super flexible concrete, Full story at http://www.physorg.com/news3985.html

http://www.physorg.com/news3985.html

Okay, so it"s 40% lighter, and 500 times more resistant to cracking. But what about strength? From the looks of it, this stuff is SO flexible that it would be absolutely useless in structural applications. I see only references to roadway tests in the article. If a beam or a girder made out of this stuff behaves like the picture in the article shows, then it is more ductile than steel! Brittle failure in concrete is a concern in structures, and this material supposedly will alleviate that concern. But you can"t build something out of spaghetti noodles. Sure, you won"t have brittle failure. But you won"t be able to hold any loads, either!

/sign

What she said.

I think the point of the picture is to show that a load that would normally cause concrete to fracture now causes a more ductile response .. agreed it would helpful to show the load strength and a comparison chart, but I suppose you can find this elsewhere.

I understand the comments that have been made by the others so far, but from the looks of it, I think that there would be a difference if you consider the thickness that you would be building structures. I think the picture and the information that is shown is to exagerate the ablity for the concrete to flex without breaking or cracking. I am sure that it would not be exactly the same as bending steel, because it seems as if the concrete reforms the original shape, but if you lay a flat piece of steel on its side, it bends pretty easy. If you stand that same piece of steel upright, well I think we would all agree that the strength would be improved, as well as if you were to stand that thin piece of flexible concrete on its side, I am sure that the strengths would increase, but you would still have the flexible capabilities to withstand vilolent forces in nature. I would think that if you would try to get any type of compressive strength or flexural strengths out of the same thickness shown in the picture with "normal" concrete, I would assume that you wouldn't expect to see any at all when it is laying flat.

I do have a couple of questions for the designers. The first is the economical stand point for construction. How much? And how many companies would be able to mix this concrete from day to day? Is there a special plant that mixes it? Or can you mix it in any plant? How many admixtures and silos would a contractor have to have to support this? Are the materials used to make this mix readily available? Are there any special constraints for finishing after placement? Skid resistance etc.?

Would the designer be inclined to try it out on a White-Topping? (Ultra-Thin Concrete Overlay).

I assume this is not reinforced with rebar or someother material.. besides the fibers, so if it was reiforced maybe it could be used structurally.

For engineerchick
YEAH! Stupid scientists. Can't even put metal in the microwave! All you with your "THEORIES", so called, on evolution, and faked moon landings... [joking - take it easy... just going with the national flow here...]

I'm sure the primary application for this will be roads, but girders & beams aren't made of concrete. We use concrete to hold the girders and beams together in a large structure or for the flooring and walls. Using it as a foundation or structural cement would seem more than reasonable, especially in seismic zones where minor shaking of the structure (and the current brittle nature of concrete) can render a building useless. And at 40% lighter, the total load on the foundation and the structure itself is reduced, so even if it's 10% weaker, you still have a lighter building held together with material that will flex under load (instead of splinter). Sounds good to me...

I saw a few months ago an 'inflatable concrete' for use in making field hospitals - I wonder (if at 40% lighter) this would work for them?

fiberglass composite is stiff, but the stiff comes from the sandwich (wood/foam/coremat/honeycomb). fiberglass itself is not so stiff.

engineergirl, you're just not right. I don't have any more detailed knowledge of that material than this article, but you only reference the picture and you certainly can not tell from that picture how much load is being applied (except that it's probably a lot, based on the equipment used.)

In really, really rough broad terms a material has a bulk modulus (resistance to bending) and a toughness (deflection before it breaks). A ceramic dinner plate has a fairly high modulus but a very low toughness (hard to bend, but then it cracks) A cheap aluminum plate has a very low modulus and a high toughness (easy to bend but it doesn't crack immediately) A good steel plate could have a pretty high modulus AND a high toughness - depending on what you put in it. Usually the highest mod steel we have has a low toughness and vice versa - but that doesn't mean that 10 years later we won't have one that beats both of the older ones.

Most steel has a higher modulus than concrete, and steel is tough enough that they sometimes ship it in a coil. So it's certainly not impossible to be very good in both traits.

Furthermore, you certainly can bend a steel beam like that picture shows. I wouldn't USE that beam afterward, and I certainly wouldn't design for that kind of load, but it certainly could be tested to that point. They may well have been destructively testing that piece of concrete...

