In accordance with IS: 1202-1978, the determination of the specific gravity of semi-solid bituminous materials, such as asphalt cements and soft tar pitches, involves expressing the ratio of their mass at 25°C to that of an equivalent volume of water at the same temperature. This test is conducted to determine the specific gravity of various substances, including bitumen road tars, creosote, and anthracene oil.
Apparatus
The laboratory equipment consists of a specific gravity bottle with a capacity of 50 ml. The bottle is available in two types: an ordinary capillary type with a neck diameter of 6 mm and a wide-mouthed capillary type with a neck diameter of 25 mm. A balance with a least count of 1g is also included in the set. A thermometer is provided to measure the temperature of the sample. Additionally, a water bath is available to ensure that the sample is at a constant temperature during the experiment.
Procedure
The process for determining the specific gravity of bituminous material involves several steps. First, the specific gravity bottle is thoroughly cleaned and dried, including the stopper. Then, it is weighed to establish a baseline measurement.
Next, the bottle is filled with fresh distilled water, and the stopper is inserted. The bottle is then immersed in a water container for at least 30 minutes at a temperature of 27°C to allow it to acclimate to the same temperature. After removing the bottle from the container, it is cleaned on the outside and reweighed with the water inside.
To fill the bottle with the bituminous material, the material is heated to a pourable temperature and carefully poured into the bottle, taking care to avoid introducing air bubbles. The bottle is filled halfway with the material and allowed to stand for 30 minutes at a suitable temperature to allow any air bubbles to escape. The bottle is then weighed again.
The remaining space in the bottle is filled with distilled water at a temperature of 27°C, and the stopper is inserted. The bottle is once again immersed in the water container and allowed to acclimate to the temperature for at least 30 minutes. After removing the bottle from the container, it is cleaned on the outside and reweighed with both the bituminous material and the water inside.
By analyzing the weights taken throughout the process, the specific gravity of the bituminous material can be determined.
Specific gravity of Bituminous Material
Observation:
The given context describes four different weights related to a specific gravity bottle, bitumen, and water. The weight of an empty specific gravity bottle is denoted as W1. The weight of the same bottle when it contains bitumen is denoted as W2. Similarly, the weight of the bottle when it contains water is denoted as W3, and the weight of the bottle when it contains both water and bitumen is denoted as W4.
To summarize, the context specifies four different weights associated with a specific gravity bottle, and each weight is determined based on what the bottle contains, whether it is empty, contains bitumen, water, or both water and bitumen.
Table for recording readings of specific gravity of bitumen
Result
Specific Gravity of bitumen = ————
Recommended Values
Bitumen is a viscous, black or dark-brown colored material that is commonly used as a binder in road construction. One of the important physical properties of bitumen is its specific gravity, which is a measure of its density compared to the density of water. The specific gravity of pure bitumen can vary between 0.97 to 1.02.
In India, the Bureau of Indian Standards (BIS) has set minimum specific gravity requirements for different grades of paving bitumen at a temperature of 27°C. For grades A25, A35, A45, A65, S35, S45, and S65, the minimum specific gravity required is 0.99. For grades A90 and S90, the minimum specific gravity required is 0.98. And, for grades A200 and S200, the minimum specific gravity required is 0.97.
Adhering to the BIS standards is important in ensuring that the quality of paving bitumen used in road construction is consistent and meets the necessary performance requirements.