A primary difference between soillime and
ed dry and blended mechanically. This mix was
then allowed to cure (7 days) before the freezing
soilcement mixtures is the rate of strength gain
test was done. The samples were also saturated
during curing. Soilcement mixes gain strength
prior to testing. The frost-susceptibility of the
rapidly, whereas soillime mixtures take longer.
samples was evaluated from a portion of the
For example, a soil (CL) and lime (510%) mix-
heave versus time curve, where the slope was
ture attains an unconfined compressive strength
of about 2760 kPa (400 lb/in.2) after 36 weeks,
relatively constant. The result was reported as the
average of the rate of heave (over 5 days) of all
whereas soil (CL) and cement mixtures attain the
samples tested. The rate of penetration was also
same strength after 4 days.
relatively linear at about 6.4 mm (0.25 in.) to 19
There is very little information in the literature
mm (0.75 in.) per day. Since the heave rate is a
on the behavior of stabilized materials that are
function of molding moisture content, compacted
subjected to frost action. The COE conducted sev-
density, overburden pressure, and rate of freez-
eral studies between 1943 to 1949 on how to
ing, the authors suggested that heave rates re-
reduce the frost-susceptibility of base materials.
ported were probably within 15%.
However, most of the studies concentrated on
The gradations of the unstabilized soils used
reducing the freezing point of water. We did
by Lambe and Kaplar in 1971 are shown in Figure
obtain some information from Lambe and Kaplar
9. These were fine-grained materials, called: 1)
(1971) and Lambe et al. (1971). They used port-
Boston blue clay (CH), having a liquid limit and
land cement and lime as the stabilizing agents.
PI of 53 and 26, respectively; 2) New Hampshire
They considered the two to be either void filling
silt (ML-CL), having a liquid limit and PI of 24
or cementatious and thought them uneconomi-
and 6, respectively; and 3) Fort Belvoir sandy clay
cal. Void filling in subgrades or base courses
(CL), having a liquid limit and PI of 41 and 19
would alter the materials, making them similar to
respectively. For the sandy clay, all material
asphalt concrete or portland cement concrete.
above the no. 10 sieve was removed. No tests
Since all the voids are filled, there would be no
were conducted with base course type soils or
capillary action, thus making the materials non-
gradations.
frost-susceptible. Cementing could increase the
The rate of heave ratio presented in Table 9 is
tensile strength of the materials and thus their ca-
the ratio of the rate of heave of the stabilized soil
pability to resist frost heave.
to the rate of heave of the unstabilized soil. A ratio
In the Lambe and Kaplar (1971) and Lambe et
of less than 1 indicates improvement. A value
al. (1971) work, lime or portland cement was add-
U.S. Standard Sieve Numbers
Hydrometer
6" 4"
2"
1"
10
40
200
3/8"
100
0
Boston Blue Clay (CH)
80
20
60
40
Sandy Clay (CL)
40
60
20
80
NH Silt (ML-CL)
100
0
100
10
1
0.1
0.01
0.001
Grain Size (mm)
Gravel
Sand
Cobbles
Silt or Clay
Coarse
Fine
C'rse
Medium
Fine
Figure 9. Gradation curves for soils used in stabilization study of Lambe and Kaplar (1971)
and Lambe et al. (1971).
14
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