Interested in concrete? Peterhead Harbour.

I'm your man.

Water to cement ratio is critical into strength and compactability of concrete. Too little water and you can't compact it and get the air bubbles out, losing strength. Too much water and you just lose strength.

How do you measure this independently on site?. Well, that is the slump test. A truncated cone 300mm high, 200mm diameter base, 100 mm diameter at the top. Fill it with concrete sample in three layers with a bit or rodding. Float off the top, slowly lift the cone off the concrete and the concrete slumps down, the wetter the concrete the more it slumps. Invert the cone and use the rod to measure down to the top of the heap of concrete. You couldn't get any more low tech. (well apart from Kelly's ball which involves a steel ball and a rod dropped into a bucket of concrete, you measure how deep it sinks. If it sinks to the bottom your concrete is probably far too wet.)

Anyway back to the photos. He rejected the concrete as being far too dry. I explained it was thixotropic (it was being dropped through water so this was a technique that slowed the dispersal of the cement - it effectively put the 'slump' into slow motion, wait two minutes and it'll get there). Try explaining concrete technology to a man in a flat cap! Anyway the argument was abandoned, one of the divers placing the concrete had snagged his weight belt on scaffold and it unhooked. Without all that lead he rocketed to the surface through all the steelwork and had to be rescued injured.

If you got this far well done.

I am available to do power point presentations on materials technology.

You only have to ask.