Cold Weather Concrete Problems w/Contractor

[Berniedog]

Need advice on what to tell the Architect. Contractor poured foundations for High School Bleachers. He was told to place insulated blankets on the footings and around piers. He did not do this but used a little straw instead. Over the weekend, the temperature got down to 20 degrees at night (Northern Ohio). What kind of tests can be performed to determine if the concrete was damaged.

Any other advice?

 

[nuche1973]

ACI has guidelines on the requirements for cold weather. It depends on if it was cold enough for the water within the concrete to freeze and stop the hydration of the paste. 20 deg (assuming F and not C) is not cold enough to stop the rate of hydration in the concrete (also assuming there was not additives). However, if you are concerned about the strength, take a 4" core out of the footing and break it. Remeber to maintain a 2:1 length to diameter ratio for your sample.

 

[BAretired]

The contractor should cover the work with insulated blankets immediately if the temperature continues below freezing. Here is a link to a similar question:

http://www.eng-tips.com/viewthread.cfm?qid=55469&page=10

BA

 

[concretemasonry]

The key is the temperature of the concrete and not the air temperature that you get on the late news or the Weather Channel.

If the concrete cooled, the reactivity and heat of hydration was reduced until the the concrete temperature increases. In general, freezing of concrete is not detrimental if the surface freezes while not fully saturated.

What was the temperature of the base (not air temperature) prior to the placement and what was the concrete temperature? Type I or Type III Portland cement?

Dick

Engineer and international traveler interested in construction techniques, problems and proper design.

 

[dik]

Let the Architect know that it is outside specification and let him deal with it...

At -7degC, it's marginal... less so, if it was covered with a layer of straw... depends on how thick. It is possible that the matrix froze and then it depends when... if during the hydration process, it can weaken the concrete surface. If before, then with the heat of hydration, during the warmer day, it will start to hydrate normally.

Taking cylinders will not likely tell you much. The only way, if there is a concern is to undertake a petrographic study to examine the matrix on a microscopic level. If it is a footing and if you lose 1/2" of thickness, is there a problem? If not, then you might consider burying the 'body'.

Dik

 

[Ron]

Agree with dik...do a petrographic examination.

 

[vandede427]

petrographic examination might cost just as much as demo and replacement.

 

[dik]

If there's a concern or if the loss of material is critical... but this is the only way for checking... and this may not tell you if the concrete has been compromised.

Dik

 

[Berniedog]

Thanks. The Architect has hired a testing company to come out and do some strength tests. It probably is not practical to do a pertographic test ($1000.00) since there are so many footings. Some may have to come out.