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: 0) by Anonymous Coward on Friday June 23 2017, @12:07PM (1 child)
Use additional typographical symbols on level 3, brothers.
(Score: 2) by takyon on Friday June 23 2017, @12:15PM
At least it's not &mdaesh;
[SIG] 10/28/2017: Soylent Upgrade v14 [soylentnews.org]
(Score: 3, Insightful) by OrugTor on Friday June 23 2017, @01:38PM (4 children)
that the ring road gets its own cycle bridge. I wish the US could prioritize like the Dutch.
(Score: 0) by Anonymous Coward on Friday June 23 2017, @04:05PM (2 children)
It might help if the entire US had a mild maritime climate and was totally flat like the Netherlands.
(Score: 0) by Anonymous Coward on Friday June 23 2017, @06:08PM (1 child)
How would that help US cities treat bicycle traffic like first-class traffic?
Most cities are designed for cars and pedestrians. If you're on a bike, you need to choose to either impose on the space for cars or impose on the space for pedestrians.
Also, I've been wondering about this one for a while. Is a mild maritime climate and totally flat land the secret to a very low rate of teen pregnancy?
(Score: 0) by Anonymous Coward on Saturday June 24 2017, @01:03PM
The flatness and climate (and population density) are what make bicycling a practical choice of transportation in the Netherlands. Govt support for biking follows that.
(Score: 0) by Anonymous Coward on Friday June 23 2017, @05:50PM
You mean overrun our country with terrorists? No thanks man.
Also 52% income tax and another 21% VAT tax, yeah fuck yourself. You don't need a fucking bike bridge.
(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!!!
(Score: 0) by Anonymous Coward on Friday June 23 2017, @01:52PM (1 child)
"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"
THANK GOD - WE'RE SAVED FROM GLOBAL WARMING !!!!!!!!!!!!
The next logical step is to stop using cement altogether !
(Score: 2) by Unixnut on Friday June 23 2017, @02:34PM
> The next logical step is to stop using cement altogether !
Don't worry, the eco worriers are in full swing in that department too. Mud hut, or one made out of living fungi? Take your pick! :-)
(Score: 2) by butthurt on Friday June 23 2017, @01:53PM (6 children)
Pre-stressed concrete has been in use since the late 19th Century.
https://en.wikipedia.org/wiki/Prestressed_concrete [wikipedia.org]
(Score: 3, Disagree) by Immerman on Friday June 23 2017, @03:14PM (4 children)
No one is claiming otherwise.
What *is* new is pre-stressed 3D printed concrete. Basically they've figured out a way to incorporate one of the major concrete-strengthening technologies with the convenience and flexibility of 3D printing. I suspect this will prove to be a tipping point in bringing 3D concrete printing from limited proof-of-concept applications to more common real-world applications..
(Score: 2) by butthurt on Friday June 23 2017, @05:48PM (3 children)
> No one is claiming otherwise.
The summary could be read that way.
They haven't. The phys.org page says:
I found the original press release (no thanks to phys.org) at
https://www.tue.nl/en/university/news-and-press/news/16-06-2017-the-worlds-first-3d-printed-reinforced-concrete-bridge-starts-to-take-shape/ [www.tue.nl]
and it says exactly the same thing; phys.org simply reprinted the press release verbatim (including the "ne" typo).
However, I also found another report, which has a cut-away illustration of the bridge:
http://www.3ders.org/articles/20170619-dutch-cyclists-to-enjoy-benefits-of-3d-printed-concrete-bridge-following-tu-eindhoven-bam-collaboration.html [3ders.org]
You can see in that illustration that the steel cables are not incorporated within the printed form; rather, the printed part is sandwiched between two abutments (which don't appear to have been printed) to which the cables are attached. The accompanying video is narrated in Dutch, which I don't speak, but it shows workers manually adding the cabling.
http://www.youtube.com/watch?v=NrDjDcETbls [youtube.com]
It appears to me that the printer creates an unreinforced piece. The reinforcement is added externally by human workers. If you look at the photo on the phys.org page you can see that the printed form has a curlicue/arabesque shape. If a cable were dispensed from the print head as the shape were being printed, it would not be possible to stretch the cable before the concrete hardened, because the cable would straighten out from the tension.
