Biomason Builds Concrete With Bacteria
2nd March 2021
A billion or two years ago, corals, brachiopods, and other sea creatures took carbon dioxide and calcium out of the seawater to build shells out of calcium carbonate, CaCO3. They were little biological factories capable of building giant structures like coral reefs. When they died they would sink to the bottom of the shallow seas and become limestone.
About 200 years ago, Joseph Aspdin figured out how to reverse the process, cooking limestone and clay at high temperatures, which decomposes after the water and carbon dioxide is driven off, leaving calcium oxide (CaO). This reacts with other ingredients, silicates and aluminates, to make Portland cement. Mix that with aggregate and water, and the mixture crystallizes and glues everything together into concrete.