pouring concrete in November.. Question

[vortech91]

I'm hoping to have my pole barn concrete floor poured in the next week or two. The barn is complete with metal roof, and walls. It does have two insulated garage doors installed. My question is

1. Should I still get this concrete poured with the cold weather we are having in Michigan already?

2. The concrete guy made no remarks of heated blankets or covering slab for cold weather protection. Should I run kerosene heater in the barn in an attempt to keep the slab from getting too cold?

3. the concrete guy said I will be fine and he will add an additive to the concrete if the temps are going to be low.

Its 2000 sq/ft of concrete and I don't want to have problems down the road.

I have no insulation and no ceiling. Vented soffits and ridge vent. So I'm unsure how the barn can hold much heat

Thanks

 

[3rdgendslmech]

Unless the temps are gonna drop way below freezing and stay there you should be fine. I poured mine in June and was told to let it cure 48 hrs before you put a car on it. You might want to wait 4 days.

 

[RPH]

Concrete curing is a heat generating process. Unless it gets extremely cold for a long period no harm done. Actually it makes for ideal conditions as it won’t set up to quickly. It allows the crew time to work it properly.

 

[GMCGarage]

Freezing concrete is a disaster.

In a nutshell, from ACI (American Concrete Institute) you should protect your concrete if “a period when for more than three successive days the average daily air temperature drops below 40 degrees Fahrenheit and stays below 50 degrees Fahrenheit for more than one-half of any 24 hour period.”

You have a windbreak, so that is good. There are no additives to prevent concrete from freezing, Calcium Chloride or other additives can be added to accelerate the cure. Actually you should make sure Calcium Chloride is not used, but some other accelerators.

What are your temps going to be for the 3 days after pour?

 

[ConCretin]

I included a short section on cold weather concrete in my Guide to Floor Slabs you can access below. With regard to your specific questions;

1. Should I still get this concrete poured with the cold weather we are having in Michigan already?

We place concrete up here in Maine year round. Until air temps get below freezing, you don't have much to worry about other than lights because it's going to take a while to finish. Below freezing is another matter. It's doable but you need to know what you are doing.

2. The concrete guy made no remarks of heated blankets or covering slab for cold weather protection. Should I run kerosene heater in the barn in an attempt to keep the slab from getting too cold?

You definitely don't want too run an unvented heater. The carbon dioxide released by the heater can damage the surface of the concrete. Insulated blankets that retail the heat of hydration are probably adequate unless you have temps well below freezing.

3. the concrete guy said I will be fine and he will add an additive to the concrete if the temps are going to be low?

As was mentioned, you can add accelerating admixtures to the concrete. it will create more heat and decrease the time it takes to get the concrete finished.

Calcium is often used but can theoretically cause corrosion of reinforcing steel. A non chloride accelerator is a reasonable alternative.


In general, you're less likely to have problems placing in colder temps than hot temps and will end up with a better quality slab i.e. less cracking and a more durable surface. Hope that helps. If you provide more info on your expected temps, we can provide more info. Good luck

 

[vortech91]

I don't have a set date to pour, but what temps would you guys consider to be too low. Its averaging 40-50 day time highs and above freezing nights, but night time lows look to be hitting the freezing point very soon.

Why not add calcium chloride?

Thanks

 

[GMCGarage]

I don't have a set date to pour, but what temps would you guys consider to be too low. Its averaging 40-50 day time highs and above freezing nights, but night time lows look to be hitting the freezing point very soon.

Why not add calcium chloride?

Thanks

Well based on ACI, you could be under 50 degrees for 12 hours or more. If hitting freezing temps at night possibly, do you want to risk having your concrete freeze? Even some surface freezing could cause localized spalling or crazing in the concrete.

Calcium Chloride is bad for steel in the concrete. If over used, the chlorides can reside, and effect the PH of the concrete and that effects the steel.

If un-reienforced, you should be ok.

Run your heater, spend the money to protect your investment.

 

[hammerhead611]

I don't have a set date to pour, but what temps would you guys consider to be too low. Its averaging 40-50 day time highs and above freezing nights, but night time lows look to be hitting the freezing point very soon.

Why not add calcium chloride?

Thanks

From the post right above yours...

Calcium is often used but can theoretically cause corrosion of reinforcing steel. A non chloride accelerator is a reasonable alternative.

 

[GMCGarage]

From the post right above yours...

Me thinks he didnt see that post, posted about the same time. I didnt see it until I post my last reply.

 

[ConCretin]

I don't have a set date to pour, but what temps would you guys consider to be too low. Its averaging 40-50 day time highs and above freezing nights, but night time lows look to be hitting the freezing point very soon.

