blinding concrete removal

[geo321]

Good day,

the contractor is proposing to remove the blinding concrete under the slab on grade and replace it by a layer of tout venant of 200mm thickness. After compaction, he will place the vapor barrier then the steel bars.

My only concern is that i am worried for the vapor barrier since placing it above crushed stone may break it but other that, I think there is no problem regarding this issue.

Your thoughts ?

Thank you.

 

[thaidavid40]

Vapor barriers get placed on top of the drainage fill (stone) layer all the time around here. The greater threat to the barrier is the placement of the reinforcing, and the craftsmen walking on top of it. Those actions tend to damage it more than any other. Some engineers place a sand layer on top of the stone layer (with a geogrid separator), with the expectation that it "cushions" the vapor barrier to some degree, and protects it. I've never seen any research done on this, but it does make some logical sense. In any event, a vapor barrier is not intended to be totally waterproof anyway - only a barrier to slow down the vapor transmission a bit. Some damage to this barrier is acceptable, and probably unavoidable too. It all depends on how much damage you consider acceptable, and what kind of floor finishes you are trying to protect.
Dave

Thaidavid

 

[geo321]

Thanks a lot dave.
So the contractor proposal is acceptable.
Thanks again