When water hits Topmix Permeable concrete, it doesn't flow in all directions, slicking up the surface.It flows in one direction ' down. And it vanishesalmost instantly.Traditional concrete has tobe permeable enough to let a minimum of 300 millimeters of water an hour through to the ground level. That allows itto safely handlea major storm event every 100 years.Topmix Permeable, in contrast, lets through 36,000 millimeters of water an hour, or approximately 880 gallons every minute.The seemingly magical product comes from Tarmac, a UK building materials and solutions company, which created Topmix Permeabletodivert rainwaterduring storms.While the company itself is only a few months old, the technology has been in development for the last six years, says product development manager Craig Burgess.One of the main issues with permeablepavements is that they require heavy maintenance due to blockage, Burgess says.As water flows through the concrete, it can mix with the dirt underneath and harden inside the gaps, reducing the permeability.Burgess says Tarmac avoided this problem with "paste control," an in-house technique used to mix the concrete that keeps it porous over time.Here's how it works.Rather than use sand-based concrete, Tarmac uses something called no-fines concrete. It's made up oftiny pieces of crushed granitepacked together. While Burgess says the mixture is extremely dry, the pieces are packed loosely enough to allow water to pass through.The system can accommodate three designs: full infiltration, partial infiltration, and full attenuation.Full infiltration refers to a system where all water goesthrough Topmix to flow into the soil underneath. It's particularly useful in wet areas that don't need to collect the rainwater.Partial infiltration involves a semi-permeable barrier beneath Topmix that acts as a drainage system into nearby sewers or waterways ' useful whenthe layer beneath Topmix can't pass the water through on its own.Full attenuationuses a capture system to store all the water that flows through Topmix. This option is most useful in areas with unclean water and high recycling rates, since the captured water can be reused later.Cities canchoose between the three systems depending on their needs, Tarmac says. Topmix Permeable fares well in allclimates except extreme cold, according to the company. In tests, it performed best in driving conditions where the speed limit was 30 miles per hour or less, and traffic was moderate to light.Topmixis currently limited to sales in the UK. In its brief life span, it's been installed on a car park and a golf course.Though the one-time cost of replacing infrastructural systems may be high ' given thatexisting roads would need to be totally gutted ' over time the reduced maintenance costs could make Topmix a worthwhile investment in countries prone to flooding.Or those that simply want to be more like sponges.Join the conversation about this storyNOW WATCH: This new 'thirsty' concrete absorbs 880 gallons of water a minute
Click here to read full news..
