[leguminous]

Aerated concrete is an established building material in some parts of the world. In Europe, a big manufacturer is Ytong, and they even make precast panels in addition to blocks.

It's made differently from this, though. It is aerated through a chemical reaction rather than mechanically.

[cornholio]

The industrial version is produced in an autoclave, this allows precise control of curing, density and final mechanical resistance/insulation values. Hence, the name the material is best known by - AAC.

On the other hand, the video linked attributes too much credit and complexity to the foam manufacturing method, it can certainly be done with very primitive technology. Here are some dudes doing it in a developing country, it's very very basic, the foam generator is basically a steel wool sponge where pressurized air combine with water containing the foaming agent. They give out the complete recipe and details of their tools:

https://www.youtube.com/watch?v=-h6zBbVkuQI

[stoneman24]

There was recently a crisis in older publicly constructed buildings in the UK that were built [0].The aerated concrete had a limited lifespan especially if it was damaged and had contact with water.

Lots of people looking for compensation and claiming mis-representation.

[0] https://www.bbc.co.uk/news/education-66669239

[cornholio]

The UK crisis involved steel reinforced AAC beams that were used (of all places) to support roofs of schools. UK turned out to be a rainy place, the rain infused into the cellular structure and corroded the steel, with disastrous consequences.

It's a very particular use case of a very particular product, not relevant to the wide majority of AAC uses around the world, which is largely non-structural and not reinforced, or subjected to moderate compressive loads, such as lateral walls for 1-2 stories buildings in non-seismic areas.

[gerdesj]

The risks were understood (by engineers) and this usage was given a "shelf life". Unfortunately, those risks were put into the "Oh we'll forget about it" or "We'll wait until it looks a bit shifty" categories.

However as any fule (engineer) kno, reinforced and especially pre-stressed conc members will fail in quite a dramatic fashion. Unless you notice rust dribbling out then you can end up with anything from the roof failing to the roof exploding. I don't think anyone was daft enough to pre-stress these things.

I don't know how much money was saved but it was a really stupid application and basically ended up punting far greater costs due to remediation down the road.

[cornholio]

> and this usage was given a "shelf life"

While it might technically be true, that surely does not absolve the engineers who did this crap.

There is a general social expectation that new buildings should be structurally sound for a duration on the order of a century. So, if you deliver something that has a mean time before catastrophic failure around 30 years, you also need to account and set up the institutions that will handle the failure, the same way nuclear companies are required to set aside money for their decommissioning. You need to have periodic inspections for signs of early failure etc. and this whole circus needs to be disclosed and priced into your tender.

In reality, this entire fiasco was a dirty and cheapest way to satisfy the contract, ye old "good enough for government work" as evidenced by the fact no substantial number of private buildings of the same period are having this problem.

The maintenance provision was snuck into - or bribed into - some mountain of legalese, but the fuckers knew exactly that they were putting children in harm's way.

[earleybird]

Is that you Molesworth???

[gerdesj]

Carry on, old boy.

[rayiner]

Using porous concrete reinforced with steel in a rainy place is a real WTF decision. It’s a miracle they didn’t collapse earlier.