There's an old saying about one of the most common construction materials of the last 2,000 years: "There are two types of concrete: the kind that has cracked and the kind that will crack."

Scientist Henk Jonkers of Delft University of Technology in the Netherlands aspires to add a third category: the kind that has cracked and is repairing itself.

The revolutionary product formulated by Jonkers has been dubbed, "Living Concrete, " but Jonkers refers to it as "Bioconcrete"-"Concrete that heals itself using bacteria."

The product is mixed just like regular concrete, yet it contains miniscule biodegradable capsules filled with calcium lactate and bacillus bacteria.

When the concrete cracks and allows water to enter, the bacteria are roused from their dormant state and thus begin to feed on the lactate. Says Jonkers, "in doing so they combine the calcium with carbonate ions to form calcite, or limestone, which closes up the cracks."

Given that concrete forms much of the modern world's infrastructure-and that its upkeep is extremely costly and often quite difficult-Bioconcrete has vast cost-savings and sustainable potential. One especially auspicious area is the containment of hazardous waste. With self-repairing concrete, no one would need to risk contamination in order to effect repairs.

For project information, see the TU Delft Self-healing Materials research program.