Curing Concrete-Colder Temps

[James "Cubby" Culbertson]

Hiya folks, I poured a 1 CY foundation for an outdoor fireplace yesterday afternoon. Temps here are ranging from highs in the 50's to lows in the mid 20's. After pouring, I covered it up in plastic and put around 6-8" of straw over the top of it. This morning, the concrete is visibly wet with a bit of standing water on it in places. I've always poured in the summer and have seen the stuff cure pretty quickly. I suspect this is normal for these temps but was looking for any expert opinions on this. I was planning to start putting my CMU etc... down probably next week but at this rate, I'm not sure I'll be able to. How long should I leave the plastic/straw in place before working on it? Thanks much for any inputs. Cheers, cc

[Joseph Meehan]

It all sounds right to me. I don't see why you would have a problem with your plans.

[PanHandler]

Remove the straw and plastic during daylight hours. Curing concrete creates heat, and the condensate puddles you see can't evaporate through the plastic. Sounds normal to me.

[James "Cubby" Culbertson]

Thanks folks. Sounds like it's more of a waiting game at this point. I suppose that will ensure I get the strongest concrete I can anyway. Cheers, cc

[louie]

Remember this: concrete curing is NOT an evaporative process - ie. the concrete does not really need to "dry" in order to cure. In fact, it's better for the end strength of the pour if it is kept moist during the cure process. There is a chemical reaction that combines the water with the portland cement in the concrete mix. The cold weather will probably slow down this reaction, but the moisture will actually help it in the long run and won't slow the cure down any.

[James "Cubby" Culbertson]

That's why I covered it in plastic and am keeping it warm. I'm just not used to it taking more than a day or so for it to hit high enough strength that I can start setting block on it. Cheers, cc

[George E. Cawthon]

If you want strong concrete, keep the plastic on to retain moisture and keep the straw on to retain heat and avoid freezing. How long? however much you want, but most of the strength develops in a few days. anything amount of time is better than pulling forms off and letting it dry out the day after you poor it like they do around here for foundations.

[James "Cubby" Culbertson]

Same here. They pour one day and are building on it the next. Maybe they are using high early strength concrete, but I doubt it. I'm headed back to work tomorrow so really the first chance I would have to do anything with it would be Monday. So a week would probably be ok for me to set a couple of courses of block on it. Cheers, cc