Need recomendations for cold temp concrete pour

[toolnut]

Looking to get this floor finished before winter... and lately it's been getting below freezing at night here, with daytime highs in the 40s. Getting different opinions if calcium ad is needed, and I wondered what the pluses / minuses of using the add might be? The guy I would like to use is recommending it strongly, and claims that with only a "2%" mixture it won't affect the strengh, but I have little experience in this area. I'm thinking that with the base still warm and air temps in the 40's...maybe I would be OK without it? As you can see from the pic, no rebar, only using a light mesh, the floor is 21 by 32 (averages about 4.5 inches think, upto 5 in a few places)

Alternative is to wait till spring... but I sure would like to get this done..

All opinions appreciated.

-Toolnut

 

[SPIKER]

I see you are putting radiant tube in there, that is good thinking, one thing make sure you take some accurate measurements near all walls and posts so that if you ever want to anchor anything along a wall/post that you can refer back to the measurements (on a photo works great I found using my digital camera marking locations and laying the tape out and taking a pic you can easily count the major foot marks and also then the 1" ticks just in case! I see you had a tape in you're pic above so maybe you are already doing that ? anyhow just wanted to say that so that later you could keep that info around store them on the web (photo bucket lets you store stuff for ever free as does many other pic sites! I had a bunch of my place and still do only they are in a hard drive that can't be accessed anymore due to a bad virus that wiped out the FATs so back up those important pics on-line and disk & 2nd storage media if possible..
sorry no help on the calcium but heard that 2% up to 5% is ok in most cases
mark

 

[Tig]

Freezing can ruin fresh concrete. I just poured a 26' x 36' garage floor last month, 2% calcium. I also covered it with a tarp that week to protect against frost.
You may want request fibreglass in the mix. It doesn't add much to the cost.
What is your slab going to used for?

 

[Egon]

If that slab is in a building make your pour and blow some heat into the building.

If you really want some high early check with the concrete supplier on final strengths etc. You can also get stronger concrete.

If its cold the contractor has to hang around forever waiting to be able to do the finish troweling.

 

[Tig]

On my slab, I think the third truck was a little late remembering to add calcium. 8 hours later at 11:00PM that area still had not set. The temp outside had dropped to 0 C so I had the finisher hand trowel it and we put a simple tarp over the slab. In the morning it was -2 C but under the tarp it was 12 C.

 

[ToadHill]

Talk to your concrete supplier, I used to pour with my dad down to about 25 degrees. The supplier used to add more than calcium, but I don't remember what else was in the mix.

 

[Lynkage]

I would not add calcium I would put concrete blankets down during the hottest part of the day over the ground a few days before you pour. Then if your pour day is above 32 deg. and will not get any lower cover with plastic.
If it will get lower then use plastic first then put your concrete blankets over that. The plastic will help keep all the moisture in the concrete and it makes it much harder. Leave it that way for 5-7 days. Just let the concrete cure about 4-5 hours after you pour before doing these things.

 

[MossRoad]

All opinions appreciated.

-Toolnut

Well, since you said it...

My father was an architect and a construction specifications writer for many years before he passed away. He had lots of knowledge on concrete, as he did lots of projects with it poured on site and pre-cast. He told me to never, ever let someone talk me into pouring concrete if the potential for freezing was near. No matter what they say it won't be as nice as a pour done above freezing.

He would wait until spring unless it is absolutely necessary to have it done now. It is supposed to get very cold here in Indiana over the next week and you are east of us and get our weather soon after.

Make sure your concrete contractor has the knowledge to do it properly if you choose to proceed.

That's just my opinion based on my father's advice. I have zero first hand knowledge of concrete other than if it is done wrong, it is going to stay wrong for a long, long time.

Best of luck on your project.

 

[toolnut]

Roger on taking the pics, I really should take a few more. Someday I'm hoping to put in a two post car lift, that's why the funny loop pattern in the center. Also will be using for to store my welding stuff, tractor goes in the unfinished section next door....

I asked the contractor today again about the downside of adding calcium, he seemed pretty confident that it wouldn't affect the future durability much, said he was using it he pours his own garage floor next week. I think it is partly to speed things up for him, but it has been getting down to 25 degrees or so here at night so I think I'm just going to let him use it.

Thanks for the all the comments, I'll have to ask him about bringing some tarps.

BTW, you'll notice no insulation under the slab... I decided that I just use re-claimed styroform (4" worth) all around the outside parimeter and skip the expense of new denser insulation directly under the slab. This will give a lot more thermal mass, (so it probobly days to heat up...) but should also carry through longer when not getting new heat. Hoping to warm it using solar collectors.. but that's another thread.. for next year.

-toolnut

 

[Mundy]

Toolnut,
I am new to this forum but have been building roads and bridges for one of the largest County Road Commissions in Michigan for the last 12 years.
I would strongly recommend against the chloride.
When I started out we used to put chloride in everything but bridge decks if it was colder than 40. Just in the 12 years I have been doing it I have watched many (not all) of the repairs and new builds that we have done with chloride spall and age much quicker than they should. Re-steel even epoxy coated rusts much faster when we add chloride. I would be worried about your water tubing.
For about ten years we have been using a D.O.T. approved NON-Chloride Accelerator. We also cover the pour with insulating blankets or straw with tarps. Your residential concrete contractor may or may not know what Non-Chloride is or may even tell you it is the same thing but the concrete supplier will know what it is and should have it.
Just remember your contractor is down the road when you have a poured floor and are still happy the following spring. 10 years or 30years are the same to him. The concrete will get hard and last many years with the chloride.
What I have seen over the years is that many of the concrete pours my department has done with chloride 10 to 15 years ago are falling apart and the steel is rusted away. In contrast the cold weather pours that have been done in the last ten years with the Non-chloride Accelerator are ageing as they would be expected.
It is more expensive than chloride but I feel a large pour with heat tubing and hope of installing a lift is a long term investment and I would want to do everything to make it last as long as possible....

