Pouring concrete in the cold

[kebwi]

This all the information I found on Sakrete's website (I'm using HD, so Sakrete, not Quikrete, but it must be the same stuff!!!):

Can concrete be placed in temperatures that would be too hot or too cold?

Concrete mixes should not be used when temperatures are less then 40 degree’s or above 90 degrees.

I was unclear about their phrasing. Bottom line, under what conditions should I not pour my hearth slab? Presumably this is governed by the temperature the following night, and perhaps subsequent unknown number of nights, but I'm unsure how their vague phrasing should be applied.

Thanks.

[KINGRIUS]

Re: Pouring concrete in the cold

Have you tried calling sackcrete's help line? One of their engineers should be able to answer you question.

[Schenkk56]

Re: Pouring concrete in the cold

I could swear I saw a note about spiraling the dome bricks in a pompeii in this string before I logged in this evening.
Just finishing my 56 x 56 slab and have decided to go with a pompeii. Would like to see pictures of a spiral construction that might have been built in this century.
I'm in upstate NY and hope to be laying brick for a few weeks yet. Do temps under freezing affect the set of mortar (or Heat Stop). We are hitting 30 degrees F already at night.
Figured out how to get the pompeii book last night and am happy to find design information for domes that I hadn't seen anywhere else. I read The Bread Builders and The Bread Ovens of Quebec but so far find Forno Bravo book much more complete. Love it.
I need to figure out how to post pictures one day soon.

[Johnny the oven man]

Re: Pouring concrete in the cold

This all the information I found on Sakrete's website (I'm using HD, so Sakrete, not Quikrete, but it must be the same stuff!!!):

Can concrete be placed in temperatures that would be too hot or too cold?

Concrete mixes should not be used when temperatures are less then 40 degree?s or above 90 degrees.

I was unclear about their phrasing. Bottom line, under what conditions should I not pour my hearth slab? Presumably this is governed by the temperature the following night, and perhaps subsequent unknown number of nights, but I'm unsure how their vague phrasing should be applied.

Thanks.

Pour at any temp. between 40 and 90 degrees. Initial set should be ok, cover it up and let it cure. Remember, longer cure time the better.Keep it moist for as long as possible.

[splatgirl]

Re: Pouring concrete in the cold

I don't know about mortar specifically, but I'm sure it would be the same or pickier than concrete with regard to the conditions during cure.
You can place concrete at just about any temperature, but you DO NOT want it to freeze at any point for at least a week, ideally a couple of weeks or longer. The hydration reaction is exothermic so it will keep itself warm to some extent at first, but you'd want to cover and insulate or provide heat from an external source if it's going to go below freezing at all.
It will also take A LOT longer to go off...twice or more as long as in warm weather.
I just poured a countertop slab on Monday. Temps were hovering at or just below freezing, so I tented it with a tarp and left my big hot shops light on under there to keep it a bit warmer overnight. I pulled the last of the form this afternoon, and it seems fine, but I think the jury is still out.

It won't work or finish the same as warm weather flatwork (especially bagged mix that does not have cold weather additives like what you'd get with ready-mix), but unless you want a butter smooth, perfect steel trowel finish, it'll be fine. Just don't let it freeze.

[kebwi]

Re: Pouring concrete in the cold

W.r.t pouring my hearth, what if I leave a space heater of some sort under the hearth in the wood storage area? The heat would be nicely trapped in the cubby and would presumably diffuse through the hearth to the external upper surface. I've seen photos of people doing this with their ovens, but I'm asking about the hearth concrete.

[splatgirl]

Re: Pouring concrete in the cold

yes! that plus a blanket of some sort on top would be ideal. Just don't let it get TOO hot under there. I did exactly that with part of my house build...tarp off and heat the space below with frost blankets on top. Slab stayed nice and toasty even in subzero weather.

[ThisOldGarageNJ]

Re: Pouring concrete in the cold

alright,, I dont know if this sounds too far gone,, could you leave an electric blanket on it ?? probably wouldnt help the bottom though...

Cheers
Mark