Researchers Make Bendable Concrete

karvind writes "PhysOrg is reporting that scientists from University of Michigan have developed a new type of fiber-reinforced bendable concrete. The new concrete looks like regular concrete, but is 500 times more resistant to cracking and 40 percent lighter in weight. Tiny fibers that comprise about 2 percent of the mixture's volume partly account for its performance. Also, the materials in the concrete itself are designed for maximum flexibility. Because of its long life, the Engineered Cement Composites (ECC) are expected to cost less in the long run, as well." Michigan roads must make the perfect test cases for this stuff, and I look forward to their improvement.

Origional News Source at U of M

[Kelerain]

Why not link to the source at the U of M News Service:

U-M researchers make bendable concrete [umich.edu]

Technocrat.net [technocrat.net] had this article [technocrat.net] earlier today, and without the extra advertising.

interesting stuff!

Re:Springs made out of concrete

[MacroRex]

There is also translucent concrete [slashdot.org] which works by having optical fibers mixed in.

Re:Remember asbestosis?

[Anonymous Coward]

No, the only reason asbestos is damaging to lungs is that it
tends to form particles 0.5 to 1.4 microns in diameter, which is the range in which any paticulate matter is lung damaging and carcinogenic in nature. Asbestos is not mutagenic; any particles that form mainly in that size will cause lung cancer. It is a strange twist of fate that asbestos fibers disintigrate to particles that size, but it has nothing to do with fibers in general or their chemistry.

Re:Remember asbestosis?

[Skadet]

Concrete is already a very harmful substance in mix form, or when it gets dust-i-fied thru demolition, breaking, what have you:


Caution:
CONCRETE MIX contains cement-itious materials and may cause irritation to lungs, eyes and skin. Avoid contact. Use only in adequate ventilation. Do not breath dust. Wet mixture may cause burns. Wear suitable gloves, eye protection and protective clothing. In case of skin contact, wash thoroughly with soap and water. In case of eye contact, flush immediately and repeatedly with large quantities of water and get prompt medical attention. In case of difficulty breathing, remove person to fresh air. If difficulty breathing persists, seek medical attention

http://www.rapidset.com/ConcreteMix_data.asp [rapidset.com]

If anything, it'll encourage those who are at risk to use the protection they should be using anyway.

Re:Concrete Roads

[TheFlyingGoat]

There's an alternative they're trying out in certain areas of Wisconsin. It's basically asphalt, but with a very high rubber content. They grind old tires into the asphalt. The net result is that it costs about the same to lay, and it can "heal" itself to some degree. The main concern is how safe it is when completely frozen, which is why it's only being tested in certain sections of freeway.

If it does prove to be a viable material to replace basic asphalt, it'll be great for Wisconsin drivers... we deal with slippery roads all winter then road construction in the spring, summer, and fall. If this can at least eliminate pothole patching, it'll pay for itself many times over.

Stone bends, too

[Zog The Undeniable]

The columns of some cathedrals - built before people understood roof trusses - are slightly but definitely bent if you sight along them. The percentage strain is very low, so they don't crack.

Re:replacing 2% volume reduces weight by 40%?

[elliotjo]

"Tiny fibers that comprise about 2 percent of the mixture's volume partly account for its performance."

The fibers are only one part of the improvement. The article also mentions replacing other major components in the concrete, including the bulk aggregate. Presumably the new components are also lighter and would account for the 40% reduction.

Dynamite, Anyone?

[zeromemory]

Is bendable concrete going to make it difficult to demolish structures built using it as the main material?

I don't think buildings made out of this stuff will survive a large enough explosion. Besides, concrete is really easy to break apart and chip (hence why you need to use rebar frames for serious construction), so just whacking away with chisel-tipped jackhammer should work for small jobs.

Re:replacing 2% volume reduces weight by 40%?

[valkoinen]

The increased strength makes it possible to use less of it to build structures of similar strength. You need 40% less of the fiber concrete to get the same strength as the traditional concrete.

Re:Whatever happened to ...

[goonies]

http://science.slashdot.org/article.pl?sid=04/03/1 1/1427213&tid=14 [slashdot.org]here it is

Re:Plastic or Elastic Bending?

[zeromemory]

Like other ductile materials, it will be elastic at low stresses, and will become increasingly plastic as stress increases.

True, but the most important factor in this case would be the lower yield strength (LYS), the point at which the transition from elastic to plastic behavior occurs. The article says very little about whether this concrete has a great LYS (deform elastically under everyday stress), or a small LYS (plastically deform even under little stress).

Re:Origional News Source at U of M

[goneutt]

A real civil engineering paper on this
http://www.engineeredcomposites.com/publications/2 005-2006/Keoleian%20J%20Infra%20Systems%25 [engineeredcomposites.com]
I've read over this, and it gives loads of info, but more for the CE, and as an ME student I'm looking for its Youngs Modulus, Tensile strength, cyclic lifespan. And I know they have real numbers for at least two of those, the pic physOrg uses is a UTM, a familiar machine.

