducing the risk of shrinkage in clay soils due to the urbanized modification of water tables.
Some other benefits to the Grasscrete concept include the improved reflectance of the crete as compared to blacktop, reducing the heat island effect. Grasscrete handles runoff and storm drainage via river training, slope protection and channels. It is also a sound product for retaining pond bottoms thanks to its pervious nature and helps provide a food source and cover for pond inhabitants. All in all grasscrete is a great product for the proper application depending upon one’s needs.


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