be hand mixed. The mechanical mixers shall be an approved type that
accurately and uniformly controls the quantity of water. When mixing by
hand, mix dry plaster aggregate to a uniform color in the mixing box, add
water, and hoe the plaster immediately into the water and mix thoroughly to
a proper consistency.
Water used for rinsing and cleaning containers and tools shall not be used
in mixing the materials.
Sand proportions shall be damp and in loose condition. A volume of damp
loose sand shall contain a minimum of 36 kg 80 lb of dry sand in 0.0283 cu m
one cu ft.
Mix the material while the mixer is in continuous operation in the
following sequence:
a.
Add maximum close to 90 percent of estimated quantity of water.
b.
Add approximately one-half of the sand.
If vermiculite or perlite
is used, add all the aggregate.
c.
Add cement and approved admixtures. [Add lime prior to cement.]
d.
Add remainder of sand.
e.
Mix with remainder of water as required.
Mix until the mixture is
uniform in color and consistency.
Avoid excessive mixing and agitation. Discard gypsum plaster which has
begun to set before it is used; retempering will not be permitted. Do not
use frozen, caked, or lumped materials. Empty mixers and mixing boxes
after each batch is mixed, and keep free of old plaster.
2.8.2
Ready-Mixed Packaged Materials
Mix ready-mixed packaged gypsum plaster in accordance with manufacturer's
printed instructions.
2.9
BONDING AGENT
**************************************************************************
NOTE: Bonding agents may be surface applied or
integrally mixed with the plaster. Use Integral
bonding agents only after review of the
manufacturer's documentation of testing and past
performance. Check compatabiity of the bonding agent
with the plaster mixtures. Bonding admixtures
increase the potential for shrinkage of the plaster.
**************************************************************************
ASTM C 631, interior application.
PART 3
EXECUTION
3.1
SURFACE PREPARATION
Clean surfaces before application of gypsum plaster of projections, dust,
loose particles, grease, bond breakers, and foreign matter . Do not apply
plaster directly to surfaces (1) of masonry or concrete that have been
SECTION 09210
Page 12
Previous Page
