Determining the Specific Gravity of Soil - Soil Properties: Testing, Measurement, and Evaluation - page 65

(3) Calculate the specific gravity of soil solids at 20°C as follows:

G 20 ° C K # G t (6-5)

where:
K the temperature coefficient given in Table 6-1.

(4) For soil solids containing particles greater than the 4.75-mm
(No. 4) sieve for which Test Method C 127 was used to determine
the specific gravity of these particles, calculate an average specific
gravity. Test Method C 127 requires the test be performed at 23 ±
1.7°C and does not require the specific gravity data to be corrected
to 20°C. Use (3) to correct this measurement to 20°C. Use the fol-
lowing equation to calculate the average specific gravity:

1

G avg @20° C (6-6)

R
100 # G 1@20 ° C

P
100 # G 2@20 ° C

where:
R the percent of soil retained on the 4.75-mm sieve,
P the percent of soil passing the 4.75-mm sieve,
G 1@20°C the apparent specific gravity of soils retained on the
4.75-mm sieve as determined by Test Method C 127,
corrected to 20°C
G 2@20°C the specific gravity of soil solids passing the
4.75-mm sieve as determined by these test methods
(Equation 6-5).

A laboratory test was conducted according to the procedure described
previously. The following data were obtained:

NUMERICAL
EXAMPLE

[A] Calibration of Pycnometer

Mass of pycnometer, M p = 158.68 g
Mass of pycnometer plus water at calibration temperature,
M pw,c = 656.43 g
Temperature of water at calibration, T c = 24°C

[B] Specific Gravity Determination

Mass of pycnometer plus water and soil at test temperature T t ,
M pws,t = 718.52 g
Temperature of contents of pycnometer when M pws,t was
determined, T t = 22°C
Mass of evaporating dish, M d = 289.14 g
Mass of evaporating dish plus oven-dried soil, M ds = 387.15 g