마술 같은 물먹는 콘크리트 This 'thirsty' concrete absorbs 880 gallons of water a minute — here's how it works: VIDEOS

  영국의 타막(Tarmac)사가 개발한 특수 콘크리트로 Topmix Permeable란 이름의 투수성 포장재이다. 

1분에 약3천3백리터의 물을 흡수할 수 있으며 흡수된 물은 콘크리트 밑으로 배수된다. 

타막사는 폭풍을 동반한 강우 시 빗물을 우회시키기 위해 개발했다.

하지만 배수 시 공극에 타 물질로 인한 막힘으로 유지관리에 큰 어려움이 있었다.

타막사는 이런 문제를 내부의 기술(비공개)을 사용해 콘크리트 페이스트 조절로 해결했다.

This 'thirsty' concrete absorbs 880 gallons of water a minute — here's how it works

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 vanishes almost instantly.

Traditional concrete has to be permeable enough to let a minimum of 300 millimeters of water an hour through to the ground level. That allows it to safely handle a 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 Permeable to divert rainwater during 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 permeable pavements 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. 

Tarmac

Here's how it works.

Rather than use sand-based concrete, Tarmac uses something called no-fines concrete. It's made up of tiny pieces of crushed granite packed 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 goes through 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 when the layer beneath Topmix can't pass the water through on its own.

Full attenuation uses 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 can choose between the three systems depending on their needs, Tarmac says.

Topmix Permeable fares well in all climates 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.

Topmix is 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 that existing 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.

http://www.businessinsider.com/how-magical-concrete-absorbs-water-2015-9

 

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