Determining the Specific Gravity of Soil - Soil Properties: Testing, Measurement, and Evaluation - page 61

Table 6-2 Recommended Mass for Test Specimen

Specimen Dry Mass (g)
When Using 250 mL Pycnometer

Specimen Dry Mass (g)
When Using 500 mL Pycnometer

Soil Type

SP, SP-SM 60 ± 10 100 ± 10

SP-SC, SM, SC 45 ± 10 75 ± 10

Silt or Clay 35 ± 5 50 ± 10

The actual step-by-step procedure is as follows (ASTM D 854-06 [1]):

(1) Pycnometer Mass —Using the same balance used to calibrate
the pycnometer, verify that the mass of the pycnometer is within
0.06 g of the average calibrated mass. If it is not, re-calibrate the
dry mass of the pycnometer.

(2) Method A—Procedure for Moist Specimens:

(2.1) Determine the water content of a portion of the sample in ac-
cordance with Test Method D 2216. Using this water content, cal-
culate the range of wet masses for the specific gravity specimen in
accordance with No. (1) under the Section “Test Specimen.” From
the sample, obtain a specimen within this range. Do not sample to
obtain an exact predetermined mass.

(2.2) To disperse the soil, put about 100 mL of water into the mixing
container of a blender or equivalent device. Add soil and blend. The
minimum volume of slurry that can be prepared by this equipment
will typically require using a 500-mL pycnometer.

(2.3) Using the funnel, pour the slurry into the pycnometer. Rinse
any soil particles remaining on the funnel into the pycnometer us-
ing a wash/spray squirt bottle.

(2.4) Proceed as described in (4).

(3) Method B—Procedure for Oven-Dried Specimens:

(3.1) Dry the specimen to a constant mass in an oven maintained
at 110 ± 5°C. Break up any clods of soil using a mortar and pestle.
If the soil will not easily disperse after drying or has changed com-
position, use Test Method A. [Method A shall be used for organic
soils; highly plastic soils; fine grained soils; tropical soils; and soils
containing halloysite.]

(3.2) Place the funnel into the pycnometer. The stem of the funnel
must extend past the calibration mark or stopper seal. Spoon the soil
solids directly into the funnel. Rinse any soil particles remaining on
the funnel into the pycnometer using a wash/spray squirt bottle.

(4) Preparing the Soil Slurry —Add water until the water level is
between 1 ⁄ 3 and 1 ⁄ 2 of the depth of the main body of the pycnometer.
Agitate the water until slurry is formed. Rinse any soil adhering to
the pycnometer into the slurry.