As part of the never ending struggle to get the right solution for this bloody slab I am now pricing and sizing concrete mixers. [Although I am still actively considering ready mixed - especially given the current weather forecast for the next week.]
Both HSS and Jewson seem to do similar mixers - a 'lightweight' 90 litre/.09 cubic metre electric or petrol mixer or a 'heavy duty' 110 litre/0.11 cubic metre diesel.
Firstly, there doesn't seem to be much difference in the volumes. Presumably the 'heavy duty' mixer just mixes a lot quicker.
Secondly, if the label on my barrow is correct then it holds 3 cubic feet which is 0.085 cubic metres or 85 litres. This seems remarkably similar to the volume of the mixers.
Given that I will probably not fill the barrow to the brim if the mix is fairly fluid, this is still only about 1.5 barrows to the 'heavy duty' mixer load.
In my mis-spent youth I worked for a time with a building firm as a labourer and unless my brain is even worse than I thought we used to get more than a barrow and a half from the mixers we used then.
Has the industry downsized the mixers in use or am I just getting forgetfull?
I have vague memories of using a mix of 9 shovels of ballast to half a (hundredweight) bag of cement. However this would probably equate to a 110 litre mixer. My spreadsheet suggests that a 110 litre mixer should take just over one
25kg bag of cement which suggests that 9 shovels and half a (50kg) bag would give a mix slightly leaner than the C20 we were previously discussing.
So am I heading in roughly the right direction?
Bag of cement per mix, and producing 1.5 barrow loads of concrete?
Cheers
Dave R