China cement usage- is this stat true?

[Zak33]

According to Bill Gates....China has used more cement in three years....than the US used in the entire 20th century!!

http://www.gatesnotes.com/About-Bill...crete-in-China

Is that legit??

[Andy3536]

They also say "concrete deteriorates. In the coming decades, the United States and China alone will need to spend trillions of dollars replacing and disposing of concrete laid down in the past generation"

Now, knowing there are Roman structures made of concrete, a quick google shows this.

"Used in the majority of buildings, bridges, tunnels and dams for its strength

Gains strength over time

Not weakened by moisture, mould or pests

Concrete structures can withstand natural disasters such as earthquakes and hurricanes

Roman buildings over 1,500 years old such as the Coliseum are living examples of the strength and durability of concrete"

From here.
http://www.wbcsdcement.org/index.php...es-of-concrete

I'd say it's codswallop...

[jim]

It does sound pretty staggering. However, the pace of city-building in China has been incredible of late, and it's not really something that the US ever did.

Also, apparently the Three Gorges Dam used 10 times the amount of concrete that the Hoover Dam did - approximately 65 million tonnes for the Three Gorges.

[Saracen]

Probably.

China has certainly been on a construction program of truly enormous proportion, from roads to entire cities. Bear in mind the base point they started from, compared to tbe US.

I've no real idea if that stat is true or not, but it wouldn't surprise me, let alone shock me, if it were.

[jim]

They also say "concrete deteriorates. In the coming decades, the United States and China alone will need to spend trillions of dollars replacing and disposing of concrete laid down in the past generation"

Now, knowing there are Roman structures made of concrete, a quick google shows this.

"Used in the majority of buildings, bridges, tunnels and dams for its strength

Gains strength over time

Not weakened by moisture, mould or pests

Concrete structures can withstand natural disasters such as earthquakes and hurricanes

Roman buildings over 1,500 years old such as the Coliseum are living examples of the strength and durability of concrete"

From here.
http://www.wbcsdcement.org/index.php...es-of-concrete

I'd say it's codswallop...

I wouldn't say it's codswallop. Even if the structures survive, they'll still be knocked down for regeneration etc. We're not particularly fond of building things and leaving them there for centuries.

[Andy3536]

Even if the structures survive, they'll still be knocked down for regeneration etc. We're not particularly fond of building things and leaving them there for centuries.

What you say is entirly true, however. The article says all the concrete will have to be replaced and disposed of because "concrete deteriorates"
That's what makes the article cosdswallop.

[Flibb]

Look up concrete cancer, millions are being spent replacing bad concrete in the UK. Mainly down to bad reinforcing. Locally there have been issues with motorway bridges that are having to be tested, so far from codswollop.

[Saracen]

....

From here.
http://www.wbcsdcement.org/index.php...es-of-concrete

I'd say it's codswallop...

You do realise that that is PR blub put out by concrete producers, don't you?

Is your position that concrete doesn't deteriorate? If so, that's codswallop. It does, and due to a range of causes, from incorrect mix, incorrect aggregages, incorrect structural design and loadings, chemicals effects, environmental effects, and all sorts.

Whoever built those 1500 year old Roman structures obviously wasn't the same bunch of incompentent nincompoops that built the concrete driveway at my old house, because that was crumbling and breaking up within about 5 years.

Concrete, done right, is pretty resilient. Done wrong, it's very poor. And there's a vast array of stages in-between. I wonder what the construction standards and concrete production quality conttol and use are of a vast array of Chinese state workers?

[Ferral]

I was watching one of the Construction programs on Quest (Extreme Engineering I believe it is). China are really specific with regards to color of cement when stuff is built in sections onsite, as an example one of the episodes was covering a rather large bridge they were building. Each section of cement that was being used building the stantions had to be perfectly matched to the previous pour in color. If was so much as a shade off then it was removed and had to be redone, this could well partly explain amout used.

[DDY]

I was watching one of the Construction programs on Quest (Extreme Engineering I believe it is). China are really specific with regards to color of cement when stuff is built in sections onsite, as an example one of the episodes was covering a rather large bridge they were building. Each section of cement that was being used building the stantions had to be perfectly matched to the previous pour in color. If was so much as a shade off then it was removed and had to be redone, this could well partly explain amout used.

I'd make a guess that the proportion of rejected material is negligible when compared to all of the cement used in China. I doubt a villager who's saved up just enough to build their first concrete house is going to care that their walls are a bit greyer than the floor.

In bigger projects, it's not just China that rejects materials on appearance, the entire world does it too, but even then the proportion is tiny.

[TheAnimus]

Ok so first off concrete itself is great, the problem is that you can't always make solid blocks of it.