Just my 2cents.

Either way the concrete needs to be protected from cold for at least 24 hours. Be carefull blowing heat in without plastic or tarp ontop of the concrete. This could dry the surface rather than cure it.
I just feel it will last longer with a Non-Chloride Accelerator or go no additive but HE grade cement.

Regards,
Mundy

 

[dqdave1]

In my opinion, You need some type of insulation on bottom of slab. I would think the "ground" will absorb all the heat and cause you a high energy bill.

 

[Lynkage]

Mundy has said just about what I have said. I guess I am just old school and prefer no additives. This is what I do for a living as well and it does seem that the additives age the concrete faster. I also do a lot of stamped and colored and heated as well. If you need it to cure quicker then go with a higher psi mix.(that is what Mundy said as well) If you use say a 6000psi mix or what some call a 6 sack mix it will cure quicker because it gets hotter faster. Concrete is a chemical reaction and instead of fighting it work within it's specs.

Also I would check with your contractor to see what mix he has planed on using as I would never pour less than a 4500 psi mix for your situation anyway. But then again I do not pour less than 4000 psi ever.

These are just my opinions and experiences.

 

[MossRoad]

Toolnut,
I am new to this forum but have been building roads and bridges for one of the largest County Road Commissions in Michigan for the last 12 years.
I would strongly recommend against the chloride.
When I started out we used to put chloride in everything but bridge decks if it was colder than 40. Just in the 12 years I have been doing it I have watched many (not all) of the repairs and new builds that we have done with chloride spall and age much quicker than they should. Re-steel even epoxy coated rusts much faster when we add chloride. I would be worried about your water tubing.
For about ten years we have been using a D.O.T. approved NON-Chloride Accelerator. We also cover the pour with insulating blankets or straw with tarps. Your residential concrete contractor may or may not know what Non-Chloride is or may even tell you it is the same thing but the concrete supplier will know what it is and should have it.
Just remember your contractor is down the road when you have a poured floor and are still happy the following spring. 10 years or 30years are the same to him. The concrete will get hard and last many years with the chloride.
What I have seen over the years is that many of the concrete pours my department has done with chloride 10 to 15 years ago are falling apart and the steel is rusted away. In contrast the cold weather pours that have been done in the last ten years with the Non-chloride Accelerator are ageing as they would be expected.
It is more expensive than chloride but I feel a large pour with heat tubing and hope of installing a lift is a long term investment and I would want to do everything to make it last as long as possible....

Just my 2cents.

Either way the concrete needs to be protected from cold for at least 24 hours. Be carefull blowing heat in without plastic or tarp ontop of the concrete. This could dry the surface rather than cure it.
I just feel it will last longer with a Non-Chloride Accelerator or go no additive but HE grade cement.

Regards,
Mundy

Mundy,
Welcome to TBN!

 

[toolnut]

Thanks a lot guys... I'm rethinking the calcium cloride add, I may just wait till spring if I can't find someone willing to do it without! One contractor said he bring in a couple of torpodo heaters... but as someone referenced, I've heard those can cause problems as well, something to do with CO2 emission.

thanks again,
-toolnut

 

[Egon]

There has been many a yard of concrete poured in cold climates using Torpedo heaters to keep the building warm. You could also get the supplier to use hot water in the mix to give some extra help.

 

[rural2]

Is the contractor going to guarantee (including demo if things go bad) in writing? Is he willing to wait 14 days for payment? That will tell you a lot right there.
Your main objective is to get the mud to set up enough to work it. Then the objective is to keep it warm enough to continue to cure without freezing. However, don't hesitate to cancel the pour if things look bad. Guarantee or not!
Like has already been said... C.C. is probably not the way to go. Call the batch plant for what cold weather design mixes are available and what they recommend. Hot water is a good suggestion, however ask the batch plant. I have seen some weird stuff with hot water and "dope" combined. Talk it over w/the contractor.
Come to think of it, your contractor should already know all this... Maybe you need a new mud rubber?
Good luck

 

[Mundy]

Thanks for the welcome.

As Egon said the heaters would work well. But remember you must have plastic or tarps down to keep the surface from drying.
We blow heat all night long on a winter bridge deck pour, we will insulate from the bottom and tent the top. Then several of the biggest salomander type heaters I have ever seen are fired up. But we also place wet burlap over the finished surface and someone is posted all night to keep the burlap wet.

With the sheet metal on the walls and the door almost closed you could blow heat through the almost closed door from a salomander and that building would stay nice and toasty. I would cover the pour with plastic and point the heater up toward the ceiling and you would be fine.

If your finisher is worried about set time and Non-Chliride Accelerator is sounding too complicated then as Lynkage said HE (High Early) or 6 sack mix should do the trick with no ill effects and may even increase the strength depending on the aggregate. This time of year Hot mix water should be standard at the plant.

I think you could get a great pour this time of year as long as you take a few precautions. It sounds like you are doing your homework and if you have to wait til spring then so be it.

Just remember 1) do not pour on frost 2) do not add chloride. 3) cover after its set. 4) protect it from the cold with insulation or suplemental heat. You'll do fine.

Regards,
Mundy

 

[Egon]

Surely sounds like proper advice Mundy!