3D-printed concrete bridge doesn't need supports:
3D-printed concrete bridge doesn't need supports
Concrete is the most consumed material in the world, second only to water. The material is pervasive because it has many practical uses — from building homes to forging dams that protect from storm surges. Reinforced concrete, concrete with steel embedded in it, is a foundation for the infrastructure of many essential industries: education, healthcare, transportation, government, and more. It would be next to impossible to live without reinforced concrete.
But the 2.8 billion tonnes of CO2 concrete emits falls just behind the total emissions of China or the United States — the two countries with the most CO2 emissions, reports Yale Environment 360.
Emissions aside, concrete thwarts natural habitats, covers and chokes ecosystems, and heats cities. We produce more concrete every two years than the plastic made in the past 60 years. Planet Earth is becoming a concrete world. And the steel used for reinforcement and the cement that binds the concrete together are at the heart of the problem.
[...] A team from Zaha Hadid Architects, ETH Zurich, and the Block Research Group decided to remove the reinforcement to build their approximately 39×52 foot arched pedestrian bridge.
While their construction methods harken back to the classic masonry arch construction, their materials are novel, with angled blocks arranged in an arch. They 3D printed concrete and applied it at right angles instead of pouring it horizontally. In doing so, they built a strong bridge without the added steel.
Due to the design, the loadbearing concrete structure uses significantly less material overall — including no steel or mortar. And, due to the bridge's geometry, the angular blocks transfer the load to the footings, keeping the entire structure stable. And because it doesn’t need mortar, the bridge can be taken apart and reassembled elsewhere.
(Score: 5, Insightful) by driverless on Monday August 16 2021, @11:03AM (6 children)
This experiment worked because it sets the concrete in compression. If you need to deal with tensile stresses, which you need to do most of the time, you need reinforcement.
So this is the answer, if you phrase the question very carefully.
(Score: 0) by Anonymous Coward on Monday August 16 2021, @11:44AM
what do you have against a domed ceiling?
or are you complaining about the bulged floor?
(Score: 3, Insightful) by KilroySmith on Monday August 16 2021, @05:49PM (1 child)
>>> if you phrase the question very carefully.
And that's my takeaway - with a desire to reduce CO2, one can design structures using this building technique - but they may not look the same.
We love to design and build concrete things that require reinforcement - we build horizontal bridges over highways because we CAN with reinforced concrete. If we built arched bridges instead, perhaps we could radically reduce the amount of steel and concrete in them.
(Score: 0) by Anonymous Coward on Friday August 20 2021, @09:25PM
Wouldn't they use more to cover the same span?
(Score: 3, Informative) by Anonymous Coward on Tuesday August 17 2021, @02:37AM (2 children)
Yes, only works in compression and in areas with no risk of seismic activity.
It does not appear there is anything in the design except friction between the segments to prevent lateral movement during an earthquake.
I don't recall the site's name, but there is a ruin in Bolivia where the builders (not Aztec nor Maya) cut pockets into the sides of stones so the pocket cut into the adjacent stone lined up. These either were filled with a single small stone, cut to fit the void created when the two larger stones were brought together, or they were filled with bronze. Some sort of locking like this would address the lateral movement concern (although it would more likely be a mortise and tenon arrangement for 3d printed structures).
(Score: 3, Informative) by Runaway1956 on Tuesday August 17 2021, @07:59AM (1 child)
I think you are referring to Tiwanacu and Puma Punku.
https://blog.world-mysteries.com/mystic-places/ancient-ruins-of-tiwanacu-and-pumapunku/ [world-mysteries.com]
These ruins predate the Inca empire, but the Inca probably took it over. Their construction was impressive as well, if different.
https://en.peru-spezialisten.com/machu-picchu-construction-technology-full-of-fascination/ [peru-spezialisten.com]
Abortion is the number one killed of children in the United States.
(Score: 0) by Anonymous Coward on Wednesday August 18 2021, @03:47AM
Yes, it was Tiwanacu.
(Score: 4, Insightful) by MIRV888 on Monday August 16 2021, @11:05AM (5 children)
While this sounds fantastic. I would need to see a bridge built to scale and tested over a period of years before I would trust it. If any of those blocks crack, you will lose the whole structure.
(Score: 0) by Anonymous Coward on Monday August 16 2021, @12:52PM
after all, we all know the roman empire fell because their bridges fell.
(Score: 2) by Runaway1956 on Monday August 16 2021, @06:18PM (3 children)
That's my take as well. I watched all the videos on that page, including the 4 1/2 minute one. What this particular bridge amounts to, is a sculpture in a park, for people to ooh and aah over. They pretty obviously chose nice firm, well-drained ground to put up the sculpture.
Is this design suitable for vehicular traffic? Vibrations and impacts at joints may destroy this design in short order. For the sake of argument, let's say that it's only good for foot traffic. Then they need to find sites suitable for this design, and put up some pedestrian bridges, and put them to the test.
Is spalling eliminated? If not, how does spalling affect the bridge over time? With solid blocks, spalling might be acceptable for quite a long time. With these hollow blocks, minimal chipping might be fatal in the short term.
Abortion is the number one killed of children in the United States.
