Off Topic And Now for Something Completely Different

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DMD said:
I have no idea if this is the correct answer, but it's just popped up on a news feed.

RAAC is a lightweight, precast, cellular concrete building material made from quartz sand, calcined gypsum, lime, portland cement, water and aluminum powder.

It started being used predominantly in public sector roof construction in the UK and parts of Europe in the 50s and continued to be used until the 90s, but the material has been found to have structural issues that means it begins to deteriorate after 40 or 50 years. That means much of the RAAC that remains in British buildings is now at risk of causing a collapse.

Professor Chris Goodier, an expert in construction engineering and materials who led a major national research project on RAAC for the University of Loughborough, explains: “Like many countries, the UK has an old building stock, which needs to be adequately repaired and maintained.

In the post-war period the country built numerous new buildings with a variety of different methods, many of which are now feeling their age.

“One innovative construction material and process was RAAC, which is an aerated lightweight cementitious material with no coarse aggregate; the material properties and structural behaviour therefore differs significantly from ‘traditional’ reinforced concrete.

“Tens of thousands of these structural panels exist across a broad cross-section of buildings, many constructed in the 60s and 70s, and many are showing signs of wear and tear and deterioration. The vast majority form the roof of the structure, usually flat, and hence are difficult to access, survey, maintain and replace.”

A report published in May 2019 highlighted the significant risk of failure of these planks and in September last year the Government sent a notice to relevant property owners stating that “RAAC is now life-expired and liable to collapse”.

Professor Goodier said it is RAAC “from the 50s, 60s and 70s that is of main concern, especially if it has not been adequately maintained”.

“RAAC examples have been found with bearings (supports) which aren’t big enough, and RAAC with the steel reinforcement in the wrong place, both of which can have structural implications. Prolonged water ingress (not uncommon on old flat roofs) can also lead to deterioration,” he said.

However, not all RAAC is dangerous by nature. It is s still manufactured and installed all over the world and can be an appropriate construction material if properly designed, manufactured, installed, and maintained.

What is RAAC? Why aerated concrete school buildings must close in England and the safety fears explained (msn.com)
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A bit odd that it appears now and only in schools then.
 
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balkan tiger said:
Anyone in the building trade know what's the score with this dodgy concrete?
Did they only use it to build schools? Why are no buildings in other uses getting closed? Is there a time when this concrete started to be used and has it stopped being used.
It's all very strange.
And of course you can't rely on the media to ask the right questions.
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Just natural aging
I’d wonder what the government are trying to hide while this is in the headlines
 
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balkan tiger said:
A bit odd that it appears now and only in schools then.
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It's not just schools, there's at least 34 public buildings and 24 hospitals as well (NHS Scotland are checking their buildings, there's a chance that the material was used in up to 250 sites).

As far as I can see, only one school roof has ever collapsed as a result of this material and that was five years ago, so I'm not sure what's prompted such drastic last minute action.
 
DMD said:
I have no idea if this is the correct answer, but it's just popped up on a news feed.

RAAC is a lightweight, precast, cellular concrete building material made from quartz sand, calcined gypsum, lime, portland cement, water and aluminum powder.

It started being used predominantly in public sector roof construction in the UK and parts of Europe in the 50s and continued to be used until the 90s, but the material has been found to have structural issues that means it begins to deteriorate after 40 or 50 years. That means much of the RAAC that remains in British buildings is now at risk of causing a collapse.

Professor Chris Goodier, an expert in construction engineering and materials who led a major national research project on RAAC for the University of Loughborough, explains: “Like many countries, the UK has an old building stock, which needs to be adequately repaired and maintained.

In the post-war period the country built numerous new buildings with a variety of different methods, many of which are now feeling their age.

“One innovative construction material and process was RAAC, which is an aerated lightweight cementitious material with no coarse aggregate; the material properties and structural behaviour therefore differs significantly from ‘traditional’ reinforced concrete.

