Concrete Cover w/ vapor barrier
Concrete Cover w/ vapor barrier
(OP)
Can the required 3" of concrete cover be reduced for a slab that is cast against the ground if a vapor barrier is used?
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Concrete Cover w/ vapor barrier
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Concrete Cover w/ vapor barrierConcrete Cover w/ vapor barrier(OP)
Can the required 3" of concrete cover be reduced for a slab that is cast against the ground if a vapor barrier is used?
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RE: Concrete Cover w/ vapor barrier
VB's are not always placed perfectly so I would probably still require the 3".
RE: Concrete Cover w/ vapor barrier
RE: Concrete Cover w/ vapor barrier
RE: Concrete Cover w/ vapor barrier
-add 10mm cover if cast onto a vapour barrier (compared to cast against formwork).
-add 20mm cover if cast directly onto the ground.
RE: Concrete Cover w/ vapor barrier
RE: Concrete Cover w/ vapor barrier
RE: Concrete Cover w/ vapor barrier
1. The potential exposure to moisture from the soil.
2. The reduction in cover due to variable subgrade elevation.
3. The mixing of soil and concrete at the interface.
Placing the slab on a good quality vapor barrier such as 15 mil polyolefin over a well-compacted cushion layer will help address some of these concerns. A reduction in cover is reasonable, but is not directly addressed in the ACI 318 code. I guess that is where "engineering judgment" comes in.
RE: Concrete Cover w/ vapor barrier
RE: Concrete Cover w/ vapor barrier
stick to 3", VB will just add protection for your slab againts moisture and undesirable chemical contamination of your subgrade.
RE: Concrete Cover w/ vapor barrier
Don Phillips
http://worthingtonengineering.com
RE: Concrete Cover w/ vapor barrier
RE: Concrete Cover w/ vapor barrier
The floor finish was a vinyl backed carpet tile. About 9 months later, a portion of the vacant floor was being built out and when the tile was lifted, mold was growing under the vinyl. We normally did a full spread glue but on this project, we again executed a deduct change order to use the grid method of glue, as recommended by Milliken.
We did a mositure test of the salb, inconclusive; monitored temperature and humidity for a couple of weeks, inconclusive; reviewed the concrete test reports to ensure the maximum slump was not exceeded; inconclusive.
We cleaned up the mold, replaced the carpet, and laid it down. We found the main lobby also had a lot of moldy areas as well. They were cleaned up and the carpet replaced.
The only thing we could think of - since the floor one slab was placed well after floor two - since it had an underfloor cellular system like that used on floor 2, hydration may not have been complete and the concrete was moist enough foster mold growth under the vinyl.
The next project in Portland, OR in 1992, we did not delete the vapor retarder, we had the concrete tested to ensure it was "dry" enough (by that time, glue was becoming water based and sensitive to moisute in the concrete) and we went back to the full spread glue method. We monitored it and did not find a recurrence.
Don Phillips
http://worthingtonengineering.com
RE: Concrete Cover w/ vapor barrier