This no joke, concrete can heal itself. A Dutch Scientist that a very specialized lime producing bacteria, when put on concrete, can heal itself. In fact, this scientist is a finalist in the European Inventors Award 2015.
This specialized bacteria, which forms naturally in high-alkaline lakes can survive up to 200 years without any water or food. The bacteria can be activated when it comes into contact with water and it uses the calcium that is in the concrete for food. When the concrete cracks, it uses the water and food to form a repair patch in the concrete.
According to the scientist, it will take 3 times as much to do a concrete job. They activate the bacteria with water and spray it onto the concrete.
But, the more we think about it, the patch is limestone. We know concrete expands and contracts and lime expands and contracts at different intervals. So it is going to form a patch, but will it seal anything in the future, I don't think so.