Concrete Casting

I need a little more information but , essentially, I have mix designs which I have used as low as 25 below zero F. These will produce 8,000 psi

Jonathan 720-308-8906

teslaq-was-right@hotmail.com

you cannot let cement freeze as it sets. The water goes into ice crystals and this starves the concrete of the water of hydration it needs to cure = weak concrete.

you can also get burst forms from expansion. do not do it.

People who must pour cement in cold weather use heaters and plastic sheets to keep it above freezing for cure to take place

search from here

http://irc.nrc-cnrc.gc.ca/pubs/ctus/8_e.html

There are several ways, two common methods are to use chemical accelerators and entrained air admixtures. Check the PCA (Portland Cement Assoc.) manual.

http://www.cement.org/basics/concretebasics_concretebasics.asp

lots of other links on that page.

from what I can see the special formulas that will set at very low temperatures make some tradeoff in final strength or cost of ingredients

Yes, there is a tradeoff. The admixtures can become quite costly. The compressive strength of the concrete placed is usually higher than the required final strength to compensate for strength loss, also increasing the costs (mixing water temp, water reducers and other admixtures). Thus, placing in cold weather is always avoided when possible.

The general answer is yes of course, but you offer no specifics as to the "specification", volume, shape and location of the casting: i.e.: Is it a large volume casting with minimal surface area - a compact shape? Is it above grade, at or below grade? Is it exposed to wind? .......................

The most obvious thing you left out was the lowest expected temperature to be designed for during the cure.

Since the curing (hydration) is an exothermic chemical reaction, heat is produced, and the larger the volume (and volume to surface area ratio) the more this internally generated heat becomes significant. If the temperature doesn't dip very much below 0° C, especially for only short periods, insulation around the concrete may well suffice without resorting to additives. Using a faster set cement, heating the water (not to exceed 50° C or so) are other aids.

However, always err on the side of caution.

If it does freeze, its ruined, but you knew that already.

Some very useful relevant information can be found at: http://www.aggregateresearch.com/caf/press.asp?id=10121