(1) Agitator sumps. After mixing, grout should be agitated to prevent
settlement while it is being pumped. This can be done by pumping the grout
into a sump equipped with a stirring blade. Figure 12 shows a type of agita-
tor that has proved satisfactory. The agitator should have the same capacity
as the mixer so that one batch of grout can be pumped while the next batch is
b e i n g mixed. When emptying the grout from the mixer into the agitator, the
grout should pass through a 1/8-in. - m e s h screen to remove pieces of sacks,
strings, wire, ties, or other foreign matter that may be dropped into the
Types of Pumps. Pumps for cement grouting should be sufficiently
flexible to permit close control of pressure and to provide for a variable
rate of injection without clogging of valves and feed lines. With constant-
speed pumps, special arrangements of the supply piping systems and valves
are needed to provide close control of the grouting operation. Constant-
speed pumps are powered by electric motors or internal-combustion engines.
Variable speed pumps are hand operated, steam driven, or air driven.
(1) Hand pumps. Hand-operated pumps are used infrequently; they are
satisfactory only when the amount of grout to be injected at any one time is
v e r y small. Their weak points are the check valves, which usually become
plugged and stick after a short period of operation, and the packing, which
frequently leaks grout as the pumping pressure is built up.
( 2 ) Air-driven pumps.
A number of air -driven pumps are commercially
a v a i l a b l e . The reciprocating
slush pump shown in figure 13 is available in
sizes from 20 to 100 gpm at
pressures from 200 to 500 psi when supplied
with air at pressures of 100
psi. This type of pump is suitable for most ce-
ment and clay grouting.
( 3 ) Power-driven pumps. Power -driven pumps have the same grout
ends as the air -driven pumps, but require an external power source. This
source is connected to the pump by gear, chain and sprocket, or V-belt
d r i v e s . A wide variety of power sources are available.
--. Reciprocating Slush Pumps.
(1) Line -type p umps. The advantage of the line -type slush pump
(fig. 13) is the accessibility of the valves. The discharge valves are located
directly above the suction valves so that both can be removed through the
same opening in the top of the pump "for cleaning or repair. The disadvan-
tage of this type of pump is that it requires two types of suction and dis-
charge valves and valve seats.