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RE: Slab-On-Grade Vapor Barrier (Scott)

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Scott:

You are correct about the 10-mil thickness (I've recently been through ACI
302.1). The committee "...strongly recommends a thickness of 10-mils be
used. The increase in thickness offers increased resistance to moisture
transmission while providing more durability during and after its
installation." (Section 3.2.3).


Regards,
Dave K. Adams, S.E.
Lane Engineers, Inc.
PH: (559) 688-5263
E-mail: davea(--nospam--at)laneengineers.com



-----Original Message-----
From: Scott E Maxwell [mailto:smaxwell(--nospam--at)engin.umich.edu]
Sent: Thursday, August 31, 2000 7:46 PM
To: INTERNET:seaint(--nospam--at)seaint.org
Subject: RE: Slab-On-Grade Vapor Barrier (One More Time)


And also consider using a heavier "barrier" to reduce the chance of
puncturing it.  I have been "taught" to use at least a 10-mil below the
graded material.

Scott Maxwell, PE, SE


On Thu, 31 Aug 2000, Mark Gilligan wrote:

> The question was asked "or has the wheel turned yet again?"
> 
> Yes things have recently changed.  ACI now recomends some graded material
> instead of sand between the concrete and the membrane.   This is in one of
> the reports in the ACI Manual of Practice.
> 
> Mark Gilligan
> 
> 
> ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
> >Okay, I know this horse has been beaten into dogfood, but I'm slow (and
> don't
> face this that often).
> 
> Please remind me.
> 
> "Old" practice was to put e.g. 6-mil "Visquine" or equal directly under
the
> slab. Later it was discovered this was NOT a good idea, as the hydrostatic
> pressure in the slab through-thickness weakened the cement (and caused the
> slab
> to cure more slowly at the bottom). This led to cracking and a
not-so-great
> slab.
> 
> LATER practice (this is where I'm fuzzy) was to put SAND directly under
the
> slab, THEN the Visquine. That way any water would bleed out of the slab
> into the
> sand, yet "new" water vapor wouldn't come up from the soil below.
> 
> Have I got that right, or has the wheel turned yet again?
> <
> 
> 
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