Concrete is the most commonly used building material in the world, and can be found in almost any structure: from buildings to bridges to waterfronts. It is made from a mix of cement, coarse and fine aggregates like gravel and sand, and water. However, it has considerable environmental impacts through all its life-cycle. Its manufacture requires extraction of raw materials, energy, and the production of cement releases CO2 as limestone is broken up. In fact, 5% of global CO2 emissions can be attributed to cement manufacturing. When used in coastal structures, cement blocks are not friendly to habitation by marine life because of their structure and chemical composition.
For several years now efforts are concentrated to find ways to minimize the environmental impacts of cement production. A spin-off of Imperial College in the UK, Novacem, announced in 2010 a greener way of cement manufacture, based on magnesium oxide. Not only did the procedure not require limestone, but it required much less energy and the new version of cement could absorb 0.6 tonnes of CO2 per tonne of cement. However, the company did not gather enough funds, the rights to the technology were sold and no follow-up has been announced so far. Other companies are currently working on CO2 sequestration in cement- like CarbonCure, who injects captured CO2 in conventional Portland cement or Solidia Technologies, who ingest CO2 to cement to produce concrete that could be 10-25% stronger than conventional. Other approaches suggest concrete mixtures which require less cement, for example by applying nanoengineering or by adding fly ash.
Regarding concrete coastal structures, ECOncrete have developed concrete products with bio-enhancing additives and with a structure that allows the development of marine ecosystems on the building blocks. The elements can be used in sea walls, marinas, tide pools and armouring units that protect and support marine habitats, while at the same time increasing the resilience of material. The providers claim that their concrete blocks offer 30-46% reduction in greenhouse gas emissions, compared to Portland based mix, act as long-term Carbon sinks and integrate byproducts and recycled materials.
There’s a lot more room for development of greener building materials. New approaches can improve energy efficiency, composition and use of recycled components in the production, which are very much needed considering the current rates of increase in building activity.