PERVIOUS CONCRETE
Pervious Concrete is a special type of concrete that has a high porosity so that water can percolate through it easily. The major advantage of this type of concrete is that it can be used in the areas where it is very important to remove the stagnant and there is no proper draining facility for removal of water.
The pervious concrete is made only by implementation of course aggregates and cement for binding the aggregates. The fine aggregates are not used so that the pores between the course aggregates are not blocked. This pore serves as a gateway for the water to percolate through the concrete substrate.
Pervious concrete is used in parking area, subways and residential streets and walkways. The pervious concrete s used in a wide range for stromwater management. It is one of the sustainable product and concrete of future generation.
History Pervious concrete was first used in the 1800s in Europe as pavement surfacing and load bearing walls. It can also reduce city temperatures and alleviate urban hot island phenomena. Pervious concrete was first invented in Britain in 1824. It was first introduced into the United States in the mid-1970s and has since been rapidly developed. The Sponge City was introduced in China in approximately 2012.
Need of Pervious Concrete A large amount of rain water ends up falling on impervious surfaces such as parking lots, drive ways, sidewalks rather than soaking into soil. This creates an imbalance to the natural ecosystem and leads to the host of problems such as erosion, flood, and groundwater level depletion and pollution of rivers. The best solution to avoid this is to alter the impervious construction surface such as concrete and asphalt by the pervious concrete. Pervious concrete also acts as a filter which removes the debris from the flood to enter into the rivers and ground water and recharge the water level.
Properties of Pervious Concrete It has just enough cement paste to bind the aggregate with each other. The aggregates that are used should be only course aggregate and fine aggregate is avoided.
Fresh Concrete Property: The plastic pervious concrete mixture is stiff compared to traditional concrete. The slump that is measured is 30 mm which is enough for placing the concrete.
However, slump of pervious concrete has no correlation with its workability it is not be specified as an acceptance criterion.
Hardened Concrete Property:
The density of the concrete is found to be 1800 kg/M3.
The void contents of the pervious concrete ranges from 20 to 25%.
Permeability:
Typical flow rates for water through pervious concrete are 120 L/m²/min.
Application
1.Low-volume pavements and parking lots
2.Residential roads, alleys, and driveways
3.Sound barriers
4.Slope stabilization structures
5.Sidewalks and pathways
6.Patios, tennis courts, swimming pool decks
7.Pavement edge drains and gutters
8.Seawalls, reefs and other hydraulic structures
9.Sidewalks and pathways
10.Foundations / floors for greenhouses, fish hatcheries, aquatic amusement centers, and zoos
11.Swimming pool decks
Benefits
1.Reduces runoff from site.
2.Helps in unchanging ground water.
3.Eliminates need for retention ponds & other costly storm water management practices.
4.Provides for more efficient use of land development.
5.Water resources are conserved.
6.Adjacent trees and vegetation are allowed more rainwater.
7.The permeability of pervious concrete provides increased safety for drivers