viscosity of bitumen 60-70

Viscosity of bitumen 60/70 as per ASTM

acceptable range of viscosity for bitumen 60/70 is between 1600 to 2400 poise.

Viscosity: Definition and Importance

Viscosity is a measure of a fluid’s resistance to flow. In the context of bitumen, viscosity refers to its ability to flow under specific temperature and load conditions. It is an essential property that affects the workability, compaction, and durability of asphalt mixtures. Proper index ensures optimal coating and binding of aggregates, contributing to the overall strength and stability of the pavement.

Factors Affecting Viscosity

Several factors influence the viscosity of bitumen 60/70. Temperature is a critical factor as viscosity decreases with increasing temperature. This temperature-viscosity relationship is known as the viscosity-temperature susceptibility of bitumen. The presence of impurities, such as moisture and foreign materials, can also affect viscosity. Additionally, the rate and duration of shear stress applied to the bitumen impact its viscosity.

Measuring Viscosity

To determine the viscosity of bitumen 60/70, various methods are employed. The most common technique is the Brookfield viscometer, which measures the resistance to flow under controlled temperature and shear conditions. It is reported in units of Pascal-seconds (Pa·s) or poises (P), depending on the measurement system used.


Bitumen is graded based on its viscosity, which helps determine its suitability for specific applications. The viscosity grading of bitumen 60/70 ensures consistency and quality control. The grading system provides information on the penetration value and viscosity range, aiding engineers and contractors in selecting the appropriate bitumen for their projects.