Pervious concrete is mixed by eliminated most or all fine aggregates from the mixture. Pervious pavements are used to allow storm water to percolate through their cavity, and to some extents, to allow roots and soils under the pavement respiring. The gas permeability of pervious concrete is thus important to the soil breathing under pervious pavements.
In pervious concrete, carefully controlled amounts of water and cementitious materials are used to create a paste that forms a thick coating around aggregate particles. A pervious concrete mixture contains little or no sand, creating a substantial void content. Using sufficient paste to coat and bind the aggregate particles together creates a system of highly permeable, interconnected voids that drains quickly. Typically, between 15% and 25% voids are achieved in the hardened concrete, and flow rates for water through pervious concrete typically are around 480 in./hr (0.34 cm/s, which is 5 gal/ft2/ min or 200 L/m2/min), although they can be much higher. Both the low mortar content and high porosity also reduce strength compared to conventional concrete mixtures, but sufficient strength for many applications is readily achieved.
Applications for Pervious Concrete
- Low-volume pavements
- Residential roads, alleys, and driveways
- Sidewalks and pathways
- Parking lots
- Low water crossings
- Tennis courts
- Subbase for conventional concrete pavements
- Artificial reefs
- Slope stabilization
- Well linings
- Tree grates in sidewalks
- Foundations/floors for greenhouses, fish hatcheries,
- aquatic amusement centers, and zoos
- Hydraulic structures
- Swimming pool decks
- Pavement edge drains
- Groins and seawalls
- Noise barriers
- Walls (including load-bearing)
How to Produce
Pervious concrete consists of cement, coarse aggregate and water with little to no fine aggregates. The addition of a small amount of sand will increase the strength. Water to cement ratio of 0.28 to 0.40 with a void content of 15 to 25%. It can be mixed by hand or machine, for large demand, or HZS concrete batching plant can produce ready mix pervious concrete capacity from 25-240 cubic meter per hour.