China used more cement in 3 years than the U.S. did in the entire 20th Century

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.

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.

uumm, yeah - I'm a concrete guy at the moment. PC = Portland Cement, 32.5 = MPa of force needed to overcome strength [1]. Normal concrete is in the 20 MPa to 50 MPa range and the strength needed is just a design parameter - it's not a quality issue. typically a slab for a house would be at the 20 MPa end and a massive industrial warehouse closer to 30 MPa (something to do with forklift wheels being small and hard), bridge spans etc ask a structural engineer. the fact that China is using a lot of grade 32.5 concrete is more likely due to the fact that they are building a lot of infrastructure that requires... 32.5 MPa strength. NB 'Grade' in the concrete industry refers to compression strength, not a quality statement. Every country has loads of standards about how cement is made, the constituents that can be added and how concrete is batched, delivered, structures designed etc. Cracks and crumbles are more likley due to inadequate design and placement of the fresh concrete. As others say, it's been around for literally 1000s of years but has infinite depth of complexity - i believe MIT found the actual formula for PC around 2010. amazing that we just used it for its bulk properties without knowing the actual chemical formula ;-)

[1] https://www.youtube.com/watch?v=_S-JnRMers8

I think China is going to suffer an epidemic of infrastructure failure in the near future, perhaps as early as the mid-2020s if the 20-30 years estimate is correct.

For comparison, South Korea's extraordinary growth was followed by a series of infrastructure failures in the mid-90s. A relatively new bridge suddenly fell into a river during the morning rush. A department store imploded, killing over 500 people. Gas explosions all over the place. IIRC none of the major accidents in Korea were caused by low-grade concrete specifically, but there seems to be a general parallel between what the Chinese have been doing lately and the "build now, worry about quality later" mentality that Koreans adopted during their period of rapid growth. Both result in crumbling buildings 20-30 years later.

I'm not an expert on this and I may be mis-remembering something I read somewhere once, but I believe the Roman formula for concrete was quite a bit different. The reasons we don't use it in modern construction are: it takes a really long time to cure, and it's made with salt water, which might cause rebar to rust.

>The Pantheon stands for a millennium, but 30-year-old concrete crumbling?

It took the wealth of a civilization to produce the Pantheon. We could make more durable buildings if we used stone, too, but do you really want to pay $10m for a house?

That was the first thing I thought when I saw this stat posted a little while ago. "Fine, the stat sounds impressive, but there's a lot of other stats that other countries do more of in the last few years than in the 20th Century".

For example, anyone could write a dramatic headline declaring that we've created more computer chips in the last X months than in the 20th century. That doesn't mean much.

In short, this feel like some sort of crappy statistic handpicked to make China look bad, when in fact it's the whole world that's using a lot more concrete, not just China!

But the stats you linked show US consumption of circa 100 million tonnes per annum. The article shows Chinese consumption at about 2100 million tonnes per annum.

So: the US did not "do the same in the last 5 years", and with China currently using cement at ~20 times the rate US is, the claim is very believable.

From the article:

> And where many houses in the U.S. are made of wood, China suffers from a relative lack of lumber. Unlike in the U.S., many people in China live in high- or low-rise buildings made out of cement.

A critical argument, but unfortunately mentioned towards the end of the article. But overall its a interesting article and this gif [0] comparing Shanghai '87 vs '13, from it gives a good perspective of the modernization (akin to images of Dubai).

[0] https://img.washingtonpost.com/blogs/wonkblog/files/2015/03/...

Not just that: China uses lots of unskilled labor that can work with concrete but not very well with steel frames. They also use more concrete per floor (we have thick walls and floors) as a form of over building since the quality isn't that great.

Singapore, a modern city by any other definition, uses concrete in the same way so they can import cheap construction labor from India.

The fundamental difference between China housing price drop and US is majority of Chinese buy properties with cash or get mortgage with very large deposit like 40%. So the risk of subprime crisis is very low.

IN 1900 US population was 1/4th what it is today (76M). The US also had access to a lot more wood per person so our homes use far less concrete. Also, US useless more asphalt vs concrete for roads so it's not exactly an apples to apples comparison.

Based on population one might expect 33 years. Would the additional factor of eleven really be expected from the fact that various developments occurred later? ISTM that the Chinese just really prefer concrete as a building material. It isn't as though all new construction in USA is concrete.

Just to add more data pointsto the discussion, here is a discussion surrounding concrete consumption due to roads.

http://reason.org/news/show/what-the-us-can-learn-from-china...

Population growth is not exponential but actually slowing. This is one of many misconceptions about demographics - an absolutely fascinating and important subject which gets little attention in the media or schools.

Here's a nice intro from Joel Cohen, a longtime leader in the field:

http://www.floatinguniversity.com/lectures-cohen

well that and their housing will be built with cement while a great amount of US housing is wood frame construction.

Still its a demonstration of unbound budgets. The future cost of maintaining it all will be the test of time. While much has been made of China's ghost towns quite a few are getting people yet I am curious as to the maintenance being done and in a timely manner. There is also the question of quality, there have been a few newsworthy stories out of China of shoddy construction.

It's frankly amazing that people are still going on about population growth. Anyone who looks at the trends - people are getting richer and moving to cities at a massive rate, and when people do that they go from having 6+ children to two or less - knows that population growth is slowing fast, and will continue to. Population growth excluding immigration is already negative across much of the western world, and will be the case everywhere before long.

In fact, the bigger issue in the western world, and eventually the whole would will be dealing with it, is what happens when this slowdown in births happens. Just as when you got a huge economic boom from having many young people, you get a economic drag when all those people age and have less young people to support them.

This always reminds me of people snickering about how much snow is in their backyard whenever the topic of climate change comes up.

If you subtract the 15% unoccupied rate from your link from the 6.6 gigatons of concrete, it's still a lot more than the U.S. used in 100 years.

They are being filled up.

https://www.bullionstar.com/blogs/koos-jansen/guest-post-5-c...

I wonder if sooner rather than later, those ghost cities might actually fill up once they bottom out and become affordable like how bad parts of SF or Oakland or NYC used to be cheap?

According to [1], it (cement) has been around ~70 megatonnes in each of those years, while the same site agrees with the article and puts China at around ~2 gigatonnes for each of those years.

Usage in the U.S. took a nosedive in 2008, I assume because of the recession. Pre-2008 shows a local maximum in 2005 of 128 megatonnes; so still an order of magnitude less.

[1] http://www.statista.com/statistics/273367/consumption-of-cem...

cement and concrete are different materials

Not really. It's more like observing the number of shipping containers going in and out of a country and deriving some rough figures on the economy from there (or trends).

Lines of code have to be examined in detail to figure out their impact, concrete is the universal component of construction, if more concrete is used there will be more construction going on.

Pound-for-pound, cement is the largest producer of carbon emissions in the world.

It gives a glimpse on the rate of change around us, and out there in the world. This big picture is fascinating to behold at, for many people.

Fearmongering

You obviously have never gone out and looked at concrete. How can you not be amazed.

That and it's common usage would probably make it a great linkbait story...

Your imagination is wrong, sadly. The cement industry accounts for nearly 5% of global CO2 emissions, about half of which comes from the chemical decomposition of calcium carbonate (which is how you make cement).