Sustainable material －POROUS PAVEMENT
-- OPEN-JOINED PAVING BLOCKS Introduction:
This essay will focus on the application of open-joined paving blocks to minimize the impact of urban development on natural drainage system-capturing, slowing and absorbing storm water in the urban condition. In the natural system, 10% surface flow,30% evapotranspiration, 40% infiltration, 20% interflow, while in an urban condition, 75% surface flow to pipes, 15% evapotranspiration, 5% infiltration, 5% interflow1. The unbalanced water distribution when water comes to the ground causing severe problems as flooding and erosion, destroying natural habitat and insufficient fill-in of water table.
Porous pavement could increase the infiltration rate and interflow rate and reduce the overwhelmingly high rate of surface flow. Porous pavement materials include: porous aggrregate, porous turf, plastic geocells, open-joined paving blocks, open-celled paving grids, porous concrete, porous asphalt. Open-joined paving blocks is one of the most commonly used. Open-jointed paving: open-jointed paving blocks are solid units shaped or placed to leave open space in the joins between adjacent units. The blocks are manufactures from concrete, clay or from natural stones or wood. The joins are filled with porous aggregate or vegetated soil. Together, the blocks and joins form a composite surface that can be porous and permeable while bearing traffic loads though the structure. Techniques
What does porous pavement system do and not do?
Pervious paving allows rainwater to either pass through the paving system itself or through joint openings between pavers.2 They are designed to capturing, slowing and absorbing storm water, they cannot treat the pollutants leaking form vehicle on roads. How does it work?
Porous pavement includes pervious surface, bedding layer, reservoir layer and filter layer3: the surface layer directly receives the traffic load and the disintegrating effects of traffic abrasion. It is likely to be made of special, relatively expensive material resist abrasion and provide qualities such as appearance and accessibility. Bedding layer builds up the thickness of a pavement with comparatively protect the subgrade from frost penetration. Reservoir is any proportion of a pavement that stores or conveys water while it exists through a drainage pipe or into the soil. Water infiltrate form the reservoir into the subgrade. It may include a Lateral outlet system- a pipe or any other lateral outlet can discharge excess water from a pavement reservoir safely. Filter layer is the layers inserted between a layer and the subgrade to separate their materials. Porous pavement hydrology4: rainfall or snowmelt infiltrates into the pavements’ surface. Some additional water may arrive as runoff from off-pavement area. Water infiltrating the pavement surface may further infiltrate the subgrade soil; the remainder overflows towards the discharge pipe. Storage in the pavement’s reservoir takes up temporary difference between inflow and outflow. Applicability and History:
The history of this technology dates back to the old concrete block manufacturing of German and Dutch. Today, open-joined models are important part of North America’s concrete industry. With the cooperation of Interlocking Concrete Pavement Institute from German, designers have the option of standard models or develop new models with custom shape, colors and imprints. Properly constructed block pavement can bring traffic loads up to 7200 psi5. it can apply to places like pedestrian-only areas, low-volume roads, low speed areas, overflow parking areas, residential driveways, alleys, and parking stalls. It cannot apply to site like: porous pavements should not be used in high pollutant loading sites. For instance high pollutant loading sites , Places where fuels and chemicals are stored or handled can be potential storm water hotspots, areas subject to...
Bibliography: Ferguson, Bruce K. 2005. Porous Pavements. Integrative Studies in Water Management and Land Development. Boca Raton: CRC Press/Taylor and Francis. http://www.loc.gov/catdir/toc/ecip0421/2004019318.html
Minnesota Stormwater Manual.
EPA: United States Environmental Protection Agency
DCR, 1999, Et seq. Virginia Storm water Management Handbook. http://www.virginiadot.org/business/resources/LocDes/BMP_Design-Manual/Chapter_10_Porous_Pavement.pdf
City of Colorado Springs. Section 2. Pavement Design Criteria Manual
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