this
purpose.
It was fabricated in a local shop economically.
(2) Grand Coulee-type g r o u t mixer, 21-cu-ft capacity. In the grouting
at Hoover Dam, considerable experimenting was done with various equipment
for mixing grout. Concrete mixers were first used but were later discarded
for the type mixer shown in figure 10. The body of this mixer is 30 in. (ID)
by 48-1 / 2 in. long. There are 16 paddles in series of 4 mounted on a
2-in. -diameter shaft. The paddle shaft is supported on the back end by an
extended babbitted bearing with cap, and on the other end by a split-cap,
rigid, babbitted pillow block. The body is made of a 3/16 -in. plate with front
head 1/4 in. thick and a removable back head 3/8 in. thick. The removable
back head not only facilitates the removal of the paddles but also permits
thorough cleaning and chipping out of hardened cement, if necessary. The
shaft has supplemental bearing supports in the heads that consist of bronze -
bushed, welded-in steel hubs.
top, 14 in. in diameter at its junction with the body, and 14 in. high. There is
2.65-hp air motor that makes 65 rpm when supplied with air at 100 psi. Its
consumption is approximately 85 cfm. A bolted coupling connects the motor
to the mixer. The body is supported on two welded reinforced saddles at-
tached to 4-in. I-beam skids which are not shown in the figure.
(3) Grand Coulee-type g r o u t mixer, 27-cu-ft capacity. For the contrac-
tion joint grouting at Grand Coulee Dam, two 27-cu-ft mixers, as shown in
figure 11, were purchased. T h e y are similar to the 21-cu-ft model. These
mixers are easy to run and to clean and are very flexible. They handle
batches of grout made from 1 to 10 sacks of cement and do a thorough job of
.
m i x i n g . These mixers were powered by air motors.
( 4 ) High-speed colloidal-type mixers. H i g h - s p e e d colloidal-type grout
mixers are commercially available in both the single - and double -drum
types. These mixers are equipped with small centrifugal pumps, which
cause the grout to circulate at high speed while being mixed. Particles of
cement may be broken and rounded to a significant degree in high-speed
m i x e r s . This results in an increase in pumpability and penetrability for
p o r t l a n d - c e m e n t grout. In an emergency, grout can be pumped at low pres-
sures into the foundation or other places with the centrifugal pumps of these
mixers.
( 5 ) Water meters. A satisfactory water meter is the single-disk type,
s i z e 1-1/2 in., and threaded for pipe connection. This type has a 6 -in. verti-
cal register with a long hand that makes one revolution per cubic foot of
water and a short hand that indicates 10 cu ft per revolution. For use in
grouting, the meter should have a reset knob to set the hands to zero and a
d i r e c t - r e a d i n g totalizer. A screen should be provided if sand or rock parti-
cles are present in the water supply.
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