Freezer Slab on Grade Design Guides/Criteria

[flight7]

Can anyone suggest a design guide or criteria for the design of a slab on grade floor for a large walk-in freezer?

I've been searching ACI, PCA, and online with little luck. I found general principles but not a detailed design guide. For what it's worth, here are some principles that I have found so far:

Without a source of underslab heat, freezing temperatures will penetrate several feet into the soil, even with an insulated slab. The 32°F / 0°C isotherm must be kept within the underslab insulation, or within a granular layer not susceptible to frost heave. Typical underslab heat sources are electrical heating, piped-in outside air, or waste heat from the refrigeration equipment.

I have had no luck finding detailed design values or procedures for any of these things. I have seen freezers in the past detailed with no more than underslab insulation, but I can't find any information to support such a design. Any suggestions?

 

[ajk1]

Have you consulted with a mechanical engineer who has done walk-in freezers?
A geotechincal engineer may also be of help.
I believe Dow Chemical has some published recommendations but I am not in the office right now and so don't have the Dow publications at my fingertips.
Sorry I cannot be of more help.

 

[Splitrings]

ASCE 32-01 Design and Construction of Frost-Protected Shallow Foundations might be useful. It has a section for unheated buildings.

 

[H57]

Are you looking for design of the concrete slab or of the below slab heating system? If you're wondering about the heating system I would talk to the electrical engineer (electric heating) or the refrigeration engineer (glycol system using waste heat from refrigeration system). Either of these systems doesn't really affect the design of the slab as long as you have a system in place to prevent freezing/heaving of the slab.

 

[flight7]

I was hoping to find something that would let me work out the depth of penetration of freezing temperatures. If I can do that (and the depth is not too deep) I can design a subgrade that won't be susceptible to heaving. If that isn't feasible then a heating system will have be be designed by others.

I'll check on ASCE 32 and Dow's website.

 

[ajk1]

In addition to Dow's website,you might call Dow and speak with their engineering department, if you can get past their sales department into thier engineering department...if you are very persistent with them you can get to their engineering department whom I have found to be quite helpful.

I believe, but am not certain, that if the refrigeration is running year round, the frost will penetrate very deep irresepctive of the insulation (the insulation just slows the "rate" of penetration) and heating below will be necessary. That seems to be the case when we design year-round hockey rinks. But again, check with Dow and/or others with experience in this, such as a refrigeratiion contractor who has installed other freezers, the geotechncal engineer, the mechanical engineer are the people we would check with. If you are in the Toronto area, check with Cimco Refrigeration.

 

[BigH]

Check out ice rinks. There have been a number of problems due to freezing of the ground beneath the ice rink. One thing to keep in mind is whether the soil that you are "founding" on is actually frost susceptible; also where is the water table. Say, for instance, you are founding on a clean sand and gravel with even a shallow water table. The sand and gravel are not frost susceptible and the freezing of the water in the voids will have only a minor "swelling" so this may not be detrimental at all. If the water table is "deep" even better. If you have silt, this is highly frost susceptible and any water will migrate up and freeze; ice lensing will be expected and certainly significant heave might occur. Water and Soil Type . . . basis of coming to a rational design.

 

[H57]

I have seen subgrade below freezers freeze to depths of greather than 10 feet with significant heaving (greater than 1 foot). I would not design a freezer without something to heat the subgrade and prevent freezing.