The researchers found just the right candidates: a hardy bunch of spore-forming bacteria belonging to the genus Bacillus that make a great living in the alkaline soda lakes of Russia and Egypt. Jonkers and his colleagues placed the spores and their food source, calcium lactate, into small ceramic pellets to prevent them from being activated prematurely by the wet concrete mix and adversely affecting the integrity of the material. The spores remained dormant until the formation of a crack allowed water to sneak in, waking the bacteria and their appetite. As they began to chow down, gobbling up the calcium lactate and water, they also began to pump out calcite (a very stable form of calcium carbonate), which quickly went to work filling up the holes. Now that they’ve successfully tested the bacteria’s mettle, Jonkers and his co-workers plan on comparing the strength of their natural concrete to that of the real thing.
Regular readers may remember that this is an idea we’ve seen before.