Frost Heave 1

[GPSSA]

Hi,

Wondering if someone could offer some advice!?

I am working on a project to convert an existing buidling into a freezer store to operate at -25 deg C/ -13 deg F.

The floor of the original building was not designed to prevent frost heave.

What measures can be taken to prevent frost heave on this existing floor slab??

thanks

 

[ACtrafficengr]

There are three things that are needed to cause frost heave:

[ol]
[li]sub-freezing tempuratures[/li]
[li]frost-susceptable soils[/li]
[li]water[/li]
[/ol]

You can insulate under the freezer floor, make sure you don't have silty soil under the building floor, put in foundation drains, or some combination of the above.

Silts are the most frost-susceptible because, unlike sand or gravel, they are fine enough to wick moisture up several feet from the the water table, and unlike clay, they are permeable enough that capillary action can wick up large amounts of water.

"...students of traffic are beginning to realize the false economy of mechanically controlled traffic, and hand work by trained officers will again prevail." - Wm. Phelps Eno, ca. 1928

"I'm searching for the questions, so my answers will make sense." - Stephen Brust

 

[civilperson]

Insulation will not work for an extended sustained cold. It will only retard the frezing process. Cold storage warehouses are ALWAYS built on heated subgrade. If you consider the depth of frost with a permanent cold condition, then you will understand the need for heating. Fortunately, the refrigeration equipment gives off quantities of heat that you can use to heat the subgrade. One design has clay pipe continuous under the floor at five foot centers fed by a 24" diameter manifold carrying the waste heat. Once, a varmint crawled in the pipe outlet and died causing a three foot floor heave in one weekend. The columns should bear on low conductive material, oak end grain blocks and NO steel penetration should be allowed through the insulation. Thus. simple spans between columns that abut insulation are required, (a steel beam through the insulation will result in an ice ball of feet in diameter from freezing condesate in just a weekend).

 

[BigInch]

Good Post.

BigInch-born in the trenches.

http://virtualpipeline.spaces.msn.com

 

[GPSSA]

Some other suggestions have been to break up the existing floor and then to install the dual circuit heater tape, vapour seal, insulation and cast a new floor....?

Does any one know of a more economical solution???

 

[CarlB]

Do you have self-contained freezer units? If not, can you achieve a similar "air gap" approach by building a raised floor over existing?

 

[dik]

You can also use the heat from the process cooling to keep the subgrade 'warm'... As noted, unless the freezing units are self contained with an 'air gap' separating them from the existing floor, the existing floor should be reconstructed. I would avoid electrical heat tracing... my experience is that it doesn't work over an extended period of time.