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New 'Thirsty' road surface absorbs up to 1,000 litres per minute

9 Oct 15  | BMS & Building Services
LaFarge's Topmix Permeable may hold the answer to flooded roads

We all know that the UK is a place of incredible amounts of rain. Every now and then, however, the sheer level of rain catches us by surprise and our riverbanks burst, our roads flood and we grind to a standstill. Or jump in a kayak. The winter of 2014 saw widespread floods, causing damage in excess of £1bn, while the winter of 2012’s floods caused almost £4bn worth of damage. In 2007, floods caused around £3bn of damage, with more than two-thirds of homes affected flooded by water running off of paving or overflowing from overloaded drainage systems.

LaFarge Tarmac, the UK’s leading sustainable building materials and solutions company, have developed a new product which may provide the answer to problems facing the majority of Sustainable Urban Drainage Systems (SuDS) designs. Topmix Permeable is ‘a fast draining concrete pavement solution which rapidly directs stormwater off streets, parking surfaces, driveways and walkways, [which] minimises the cost and long-term maintenance for local authorities and developers of stormwater management’.

Existing surface water drainage systems suffer from a number of problems. For example, the continued expansion of urban areas using impermeable materials reduces the square footage of land which can absorb water away from the surface, meaning water is pooling on the surface in far greater quantities. The majority of our existing drainage systems are designed to direct excess rain water into watercourses or drains, but where heavy rainfall is prolonged, these courses quickly become saturated and begin to overflow. Water running down the road can quickly become contaminated by fuels, detergents and other pollutants, which can lead to increased pressure on water treatment plants or contaminated water being drained straight into watercourses.

Traditional drainage systems can be expensive to maintain, and the direction of rainwater directly into watercourses or drains and sewers can result in natural aquifers being bypassed, thereby reducing the level of the water table, which can lead to water shortages, natural streams and ponds drying out and even damage to the foundations of homes, as clay-laden soils dry out and shrink.

Topmix Permeable functions as a super-absorbent surface covering for myriad ground surfaces, ‘drinking in’ incredible amounts of water almost instantaneously. A permeable layer of concrete sits on top of the road, allowing water to drain down through a matrix of relatively large pebbles into a loose base of aggregate underneath. Extra drainage channels are incorporated into this aggregate layer to help increase the amount of water it can manage.

Topmix Permeable is capable of absorbing up to 4,000 litres of water in the first 60 seconds, and has a drainage capacity of 150-1,000 litres per minute per square metre.

One obvious issue which could face this system is the possibility of water held within the material freezing in low temperatures. LaFarge Tarmac claim that very little water would be retained by the material, but that, should climate change cause water retention within the system, the high void content (up to 35%) would allow the water to freeze and expand without damaging the surface itself.

Another possible problem could be the build-up of dust, dirt and other materials which might block the permeable layer. LaFarge Tarmac is designed to remove a high percentage of Total Suspended Solids (TSS), reducing this risk, though regular hydro-pressure cleaning is recommended for optimum results.

Kayhan Ozturk, CBSbutler’s BMS team leader, is very excited about the possible uses of this material, and believes that ‘aside from the obvious infrastructure and road applications, this, or future variants of this technology could provide a good solution for replacing flooring in ground or basement level plant rooms to prevent flooding and critical failures of HVAC, BMS Controls and other electrical systems within buildings, without the need for additional drainage systems and pumps.’


Looking for work within the BMS and Built Environment sectors? Give Kayhan a call on 01737821034 or send your CV to


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