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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.
I wonder if this new concrete may enhance the concrete submarine programme for deep submersibles.
Being in something with a bit more toughness, and better tensile strenght might be more reassuring. A little less like going to sea in an eggshell.
Maybe a flexible road may not be able to stop the water penetration, but might be able to return (or be pounded) back into its original shape? A small crack stays small, even after many ice expansion cycles, rather than turning into a massive pothole?
...can it withstand the impact of a jet airplane?
And is it safe to inhale the fibers if said airplane makes a big ol' mess?
Concrete roads are far more resiliant to wear than asphalt/tar roads, this means (generally) less repair work. This is a major factor when you're dealing with a massive arterial system.
Overall concrete roads and asphalt tend to work out the same in terms of costs (over a period of years), concrete being more expensive to lay but lower repairs and vice-versa for asphalt.
The architects, contractors, and construction workers of the Petronas towers in Kuala Lumpur simultaneously shout, "D'oh!"
From what I remember of watching a documentary on the construction of the Petronas towers, the primary concern of the engineers was the compressibility of the concrete -- each floor has to withstand the weight of the numerous floors above it. Flexibility was the least of their worries.
Furthermore, the two towers are located on a relatively 'soft' foundation -- they essentially 'float' on sea of soft land. The towers aren't anchored to the bedrock. Additionally, the bridge that connects the two towers is designed to allow the towers to move towards and away from each other. Thus, the towers stabilize each other and are quite flexible. According to the documentary, if you watch the water in the upper-level toilets on a windy day, you'll see it swooshing around.
I'm Trappped at Berkeley.
How do you know that ? The article makes no mention of what the fibres are actually made of, let alone what their temperature response is. And how would they catch on fire if they are inside the concrete ? It would have to crack open to expose them to oxygen before that could happen, presuming that they are even flammable in the first place.
buildings that bend and shift better under harsh weather conditions such as wind and rain
Although it's good for a structure to have some flexibility under periodic loading (earthquakes, winds, etc.), the U of M article mentions applications like expansion joints and roads. In an expansion joint, the component is expected allow displacement to reduce pressure on other parts. Just think about a simple bridge with 2 expansion joints on both ends. Temperature changes will cause the bridge to expand/contract. Rigid joints on either end would prevent the structure from deforming freely so there would be a lot of added stress. The amount of force to resist this expansion/contraction is huge, (Any second year civil engineering students can back me up with some numbers) thus the need for expansion joints. The joints themselves aren't doing any significant load-bearing.
Compare this to a building where much of the structure is supporting vertical loads (gravity). Imagine if a column was made from this stuff, nothing could depend on it for structural support due to its inability to resist deformation. So everything this column (or beam) is trying to hold up comes tumbling down. Just look at that video where the beam completely bends under the load.
Flex in structures is good in hurricanes and stuff, but it doesn't do much good if it can't even hold itself up.
because the concrete is thinner, not because the concrete is lighter. This discerned from RTFA. We poured a pad for a picnic pavilion at the yacht club using concrete that is reinforced with polyethylene fibers. It allowed us to pour a large pad that will not crack without having to use tiebacks. Which brings to mind something I've often wondered about...
With concrete, when it's pre or post stressed in compression, it's much less likely to crack. Traditionally this is done by tensioning the steel prior to pouring or tensioning cable or rod 'tiebacks' after partial curing. Now this is very nice but... It should be possible to engineer a fiber that will shrink as it ages and bonds well as an aggregate. If the shrink time could be matched up reasonably well with the cure time of the concrete it would simplify many types of construction.
Concrete was the first material that was used in the construction of mass use roadways back in the early days of the automobile as asphalt hadn't been discovered yet. Theres a very good chance that the concrete roads you drive on today were laid back in the 40s and early 50s. But concrete was always expensive to use, and required extensive preperation of the ground in order to pour it. So it was a slow and tedious proces, and not many cities could not afford to have more than one crew going at a time.
When it was discovered that Asphalt, a by-product of oil refining, could be mixed with a small sized aggregate *gravel* and basically smooshed ontop of any roughly prepared surface to create a roadway, well that was the end of using concrete. Most concrete projects were abandoned overnight and roads started being laid at a fraction of the price and at triple the speed.
The one caveat is that in Northern Areas it was discovered that asphalt roadways were not holding up as long as their concrete breathern. Many asphalt roads were having to be torn up and replaced every other year due to extensive freeze damage. Many cities went back to using concrete for their roads, until better techniques of preparing the roadbeds were discovered. Which were to compress and smooth the roadbed as much as possible, then lay a barrier layer of aggregate *gravel* on top of that to help with drainage and settling, then to finally slope the finished road from the middle to the edges for increased water run-off.
...will it have the same (or better) coefficient of friction than normal concrete? Sure it might not crack, but if your tires don't stick to the road, then you're going to have more problems...