“Tens of thousands of these structural panels exist across a broad cross-section of buildings, many constructed in the 60s and 70s, and many are showing signs of wear and tear and deterioration. The vast majority form the roof of the structure, usually flat, and hence are difficult to access, survey, maintain and replace.”

A report published in May 2019 highlighted the significant risk of failure of these planks and in September last year the Government sent a notice to relevant property owners stating that “RAAC is now life-expired and liable to collapse”.

Professor Goodier said it is RAAC “from the 50s, 60s and 70s that is of main concern, especially if it has not been adequately maintained”.

“RAAC examples have been found with bearings (supports) which aren’t big enough, and RAAC with the steel reinforcement in the wrong place, both of which can have structural implications. Prolonged water ingress (not uncommon on old flat roofs) can also lead to deterioration,” he said.

However, not all RAAC is dangerous by nature. It is s still manufactured and installed all over the world and can be an appropriate construction material if properly designed, manufactured, installed, and maintained.

What is RAAC? Why aerated concrete school buildings must close in England and the safety fears explained (msn.com)
Click to expand...

Should have looked up the concrete the Romans used.
 
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DMD said:
Or the pyramid builders. <cheers>
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They didn’t use concrete. They did use mortar.Would be useful to have then build large structures though. The Romans invented a concrete that set underwater. Details were lost and they didn’t rediscover how to do it until last century. Watched them demonstrating it in a documentary a while ago.
The Romans constructed Hadrian’s wall at the rate of a mile a month. The should be in charge of road repairs.
 
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Cityzen said:
They didn’t use concrete. They did use mortar.Would be useful to have then build large structures though. The Romans invented a concrete that set underwater. Details were lost and they didn’t rediscover how to do it until last century. Watched them demonstrating it in a documentary a while ago.
The Romans constructed Hadrian’s wall at the rate of a mile a month. The should be in charge of road repairs.
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Ye but what have they ever done for us??
 
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originallambrettaman said:
It's not just schools, there's at least 34 public buildings and 24 hospitals as well (NHS Scotland are checking their buildings, there's a chance that the material was used in up to 250 sites).

As far as I can see, only one school roof has ever collapsed as a result of this material and that was five years ago, so I'm not sure what's prompted such drastic last minute action.
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Maybe so that another roof doesn't collapse on kids? Not ITK, just a wild guess
 
originallambrettaman said:
Clearly, but you've rather missed my point, why wait five years to do anything about it?
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Ineptly handled once again by the powers that be.

Nowt’s crashing on kid’s heads today, tomorrow or next week. A maintenance and/or replace program initiated five years ago would have sorted this whole problem by now. Could have run it through lockdown when schools were closed anyway.

Now we’ve got unnecessary and irrational panic and mass inconvenience for children, parents, school managers and teachers which should all have been avoided.

Incompetence at the top level doesn’t even come close to covering it.
 
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Ernie Shackleton said:
Ineptly handled once again by the powers that be.

Nowt’s crashing on kid’s heads today, tomorrow or next week. A maintenance and/or replace program initiated five years ago would have sorted this whole problem by now. Could have run it through lockdown when schools were closed anyway.

Now we’ve got unnecessary and irrational panic and mass inconvenience for children, parents, school managers and teachers which should all have been avoided.

Incompetence at the top level doesn’t even come close to covering it.
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Somewhere in the news it was mentioned that a school roof collapsed last week...
 
Chesh1recat said:
Sadly, yes, this one https://www.google.com/url?sa=t&sou...EQFnoECBoQAQ&usg=AOvVaw3oMvV1CfJD--l4A0YqRptL
Don't know if it's the case here but I recall stories of corruption in awarding contracts and subsequently using inferior materials leading to building failure - former Eastern Bloc countries eg Romania come to mind.
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That’s awful but there’s no suggestion that this was caused by failure of the type of construction currently under discussion in this country.
 
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