(Score: 0, Insightful) by Anonymous Coward on Monday August 16 2021, @07:30PM
Sometimes, you spall just so much, that it is better to runaway. Sometimes not. It is just that I have nothing to say.
(Score: 2) by Reziac on Tuesday August 17 2021, @02:16AM (1 child)
I'm reminded that cinder blocks, which are hollow and (nowadays) mostly air, are really strong until they're not, and the wrong sort of stress or impact easily shatters them. (Old time blocks were a LOT stronger.)
However this gave me a different thought: why are we not using waste plastic, molded into slabs and blocks, for stuff like road surfacing? so what if it might need to be thick; it's waste, and there's lots of it. It's used as a substitute for concrete in portable curbs, so...
And there is no Alkibiades to come back and save us from ourselves.
(Score: 0) by Anonymous Coward on Tuesday August 17 2021, @02:41AM
Those cinder blocks, if created in an area that still has coal fire power plants, probably contains waste products from the power plant. Ditto dry wall sheetrock panels.
As for roads, ground up tires and crushed glass have both been added to asphalt.
(Score: 4, Interesting) by surjeon on Monday August 16 2021, @11:45AM (2 children)
Does anyone see how taking the steel out significantly reduces the CO2 output? Sure steel has environmental impact, but it's nothing to calcination of limestone to make cement.
Now if there's less cement, that obviously helps, but doesn't that just make weaker concrete?
Is the advantage of 3d printing that it can have voids in the structure? That's not mentioned. Otherwise I don't see how using weaker concrete with no reinforcement in a geometry that precludes having anything under tension can use less material.
(Score: 0) by Anonymous Coward on Monday August 16 2021, @02:18PM
It is the lack of tension that reduces the amount of material required due to concrete having much better compressive strength than tensile.
(Score: 0) by Anonymous Coward on Tuesday August 17 2021, @02:50AM
Steel causing spalling is a major reason for having to raze and re-build concrete buildings, bridges and other structures (the steel rebar rusts, expands, and breaks apart the concrete structure from the inside). Spalling is why modern concrete structures are usually replaced after decades, and Roman concrete (no rebar) has lasted for centuries.
But, better than going back to Roman times, and using no reinforcement, is to use basalt fiber reinforcement and basalt rebar. The basalt rebar is a drop-in replacement for steel, and mixing in some chopped basalt* fibers helps prevent any cracking in the concrete. Concrete that lasts forever and is seismically safe.
* glass fiber is also used, but glass fibers must be coated to protect them from the cement which otherwise degrades them before it cures.
(Score: 2, Insightful) by Anonymous Coward on Monday August 16 2021, @12:49PM (6 children)
> It would be next to impossible to live without reinforced concrete.
It would be next to impossible to live our current modern lifestyle without reinforced concrete.
ftfy
We are here, our ancestors must have lived without reinforced concrete--as hard to imagine as that might be /s.
(Score: 2) by Acabatag on Monday August 16 2021, @02:11PM (5 children)
We could not live packed tight in high density housing without lots of concrete.
(Score: 0) by Anonymous Coward on Monday August 16 2021, @04:49PM (4 children)
And that's bad? We could be living in trees eating fruits and using waterfalls for showers.
(Score: 0) by Anonymous Coward on Monday August 16 2021, @04:54PM (2 children)
Don't knock it, I spent a summer camping and did pretty much that. Not the worst summer I've ever had. A picturesque small waterfall in the Finger Lakes region of NY State (where there are many small falls carved into limestone) provided the shower. Cold, but so much water that I hardly needed soap to get clean.
(Score: 1) by Acabatag on Monday August 16 2021, @05:35PM (1 child)
I live in a woid frame house on 5 acres. The foundation is cement but it's century old cement. Our mortgage payment is about $900 so it's not bad. We are close enough to town that it's a 15 minute bike ride.
(Score: 0) by Anonymous Coward on Friday August 20 2021, @01:17AM
And i live in a Van down by the River!
(Score: 0) by Anonymous Coward on Friday August 20 2021, @09:28PM
(Score: 0) by Anonymous Coward on Monday August 16 2021, @01:09PM (1 child)
Do the figures for China and the United States include the CO2 from cement made in those countries? Alternatively do the cement numbers exclude those already included in the figures for those two countries?
(Score: 2) by HiThere on Monday August 16 2021, @02:06PM
No and no. But those are still important figure to bear in mind. E.g. it implies that IF one could eliminate concrete, that would reduce the CO2 emitted by both China and the US substantially. Unfortunately, I don't think this project demonstrates that.
Javascript is what you use to allow unknown third parties to run software you have no idea about on your computer.
(Score: 2) by krishnoid on Monday August 16 2021, @08:45PM (1 child)
What *is* concrete, chemically (and/or structurally)? I mean, there's some structural component, there's some "glue" that mixes with water and isn't a binary epoxy, there's some setting process, but ... ?
(Score: 2, Informative) by pTamok on Monday August 16 2021, @09:18PM
Dumb answer:
Wikipedia:Concrete [wikipedia.org]
(Score: 3, Interesting) by Nuke on Monday August 16 2021, @10:24PM (1 child)
This idea is several thousands of years old.
WTF is the fuss about?
(Score: 0) by Anonymous Coward on Friday August 20 2021, @01:20AM
It's 3D printed, and can be a gun.