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Placing Concrete in hot or cold weather

posted by Bob Wednesday, September 29, 2010 at 9:31 AM

People who pour concrete for a living can work almost year round in most parts of the country. This is because either through trial and error or spending time reading a lot of technical journals they have figured out how to successfully place concrete even though it is sweltering hot or freezing cold. For almost everyone else I would recommend that you limit your concrete activities to more moderate weather. If it’s so hot out that all you can think about is going for a swim I would suggest you get a cold beverage, turn up the AC and forget the concrete. If it’s so cold that you need gloves, consider spending time in front of the fireplace with a good book.

If this doesn’t quite give you specific enough guidelines, maybe we should define what moderate temperatures are? This is open for debate and involves other factors but in general if the air temperature is between 50° F and 90° F you should be safe. You can safely place concrete outside of these limits but you need to do a few things to make sure your job won’t turn into a nightmare.

The air temperature by itself isn’t the determining factor on whether you should pour concrete. The temperature of the air, the humidity level, and the wind speed, the temperatures of the surface where you are placing the concrete, the water and the dry concrete in the bag all play a huge part and must be taken into consideration. The air, wind and humidity are pretty much beyond your control but some of the others you can influence. It is important to remember that the temperature of the mixed material is as important as the air temperature.

Cold Weather
If the air temperature is below 32° F I would really advise that you wait until warmer weather or call a pro. Unless you want to erect a tent with a space heater or steal your spouse’s electric blanket off the bed, this will only lead to trouble. If it is so cold out that the ground is frozen don’t pour concrete under any circumstances. The biggest issue when pouring concrete when the air temperature is just above freezing is the night time temperatures that will follow. Concrete sets much slower in cold weather. It is critical (I’m going to repeat that- critical) that the concrete sets before it is exposed to freezing temperatures. The problem is that when water freezes it takes up more space in the ice phase than it does in the liquid phase. When all of the water that you used for mixing freezes, it expands, causing your concrete to crack. The key is doing what you can to make sure the concrete sets fast enough to prevent this.

The first thing that pros do in the winter is use hot water. If you use hot water and keep the dry product in a heated area of your house or garage until you are ready to use it this will greatly accelerate the set of the concrete. You can buy products designed to set quick such as Sakrete Fast Setting Concrete. It will not set as fast as the literature says it will if the air temp is anywhere near freezing but it will set much faster than normal concrete. You can also buy additives to accelerate the set. The only concern here is the type of accelerator. If it contains calcium chloride and your concrete will contain rebar or metal wire mesh, the chlorides will attack it and produce rust. This will ultimately crack your concrete. When concrete sets it gives off heat. Not like frying an egg but there is a slightly exothermic reaction (a big word for a reaction that gives off heat-use it to impress your friends). You can use this to your advantage by covering the concrete (after it has stiffened) with a blanket. They sell blankets for this purpose so your kids won’t have to sleep in the cold. You could also put up a tent or lean to and put a space heater inside.

Hot Weather
If the air temperature is above 90° F you need to be careful. Of course what you are doing with the concrete also makes a difference. We will address that later. In addition if the wind is blowing hard and the humidity is low, even 90° might be a problem. The issue with hot weather isn’t really the heat. Neither the cement nor the aggregates have a problem with temperature. This isn’t like a chocolate bar on the front seat of the car in July. The issue is that the top layer of concrete will dry much faster than the bottom layer. As concrete dries it shrinks. This means that the top will be shrinking while the bottom is stationary. At this point you get your own north/south civil war breaking out inside the slab. There will be casualties.

To avoid this aggression you need to keep the top and the bottom curing at the same rate. There are several things you can do before and during mixing and several things you can do after placement. Before mixing store the material in a cool place or at least avoid laying it in the hot direct sun. Then use the coldest water that you find. Ready mixed concrete companies actual use ice to replace all or most of the water to slow down the set. After you have placed the concrete and it has taken a set, you need to keep the slab moist. This can be done in several ways. You can spray the slab periodically with a hose, turn on a sprinkler with a fine mist, cover the slab with wet burlap or with chemicals designed to keep water from evaporating so quickly. In very high temperatures, very low humidity or high winds you may to do this for several days. Almost everything in this discussion on hot weather is directed at someone pouring a slab. If you are mixing up concrete and placing it in a hole to support a fence post of deck, hot weather normally isn’t a problem. If the concrete is setting too fast to place in the hole, then using cold mixing water or ice will help.

