Need Concrete Knowledge

[Wayne County Hose]

I have decided to stick build my new home. Unfortunately, the weather here in the northeast is typical January. My old basement was 6'. I want to add 18" of concrete to the top of the existing foundation. I don't want to go any higher as the house will stick up out of the ground way too much. 18" is really too much. Anyway, I am concerned about having concrete poured in sub-freezing temps. I am told that the additive used to keep it from freezing weakens it. The existing foundation is 4500lb. concrete. I know it would probably be okay to pour it anyway, but I would rather have both pours the same strength. Does anyone out there have concrete knowledge on this? Pun intended by the way. Thanks for any help, Andy.

 

[tommu56]

What about 3 - 4 courses of block added to existing foundation?

tom

 

[SpringHollow]

Your concrete supplier can make the concrete to the strength you need as well as having the correct freeze protection. They have to do this for commercial construction all of the time, often with higher rated concrete than what you need.

Ken

 

[Egon]

It all depends on the outside temperature. High early concrete is only good for limited freezing. Hoarding and heat may be needed.

 

[EddieWalker]

I'd go with block. Drill holes in the top of the existing wall for half inch rebar and epoxy them in place. Morter the block into place and cross the tops of the second to top row of blocks with rebar that you tie together with the vertical rebar in your wall. Fill the cavities with concrete.

Trying to pour a concrete wall on top of an existing wall is more complicated then I'd be willing to try. I would also be very hesitant about hiring it out as it's not a common job and you'll be lucky to find somebody who actually knowos what they are doing. If it's wrong, your entire house will move.

Eddie

 

[rimshot]

There is no question about it. Pour concrete if you only if you absolutely have to in sub freezing temps but you will get 1/2 the workmanship and it will cost you twice as much. Once poured cover it all as best you can even if it means using styrofoam, tent it and keep heat on it until weather returns to above freezing as long as you can otherwise. make sure you add not more than a 2% chloride to your batch as it will speed up hydration of concrete. If you can lay blocks as opposed to forming/pouring that might not be as bad. Make double sure you don't pour over any frozen soil. If you use mortar see to it you use a frost preventer like a liquid additive to water and use hot water and sand can be heated as well. Remember also there is a downside to using chloride as you know what happens when chloride and any steel reinforcing come together.

rim

 

[crbr]

I have decided to stick build my new home. Unfortunately, the weather here in the northeast is typical January. My old basement was 6'. I want to add 18" of concrete to the top of the existing foundation. I don't want to go any higher as the house will stick up out of the ground way too much. 18" is really too much. Anyway, I am concerned about having concrete poured in sub-freezing temps. I am told that the additive used to keep it from freezing weakens it. The existing foundation is 4500lb. concrete. I know it would probably be okay to pour it anyway, but I would rather have both pours the same strength. Does anyone out there have concrete knowledge on this? Pun intended by the way. Thanks for any help, Andy.

Wait for better temps.

 

[Egon]

[QUOTEWait for better temps.][/QUOTE]

Now that is good advice.


Long small pour sections do not generate much heat when curing and are difficult to hoard.

 

[Wayne County Hose]

Waiting for better temps is not an option. I have spoken to some builders and they tell me do not use heaters and enclose. Heaters remove oxygen from the air and the concrete won't cure properly. I'm also told that pouring on top is okay. The contractor is boring holes into the existing foundation and adding rebar into those holes. He is also placing the forms along the existing foundation.

Eddie, I like your idea. Is this something you have done? I didn't want to go with block, but the job is not started yet.

The contractor is very respected in the area. He poured the original foundation 15 years ago. The engineer that came to inspect it after our house fire told me that whoever did our foundation did an exceptional job, and he was very adamant about it. So, I do trust that if he pours it, all will be okay. My main concern is pouring in cold temps.

Ken, that's kind of what I'm hearing. I had a customer in today that used to work for a cement company. He told me that they don't use calcium anymore. He said they use something else that also speeds the curing time.

Thanks for all your inputs, Andy.

 

[Egon]

I'm afraid your contractor is not familiar with pouring concrete in cold weather. Maybe cool weather but serious cold is a different animal. Adding heat is the only way to go. There are different ways to do this.