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The Texas Highway Department has completed two years of extensive use of paving asphalts based on viscosity grading instead of penetration according to the requirements of the Asphalt Institute Study Specifications of January, 1963. No problems have been encountered in viscosity testing by either the state or producer. Only one minor producer out of 16 sources had any difficulty in meeting the viscosity limits. Variation in consistency at 77 F is much greater among producers under viscosity grading. Due to the lack of a needed softer or lower viscosity grade, viscosity grading has encouraged the use of much harder asphalts. Viscosity grading is considered to be still in the experimental stage and further evaluation is needed particularly in relation to durability.
pavements, asphalts, viscosity, penetration, grading (classifying), bituminous cements, sealing, durability, specifications
Chaffin, C. W.
Supervising chemical engineer, Materials and Tests Div., Texas Highway Dept., Austin, Tex