Table 8. Frost-susceptibility classification of FAA-specified base
subbase materials.
Allowable
Allowable
Asphalt
FAA
% passing
% finer than
Institute
COE
designation
no. 200 sieve
than 0.02 mm
criterion
criterion
< 15
<3
P-154 subbase
No
Yes
Yes, ≤ 7%
Yes, ≤ 6%
P-208 aggregate base
515
No, > 7%
No, > 6%
<3
Yes, ≤ 7%
P-209 crushed aggregate base
08
Yes
No, > 7%
Yes, ≤ 7%
Yes, ≤ 6%
P-213 sandclay base (A)
25
No, > 7%
No, > 6%
Yes, ≤ 7%
Yes, ≤ 6%
P-213 sandclay base (B)
425
No, > 7%
No, > 6%
with the exception of the P-209 crushed aggregate
als, two specifications were chosen. One was the
base and P-154 subbase, are frost-susceptible. To
Asphalt Institute criterion that defines a frost-
make the frost-susceptible material (with the ex-
susceptible soil as one that contains more than 7%
ception of caliche, shell, and lime rock) non-frost-
passing the no. 200 sieve. The second was the
susceptible, the amount passing the no. 200 sieve
COE criterion that the amount
finer than 0.02 mm should be
25
Mat'l. No. and
one-half of the amount passing
Saturation Moist. Cont. (%)
the no. 200 sieve. The frost-sus-
1 (8.1 %)
+
4 (5.1)
50
20
ceptibility ratings are shown in
8 (3.8)
5 (7.7)
Table 8.
+ ++
3 (4.2)
2 (4.3)
Croney and Jacobs (1967)
15
7 (3.1)
found that the amount passing
6 (4.8)
+
+
the no. 200 sieve for limestone
+
10
25
(oolitic and magnesian) mate-
rials had no effect on frost
+
heave. However, the satura-
5
tion moisture content did have
a significant effect on frost
heave. They found that as the
0
0
0.2 0.4 0.6 0.8 1.0
50
100
150
200
250
Saturation
saturation moisture content in-
Hours of Freezing
Moisture Content (%)
creased, so did the amount of
heave (Fig. 6 and 7). The reason
U.S. Std. Sieve Size and No.
Hydrometer
3
3
4
4
10
40
200
suggested is the porous nature
100
of limestone. Suction of water
to the freezing front is main-
tained by the fine capillaries in
80
the rock. This finding probably
also applies to the caliche and
60
shell base course materials.
With hard limestones, this was
not the case and the amount
40
passing the no. 200 sieve had
Material
6
Materials
an effect on frost heave (Fig. 8).
1-5; 7 and 8
20
Based on the chosen criteria,
Table 7 tells us that, depending
on the gradation used, all the
0
1.0
0.1
0.01
0.001
100
10
unstabilized base materials,
Grain Size (mm)
Gravel
Sand
Figure 6. Frost heave of eight crushed
Silt or Clay
C'rse
Fine
C'rse
Medium
Fine
oolitic limestones (1 in. = 25.4 mm).
11
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