TM 5822-14/FJMAN 32-1019
must be prepared at different treatment levels and
cling, should be used as the basis of the pavement
the PI of each mixture determined. The Referee
thickness design if the reduced subgrade design
Test of ASTM D 423 and ASTM D 424 procedures
method is applied.
f. Cement content for stabilized soil. The follow-
will be used to determine the PI of the soil-cement
mixture. The minimum cement content that yields
ing procedure is recommended for determining the
the desired PI is selected, but since it was deter-
design cement content for cement-stabilized soils.
(1) Step 1. Determine the classification and
mined based upon the minus 40 fraction of the
material, this value must be adjusted to find the
gradation of the untreated soil following proce-
design cement content based upon total sample
dures in ASTM D 422 and D 2487, respectively.
(2) Step 2. Using the soil classification select
weight expressed as
A = 100BC
an estimated cement content for moisture-density
(eq 3-1)
where
tests from table 3-2.
A = design cement content, percent total
weight of soil
Table 3-2. Cement requirements for various soils
B = percent passing No. 40 sieve size, ex-
Initial Estimated
pressed as a decimal
Cement Content
C = percent cement required to obtain the
percent dry weight
Soil Classification
desired PI of minus 40 material, ex-
GW, SW
pressed as a decimal
GP, GW-GC, GW-GM, SW-SC, SW-SM
(2) Improve gradation. If the objective of modi-
GC, GM, GP-GC, GP-GM, GM-GC, SC,
fication is to improve the gradation of a granular
SM, SP-SC, SP-SM, SM-SC, SP
soil through the addition of fines then particle-size
CL. ML, MH
9
analysis (ASTM D 422) should be conducted on
samples at various treatment levels to determine
11
CH
the minimum acceptable cement content.
(3) Step 3. Using the estimated cement con-
(3) Reduce swell potential. Small amounts of
portland cements may reduce swell potential of
tent, conduct moisture-density tests to determine
some swelling soils. However, portland cement
the maximum dry density and optimum water
generally is not as effective as lime and may be
content of the soil-cement mixture. The procedure
considered too expensive for this application. The
contained in ASTM D 558 will be used to prepare
determination of cement content to reduce the
the soil-cement mixture and to make the necessary
swell potential of fine-g-rained plastic soils can be
calculations; however, the procedures outlined in
accomplished by molding several samples at vari-
MIL-STD 621, Method 100 (CE 55 effort), or
ous cement contents and soaking the specimens
ASTM D 1557 will be used to conduct the moisture
along with untreated specimens for 4 days. The
density test.
(4) Step 4. Prepare triplicate samples of the
lowest cement content that eliminates the swell
potential or reduces the swell characteristics to the
soil-cement mixture for unconfined compression
minimum is the design cement content. Procedures
and durability tests at the cement content selected
for measuring swell characteristics of soils are
in step 2 and at cement contents 2 percent above
found in MIL-STD-621A, Method 101. The cement
and 2 percent below that determined in step 2.
content determined to accomplish soil modification
The samples should be prepared at the density and
should be checked to see whether it provides an
water content to be expected in field construction.
unconfined compressive strength great enough to
For example, if the design density is 95 percent of
qualify for a reduced thickness design in accord-
the laboratory maximum density, the samples
ance with criteria established for soil stabilization.
should also be prepared at 95 percent. The samples
(4) Frost areas. Cement-modified soil may also
should be prepared in accordance with ASTM D
be used in frost areas, but in addition to the
1632 except that when more than 35 percent of the
procedures for mixture design described in (1) and
material is retained on the No. 4 sieve, a 4-inch-
(2) above, cured specimens should be subjected to
diameter by &inch-high mold should be used to
the 12 freeze-thaw cycles prescribed by ASTM D
prepare the specimens. Cure the specimens for 7
560 (but omitting wire-brushing) or other applica-
days in a humid room before testing. Test three
ble freeze-thaw procedures. This should be followed
specimens using the unconfined compression test
by determination of frost design soil classification
in accordance with ASTM D 1633, and subject
by means of standard laboratory freezing tests. If
three specimens to durability tests, either wet-dry
cement-modified soil is used as subgrade, its frost-
(ASTM D 559) or freeze-thaw (ASTM D 560) tests
susceptibility, determined after freeze-thaw cy-
as appropriate. The frost susceptibility of the
3-2
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