Super reefs of concrete

In Denmark, scientists and artists are currently working on an artificial reef made of newly developed concrete. The 'Super Rev' (Super Reefs) project aims to restore 55 square kilometres of reefs off the Danish coast. The driving force behind the project is an international group of artists - Superflex - who, together with the Technical University of Denmark

(DTU), are investigating whether it is possible to turn newly developed concrete into a stone reef. This is necessary because 8.3 million cubic meters of rock have been removed in the past 100 years to expand Danish ports and to produce concrete. According to a study by DTU Aqua, this is equivalent to removing 55 square kilometres of habitat for animals and plants. The advantage of using concrete is that it is easy to form and is not only responsible for CO2 emissions during the manufacturing process, but also absorbs CO2 during its lifetime. This creates a chalky surface layer, resemblaning to the surface of coral reefs and therefore forms a natural breeding ground for marine animals.

The researchers at DTU have now tested three different concrete variants. A pigment was added to one concrete that turns the artificial reef pink, which Superflex says is the favourite colour of several organisms. Another concrete consists of cement with added recycled raw materials from the brick industry, resulting in a brown material. In the third concrete, the researchers partially replaced cement with high-fired Danish clay, which in this case creates an orange colour. The project partners are also investigating whether concrete from other projects can be reused.

DTU is also involved in a similar project (Living Port) in Puerto de Vigo, Portugal, collaborating with ECOncrete, a construction company that develops new concrete and concrete elements. The pilot project was funded by the EU's Horizon 2020 and recently won the 'Infrastructures' category at the World Sustainability Awards. Another project is being carried out in Køge, where DTU is helping to create a rich fish life on the seabed of Køge Bay, also by applicating concrete reefs.

The intention is that the projects will not only benefit marine life and increase biodiversity, but also that the construction industry can use the experience for future coastal protection projects, bridges, tunnels and offshore wind farms.

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