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Cold Weather Concrete, Again.

K

Keystone

SAWHORSE
Joined
Feb 23, 2010
Messages
1,297
Location
Lehigh Valley, Pennsylvania
Assumed, cold weather concrete protection, below 40*F, equals blankets or similar approved. Without sources for heat.

Given, ACI 306, 28*F and rising to pour.

Comment, Being ACI calls for the minimum temperature to be 28*F, would it be wrong to interpret the temperature shall remain above 28*F after the pour, say overnight and successive days?

If you believe it’s wrong, why? Can anyone cite a section of ACI that states otherwise?


NOTE, I see ACI offers a commentary on structural concrete but nothing for Cold Weather Concrete.

ACI CODE-318-19(22): Building Code Requirements for Structural Concrete and Commentary (Reapproved 2022)

The “Building Code Requirements for Structural Concrete” (“Code”) provides minimum requirements for the materials, design, and detailing of structural concrete
www.concrete.org
 
Code in Canada requires above freezing for a couple of days. The issue we've had is that makes the assumption that it is minimum code concrete with no admixtures. In reviewing the Canadian Cement Association' book on concreting, if the concrete hits 4 MPA before it freezes, it will recover and continue to gain strength. Not to the original design strength. It will be about 80% lower, but if you over design the mix (which we always see here), there is no issue.

Failure to hit 4 MPA before freezing causes the strength to either stop at that level, or even degrade over time.

Based on testing we've seen, the strength hits 4 MPA with the mixes coming out of the plants before the temperature gets anywhere close to freezing. Of course, we don't see concreting in extreme temperatures, so this could cause some issues.
 
tmurray said:
Failure to hit 4 MPA before freezing causes the strength to either stop at that level, or even degrade over time.
Click to expand...
Down here we use real concrete … measured in thousands of psi … not those goofy numbers.

So i looked it up, found a conversion formula, and now i’m confused. It shows 3000 psi concrete is the same as 20 mpa. So 4 mpa would only be 600 psi. Thats not very strong. Are you saying it only has to get to 600 psi before freezing?
 
mtlogcabin said:
That is what you would have to assume if you are not there to see the tickets
Click to expand...
I would if the plants sold it, but they won't for liability reasons.

well, they probably would for something like a slab pour in a heated building, but that again is a different mix altogether.
 
e hilton said:
Down here we use real concrete … measured in thousands of psi … not those goofy numbers.

So i looked it up, found a conversion formula, and now i’m confused. It shows 3000 psi concrete is the same as 20 mpa. So 4 mpa would only be 600 psi. Thats not very strong. Are you saying it only has to get to 600 psi before freezing?
Click to expand...
You folks are the only ones.

Yeah. Once it unfreezes it will continue to cure and increase in strength.
 
While atmospheric temperature is important what really matters is the temperature of the concrete. Insulated forms can make a big difference. Also installing a tent over the concrete work and heating it has been done.

Engineers concerned about cold weather will be guided by ACI standards.

The question is what the building official can require regards cold weather concreting.? Be prepared to reference code section.
 
tmurray said:
Code in Canada requires above freezing for a couple of days. The issue we've had is that makes the assumption that it is minimum code concrete with no admixtures. In reviewing the Canadian Cement Association' book on concreting, if the concrete hits 4 MPA before it freezes, it will recover and continue to gain strength. Not to the original design strength. It will be about 80% lower, but if you over design the mix (which we always see here), there is no issue.

Failure to hit 4 MPA before freezing causes the strength to either stop at that level, or even degrade over time.

Based on testing we've seen, the strength hits 4 MPA with the mixes coming out of the plants before the temperature gets anywhere close to freezing. Of course, we don't see concreting in extreme temperatures, so this could cause some issues.
Click to expand...
I think the Canadian Cement Association is being very optimistic, if the concrete freezes at 4MPA it will recover and gain strength.. I agree but I’d have to assume not optimal design strength. Either way it’s not your conclusion it’s the Canadian Concrete Association.

I suddenly find myself in agreement with the Canadian Cement Association after this post original post is now being edited to include this information, little continued research. Concrete Network indicates a 500psi or what approx 3.5MPA+/-

Cold Weather Concreting - Winter Concrete Mix - Concrete Network

Two main problems with pouring concrete in cold weather: It can freeze, and it sets more slowly when cold. Plus, tips for changing concrete mix during cold weather.
www.concretenetwork.com
 
Last edited:
Mark K said:
While atmospheric temperature is important what really matters is the temperature of the concrete. Insulated forms can make a big difference. Also installing a tent over the concrete work and heating it has been done.

