Sealing cement

Michael McColgin <mimccol [at] dlapr__lib__az__us> writes

>A new museum has a huge storage area that's excellent in every way
>*except* for the cement slab.  The builder says it may take 2 years
>for the cement to cure.  The odor is overwhelming and the area is
>currently used for storing both artifact and photograph collections.

Curing concrete can indirectly cause several problems for
collection-holding facilities. A coatings engineer once related to
me that concrete, a combination of alkaline calcium oxide, silica,
iron and aluminum oxides that forms a solid when hydrated, is
exothermic while curing and, while never producing high
temperatures, does result in small particles of silica and silicates
to be given off as dust-sized, (0.5 to 5 micron) particles. These
are highly abrasive--like glass. Calcium sulfate is also added to
large concrete pours to slow curing and hydrated sulfate particles
can also be put in the air. These could result in tarnish/corrosion
problems for photographs and metals. I've never seen hard research
figures on this but it made sense to me. I'd be interested in
others' experiences in this arena. In any case, the coatings
engineer thought that it would be smart to seal concrete and
concrete block before allowing collections into these spaces.

Dale Paul Kronkright

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                  Conservation DistList Instance 9:50
                Distributed: Saturday, December 23, 1995
                        Message Id: cdl-9-50-002
                                  ***