Weve got to mix C40 by hand for a top down underpinning job, as the pins are quite small we are going to mix it by hand, i cant seem to find a ratio for c40, most other mixes, but not C40....any words of wisdom appreciated.
Mix ratio of C40 concrete
- Thread starter handyman77
- Start date
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1: 1.5: 3, approximates to a C40 concrete, but strength also depends on water content, compaction etc.
Thanks Tony!
Just to specify we are using ballast and cement, i was thinking 3: 1: with minimal water to comply with the slump test.
Just to specify we are using ballast and cement, i was thinking 3: 1: with minimal water to comply with the slump test.
The reason you can't find a prescribed mix ratio for C40 is it doesn't exist. BS5328 only goes up to 25N and anything above 20N can't be mixed with all in ballast. That's not to say you couldn't end up with a mix higher than 25N - just that it's not predictable based on the mix ratio. The only way to guarantee 40N is readymix.
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Underpinning and mixing by hand, that’s not the greatest of combinations I’d want to see.
If this is a subsidence job any future buyer will (or at least their mortgage provider will) walk a mile unless the works have been carried out by a contractor and have an insurance backed guarantee ……
If this is a subsidence job any future buyer will (or at least their mortgage provider will) walk a mile unless the works have been carried out by a contractor and have an insurance backed guarantee ……
I have been recommended a readymix bag of concreting with a strength of 40n. Is this sufficient?
And in answer to your smartass comment freddie, this is a new build that we have to cast as a first ring then an underpin ring then the base, this is all specified by an engineer. There is nothing above at the moment.
And in answer to your smartass comment freddie, this is a new build that we have to cast as a first ring then an underpin ring then the base, this is all specified by an engineer. There is nothing above at the moment.
It ain't smartass! We don't know what you're doing do we? 
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