Expansion characteristics – USG HYDROCAL Gypsum Cements User Manual

Page 2

Expansion Characteristics

continued

Recommended Proportions for
Medium High-Expansion Cement
Parts
Medium High-Expansion

Parts

Maximum

Gypsum Cement

Water

Expansion

(by weight-lb.)

(in. per ft.)

100

48-50

1/8

100

44-45

3/16

Casts must be a min. of 4 to 5-in. in depth to obtain these
values. Expansion values can be increased 10 to 15 percent
by using hot water (120° to 130°F for a slurry temperature of
100° to 110°F).

Mixing

eigh expansion plaster and water as recommended and

strew plaster into water as evenly as possible. Allow
plaster to soak for a few minutes; with heavier mixes,
however, there will not be enough water to completely
soak the plaster.

With hand mixing, force plaster into water and mix
vigorously until a smooth mass is obtained. For mixes
from 10 to 15 lbs., a

⁄

-in. drill motor with a 4-in. disc

has been found to be far superior to hand mixing.

Where larger machine mixing is used, a planetary-action
batch mixer equipped with a bar-type agitator is
recommended.

Lower

Expansion

Greater

Approx. Lower Limits

Controllable

Approx. Upper Limits

and Effects

Variables

and Effects

About 60 cc

Consistency

About 40 cc

Over this amount material too

(Parts of water to 100 lb. H

YDROCAL

Below this amount material too

watery and slow set

by weight)

pasty to handle

About 1 Min.

Mixing Time

About 5 Min.

Unmixed lumps giving variable

(Mechanical mixer of appropriate size

Extremely fast set. Danger of mixing

expansion and sets

operating at approximately 1,760 rpm)

through set and disrupting structure

so no set or strength will result

About 32°F.

Slurry Temperature

About 110°F.

(Temperature of H

YDROCAL

Above this temperature set is

and water combined)

retarded. Up to this temperature

set is accelerated and may become

too fast for use.

United States Gypsum Company
Industrial Gypsum Division
125 South Franklin Street
Chicago, IL 60606-4678
Technical Assistance: (800) 487-4431