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RE: Slab-on-grade

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The advice is appreciated.  Currently we will have a layer of crusher fines
directly under the concrete and above the vapor retarder.  The crusher fines
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 many
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 be
> 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 current
> 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)