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RE: Slab-on-grade

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You have some real concerns here.  2% is pretty low but there are ways to 
accelerate it, eg, heat and air circulation and ventilation.  time/ 
moisture content curves are not really available because there are so many 
variables, RH of air, RH of soil, presence of vapor barrier, temp, 
thickness of slab.  I don't recommend sealing the moisture in.  Many 
problems can stem from that.  I've been in suits regarding just this topic. 
 I strongly recommend getting the water as low as posible going in with SP 
and then testing the moisture until it gets to where you need it.

-----Original Message-----
From:	Harold Sprague [SMTP:harold.sprague(--nospam--at)]
Sent:	Wednesday, November 18, 1998 10:52 AM
To:	'seaint(--nospam--at)'
Subject:	RE: Slab-on-grade

The advice is appreciated.  Currently we will have a layer of crusher fines
directly under the concrete and above the vapor retarder.  The crusher 
compact easily and stay in place while placing the concrete.

What I was looking for is ways to reduce the moisture in the slab like
vacuum dewatering, dropping the w/c ratio as low as possible, etc.

Does anyone have any data for various mixes, and a time to moisture content

One additional constraint is that the contractor wants to use a slick line
to place the concrete.  This is the worst method of placement, because it
greatly reduces the flexibility of the mix design.  The mix needs to have
more sand and more cement, which increases the water demand.

Harold Sprague
The Neenan Company

-----Original Message-----
From: dan914(--nospam--at) [mailto:dan914(--nospam--at)]
Sent: Wednesday, November 18, 1998 6:37 AM
To: seaint(--nospam--at)
Subject: Re: Slab-on-grade

A word of caution - be careful of curling of the slab.  I have heard so 
arguments pro and con for vapor barriers and different details to stop
that it becomes very contrdictory.

Harold Sprague wrote:

> I have a slab-on-grade on which a seamless adhered floor covering is to 
> applied.  The manufacturer requires a moisture content of about 2% prior
> installation.
> Is there any way to drive the moisture content that low in about 2 months
> time?
> We are placing a vapor barrier and have other details to mitigate ground
> water.  My concern is the water that will be in the concrete.  Our 
> mix has a w/c ratio of about 0.47.
> The only other choice is a surface applied sealant that could trap water
> vapor within the slab.
> Comments and solutions are welcomed.
> Regards,
> Harold Sprague
> The Neenan Company
> harold.sprague(--nospam--at)