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USER COMMENTS

I don't know who writes your stuff but it's great. Congratulations for putting together technical materials that deliver the essential information, are easy to understand and...I can hardly believe it...are entertaining! Thank you!
- Kathryn
Wednesday, November 3, 2010 at 10:45 PM

Kathryn, Thank you for comment and your interest in our products. Concrete, while truly fascinating to technical junkies, can be terribly boring to everyone else. I try to inject a little humor so that I don’t fall asleep while writing the blog and I don’t lose anyone while they are reading it. By the way I am the same guy that does the videos.
- Bob
Thursday, November 4, 2010 at 1:53 PM

Thank God you had this information!!! I am pouring a concrete floor the day after Thanksgiving...and Mother Nature decided to go ahead with winter and it will be snowing with a high of 35 and low of 20. Crazy weather when just today it was 70!!! Anyway...I will be using hot water, space heater, and blanket as you have advised. At least this is being done in a pre existing block building so the heater should help alot. Thank you so much for the information.
- Beverly
Tuesday, November 23, 2010 at 7:00 PM

Thank You Beverly for your post. We are thrilled to know the blogs are helpful to you. Visit often for new blogs and good luck with your project.
- The Sakrete Team
Monday, November 29, 2010 at 10:36 AM

I have been in the public relations/marketing profession for more than 30 years. I must offer my praise for the down-to-earth style in which you have written your explanations on how and when to use your products. Great job.
- Gregg
Wednesday, December 29, 2010 at 5:41 PM

Yikes! So now what? I helped a friend place poles for a pole shed yesterday. The weather had "warmed" into the upper 30's and our first snow has melted... The concrete we placed in the 3 foot holes warmed some when mixed and seemed to be setting- When the sun set it got suddenly much colder than expected (into the upper 20's)...water froze in the hose, our wives were sure they were freezing too! I covered the new concrete in a vain attempt to retain a bit of heat, but I am sure that the ground froze (and likely the concrete, too). Any ideas about what might now happen to the concrete that we placed? The ground will likely be frozen now till spring- what can we expect after "the thaw"? Thanks
- David
Tuesday, December 6, 2011 at 1:02 PM

David, When the water in a concrete mix freezes it will expand and cause the concrete to crack. After the thaw you can more than likely expect for there to be spalling and the surface could be very weak.
Dean - Tech Service Team
Tuesday, December 6, 2011 at 2:18 PM

I was going throught the codes. BS code specifies that if the temperature of the concrete is more than 30 C then we have to consider the same as hot weather concreteing but as per IS code the temperature mentioned is 40 C. What exactly is write? Can you please explain?
- Rahul Jotshi
Monday, June 4, 2012 at 1:00 AM

When applying concrete the American Concrete Institute (ACI) has standards set for applying in hot and cold weather conditions. These standards are ACI 305 and 306. I can't say whether the BS or IS is correct, they are just two different standards for those different countries.
Dean - Tech Service Team
Tuesday, June 5, 2012 at 5:19 PM

I was planning to pour a two step stairs with out door temperature in the low ninties, but thanks to your advice I'm postponing until the weather cools a little. Your website is appreciated.
- Bill
Monday, July 30, 2012 at 8:06 PM

I live in northern Canada and have poured concrete in warm to hot weather (25 to 34C) and in the colder weather BEFORE the ground freezes (-5 to 5C) and all of your advice in your article is great. It reconfirms what many contractors (and myself) do up here. I've poured many retaining walls and large foundations and in the heat the concrete drys too quickly and in lower temperatures it takes a bit of extra prep work. One additional hint; if you have forms on the concrete (walls, foundations - mainly), keep them on for 3 days (or longer) and use a water misting device (especially on warmer days) to slow the setting process. Thanks the write-up, great job!!
- Gray
Tuesday, September 25, 2012 at 3:09 AM

Hi I poured a concrete footing yesterday and the temp was 5• however the temp dropped after an hr to about -1 when the light went the cemente seems soft this morning should I dig it up re mix with more cement and a frost inhibitor or wait the full 24hrs as its going to get up to 7• today help thank ed.
- Ed uk
Friday, November 30, 2012 at 4:35 AM

