cement quantity for concrete

I need to mix 100 litres of good quality concrete. Using 20mm (or thereabouts) ballast, What weight (Kg) of cement is needed for a 3:1 mix?

TIA

Reply to
jim_in_sussex
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Don't forget the fine aggregate - you need to fill those gaps.

Reply to
Grunff

At I:3 mix by volume you'd need 25L cement and 75L ballast Cement weighs approx 1600kg/m³ = 1.6kg/L so you'd need 40kg = just over 1½ bags.

I:3 is a *really* strong mix though. 1:6 is good quality, so one 25kg bag of cement would be perfect.

Reply to
Peter Taylor

About 15 good shovels. Why are you going 3:1 with concrete, though?

Reply to
Chris Bacon

He's using ballast.

Reply to
Chris Bacon

Various online calculators:

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Reply to
Phil

The message from "jim_in_sussex" contains these words:

Concrete is usually specified in terms of volume and with 3 constituents

- gravel, sharp sand and cement - and 3:2:1 is a very strong mix.

According to my ancient source of information a cubic yard of 3:2:1 concrete requires 0.748/0.499/0.299 cu yards of each constituent or

0.794/0.601/0.271 tons. Oh yes and 30.9 gallons of water (which presumably assumes that the aggregate is perfectly dry, an impossibility in my experience).
Reply to
Roger

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