There are two parts to this decision; the first is the time required to get a finish on the concrete and the second is your ability to protect the concrete from freezing until it gains adequate strength.

Finish time increases significantly when the concrete temp drops below 50. The concrete should arrive at 70 degrees or more but will cool rapidly when it hits the cold ground. This is why it helps if you place on insulation or if you are able to warm up the ground beforehand. (obviously frozen ground is a non starter) Placing in the sunshine also helps considerably.

We regularly push the envelope but I wouldn't suggest placing if the temps are projected to drop much below freezing before early evening. To pick some safe numbers, lets say daytime highs near 50 and at least 30 degrees at 10 pm. I'd strongly suggest a minimum of 2% accelerating admixture. This should provide you time to get a decent finish and get it covered.

If temps are projected to drop below freezing in the first 48 hours or so, you'll want to protect the finished slab. Insulated concrete blankets are ideal but poly covered with a thin layer of hay will work too. Remember the concrete and accelerator will generate the heat - you just need to hold it in. Either method will protect the concrete to temps well below freezing. If we are going to pick a number, let's say a low of 25 degrees for 48 hours after placement.

Ideally you are trying to maintain the slab at 55 degrees for 48 hours. You can use a simple probe type thermometer in a drilled hole if you want to check. Don't panic if the temps are below 55. As long as the concrete doesn't actually freeze before it reaches 500 psi, it will be fine. It will just set slower so you'll want to leave your protection in place longer.

 

[6768rogues]

If the ground is frozen, wait.
When I was inspecting for a living, down to 25 degrees was ok with regular air entrained concrete. That was the overnight low for a few hours, not the daily average. Often the contractor wanted to add one percent accelerator or they would have to wait too long to get on it. Ok.
If it is a little colder, two percent accelerator can be used. Not more than that.
If it gets down in the very low 20s or the teens, do something like covering it with blankets or closing the building to protect it and keep it warm if the colder temps are only short term overnight.
Concrete makes heat during the hydration process, so it keeps itself warm. If it is cold, accelerator will make the hydration process speed up, making its heat speed up. There is a point where it is too cold even with accelerator without covering the concrete or doing something to protect it. In our area, that is considered to be around the 20 degree mark as a low point, not the average daily temp.
If it freezes, hydration stops and later it falls apart.

 

[matt_i]

3% calcium chloride has been used since man started pouring concrete. I would ask about a non chloride accelerator but if you can't get it, not to worry. I would give the mix yard a couple of days to get that if they don't have it on-hand. Sooo much concrete is poured with CaCl2. My take is that the damage to reinforcing is minimal.

I had some similar concerns, pouring my floor right around 11/01 a couple of years back. All went well, the guy I used said he wasn't worried until he saw an overnight low of 28F or lower predicted.

Definitely agree that the concrete will generate its own heat due to the chemical reaction. Its just a matter of keeping it in. The straw is a pretty good idea for something temporary to cover 2000sqft.

I would also make sure you have a clear understanding with your concrete contractor that the control joints are to be cut the next morning after the pour. Snap lines on 10-12 foot squares.

I used a curing sealant that went on the same evening of the pour, just as the sun was setting, I could walk around with sock feet and not damage anything. It looked like a black ice skating rink for awhile. Great stuff!

I'm still quite happy with the job under foot traffic and some light forklift traffic. The big dogs (big machines, heavy forklift) haven't rolled in yet, but will soon.

 

[b-boy]

Mine was poured 2 years ago in early January. It was pretty cold.

The contractor was supposed to do it a few weeks earlier, when we had temps in the 40s, but blew me off. He had hot water added to the concrete mix, covered it in plastic, sealed the entire pole barn in plastic, and ran several torpedo heaters for a few days until it cured. He came back in the Spring to do the external pads. I haven't had any problems.

He tried to charge me $450 for the kerosene he used to heat the building, but I wouldn't pay it. If he'd have been there on time, the heaters wouldn't have been needed. We made a deal - I paid him in cash, and he ate the cost of the kerosene.

 

[pcmeiners]

"The straw is a pretty good idea for something temporary to cover 2000sqft"
That good if you have plastic below it, otherwise straw will stain the concrete. Definitely use plastic. Not only does it slow heat loss but just as important it maintains the water within the concrete so it cures properly.

 

[77Birdman]

llwillysfan is correct. We pour in MD year round also, though Im sure ME gets much colder weather. Its not ideal but can be done. Around my parts one can rent concrete blankets, you might want to check with some industrial rental companies in your town. Give plenty of advance notice though as they get in demand when temps go down. Simply laying down 6 mil poly over the finished slab will help. The concrete will give off heat and the plastic will keep it in. I would imagine in MI they use a winter mix for the concrete as well.