would have had very limited evaporation and diffusion
potential. We believed that the sintering process would
be essentially complete at the time of fabrication;
however, we produced three parallel series of bricks
and stored them at three different temperatures (10,
15, and 25C) for four time periods (1, 5, 10, and
20 days) to determine what effect, if any, time and
temperature would have on CFG ice.
We produced a total of six bricks for each storage
period and temperature. The 15 and 25C
temperature series were kept in chest freezers, while
the 10 series was kept in the coldroom and was
therefore subject to a certain amount of temperature
variation because of other activities in the coldroom,
Figure 1. Steel form used to produce
such as sample preparation, microscopic work, and so
compacted snow/ice samples.
forth. Strength measurements were made after a total
storage time of 1, 5, 10, and 20 days. The pond and
after its density had been determined and recorded.
lake ice used as control was also stored in the coldroom
Most of the bricks in this study were made using 6.87
until we were ready to cut it into test samples.
MPa pressure held for 30 seconds. The time to reach
maximum pressure was about 60 seconds in all cases.
PART 2. THE TEST PROGRAM
Gross appearance and behavior
In appearance the compacted material was
We conducted four test series in this study as
uniformly white and completely opaque, the bubbles
follows:
too small to be seen with the naked eye. During sample
1) Unconfined compressive strength tests. This
preparation either with bandsaw or handsaw there was
series of tests was done to evaluate the load-bearing
little splintering. The only evidence of flaws was an
potential of CFG ice. In addition, since this test has
occasional tendency to split horizontally into two or
been performed on a wide variety of different ice types,
three slabs (normal to the stroke). This may have been
it allowed us to compare the CFG ice with other,
an artifact of the removal from the mold. It usually
frequently studied, types of ice.
happened immediately after fabrication, although we
2) Flexural strength tests. The flexural strength of
did lose one test brick that split as we were about to
ice is usually studied to gain insights into the strength
cut it at test time. Even immediately after the bricks
of a floating ice sheet as it applies to the load-bearing
had been removed from the mold, the material seemed
capacity of the sheet, forces on structures, ridge
strong and hard. It will be referred to in this report as
building processes, and so forth. We measured the
"compacted fine-grained (CFG) ice."
flexural strength of CFG ice first to get an idea of its
effectiveness as a pavement over a relatively soft base
Storage of bricks used in strength tests
(snow, for example) and again to compare the CFG
Many researchers have demonstrated that the
ice with other, frequently studied, types of ice.
strength of compacted snow depends on its density and
3) Effect of final compaction pressure and duration
the duration and temperature of sintering (Butkovich
of final load. This series was to determine whether
1962, Ramseier and Sander 1966, Abele et al. 1968).
pressures as high as 7 MPa were required and what
All of these studies dealt with lightly compacted snow
influence the duration of the final load had on the ice
with high porosity and considerable air circulation. In
density.
these circumstances the main processes driving the
4) Effect of storage in a thermal gradient. This test
sintering of the material are evaporation, diffusion, and
was to determine whether the CFG ice would weaken
condensation. The CFG ice used in this study, however,
or recrystallize in a thermal gradient.
had densities ranging from 800 to 890 kg/m3. A density
of 820 kg/m3 is thought to mark the transition between
Uniaxial compressive testing
compacted snow and ice, where pores in the material
The measured strength of ice is affected by many
no longer communicate with one another (Abele and
factors, including grain size, type, and orientation;
Gow 1976), so most samples were above the density
temperature; density; strain rate; inclusions; and
of pore close-off and the few that fell beneath this
salinity. All of these aspects have been studied for
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