EXPERIMENTAL RESULTS
The mean initial specific water contents and equilibrating-solution molalities
for the pastes are presented in Table 1. The specific liquid water contents of the
pastes as measured by pulsed NMR are presented in Tables 2 through 7, and their
liquid water contents are presented graphically in Figures 1 through 6.
For a given initial solution molality, the freezing curves of all pastes displayed
the roughly exponential decline in liquid-water content with decreasing tempera-
ture that is characteristic of freezing curves. The freezing curves of the sand pastes
were much less smooth than those for the kaolinite or montmorillonite pastes be-
cause of the much lower intensity of the peak signal from the sand samples. There
was no pronounced hysteresis between the cooling and heating curves for any of
the samples. For each of the three minerals, the freezing curves of the pastes that
had been equilibrated with 0.001-mol kg1 NaCl solutions were roughly coincident
with those that were equilibrated with 0.01-mol kg1 NaCl solutions. For each min-
eral, the freezing curves of the pastes initially equilibrated with 0.1-mol kg1 NaCl
solutions showed more liquid water at a given temperature than those equilibrated
with the lower-molality solutions. This shifting in the curves was likely the result
of the depression of the freezing points of the higher-molality solution. On a rela-
tive basis, this shift was most pronounced for the sand samples and least pronounced
for the kaolinite samples.
COMPARISON WITH THEORY
In this section we first detail how the capillary pressures and specific volumes of
the pore water solutions were calculated. These calculated values are then pre-
sented graphically and analyzed.
Calculation of the necessary
thermophysical properties
As stated earlier, the following thermodynamic quantities are needed to calcu-
late ice-solution capillary pressures in frozen porous media:
1. The mole fractions of the solute and
solvent
2. The freezing point of the solution
Table 1. Equilibrating solution mo-
phase in bulk
lalities and total specific water
masses for pastes frozen then
3. The molar entropy of ice
thawed in this study.
4. The molar entropy of the liquid solu-
tion
Initial
Initial
NaCl
specific water
5. The molar volume of the liquid solu-
molality
content
tion
(mol kg1)
(kg kg1)
Mineral
6. The temperature derivative of the sol-
Kaolinite
0.100 471
2.3425
ute chemical potential.
0.010 031 4
2.6703
0.001 002 98
2.1865
Mole fractions of the solute and solvent
Montmoril-
0.100 471
35.8610
A bulk H2ONaCl system under atmo-
lonite
0.010 031 4
31.5064
spheric pressure has a precisely defined eu-
0.001 002 98
12.5529
tectic point at 252 K (21.15C) and 5.14 mol
kg1. Below the eutectic temperature no liq-
Sand
0.100 471
0.2165
0.010 031 4
0.2146
uid phase remains, giving way to a mixed
0.001 002 98
0.2225
solid phase composed of hexagonal ice [rep-
7
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