Topmix Permeable is a concrete solution created by Tarmac, a United Kingdom building materials and solutions company, that can absorb water. It was created in an attempt to divert rainwater during major storms.
Concrete traditionally only has to be permeable enough to let a minimum of 300 millimeters of water an hour through to the ground level, this allows it to handle a major storm every 100 years or so. Topmix Permeable concrete allows 36,000 millimeters of water an hour through to the ground, that’s approximately 880 gallons of water absorbed every minute.
“We believe that the capacity is several times more than enough to deal with the heaviest rainfall we’ve ever experienced in the UK,” says Richard Stares, the commercial director at Tarmac. “The product’s price is similar to other concretes on the market,” he added.
One of the only issues with this incredible concrete solution is that it requires heavy maintenance because of blockage caused by water mixing with dirt underneath the concrete. This can cause it to harden inside the gaps and could reduce the permeability.
Burgess claims that Tarmac avoided any problems with this by using “paste control,” which is an in house technique that’s used to mix the concrete that keeps it porous over long periods of time.
How does Topmix Permeable Concrete work?
Topmix permeable concrete uses something called no-fines concrete as opposed to the traditional sand based concrete. This special kind of concrete is made up of tiny crushed pieces of granite that are packed together, but loosely enough to allow water to pass through. This amazing system accommodates three designs:
- Full infiltration – Which refers to a system where the water flows through the Topmix and into the soil underneath. This is primarily used in wet areas that typically don’t need to collect much rainwater.
- Partial infiltration – This system is the semi-permeable solution. It has a barrier beneath the Topmix that acts as a drainage system into nearby sewer systems or waterways.
- Full attenuation – This refers to a system that captures all the water that flows through the Topmix and stores it in a designated location. This is used in areas that have unclean water and high recycling rates.