exterior slab on grade

[strucbells]

Is it common practice or recommended to require a single or double polyethylene slip sheet for an exterior industrial slab on grade (no cover)? Basically a vapor retarder like for a building but the intent would be just to help reduce subgrade restraint for shrinkage and curling and help protect the slab from any unknown environmental durability issues from below (sulfates, etc.)

ACI seems to give clear guidance that vapor retarders do NOT cause curling like previously thought and some sources online claim they actually reduce curling, but ACI seems to hedge in a few places in ACI 360 and 302 due to possible impact on surface bleeding/finishing.

For context, current slab design is lightly reinforced (0.1%) with frequent sawcut contraction joints (enhanced aggregate interlock approach), placed over a 6" well graded crushed rock base. The slip sheets (if added) would go directly under the slab on top of the crushed rock base.

Seems like a minor additional cost if it helps reduce shrinkage cracking, but I haven't done a lot of these before so curious if they'll think I'm crazy for requiring it.

 

[jhnblgr]

The only issue with vapor barriers is all the water works its way up through the concrete, making it more difficult to finish with excess bleed water. Also if used rebar can’t be used for grounding. I think vapor barrier then stone then concrete would be best, stone protects vapor barrier from puncture when placing concrete.

 

[strucbells]

Placing the vapor barrier under the stone doesn't seem to help with the friction/base restraint at all really which would be the main reason to add it in at all