Lesson 1/Learning Event 5
If an 800 or 3000 grade MC or SC is present though, it, too, may become sticky in a few minutes
since there is already such a small amount of cutter-stock in it. When such a viscous grade is
present, it is well to confirm the identification of the sample by a Prolonged Smear Test.
Generally, the MCs and SCs will penetrate through the paper while the RCs will not. You can
determine this by observing the back side of the paper.
In a Prolonged Smear Test, a thin smear is made on nonabsorbent paper and allowed to
completely cure. If the viscous cutback is an RE-3000, it will cure completely in about three
hours. When the spot has cured completely (the cutterstock has almost all evaporated) the smear
will be almost pure AC and will be hard and no longer sticky. If the viscous sample were an MC
or SC-800 or 3000, the spot would still be uncured and, therefore, very sticky, even after 24
hours, while the RC smear will have become a hard, glazed spot.
Heat-Odor Test. To differentiate MCs and RCs, their major differences must be emphasized.
Probably the main difference between the two lies in the fact that one has kerosene as its
cutterstock, while the other has been mixed with the diesel or slowly volatile oil class. Perhaps
some people can tell the difference by odor alone, at room temperature, but this is not always
reliable. Perform the heat-odor test to definitely establish the sample as an MC or SC. Apply
heat to the sample in order to drive off the kerosene if it is present, and to make it show up in the
form of an odor. It is best to heat the sample in a dosed container in order to capture the
escaping vapors, being careful not to apply too much heat. If the sample is an MC, it will have a
strong petroleum odor or a definite kerosene odor. On the other hand, should the sample be an
SC, no kerosene or petroleum odor will be detected. An SC may have a faint odor of hot motor
oil.
The ability to tell an RC from an MC and an SC from either is perhaps as important as any part
of field identification. With various cutback materials, construction methods vary widely, and
the properties of the final surface are likewise entirely different in many cases.
Field Penetration Test. Assuming that the unknown material mixes with a petroleum distillate,
and will not pour, it is established that it is an asphalt cement. Now, you must designate the
penetration grade of the asphalt and identify the sample as an asphalt cement either hard,
medium, or soft.
The field penetration test is performed to approximately fix the hardness of the asphalt, not to
pinpoint its exact penetration number. It is sufficient to know whether it falls in the hard,
medium, or soft groups. This is sufficient information for planning or in some cases actually
starting emergency construction for it indicates what construction methods and equipment will
be suitable and what approximate application of mixing temperature may be used.
To perform this test, attempt to push a sharpened pencil or nail into the container of asphalt (at
about 770) using a firm strong pressure. "Strong" is
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