shed, crusher or grinder, screening equipment, and premixer may be re-
q u i r e d . The grout lines and control system are the same as for cement
grouting.
( 2 ) Operation. Normally the batching method is best suited to mixing
clay grouts. For processed clays such as bentonite, the operation is similar
to that for cement. For cement grouts containing bentonite, the cement
should be mixed with water before adding bentonite. When natural soils are
used, the raw material is delivered to the plant by truck, scraper, or con-
veyor and stockpiled under a storage shed if necessary. Where the grout de-
sign requires predrying, the soil is spread and worked to facilitate drying.
Predrying may result in easier mixing, better dispersing, and better water
control in the grout. Moist clay will require vigorous mixing for complete
d i s p e r s i o n . The usual procedure is to crush or grind the raw soil and mix
the water to disperse the particles. The mix is then discharged on screening
equipment to remove lumps, foreign matter, and coarse material. The
screened slurry is then run into the mixer for the addition of admixtures or
into the sump for pumping to the holes.
c . Chemical Grouting. The equipment required and the assembly of a
chemical grout plant are dependent on the chemical system employed. Ade-
quate storage facilities for both dry and liquid components, mixing tools,
proportioning systems, pressure control, and flushing lines are required.
When a commercially produced chemical system is used, the manufacturer' s
recommendations for equipment and operations should be closely followed.
For projects using custom design chemical processes, the plant equipment
and operational procedures should be specified by the person or organization
designing the mix. In any case, extreme caution should be exercised at all
times to protect workmen from dangerous chemicals and fumes. An ample
supply of water is required on all chemical grouting jobs. Figures 24 and 25
show schematic layouts for typical plants used for one of the commercial
c h e m i c a l grouts.
d . Asphalt Grouting. The principal items of equipment required for
grouting with hot asphalt are heating tank, pump, supply lines, and gages in
suitable arrangement such as shown in figure 21. The pressure gage is pro-
tected from the asphalt by using a 1-in. nipple and pigtail siphon. The nipple
is filled with grease and the siphon with oil. In cold-weather operations, it
may be necessary to heat supply lines. One method is to insert a heavy, in-
sulated iron wire in the grout line. One end of the wire is connected to the
bottom of the supply line, and the other to a high-amperage, low-voltage gen-
erator, such as used in commercial welding machines. The machine is
grounded to the supply line to complete the circuit. Steam has also been used
for heating lines, but has proved cumbersome and costly. When the asphalt is
pumped in the hole, steam will form if water is present in the hole. Some of
the steam will be caught in the supply line , and provisions should be made
for bleeding if off to prevent it from blowing back into the heater. Extensive
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