Why to do Viscosity test of bitumen?
The viscosity of bitumen and tar in road construction practice is based on the arbitrary test result obtain With orifice type viscometer. This test is carried Out to determine the viscosity of bitumen and tar which remain fluid under the specified temperature of the test.
Specified Conditions for Viscosity Test
- Apparatus: orifice type viscometer
- Diameter 4 & 10 mm
- Temperature: 25° c and 40°c
- Quantity of bitumen: 50 cc
The standard orifice viscometer test measures the time in second for a 50 ml of binder Liquid to flow from a cup through a standard orifice under the above specific Conditions.
- Sieve of 150 micron
- Digital Clock
- Digital thermometer
- 60 ml receiving Flask
- Temperature Regulator
- Savbolt viscometer
- Emulsion Sample
- Oil Tube
- Water bath
Procedure for Viscosity test of bitumen
First of all pass the emulsion sample with the help of 150-micron sieve and pour it to the beaker.
Now, pour the filtered emulsion to the Savbolt viscometer’s tube.
(Viscometer machine is cylinder like structure and consist of a hollow tube at the center.)
The hollow tube of viscometer is filled with sample and exterior part with water for water bath.
Cover lid of viscometer and join two thermometers to measure the temperature of the sample and water as well.
Now, stirr the sample with the help of movable lid of viscometer and make the temperature of sample up to 50 degree Celsius.
Now. once the temperature reaches 50 degree, the sample should be taken out through lower hole of the viscometer.
The sample should be collected in 60 ml receiving Flask.
Take a stopwatch and note the time required to fill the flask up to a horizontal line as shown in the figure above.
Yes, we have completed, the time taken to fill the sample up to the horizontal line of flask is the value of viscosity of the bitumen.
Now note down in format,
Format for Viscosity test of bitumen
Types of emulsion :-
Final Temperature of Sample :-
Time taken to fill flask :-
Significance for Viscosity test of bitumen
The viscosity of bitumen binder is its most important physical characteristic, it defines Inverse of fluidity and is a measure of resistance to flow.
The right choice of bitumen can be made after Owing its Viscosity because of the following reasons: .
The degree of fluidity of the binder at the application temperature determines the quality of mixing binder of lower Viscosity results in lubrication only.
Binder of reasonable Viscosity results in the uniform film (coat). It results in a heterogeneous mixture because of less resistance for mixing.
Binder of higher viscosity requires more comparative effort and may result in a heterogeneous mixer. premix with a higher Viscosity binder is not easily workable.
Precaution while testing bitumen
The temperature should be noted carefully.
Standard size of flask should be used.
Emulsion should be filled in viscometer up to the the lower tube.
Make sure no sample should be out of flask while extracting emulsion from viscometer.
The horizontal line of the flask should be noted carefully to take accurate time of filling.