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Birmingham History of Reinforced Autoclaved Aerated Concrete (RAAC) and other concrete problems

Morturn said:
The Queensway Tunnel was built in the later sixties. I cannot recall when problems with high alumina cement came to light, I seem to recall it was at a swimming’s pools roof beams, possibly at a school. The cause, and remedy was quickly identified, and programme of testing initiated.

I cannot remember the science behind this cause of failure, it will be out there on the internet for anyone interested, but basically high alumina cement converts to a less stable condition in some circumstances. What this effectively meant was high alumina cement ducked under the radar of normal testing procedures. Also, most high alumina cement products were precast, not bulk or mass concrete.

Certainly, some of the works I have been involved in required onsite concrete testing and samples to be taken at the time of delivery and placement and sent to the lab.

Just as a matter of interest, if you like this sort of thing; high alumina cement has a rapid curing time, a few days as opposed to 28 with normal concrete. So, you can imagine the manufacturers of precast beams did not have to store onsite 28 days’ worth pf production before it could be moved.
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What we found (maybe things have changed) that rapid curing of the mix does not allow for maximum strength. For large presses for example the concrete was actually a floating slab isolated from the main area or floor. We allowed the isolated slab to cure naturally to obtain maximum strength. Concrete/ cement has been around for a long time and it seems that folks are always trying to speed things up. I am not an expert by any means but like my old manager would say, “take the time to do it right the first time because you will the second, third and on & on”
 
Richard Dye said:
What we found (maybe things have changed) that rapid curing of the mix does not allow for maximum strength. For large presses for example the concrete was actually a floating slab isolated from the main area or floor. We allowed the isolated slab to cure naturally to obtain maximum strength. Concrete/ cement has been around for a long time and it seems that folks are always trying to speed things up. I am not an expert by any means but like my old manager would say, “take the time to do it right the first time because you will the second, third and on & on”
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I can go with that too. We would send test cubes off at 7, 14 and 21 days after curing underwater. By 28 days concrete has acquired about 95% of its strength then continues to improve slowly over a period of years.

My recollections are that it’s the stuff that’s been altered to make t cure quicker that seems to be problematic.
 
Morturn said:
I can go with that too. We would send test cubes off at 7, 14 and 21 days after curing underwater. By 28 days concrete has acquired about 95% of its strength then continues to improve slowly over a period of years.

My recollections are that it’s the stuff that’s been altered to make t cure quicker that seems to be problematic.
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That is exactly what it seems like to me!
 
Morturn said:
Its not new ether, the Boswell built in the 1920’s houses were basically concrete and suffered from poor design. Then we had the Wimpy No Fines built to replaces the terrace housing in Aston, New Town and Lozells.
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We had a big situation in the early 60’s in Boston. A contractor used sub par concrete on a massive inner city sidewalk (pavement) project. After a couple of years the sidewalks started to granulize and wash away. That got a lot of attention because the contractor was related to the mayor or something like that. It seemed like after that it really got peoples attention. Not perfect by any means but it gave a lot of visibility to such things.
 
Richard Dye said:
We had a big situation in the early 60’s in Boston. A contractor used sub par concrete on a massive inner city sidewalk (pavement) project. After a couple of years the sidewalks started to granulize and wash away. That got a lot of attention because the contractor was related to the mayor or something like that. It seemed like after that it really got peoples attention. Not perfect by any means but it gave a lot of visibility to such things.
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Not Birmingham but we had something similar in the UK in the early eights with Junior Books Ltd v Veitchi. Sub standard concrete work in a floor. It bought about a lot of legal controversy.
 
It appears that Aston Manor Academy has RAAC and was one of the 13 schools whose budgets were scrapped in 2010.

IMG_3066.jpeg
 
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Pedrocut said:
www.bbc.co.uk

Solihull's Core Theatre shuts after dangerous concrete found

The concrete is prone to collapse and is affecting more than 150 schools across England.
www.bbc.co.uk
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Looking at these it seems like people took a good think too far. Funny how that happens.
A similar thing occurred some years ago with polyurethane foam. PU is a great material but can be pricey. Foaming not unlike the concrete is a good way to to reduce density and cost. Except there is a limit. We we and other US companies were competing with Asian companies who were using PU foam at high levels, only as in the concrete their physical performance was not acceptable. It took the market a long time to recover.
 
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