When people first hear the words thirsty concrete, they wonder, “what is thirsty concrete?” because they have never heard of it. Once they know about it and how it can be used for pavement that can withstand excessive rain, they wonder, “how does thirsty concrete work?”
Here is everything you need to know about thirsty concrete:
1. Thirsty Concrete is a Nick Name
Lafarge Tarmac invented a porous concrete called Topmix Permeable that drains water at an amazing rate. Thirsty Concrete is just more memorable than Topmix Permeable.
2. How Thirsty Concrete Differs from Traditional Concrete
Traditional concrete only has to be permeable enough to let a minimum of 300 millimeters of water an hour through to the ground level.
It can only safely handle a major storm event every 100 years. Climate Change is changing that.
Thirsty concrete can let 36,000 millimeters of water through an hour, or about 880 gallons every minute!
3. The Issues with Permeable Pavements
One drawback with permeable pavements is that they require a lot of maintenance because of blockage.
When water flows through the concrete, it sometimes mixes with the dirt underneath and hardens inside the gaps, which reduces permeability.
Tarmac avoided this problem with “paste control”, an in-house technique used to mix the concrete which keeps it porous.
4. How Thirsty Concrete Works
Thirsty concrete doesn’t actually absorb water. When water hits it, it doesn’t flow all over the place and slick up the surface. It flows down only and is gone almost instantly, because it drains into the ground.
It drains because the concrete is made of small pieces of granite that are packed together, instead of the sand of traditional concrete.
There are three different designs of concrete, each made up of two layers. The designs are full infiltration, partial infiltration and full attenuation.
Full infiltration: with this design, all water goes through Topmix to flow into the soil underneath.
Partial infiltration: this design involves a semi-permeable barrier beneath Topmix that acts as a drainage system into nearby sewers or waterways.
Full attenuation: this design uses a capture system to store the water that flows through Topmix. This captured water can be reused later.
5. The Application of Thirsty Concrete
With global warming causing rainfall rates to increase, thirsty concrete could help preserve infrastructure and communities in times of excessive rain.
It is unlikely thirsty concrete will be able to hold up to the wear of city traffic because of a top layer of fine, tightly packed granite. Tests showed it performed best with driving conditions where the speed limit was 30 miles per hour or less, and the traffic situation was moderate to light.
Freezing climates are out of consideration for thirsty concrete as well. Water trapped inside it would solidify and expand, causing the permeable layer to bend or crack.
Thirsty concrete solves the flooding problem that happens when land is paved over and the water has nowhere to go because it can’t be absorbed.