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Re: Freezer Slab

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Jim & Jim,

        This was discussed on this list a year or three ago and there were several good postings at that time.  You might check them out.

        Essentially, I believe you do have a frost heave problem.  As usual, fixing it is a lot more difficult than preventing it in the first place would have been.

        The prevention is simple: prevent the sub base material from freezing; OR use a sub base material that is not affected such as gravel that is low on fines and no water table nearby to feed the frost lenses.  Two ways to prevent freezing of the material below the freezer are: provide ventilation; and place waste heat coils UNDER the insulation.  You have a lot of waste heat from the freezer to get rid of; wasting (some of) it under the freezer where it can actually do some good is often a good idea.  Remember, no amount of insulation can stop the frost; it can only slow it down (but sometimes you can slow it down so much that you outlive the onset of the frost problem).

        To fix it you have some options.
1.)  Rip it out and rebuild it. (Probably not the preferred option.)
2.)  Perhaps you can raise it and allow ventilation to reduce the frost over time, then reset it.
3.)  Perhaps you can raise it, set it on beams that span the frozen area.
4.) Maybe you can move it to some other location and thus avoid dealing with the problem (the business man's solution).

        Good luck.

Regards,

H. Daryl Richardson

"Kestner, James W." wrote:

 Jim:I read a report one time that said that it has been observed that some silty soil can draw water up thru capillary action as far as 20 feet away. A freezer building or an ice skating rink that has been in continual operation for a long period of time can have large ice lenses form and heave the floor slab. Ground water can, of course, fluctuate so the fact that there was no ground water in the test pit may or may not have any bearing. It could have been taken during a dry year or a dry season.What kind of soil do you have? What kind of gradation does it have? How much material passes a number 200 sieve?One possible solution is to dig out the ice lense and replace it with non-frost susceptible fill material, insulation and slab. What solution were you thinking of?Jim K.
[Kestner, Jim] -----Original Message-----
From: Jim Persing [mailto:jpersing(--nospam--at)fhoarch.com]
Sent: Monday, July 28, 2003 12:51 PM
To: seaint(--nospam--at)seaint.org
Subject: Freezer Slab
 
I have been asked to make a recommendation for repair of a freezer slab that has risen about 6" from the edge to the middle - 10' +/-.The freezer is kept at about -10 degrees F and has a floor consisting of 4" concrete over 3" rigid insulation over 4" of concrete.  The building is in a mild climate in the Pacific Northwest and is about 10 years old and the original soil report shows no ground water to the bottom of the test pits.  Somewhere water has intruded - broken water line?As far as I can tell (and also from a core through the floor) the cause is from frost heaving.  I have done a little bit of work in Alaska and dealt with frost heaving but this is in reverse.  I think I know what to do but just wondered if anybody has dealt with this problem before and has recommendations on how to fix it.Jim Persing, PE