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Bendable Concrete
Jeremy Faludi, 20 Jul 05

050509_concrete.jpg

Apparently a lot is happening in concrete these days, as yesterday's post showed. Another breakthrough came recently from the University of Michigan. As the university's Record reported last month, they have invented a bendable concrete.

Flexible concrete might sound like a gimmick, but most concrete fails because it is brittle, so cracks develop over time, and eventually become catastrophic. U Michigan has reduced this brittleness to make a concrete "500 times more resistant to cracking and 40 percent lighter." They also say that for a typical application, it "is 37 percent less expensive, consumes 40 percent less energy, and produces 39 percent less carbon dioxide".

Pretty amazing. So what's it made from?

The material is called ECC ("Engineered Cement Composites", which actually describes a whole family of materials that the university has been researching for a decade). Instead of being a composite of cement and aggregate (like gravel or other filler), it is a composite of fiber and concrete, like many of the high-performance concretes today. It does not use exotic fibers like carbon nanotubes, but instead relies on the cement (the glue holding fibers together, or the "matrix" of the composite") being more flexible than usual.

ECC is already heading out of the lab into real-world tests, first as a road patch in 2002 and this summer will be tried in part of a bridge deck. It'll still be some time before it hits the building industry, however.

Other data sheets and fun pictures (including spray-on ECC and ECC being used for the yearly concrete canoe competition, can be found here and here.

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Comments

Great find, Jeremy. Do you have a sense of the degree to which this process could be combined with some of the other advanced concretes we've posted about?


Posted by: Jamais Cascio on 20 Jul 05

On the topic of concrete alternatives, you may wish to look into "Isochanvre" - a hemp blended concrete alternative. I couldn't find out a whole lot on it; Given the product's apparently French origins, Nicole-Anne Boyer might have better luck (assuming she speaks French)!

http://sustainabilityzone.com/comments.php?load_this=124

Litracon was another interesting one, although it seems more cosmetic in nature, like using glass blocks for wall accents.


Posted by:
Rod Edwards on 20 Jul 05

How would you break this stuff down, if you wanted to demolish an existing structure to make way for a new one?


Posted by: sanman on 21 Jul 05

you may be able to cut it.. rather than break it..

probably, bendable concrete or sprayable ECC could be made cuttable than breakable..

just my inference based on nature of similar substances.


Posted by: harish on 21 Jul 05

One of the issues with the new technologies in concrete is its adoption by the industry. Because of the large number of regulations in biulding codes, especially local ones, it can take a long time for these innovations to be available. I certainly don't think the creativity and new technology is lacking, it may be the regulatory hurdles that delay introduction.


Posted by: Richard on 21 Jul 05

Hey, folks, a little roundup of responses:

Jamais:
ECC could indeed be combined with other concretes we've talked about. Personally, I think the best possible solution is concrete that is both fiber-reinforced and foamed (like Europe's autoclave stuff, or the Australian one you posted about.) Foaming concrete also helps stop crack propagation, and it lets you have thick slabs without much mass. (doubling the thickness of a wall or beam helps avert failure much more than doubling the material strength.) Their bendy-cement might also be amenable to using high-strength fibers like carbon (carbon-concrete mixes also change conductivity under stress, which can be used as a cheap distributed sensor system to detect strain.) And nano-sizing the fibers (no matter what they are) increases bonding between them and the matrix because of better surface-area-to-volume ratios. Etc., etc.

Rod:
I'm not familiar with that particular hemp-concrete mix, but there are many people using natural fibers (also jute, straw, and others) to be more eco-friendly fiber reinforcement. Unfortunately, though, none of these natural fibers are anywhere near as strong as glass or carbon fiber (though their bonding to the cement is usually better), so they don't help the strength of material that much, and end up kind of being a different kind of filler. But I see they've also combined this with lime-based cement, which is new. So even if it's the same strength as concrete but much lighter and greener, then great.

Harish:
I've no idea about cutting vs. breaking. But presumably for economic reasons you'd only build structures that have the same ultimate strength as what we build with normal concrete (actually less, in fact, if you know it'll be less likely to fail from crack propagation.) So it should be just as easy to break with a wrecking ball. It's just less likely to slowly crack and fall apart by itself over time.

Richard:
Yes, it'll no doubt take time to get to market. But maybe Kyoto and carbon markets will start to make normal cement more expensive, and alternatives will become more attractive. ...That's the main problem, is that right now concrete's so damn cheap.


Posted by: Jer on 21 Jul 05

There may be less need for the wrecking ball in the future. I have heard of company down that claims that their pre-engineered concrete building system "will never see a landfill". It seems that the concrete components can be disassembled to expand, contract or remove a building.


Posted by: Steve on 22 Jul 05

ooh, actually, that's brilliant. Yeah, one of the many good things about modular building systems is potential ease of disassembly.

We need to get the Lego corporation onto this...


Posted by: Jer on 22 Jul 05

Hello, Jeremy we spoke a year or so ago about ceramic cement and the R&D I have been doing in conjunction with Dr. Arun Wagh at Argonne National Labs and the Bindan Corportation. For those unfamiliar with phosphate-bonded cements check out www.bindancorp.com. Interesting article and comments. Two things caught my eye. I was unaware that portland cement naturally bonds with fiber, or any cellulous (as one comment infers), unless the fiber has been specially treated. Also over the past year I understand that portland cement is becoming increasingly difficult to obtain in large volumes and therefore it has significantly begun to rise in price, primarily due to the enormous volumes being consummed in China. Although ceramic cement is currently more expensive than portland cement to produce I have recently found methods to produce the raw materials much cheaper. I believe this will soon bring these superior cements in line with portland cement pricing. Ceramic cement also naturally and easily bonds with a wide variety of fiberous materials to create exceedingly strong composite materials. Judd


Posted by: Judd Hamilton on 24 Jul 05

for information.


Posted by: praful on 30 Jul 05



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