Cold weather concrete

I'm a GC in central oregon. My concrete guy poured out 15 yards yesterday for the flatwork around a house I'm building. For some darn reason he didn't think he'd need blankets last night. Needless to say, it got down to 21 degrees last night. I noticed this morning that there were a few areas that were starting to turn light gray. It looks like the thing is ready to freeze pop. I've put in a call to his cell saying that we'll need blankets for tonight.
Basically, if the thing freeze pops and starts spawling, then I'm going to be in a fight with him on getting paid...and ripping the job out.
Does this seem like he should have to take care of it or am I off base?
-Dan
-
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I'm a GC in central oregon. My concrete guy poured out 15 yards yesterday for the flatwork around a house I'm building. For some darn reason he didn't think he'd need blankets last night. Needless to say, it got down to 21 degrees last night. I noticed this morning that there were a few areas that were starting to turn light gray. It looks like the thing is ready to freeze pop. I've put in a call to his cell saying that we'll need blankets for tonight.
Basically, if the thing freeze pops and starts spawling, then I'm going to be in a fight with him on getting paid...and ripping the job out.
Does this seem like he should have to take care of it or am I off base?
-Dan
-
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Daniel Vance wrote:

not be an indiaction of trouble. I would be more concerned with the question of wether he cured the concrete with a curing material than the fact that it was not covered on the first night. Concrete needs to be cured properly to gain strength and durability. Proper curing involves keeping the concrete temperature above 40 degrees F, and moist, until the design strength is achieved. Concrete creates heat as it hydrates, and some contractors rely on this to keep the material from freezing. This doesn't always do the job, and blankets should be used to keep the concrete warm enough to gain strength. The curing material keeps moisture in the surface while the concrete is gaining strength. Concrete that is allowed to dry during early ages will loose as much as 40% of it's ultimate strength potential on the surface. When concrete is allowed to dry during curing, the chemical process changes from Hydration, making concrete, to carbonation, making chalk. Chalk is weak, porous, and lighter colored than the same material that is cured properly. If no curing agent was used, you may have a slab with a surface that will absorb water and not be strong enough to withstand freeze thaw cycles. Throw some water on the slab, if it is absorbed quickly, there is no curing agent there. If the water doesn't soak in, there probably was a curing agent used. Regarding blankets, they should be used when temperatures are expected to drop into the 30's, however, expect them to leave permanent marks on the surface. There are admixtures available that allow placement of concrete at temperatures as low as 20 degrees F without using blankets. They basically reduce the amount of water available to freeze, treat the water to lower freezing point, and accellerate the strength gain so that the concrete rapidly gains enough strength to resist freeze thaw.

to set up a training session on Cold weather concrete practices. You could also require ACI Concrete Finisher Certification training for your concrete subs.

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Amen, and quite well written. ______________________________ Keep the whole world singing . . . . DanG (remove the sevens) snipped-for-privacy@7cox.net

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I vote that he is responsible for knowing the forecast and making arrangements for protecting the concrete from freezing.
Steve.
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In general, the subcontractor is responsible to put a thermal blanket on the concrete when weather prediction calls for a freezing night. However, legally, it would be touch to prove so in court if you don't have it on paper. I am aware that many of the construction related cases rely on "common practices". In this case, the common practice is that the subcontractor is supposed to cover the concrete when there is freezing weather. No mater what the weather is, he has to deliver a non-defective product before getting paid.
How about making him paying for a concrete test to make sure that the cracks don't compromise the strength of the concrete? I haven't done a concrete test yet but I think such a test is feasible.
-vd-
SteveF wrote:

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This topic is of great interest to me. My wife and I were planning on building a concrete house but time got away from us, and now it looks like it'll be too cold to do it until spring. We live in northeastern Oklahoma, so it'll be probably February or late January at the earliest before we have temperatures down to 21 degrees. However, we've already had a soft freeze and I'm concerned that if we're pouring concrete for a 2000 sq foot house, that we should wait until Spring. Is this true or is there a way to keep the concrete from freeze?
Vinh Dam wrote:

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I think we all need more information. What do you mean by a concrete house? Footings, sure. Slab in contact with the earth, can be protected with blankets. ICF's,insulated depending on how heavy a concrete mass. Cast in place walls? There are usually significant windows of weather that allow temperatures for concrete. Are you doing the work or using subs? Are you the general? Are you worried about quality or time?
If you wait in Oklahoma for those 22 days each year when it's not too hot, too dry, too wet, too cold, too windy, you may never get 'er done. We pour concrete in central Oklahoma year round, though I prefer to avoid heavy schedules in January and February. There are a few days that common sense says that humans don't want to be out, much less concrete. Concrete reponds to real temperature, not chill factors. Oklahoma has given me a whole new respect for chill factors. I've worked in Colorado at 12 below in a sweater for weeks on end; when it's 30 above with 60% humidity and the wind is howling here, it's time to go to the house. The song says it all. . . . "when the wind comes sweeping down the plains . . . .. ."
Don't pour concrete on frozen ground. Don't pour concrete on ice or snow. Don't pour concrete in deep water puddles and mud. Pour when the temperature is 35 and rising. Protect concrete from freezing for a minimum of 3 days, 7 preferred, 28 ideal. This can be done with heaters, blankets, tents, etc.
Footings dug into soil and poured can usually survive by ground temperature alone in the proper weather window. ______________________________ Keep the whole world singing . . . . DanG (remove the sevens) snipped-for-privacy@7cox.net

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It's a Terra-Dome home. (www.terra-dome.com) The structure is poured on site. The Terra-Dome people are doing it, not me. The walls are approximately 10 inches thick. The roof is 8 or 9 inches thick, I believe.
DanG wrote:

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Work out the details with terra dome. I'm sure they have plenty of experience pouring in winter weather. If you're ready to go, there is some great pouring weather in October, November, and December. Be aware of cold weather issues and ask them how they deal with them. Your local ready mix will play a significant role in the process. I assume terra dome has their own pumps, etc. It looks as if they cast-in-place for the walls. I would be curious how they do the domed tops. It may be a gunnite type process or cast-in-place. Either would require some special form work for the dome. ______________________________ Keep the whole world singing . . . . DanG (remove the sevens) snipped-for-privacy@7cox.net

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They have forms that they use over and over from job to job. It's concrete poured onsite with loads of rebar.
DanG wrote:

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