A bridge in Shanghai was built with Styrofoam blocks inside it, to reduce the amount of concrete needed.
https://www.weirdasianews.com/2010/02/05/shanghai-wonderbridge-trash-collapses/ [weirdasianews.com]
There also exists foamed concrete, which can include "up to 80% air" according to one purveyor.
http://www.cemex.co.uk/porofoam-lightweight-foamed-concrete-for-voidfill.aspx [cemex.co.uk]
(Score: 2) by Osamabobama on Friday June 23 2017, @07:17PM
Furthermore, this implementation is actually called post-tensioned concrete, as the tension is added after assembling the bridge.
Wikipedia article [wikipedia.org]
Appended to the end of comments you post. Max: 120 chars.
(Score: 3, Interesting) by Dr Spin on Saturday June 24 2017, @09:05AM
A bridge in Shanghai was built with Styrofoam blocks inside it, to reduce the amount of concrete needed.
Many buildings in the ancient Roman world (ie from centuries before the time of Christ) used concrete with tiny clay
vessels embedded to keep the weight down in large dome structures. This is not a new technique, and people who
study construction engineering at reputable universities (or Google), should be fully aware of this technique, as well
as the one of embedding cables or wires and tensioning after the concrete sets, which I saw being done in the 1950's.
It remains the case that 3D printing in concrete gives you abilities never seen before, but these are mostly because
of the combination of speed and complexity of shape. In some cases, clearly, also because "trendiness" means more
effort goes in at the design stage. You can pour a lot of concrete for the cost of a highly skilled design engineer.
Warning: Opening your mouth may invalidate your brain!
(Score: 2) by Immerman on Saturday June 24 2017, @02:58PM
The only "First" I see is
> the world's first 3-D printed reinforced, pre-stressed concrete bridge
Wherein the "3-D printed" part is clearly mentioned first. You've got to have some pretty dodgy comprehension skills to convert that to a claim of the first pre-stressed concrete structure of any type. May as well interpret "Genetic engineers create world's first glowing rabbit" is a claim to have created the first rabbit.
Excellent in-depth information though, thank you. Even though it is very disappointing. I mean post-stressed concrete is definitely a step in the right direction, but it's not exactly new technology, and using it with printed concrete components verges on the blindingly obvious.
If they had prestressed the concrete, I would certainly not expect the cable to be fed from the print head, for exactly the reasons you mention. Instead, I would expect a second system to place and hold the cables so that they maintain tension along useful directions - potentially parallel to the printing, but not necessarily.
As for filling cast concrete with styrofoam or other filler, that's certainly old news (and foamed concrete is extremely interesting, there's even some promising cheap and low-tech DIY options out there that I'd love to try if I ever have the excuse) . What 3D printing offers though is well-ordered structure within the mostly-hollowed space in order to maximize the strength supplied by a given amount of concrete honeycomb, based on the specific loading requirements of the application. You could theoretically get comparable results by prebuilding a styrofoam-and-rod structure within your forms to create the desired hollows, in fact that might be much superior since you can avoid the inter-layer bonding issues, but that's going to be *extremely* labor-intensive in comparison.
(Score: 0) by Anonymous Coward on Friday June 23 2017, @07:04PM
No, but pre-stressing 3D printed concrete might be somewhat novel.
(Score: 2) by DeathMonkey on Friday June 23 2017, @06:41PM
A technical correction that adds nothing to the actual conversation... The best kind!
When you pre-stress concrete it's actually to prevent damage from sheering stresses. Concrete has a fairly high tensile strength already.