Ed, are you referring to Celsius or Fahrenheit? Cold weather will cause the concrete to set up much slower and it is crucial for it to set up before it is exposed to freezing temperatures. Since it is still very early you may want to give it some time to see how it turns out. Also, which concrete mix did you use?
Dean - Tech Service Team
Monday, December 3, 2012 at 5:07 PM

Hi, we build house in Ohio. Concrete contractor poured the concrete footings on 45 F and covered it because next day was raining. today was 25 and he was cleaning the area. it start snowing and temperature stayed the same. can you please tell me if this is ok?
- DS
Thursday, January 31, 2013 at 9:40 PM

DS, when placing concrete in cold weather you want to make sure that it is not exposed to freezing temperatures before the material has set. Concrete will take much longer to set in colder temperatures. It's difficult to say if it is ok, in this scenario there are a lot of variables that could affect the curing of the concrete footing(temperature, rain, snow)
Dean - Tech Service Team
Friday, February 1, 2013 at 3:55 PM

I understand the importance of NOT having the cement freeze while pouring in winter/cold weather. BUT my question is about the ground and frost. I want to do the prep work for sidewalks at the end of March. I will buy the correct cement mix from local company.
- Allan
Sunday, March 3, 2013 at 9:48 AM

Allan, a general rule with placing concrete in cold weather is that any snow, ice or frost must be removed prior to placing the concrete. It is very important to make sure that all surfaces that will be in contact with the fresh concrete cannot cause early freezing of the concrete.
Dean - Tech Service Team
Monday, March 4, 2013 at 8:53 AM

Help, I poured concrete footers for a deck three days ago. the day time temp was warm but it froze in the night. I waited two days for the concrete to set and then placed anchors and bolts in the crete. It seemed wet but i could not wait. You say the concrete will crack, does that mean brake apart? will the weighted of my 10x12 deck crush the footers. . .Im frieked out here!
- Samuel
Friday, March 8, 2013 at 9:25 PM

Samuel, it's difficult to say what the outcome of the poured concrete will be. If the concrete does freeze before it sets the water expands which may cause it to crack, and break apart. Being that it is a structural application you may want to have a design professional take a look at it to ensure it would be able to support a deck.
Dean - Tech Service Team
Wednesday, March 13, 2013 at 4:59 PM

Ok, This weekend I wanted to pour my footers for my deck. 2ft deep by 12" wide. Weather. Friday day high 49degrees, night low of 31, Saturday day high of 51, night low of 33 and Sunday day high of 44, night low of 37, rainy. Will I be safe to pour my concrete footers on Saturday afternoon or should I wait till first weekend in April?
- Brian
Wednesday, March 20, 2013 at 7:08 PM

Brian, it appears that the temperature will be right on the edge of the freezing mark. Just to be safe I'd recommend to wait til there is slightly warmer weather. It would be much better if the concrete footers could be poured when the low temperature will not go below 40.
Dean - Tech Service Team
Friday, March 22, 2013 at 7:28 AM

Bob, Thank you for your post. Worst thing is that I read your post AFTER I poured the concrete. But your post did taught me a lesson for future concrete works. Thank you! Also you have quite a sense of humor.
- TT
Wednesday, July 17, 2013 at 9:35 AM

Sir Please tell if we have concrete under (- 20C) what we should to do? It is a right way to have fire to keep concrete worm and include so accelerator materials in Concrete Mix?
- Asad Khan
Thursday, August 1, 2013 at 1:50 AM

Asad, if you are pouring concrete in -20C temperatures you would have to take the proper precautions to ensure long term concrete durability. In regions where they experience very cold temperatures they often use ground heaters to thaw the ground if it is frozen. Also it is common to use hot water in the mix to accelerate the set time as well as use heating blankets and tents to retain the heat. Set accelerators can be used but keep in mind if the concrete has rebar or metal reinforcement it isn't recommended to use a set accelerator with calcium chloride, it will attack the metal and cause it to rust, eventually cracking the concrete. Also you can follow ACI 306, which is the guide for Cold Weather Concreting.
Dean - Tech Service Team
Thursday, August 1, 2013 at 9:55 AM

