Capillary Break and slab THickness

[kamrang]

Hi,

Some geotech consultant recommend omitting capillary break under a slab with thickness of 10 inch or greater. They still recommend using vapor barrier/retarder.

Is there any kind of publication which talk about this elimination of capillary break?

Thanks

 

[Ron]

10-inch thick concrete, well placed and consolidated, will not "wick" a lot of water....it will; however, contain a lot of water that will come out at the surface with time. That would occur regardless of the use of a capillary barrier or vapor barrier.

Think of a 10-inch thick concrete tank holding water...even uncoated, it isn't likely going to leak.

 

[dik]

By capillary rise, if the underside of the slab is in contact with water, the slab will carry the moisture upwards. Capillary rise can wick moisture up several feet.

I would still use PEVB btw the slab and fill; I don't like to rely on free draining aggregate.

Have to minimize moisture and temperature differences btw top of slab and bot of slab. Using the PEVB, there is a bit of a tendency for the slab to 'curl' and if you are looking for a fairly flat slab, you might want to do a bit of research on this.

Dik