Getting ready to pour a four foot ICF stem wall next week.
Temps are projected to be lows in mid teens and highs in the mid 30's (F)
It has been years since I poured in weather this cold.
Any new recommendations for concrete mix, additives, etc.?

OK, all you guys for MN and other points north, stop laughing, and remember,
I'm from Kentucky, and this is pretty cold for us.  Not even sure my blood will still flow
when it's that cold outside.

This time of year in upstate NY the concrete co. mix with hot water. We pour either a 2 or 3 slump and add a mid to high range water reducer, which takes the slump up to a 6 to 7. This reduces the water in the mix by 30 to 40 percent. If your temps are not in the super cold range for a long period of time you should be ok.

Posted By smartwall on 04 Dec 2010 09:41 AM
This time of year in upstate NY the concrete co. mix with hot water. We pour either a 2 or 3 slump and add a mid to high range water reducer, which takes the slump up to a 6 to 7. This reduces the water in the mix by 30 to 40 percent. If your temps are not in the super cold range for a long period of time you should be ok.

Pretty much the same here in Alberta. We pour as long as the concrete pump truck can operate. We do usually lay a 2 x 10 or something on top of the poured wall to protect the top concrete from frost damage.

If you have heat blankets, you could put them over the top of the wall. A 2 x 10 is nice, but it gets cold and that can affect the concrete

Timely topic for lower Saskatchewan. 

If a person is using the Fab-Form system for a mono pour 4' frost wall, and the temp is -10C, and the ground already has 18" of frost, how would you treat both the ground prep and protection of the "footing" area after the pour.

Also, what is the product you refer to that takes the slump of 2-3 to 6-7 (reply directly SVP if you don't care to mention trade names).  

With the heated water in the concrete you shouldn't need to add any extra heat. Just be sure to insulate any exposed concrete (tops of walls, as well as bottom of windows). You can insulate with batts, rigid foam, or insulated tarps (if you use batts, I would recommend laying poly down before the batts to keep the fiberglass from getting stuck in the concrete).

The concrete will generate enough heat as it cures to keep from freezing within the walls. If you want extra heat during curing you can add accelerator, which will generate additional heat as it cures.

The coldest pour I have heard of was at nearly -40 Celsius (which is also about -40F). A redi-mix near Winnipeg, MB, Canada poured without adding additional heat (other than heated water in the mix). Apparently the concrete froze before falling off the chute of the truck, but once in the wall it cured perfectly. Thermometers placed inside the wall showed the coldest concrete temp within the first week was +13 Celsius at the footing. (If someone is more familiar with this project, feel free to correct the details, if I have gotten in wrong.) This goes to show the versatilty of ICF in any condition.

I read about a builder (sorry, don't remember where) and his cold-weather pour. He used a throw-away propane water heater salvaged from a plumber friend's recycle bin, a couple of loops of pex in the pour and a circulating pump. With the heater at its lowest temperature setting and the pump running continuously for several days, the whole pour cured properly. The pex was just abandoned in the now-solidified concrete and the water heater discarded. Again..

I use Fritz-Pax. I dose my concrete on site. Some of the water reducers will fall out of solution in 35-45 minutes. The Fritz-Pax are in bags that disolve in water, you just add them to the mix and rotate the drum at high speed for 5 minutes. As far as the Fab-form the one weakness is that it retains water so you would have to open up the plastic to allow the water to evaporate. In cold weather the best insulation is straw. The plastic idea is not a good one for the same reason, if you retard the flow of moisture it will take longer for the concrete to dry. Two ways you are going to dry an icf wall, footing and the top of the wall. cover either and it will take longer. Lower slump is the answer. unfaced batts are good they will wick water and insulate. Who cares if it sticks to the top it's easy to remove.  I checked the Friz-Pax site and there is a distributor in Edmonton.

