For self-healing concrete, just add bacteria and food

Like living bone, concrete could soon be healing its own hairline fractures – with bacteria in the role of osteoblast cells. Worked into the concrete from the beginning, these water-activated bacteria would munch food provided in the mix to patch up cracks and small holes.

Concrete reinforced with steel forms the skeleton of many buildings and bridges. But any cracks in its gritty exterior make it vulnerable: "Water is the culprit for concrete because it enters the cracks and it brings aggressive chemicals with it," says Henk Jonkers of Delft University of Technology in Delft, the Netherlands. These chemicals degrade both concrete and steel.

Locating and patching cracks in old concrete is a time-consuming business, but rebuilding concrete structures is expensive. Jonkers thinks the solution is to fight nature with nature: he suggests combating water degradation by packing the concrete with bacteria that use water and calcium lactate "food" to make calcite, a natural cement.