Table 15-3.-Relative Density of Water and Correction Factor (K) at Various Temperatures
boiling may cause material to be boiled out of
Weight of the flask filled with water
the flask.
7. After all air has been exhausted, and the
flask and contents have cooled, add more
de-aired, distilled water until the flask is filled
to the ring marked on the neck. To ensure
all air is exhausted, a second boiling may be
necessary.
8. Next, dry the outside of the flask and
any moisture above the water surface inside the
flask.
9. Weigh the flask and contents to the
nearest 0.01 g, and record the information in
block 6j (fig. 15-33). This is Wbws.
10. Immediately after weighing, stir the
suspension to assure even temperature distribu-
tion. Immerse a thermometer to mid-depth of the
flask, and read the temperature of the soil-water
suspension. Record this temperature in block 6C
(fig. 15-33).
11. Finally, with the data entered on the data
sheet, compute the specific gravity using the
following formula:
only, at test temperature. You can
get this value from a calibration
curve, or table, previously prepared
for the flask used in the test.
Weight of the flask, water, and
sample at test temperature
Bulk and Apparent Specific Gravity
The following discussion applies to determina-
tion of bulk and apparent specific gravity.
Bulk specific gravity is usually determined for
the coarser materials that are retained on a
No. 4 sieve. Large stones may be determined
individually.
SAMPLE PREPARATION.— Separate the
sample on a No. 4 sieve, and use the material re-
tained on that sieve for the test. Approximately
2 kg is required. Ensure the sample is a represen-
tative sample.
In preparing the sample, first wash the
material to remove dust and coatings. Then
immerse and soak the sample in water for 24 hr.
Just before making the test, dry the sample to-a
saturated-surface-dry condition. Do this by
where:
w,
=
K
=
rolling the sample in art absorbent cloth to remove
excess surface water. You may wipe large particles
individually. When saturated-surface-dry, the sur-
Dry weight of the sample
face may still appear damp. Take care to avoid
excessive evaporation during the surface drying.
Correction factor based on the
APPARATUS.— Apparatus for the test is as
density of water at 20°C. You can get
follows:
this factor from table 15-3 by select-
Balance, 5 kg or larger, sensitive to 0.1 g
ing the correction factor that cor-
Wire mesh basket, approximately 8 in. in
responds to the temperature obtained
diameter and 8 in. high; 2-mm (No. 6) or finer
in Step 10, above.
mesh
15-28
