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

Back in 1974 several school roofs are reported to have collapsed and schools closed due to fear that high alumina cement beams were faulty.
The Environment Department called for inquiry by councils, and Tubes Investments devise a method of solving the problem ?


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mw0njm. said:
1n the 50/60s there was a outside company down aston church rd by the cut bridge that made thermalite blocks from the old power station waste
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Thermalite had a production plant at Hams Hall Power Station. They used the fly ash from the power station boilers in the production process. When I worked, thermalite would deliver the blocks still steaming hot from the factory.
 
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Morturn said:
Thermalite had a production plant at Hams Hall Power Station. They used the fly ash from the power station boilers in the production process. When I worked, thermalite would deliver the blocks still steaming hot from the factory.
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i liked working with them becouse they was easy to cut and lift:grinning:
 
It's easy to be confused by the different construction methods. My understanding of the problem is that it is the reinforced concrete supporting beams which are failing. Thermalite is used as non supporting blocks or slabs and has no reinforcing steel content?
 
Tinpot said:
It's easy to be confused by the different construction methods. My understanding of the problem is that it is the reinforced concrete supporting beams which are failing. Thermalite is used as non supporting blocks or slabs and has no reinforcing steel content?
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In the link above that Pete supplied, I thought they had rebar in the roof panels. The blocks absorbed water causing the rebar to rust sag and collapse. At least that what I thought.
 
Tinpot said:
It's easy to be confused by the different construction methods. My understanding of the problem is that it is the reinforced concrete supporting beams which are failing. Thermalite is used as non supporting blocks or slabs and has no reinforcing steel content?
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There may be a confusion between the product Thermalite and the company Thermalite Ytong Ltd. They advertise the manufacture of aerated products on two production lines, one producing building blocks and the other reinforced building slabs.

As there are other historical problems with concrete that have affected Birmingham buildings I think I will alter the title to include.
 
Due to a roof collapse at Camden Girls School in August 1973, and 9 months later a pre-cast concrete beam from roof of Sir John Cass school in Stepney The Department for the Environment ordered safety checks in 1974, the problem being quick setting cement with high alumina cement.
 
We built a home right on the ocean. For the siding we used Hardy plank or Hardy board to look like clap board (we had strict building codes). This was actually low-density concrete that was inert to the saltwater environment. It was a little pricy but supposedly easy to install. The caveat was you needed the right blade for your saw or everything splintered or cracked & you needed the right nails and drill or you had another mess. The good news is that after 15 years it still looks like new but you had to get it right! Sorry off topic a little!
 
In the safety checks of 1974 the Birmingham Post reports 16 blocks of council flats potentially affected (would not name buildings involved)…17 schools have been either partially or wholly closed due to danger.
 
I recall that the Queensway Tunnel had a number of roof beam made from high alumina cement. Its not a bad product if made strictly to specification. The problems arose when used in certain environmental conditions like swimming pools that used chlorine or if very strict ratios of water, cement and aggregate were not adhered too. There used to be a lot of guess work when high alumina cement was first used.
 
Morturn said:
I recall that the Queensway Tunnel had a number of roof beam made from high alumina cement. Its not a bad product if made strictly to specification. The problems arose when used in certain environmental conditions like swimming pools that used chlorine or if very strict ratios of water, cement and aggregate were not adhered too. There used to be a lot of guess work when high alumina cement was first used.
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Interesting.......I have not been involved in structural concrete; however, I have been involved with very high load flooring to support 3,000-ton presses and steel storage. Every truck load was certified material from the mixer, going back to 1976 through 2009 and we never had any issues. Currently I am involved with a project in Louisiana requiring a high pressure mix in a 25,000 sq ft building, all loads will be tested and certified.
I am very surprised that the Queensway Tunnel material was not certified or possibly the specifications were not substantial.
 
Richard Dye said:
Interesting.......I have not been involved in structural concrete; however, I have been involved with very high load flooring to support 3,000-ton presses and steel storage. Every truck load was certified material from the mixer, going back to 1976 through 2009 and we never had any issues. Currently I am involved with a project in Louisiana requiring a high pressure mix in a 25,000 sq ft building, all loads will be tested and certified.
I am very surprised that the Queensway Tunnel material was not certified or possibly the specifications were not substantial.
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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.
 
In 1974, nine months after the Camden school roof collapse, there was the collapse at Sir John Cass in Stephen..,,

Two beams forming part of the roof over the swimming pool at the school collapsed. The investigation showed that the cause of the failure was loss of strength due to conversion of high alumina cement concrete followed by sulphate attack leading to disruption of the concrete.
 
Pedrocut said:
In 1974, nine months after the Camden school roof collapse, there was the collapse at Sir John Cass in Stephen..,,

Two beams forming part of the roof over the swimming pool at the school collapsed. The investigation showed that the cause of the failure was loss of strength due to conversion of high alumina cement concrete followed by sulphate attack leading to disruption of the concrete.
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Thanks, that it.
 
Pedrocut said:
Evening Mail, June 1983…falling blocks Chelmsley Wood…

View attachment 183884
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This if I recall correctly is more of a problem with the design of large panel block construction than the concrete. The Ronan Point disaster sometime late 60’s was initially caused by a gas explosion, but soon proved to be poor design and construction.

Birmingham had a lot of these large panel blocks. Still has a few. The council had to undertake a lot of work. Firstly, all gas was removed and dwelling with gas cookers were compensated. I recall it was about £70 per cooker. There was then a programme of reinforcement where the panels were strapped and bolted together. All the work was done internally with large steel anchors and straps inserted through the floors. The blocks at Fossway Drive had a delayed opening due to this, others were done in occupation.

There was also the problem with damp ingress. Again, the council had to replace the filler in all of the joints. All done externally with men in cradles. There were then further problems with the mosaic tiling falling off. Yet again, more work to fix steel mesh over the mosaic.

The big concrete problem in my opinion is of course spaghetti junction and midland elevated motorways.
 
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