Specific Gravity of Bitumen

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The specific gravity of semi-solid bituminous material, asphalt cements, and soft tar pitches shall be expressed as the ratio of the mass of a given volume of the material at 25 °C to that of an equal volume of water at the same temperature. This test is done to determine the specific gravity of semi-solid bitumen road tars, creosote and anthracene oil as per IS: 1202 – 1978.

Apparatus

• Specific gravity bottle of 50 ml capacity, ordinary capillary type with 6 mm diameter neck or wide mouthed capillary type bottle with 25 mm diameter neck.
• Balance having least count of 1g.
• Thermometer.
• Water bath.

Procedure

1. The specific gravity bottle is cleaned, dried and weighed along with the stopper.
2. It is filled with fresh distilled water, stopper placed and the same is kept in water container for at least half an hour at temperature 27⁰C.
3. The bottle is then removed and cleaned from outside. The specific gravity bottle containing distilled water is now weighed.
4. The bituminous material is heated to a pouring temperature and is poured in the above empty bottle taking all the precautions that it is clean and dry before filling sample materials. The material is filled up to the half taking care to prevent entry of air bubbles.
5. To permit an escape of air bubbles, the sample bottle is allowed to stand for half an hour at suitable temperature cooled to 27⁰C and then weighed.
6. The remaining space in the specific gravity bottle is filled with distilled water at 27⁰C , stopper placed and is placed in water container at 27⁰C.
7. The bottle containing bituminous material and containing water is removed, cleaned from outside and is again weighed.

From the weights taken, the specific gravity of bitumen can be found out.

Observation:

Where, W1 = Weight of empty specific gravity bottle W2 = Weight of bottle+bitumen W3 = Weight of bottle +water W4 = Weight of bottle + water +bitumen

Result

Specific Gravity of bitumen =  ------------

Recommended Values

The specific gravity of pure bitumen ranges from 0.97 to 1.02. according to Indian Standard (BIS) minimum specific gravity of paving bitumen at 27°C shall be 0.99 for grades A25, A35, A45, A65, S35, S45 and S65 , 0.98 for A90 and S90 and 0.97 for A200 and S200. Read More: Asphalt, Bitumen and Tar – Types, Difference and Comparison