Work out how many cubic yards you will use ((60/3) X (40/3) X (5/12/3)) for the shed plus the drive ((20/3)X(20/3)X(5/12/3)) for a 5 inch deep concrete layer. I guestimate thats about 40 cubic yards. Where I am readymix delivered within about 10 miles of the plant costs about $150 per cubic yard. That comes to the massive amount of $6,000.
To that you should allow for re-inforcing steel maybe 16 sheets at around $15 per sheet under $300. Plus formwork if you have to buy it say $500 plus fibre expansion joint allow $200.
So around $7,000 pure materials plus rental of a concrete pump @ $500 per half day if you need one, rental on an agitator & skimer for the day maybe another $500. Then it depends on how many friends you can get together to help you for the day + beer and barbeque meat etc.
If you have to pay for professional help you can probably double the materials cost to get the job done.
Anyway thats how I would go about estimating how much concrete would cost me. Plug in your local numbers but however you look at it its expensive and I can tell you its hard work doing it yourself.
