The specific gravity of soils composed of particles
smaller than the 4.75-mm (No. 4) sieve is determined by means of a pycnometer as per AASHTO T 100-15 test
method. For soils with particles larger
than the 4.75-mm (No. 4) sieve, the method outlined in AASHTO T 85 is
followed.
If the soil is
composed of particles both larger and smaller than the 4.75-mm (No. 4) sieve, the sample is first separated on
the 4.75-mm (No. 4) sieve. AASHTO T 85 test procedure is adopted on the particles retained on 4.75-mm (No. 4)
sieve and
AASHTO T 84 for particles passing 4.75-mm (No. 4) sieve, and a weighted average is calculated.
Volumetric flask having a capacity of atleast 100 mL or a stoppered bottle having of atleast 50 mL.
Thermostatically controlled drying oven capable of maintaining a temperature of 110 ± 5°C (230 ± 9°F).
Specific gravity test is carried out on either oven-dried soils or soils at its natural
moisture content.
Either a volumetric flask or a stoppered bottle is used as pycnometer for conducting the
tests.
At least 25 g of the oven-dry soil test sample is used when the volumetric flask
is used and at least 10 g of the oven-dry soil test sample is used when stoppered bottle
is used.
When the sample contains natural moisture, the mass of the oven-dried soil, W0 is determined at the
end of the test by evaporating the water in an oven
maintained at 110° ± 5°C (230 ± 9°F). When oven-dry samples are used, dry the sample for at least 12 h, or to
constant mass, in an oven maintained at 110° ± 5°C (230 ± 9°F), cool it to room temperature, record its mass,
and transfer it to the pycnometer.
Standardization of Pycnometer:
Step 1: Record the mass of dry pycnometer (Wf).
Step 2: Fill the pycnometer with distilled water and determine and record the mass of the pycnometer and water (Wa). Immediately, insert the thermometer into the water and determine its temperature Ti.
Calculation: To determine Wa at the desired temperature
Tx;
Wa@Tx=(Density of
water at Tx/Density of water at Ti) × (Wa@Ti -
Wf) + Wf.
Test Procedure:
Step 1: Add distilled water io the prepared soil sample transferred to volumetric bottle/stoppered flask in such a way that the water will cover the soil to a maximum of about three-fourths full in the volumetric flask or about one half full in the stoppered bottle.
Step 2: Remove entrapped air by either boiling the pycnometer gently for atleast 10 minutes or by applying a partial vacuum of 13.33 kPa (100 mm Hg).
Step 2: Fill the pycnometer to its calibrated capacity. Clean the outside of the pycnometer with a dry cloth and determine the mass of pycnometer and its contents (Wb) and the temperature (Tx) of the contents.
Specific Gravity of soil based on water at temperature Tx is calculated as;
where:
Tx=Temperature of the contents of the pycnometer when mass Wb was determined.
W0=Mass of oven dried soil sample in grams.
Wb = Mass of pycnometer filled with water and soil at temperature Tx.
Wa = Mass of pycnometer filled with water at temperature Tx (determined during the
calibration of pycnometer).
AASHTO T 100 requires the specific gravity values to be reported based on water at 20°C. Specific Gravity
of
soil based on water at temperature 20°C is calculated as;
Specific Gravity @ 20°C = K × Specific Gravity @ Tx°C.
where;
K = ratio of relative density of water at Tx°C to the relative density of water at
20°C = ρw/0.99820
The following Density of water-Temperature correlation as provided in ASTM D
854 has been used to calculate
the density of water, ρw (mg/litre) in this TransCalc tool.
SPECIFIC GRAVITY OF SOILS
Specific Gravity of Soils: Output
Test Temperature Tx:
Density of Water at Test Temperature Tx:
Density of Water at 20 °C:
Specific Gravity of Soils at Temperature Tx:
Specific Gravity of Soils @ 20°C:
Weighted Average Specific Gravity
| Specific Gravity | Mass Percentage |
|---|
Weighted Average Specific Gravity
Weighted Average Specific Gravity:
Report Section