Study of Asphalt Viscosity Testing at 60 F

A cooperative study among six laboratories has defined test conditions to minimize differences in results obtained by different laboratories using four different instruments for determining the viscosity of asphalt at 60 F (16 C). The methods—cone-plate, falling plunger, sliding plate, and sliding plate at controlled rate of shear—are all currently proposed for the Book of ASTM Standards, Part 11.

The study shows that adhering closely to specified temperatures and times in sample preparation and using a uniform viscosity loading sequence will decrease the variability in results among laboratories and methods. A loading sequence going from low to high gives viscosities about 8 to 9 percent higher than those obtained with a reverse sequence. These results are the groundwork for a future study of precision.