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Biologists Create Self-Healing Concrete
Mr.Intel writes: A team of microbiologists from the Delft University of Technology claims to have invented "bioconcrete" — concrete that heals cracks and breaks using bacteria. The goal was to find a type of bacteria that could live inside concrete and also produce small amount of limestone that could re-seal cracks. This is a difficult prospect because concrete is quite dry and strongly alkaline. The bacteria needed to be able to stay alive for years in those conditions before being activated by water. The bacteria also need a food source — simply adding sugar to concrete will make it weak. The scientists used calcium lactate instead, adding biodegradable capsules of it to the concrete mix. "When cracks eventually begin to form in the concrete, water enters and open the capsules. The bacteria then germinate, multiply and feed on the lactate, and in doing so they combine the calcium with carbonate ions to form calcite, or limestone, which closes up the cracks."
Bacterial concrete is ideal for constructing underground retainers for hazardous waste, as no humans would have to go near it to repair any occurring cracks. For residential buildings, however, it does seem the traditional repairing of cracks will remain the most economically attractive solution for now.
Currently, our research focuses on creating the right conditions for the bacteria to produce as much calcite as possible and on optimizing the distribution of food for the bacteria.
"First they came for the slanderers and i said nothing."
Concrete longevity has a LOT to do with preparation and maintenance.
For example tree roots - proper subsurface preparation, which isn't normally done for sidewalks, will result in roots not extending far under the concrete, and even if they do penetrate somewhat, not growing large enough to crack the concrete. Failing that, routine maintenance with certain products will kill the roots before they get too large, but leave the rest of the tree unaffected.
As for your questions -
1. It will probably only fix any given crack spot once.
2. 99% of the fixes will be practically microscopic in nature.
3. At the depths we're looking at, restoring a barrier is a bigger deal than being structural.
4. Most of the time the very cracking releases the stress that caused the crack, then water gets in and freezes, widening it. This keeps the water out(after the bacteria do their job).
I don't read AC A human right
Bacteria are no more animals than a rock or baseball bat. They're Prokaryotes, which is an entire different kingdom than Eukaryotes which include plants and animals.
You need to read some biology text that's younger than 30 or 40 years old.
Life hasn't been divided into just plants and animals in a long time. There's also fungi, bacteria, archaea, ... See here for example.