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Amazing, appreciated as always. I saw the 3ton (or just shy of) estimate on a few calculators, but good to know about the reinforcing delete.
I may be able to convince ms_com that it's something me and a mate could do. Have the mate's better half and offspring round as a distraction and call it socialising.
stevo_com-
For speed of mixing: water first (enough to turn cement into a slurry), half bag of cement, 12 BIG shovels of ballast, add more water as necessary. The bottom of each ton bag will be stonier and need less water. To put it in context, my record is 13 tons mixed in a day. 5 bags cement per ton bag, this should be slightly too much, but saves having to run off for more.
Ensure shuttering is level and measure diagonals to square it up, 4x2 timber is ideal. Start at one end and tamp down to the shuttering with another lump of 4x2 until it spills over the far end, making sure your 4x2 is in contact with the concrete all the way across. If your shuttering is right, your concrete will be.
Pro tip: dig the shuttering in half an inch deep to give a concrete depth of 3 1/2 inch. This is ample and will ensure you don't run out of ballast. Having a bit of ballast left over is less of a pain in the arse than running out!
ColinTheBald
That size of shed base with a 4" depth of concrete (more than adequate,
no reinforcing needed) would take 3 tons. There is no need for vibrateywhatsits. Presuming the dig is done and shuttering is ready, 2 muppets with a mixer and barrow could comfortably do that in a day.
@Silly_Savage: nice pointing!