We built a house in central oregon and we're planning on pouring a concrete driveway in September, after the weather cools down (it's not uncommon for 90f plus in the summer). My question/concern is: it gets really cold at night starting about mid October. ..if we pour in September, will the concrete have enough time to set properly? If not, when is the best time to pour (in Central Oregon)?
- Candace
Sunday, August 11, 2013 at 2:45 AM

This so called information or an article very useful and i highy appreciate it. Thanks Bob
- Najeebkdean
Sunday, October 6, 2013 at 11:17 AM

I want to resurface my driveway but the data sheet says it cannot get below 50 for 24 hours. You are saying the concrete needs to be set before freezing to be okay. If I am applying on a 60 degree day and the resurfacer only has a 20 minute or so work time, and I am applying at 1/16", does that mean I could still do this? Ardex allows for application in colder temps but I'd rather go with the Top N Bond or Flo Coat if I can find either.
- Toni
Wednesday, October 30, 2013 at 6:40 AM

I am sorry meant to add that the 60 degree day gets into the 40s at night
- Toni
Wednesday, October 30, 2013 at 6:41 AM

Toni, with the Top'n Bond or Flo Coat being that they are polymer modified it is recommended for the temperature to be at least 50F for the first 24 hours.
Dean - Tech Service Team
Wednesday, October 30, 2013 at 4:45 PM

I read there is something in the molecules that makes hot water break down faster and freeze than water that is a normal temperature. It might be a learned myth that using hot water in low temperatures will prevent the effects of freezing. The other one I would not do is add diesel or anti-freeze to concrete. That creates ground contamination, and I can only imagine what other problems that might cause.
- Senior Lotsman
Saturday, November 2, 2013 at 12:19 AM

I am pouring a retaining wall below ground in steel/plywood forms 8ft. tall 33yards total with 1/2" rebar framework inside 1ft. wide walls temp is dropping from 45 deg. to 25 deg. then the next few day above freezing also this is being done through a pump truck, also the mix is 4000psi with waterproof mixture (rheomac 300) and also water reducer-mid range, do you see any problem?????
- stephen
Monday, November 11, 2013 at 6:10 AM

Stephen, I'd recommend to contact the ready mix company to get their recommendation since it is their product. If Sakrete Concrete was going to be used then it would be advised to maintain a temperature of 40F.
Dean - Tech Service Team
Monday, November 11, 2013 at 4:34 PM

I'm scheduled to pour piers this week (Nov 12-16). It's been getting colder outside, but we don't have frost in the ground yet. The holes are going 16' deep (roughly 8' below frost line) and will be reinforced with rebar. Temperatures are staying between +5 and -10 Celcius. Am I ok, so long as I wrap them after pouring?
- Preston
Tuesday, November 12, 2013 at 12:35 AM

Preston, those are definitely some cold temperatures for pouring concrete. You need to make sure that the concrete will not get near freezing temperatures until at least it sets up so if you could somehow keep that area warm that would be ideal.
Dean - Tech Service Team
Tuesday, November 12, 2013 at 12:39 PM

I will be installing a 2 park benches next month (December) in Maryland. Each bench has to poles that get planted about 18 inches in the ground. I was planning to use Sakrete in the holes. It can be cold and below freezing at night. Will I be OK? Thanks, Jackson
- Jackson
Tuesday, November 12, 2013 at 1:53 PM

Jackson, you have to make sure that the concrete doesn't get near freezing temperatures. If it's going to get that cold you should take the proper precautions to make sure the concrete isn't affected. You also have to take into consideration the ground temperature, the ground will continue to get colder this time of year and that can affect the temperature of the mix.
Dean - Tech Service Team
Tuesday, November 12, 2013 at 4:42 PM

I had concrete poured today. The temp at the time of pouring was around 50-55 degrees. I'm now worried after reading about concrete since the temp has dropped to 27 degrees. The temp tomorrow will be close to 60 when they pour a pool deck, but again in the evening should be around 30. The contractor says it should be fine since the ground hasn't frozen yet and the pour temps are in the 50's...should I worry?
- Liam
Wednesday, November 13, 2013 at 10:06 PM

Liam, it all depends on what is done to protect the concrete while it is still fresh, it is recommended to keep it above freezing.
Dean - Tech Service Team
Thursday, November 14, 2013 at 4:20 PM

