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Re: Air entrainment vs hardener

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Sherman,

        Perhaps you can change your detail at the side.  In Canada it would be
common to have a grade beam or foundation wall around the perimeter of a
building, the slab on grade floor would then be poured inside of the grade beam
and would not be exposed to the outside weather conditions.  A variation of this
would include placing a 2x4 or 2x6 in the formwork at the top of the grade beam
(foundation wall); this would give a 1.5" seat for the slab to rest on top of
the grade beam.

Regards,

H. Daryl Richardson

"Sherman, William" wrote:

> I'm curious how others solve the following problem: I have a floor slab at
> grade for which a concrete surface hardener is desired in an industrial
> equipment area. The outside edges of the floor slab will be exposed to the
> weather in a freeze-thaw environment (northeast US), but it is otherwise in
> an enclosed area. The building interior is industrial and the interior
> temperature will be kept above 50 or 60 degrees F.
>
> 1. Should the slab be air entrained due to freeze-thaw exposure at the
> edges? It seems that this is the worst freeze-thaw exposure, right at
> finished grade where moisture and temperature will vary the most. On the
> other hand, will the limited surface exposure and heat from the interior
> reduce the effects of freeze-thaw on the exposed concrete edges?
>
> 2. Air entrainment creates finishing difficulties and is not recommended for
> trowelled finishes with shake hardeners. (Possible blistering and
> delaminations if not finished properly.) A separate surface applied epoxy
> topping could be applied after the concrete cures, but this would add
> considerable cost relative to a shake hardener.
>
> So what solutions have others used?
>
> William C. Sherman, PE
> CDM, Denver, CO
> Phone: 303-298-1311
> Fax: 303-293-8236
> email: shermanwc(--nospam--at)cdm.com
>
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