
“Reversible Concrete” May Revolutionize Temporary Architecture - bemmu
http://thecreatorsproject.vice.com/blog/mits-reversible-concrete-is-ready-to-revolutionize-temporary-architecture
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tcdent
That's a deadly mass of material. In the video, when they're taking the mold
off, the trajectory from the top of any falling chunks is super sketchy, too.

Would be interesting to see destructive tests. They obviously have digital
designs, but could those be accurately used for simulation?

I'm sure they know what they're doing, they've wearing matching overalls.
Those are just some concerns I'd have about constructing and exhibiting such a
thing.

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brenschluss
I've held those rocks - the material is porous and super light, almost like
styrofoam.

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tcdent
You're right. It's not gneiss as the article says, either.

[http://www.misapor.ch/EN/Home.html](http://www.misapor.ch/EN/Home.html)

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teddyh
When I saw the title, my immediate question was “Reversible _by who_?” The
answer seems to be: everybody. With such a structure, _anybody_ could come
along and knock it over by simply pulling out the loose string. I’m not sure
I’d want to use this for anything important.

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JulianMorrison
Or giving it a solid shove, by the looks of it. It seems stable against only
its own weight.

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Asbostos
A similar effect can already be done by entirely conventional means.

[http://www.stone-ideas.com/2015/01/11/gabions-product-
area-g...](http://www.stone-ideas.com/2015/01/11/gabions-product-area-great-
potential-artists-designers-alike/)

Gabion:
[https://en.wikipedia.org/wiki/Gabion](https://en.wikipedia.org/wiki/Gabion)

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dkbrk
I don't know how useful this will be. I think being made from crushed gneiss
in a jammed configuration, it should be fairly strong in pure compression.
Bending stress would probably cause failure quite rapidly, and I think it
would steadily weaken with vibrations of sufficient amplitude, especially if
it wasn't loaded.

That said, I really don't care just how useful or practical this is because
it's already so damn cool. That trick with the string is very clever and I
would love to see the mathematical model they use for planning its path.

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justinph
I'm not a materials scientist, but I bet this has a good deal of vertical
strength, but almost no lateral strength. Probably limits its utility quite a
bit.

But, still really interesting.

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jostmey
Concrete is awesome because you just pour it into a mold and it dries. With
this technology it appears that you still need a mold and you have to take the
time to layer it.

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sparky_z
Expanding on what x3n0ph3n3 said, concrete doesn't harden because the water in
it evaporates away. Rather, the water is consumed in a chemical reaction. In
fact, you have to be careful that the water doesn't evaporate too much during
the curing process. It's very common to hose down a curing sidewalk and keep
it covered for 30 days.

Incidentally, the chemical reaction is exothermic. That's one of the reasons
why you can't pour a concrete dam all at once: the heat generated would be
enormous.

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iamcurious
Impressive, they use a 3d printer but it seems like it could be done by hand.
Which would make for a fun craft project. "Today we will knit an scarf,
tomorrow a wall!"

Still, it does seem like it would erode quickly and the article doesn't says
if it could withstand a platform on top.

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vinceguidry
I bet it could support a great deal of weight. Right by my coffee shop one
year the side of a creek collapsed, they built a huge retaining wall with
exactly this kind of gravel. They would dump it in 10x8x8 wire crates and
stack the crates on top of each other. The article said it was gneiss gravel,
that stuff takes awhile to erode. It's not like concrete at all, much much
stronger.

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markbnj
This is interesting, and the technique is certainly surprising to me, but I
don't think "reversible concrete" is a reasonable way to describe what has
been produced. Perhaps it is a lot more stable than it looks, but what about
compression loads?

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hugh4
What about a good rainstorm and an overnight freeze?

