Concrete type for footings
I have a question regarding the type of conrete to use for footings for a deck/pergola. I just tried to get a price for readymix concrete delivered but they told me I would need to specify the exact type and strength of concrete I want. They did however give me a quote for 20/20/80 (???) at around $220 cubic metre.
What does everyone use for concrete footings? I have seen discussions saying to avoid using the quick set stuff due to an apparent non-structural rating.
Do you mix it yourself?
I have ten posts to set (using galv stirrups) and was going to use a hole 450mm dia and 600mm deep. That's approx 0.1m3 per hole.
Also are there any suggestions for how to keep the top neat. Do you form up some type of box at ground level? Or some type of cylindrical formwork? I want to keep the top slightly above ground level so I can ensure a proper water run off.
Many thanks in advance!