Existing Soil Materials

[AAEC]

We had just demo the existing concrete slab which was damage due to upheaving from swelling of soil materials (clay type soil. What should I do with the existing soil before we place the new concrete slab? Should I take a sample and get a proctor on it and re-condition and re-use it? Should I replace it with basecourse that do not absorb to much water?

 

[ishvaaag]

I think this is a matter on how much heave is able to be delivered by the subsoil. Normally a replacement of the same will be the path to take. Otherwise you may need to consider a structural slab on piles well anchored able to control the heave, on void forms or alike. Since this kind of problem is recurrent in the areas, maybe asking someone (contractor, engineer) may give a correct answer and evaluation about the local way to proceed.

 

[DWHA]

For frost heave to occur, one of 2 things needs to happen. Water in soil or freezing temperatures. Eliminate either one of these and heave will not occur. If the location cannot be insulated to prevent freezing temps, then remove and replace with a material that will not hold water (sand, clean aggregate, etc.)

 

[cvg]

or extend footings below the frost depth

 

[jrm73]

There seems to be too many unknowns to make such a decision to just replace the old slab with a new one. You should have a geotechnical engineer do a proper investigation (soil borings & lab tests) and recommend a new course of action. It may be that a new slab can be placed but you they may also recommend removal/ replacement of offending soils, structural suspension, elevate on select fill or soil modification. They should also recommend that you take measures keep water away from the new slab.

Good Luck