Page 4 - 2017-04-CFR Volume 103 Gypsum Yes or No - April 2017

Look at all the technology we have available today
for communications that was questioned
and even feared less than a decade
ago. Without it today most of us could-
n’t function. Follow along with an open
mind here.

Gypsum develops about ½ of its ultimate strength
very quickly – usually within a few hours of being
mixed and set. The other ½ of the strength comes
when all the water of convenience has evaporated
from the hardened mass (i.e. floor).

The above is important because unlike Portland ce-
ment that may take up to 28 days to develop ultimate
strength, gypsum strength happens very quickly. Im-
proving the evaporation of the free water via fans or
HVAC systems will hasten the drying time and ulti-
mate strength. Because gypsum contains two mole-
cules of chemically bound water, gypsum is a great
heat sink which makes it a desirable building materi-
al when used to slow the progress of heat due to fire.
For this reason poured gypsum underlayment is the
preferred material used in wood-frame multi-family
structures due the above
Multi-family structures include apartments, condos,
townhomes, dormitories, barracks, low-rise hotels/
motels etc. All building code bodies in the US re-
quire a minimum 1 hour fire protection between
units. UL (Underwriters Lab) is the recognized au-
thority in managing the design of walls, ceiling and
floors.

Gypsum Concrete for the Building Contractor:
Gypsum concrete used in the US for multi-family in-
stallations (INCLUDING REPAIR) must be recog-
nized by UL. Manufacturers must show the UL label
on all UL-approved products. ¾” of gypsum concrete
provides the same heat protection as 2½” of light-
weight concrete.
Gypsum concrete formulations can range in density
from 115 to 130 lbs/cu ft. with compressive strengths
beyond 12,000 psi and gypsum concrete can be for-
mulated to be “vinyl ready” with virtually no surface
corrections needed at compressive strengths that
meet and exceed resilient flooring manufacturers’
requirements. Gypsum concrete EXPANDS when it
sets. This unique characteristic results in crack-free
installations.

4 Commercial Flooring Report April 2017