Concrete question on number of bags

[mogga]

How many bags of readymix concrete would I need to fill a volume of
approximately 0.25 cubic yards.

Google tells me

0.25 (cubic yard) = 191.138714 litres

Which I thought might help.

But then I see concrete (ready mixed) is in 20kg bags.

and this page says
http://www.coateshomecentre.com.au/tips_tricks/tip_how_many_bags.htm
Allowing for waste you will need about 110 x 20kg bags of concrete per
cubic metre

1 yard = 0.9144 meters
Which for rough calculations is about the same
so .25 of a cubic yard is about the same as .25 cubic metre

which means 1/4 x 110?

= about 27

Which sounds a huge amount.

What have I done wrong?

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[RubberBiker]

Sounds about right, concrete is roughly 2.2 tonnes per cubic meter -
so that is 110 of your 20kg bags - and you're using about a fifth of
that.

You might be better off hiring a mixer and making it up from cement
and ballast - you *always* find out that more is required than
estimated.

[mogga]

On Fri, 12 Jun 2009 12:28:45 -0700 (PDT), RubberBiker <d...@gglz.com>
wrote:

Thanks!

[A.Lee]

mogga <d...@NOSPAMPLEASEmogga.com> wrote:

> How many bags of readymix concrete would I need to fill a volume of
> approximately 0.25 cubic yards.

> 1 yard = 0.9144 meters

> Which for rough calculations is about the same
> so .25 of a cubic yard is about the same as .25 cubic metre
>
> which means 1/4 x 110?
>
> = about 27

27 x 20kg = 540kg.
Maybe a little high, but not too far out.
A cubic metre of water weighs 1000kg. Concrete is denser than water, so
at least 2000kg of concrete for 1 cu.M. Thats 500kg for a quarter cube.

It is only 7 to 9 wheelbarrows full.

Alan.
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To reply by e-mail, change the ' + ' to 'plus'.

[The Natural Philosopher]

wuss. I used 6 wheelbarrows to the ton..;-)

anyway OP: buy a 'tonne bag' of aggregate and use 3-4 shovels of that
for every shovel of cement, and buy cement *as needed*.

Any left over, use in the garden - the aggregate, not the cement. Tip it
in boggy spots and topsoil over :-)

> Alan.

[Tim S]

RubberBiker coughed up some electrons that declared:

> You might be better off hiring a mixer and making it up from cement
> and ballast - you *always* find out that more is required than
> estimated.

Unless you book an RMC lorry - in which case you always find you ordered 1
cu yard too much and the bloke is going to drop it on your garden whether
you like it or not!

[Tim S]

mogga coughed up some electrons that declared:

Nothing - 0.25m3 is actually a *quite a lot* of concrete weightwise, in
terms of mixing and barrowing the stuff. OK, it's next to nothing in
building site terms... But 27 seems reasonable guestimation wise...

You'll want to hire a mixer - even a little one and say 10-13 batches would
be less painful than trying to hand mix that lot.

Cheers

Tim

Says he who did 8 *big* mixer loads of sand/cement screed the other day,
about 2/3 ton and that was enough work for an afternoon...