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Identification Tests - 14071_311
TESTS ON AGGREGATE - 14071_313

Engineering Aid 2 - Intermediate Structural engineering guide book
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that has a thermometer running through the stopper, as shown.  The  flask  and  contents  are  heated.  As  the temperature  rises,  distillate  is  given  off  in  the  form  of vapor. A condenser returns the vapor to liquid form, and the liquid (the distillate) is caught in a volumetric beaker. The   test   indicates   what   can   be   expected   in   the application and use of the materials. The distillation temperature ranges from  374°F to 680°F for RC asphalt cutbacks,  from  437°F  to  680°F  for  MC,  and  only  at 680°F for SC. Road tars are distilled at temperatures that range from 338°F to 572°F, and tar-rubber blends from 170°F to 355°F. The amount distilled is expressed as a percentage of the total. The residue is the difference between the distillate and the total. The percentages of distillation may be as little as 1 percent for tar-rubber distilled at 170°C (338°F) to as much as 59 percent when RC and MC cutbacks and tars are heated to the higher temperatures. Record the volume of bitumen remaining in the flask. If the residue is solid enough to be tested, it is subjected to the penetration test described later in this chapter. If it is solid enough for this test, the residue must be asphaltic cement, and the original material was either RC or MC. If it is not solid enough for penetration testing,  the  original  material  was  SC. Finally, you can determine the grade by calculating the percentage of bitumen and comparing it with the ranges previously given. Flash Point Tests The flash point  of a bitumen that contains a volatile distillate is the temperature at which it begins to give off ignitable vapor. The principal purpose of flash-point testing  is  to  determine  maximum  safe  mixing  and applying temperatures; however, these tests are an aid to identification as well. Referring again to table 13-6, you see that RC and MC have flash points below 175°F. MC-30 and SC-70 have flash points around 150°F, but the other grades of SC have flash points above 175°F. Testing for a flash point below 175°F is done with the tag open-cup equipment shown in figure 13-31. When testing for flash points above 175°F, use the Cleveland open-cup equipment shown in figure 13-32. When  using  either  of  these  testers,  you  need  to  follow the  procedures  described  in  NAVFAC  MO-330.  While there  are  important  procedural  differences,  flash-point testing using either equipment is similar in that you use the equipment to heat the test sample at a prescribed rate of  temperature  increase.  Then,  when  the  temperature reading on the thermometer nears the estimated flash Figure 13-31.—Tag open-cup flash point tester. point (table 13-6), you use an alcohol torch to begin passing a flame across the surface of the sample. The flash  point  is  reached  when  the  test  flame  produces  a distinct flicker or flash on the surface of the sample. At this point you read the thermometer and record the temperature. Penetration  Test Figure 13-33 shows an asphalt penetrometer that is used  to  determine  the  grade  of  asphalt  cement.  In performing  the  test,  the  needle  is  carefully  brought  to contact with the surface of the sample, then released so as to exert a pressure of 100 grams. The seconds after the needle is released, the distance it penetrated the sample is read, to the nearest 0.01 centimeter, on the penetrometer  dial.  The  reported  penetration  is  the average of at least three tests on the same material whose values do not differ more than four points between maximum  and  minimum.  Detailed  procedures  can  be found  in  NAVFAC  MO-330. 13-44







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