Concrete could soon heal its own cracks, using bacterial spores:
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.
So the spores remain dormant until rainwater works its way into the cracks and activates them. The harmless bacteria — belonging to the Bacillus genus — then feed on the nutrients to produce limestone.
The bacterial food incorporated into the healing agent is calcium lactate — a component of milk. The microbes used in the granules are able to tolerate the highly alkaline environment of the concrete.
Self-healing and how about translucent?
Pretty cool time to be alive.
Relative to each other limestone is porous and concrete is not, and where the two meet you get problems. As the owner of a house made of limestone that has been patched with concrete I know a little about this.
Still, given that the limestone is filling a crack it will reduce the amount of water penetration but it would be more a patch than a heal. Maybe the limestone plug would spit out again at the next frost. Maybe it would be so small as to be a non-issue.