Lesson 1/Learning Event 5
meant to be perhaps a 10 pound pressure. If only a slight penetration is made, with considerable
difficulty, a hard asphalt cement is present. If the penetration is made without great difficulty-
slowly, perhaps, but positively, and to any desired depth, probably a medium asphalt cement is
present. If the penetration is made with ease, the asphalt cement is naturally in the high
penetration scale (a soft AC). Even the highest penetration grade will not pour at 77 or even
immediately deform, if the container it is in is tilted.
Stone Cutting Test. Where a material has been tested and found to be an emulsion, it is
necessary to know whether it is a Rapid Setting emulsion, termed as a "non-mixing" grade, or a
Medium or Slow Setting emulsion, the latter two types being termed "mixing" grade emulsions.
It is important to know which type is present since the uses of the mixing and non-mixing types
vary greatly. The test performed to distinguish between these two kinds of emulsions is the
stone coating test.
This test consists of taking a handful of damp sand and adding to the sand a small amount of
emulsion (estimate about 6 to 8 percent by weight) and attempting to mix the two materials.
Care should be exercised not to add so much emulsion to the sand as to saturate it.
A Rapid Setting emulsion will "break" so quickly it will not be possible to mix it with sand. It
breaks immediately, gumming up the mixing spoon and the aggregate with asphalt cement. On
the other hand, if the unknown sample is a Medium or Slow Setting emulsion, the material, when
added to the damp sand, will mix easily and coat all the particles completely, as well as the
mixing spoon, with a uniform coating of asphalt.
It is not necessary to attempt to determine the viscosity grade of an emulsion since there are so
few grades. Simply find out whether the emulsion is a mixing or non-mixing grade. This is
sufficient identification for field conditions. Likewise, by means of field identification, it is not
necessary to distinguish between an MS and an SS, since both are mixing grades, and largely
used for the same jobs.