How do i calculate concrete ingredents?

joeb99 · 5 Feb 2007

I need to make C35p concrete, 1:2:1 cement:sand:gravel.

I need to make a total of 0.77 cubic metres, how much sand, cement and gravel do i need and how do you calculate this???

Joe

denso13 · 5 Feb 2007

0.77 cubic metres is about 1.6 tons.

So by weight it is about 400kg cement, 800kg sand, 400kg aggregate. There is water too, obviously, but that should give you an idea.

joeb99 · 5 Feb 2007

How did you get from 0.77 cu. metres to 1.6 tons? Is there a conversion factor (looks like cu.metres x 2)

J

denso13 · 5 Feb 2007

1 cubic meter of concrete equals about 2.1 - 2.2 tons

joeb99 · 5 Feb 2007

Thanks denso13.

One last thing, so i dont sound silly when ordering the stuff, what sort of chippings do i ask for at the builders yard?

denso13 · 5 Feb 2007

10mm clean aggregate, whin chips in these parts , easier to work with than the larger stuff

joeb99 · 5 Feb 2007

denso13 said:
10mm clean aggregate, whin chips in these parts , easier to work with than the larger stuff

Thanks, i've called the yard and they call it 'half to dust' so i've ordered that - guess that means half inch in size down to just dust.

Funny thing is B and Q are actually cheeper for cement and chips. The yard refused to match their price, but i cant get 1.5 tonnes in the car!

Oh well, it'll be here tomorrow ready for laying.

topgun · 6 Feb 2007

Try this site http://www.diydoctor.org.uk/projects/mixing_concrete.htm

Bigburn · 6 Feb 2007

Why dont you just get a readymix company to deliver the concrete ?.

joeb99 · 7 Feb 2007

Is that a cheeper way to buy it? Its in the kitchen, round the back of the house, so would need to be pumped round about 50ft.

denso13 · 7 Feb 2007

Easiest way is to phone up local suppliers and compare against the cost of materials.

It would be 1 cubic meter delivered which wouldn't be cost effective from the larger suppliers as you pay for the vehicle not being full.

Some local companies may deliver a small amount for a reasonable price but you would have to check.

Sounds like a barrow job as well, but then it's not much.

joeb99 · 7 Feb 2007

Yeah, they delivered the materials yesterday.

I bought a tonne of sand, and 20 bags of cement (half tonne), and 20 bags of aggregrete (half tonne).

Shifted it all round the back of the house ready for tomorrow.....

iangh · 9 Feb 2007

hope you have a mixer!

joeb99 · 9 Feb 2007

Well, i chickened out of doing it today, so starting to mix tomorrow (sat) at 7am.

The mixer is sat in the kitchen, next to the fridge and 20 bags of cement ready to go.

What should i use to 'tamp' down the pour? any tips?

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How do i calculate concrete ingredents?

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