TM
5-818-6/AFM
88-32
obtained and the grout will be stable. The presence of cement may affect the
groutability of clay grouts,. a point which must be considered. For large
amounts of cement the grout should be considered as a portland-cement
grout with soil additive.
( 2 ) Chemical. There are several chemicals that can be used in soil
grouts to modify the grout properties, but little experience has been reported
in the literature. The effect that a chemical additive will have on a clay
grout will depend on the mineralogical and chemical properties of the soil.
Following is a partial listing of electrolytes, as reported by Kravertz (35),
that are used in quantities less than 5 percent, by weight, as stabilizing
agents or flocculants in clay grouts.
Stabilizing
Agents
Flocculating
Agents
Potassium nitrate
Aluminum sulfate
Potassium
carbonate
Sodium sulfate
Sodium aluminate
C a l c i u m chloride
Sodium silicate
Copper sulfate
Lithium carbonate
F e r r o u s sulfate
Sodium hydroxide
( 3 ) F i l l e r s . Sands can be used as fillers in
clay-cement
grouts w h e r e
voids to be filled are sufficiently large to Permit
intrusion of
these p a r t i c l e
s i z e s . Where large quantities of grout take are
anticipated,
an econmical
gain will be achieved through use of sand fillers,
without loss
in quality of
the grout.
f . Proportioning Clay Grout. Once a soil has been determined suitable
as a grout material for a given job, it is necessary to determine the water
and admixture requirements to achieve desired properties in the grout. The
grout must have sufficient flowability without excess shrinkage, and after a
s p e c i f i e d time, it should develop a gel of sufficient strength. The flowability
will depend upon the water- clay ratio, which from the standpoint of bleeding
should be kept to a minimum. To provide a suitable gel, it might be neces-
sary to use chemical additives such as sodium silicate to improve the gel
strength at high water-clay ratios. Because of the wide range of physioc-
hemical properties of fine-grained soils that affect grout properties, it is
necessary to use a trial procedure to achieve the desired results. Trial
batches with varying proportions of soil, water, and admixtures should be
mixed, duplicating field conditions as closely as possible. Samples from the
trial batches should be tested for stability, viscosity, gel time, shrinkage,
and strength. From the results the most suitable mixtures can be selected
and criteria for changes in the mixture proportions to meet field conditions
can be determined. The batch size for trial mixes should be sufficient to
provide adequate samples for the various tests.
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