Page 1 of 1
Posted: Sun Jan 02, 2011 10:18 pm
by woodfit
Hi all
First post so here goes...I am looking to lay a base for a 10ft x 12ft shed around 4 to 6 inches thick and will order the ballast and cement (Grab bag) from my local merchants but how can you work out how much to order because obviously aggregates are sold by weight and not volume so is there any way of working out how much I will need in relation to the size of the slab I want to mix and lay??
Tom
Posted: Mon Jan 03, 2011 8:28 am
by Mikey_C
the calculators for converting concrete volume to material weights for C20 concrete is here about half way down
general info about concrete, mixing on site, ordering and health and safety is here
info if you decide to vary the mix a bit because you want it stronger is here
tonne grab bags can contain as little as 850Kg.
read digest and come back if you have any further questions 
Posted: Mon Jan 03, 2011 12:25 pm
by dig dug dan
generally a tonne bag contains 0.6 of a cubic metre.
So for a 10 x 12 (3m x 3.6m) you will need just over a M of ballast (assuming you are doing 4")
By the time you have brought two tonne bags, all the cement, you would be better off buying ready mix. its not much more expensive, its all the same strength, and a lot less hassle.
As a rule of thumb for me, if its 1 cubic M or more, i ready mix it. if its less, i mix by hand.
Posted: Mon Jan 03, 2011 1:18 pm
by msh paving
dig dug dan wrote:As a rule of thumb for me, if its 1 cubic M or more, i ready mix it. if its less, i mix by hand.
same hear dan, not worth messing making more than 1 m cube
MSH
Posted: Mon Jan 03, 2011 2:13 pm
by Tony McC
It's not just the hassle of mixing a cubic metre or more, it's the problem of consistency, knocking out 20-odd mixes and hoping that you;ve got the quantities right each and every time, and a regular slump.
At least with ready mix, you know it's all one strength, all one slump.
Posted: Mon Jan 03, 2011 2:53 pm
by lutonlagerlout
a metre of readymix if you use the mixer companies should cost about £150
believe it or not me and my old man knocked up 20 tonnes of ballast 1 day with a barrowmix mixer,the good old days NOT
cheers LLL