
What is Concrete? - mikecarlton
http://gizmodo.com/what-is-concrete-1721627320
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dstyrb
Cool stuff -- author doesn't mention that Roman cement had a usability life of
>2000 years, while Portland cement starts to degrade after 50 years (for rough
harbor usages).

[http://www.bloomberg.com/bw/articles/2013-06-14/ancient-
roma...](http://www.bloomberg.com/bw/articles/2013-06-14/ancient-roman-
concrete-is-about-to-revolutionize-modern-architecture)

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bane
One of the really surprising things when you visit the Colosseum in Rome is
how _modern_ a structure it feels. Rather than ruins, it feels more like a
construction site, a half-finished stadium for some up coming Olympics or
World cup.

It's not just two Greek amphitheaters dug into facing hillsides...it's
something on a completely different level.

All this despite being left in complete, abandoned ruins for something like a
_thousand_ years. Then damaged in earthquakes, stripped of stone (probably
also concrete blocks) for other construction, legend has it's been used by
monastic orders, as a wool factory and other crazy uses.

This isn't modern reinforced concrete, it's _just_ concrete.

If you wonder around Rome you come across possible the pinnacle in concrete
work in human history, the Pantheon. I've heard that we _still_ don't know how
they produced the dome, another nonreinforced wunder construction that's
survived for millenia. Again, survived earthquakes, wars, and other uses, and
again a huge structure that feels amazingly modern in size and scope.

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rsync
"I've heard that we still don't know how they produced the dome, another
nonreinforced wunder construction that's survived for millenia."

We didn't, but we do now. It has recently been fully understood to have been
volcanic ash mixed into the concrete that makes it so strong and stable.

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

[http://www.romanconcrete.com/docs/spillway/spillway.htm](http://www.romanconcrete.com/docs/spillway/spillway.htm)

~~~
bane
my understanding is that the density (and thickness) of the concrete changes
as the dome moves inward from the walls to the oculus, and we have no modern
method for reproducing such a constant density variance

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lingben
it still boggles my mind that Rome has working sewers that were constructed
more than 2000 years ago and there is every indication that they will last
another 2000 years of continuous use

[http://www.bbc.co.uk/programmes/b05xxl4t](http://www.bbc.co.uk/programmes/b05xxl4t)

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andrewl
The book _Stuff Matters: Exploring the Marvelous Materials That Shape Our Man-
Made World_ has a chapter on concrete. The self-healing concrete was
completely new to me. Definitely worth a read, and not just for the concrete
chapter:

[http://www.goodreads.com/book/show/18222843-stuff-
matters](http://www.goodreads.com/book/show/18222843-stuff-matters)

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ubasu
See the concrete canoe competition:

[https://en.wikipedia.org/wiki/Concrete_canoe](https://en.wikipedia.org/wiki/Concrete_canoe)
[http://www.asce.org/concrete-canoe-photo-
gallery/](http://www.asce.org/concrete-canoe-photo-gallery/)

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bbcbasic
Another interesting property of unset concrete is that it can burn your skin
due to alkalinity.

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IgorPartola
Meta comment: I often times find great articles on Gizmodo. While other Gawker
sites like Lifehacker are more mediocre, Gizmodo often features interesting
and more in depth posts like this one.