Why do you want to let the water escape? Concrete does not simply "dry out" it CURES. Trapping the moisture inside the concrete will actually result in a stronger concrete mixture. The design strength of concrete is normally reached at about 28 days. If the concrete cures in an open-air environment, this will be its final strength. However, in an ICF form, the moisture is trapped inside the forms allowing the hydration process to continue much longer (some say the concrete will continue to gain strength forever - I don't personally think it is this extreme). In ICF the design strength is also reached at the 28 day mark, but it will continue to gain strength beyond this to perhaps 25-30% more than the original design strength. It is the same idea as pouring a floor and using wet tarps or covering the slab with water - trapping the moisture will increase the finished strength of the concrete.

I would not reduce the slump of the concrete simply to ensure proper consolidation. If the mixture is too dry, it will not flow in the wall as well and this will increase your chance of having voids/honeycombing.

The pex tube idea is interesting - I like the fact that the heater cost him nothing and the pex tube was minimal cost. I know of a builder that does the same thing with heat tape. He lays it out at the bottom of the wall, builds the ICF wall above, then simply insulated the top of the wall and plugs in the heat tape allowing the heat to radiate up through the forms, warming up the rebar and removing any frost. The heat tape can be either removed before pouring or left in the concrete.

See what happens to your concrete when your moist concrete freezes. The temp here this morning is 3 degrees. Hasn't been above freezing for 6 days. Reducing the water content of the concrete also increases the stenght. Using a water reducer increases the slump without adding water. Sounds like you've read the books but have little on the job experience dealing different pour conditions.   I poured a job in Jan 08 that stayed green for 2 months luckily it stayed above freezing for most of the time.  Different areas require different techniques.

You are correct in that adding a plasticizer will allow for better concrete flow within the forms.

As far as cold weather experience - I have successfully poured concrete into ICF at around -25 degrees Celsius. I am telling you what I have done and let you know it works.

By trapping the heat generated by the concrete within the cavity (using a combination of the insulation already present on the forms and adding insulated tarps, batts, etc to any exposed areas) you are keeping the space in that cavity ABOVE FREEZING - this includes the concrete. How will the water be able to freeze if the temperature is not below freezing?

When you were suggesting that opening up the plastic will allow the water to evaporate - if the air is below freezing, wouldn't this exposed moisture freeze, rather than evaporate?

Ok I give. I installed my first icf in 1989 but I'm still learning everyday. So your saying that by covering the icf with a water impermiable cover that a form of osmosis will remove the water. The heat tape idea is crazy. I wonder how many mega watts of power you would need to raise 3 slump concrete above freezing for a two week period. Three slump concrete weighs 165lbs per cu. ft.,so an average 1300 sq ft wall would contains 141,500 lbs of concrete with the wall insulation having an r-value of 10. Dana I need your formulas.

The heat tape is not used to heat the concrete - it is plugged in prior to pour just to warm up the inside of the forms and remove any frost from the rebar.

Wes, I hope your pour went well. I'll throw in my most recent experience with cold weather ICF building. We poured 800+ yards in upstate New York on a project spanning late December of 09 to March 10. We poured at a 5 to 5 1/2" slump with concrete that had to be at least 50 degrees going into the wall. The only way the supplier could get the temps was to store the sand and stone in a heated ICF.....go figure....building and transfer it to the plant as it was batched. We would lose about 5 degrees from the truck to the end of the hose at 15 degrees. It was common for it to be 5 to 10 below the night before the pour. The concrete would average 55 degrees going into the wall and with sensors we put in the wall we discovered that the temps would rise to about 125 degrees within a few hours without any excellerants. We would cover the exposed concrete with batts to protect from frost. We were getting three day breaks within 90%. Cold weather ICF construction is not fun but can be done with success if planned right.

Strangely enough, concrete is strongest when you cure it underwater and weakest when you let it dry out. But it is also stronger with less water in the original mix and weaker with more water in it.

Thanks for all the info, folks.
You know the old saying, 'If you don't like the weather, wait 24 hours'. Well, I waited 48 hrs, and got above freezing temps. It's turned cold again, but the concrete is in.
Thanks again.