concrete

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Was hoping to lay concrete base 6metres by 3metres. Temperature this morning below freezing. Whats the groups advice for laying concrete in this weather? Any help gratefully accepted. Thanks

[Andrew Mawson]

Don't if you can delay the job.

If you really have to have it down today get them to put the appropriate ad-mixture in the mix, and when down and beginning to harden cover in hessian and straw.

AWEM (who for years had a crumbly concrete apron that he'd laid when it was too cold - now replaced)

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[Rick]

The stuff must set, before the water freezes, or even gains small ice cristals.

Its best to wait.

Rick

[Andrew Mawson]

message

Speak to your concrete supplier - they should be able to dope the mix

AWEM

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[Ian Stirling]

It is possible to heat the concrete, while it sets, to avoid freezing. If you have it, a simple layer of straw on top of it, and a tarp over that will do - the concrete will generate its own heat. A heater set to "frost" also can help.

[sPoNiX]

Must make cooking a bit difficult.

sponix

[Andrew Mawson]

Yes a tad heavy round the neck cord

Seriously though, when it was taken up to extend the garage forwards although the top couple of inches was basically compacted ballast the bulk of it was pretty hard - certainly the JCB puffed a bit of black smoke hoiking it out !

AWEM

[Rick]

Don't

Concrete (normal mixes anyway) should not be laid when frost is present or likley. Wait until there is no frost on the ground, if frost is likley within first 48 Hrs .. then insulate the top ... ideally with a layer of straw and top with poly sheet - or as a minimum a thick tarp.

You can get frost proofer added, but it is far better to do without ... as theses are accelerators, and can weaken the finished strength.

[meow2222]

Best thing is to add an antifreeze. Dilute sugar makes a good antifreeze ;)

Unfortunately I haven the heart, dont do that, least not unless you want to play expensive party tricks.

NT

[Rick]

Also if Building Regs are involved (they may not be for this) they would be in their rights to refuse to accept this without a full lab analysis ... of a cured cube of the mix, for compressive strength.

If Bld Ctrl not involved you can do as you want ... persoanlly I would go buy a 5 litre container of FEB accelerator and add that to the mix ( if home mixing)

[Weatherlawyer]

Note the term "or likely" ignore the "when frost is present" bit.

They put new sea barriers on the coast of North Wales after a flood one winter. Some of them were poured in frosty weather and even though the centre of the pour may have been (but who can say?) OK, the top of the pour on each mold that got filled in such weather, was flaey and required a lot of subsequent maintainance.

I rather think that had the firm been made to remove the affected sections the job would never have been finished. I imagine they will fail sooner than the rest due to the overseers compromising. But that is conjecture.

The point I am trying to make to the OP is that if you make the pour and the concrete fails, you will have to take off any subsequent building, dig up the concrete and pay to have it removed, re-lay more concrete and re-erect the building. All for the sake of waiting a few days or even weeks.

Stop hoping and start thinking. How much is such a scenario going to cost if there are services to be taken into consideration too? And how much is it going to cost you to wait?

You can get around it by setting straw or sawdust smouldering on top of it if the weather is cold enough for frost, as such weather is usually accompanied by calm air. It's a method used in orchards for millenia. I have even seen it used on pig farms where the porkers were kept outdoors in tin sties.

[Rick]

hang on a tad .... look at my words ...

To infer that the concrete mix used for sea barriers is a 'normal mix' is incorrect.

I have laid a slipway, where we had only 4 hrs between tides - no problem, but we used a specific mix for rapid hardening & suitable for continued salt water immersion ... not in any way a normal mix for domestic concrete.