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Subject: Flooring


From: Connie McCabe <c-mccabe>
Date: Thursday, August 9, 2001
Jeffrey Maish <jmaish [at] getty__edu> writes

>We are in the process of a remodelling a space that has a concrete
>floor that has been patched at different points over the years. This
>lab is for heavy objects, frequently has wheeled lifts and forklifts
>rolling over it so has to be fairly impact resistant as well as
>chemically resistant. We are looking into possible ways to refinish
>the concrete and wondered if anyone has had experience with
>resurfacing concrete floors. ...

I just saw your note on the DistList, and thought I'd just share a
bit of what I've recently learned about coating a concrete floor
with epoxy.

There are several kinds of epoxy flooring, thin coat and thick coat,
such as the terrazzo flooring you have all through your buildings (I
love the Getty's terrazzo restroom floors with the blue and
colorless glass chips!).  The thick coat (usually 1/4-3/8 inch) may
be a good choice for you, since they are "self-leveling" and will
disguise the concrete repairs and patches. Some are made for
heavy-duty industrial use (like factories and airports).

There are straight epoxies and some hybrid epoxy-acrylics, which
might be useful if there is any dampness in the concrete.  The
thick-coat epoxies can include things like vinyl or walnut chips.
And the terrazzo-type can include any kind of decorative aggregate.
Sand can be applied to the surface of any epoxy for traction which
is then supercoated with another thin epoxy layer.

No matter what, the surface of the concrete must be prepared
according to the application instructions. This means at least clean
and de-grease. Most likely you will have to profile the surface,
which means shot blast, acid etch, or scarify to give the concrete a
tooth so the epoxy will hold. It will be messy.  So get copies of
the application instructions of the coatings you're interested
in--which is sometimes harder than it sounds. Find the part that
says "Surface Preparation" and take it from there so you'll know
what you're in for.

There is a standard test method to determine if the water vapor
emission is low enough to coat the epoxy directly onto the concrete
subfloor. You can buy kits from flooring companies--they cost about
$14 each--you need at least three depending on the area of your
floor. Or you can pay someone to do it and they charge a small
fortune. Or you can set it up yourself using ASTM F-1869-98,
Standard test method for Measuring Moisture Vapor Emission Rate of
Concrete Subfloor using Anhydrous Calcium Chloride." You can get a
copy using the ASTM web site, but may of the flooring companies will
have a copy you can use.

If you really want to use straight epoxy but your floor just doesn't
seem to want to dry out, there are drying agents that are used in
conjunction with the epoxy--but the floor still must be profiled
before subjecting it to the drying agent. Once the moisture vapor
emission is low enough, the epoxy can be applied.

If you have to pour a new thin-layer concrete sub-floor (such as
might be necessary if you're installing compact shelving), it is
handy to know that light-weight concrete takes longer than standard
concrete to dry (at least 190 days), and even then you may have to
use a drying agent to get the water vapor emission low enough to
coat it with epoxy.

Bottom line: go to your local industrial flooring companies and see
what they think about your site and the options they offer. Talk to
several installers that have done this for a long time: they will
tell you what will and won't work, since they have to warranty the
installation.  And go to the web and do a search under "epoxy floor"
and "terrazzo".  You will be amazed by all the options available.
Good luck,

Connie McCabe
Senior Photograph Conservator
National Gallery of Art
Washington, DC

                  Conservation DistList Instance 15:16
                 Distributed: Thursday, August 9, 2001
                       Message Id: cdl-15-16-003
Received on Thursday, 9 August, 2001

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