Just from eyeballing that picture, I'd say a fair number of steel beams undergo a significant fraction of that deflection as part of their design - many of them shipping "prebent" so that they are flat after load is applied.

The most obvious example of this is to see an container semi-trailer that doesn't have a container on it (it's basically like a flatbed semitrailer without the bed) Usually the length in the middle is a beam that will have a very noticeable upward bulge.


There aren't very many applications that come to mind where a this kind of toughness would actually make the material less desireable (other than cost and things already designed for something else) The only application that comes to mind is bulletproof armor ceramic inserts, because they disperse a lot of energy BY cracking. (Not to say that this kind of ceramic is the same as concrete - which is a composite - but I'm referring to increased toughness alone)

Alternative reinforcement with similar properties has been around for a while from companies like <a href="http://www.polytorx.com/">PolyTorx</a>.

from what it looks like its not real easy to bend if they needed a hydrolic press to bend it

I just happened to read the article this morning... interesting concept. After having been closely involved in the planning & construction of several buildings (the latest 44 condo project of concrete and cinderblock constuction and not one wood 2x4 in the entire structure) I read a couple of the posts. Here is my take.... Flexible yes, strength, durability, light weight... for a bridge material coupled with other traditional methods and materials this could really be a useful product in colder climates and natural disaster prone areas. The uses I see for everyday people there could be a number, roadways, sidewalks and possibly layering driveways with a hardened traditional concrete below with a cover of this newer product above or to shield the basements of homes. Possibilities are only limited by the mind. As for those who say what good is it you can't make anything out of noodles... well this doesn't have to be a universal replacement for all traditional concrete. It will have applications where it outshines regular concrete and where it will fail compared to regular concrete. Compare it to the glue on post it notepads. You don't try to glue a chair with that stuff it just doesn't work... every situation is different. I think I would be an investor in this product. One last thought... Length, depth, width all play a part in flexability. Obviously a 4 ft cube of this new material would not have the same properties as the photo they showed above... I think that some posters need to go back to school and study loads, and applications before they post. I too would like to know the cost and availability of the product, along with the more technical fine print.

r6mtn: good point. I hadn't thought of it that way.

Sgt_Jake: not sure I understand what you're saying. Girders and beams aren't made out of concrete? Then why are there sections in the code on how to make beams and deep beams out of concrete? (ACI 318-02 chapter 10, Flexure and Axial Loads) Why is beam design such a significant portion of Concrete Design courses? I do agree with you about foundation applications, though. Again, hadn't thought of it that way. I read about those inflatable hospitals, too. Those things are COOL!

XIG engineer: Thanks for clarifying all that.

Believe me this is cutting edge stuff. Industry might get to use this in 10 years on a beginning level. As far as load carrying, that's not the primary concern. Tensile strength in traditional concrete is about 10% of the compressive strength so cracking under tensile loads (ie thermal stresses, etc.) has always been a problem. Hence rebar which has wonderful tensile strength.
This would make thermal problems basically go away so huge pours could be done continuously rather than split up into sections making cold joints. The problem of course would be deflection. You would just have to design for large deflection which would be a big problem in some structures. This stuff would be perfect for road overlays though. No cracking when the underlying foundation settles so you could probably have a pavement last 10 times as long as normal with only a thin overlay.

but what I do know...

How cool to be involved in that kind of project! You must feel very privileged. I am a very recent graduate, working with a really great CE firm and heading back to graduate school soon, so I haven't had all that many opportunites yet, to be a part of a large-scale project like yours. I do realize that my lack of real-world experience is a disadvantage (although, it's to be expected, since I just got out of school, don't you think?), and I hope that someday I can be as experienced and knowledgeable about this stuff as you appear to be.

I shouldn't have put that post up so quickly (judging from the number of "you're wrong!!" posts on here) , but I was simply expressing the first thoughts that came to mind after I read the article. There have been some awesome rebuttals that have reminded me of some things that didn't jump to mind during my initial post, and I appreciate that!

Hope to learn more, as more people post stuff!

The test they are showing is a flexural strength test. Normally they cast beams about 6x6x24 or so and the things are so weak in tension you can barely put 2000 lbs on it before it cracks. Drives lab technicians nuts because the tests have such a large uncertainty at that level of load. So, yea the pic is a demonstration of the elasticity, not an actual testing condition. No one tests for flexural strength with that cross section. I'd love to see the compressive strength on these.