Question

As per current Viscosity Graded (VG) bitumen specifications in India (IS 73: 2006, Third revision) the Absolute Viscosity of bitumen using vacuum capillary tube viscometer is determined at _______ temperature.
1. 135°
2. 25°
3. 27°
4. 60°

Answer 1

Correct Answer - Option 4 : 60°

Explanation:

Viscosity:

• It is defined as the property of bitumen with which it resists flow due to internal friction.
   

There are two types of viscosity for any fluid:

1) Absolute/Dynamic viscosity:

• It is defined as the tangential force per unit area required to move one horizontal plane with respect to another horizontal plane at a unit velocity while maintaining unit distance apart within the fluid.

2) Kinematic viscosity:

• It is the ratio is dynamic viscosity to the density of the fluid.
   

Vacuum capillary tube viscometer:

• This test is suitable for a temperature range of 20 ± 0.1° C.
• The time required for the level of liquid to drop from one mark to another mark is measured nearest to one-fifth of a second.
• The result is valid only if the reading of two consecutive readings doesn't vary more than 1 percent.
• An average of not fewer than three readings is taken for the final result.
• The viscosity test results such as viscosity in poises 60° C and 300 mm mercury vacuum.
• Kinematic viscosity at 135° C also needs to be determined for the paving bitumen as specified in  IS: 73 - 2006  62.

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Properties of bitumen	Type of test
Viscosity	Viscometer test
Specific gravity	Pycnometer
Grade of bitumen / Hardness of bitumen	Penetration test
Softening test	Ring and ball test
Ductility	Standard briquette of bitumen