http://www.dailymail.co.uk/sciencetech/article-3083588/No-potholes-Living-concrete-heals-using-BACTERIA-comes-contact-water.html
No more potholes! 'Living' concrete heals itself using BACTERIA when it comes into contact with water
Bacteria are typically found near volcanoes and is heat and cold resistant
The bacteria and calcium lactate is mixed with water and concrete
When cracks appear, and rain enters them, the water 'awakens' the bacteria
Bacteria then 'eat' calcium lactate and secrete limestone to close cracks
And this bacteria can also be added to a liquid and sprayed onto existing cracks formed by decades of wear and tear, as well as onto other materials.