26 ms·

Pedant: Cement != Concrete. Cement is one component of concrete. Concrete is composed of water, aggregate, and cement. The video linked to by Gates' blog says[

by bch 12y ago

Pedant: Cement != Concrete. Cement is one component of concrete. Concrete is composed of water, aggregate, and cement. The video linked to by Gates' blog says[0] "The most important material in terms of sheer mass in our civilization is cement made into concrete" "The chinese poured into their buildings and roads [...] as much concrete in just 3 years as United States in 1 century". "In modern times, researchers have experimented with the addition of other materials to create concrete with improved properties, such as higher strength, electrical conductivity, or resistance to damages through spillage."[1] There's more available[2] to concrete these days than what the US infrastructure used up to 2000[3]. Not that 3 years consumption > 100 years consumption isn't impressive, but: 1) not only are we not comparing the same period 2) it's not clear we're comparing the same material I often hear cement and concrete used interchangeably, but had the difference drilled into me when I worked (doing computer work) in the industry briefly. For that reason (cement != concrete) and potential advancements in concrete (maybe there are new composites that let us use a fraction of what used to be necessary?) it's not entirely clear what the numbers mean, outside of "China is growing fast". [0] https://www.youtube.com/watch?v=xi7O9pmM_A0&feature=youtu.be&t=54s https://www.youtube.com/watch?v=xi7O9pmM_A0&feature=youtu.be... [1] http://en.wikipedia.org/wiki/Concrete#Modern_additives http://en.wikipedia.org/wiki/Concrete#Modern_additives [2] http://www.columbiatribune.com/editorial_archive/pollution-eating-concrete/article_c82246f6-5cfa-11e3-9f03-10604b9f6eda.html http://www.columbiatribune.com/editorial_archive/pollution-e... [3] https://img.washingtonpost.com/blogs/wonkblog/files/2015/03/making-the-modern-world-cement-A_800_v2-11.png https://img.washingtonpost.com/blogs/wonkblog/files/2015/03/...

thinkpad20 12y ago
The linked article makes this clear: > In case you need a refresher, cement is a powdery lime-and-clay substance that is combined with water and gravel or sand to make concrete.
jacquesm 12y ago
Anybody that does not understand the difference between cement and concrete is going to be in for a surprise when they mix up a batch of dark gray goop and try to use it for something in construction. The shrinking alone will cause some interesting effects. There are a lot of lay-man misconceptions about concrete, one of the more persistent ones is that concrete needs to 'dry'. It doesn't, it needs to cure, it's a chemical reaction that gives concrete its strength, not something going into solution to allow pouring that then dries and solidifies. Concrete is very interesting material, its history is fascinating and the materials science behind it as well. Such a simple thing in principle, so incredibly complex. Just like glass another one of those materials with vast depth.
- Osmium 12y ago
  > Concrete is very interesting material, its history is fascinating and the materials science behind it as well. It's one of those deceptively 'unsexy' materials too from an outsider's perspective: think of steel and someone may think of, what, swords? watches? but think of concrete and someone thinks of brutalist architecture and urban decay. But there's no reason why concrete is any less fascinating and complex than steel. What I suppose I'm saying is that it has a PR problem, and I'm glad people like yourself are leaving comments like that to help solve it :)
  - JoeAltmaier 12y ago
    Isn't the Parthenon cast in concrete? Some very beautiful buildings have been made that way.
    - Osmium 12y ago
      I believe the Pantheon dome was, not sure about the Parthenon though. But it's definitely very old. A lot older than some people realise I think. But yes, not disagreeing that it can be beautiful. I've seen many beautiful concrete sculptures, but I don't think it's the first thing that springs to mind for many.
      - JoeAltmaier 12y ago
        Ha ha, yeah, that's the one. What was I thinking.
    - deathanatos 12y ago
      The replica in Nashville, TN has concrete in its construction. The original, I believe, is made of marble. (but I'm less certain. I've never seen the real one, sadly.) [1]: https://en.wikipedia.org/wiki/Parthenon_%28Nashville%29 https://en.wikipedia.org/wiki/Parthenon_%28Nashville%29 [2]: https://en.wikipedia.org/wiki/Parthenon#Present_building https://en.wikipedia.org/wiki/Parthenon#Present_building [3]: https://en.wikipedia.org/wiki/Mount_Pentelicus https://en.wikipedia.org/wiki/Mount_Pentelicus
zupreme 12y ago
What's really going to bake your noodle is that the Romans made, over a thousand years ago, better and longer lasting concrete than we do today - and engineers still don't know why. [reference] http://www.upi.com/Science_News/2013/06/04/Ancient-Roman-concrete-better-than-todays/3571370365287/ http://www.upi.com/Science_News/2013/06/04/Ancient-Roman-con...

by bch 12y ago

thinkpad20 12y ago

The linked article makes this clear: > In case you need a refresher, cement is a powdery lime-and-clay substance that is combined with water and gravel or sand to make concrete.

jacquesm 12y ago

Anybody that does not understand the difference between cement and concrete is going to be in for a surprise when they mix up a batch of dark gray goop and try to use it for something in construction. The shrinking alone will cause some interesting effects. There are a lot of lay-man misconceptions about concrete, one of the more persistent ones is that concrete needs to 'dry'. It doesn't, it needs to cure, it's a chemical reaction that gives concrete its strength, not something going into solution to allow pouring that then dries and solidifies. Concrete is very interesting material, its history is fascinating and the materials science behind it as well. Such a simple thing in principle, so incredibly complex. Just like glass another one of those materials with vast depth.

Osmium 12y ago
> Concrete is very interesting material, its history is fascinating and the materials science behind it as well. It's one of those deceptively 'unsexy' materials too from an outsider's perspective: think of steel and someone may think of, what, swords? watches? but think of concrete and someone thinks of brutalist architecture and urban decay. But there's no reason why concrete is any less fascinating and complex than steel. What I suppose I'm saying is that it has a PR problem, and I'm glad people like yourself are leaving comments like that to help solve it :)
- JoeAltmaier 12y ago
  Isn't the Parthenon cast in concrete? Some very beautiful buildings have been made that way.
  - Osmium 12y ago
    I believe the Pantheon dome was, not sure about the Parthenon though. But it's definitely very old. A lot older than some people realise I think. But yes, not disagreeing that it can be beautiful. I've seen many beautiful concrete sculptures, but I don't think it's the first thing that springs to mind for many.
    - JoeAltmaier 12y ago
      Ha ha, yeah, that's the one. What was I thinking.
  - deathanatos 12y ago
    The replica in Nashville, TN has concrete in its construction. The original, I believe, is made of marble. (but I'm less certain. I've never seen the real one, sadly.) [1]: https://en.wikipedia.org/wiki/Parthenon_%28Nashville%29 https://en.wikipedia.org/wiki/Parthenon_%28Nashville%29 [2]: https://en.wikipedia.org/wiki/Parthenon#Present_building https://en.wikipedia.org/wiki/Parthenon#Present_building [3]: https://en.wikipedia.org/wiki/Mount_Pentelicus https://en.wikipedia.org/wiki/Mount_Pentelicus

zupreme 12y ago

What's really going to bake your noodle is that the Romans made, over a thousand years ago, better and longer lasting concrete than we do today - and engineers still don't know why. [reference] http://www.upi.com/Science_News/2013/06/04/Ancient-Roman-concrete-better-than-todays/3571370365287/ http://www.upi.com/Science_News/2013/06/04/Ancient-Roman-con...