Slashdot Mirror
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."
Okay, so the bacteria are going to be in the walls, exposed to mutagens and/or radiation, and unobserved by humans for years at a time. I want movie rights!
That basically describes how your walls are right now.
"First they came for the slanderers and i said nothing."
If I can't stop concrete sidewalks from being cracked by tree roots over the years, something is wrong with me? Obviously, I should just chop down all nearby trees.
If I can't stop idiots with trucks that surpass expected weight limits or heavy objects falling onto the concrete, something is wrong with me? I'm not Superman.
This has nothing to do with concrete when it being formed. The worst that happens at that time are paw prints and graffiti.
My concern is, if this stuff works, how much will it work? Will it repair itself in the same area more than once? What is to stop the bacteria from forming a big lump on the surface after they bridge the crack's gap. Is the replacement material even nearly as strong as the original concrete or will it just break again under less stress? If the intended use of this for building construction or surfaces to walk on? I can see it being used in 1-3 story buildings as material, but any where solid concrete has to be used instead of those hollow cinder blocks, I can't see it being possible, much less if water is needed to activate it.
If the concrete fills it's own cracks automagically, two questions spring to mind: 1) Will the crack-filling material have the same load bearing properties or (as I suspect) it will be much weaker at those spots, and 2) will the filled cracks disguise the facts that the object may be under a load that was not anticipated by the designer (tensile or bending loads vs. compressive loads)?
Reinforced concrete is often used in bending and tensile load applications in architecture, and if the reinforcing is not stiff enough cracks often will appear on the surface. They are unsightly, but if the reinforcing is taking the load (as it should) these are not structural deficiencies. But for complex architectural domes and shells, the presence and size of these cracks is something that needs to be monitored.
If the concrete is used in a container and it cracks, we may actually want to see the crack as that is a warning that something is being loaded in an unanticipated way. Hiding it with a self-filling mechanism may not be desirable.
Left MS Windows for Linux Mint and never looked back!
Vote for Bernie in 2016!