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It is important to know the specific gravity of flyash as it can affect the quality of concrete. Determination of the specific gravity of flyash by Le-Chatelier flask:

Test Standard : IS 1727:1967

Test Apparatus

  1. Weighing Balance of accuracy 0.0002 gm.
  2. Le-Chatelier flask.
  3. Constant temperature water bath.
  4. Kerosene.

Test Method for specific gravity of flyash

  1. Maintained the laboratory at a temperature of 27±2 oC. Le chatelier flask shall be test filled with kerosene to a point on a stem between 0 and 1.0 ml mark.
  2. After pouring, if necessary, inside the flask above the level of the liquid shall be dried. .
  3. The flask shall be immersed in a constant temperature water bath maintained at room temperature for sufficient interval to avoid variation greater than 0.2 oC in the temperature of the liquid in the flask before recording the readings.
  4. The first reading shall be recorded (say R1, ml). A weighed quantity of flyash (about 64gms) shall then be introduced in small amounts in the flask at the same temperature as the liquid.
  5. Care will be taken to avoid splashing and to see that the cement does not adhere to the inside of the flask above the liquid.
  6. After all the cement has been introduced, the stopper shall be placed in the flask and the flask rolled in an inclined position or gently whirled in a horizontal circle so as to free the flyash from air until no further air bubbles rise to the surface of the liquid.
  7. If a proper a quantity of flyash has been added, the level of liquid will be in its final position at some point of upper series of the graduations.
  8. The final reading shall be recorded after the flask has been immersed in constant temperature water bath at room temperature (say R2, ml).

The difference between the initial and final readings represents the volume of liquid displaced by mass of pozzolana used in the test.

Test Result Calculation

Specific gravity of pozzolana (gm/cm3) = (Mass of the flyash (M, gm) / Final reading (R2)- Initial Reading (R1)

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