MikeCapon
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| posted on 21/10/10 at 07:41 AM |
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Fresh concrete - Frost damage?
Any builders that can give me a bit of advice please. I poured a bit of concrete yesterday and during the night the temperature dropped to 0°C. Is
that likely to have damaged the concrete?
The job in question is a biggish lintel (1.70M x 0.2M x 0.5M) with 4 10mm dia lengths of rebar across the opening. 3 mixer fulls of 1/2/3 concrete. It
looks fine this morning but I could do with some reassurance.
Anyone?
Thanks in advance,
Mike
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Strontium Dog
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| posted on 21/10/10 at 07:48 AM |
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It depends what it is for. If it is load bearing I would be concerned. When I was building a lot we used to stop concreting or block laying at 4 deg.
Having said that, concrete sets by an exothermic reaction and so may have been warm enough to be ok. Another other point is that when making load
bearing lintels, the reinforcement is usually pre tensioned and held under tension until the concrete has set so your home made lintel might not be as
strong as a proper one!
As I said though, depends what you are doing with it and if you can see no cracks and it's not crumbling then it's probably not frost
damaged!
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Ben_Copeland
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| posted on 21/10/10 at 08:08 AM |
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Did you cover it over? or just leave it open to the elements?
Ben
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MikeCapon
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| posted on 21/10/10 at 08:11 AM |
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quote:
Originally posted by Strontium Dog
It depends what it is for. If it is load bearing I would be concerned.
It is load bearing because its a lintle.. Not huge loads though. The opening is 86cm wide and the only load is the lintle itself and the poured
concrete above it. The weight of concrete directly above the opening is no more than 350kg.
quote:
When I was building a lot we used to stop concreting or block laying at 4 deg.
When I poured the concrete yesterday afternoon the temperature was 10°. Forecast was for 3° overnight. It was only this morning when I saw 0° on the
max/min thermometer that I got my worry beads out....
I've got some more to do today. Do you think I should wrap it up to keep it warm tonight??? Forecast is for 9° today and 4° overnight...
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MikeCapon
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| posted on 21/10/10 at 08:16 AM |
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quote:
Originally posted by Ben_Copeland
Did you cover it over? or just leave it open to the elements?
I did cover it Ben but only with a light tarp to protect it in case of rain. Of course the sides and bottom were 'protected' by the
shuttering which is 27mm thick planking.
I'm thinking now of wrapping it all up nice and warm with something that will insulate it a bit more.
How long is it vulnerable to frost damage? How long do I need to protect it for??
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Ben_Copeland
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| posted on 21/10/10 at 08:18 AM |
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If its covered it should be ok, as the heat will be retained under the cover. As long as it looks ok when you take the shuttering off i think
it'll be ok.
Ben
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pewe
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| posted on 21/10/10 at 08:23 AM |
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Based on my limited experience I reckon it will be OK - if it was only 0 deg. and covered the likelihood is that the setting reaction will have kept
it warm enough. By tonight it should have gone off enough not to be a problem but I'd still cover it.
Cheers, Pewe. 
PS Don't know about frosty but your avatar always sends shivers down my spine!!
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Strontium Dog
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| posted on 21/10/10 at 08:56 AM |
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Ha ha! When I said "load bearing" I was thinking of TONS! If you see no evidence of cracking and you had it covered you should have no
problem. It should be safe now unless we get a really severe frost. Keep it covered for the next 3 days to be sure while it is still fairly green and
all should be well. You can always chuck some mesh or bar in the third of a ton you are going to pour next if you are worried about it!
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v8kid
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| posted on 21/10/10 at 09:44 AM |
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SD is right you will have no problems especially since it is not loadbearing. The shuttering and the tarpaulin will be adequate for a light frost
overnight.
If doing it again you might consider admix and putting a good few layers of wrapping round it to insulate.
You'd be surprised how quickly the sales people at B&Q try and assist you after ignoring you for the past 15 minutes when you try and start a
chainsaw
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MikeCapon
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| posted on 21/10/10 at 11:52 AM |
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Thank you all. As ever you have come up with the goods. And I've put away the worry beads for next time I go to do something I haven't got
a clue about.
It's going to be 4° tonight according to the forecast so I'll wrap up the stuff I'm pouring today to keep it nice and warm till
tomorrow.
All that's left now is to explain to SWMBO why the new boilerhouse is wearing a sleeping bag when she comes home from work.
All the best,
Mike
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DavidW
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| posted on 21/10/10 at 12:27 PM |
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quote:
Originally posted by Ben_Copeland
If its covered it should be ok, as the heat will be retained under the cover. As long as it looks ok when you take the shuttering off i think
it'll be ok.
I agree.
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