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It measures the hardness or softness of bitumen by measuring the depth in
tenths of a millimeter to which a standard loaded needle will penetrate
vertically in 5 seconds.
BIS had standardised the equipment and test procedure.
The penetrometer consists of a needle assembly with a total weight of 100g and a
device for releasing and locking in any position.
The bitumen is softened to a
pouring consistency, stirred thoroughly and poured into containers at a depth
at least 15 mm in excess of the expected penetration.
The test should be
conducted at a specified temperature of 25 C.
It may be noted that
penetration value is largely influenced by any inaccuracy with regards to
pouring temperature, size of the needle, weight placed on the needle and the
test temperature.
A grade of 40/50 bitumen means the penetration value is in
the range 40 to 50 at standard test conditions.
In hot climates, a lower
penetration grade is preferred.
The Figure 0.1 shows a schematic Penetration Test setup.
Figure 1:
Penetration Test Setup
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