SPECIFIC GRAVITY

Updated: Jul 16, 2020

AIM

To determine the specific gravity of fine-grained soil by density

bottle method as per IS: 2720 (Part III/Sec 1) - 1980.

PRINCIPLE

Specific gravity is the ratio of the weight in air of a given volume

of a material at a standard temperature to the weight in air of an

equal volume of distilled water at the same stated temperature.

APPARATUS

i) Two density bottles of approximately 50ml capacity

alongwith stoppers

ii) Constant temperature water bath (27.0 + 0.2 °C)

iii) Vacuum desiccator

iv) Oven, capable of maintaining a temperature of 105 to 110 °C

v) Weighing balance, with an accuracy of 0.001 g

vi) Spatula

PREPARATION OF SAMPLE

The soil sample (50 g) should if necessary be ground to pass

through a 2 mm IS Sieve. A 5 to 10 g sub-sample should be

obtained by riffling and oven-dried at a temperature of 105 to

110oC.

PROCEDURE

i) The density bottle along with the stopper, should be dried at

a temperature of 105 to 110 °C, cooled in the desiccator and

weighed to the nearest 0.001 g (W1).

ii) The sub-sample, which had been oven-dried should be

transferred to the density bottle directly from the desiccator

in which it was cooled. The bottles and contents together

with the stopper should be weighed to the nearest 0.001 g

(W2).

iii) Cover the soil with air-free distilled water from the glass

wash bottle and leave for a period of 2 to 3 hrs. for soaking.

Add water to fill the bottle to about half.

iv) Entrapped air can be removed by heating the density bottle

on a water bath or a sand bath.

v) Keep the bottle without the stopper in a vacuum desiccator

for about 1 to 2 hrs. until there is no further loss of air.

vi) Gently stir the soil in the density bottle with a clean glass

rod, carefully wash off the adhering particles from the rod

with some drops of distilled water and see that no more soil

particles are lost.

vii) Repeat the process till no more air bubbles are observed in

the soil-water mixture.

viii) Observe the constant temperature in the bottle and record.

ix) Insert the stopper in the density bottle, wipe and weigh

(W3 ).

x) Now empty the bottle, clean thoroughly and fill the density

bottle with distilled water at the same temperature. Insert the

stopper in the bottle, wipe dry from the outside and

weigh (W4 ).

xi) Take at least two such observations for the same soil.

REPORTING OF RESULTS



The specific gravity should be calculated at a temperature of

27 °C and reported to the nearest 0.01. If the room temperature is

different from 27 °C, the following correction should be done:-






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