Communicating biodiversity in coastal infrastructure using coloured concrete

Lack of hard substrate in the ocean has a negative impact on the marine ecosystems, as habitats, hiding places and feeding grounds have disappeared in past decades. By integrating solutions specifically designed for improving biodiversity, social acceptance and aesthetics, while maintaining structural durability more sustainable solutions for coastal infrastructure can be realized. Concrete provides flexibility for creating diverse surface textures, overall shape and chemical composition of each unit, when compared with other materials, providing advantages when utilized as hard substrate for the creation of marine habitats. With this focus, specifically designed concrete units were installed in Copenhagen harbour in collaboration with the art collective SUPERFLEX. Three mineral admixtures were chosen for this art installation to highlight the reduction of environmental impacts as well as achieving specific colours. Namely, iron oxide, biosilica and chamotte were used with a substitution rate of white Portland cement at 1%, 10% and 15% respectively. XRD, TGA, Titration, indicators and were used to characterize changes in mineralogy. After 4 and 19 months of exposure, similar performances for the three mix-designs were observed. However, the mixture containing biosilica showed tendencies towards an increase in early resistance towards chloride ingress.