[tim0476]

I have a contractor scheduled to pour a concrete patio for me on Monday. Daytime temp is 49F high nighttime low is 32F. He told me as long as it does not stay below 32F then we are good. I read where anything below 40 is not ideal and I am sure he is not taking any special precautions. Thoughts?

 

[Nealtw]

I have a contractor scheduled to pour a concrete patio for me on Monday. Daytime temp is 49F high nighttime low is 32F. He told me as long as it does not stay below 32F then we are good. I read where anything below 40 is not ideal and I am sure he is not taking any special precautions. Thoughts?

I don't think that is a problem, new concrete gives off heat.

 

[SW Dweller]

Sure you can pour it. If there is a chance that the temp will go below 40F I would be looking for someone to be installing a blanket over the concrete for at least 3 weeks.
Concrete cures it does not dry. If the water in the mix freezes you could be in for trouble.

There are several schools of thought on this. Some say calcium chloride below 50F.
There are other products. All of these products cost money. You might want to call one of your redmix plants and see what they have available for cold weather concrete.

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[LMHmedchem]

I think it would be very reasonable of you to ask for a guarantee in writing that specifically refers to cracks and the cold weather. At least that way if there is an issue then it's clear that it's the contractor's problem and not yours.

If the contractor has allot of experience in your area then they should know the weather and know what to do about it. I hope you picked a contractor who has been around for many years with allot of good work to show off. If they won't guarantee what they are going to do then I would look for someone else to do it. The is no such thing as a guarantee that's not in writing.

LMHmedchem

 

[SW Dweller]

If only concrete worked that way, the guarantee part. I have a couple of contractors that I know well that concrete is their life. One poured my home slab. Even saw cut the slab in sections right after the job was done. (the next day) I do have cracks, around the plumbing penetrations and those run to the outside. My floor is not structural so I did not get bent about it. Even added in fiberglass fibers to make it stronger. I was with the other one when he stopped by a prospective job and the HO asked about cracking in his drive way. He said if I cut the slabs up and into 6 pieces I can give you a guarantee. No no no I want a solid slab. Sorry, I can not do that. It is there work not mine so I do not challenge them.
I am not certain on what has changed with slabs of concrete in this century. For the most part the bigger the slab the sooner it will crack. Maybe they are using less cement, the 2x4's have gotten smaller twice. All of the homes around here are all post tension slabs. Other wise you have to get an enginner to do an earth study for every property and put his name on it. I did as well for my new home because it is not a post or pre tension slab.

When my 30x70 slab was poured I bermed the dirt up and flooded the slab with 3" of water every day for a month. Temps were in the 100's. The slab stayed green for a long time. Still dark in color now that it is inside and a year later.

Freezing is a hard one to predict. I do not see how you can expect the man to be responsible for the weather with out compensation.

 

[SPS-1]

I think you are fine.
The concrete only has a problem if it freezes before it has gained some strength. As mentioned, curing concrete gives off heat. Not positive, but I think the risk factor in your case is only the first night. And you will start off with several tons of concrete at perhaps 45 degrees --- it don't freeze with 1 hour at 31 or 32.
Other than that, cold weather will only slow down the rate of curing. And a slow cure is generally better than hot weather and a fast cure.
Hopefully it rains a lot following the pour.
Ask the contractor for directions on keeping the slab hydrated.

 

[Racinmason]

I think it would be very reasonable of you to ask for a guarantee in writing that specifically refers to cracks and the cold weather. At least that way if there is an issue then it's clear that it's the contractor's problem and not yours.

If the contractor has allot of experience in your area then they should know the weather and know what to do about it. I hope you picked a contractor who has been around for many years with allot of good work to show off. If they won't guarantee what they are going to do then I would look for someone else to do it. The is no such thing as a guarantee that's not in writing.

LMHmedchem

If your contractor gives you a guarantee on the cracks, he isn’t a concrete contractor. The only guarantee with concrete is that it gets hard and it cracks. If the low is 32, you are fine.

 

[LMHmedchem]

If your contractor gives you a guarantee on the cracks, he isn’t a concrete contractor. The only guarantee with concrete is that it gets hard and it cracks.

I guess my point is that a patio is a largely decorative pour of concrete. There isn't much point if it looks like crap a few months after it is installed. If I paid for a patio and it developed large cracks very quickly I wouldn't be very happy about that, especially if I thought the issue was that it was poured with insufficient precautions when it was too cold. Most of you think that it won't be too cold so hopefully that won't be an issue.

It seems like this is the contractors decision to pour the concrete in the expected weather. I would expect some kind of assurance that the final product will look good for a reasonable period of time. What is the point of going to all the trouble and expense of a new patio if that is not the case?

The poster didn't say how large the patio is and if there are planned seams and expansion joints etc. If the contractor knows what they are doing and the size of the poured pads is small enough, then the pads should be free of large cracks for a decent period of time. This assumes that it was adequately dug out with proper base material, well compacted, etc. If this is one large pad and is so large that it cannot be expected to not crack fairly soon, then the contractor should make the owner aware of that and possibly suggest a solution different then poured concrete. If the owner doesn't care about cracks, then why should anyone else.

They really don't do concrete patios around here because of all the frost and the 100+ degree yearly temperate variation. Patios here are relatively small 2" thick paving stones with the seams filled with polysand or nothing. The sidewalks are poured concrete but they don't go larger than 6'x6' for each pour and every 5th pad has an expansion joint. These hold up very well and generally go a decade or longer with no visible cracks, excepting annoyances like tree roots and the narrow spots next to utility poles.

LMHmedchem

 

[jomama45]

Probably too late because it's already Wednesday, but I don't see n issue with the weather forecast. TO be 100% honest, we have had more issues with concrete flatwork poured in the hottest temps in summer than we ever had with the ones poured barely above freezing. In fall, going into winter, it can be dicey, but in spring going into warmer temps, there's far less risk......