Thanks for the response Dean!!
- Candace
Friday, November 22, 2013 at 4:54 PM

Hi, I would like to know, this week I need to pour ciment for my balcony and I am worry about the temparature : in the day, it will be -4 and at night, it will be -10. What should I do so the ciment won't crack? An answer will be appreciate as soon as possible. Thank you email address: sandra.rocchini@sympatico.ca
- louis cordeiro
Sunday, November 24, 2013 at 7:15 PM

Louis, those are pretty cold temperatures for concrete work, if you are applying concrete to a balcony you also have to consider the fact that it will be getting cooled from the air below so keeping that area warm may be difficult. I would be very cautious with working with the material since it will be well below freezing the entire time.
Dean - Tech Service Team
Monday, November 25, 2013 at 5:09 PM

Thanks for the advise but I have no choice of doing my balcony since it's all apart. If I use heaters with this help the ciment to dry ??? What the worst thing that could happen ? where are you located ? thanks again Louis
- louis cordeiro
Monday, November 25, 2013 at 8:45 PM

Hi, just had cement "mud job" applied yesterday and today in preparation to apply our thin stone veneer around bottom of my house. Temperatures in the 30-40 degrees faranheight (colder at night). Will this be problematic especially after we apply stone veneer? Thank you.
- Paul
Monday, November 25, 2013 at 11:19 PM

Louis, if you use heaters that will help bring up the temperature of the area being repaired. The worst thing that could happen would be that the concrete cracks.
Dean - Tech Service Team
Tuesday, November 26, 2013 at 2:25 PM

Paul, it's difficult to say, it's one of those things where you will have to wait and see. If the temperature of material and air was below freezing you run the risk of it cracking. I would inspect the mud prior to placing the stone veneer, just to make sure it is solid before setting the stone.
Dean - Tech Service Team
Tuesday, November 26, 2013 at 4:40 PM

Thanks Dean. Spoke to the mason who said he used antifreeze in the mix and assured me that he's done this before as he's been a mason for 15 + years but I'm still concerned. Is using antifreeze normal practice?
- Paul
Wednesday, November 27, 2013 at 2:53 PM

Don't know what happened to !st part of Question!!My contractor is planning to pour a 9 foot retaining wall this week. The temps should be 48 thru 52 day &37-38 nite.We can be as much as 10 degrees warmer day because we are right on water and have south exposure.Please look at end of question above.THANKS!!there is nothing but a gaping hole there now and the house foundation is only abt.12 ft.behind.
- carol
Saturday, November 30, 2013 at 3:47 PM

Paul, it depends on the admixture being used. Many times set accelerators are used and those aren't to be confused with antifreeze, set accelerator simply makes the concrete set faster. You have to be careful though because many accelerators contain calcium chloride and if your concrete has rebar then it will attack the rebar, cause it to rust and crack your concrete.
- Dean
Tuesday, December 3, 2013 at 3:11 PM

Hi Carol, can you provide a little more clarification on your question?
- Dean
Tuesday, December 3, 2013 at 3:18 PM

Thanks again Dean. No rebar as we've applied the mud on the exterior of the home and now plan on applying thin stone veneer (found real stone veneer that is same price as cultured stone). So now that no rebar given project described, do you think we should be ok having used an accelerator?
- Paul
Wednesday, December 4, 2013 at 10:34 PM

Hi Paul, many set acclerators have minimum temperatures that they must be applied in so as long as the directions are followed I dont see an issue with it.
Dean - Tech Service Team
Thursday, December 5, 2013 at 11:27 AM

Hi , my contractor was planning to pour our footings for our house last week but we have been hit by a cold snap. Temperature has been highs of 0 and lows of -5 C for the last 5 days. So he postponed pouring because of frozen ground. The week before was 8 and lows of 5 C . This coming week the temperatures will be getting back to highs of 6 and lows of 2 C. How many days after our freeze should we wait to pour the footings? Can they be poured on the first day when temperatures go above 0 C? Or should they wait for a couple days to make sure the ground is thawed completely? Also the concrete company is a professional company so I would imagine they know what to do. And the city does have to inspect the job afterwards.. thanks again for all the comments.
- Grant
Sunday, December 8, 2013 at 9:55 PM

