As Landscape Architects, we are always trying to find ways to reduce a project’s carbon footprint, yet one of the most ubiquitous, materials we find ourselves having to specify is concrete; however, the production of concrete produces a lot of carbon dioxide. This is because the process of creating concrete’s key binding ingredient (Portland Cement) takes an enormous amount of energy. Portland Cement is made by adding clay and ground-up limestone together and heating it to 2000 degrees, which demands a lot of coal-powered energy. On top of the energy required to heat the mixture, the chemical process of heating limestone to get it to become quick-lime releases carbon dioxide. The cement is then mixed with aggregate and water to create concrete.
We recently were introduced to CarbiCrete – a new cement-free, carbon-negative concrete. This product is innovative in that it makes use of slag left over from steel production. This energy-rich waste product is ground to a powder, then mixed with aggregate and water which serves as a binding material in place of cement. The concrete mixture is then formed into blocks, the process of which actually requires carbon dioxide – the blocks absorb carbon dioxide as they form! Therefore, CarbiCrete production is not only carbon neutral, it is carbon negative.
Currently, CarbiCrete is only available in a pre-cast form, meaning that there are many instances where Poured-In-Place Concrete will still be required. However, products like these give us hope for a better future!
Read more about CarbiCrete. CarbiCrete is based in Montreal and has several pilot studies in the works.
image source: CarbiCrete – https://carbicrete.com/concrete-makers/
Thank you to the New Yorker’s article “A Vast Experiment – The Climate Crisis from A to Z”
https://www.newyorker.com/magazine/2022/11/28/climate-change-from-a-to-z