Self repairing concrete?

BBC:

Experimental concrete that patches up cracks by itself is to undergo outdoor testing.

The concrete contains limestone-producing bacteria, which are activated by corrosive rainwater working its way into the structure.

The new material could potentially increase the service life of the concrete - with considerable cost savings as a result.

The work is taking place at Delft Technical University, the Netherlands.

It is the brainchild of microbiologist Henk Jonkers and concrete technologist Eric Schlangen.

If all goes well, Dr Jonkers says they could start the process of commercialising the system in 2-3 years.

Concrete is the world's most widely used building material. But it is prone to cracks, which means that structures need to be substantially reinforced with steel.

"Micro-cracks" are an expected part of the hardening process and do not directly cause strength loss. Fractures with a width of about 0.2mm are allowed under norms used by the concrete industry.

But over time, water - along with aggressive chemicals in it - gets into these cracks and corrodes the concrete.

"For durability reasons - in order to improve the service life of the construction - it is important to get these micro-cracks healed," Dr Jonkers told BBC News.

Bacterial spores and the nutrients they will need to feed on are added as granules into the concrete mix. But water is the missing ingredient required for the microbes to grow.

... 

Rainwater will do the trick on exposed surfaces.  Concrete was the dominant material used by the Romans for their structures.  It is why their buildings outlasted those of other civilizations before them.  This process has teh potential to save repair costs on highways and foundations for homes built on a slab.