Concrete, one of our most useful and versatile building materials, is dangerous when damaged. When that happens, it's more usual to send for a concrete mixer rather than a doctor. All that's about to change with self-healing bio-concrete developed by microbiologist Henk Jonkers and concrete specialist Eric Schlangen. Indeed, special bacteria have been added in the mixture. When water enters the concrete, bacteria munch on calcium lactate: prognosis for recovery excellent!