slab deterioration

[rittz]

The slab-on-grade is in the basement of a 70-year-old masonry grocery warehouse 100' x 80'. THere is widespread efflorescence, some surface deterioration, some heaving. The floor will be used to house exercise equipment (light loading) (fitness center)to be carpeted. The floor does not seem to be damp at the moment. Could one place a 2" lift of concrete with some sort of fabric between with confidence even if the slab has been severly weakend by age, or aggregate attack, or whatever. Assuming that whatever source of moisture that might have been present at one time is no loger present.

 

[Ron]

My only concern would be the heaving. Otherwise, a two-inch thick polymer modified concrete topping could be used. Keep in mind that even if you use a separator, you'll likely get reflective cracking.

An alternative would be similar to a "crack and seat" pavement renovation. Break up the existing slab, provide separator or fill all voids with sand,compact and place new slab over the prepared subgrade...that way you keep the waste in place and don't need to get it out of the basement. Would also help maintain more ceiling height.

 

[JAE]

One other thought - since this is a basement, the basement slab might be essential to holding the lateral thrust of the basement wall in check. By removing the entire slab, or breaking it up to some degree, you might remove the entity that is resisting the earth pressure from moving the base of the wall inward. A phased replacement would be required in this case.

 

[Ron]

Good point JAE...another possibility is to leave a strip at the perimeter intact while the remainder of the interior is done

 

[LobstaEata]

In addition to the heaving issue, if there is widespread efflorescence, then there must be moisture migration through the slab which would be sufficient to draw out salts from the concrete. I'd wonder if there is any moisture barrier under the existing slab. If not, a concrete overlay may level the floor, but will not address the moisture issue. Mold under a new carpet might be an unwanted consequence.

Hope this is helpful.