Grant, it's difficult to say how long you should wait for the ground to thaw, the main thing is that if the ground is freezing then it will bring down the temperature of the fresh concrete mix. This time of year many pros use concrete blankets to keep the material warm enough to pour at those temperatures.
Dean - Tech Service Team
Tuesday, December 10, 2013 at 9:49 AM

Dean... We poured a large driveway 2 days ago and temps were perfect. Daytime was high 70's and night times low 50's. I just looked outside and it is snowing lightly and the temp is 33 degrees. My concern is the surface of this drive. Will it pop when it freezes tonight? Will 6 mil plastic help stop this or do I need to buy an 800 square foot blanket? Not sure if I should even be worrying as the slab has had 48 hours so far to cure some...
- george
Thursday, December 19, 2013 at 12:35 PM

Hi George, I dont think you have anything to worry about. If the slab had 48 hours to cure and the temps were 70 for the high and 50 at night it should be fine. Now if it got well below freezing while being poured and it wasn't protected properly then that's something to worry about. The main thing is for the concrete to set before freezing, which it had plenty of time to do.
Dean - Tech Service Team
Friday, December 20, 2013 at 8:00 AM

Thank you for your help! We just had below grade (48" down) footings poured (not fast acting) for a front porch. Temperature has been and will be in the 40's/50's and maybe moving into the 60s today (F), which sounds ideal (thank God). Should we cover the trenches with a plastic tarp since it will be sunny and might even rain? Also, there seems to be disagreement over when we can start laying the concrete blocks on top. Our contractor said 24 hours but other columns say you need to wait a few days for curing. The footings will support the concrete block walls and a concrete slab on top but nothing else. And another question, the contractor only placed the rebar 2" above the ground and I've read it should be 3". Could this cause a problem?
- Wendy
Saturday, December 21, 2013 at 9:19 AM

And while I am asking, are there similar temperature concerns when laying and filling the concrete blocks?
- Wendy
Sunday, December 22, 2013 at 1:14 PM

Wendy, being that this is a structural application it would be best to contact your local building code official to get their requirement for how long you must wait to build on.
Dean - Tech Service Team
Monday, December 23, 2013 at 1:35 PM

OK, well we ended up waiting longer because it rained. Are there similar temperature concerns with mortar for laying concrete blocks and concrete used to fill the blocks? Thanks and happy holidays!
- Wendy
Tuesday, December 24, 2013 at 7:54 AM

Hi Wendy, yes you still have to take into consideration the temperature when using a mortar or filling the cells of concrete with a concrete/core fill grout material.
Dean - Tech Service Team
Thursday, December 26, 2013 at 10:44 AM

Thanks Dean. Is there a core fill grout product you have that is preferable to your high strength concrete mix? We were going to use the latter.
- Wendy
Thursday, December 26, 2013 at 10:09 PM

It was great talking to you earlier Wendy, as we discussed on the phone when using the Concrete Mix or Sand Mix, being that you have to add more water to get the material to flow into the cells it can weaken the material. The High Strength Concrete Mix will be 4000psi and Sand Mix will be 5000psi when mixed with the amount stated on bag.
Dean - Tech Service Team
Friday, December 27, 2013 at 5:04 PM

Hi i a. Fro. Kashmir where the day temp. Is 9 degree celcious and night te.p. dips to minus 10 degree celcius. I want to pour concrete. What chemical i shoud add for fast set.
- raahi ajaz
Wednesday, January 1, 2014 at 11:28 AM

Raahi, unfortunately we dont offer a chemical additive for such cold applications. You may want to check with a company that specializes in chemical admixtures.
Dean - Tech Service Team
Thursday, January 2, 2014 at 1:48 PM

Last Thursday i poured concrete around two 3 inch pvc pipes 20inches deep and 5 feet tall to use them as sleves for clothes line poles. it was above freezing for 24 hours but the concrete still looks like it has not set completely, still dark grey. i used hot water in the mix and it is now around 30 every night. what do i do and will this make my sleves fail when i put the poles in them? i plan to cut the sleves ground level when i put the poles in.
- Travis
Thursday, January 2, 2014 at 9:31 PM