Engineers concerned about cold weather will be guided by ACI standards.

The question is what the building official can require regards cold weather concreting.? Be prepared to reference code section.
Click to expand...
for one...

1901.2 Plain and reinforced concrete. Structural concrete
shall be designed and constructed in accordance with the
requirements of this chapter and ACI 318 as amended in Section
1905 of this code.

Maybe ACI 5.11 ish...I cant afford the book....

ACI-318
5.11 — Curing
5.11.1 — Concrete (other than high-early-strength)
shall be maintained above 50 F and in a moist condition
for at least the first 7 days after placement, except
when cured in accordance with 5.11.3.
5.11.2 — High-early-strength concrete shall be maintained
above 50 F and in a moist condition for at least
the first 3 days, except when cured in accordance with 5.11.3.
 
I don't believe that IBC Chapter 19 adds anything other than reference ACI 318.

II believe the ACI reference is to an earlier version. For ACI 318-14 the sections are 26.5.3 and 26.5.4 and they are essentially unchanged. This raises the questions: How many building departments have a latest copy of all of the reference standards listed in the IBC and the other codes as well as the standards referenced from the reference standards. These documents are a part of the code.

Cold weather and curing requirements are typically located in the project specifications. In my experience many plan checkers do not look at the project specifications.

While ACI 306 is a useful document it is a report and not a standard. Further I cannot find where it or ACI 306.1 is formally incorporated into the standard as opposed to being referenced in the commentary. Thus it is not enforceable. What the building official can do is to make use of ACI 318 Section 26.5.3.2(d) and require field cured concrete cylinders.
 
Mark K said:
While atmospheric temperature is important what really matters is the temperature of the concrete. Insulated forms can make a big difference. Also installing a tent over the concrete work and heating it has been done.

Engineers concerned about cold weather will be guided by ACI standards.

The question is what the building official can require regards cold weather concreting.? Be prepared to reference code section.
Click to expand...
To your point, our code is written so that when temperature is below 5C, the concrete temperature must be maintained at 10C for 72 hours. It says nothing of the measures that the contractor needs to take, just the end objective.
 
Keystone said:
I think the Canadian Cement Association is being very optimistic, if the concrete freezes at 4MPA it will recover and gain strength.. I agree but I’d have to assume not optimal design strength. Either way it’s not your conclusion it’s the Canadian Concrete Association.

I suddenly find myself in agreement with the Canadian Cement Association after this post original post is now being edited to include this information, little continued research. Concrete Network indicates a 500psi or what approx 3.5MPA+/-

Cold Weather Concreting - Winter Concrete Mix - Concrete Network

Two main problems with pouring concrete in cold weather: It can freeze, and it sets more slowly when cold. Plus, tips for changing concrete mix during cold weather.
www.concretenetwork.com
Click to expand...
Oh, I see. Don't believe us Canadians, but as soon as an American says it, it must be true. You're just prejudice against us Canadians.

No, I'm just joking. Sarcasm doesn't translate real well on a forum.

I'm glad to see the consistency to help reinforce our position.
 
tmurray said:
Oh, I see. Don't believe us Canadians, but as soon as an American says it, it must be true. You're just prejudice against us Canadians.

No, I'm just joking. Sarcasm doesn't translate real well on a forum.

I'm glad to see the consistency to help reinforce our position.
Click to expand...
Yeah I knew that wasn’t coming off the best, but then I thought. What do I care, I am American and Americans are always correct. Even when we are the only country to use our own measurement system
 
I for one don't have time to keep track of all of the jobs and temperatures. In my opinion that is up to the contractor/RDP/project manager. We have poured in the cold & used many different methods but with out knowing what's in the mix we are just guessing. I inspect the forms and rebar not the actual pouring of the concrete.
 
When special inspections are required the inspector should be checking the temperature.
 
my250r11 said:
I inspect the forms and rebar not the actual pouring of the concrete.
Click to expand...
If the contractor does a proper job, there is a testing company on site taking test cylinders that should be left to cure with the slab. When they are broken it will be obvious if the temperature was too cold.
 
It would appear that there is a problem with the special inspectors.

Hiring the special inspectors is the responsibility of the owner and unless the engineer of record voluntarily takes on that duty the engineer of record is not responsible for performing special inspections.

Is the building department aware of these practices?
 
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