7 Great Reasons to choose Permeable Concrete
Permeable Concrete, or pervious concrete is changing the way public spaces are landscaped.
Concrete is the second most consumed product in the world. And contrary to our belief, its usage is much wider than constructing buildings only. With recent developments in concrete, it has become an important material for an array of usages. Permeable Concrete is a prime example of development in the concrete industry. Although the material itself isn’t new, since it was first used in 1852, it has been attracting renewed attention.
Land changes through urbanisation
One change that urbanisation has brought is the increase in pervious coverings on the land in cities and suburbs. The water that falls needs to go somewhere, and pervious covering means rapid runoff into streams and rivers. This can lead to an increase in flooding for towns downstream. One way to reduce the rapid runoff is through the use of permeable concrete.
https://youtu.be/ERPbNWI_uLw
What is Permeable Concrete?
Permeable Concrete is also known as Porous Concrete, Pervious Concrete, Gap Graded Concrete, No-Fines Concrete and Enhanced-Porosity Concrete. Permeable concrete, similar to Normal Concrete, uses a mix of cement, water, and coarse aggregate with little or no sand (Fine Aggregate) in it. The resulting concrete has 15% to 25% voids, which ensure a water flow rate of 0.2 to 0.5 cm/s. Although the higher porosity and lack of mortar paste reduces the strength of pervious concrete as compared to conventional ones, the strength is sufficient for most uses.
https://youtu.be/Ml7hDu1fOqM
What are the Applications of Permeable Concrete
Although Pavement Construction is the major application of pervious concrete since it reduces the stormwater runoff and adds to the surface water table. In fact, the usage of permeable concrete in pavement construction is considered one of the Best Management Practices (BMP) by the Environment Protection Agency (EPA).
The usage of Permeable Concrete in pavements and in other horizontal constructions, depending on the precipitation values of a certain region, can eliminate the need for retention ponds and other precipitation runoff storage facilities. This would result in more efficient land use, especially in urban areas where land is already expensive.
Below are some of the many applications in modern landscaping;
- Residential Roads and Driveways
- Parking Lots
- Pavements with low traffic volume
- Tennis Courts
- Sub-base for conventional concrete pavements
- Artificial Reefs
- Well Linings
- Slope Stabilisation
- Swimming Pool Decks
- Pavement Edge Drains
Production of Pervious Concrete
Production of Permeable Concrete is very similar to that of normal concrete since it uses the same ingredients. However, the amount of ingredients differ. Pervious Concrete is also mix-designed and therefore should be designed for the desired purpose.
A general guideline is listed in the table below.
Table 1 Typical Mix Proportion for Pervious Concrete (Divya Bhavana et al., 2017)
| Material | Quantity (kg/cubic metre) |
| Cement | 270 to 415 |
| Aggregate (Coarse and Fine) | 1190 to 1480 |
| Water to Cement Ratio (by mass) | 0.27 to 0.34 |
| Aggregate to Cement Ratio (by mass) | 4 to 4.5 |
| Fine to Coarse Aggregate Ratio (by mass) | 0 to 1 |
This typical guideline is for information only, and therefore a trial mix should always be prepared and checked for the desired purpose. Apart from the usual materials, Supplementary Cementitious Materials (SCM) and chemical admixtures are also used as per the dosage mentioned by the manufacturers.
Water to Cement Ratio for Permeable Concrete
A lower water to cement ratio is used since higher water to cement ratios would affect the compressive strength of concrete. If compressive strength is not important, a higher water to cement ratio can be used.
The use of Fine Aggregate will reduce the permeability of concrete and make it less porous. However, the compressive strength would be improved.
Lightweight aggregate, recycled aggregate, and other types of aggregate or other techniques like fly ash geopolymer concrete have also been utilized to make Permeable Concrete.
Characteristics of the Concrete
Although it is similar to Normal Concrete in terms of its ingredients, there are a multitude of characteristics that make this concrete different.
Some characteristics of Hardened and Green (Fresh) Permeable Concrete are as follows:
The Permeable Concrete has a textured surface after placement.
* In-place densities are usually 1600 kg/m^3 to 2000 kg/m^3
* Due to low or no mortar content, Permeable Concrete renders a lower slump value and a stiffer consistency. Slump values are usually less than 20 mm (0.75 inches).
* In spite of the higher void percentage, the Permeable Concrete can render a compressive strength of 3.5 MPa to 28 MPa. Typical values are about 17 MPa
No Darby, Trowel or Bullfloat is used since they tend to seal the surface of concrete.
7 Benefits of using Pervious Concrete in Commercial Landscaping.
1. Permeable Concrete is much more than a way to reduce stormwater runoff in urban areas. Listed below are some benefits of using Permeable Concrete.
2. It reduces pollution by allowing the water to percolate into the ground. The sand chemistry and biology are allowed to treat the water naturally.
3. Allowing the rainfall to percolate allows it to recharge ground water and aquifers.
4. It improves land use, especially in Urban Areas
5. The light colour of Concrete and its relatively open pore structure absorb and store less heat, respectively, when compared to Normal Concrete. This helps in lowering heat in urban areas.
6. It is difficult for trees planted in parking lots and footpaths to grow in impervious concrete environments since it makes it difficult for water to reach the roots. Street trees benefit from Permeable concrete and further reduce the heat in urban areas.
7. It eliminates the risk of ponding over the roads over longer periods of time, as is observed in some developing countries after rainfall.
8. The pervious concrete can absorb the noise of the vehicles on the road, creating a pleasant environment.
9. On rainy days, pervious concrete pavements do not have splashes and puddles, which glisten at night and are dangerous for drivers.
As per recent researches, the permeable concrete can also be used for the purification of sea water.
https://youtu.be/vs6cmSfs5AU
Permeable Concrete as a Filter
According to the US EPA, permeable pavements can help filter out pollutants that contribute to water pollution. The porous structure of pervious pavement allows stormwater to percolate into the underlying soil while filtering out harmful sediments, resulting in better stormwater quality. Studies have shown that, as well as preventing larger plastic pollution being washed into the stormwater, permeable concrete can reduce pollution from microplastics and microrubber.
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References and Further Reading
Divya Bhavana, T., Koushik, S., Uday Mani Kumar, K., & Srinath, R. (2017). Pervious concrete pavement. In International Journal of Civil Engineering and Technology (Vol. 8, Issue 4). https://doi.org/10.3141/2113-02
Park, S. B., Lee, B., Lee, J., & Jang, Y. Il. (2010). A study on the seawater purification characteristics of water-permeable concrete using recycled aggregate. Resources, Conservation and Recycling, 54(10), 658–665. https://doi.org/10.1016/j.resconrec.2009.11.006
Yang, J., & Jiang, G. (2003). Experimental study on properties of pervious concrete pavement materials. Cement and Concrete Research, 33(3), 381–386. https://doi.org/10.1016/S0008-8846(02)00966-3