What about adding a small amount of salt to the water mixture to prevent freezing? For say, 30-40°F ambient temperatures?
- Jon
Saturday, January 4, 2014 at 8:14 AM

We had a 20' x 40' cement slab poured in 60 degree weather yesterday. The temperature got around 30 degrees in the night. Today's high was 39 and now it's 21 degrees with a possible wind chill of -5 to -8 in the night. The contractor covered it with a heavy black plastic looking sheet. He said it would be fine because they added calcium? I'm still worried. Do you think it will crack? And if it does, what is the solution? --- Dana
- Dana
Monday, January 6, 2014 at 12:28 AM

We had a 20' x 40' cement slab poured in 60 degree weather yesterday. The temperature got around 30 degrees in the night. Today's high was 39 and now it's 21 degrees with a possible wind chill of -5 to -8 in the night. The contractor covered it with a heavy black plastic looking sheet. He said it would be fine because they added calcium? I'm still worried. Do you think it will crack? And if it does, what is the solution? --- Dana
- Dana
Monday, January 6, 2014 at 8:54 AM

Travis, which concrete mix was used? And can you tell me how the material was mixed and how much water was added?
Dean - Tech Service Team
Monday, January 6, 2014 at 12:08 PM

Jon, it wouldn't be recommended to add salt to the mix water, you always want to use clean potable water.
Dean - Tech Service Team
Monday, January 6, 2014 at 3:46 PM

Dana, it sounds like they used a set accelerator in the mix which allows it to set much faster than normal concrete. Whether or not it will crack unfortunately is very difficult to say, it's something you'll have to keep an eye on.
Dean - Tech Service Team
Monday, January 6, 2014 at 4:15 PM

Dean I used the basic 80 pound bag with between 3/4 and 1 gallon of hot water mixed very well by hand with a hand trowel to make sure it was mixed well. It was not soupy at all and it set fairly quick but has not yet looked cured. the morning after I poured it there was dew and has been almost every day since. ground around the hole was slightly moist but not wet. was 14 here this morning and have had it covered with a heavy towel with plastic drop cloth on top of that for three days until it got to about 50 each day.
- Travis
Monday, January 6, 2014 at 10:28 PM

Travis, if you could give us a call at 866-SAKRETE that way we can discuss further and see how we can assist you.
Dean - Tech Service Team
Tuesday, January 7, 2014 at 8:49 AM

Doing fence post holes 5" round 36" deep. 80° F some light wind. Mixed 80lb bag in harborfreight mixer with 3.5gal of water like the bag says. Filled bottom half of hole thinking I could shove post into half full holes. I could not. So I used post hole diggers to get the concrete out of the hole and then put the post in and then fill with concrete. Took about 30 min to get concrete out of hole and level and brace post. Question is : Is it possible my concrete got too dry? What happens when concrete is too dry? Should I have added water after digging concrete out of hole and mixed some more? I'm a newb to this. I always just pure bag into hole and add water with hose. But these big heavy post. I want to be done right.
- Brian
Tuesday, February 25, 2014 at 9:19 AM

Brian, I do not feel that your concrete was too dry. I think it was just the order in which you placed your materials. You want to set and level the post first then pour the mixed concete around it. It would be extremely hard to shove a post down into properly mixed concrete.
- RLC - Tech Service Team
Tuesday, February 25, 2014 at 11:04 AM

We are building a new home in Coppell TX. The temp yesterday was around 78* so the foundation was poured. Today the temp is 25* with some sleet rain. Will this affect the the foundation that was poured yesterday????
- Claudia
Sunday, March 2, 2014 at 10:49 AM

We are in arlington tx. Sat it was 80 outside had been 50s for several days i think before, so we set 8 10' fence poles in 30 deep. We finished just about 8pm then Sunday the temp dropped to 30's and then 20's every since. Did the concrete have time to set up ????
- madge
Tuesday, March 4, 2014 at 11:10 AM

Claudia, If this was poured by a ready-mix company you should give then a call with your concerns. Our Sakrete Concrete mix should be used between 40-90 degrees.
- RLC - Tech Service
Tuesday, March 4, 2014 at 4:16 PM

Madge, If your temperatures were above freezing for the first 24 hrs then you should be fine.
- RLC - Tech Service
Tuesday, March 4, 2014 at 4:22 PM

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