What Is Permeable Concrete and What Makes It A Green Choice?

by TRP Ready Mix on February 11, 2019

A lone plant grows between narrow concrete walls.

Concrete Suppliers Discuss the Environmental Benefits of Water-Permeable Concrete

Permeable concrete is a special type of concrete that has positive impacts on the environment and is also economically advantageous.

Short of making it from recycled concrete, you can order new permeable concrete mixes from your local concrete suppliers.

If you want to benefit from using permeable concrete for your next concrete project, here’s what you need to know about this type of concrete, and why it’s a greener, more economical choice.

What Is Permeable Concrete/Porous Pavement?

Permeable concrete, also known as pervious concrete or porous concrete, is a structural concrete with a large volume of voids. These interconnected voids make up about 15 to 35 percent of the concrete’s volume.

Similar to regular concrete, concrete contractors make pervious concrete by mixing cement, coarse aggregates, and water. But this concrete mix does not usually contain fine aggregates such as sand or clay, and when it does, it only contains a small amount.

The absence of sand in this concrete mix results in an open-cell (porous) structure that water can easily pass through. And these open voids give the concrete a honeycomb texture.

What are the Various Types of Permeable Pavements?

  • Porous Asphalt – Used on highways to eliminate excess water.
  • Porous Turf – Used for occasional parking areas such as at churches and stadiums.
  • Single-Sized Aggregate – Also known as loose gravel.
  • Plastic Grids – These grids create porous systems, can be planted with grass, and also reinforce gravel driveways, fire lanes, and parking lots.
  • Permeable Interlocking Concrete Pavers – These pavers are laid out in a grid pattern, with the spaces in between filled with grass or small stones.
  • Permeable Clay Brick Pavers – Like interlocking concrete pavers but made from fired clay.
  • Resin-Bound Paving – This is a mixture of clear resin and aggregate, used in areas for both vehicles and pedestrians.
  • Bound Recycled-Glass Porous Pavement – A mixture of recycled glass, resins, and binding agents that creates colourful pavement for pedestrians and vehicles and keeps glass out of landfills.

How Is It Used?

Pervious concrete is typically used areas with light traffic, parking areas, pedestrian walkways, and greenhouses.

Porous concrete is delivered to the job site in ready-mix concrete trucks and placed within standard forms. Once placed, concrete contractors will use a vibrating mechanical screed to level the concrete. Then they will compact the concrete for greater strength using a heavy steel roller.

They will then mist the concrete with water, cover it with a plastic sheet, and keep it damp for at least seven days.

Why Is It Used?

Permeable concrete is used to retain stormwater, replenish water tables and aquifers, and reduce floods. It can take in rainwater at a rate of 3 to 5 gallons per minute per square foot. The rainwater may be stored in a gravel layer under the pavement, or it will percolate into the soil underneath.

This filtration process purifies rainwater by breaking down pollutants and chemicals with aerobic bacteria in the voids. These pollutants include heavy metals, hydrocarbons, dirt, and debris.

The filtration process also prevents rainwater from pooling up and causing erosion and pollution in nearby ecosystems.

Homeowners also use permeable concrete for their driveways to avoid puddling, prevent erosion, and save on costs for connecting to local storm sewer systems.

What Is It Ideal For?

Permeable concrete is ideal for low-traffic volume pavements such as:

  • Residential roads
  • Driveways
  • Sidewalks
  • Bike paths
  • Parking lots
  • Golf cart paths
  • Patios
  • Swimming pool decks
  • Sports pitches,
  • Low-water bridges
  • Sub-bases
  • Walls
  • Well linings

What are the Benefits of Pervious Concrete?

Environmental Benefits

When rainwater falls on impervious pavement on streets, sidewalks, driveways, and parking lots, this water doesn’t soak into the soil as it should naturally. Instead, it creates an imbalance in the environment, leading to the following environmental problems:

  • Flash floods
  • Erosion
  • Water table depletion
  • Pollution in water systems

Pollution in water such as ponds, streams, lakes, rivers, and coastal waters occurs due to storm and rainwater runoff. The rainwater washes oil, grease, de-icing salts, chemical fertilizers, and other contaminants from non-permeable pavements into the nearby water systems. As a result, fragile ecosystems are threatened by this pollution, and even humans are harmed by waterborne illnesses in the contaminated runoff water.

Permeable or porous concretes, on the other hand, allow rainwater to filter into the soil below, thus preventing the environmental problems associated with impervious pavement, and reducing the need for storm-water management systems.

Pervious concrete also allows trees to flourish in highly-developed urban areas by providing water and air to their root systems.

Another environmental benefit of porous concrete is its ability to help reduce the urban heat island effect. These pavements don’t absorb, store, and release heat back into the environment because they are porous and light in colour. The open-cell structure also allows cool temperatures from the earth below to cool the pavement.

The light colour of permeable concrete also makes it more reflective, which helps increase visibility at night, reducing the need for lighting and saving on energy.

Economic Benefits

Permeable concrete pavement is also an economically-viable pavement option. It reduces the long-term maintenance costs for storm-water management, such as costs for installing retention basins, curbs, and gutters.

It is just as durable as traditional concrete pavement, with the same low life-cycle costs. And it often has reduced installation time and costs since there’s no need for underground piping, storm drains, sloping, or grading.

Compared to regular pavements, porous concrete requires much less salt and other de-icing chemicals in winter, reducing costs for winter road maintenance and the harmful amount of salt and chemicals added to the environment.

Ease of Installation

Concrete contractors can often complete permeable concrete projects faster than regular concrete jobs. Unlike regular concrete, pervious concrete isn’t finished with a bull float or trowel since these seal pavement and prevent water penetration.

Lastly, permeable concrete is also better for drivers and pedestrians. Since it doesn’t allow rainwater water to accumulate and puddle on roads, this concrete reduces the risk of spraying pedestrians and hydroplaning while driving.

Now that you know what permeable concrete is, how you can use it, and its many benefits, consider using it for a more eco-friendly concrete construction project. Contact your local concrete suppliers for more information about this useful concrete pavement alternative.