Porous Concrete

Porous concrete helps to reduce the risk of flooding in urban areas, draining and filtering rain away from the surface, with benefits to human health and safety.

Sustainable urban drainage systems (SUDS) are an increasingly important component of climate adaptation in urban areas, as more frequent and more severe rainfall events occur because of climate change.  These in turn increase the risk of surface flooding (flash floods). This risk is further elevated by the lack of ground surface available to absorb water (e.g. due to the presence of buildings or impermeable roads), thus increasing water runoff.

Porous concrete offers a solution to this challenge, allowing designers to incorporate SUDS into developments without reliance on soft landscaping (a common SUDS solution). Produced with little to no fine aggregate content, it will typically comprise 15%-25% voids. These voids allow water to flow through the concrete at rates of around 0.34 cm/s (480 in./hr), which is 200 L/m²/min (5 gal/ft²/ min).

The use of porous concrete reduces the risk of flash flooding, minimises stormwater runoff to surrounding waterways, and allows natural filtration to recharge local groundwater suppliers. It also helps to treat pollutants from vehicles and other sources (in the form of hydrocarbons and heavy metals, as well as sediment accumulate on the surface), allowing clean water to pass through the pavement into the native soil beneath.

In addition, in certain regions, dry and clean surfaces minimise the risk of mosquito breeding, while the open pore structure and light colour of porous concrete means it absorbs less heat from solar radiation than darker pavements, helping to lower heat island effects in urban areas.

In the context of phrases such as “concrete Jungle” and “concreting over the country”, the fact that there are concrete solutions to the climate change risk of increased surface flooding is clearly positive for concrete and demonstrates concrete’s sustainable value.

Header photo by Paul Mocan on Unsplash