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Self Healing Concrete?
Recently fellow member @TBA sent me a link reminding me about some new ideas in concrete technology I first heard about a year or so ago. Cracking, as you may suppose, is one of the biggest threats to the integrity of concrete structures. Water crystals freezing and thawing in a confined space of a crack can cause significant damage. Water can also deteriorate steel reinforcement, weakening critical parts of bridges, dams, etc…. Water and other chemicals and gasses can also make their way into a structure through micro-cracking, which is inherently present in concrete. The goal of “self healing” concrete is to figure out an additive to the mix that will repair cracks as they occur. Researchers have discovered a few kinds of ureolytic bacteria that can be mixed in the concrete when it is produced and lies dormant in the hardened concrete. If it is ever exposed to water through a crack however it will activate and produce limestone to fill the crack automatically. Here is a short video explaining the basics:
This is still in the research phase but there seems to have been significant progress made in the year or so since I first heard about it and could have tremendous impact on infrastructure projects like bridges, walls, damn and really any exterior concrete exposed to the elements.
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Water sure weakens my damns; but alcohol makes them stronger.
You are self healing and self medicating!
I don’t get sick very often (no self-respecting bacterium would live in me), but this knee is driving me crazy.
What a time to be alive!
I expect that in a Planet of the Apes scenario, eventually all the concrete would be replaced by limestone, sort of like petrified wood.
How about a coating?
The PWRs (pressurized water reactors) I’m familiar with have pressure vessels typically made of carbon steel for strength, but they also have a metal liner inside to resist corrosion. It works really well—so well, commercial reactors get license extensions beyond their normal design life.
Can a liner be made for concrete in addition what you posted about? Maybe a two-pronged approach would allow concrete structures to last for centuries instead of decades, or years . . .
There are lots of coatings used, some to more success than others. Epoxy coatings are also typically used on steel reinforcement used in bridges and other critical structural elements exposed to the weather. There is also a coating company called Spray-Lock who’s product is supposed to fill in cracks form the surface and water proof the concrete.
We’re always theorizing around here. Always good to see someone taking concrete measures.
Someone had to say it.
No. They didn’t.
I doubt that this will make a big difference in infrastructure projects any time soon, but it is interesting and smarter people than I have been wrong about the impacts of new inventions. Cor-Ten steel was supposed to be a big deal, but in practice, not so great. Environmentalists might be concerned about releasing the Andromeda strain, perhaps rightly so.
You guys may want to congratulate Concretevol. He’s now on the board of directors of the Tennessee Concrete Association. I’m certainly not (going to congratulate him).
Is there a Tennessee Abstract Association?
No one can tell.
What you have to understand is that self-healing concrete isn’t going to fix stuff like in Concretevol’s picture. It’s going to prevent it from happening.
I doubt it. In many parts of the country, title insurance companies and such have been trying to have existing abstracts destroyed, much to the dismay of genealogists.
Which picture? Of his concrete or his picture?
Both.
It’s downright Star Trekish. In the best way.
Oh, please tell me the optimum source of this bacteria is the burned bones of Roman slaves, so the circle can be complete. :)
Apparently, the Romans figured out something like this. Seawater actually made their concrete stronger by provoking a chemical reaction resulting in a rare chemical that strengthens the concrete by making it more flexible. Scientists are studying what the Romans did in the quest for self-healing concrete. https://www.nature.com/news/seawater-is-the-secret-to-long-lasting-roman-concrete-1.22231
Yes it’s a similar concept in that you are using naturally occurring things (volcanic ash/bacteria) in the mix to make the concrete more durable. I believe the Romans lucked into the side benefit of a seawater reaction that formed Tobermorite, but that doesn’t make it any less valuable. I hadn’t read before that the crystals made the concrete more flexible but it definitely made it harder, whereas modern concrete using portland cement is very susceptible to breaking down from sea water.
Sorry, my friend. Given what we know about the immune role of your microbiome, if you don’t get sick often, part of the credit has to go to the bacteria living in and on you. Can’t speak to whether they respect themselves, though.
Does the bacteria remain in the concrete or spread beyond? What are its temperature tolerances? How expensive is its procurement and preservation before mixing?
It sounds useful. But, as I’m sure you know, there are no perfect solutions. Each new element introduces its own challenges.
@concretevol, I was intrigued a few years back by mention development of a translucent concrete. Did anything practical ever come of that?
Speaking of coatings and corrosion, this has gotten to me since I first learned of it back in science school:
If you
are weird like me andfind this sort of thing fascinating (and especially if you’ve had a few more sporting moments in the chemistry lab or factory than you wanted to going in) you might enjoy the recurring posts on Derek Lowe’s excellent In the Pipeline drug development blog that appear under the rubrics Things I won’t work with and Things I’m Glad I Don’t Do.Here’s a sample:
Reassurance to parents: They don’t let beginners play with this stuff in Chem 1A.
Amazing!
The first thing I thought of was Gaudi’s buildings in Barcelona; to me, they look like they’re made of organic concrete!
As far as I know the bacteria remains dormant within the concrete until the introduction of water. I haven’t read of any temperature issues while it is in the dormant state and obviously it would have to be above freezing for water to seep into a crack. I don’t know what the costs are to this method as it is still in the testing and experimental stages.
Yes I would bet this is not a “cure all” but it is an exciting development when it comes to combating water/chemical damage.
@ontheleftcoast, I don’t have any first hand experience working with translucent concrete. I’ve heard about it for awhile and from what I understand it is still primarily used as in interior decorative pieces. I believe it is done either by replacing aggregates with glass or other light emitting materials or actually using some time of fiber optics. It definitely sounds expensive and rather exotic.
The species mentioned are spore formers, whose spores evidently can survive the alkaline conditions of uncured concrete and the heat of curing – which wouldn’t be that exotic. Many bacterial spores tolerate pretty hostile conditions and can persist for years waiting for the right conditions to come along. The other ingredient, calcium lactate, is fairly soluble. I wonder if it leaches out over time.