The viscosity of asphalt binder at high manufacturing and construction temperatures (generally above 275°F (135°C)) is important because it can control the following:
Pumpability. The ability of the asphalt binder to be pumped between storage facilities and into the HMA manufacturing plant.
Mixability. The ability of the asphalt binder to be properly mixed with and to coat aggregate and other HMA constituents in the HMA manufacturing plant.
Workability. The ability of the resultant HMA to be placed and compacted with reasonable effort.
The Rotational Viscometer (RV) (left) is used to determine the viscosity of asphalt binders in the high temperature range of manufacturing and construction. This measurement is used in the Superpave PG asphalt binder specification. The RV test can be conducted at various temperatures, but since manufacturing and construction temperatures are fairly similar regardless of the environment, the test for Superpave PG asphalt binder specification is always conducted at 275°F (135°C).
Pavement interactive-RV has a detail introdution on this test method. Test discription, basic procedure, results analysis can be found in that page.
AASHTO T 316 and ASTM D 4402: Viscosity Determination of Asphalt Binder Using Rotational Viscometer.