determine the frost-susceptibility of material
FROST HEAVE
identified as Tilcon common granular fill. The
Frost heave, or the raising of the surface layer
testing procedure used at CRREL is ASTM D5918-
because of ice in the subsurface, is detrimental to
96, Standard Methods for Frost Heave and Thaw
pavement structures. By increasing the amount of
Weakening Susceptibility of Soils. This is an index
damage to a pavement structure, frost heaving
test for estimating the relative degree of frost-
decreases the design life of a structure, which
susceptibility of a soil. This procedure cannot be
increases the cost of either maintenance or replace-
used to predict the actual amount of frost heave
ment (U.S. Army and Air Force 1985). There are
expected nor to predict the actual strength of the
three necessary conditions for frost heaving: frost-
soil after thaw.
susceptible soil, freezing temperatures, and the
Two sets of tests were conducted to assess the
presence of water.
present and future conditions of the subbase ma-
The frost-susceptibility of a soil depends on the
terial. In one case, the specimens were compacted
amount of fines passing the no. 200 (0.074-mm)
at the in-situ moisture content, then saturated.
sieve. In particular, Casagrande (1931) found that
These samples are referred to as saturated. This
he could index the frost-susceptibility of the soil as
case assumes that the subbase is saturated
a function of the material finer than 0.02 mm. He
because of the infiltration of water into the pave-
found soils having greater than 3% of material
ment system, which may occur in the later life of
finer than the 0.02-mm size appear to be highly
the pavement due to cracking. In the second case,
frost-susceptible. In addition to having a frost-
the specimens were compacted at the in-situ
susceptible soil, freezing temperatures and a near-
moisture content and no additional water was in-
by source of water are also required for frost heave
troduced during the testing. These samples are
to occur. Based on the initial assessment of the Til-
referred to as unsaturated. This case assumes that
con common granular fill material at CRREL, we
the pavement structure is not saturated, such as
found that the amount of fines passing the no. 200
in the beginning of the pavement life.
sieve was approximately 20%, of which approxi-
Eight samples were prepared for testing. These
mately 14% was finer than 0.02 mm (Fig. 1). The
samples were compacted at a density of 2.2 g/cm3
current COE frost-susceptibility criteria limits the
and a moisture content of 8%. The moisture-
amount of material finer than 0.02 mm to 3%. More
density data used were obtained from the NED
explanation on the laboratory results for the Tilcon
Geotechnical Engineering Division. The samples
common granular fill are presented later.
are 146 mm in diameter and 150 mm in height.
The compacted samples are confined in a split
LABORATORY TESTING
ring mold, which allows the samples to heave in
The Geotechnical Engineering Division at NED
an unrestricted manner.
requested CRREL to perform laboratory testing to
For the saturated case, four samples were com-
100
90
80
70
60
50
40
30
20
10
0
10
1
0.1
0.01
0.001
Particle Size (mm)
Figure 1. Grain size distribution for Tilcon common granular fill material.
2
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