Viscosity is simply a measure of a fluid’s resistance to flow and is described by the following equation:
Asphalt binder viscosity is typically measured at 60° C (140° F) because it approximates the maximum HMA pavement surface temperature during summer in the U.S.
The basic absolute viscosity test measures the time it takes for a fixed volume of asphalt binder to be drawn up through a capillary tube by means of vacuum, under closely controlled conditions of vacuum and temperature (ASTM, 2003 ). Although absolute viscosity is an improvement over the penetration test, it still only measures viscosity at one temperature and thus does not fully characterize an asphalt binder’s consistency over the expected range of construction and service conditions.
Standard Test Methods
- AASHTO T 202 and ASTM D 2171: Viscosity of Asphalts by Vacuum Capillary Viscometer
- American Society for Testing and Materials (ASTM). (2003). Annual Book of ASTM Standards, Volume 04.03, Road and Paving Materials; Vehicle-Pavement Systems. ASTM International. West Conshohocken, PA.↵