The site owners are going to kill me but...

[Spy der Mann]

Here's a streaming video! [umich.edu]

(And here's the original article [umich.edu] from the Univ. of Michigan)

*already starts to feel guilty about the /. effect* :-(

Re:flexible Roads

[Andy Gardner]

Potholes are infact caused by the freeze thaw cycle. During the winter water seeps into the ground freezes and hence expands, pushing the road surface up. When ambient temperatures rise the ground thaws returning to its normal level but the pavement often remains raised, this creates a cavity under the pavement. The action of cars passing over the cavity causes the road surface to crack and fall into the cavity, the rest is history. This wear could be caused by a snow plough but i doubt it is the cause in the majority of cases.

As an iteresting side, damage can also be caused during the frozen period and occurs on motorways due to the increased speed and use. As a wheel passes over a raised frozen 'bump' the supension compresses. There is then a period when the wheel is airborne as the rebound of the suspension and weight of the car pushes the wheel back onto the surface. The repeated action of this leads to a spot on the road after the raised section that suffers increased wear. This promotes uneven wear of the road surface, thats why sometimes you will find a section of motorway that is rr eea llyy bb umm p p ppyyy.

Re:concrete submarine

[Anonymous Coward]

You're misinterpreting the Popular Mechanics article. These are not deep submersibles. The advantage of a concrete submarine, like the advantage of a WWII Liberty ship, is that it is cheap. That's it. Cheap. It doesn't perform better, it doesn't last longer, and if you're a civil engineer, you'd probably laugh at the idea of crawling into one and diving into the deeper depths of the ocean.

The WWII Liberty ship had a design life of 5 years and a "positive" ROI if it managed to survive its first (outbound) trip to deliver cargo to Europe. The entire vessel could be completed in an average of roughly 60 days. You could build them quickly using forms, you could build a lot of them using cheap materials, and they couldn't be sunk quickly enough to cut off the British from the American industrial complex. Now imagine the concrete submarine. Same principle, different wartime purpose.

Now the nerdly part. From a materials perspective, you're dead wrong.

To start with, the nit: Concrete has practically no tensile strength in comparison to steel - reinforced concrete design assumes that all tensile strength is provided by the embedded steel rebar.

Next, the myth: Concrete has good compressive strength - high strength varieties can have crush pressures exceeding 140 megapascals. Steel has much better compressive strength - high strength varieties can have crush pressures exceeding 2500 megapascals. Steel is stronger, but vastly more expensive. Concrete is weaker, but, literally, dirt cheap. Reinforced concrete is a practical compromise that optimizes economy versus loads for a particular design envelope (notice that modern skyscrapers do not have loads of reinforced concrete incorporated into their design).

Next, the mechanical nit: unless you've designed a perfect sphere, your concrete submarine will not only have to resist compression. Various parts of the structure will experience "tension" in response to bending moments and shear forces that resist the spreading tendency that will occur in a non-spherical, hollow form subjected to a pressure differential (tension is in quotes because I'm referring to subelements that are being pulled apart, not to the entire cross section as is normally the case). You can mitigate this problem by using pre-stressed concrete, so that the entire structure is under compression, but you will have spent a portion of your compression resistance to eliminate that problem. Steel makes your life much, much easier.

Finally, the materials problem: Concrete is porous and breaks down in marine environments as the salts attack the calcium hydroxide matrix, dissolving the cohesive minerals, depositing non-cohesive minerals, and splitting the crystalline structure like ice and the Old Man of the Mountain. Concrete is used in marine environments, but it deteriorates comparatively quickly. Now cycle your concrete though tens or hundreds of atmospheres of pressure in a marine environment. Your concrete will deteriorate even more quickly. Coatings will help, but they will have to be inspected frequently because of the frequent depressurization.

In conclusion, it would be a bad idea. The depth limitations of current deep submersibles are not caused by the pressure hull, but instead by more practical considerations like transport and life support. See http://www.unols.org/committees/dessc/replacement_ HOV/new_hov_brochure.pdf [unols.org] (PDF link).

Re:Only possible problems I see..

[BeBoxer]

How much does this road bend, also what kinda of deformation would we see from traffic. The current roads currently get grooves in them. But make a road that actually felxes, wht kind of effect would that have on the surface of the road? This to me would mean MORE maintaining the road, not less.

I think you'll find that the grooves you see are only on asphalt roads. Concrete roads don't get them. Asphalt gets soft when it gets hot, so the cars can sink in a little bit. Concrete roads never get soft. I suppose with huge traffic volumes an old concrete road could have grooves worn into it, but I think the concrete falls apart from cracks and such long before that happens.

Re:Concrete Roads: How about brick

[soliptic]

You Americans are funny ;-)

In this town, we have cobbled streets, still going strong from the Middle Ages...