3 ms·

> Concrete alone is incredibly long-lived and durable It can be, but usually isn't. People don't make concrete buildings to last 100 years. Normally, chloride

> Concrete alone is incredibly long-lived and durable It can be, but usually isn't. People don't make concrete buildings to last 100 years. Normally, chlorides, and carbonation set the expiration date on a building. In China, 20 year old, if not 10 year old highrises are knocked down. Before I saw that myself, I thought that it's madness.

RosanaAnaDana 5y ago
Building with concrete to knock down in 10-20 years is actual madness.
- magicsmoke 5y ago
  There's a kind of twisted logic to it. If your construction techniques are constantly improving and the high volume of construction incentivizes you to develop more cost efficient construction technologies, then planned obsolescence of buildings is like planned obsolescence of phones. Build soviet block apartments, knock down in 20 years, replace with prefab building compartments with wiring and plumbing built in at the factory. Then export the prefab technology worldwide to take advantage of the infrastructure boom in other developing countries. Isn't build fast, break fast, and learn fast the whole silicon valley ethos?
- brandmeyer 5y ago
  On the other hand, building with an eye to increase density in a couple of decades looks like smart planning for growth.
  - baybal2 5y ago
    Not so. Most of "knockdown 10 year old building, and rebuild" are done for very expensive, luxury developments with much lower density. Think of 2-4 mansion apartments per floor. Nothing else would've made economic sense. In comparison, the densest tower I seen in China had whooping 24 apartments per floor.
hguant 5y ago
Part of that is because they have to other wise the building would collapse on its own. A big issue people don't talk about is that a lot of the concrete China makes is subpar and not up to spec by US or EU standards - they don't use the right (aka more expensive) grade of sand, so the concrete doesn't bind as strongly as it should. The sand used to make concrete has to have rough edges, something about the surface area, which ironically means that desert sands aren't very useful - they've been rounded by wind erosion and rubbing against other sand grains.
- pueblito 5y ago
  It’s not surface area so much as the faceted sides of crushed sand lock together when compressed instead of sliding past each other
- jhgb 5y ago
  What I was wondering some time ago...couldn't you sieve desert sand for larger grains and then crush them?
ornornor 5y ago
> In China, 20 year old, if not 10 year old highrises are knocked down. Isn’t it part of their 12% year on year growth strategy? Whatever it takes to make these numbers happen? Which is also why China builds cities designed for millions of people that remain ghost towns once they’re done: they’re not really built to be lived in but to boost the economy activity via construction costs.
- baybal2 5y ago
  To some part, it must be. I don't believe that even in communists China there must be somebody who don't realise how bonkers it is. But economic gain is there too. The surreal real estate bubble makes knocking down even 10 year old buildings profitable.

RosanaAnaDana 5y ago

Building with concrete to knock down in 10-20 years is actual madness.

magicsmoke 5y ago
There's a kind of twisted logic to it. If your construction techniques are constantly improving and the high volume of construction incentivizes you to develop more cost efficient construction technologies, then planned obsolescence of buildings is like planned obsolescence of phones. Build soviet block apartments, knock down in 20 years, replace with prefab building compartments with wiring and plumbing built in at the factory. Then export the prefab technology worldwide to take advantage of the infrastructure boom in other developing countries. Isn't build fast, break fast, and learn fast the whole silicon valley ethos?
brandmeyer 5y ago
On the other hand, building with an eye to increase density in a couple of decades looks like smart planning for growth.
- baybal2 5y ago
  Not so. Most of "knockdown 10 year old building, and rebuild" are done for very expensive, luxury developments with much lower density. Think of 2-4 mansion apartments per floor. Nothing else would've made economic sense. In comparison, the densest tower I seen in China had whooping 24 apartments per floor.

hguant 5y ago

Part of that is because they have to other wise the building would collapse on its own. A big issue people don't talk about is that a lot of the concrete China makes is subpar and not up to spec by US or EU standards - they don't use the right (aka more expensive) grade of sand, so the concrete doesn't bind as strongly as it should. The sand used to make concrete has to have rough edges, something about the surface area, which ironically means that desert sands aren't very useful - they've been rounded by wind erosion and rubbing against other sand grains.

pueblito 5y ago
It’s not surface area so much as the faceted sides of crushed sand lock together when compressed instead of sliding past each other
jhgb 5y ago
What I was wondering some time ago...couldn't you sieve desert sand for larger grains and then crush them?

ornornor 5y ago

> In China, 20 year old, if not 10 year old highrises are knocked down. Isn’t it part of their 12% year on year growth strategy? Whatever it takes to make these numbers happen? Which is also why China builds cities designed for millions of people that remain ghost towns once they’re done: they’re not really built to be lived in but to boost the economy activity via construction costs.

baybal2 5y ago
To some part, it must be. I don't believe that even in communists China there must be somebody who don't realise how bonkers it is. But economic gain is there too. The surreal real estate bubble makes knocking down even 10 year old buildings profitable.