Rotational Viscometer 431s25

Experiment number: 6 Experiment name: Rotational viscometer test. Aim of experiment: To determine the viscosity of bitumen at different temperature using rotational viscometer. Relevant codes: ASTM D4402/D4402M-13, Standard test method for viscosity determination of asphalt at elevated temperatures using a rotational viscometer. Relevance and importance: Bitumen is a thermo-plastic material whose viscosity varies with variation in temperature. From the point of view of pavement engineering, the viscosity of bitumen should be low enough to properly coat the aggregate particles at the mixing temperature and also maintain an adequate viscosity to undergo proper compaction at the compaction temperature. To ensure that the binder fulfils this criteria, viscosity measurements are taken at varying temperature and a plot of viscosity vs. temperature is made. From this plot temperature corresponding to suitable viscosity can be determined. Test description: In this test, after the equipment warms up properly, the torque is set to in between 10% to 98%. The bitumen sample is heated and poured into the sample chamber and the sample chamber is inserted into the viscometer. The test sample is allowed to equilibrate for 10 min at the test temperature. After that the test is started, once the rotations stabilise, viscosity reading are noted down. Apparatus required: 1. Rotational viscometer. 2. Temperature-Controlled Thermal Chamber Heater. 3. Sample Chambers, reusable or disposable. 4. Temperature Controller, capable of maintaining the specimen temperatures to ±1.0°C. 5. Balance, thermometer. Procedure: For conducting the test, this steps are followed: 1. The instrument is allowed to warm up properly for at least 5 min. 2. Bring the temperature of the equipment to the desired test temperature.

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An apparatus-measuring geometry is selected that will develop a resisting torque between 10 % and 98 % of the instrument capacity at the selected speed. Accuracy

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increases with increase in torque. The sample chamber is preheated and the selected apparatus-measuring geometry

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until temperature equilibrium has been obtained for at least 15 min. Fill the sample chamber with specified amount of bitumen sample, taking care not to

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overfill. The preheated apparatus-measuring geometry is inserted into the liquid in the

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chamber, and coupled to the viscometer. The asphalt sample is brought to the desired test temperature and allowed to

equilibrate for 10 min. 8. Then the test is began, keeping the resisting torque in between 10% to 98%. 9. For torque readings above 98 % of the instrument capacity, decrease the speed of rotation of the apparatus-measuring geometry and for torque reading below 10 % of the instrument capacity at the highest test temperature, increase the speed of rotation of the apparatus geometry. 10. Viscosity or the torque is measured at 1min intervals for a total of three minutes after the readings stabilizes. Observation table: Binder used for testing is

SL. No

Temperature, °C

1 2 3

Calculations:

Viscosity readings, Observed

Mean

Torque, % Observed

Mean

Mean viscosity,

Result and discussions: