Pervious concrete, also known as porous or water-permeable concrete, is a unique material designed to allow water or air to pass through its large voids. With pore sizes ranging from 2 to 8 mm and a void content of 18 to 35 percent, this concrete offers distinct advantages, particularly in pavements. In this article, we delve into the various aspects of pervious concrete, from its historical roots to its applications and environmental benefits.
Porous concrete traces its origins back to Europe in the 1800s, initially used as a pavement surface. However, it gained prominence in the United States during the 1970s and saw increased demand post-World War II when conventional cement supplies were disrupted. Surprisingly, India embraced the benefits of this innovative concrete only in the 2000s.
Pervious concrete offers a range of benefits, making it an attractive choice for sustainable development. Let’s explore some of its advantages in detail:
Groundwater Recharge : The permeability of pervious concrete allows stormwater to seep into the ground, contributing to increased groundwater levels.
Reduction in Surface Run-off : By enabling water to penetrate the ground, porous concrete significantly reduces surface run-off, mitigating drainage system costs.
Reduction of Sewers : With diminished stormwater run-off, there’s a decreased need for large stormwater sewers, resulting in cost savings.
Development of Trees : The increased moisture content from infiltrating stormwater, coupled with air circulation through the concrete voids, creates a conducive environment for the growth of trees and plants.
Filtering of Stormwater : Pervious concrete acts as a natural filter, trapping dirt in its voids and allowing only clear water to reach streams, ponds, or lakes.
While pervious concrete boasts several advantages, it does have its limitations, such as being unsuitable for heavy traffic pavements, requiring longer curing times, and necessitating specialized construction practices. Regular cleaning is also essential to maintain its permeability.
The functionality of pervious concrete lies in its ability to allow water to flow through. The permeability depends on void percentage and size. The absence of fine aggregates creates a grainy-textured surface, offering higher friction for vehicle tires, making it suitable for various weather conditions.
However, the concrete’s effectiveness can be hindered by contaminants in stormwater, necessitating cleaning methods like vacuum suction or pressure washing.
Creating pervious concrete involves a mixture of cement, coarse aggregate, and water, with minimal to no fine aggregates. The void content, water-cement ratio, and choice of materials influence its strength and permeability. Recycled materials, including old concrete, contribute to environmental sustainability.
Pervious concrete may have lower strength compared to traditional concrete, but it is sufficient for driveways and parking loads. Special mix designs can enhance its strength, and proper construction techniques ensure durability, with a lifespan of 20-40 years.
While the initial installation cost of pervious concrete may be higher than regular concrete, its long-term cost-effectiveness arises from reduced stormwater control requirements and minimal upkeep. Comparing costs per square foot, pervious concrete competes favorably with porous asphalt, offering a sustainable alternative.
In conclusion, pervious concrete emerges as a viable solution for urban areas, addressing multiple environmental challenges. Its strength, durability, and comparable lifetime costs make it an appealing choice. Although its use in India is currently limited, overcoming hurdles like expertise and study material availability could pave the way for widespread adoption, considering its cost-effectiveness compared to existing paving systems. The endorsement of permeable pavement by the US Environmental Protection Agency further solidifies its standing as an industry best practice.
