Concrete is prone to developing cracks as it ages. That in and of itself is not a real problem; minor cracks do not a structural problem make. The problem come when water gets into those cracks. Water erodes the concrete structure from the inside out, carries with it other caustic chemicals (e.g. acid rain) and when it freezes inside the concrete does more dammage as it expands.
At the Delft Technical University in Holland Netherlands microbiologist Henk Jonkers and concrete technologist Eric Schlangen are working on a possible solution for cracked concrete by having the concrete repair itself. Concrete is mixed with bacterial spores and the nutrients for the spore. On their own the two ingredients are inert. But when water is introduced the spores start to feed and produce a very useful biproduct: limestone.
"In the lab we have been able to show healing of cracks with a width of 0.5mm - two to three times higher than the norms state," Dr Jonkers explained.
Read more about the project here.