Currently (Dec 2011) doing fence posts and some small concrete pads around the house so I need to self mix the concrete

Here is a good example of what is required from the "General Purpose Cement Product Data Sheet" on Boral's Site

From my learnings if you mix in the following shovel fulls of Cement/Sand/Aggregate you will use approximately the following bags of cement per m3 of concrete

Cement | Sand | Aggregate (gravel) | Bags of 20kg General Purpose Cement per Cubic Metre | Comment |

1 | 2 | 3 | 16 | Strong but costly |

1 | 2.5 | 4 | 13 | Good for fence posts |

The more cement the more costly of course so don't over do it.

Can you assist by confirming how many 40kg bags of cement do I need per cubic metre volume?

Thanks

If itβs 13 bags of cement for 20kg bags it will be 6.5 bags of cement for 40kg bags.

Are you sure that's 20 kg of cement per bag james?

I'm not sure if I understand exactly what you mean, but in Australia the standard weigh for a bag of cement is 20kg.

How many 20kg general purpose ready mixed concrete bags do i need for .56 cubic metres

If it's 13 bags of cement for 20kg bags it will be 7.5 bags of cement for 40kg bags.

I found from Boral 1m3 of cement you need 108 20kg bags (54-40kg) premix bags or For a one 20 kg bag equals 0.01m3.

This should be easier to understand.

Great thanks Jarod

How many bags of concrete do I need for a 3.1m x 3.1m x 110mm slab?

C'mon Allan - thats just lazy ?

3.1 x 3.1 = 9.61m2 x 0.11 = 1.05m3

James' estimates for 1cubic meter will be close enough for your slab.

Thanks Drew π