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This test is done to determine the penetration of bitumen as per IS: 1203 – 1978. The principle is that the penetration of a bituminous material is the distance in tenths of a mm, that a standard needle would penetrate vertically, into a sample of the material under standard conditions of temperature, load and time. The apparatus needed to determine the penetration of bitumen is
ii) Water bath
iii) Bath thermometer – Range 0 to 44oC, Graduation 0.2oC
Bitumen should be just sufficient to fill the container to a depth of at least 15mm in excess of the expected penetration.
Procedure to determine the penetration of bitumen
i) Soften the bitumen above the softening point (between 75 and 100oC). Stir it thoroughly to remove air bubbles and water.
ii) Pour it into a container to a depth of at least 15mm in excess of the expected penetration.
iii) Cool it at an atmospheric temperature of 15 to 30oC for 11/2 hours. Then place it in a transfer dish in the water bath at 25.0 + 0.1oC for 11/2 hrs.
iv) Keep the container on the stand of the penetration apparatus.
v) Adjust the needle to make contact with the surface of the sample.
vi) Adjust the dial reading to zero.
vii) With the help of the timer, release the needle for exactly 5 seconds.
viii) Record the dial reading.
ix) Repeat the above procedure thrice.
REPORTING OF RESULTS
The value of penetration reported should be the mean of not less than three determinations expressed in tenths of a mm.