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Concrete Raft Curing

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Aden30mm

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I wonder if someone can provide me so,me advice on concrete raft curing.

I laid yesterday a concrete raft for a new shed the raft size is 12ft X 7ft, the thickness varies but overall is is about 4 inches. The sub base is a mixture of sound concrete and well compacted sand/ballast. I used a 1 cement to 4(mixed ballast) mix, placed a expansion gap in the middle of the raft. The weather was a barmy 11 degrees C, last night is did not dip below 6 degrees.

The concrete was covered over with a tarp suspended on wooden post maintaining an air gap, the sides of the raft were further protected by hessian.

I worked out that I've got 56 hours until the temperature drops to 0, my perception is that initial curing will have taken place, and the danger from frost will not be an issue.

The question is will this be satisfactory or do I need to do anything else? I don't wish to use any heat if possible, as it would have to be electrically driven.

Kind regards

Aden
 

PAC1

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You should be ok without any measures. All I would say is it is best to cover the slab over for a week with hessian or a tarp or even newspapers. It is certainly not necessary to heat the slab it would be a pointless and expensive exercise.
 

John15

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Hi Aden,

The 2 main rules when dealing with freshly laid concrete are 1. Keep the surface moist or covered with a membrane to prevent fast drying and so allowing the cement in the mix to fully hydrate. Fast drying risks cracking and low strength - not such a problem in winter of coarse. 2. Keep the surface of the slab above 2^c, or better still 5^, to prevent the water at the surface from freezing. This can be done with thick hessian or something similar suspended a few inches above the slab.

Hope this helps,

John
 

Aden30mm

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Yep, just checked the raft, looking good surface water has migrated. I looked at a website and the setting time of 15 hours at 4 degrees seems to work. I did incorporate some frost proofing into the mix, but I under dosed, but it hopefully should provide a small margin of protection.

The site is quite sheltered protected from wind and is covered by a tarp on battens. Just have to keep my power dry and the faith in the lord time.

Thanks for the feedback.
 
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