Cold concrete ok

[bhads]

Thanks for the replies to my query regarding pouring concrete in cold weather. Anyhow, this morning I had the concrete poured. The pump arrived on time, the concrete was half an hour late. The first thing the readymix driver did was to ask for a cheque or wouldn't provide the concrete to the pump. I hadn't even got a chance to say hello at this point. The readymix had a 125 slump, though an 85 slump had been requested, but the pump guy assured me this was fine. We poured 5m cubed in about twenty minutes. I checked the temp of the concrete and discovered it was about as cold as tap water on a cold winter's morning. After levelling, I didn't really see the point of the insulating such a cold mix, but I did so anyway with 25mm polystyrene and some rolls of loft insulation in plastic sheets. I covered the whole lote with tarp.

Question: will this mix reach a good strength or did I make a mistake in accepting it?

TIA Bhadan.

[Tony Bryer]

If it doesn't freeze it will be fine, just take longer to reach full strength. In curing concrete generates heat: your insulation helps keep this in.

[Brian G]

Bhadan,

This would concern me "The readymix had a 125 slump, though an 85 slump had been requested". You have a lot more water in there than you asked for - and the more water you have in concrete the weaker it is!

That's why, when you ask a readymix driver to add water to the mix, he gets you to sign his delivery notes to that effect - to protect his bum if something goes wrong - like the concrete failing a crush test - did you get him to sign the delivery note to the effect that HE said the added water would be OK?

Brian G

[Chris Bacon]

It should be fine, sounds as though you've plenty of insulation there.

[bland]

I'm no expert but found this web site for professional yankee pourers last year

Googling for "cold weather curing of concrete" brings back a lot of stuff. The main thing seems to be to keep it damp for a lot longer if its cold but eventually there's no loss of strength.

bland

[Rick]

You did the right thing ... in my local it is due to hit -2 tonight, and you really don't want the prodcut to freeze before it has gone off.

Leave it coverred unless sun is out tomorrow

[Rick]

The keeping it damp is to ensure full set, concrete sets by chemical reaction not by drying out. I allways damp down fresh concrete each day for first week ...it needs water to reach optimum set, excess will not arm it after first set has taken place.