Poor-quality concrete could lead to skyscrapers collapsing

[Rum]

There is actually a concrete testing regime in the UK. My first real job, which I had when I was about 23 was doing exactly that. We would get samples as they were delivered to the building site and do two main tests. The first was called a 'slump' test. We would fill a special cone with the stuff, turn it over and measure how much it 'slumped'. The second involved taking a sample to the lab, weighing it, microwaving the hell out of it and then weighing it again. There were a couple of other randomly administered tests too. These were all designed to ensure that the quality was right.

We were however a very weak link in the quality control chain. Nobody checked on us and I would probably have been eminently bribable given we were working on roads not skyscrapers.

Yeh, I used to do that slump test on concrete pours. If the trucks were late, or kept waiting too long, the concrete started to go off, and to make it pass the test, they would add water, to make it runny again. ( not allowed but frequently done ).

I don't know what the arrangement was for paying for a lorry load of concrete that was sent away because it was kept waiting too long, but that was the incentive. They would also have to find somewhere to dump it. Usually, some local project that just needed cheap fill.

We used to take samples back to the lab, as concrete cubes, which were kept in water tanks for about a week, and then dried and put in a crusher, and the strength when it failed was measured.

I expect that was widely fiddled too, as it would cost a fortune to fail a whole bridge, after it had been poured.

Where and when did you do this job? I did it for a year way back in 75-76 for a company called Stangers. We were working on the M5 running past Cardiff - a new road at the time.

[mistermack]

Where and when did you do this job? I did it for a year way back in 75-76 for a company called Stangers. We were working on the M5 running past Cardiff - a new road at the time.

I was working on the M5, just south of Gloucester in 1969. I was working for Sandbergs, who are still going strong.
We used to do compaction tests on soil too, virtually everything was tested.

The concrete test on site was slightly different to the current slump test. The equipment was a frame, about five feet tall, with two cones, one above the other. You put the sample in the top cone, let it slip down into the second, and then into a container. I think the container was then weighed. I can't remember the exact details, but that was the basics.
Then you filled a cube mould, and took the cubes back to the lab for soaking and crushing when cured.

We tested soil samples, compaction, all sorts. Good fun at the time. I learned to drive on their landrovers onsite. Not much health and safety. But plenty of drinking and gambling on virtually anything.

You had a good summer for it in in 76. Wasn't that the M4 at Cardiff?

[Rum]

Yes it was the M4 - my mistake. We did all those tests too as it happens. And it was a superb summer - the 'drought' of 76. It didn't rain from late April to September and by July the road workers were told to stop working for the middle two hours of the day because it was so hot, especially on the concrete bits. It absolutely sweltered.

Dodging the giant earth movers in a Landrover on rough terrain was a bit of a game with us too - as you say, little health and safety. Which reminds me that we used industrial microwave heaters to dry some samples - this was well before domestic ones were available at least commonly. You could open those things' doors with the machines still irradiating away and no doubt killing lots of important cells - and worse!

I did the job for the best part of a year while I was deciding on my future. It was a great job for a single guy - lots of overtime and a really good rate of pay. The rest of the crew I worked with were all a bit fast and loose and living for the present. There was a career of sorts to be had if I had taken exams and stuff, but it wasn't for me in the end and I ended up getting into social work .

[MiM]

Sub standard concrete foundations was the first major problem in building the new NPP (Olkiluoto 3) over here. However, those where found out and fixed, before the construction work had continued too far.

[Trinity]

I remember my gramps always taking the piss out of the term "concrete cancer" when our local 9 storey hospital was in danger of collapse back in the 80's; he said it was a cover up for cutting corners and bad concrete mixes were used. The hospital was eventually pulled down and a new two storey one built.