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The thin-film oven test (TFO), ASTM D 1754-69, is well established and functional; however, it requires 5 h exposure time. The rolling thin-film oven test (RTFO), ASTM D 2872-70, is also functional. Its precision is better, and it is faster to do. Unfortunately, the two exposures differ enough so they should not be used interchangeably without separate specification limits for each test. A good solution to this dilemma would be another oven exposure which has the advantages of the RTFO (that is short exposure time and high precision) and which, at the same time, affects asphalts in the same way as the TFO. This has been substantially accomplised by converting the RTF oven from a convection oven to a forced-draft oven. The added circulation causes more volatile loss to occur. This rolling thin-film circulation (RTF-C) oven test not only gives exposures very close to the well-accepted TFO; but it is just as fast as the RTFO to perform. It is suggested that this new oven exposure be considered as a replacement for the RTFO and interchangeable with the TFO in specifications.
asphalt, oxidation, specifications, durability, thin films, bitumens, viscosity, viscosity tests
Senior research associate, Chevron Research Company, Richmond, Calif.