The following discussion applies to determination of bulk and apparent specific gravity. Bulk specific gravity is usually determined for the coarser materials that are retained on a No. 4 sieve. Large stones may be determined individually.

SAMPLE PREPARATION. Separate the sample on a No. 4 sieve, and use the material retained on that sieve for the test. Approximately 2 kg is required. Ensure the sample is a representative sample.

In preparing the sample, first wash the material to remove dust and coatings. Then immerse and soak the sample in water for 24 hr. Just before making the test, dry the sample to-a saturated-surface-dry condition. Do this by rolling the sample in art absorbent cloth to remove excess surface water. You may wipe large particles individually. When saturated-surface-dry, the surface may still appear damp. Take care to avoid excessive evaporation during the surface drying.

APPARATUS. Apparatus for the test is as follows:

Balance, 5 kg or larger, sensitive to 0.1 g Wire mesh basket, approximately 8 in. in diameter and 8 in. high; 2-mm (No. 6) or finer mesh

Suitable equipment for suspending the wire basket from the center of balance scale pan Thermometer, general laboratory

PROCEDURE. Perform the test in the following steps. You must complete the first step as quickly as possible after surface-drying the sample.

1. Determine the weight of the saturated-surface- dry sample and container. This weight minus the tare weight of the container is the weight of the saturated-surface-dry soil that you should enter in block 7e (fig. 15-33).

2. Determine the weight of the wire basket suspended in water. Record this weight in block 7g (fig. 15-33).

3. Place the sample in the basket and immerse the basket and sample in water. (Hang the basket from the balance and support the container so that the basket hangs freely in the water.) Read the weight and record it in block 7f (fig. 15-33). Sub-tract the weight of the empty basket suspended in water, Step 2 above, to determine the weight of the saturated soil in water. Record this weight in block 7h (fig. 15-33).

4. Measure and record the temperature of the water and soil. Enter this temperature in block 7b (fig. 15-33).

5. Determine the ovendry weight of the sample and enter the results in block 7k (fig.15-33). 

6. From the recorded information, you may now calculate both the bulk specific gravity (G~) and the apparent specific gravity (Ga) using the following formulas:

After determining the specific gravity of solids (G.) and the apparent specific gravity you can calculate the specific gravity of an en-tire soil sample (both larger and smaller than a No. 4 sieve). To do so, use the following formula:

Enter this composite specific gravity in the remarks block of the data sheet. Note, too, that you should also enter in the remarks block the percent of materials that is retained on, or passes, the No. 4 sieve.