TM
5-822-14/AFJMAN
32-1019
CHAPTER 3
DETERMINATION OF STABILIZER CONTENT
3-1. Stabilization with Portland Cement. Port-
is presented in appendix B. If the pH of a 10:1
mixture (by weight) of soil and cement 15 minutes
land cement can be used either to modify and
after mixing is at least 12.0, it is probable that
improve the quality of the soil or to transform the
any organics present will not interfere with nor-
soil into a cemented mass with increased strength
mal hardening.
and durability. The amount of cement used will
(2) Sulfates. Although sulfate attack is known
depend upon whether the soil is to be modified or
to have an adverse effect on the quality of hard-
stabilized.
ened portland cement concrete, less is known
a. Types of portland cement. Several different
about the sulfate resistance of cement stabilized
types of cement have been used successfully for
soils. The resistance to sulfate attack differs for
stabilization of soils. Type I normal portland ce-
cement-treated coarse-grained and fine-grained
ment and Type IA air-entraining cements were
soils and is a function of sulfate concentrations.
used extensively in the past and gave about the
Sulfate-clay reactions can cause deterioration of
same results. At the present time, Type II cement
fine-grained soil-cement. On the other hand, gran-
has largely replaced Type I cement as greater
ular soil-cements do not appear susceptible to
sulfate attack. In some cases the presence of small
sulfate resistance is obtained while the cost is
amounts of sulfate in the soil at the time of
often the same. High early strength cement (Type
mixing with the cement may even be beneficial.
III) has been found to give a higher strength in
The use of sulfate-resistant cement may not im-
some soils. Type III cement has a finer particle
prove the resistance of clay-bearing soils, but may
size and a different compound composition than do
be effective in granular soil-cements exposed to
the other cement types. Chemical and physical
adjacent soils and/or ground water containing high
property specifications for portland cement can be
sulfate concentrations. A procedure for determin-
found in ASTM C 150.
b. Screening tests for organic matter and sul-
ing the percent SO4 is presented in appendix C.
fates. The presence of organic matter and/or sul-
The use of cement for fine-grained soils containing
more than about 1 percent sulfate should be
fates may have a deleterious effect on soil cement.
avoided.
Tests are available for detection of these materials
c. Water for hydration. Potable water is nor-
and should be conducted if their presence is sus-
mally used for cement stabilization, although sea
pected.
(1) Organic matter. A soil may be acid, neu-
water has been found to be satisfactory.
tral, or alkaline and still respond well to cement
ments for cement stabilized base and subbase
treatment. Although certain types of organic mat-
courses are indicated in table 3-1.
ter, such as undecomposed vegetation, may not
e. Cement content for modification of soils.
influence stabilization adversely, organic com-
(1) Improve plasticity. The amount of cement
pounds of lower molecular weight, such as nucleic
required to improve the quality of the soil through
acid and dextrose, act as hydration retarders and
modification is determined by the trial-and-error
reduce strength. When such organics are present
approach. If it is desired to reduce the PI of the
they inhibit the normal hardening process. A pH
soil, successive samples of soil-cement mixtures
test to determine the presence of organic material
Table 3-1. Gradation requirements for cement stabilized base and subbase courses
Percent Passing
Type Course
Sieve Size
1 in.
100
Base
70-100
in.
45-70
No. 4
10-40
No. 40
0-20
No. 200
100
1 in.
Subbase
45-100
No. 4
10-50
No. 40
0-20
No. 200
3-1
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