Ever had the opportunity to get up close or under a disused cooling tower from a power station? Those big conical shapes that have steam rising up the top, and water dropping down the side? These things last decades without any issue. They are slipformed, a continuous process of pouring concrete, there is no 'seam' no 'gap'.

But to achieve that the structure has to be supported by something that absorbs any shock, allows it to sway. That pattern at the base of the cooling tower lets it do just that.

Now you can't make many structures like that. Houses that are rectangles need to allow bits to move without interfering with each other. Some shapes are almost impossible to slipform so have to be attached. This means gaps, these water can invade. The weather gets cold, the water starts to expand as it freezes, gaps get bigger, repeat. Bits of the concrete can start to break loose. The structure moves say with the wind or ground changes beneath it. Water gets in, it freezes, years pass, the structure needs work.

This is why it has to be replaced, the more ambitious the project, the more pre-fab blocks the more strength required, the more issues.

However, take a look at how long the hoover dam will likely last, some say 10,000 years. The concrete inside it is in some places still curing.

[Bluecube]

They also say "concrete deteriorates. In the coming decades, the United States and China alone will need to spend trillions of dollars replacing and disposing of concrete laid down in the past generation"

Now, knowing there are Roman structures made of concrete, a quick google shows this.

"Used in the majority of buildings, bridges, tunnels and dams for its strength

Gains strength over time

Not weakened by moisture, mould or pests

Concrete structures can withstand natural disasters such as earthquakes and hurricanes

Roman buildings over 1,500 years old such as the Coliseum are living examples of the strength and durability of concrete"

From here.
http://www.wbcsdcement.org/index.php...es-of-concrete

I'd say it's codswallop...

Different cement. The exact composition of the cement the Romans used is apparently a bit of a mystery but it's superior to modern mixtures.

[jas88]

Considering a lot of US buildings are non-concrete - timber-frame or brick houses, steel-frame buildings - it may not be such a large amount there as you might expect: a few massive structures like Three Gorges will go a very long way. A thousand tonne bridge is tiny compared to that monster dam alone - 65,000 times the size.

It'll be interesting to see how well the rushed concrete installations of the last few overheated years of frantic activity in China hold up to time, too - how much of it will need premature replacement?

[TheAnimus]

Different cement. The exact composition of the cement the Romans used is apparently a bit of a mystery but it's superior to modern mixtures.

That's one of those fun myths, up there with the whole the Russians took a pencil thing.

https://simplesupports.wordpress.com...oman-concrete/

It's more complex!

[HalloweenJack]

Ok so first off concrete itself is great, the problem is that you can't always make solid blocks of it.

Ever had the opportunity to get up close or under a disused cooling tower from a power station? Those big conical shapes that have steam rising up the top, and water dropping down the side? These things last decades without any issue. They are slipformed, a continuous process of pouring concrete, there is no 'seam' no 'gap'.

But to achieve that the structure has to be supported by something that absorbs any shock, allows it to sway. That pattern at the base of the cooling tower lets it do just that.

Now you can't make many structures like that. Houses that are rectangles need to allow bits to move without interfering with each other. Some shapes are almost impossible to slipform so have to be attached. This means gaps, these water can invade. The weather gets cold, the water starts to expand as it freezes, gaps get bigger, repeat. Bits of the concrete can start to break loose. The structure moves say with the wind or ground changes beneath it. Water gets in, it freezes, years pass, the structure needs work.

This is why it has to be replaced, the more ambitious the project, the more pre-fab blocks the more strength required, the more issues.

However, take a look at how long the hoover dam will likely last, some say 10,000 years. The concrete inside it is in some places still curing.

sadly that's a misconception about the hoover damn - if it had been a single continuous pour then it would take 125 years to cool off. but it was nt , they built it in blocks - and the concrete curing was aided by not only ice cold water being sprayed over it - but a series of 1 inch pipes running through it to cool it.


curing was complete in 1935

https://www.usbr.gov/lc/hooverdam/hi.../concrete.html

[TheAnimus]

It's a misconception the official tour guides themselves put around in my defence! I guess it depends what you mean by curing, as the cooling tapers off (material scientists please don't hate me if it's geometric) exponentially I believe. The link you reference refers to the cooling operation they had pipes installed just to help dissipate heat, with a huge refrigerating plant built there, as the link mentions 1000 tons in 24 hours, that's crudely speaking 3.5MW (if my mental arithmetic is right, which it normally isn't when crossing units!). That's nuts!

http://www.quora.com/Is-it-true-that...-or-more-years

Someone there suggests that yes it is technically still hydrating. There is a lot of fun engineering and chemistry that goes into these things, it makes it very hard to accurately generalise. But the cooling assistance stopped, not the chemical process in the concrete.