No matter how carefully it is mixed or reinforced, all concrete eventually cracks, and under some conditions, those cracks can lead to collapse. "The problem with cracks in concrete is leakage," explains professor Henk Jonkers, of Delft University of Technology, in the Netherlands. "If you have cracks, water comes through -- in your basements, in a parking garage. Secondly, if this water gets to the steel reinforcements -- in concrete we have all these steel rebars -- if they corrode, the structure collapses. "Overtime, this can become a dangerous (and expensive) problem." But Jonkers has come up with an entirely new way of giving concrete a longer life. "We have invented bioconcrete -- that's concrete that heals itself using bacteria," he says.
The bioconcrete is mixed just like regular concrete, but with an extra ingredient -- the "healing agent." It remains intact during mixing, only dissolving and becoming active if the concrete cracks and water gets in. When water gets into the cracks, the bacteria is activated and produces a component in limestone called calcite that fills up the crack completely. Researchers are still conducting outdoor tests to see if the concrete can be put to real use.
Jonkers chose bacillus bacteria for the job, because they thrive in alkaline conditions and produce spores that can survive for decades without food or oxygen. He hopes his concrete could be the start of a new age of biological buildings. "It is combining nature with construction materials," he says. "Nature is supplying us a lot of functionality for free -- in this case, limestone-producing bacteria."