Henk Jonkers, a microbiologist at the Delft University of Technology, in the Netherlands, has developed a way to make the cracks in concrete structures heal themselves. This is accomplished by embedding the concrete with limestone producing bacteria - the Bacilus Pseudofirmus or the Sporosacina Pasteurii.
When water enters the cracks in the concrete, the dormant bacteria become activated and start producing limestone which fills the cracks and eventually covers them. This prevents many problems commonly found in concrete structures as they age, such as leakage and the corrosion and oxidation of the steel reinforcements.
This innovation tackles the issue of the durability of concrete, which is the most common building material used worldwide. These bacteria can lie dormant in the artificial stone for up to 200 years, which is way beyond the common lifespan for modern buildings.
Sources: Futurism, Smithsonian