Determination of Absolute viscosity of bitumen by Cannon - Manning vacuum capillary viscometer

DETERMINATION OF ABSOLUTE VISCOSITY

 

Importance

In all bituminous works bitumen is required to be heated up to a definite temperature, so that the specific grade of bitumen may reach at its proper viscosity label, so that it can be mixed correctly with the aggregates to get a homogenous mix.

 

Definition of Absolute or Dynamic Viscosity of a Newtonian Liquid

It is defined as an internal friction, such that if a tangential force of one dyne (0.00001 N) acting on planes of unit area separated by unit distance of the liquid produces unit tangential velocity, the CGS unit for the viscosity of the liquid is 1 Poise (Dyne.Sec/Cm2).

 

Definition of Newtonian Liquid

A liquid in which the shear stress is directly proportional to the rate of shear strain. The constant ratio of shear stress to the rate of shear strain is defined as the coefficient of viscosity of the liquid. If this ratio is not constant then the liquid is called as a non-Newtonian liquid.

 

Objective

To determine the properties that may contributed towards the viscosity grade of bitumen.

 

Apparatus

(i) Cannon-Manning Vacuums Viscometer

(ii) Thermometer

(iii) Timing Devise (Stop watch)

 

Cannon - Manning vacuum capillary Viscometer

 

Sample Preparation

Heat the sample to a temperature less than 90°C for bitumen above their individual approximate softening point temperature awaiting it has become sufficiently fluid to pour. Pour about 20 ml into a suitable container and maintain it to a constant temperature of 135 ± 5.5°C

 

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