Spesific Gravity

O: 3/X-2/GTK/11

Objective:
This test is done to determine the specific gravity of fine-grained soil by density bottle method . 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.

Equipment:

1. Two density bottles of approximately 50 ml capacity along with stoppers
2. Constant temperature water bath (27C + 0.2C)
3. Vacuum desiccator
4. Oven, capable of maintaining a temperature of  105C  to 110C
5. Weighing balance, with an accuracy of 0.001g
6. Spatula

Preparation of Sample
The soil sample (50g) should if necessary be ground to pass through a 2mm IS Sieve. A 5 to 10g sub-sample should be obtained by riffling and oven-dried at a temperature of 105 to 110oC.

Procedure to Determine the Specific Gravity of Fine-Grained Soil

1. Pray before starting practice
2. The density bottle along with the stopper, should be dried at a temperature of 105 to 110oC, cooled in the desiccator and weighed to the nearest 0.001g (W1).
3. 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 0.001g (W2).
4. Cover the soil with air-free distilled water from the glass wash bottle and leave for a period of 2 to 3hrs. for soaking. Add water to fill the bottle to about half.
5. Entrapped air can be removed by heating the density bottle on a water bath or a sand bath.
6. Keep the bottle without the stopper in a vacuum desiccator for about 1 to 2hrs. until there is no further loss of air.
7. 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.
8. Repeat the process till no more air bubbles are observed in the soil-water mixture.
9. Observe the constant temperature in the bottle and record.
10. Insert the stopper in the density bottle, wipe and weigh(W3).
11. 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 ).
12. Take at least two such observations for the same soil.
13. Pray after completion

Pictures;

 

Erlenmeyer

 

 a set of spesific gravity equipment

 

Balance

Reporting of Results

Note:

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:-
G’ = kG
where,
G’ = Corrected specific gravity at 27 C
k = [Relative density of water at room temperature]/ Relative density of water at 27 C.

Maintenance:
Clean the equipments after the experimen is finished