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Today the Built Environment department's concrete printer starts printing the world's first 3-D printed reinforced, pre-stressed concrete bridge. The cycle bridge will be part of a new section of ring road around Gemert [Netherlands] in which the BAM Infra construction company is using innovative techniques.
[O]ne of the advantages of printing a bridge is that much less concrete is needed than in the conventional technique in which a mold is filled. By contrast, a printer deposits only the concrete where it is needed. This has benefits since in the production of cement a lot of CO2 is released and much less of this is needed for printed concrete. Another benefit lies in freedom of form: the printer can make any desired shape, and no wooden molding frames are needed.
They have managed to not only 3-D print concrete, they have also developed a technique to lay down a cable within the concrete so that it can be 'pre-stressed' — avoiding tensil stress.
The researchers successfully tested a 1:2 scale model under a 2000kg load.
(Score: 3, Insightful) by Runaway1956 on Friday June 23 2017, @01:41PM (5 children)
I'm simply not in any hurry to take a vacation in the Netherlands to test this idea. They use less concrete? Interesting idea. But, engineers already use as little concrete as possible. It's not like an engineer gets a huge kickback from the concrete plant or anything. New and different shapes? Again, interesting. They're going to use spheres and/or egg-shapes? Nope, I didn't think so. Besides which, the carpenters can already form just about any shape you want formed up. If you WANT a sphere, you can find a crew to form it. If you want a hollow sphere, that can be done as well.
I think I'll wait a good long while, and see how this works out for them. That scale model? Have they actually put it to the test, with traffic crossing it routinely, in fair weather and foul, both hot and cold? Didn't think so.
This reminds me of those claims for various items, "it will last a thousand years". Uh-huh - the doohickey was only invented twenty years ago, and this new model was designed last year, but you've somehow stressed it enough to guarantee that it will last 1000 years?
Call me a luddite, I don't care. I'll believe it when it's been tested in real life, under real life stress, for a couple decades.
(Score: 3, Informative) by Immerman on Friday June 23 2017, @03:08PM (1 child)
Granted, simple shapes like spheres, and even hollow "eggs" aren't incredibly difficult to cast, though they will still add substantially to the cost - takes a lot more man-hours to build the forms for a fairy castle than for a rectilinear slab. Where 3D printing gets *really* interesting is in doing things like honeycombed interiors, which can give you most of the strength of a solid casting while using almost as little material as a hollow casting.
And obviously the initial designs will be fairly conservative - radically new designs that exploit the advantages of a new manufacturing technology take a lot of time and effort to develop, and are particularly risky when the claimed advantages haven't actually been thoroughly tested in the real world. Give them some time - once the new technologies have been tested and proven in terms of strength, durability, and cost-effectiveness, then the architects will begin to explore its non-traditional capabilities far more fully.
(Score: 0) by Anonymous Coward on Friday June 23 2017, @03:45PM
There is a potential danger with using so little concrete in a "bracing" manner rather than a solid, bulk manner: the concrete in the "less material is used" structure is suddenly more critical. If it cracks or weathers away, failure will happen sooner than with a bulk cast concrete structure.
(Score: 2) by bob_super on Friday June 23 2017, @07:23PM (1 child)
> Call me a luddite, I don't care.
That computer you used to post this message was designed by people who knew how materials behave under stress and over time.
That SpaceX launch I just watched, was also made possible by engineers who know how materials react.
Why wouldn't something as ancient as concrete have a predictable behavior?
(Score: 2) by Runaway1956 on Saturday June 24 2017, @12:38AM
Just because the material is predictable, doesn't mean that we have a perfect understanding of that behaviour. When there is less concrete in the structure, how does that affect spalling? Is that perfectly understood? Or, have they found a way to prevent it?
(Score: 0) by Anonymous Coward on Friday June 23 2017, @08:27PM
Short version:
It's all about me!!!