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The quality and the
properties of Bitumen has a great influence on the final
performance of the asphalt mixture and a number of tests can
be carried out upon its physical properties.
The penetration value, or
PEN, is used to provide an indication of the stiffness of
bitumen or tar.
Preparation of the sample
includes heating to about 110°C and ensuring that all water
has been removed by stirring. Once cooled the sample is then
reheated to 80-90°C above the sample softening point until
completely fluid and free of air bubbles and then allowed to
cool for 1 hour at room temperature.
Samples are then placed in
dishes provided and placed in a constant-temperature water
container for a specified time at 25°C.
The test can then be carried
out.
A needle is allowed to
penetrate the prepared sample under a 100g load applied
vertically for a timed duration (normally 5 seconds). The
scale is then read to give a penetration value. The test is
repeated 3 or more times to give a more accurate averaged
reading.
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