added to the emulsion up to proportions of 1:3 for use in slurry seal coats. Because emulsions contain water, they  have  certain  disadvantages.  During  freezing weather the emulsions can freeze, and the components can  separate.  Also,  emulsions  are  difficult  to  store  for extended  periods  because  they  tend  to  “break”  even  in unopened drums. When emulsions are shipped, the water in the mixture takes up valuable space, which could  be  used  to  transport  hard-to-obtain  materials. FIELD IDENTIFICATION OF BITUMENS A  fairly  accurate  identification  of  bituminous materials is necessary to make decisions regarding types and methods of construction, types and quantities of equipment, and applicable safety regulations. Field tests must  be  performed  to  identify  a  bituminous  material  as asphalt  cement,  asphalt  cutback  asphalt  emulsion,  road tar, or road-tar cutback and to field-identify the grade. Field  identification  of  bitumens  is  summarized  in figure  13-29. Test for Solubility The  first  procedure  in  the  identification  of  an unknown bituminous material is to determine whether it  is  an  asphalt,  an  emulsion,  or  a  tar.  Bituminous materials may be differentiated by a volubility test. To perform  the  test,  you  simply  dissolve  an  unknown sample (a few drops, if liquid, or enough to cover the head of a nail, if solid) in any petroleum distillate. Kerosene, gasoline, diesel oil, or jet fuel is suitable for this test. One or more of these distillates is usually available to the EA in the field Since asphalt is derived from  petroleum,  it  will  dissolve  in  the  petroleum distillate.  If  the  material  is  an  emulsion,  it  can  be detected  by  the  appearance  of  small  black  globules,  or beads,  which  fall  to  the  bottom  of  the  container.  Road tar will not dissolve. If the sample is an asphalt, the sample-distillate  mix  will  be  a  dark,  uniform  liquid  If it is a road tar, the sample will be a dark, stringy, undissolved mass in the distillate. You can make a check by spotting a piece of paper or cloth with the mix. If no stain results, the material is a tar; however, if a brown to black stain appears, then it is asphalt. The volubility test provides  a  positive  method  of  identification. Tests for Asphalt Cement When  the  volubility  test  determines  that  the bituminous  material  is  an  asphalt  you  should  then perform a  pour test to  distinguish  whether  the  asphalt material  is  asphalt  cement  or  asphalt  cutback.  In  this  test you place a small sample of asphalt into a container and attempt to pour it at mom temperature (77°F). Since asphalt cement is a solid at room temperature, it will not pour. Even the highest penetration grade (200 to 300) will  not  pour  or  immediately  deform.  The  thickest asphalt   cutback,   however,   will   start   to   pour   in 13 seconds at a temperature of 77°F. The   various   grades   of   asphalt   cement   are distinguished by their hardness, as measured by a  field penetration test. For  purposes  of  field  identification, the consistency of asphalt cement maybe approximated at  room  temperature  as  hard  (penetration  40-85), medium (penetration 85- 150), and soft (penetration 150-300. These limitations are flexible, as complete accuracy   is   not   essential.   You   can   make   an approximation of the hardness while in the field by attempting to push a sharpened pencil or nail into the asphalt at 77°F with a firm pressure of approximately 10  pounds.  When  the  pencil  point  penetrates  with difficulty or breaks, the asphalt cement is hard. When it penetrates  slowly  with  little  difficulty,  the  asphalt cement  is  medium.  If  the  pencil  penetrates  easily,  the asphalt cement is a high penetration or soft grade. Tests for Asphalt Cutbacks In  addition  to  distinguishing  asphalt  cement  from asphalt cutback as discussed above, the pour test will identify the viscosity grade of the cutback at a room temperature of 77°F. After the pour test, the approximate viscosity grade of the cutback is known, but the actual type (RC, MC, SC) is not. Asphalt cement is “cut back” with a petroleum distillate to make it more fluid. If the material does not pour, it is an asphalt cement. If it pours, it is a cutback or emulsion. It has been found that the cutbacks of a given viscosity grade will pour like the following  substances: 3 0- 7 0- 250- 800- 30 0 0 - A smear Water Light  syrup syrup Molasses Barely  deform test is used to distinguish an RC cutback from an MC or SC cutback.  The test is based on the fact that RCs are cut back with a highly volatile material (naphtha  or  gasoline)  that  evaporates  rapidly.  To perform the test, you simply apply a thin smear of the material on a nonabsorbent surface, such as a piece of 13-41