Can flow fill (CLSM) be used as a fill material to meet frost protection requirements?

[dauwerda]

I have an equipment foundation that needs to be frost protected. In this case, the frost depth is 48".

In section 4.2 of ASCE 32 it states, "Foundations placed on a layer of well-drained, undisturbed ground or fill material that is not susceptible to frost shall have the thickness of such a layer included in meeting the design frost depth defined in Section 3.2. Undisturbed granular soils or fill material with less than 6% of mass passing a #200 (0.074 mm) mesh sieve in accordance with ASTM D422 and other approved non–frost-susceptible materials shall be considered non–frost-susceptible"

My thought is to excavate the area of the foundation down to frost, then fill the excavation with flow fill. The foundation would then be formed and poured on top of the flow fill, allowing it to only be 12" - 18" thick rather than 48" thick. So, as the subject asks, can flow fill be considered a non-frost-susceptible fill material? What are everyone's thoughts on this?

Thanks!

 

[jayrod12]

AS in lean mix concrete? My first thought would be no, because the frost could grab the sides of the lump of lean mix and still try to jack it up. But others may have different opinion.

 

[dhengr]

Jayrod12:
Would that same thinking and logic apply to the found. walls on your light framed houses or on your stem wall on an unheated garage? There are many more lineal feet of those found. walls, and they are likely less heavily loaded too.

Dauwerda:
The one problem with a pad out in the middle of nowhere is that you are not likely adding any heat to the soil system under that pad. I would think that it might be worth getting some GeoTech advice on this matter for the general soils conditions in your area. Then, do a good job of grading the site around the pad, for drainage away from the pad a sufficient distance, and maybe you don’t have to do anything special. Of course, you should always remove all organic or deleterious materials, and place the pad on compacted or undisturbed soil. And, connections to the equipment should always be made with some potential movement in mind. Take a look at the current thread “Concrete pad foundation design,” ‘ thread256-396557 ‘ over in the foundations forum. This topic has been discussed in other thread also, try a search of that topic.

 

[dauwerda]

jayrod12:
Yes, I am talking about a lean concrete mix. As dhenger mentioned, I don't see how grabbing the sides of the foundation would be any more or less of an issue if it is a lean concrete mix or a full depth structural concrete foundation.

dhenger:
I agree, grading for proper site drainage is very important. And yes, the problem with equipment foundations is the lack of heat added as there is with a conditioned building. So, the traditional grade beam / footing and stem wall / thickened edge slab designs don't solve the problem of frost heaving the foundation unless you also add insulation below and around the foundation per ASCE 32. The insulation helps retain the earth's heat below the foundation without the help of a heated building above it. Rather than messing with insulation the ASCE 32 also allows for the foundation to be constructed on top of non–frost-susceptible material that goes down to the design frost depth.
As for the thread you linked, I don't see how it pertains to my question, however I probably should have started this thread in the foundations forum. I did do a search of my question and didn't find anything that really addressed it.

Thanks for the replies!

 

[BUGGAR]

You might check out some of the things they do in Alaska to stop frost heave. I like the lean concrete mix - can you reverse taper the sides or put thin sheet of styro on the sides to prevent lifting from adjacent soils?

 

[oldestguy]

I'd say it also depends on what the code means for "Frost depth". It really, on the job, can vary from next to nothing to double the code figure, all depending on insulation, moisture content and soil type. Also damage or heaving can be insignificant or serious again depending on these factors. Usually that "Frost depth" is a general thing that may not apply specifically to your site other than requiring some code conformance legally. The advice to get local soil information, preferably with an experienced geotech, would help a lot. Remember concrete is good conductor of heat, better than most soil. Also, how critical is the equipment supported?