Absolute Viscosity Test of Bitumen – ASTM D2171

The Absolute Viscosity Test measures the flow resistance of bitumen using a Cannon-Manning Vacuum Capillary Viscometer. This method is widely used for quality control of paving-grade bitumen.

1. OBJECTIVE

To determine the absolute viscosity of bitumen using the Cannon-Manning Vacuum Capillary Viscometer at a controlled temperature under a vacuum.

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2. APPARATUS

• Constant Temperature Bath (accuracy ±0.1 °C).
• Silicone Oil Bath (up to 150 °C) or Water Bath (up to 100 °C).
• Vacuum System (maintains ±0.05 cm Hg accuracy up to 30 cm Hg).
• Stopwatch (accuracy 0.5 sec).
• Cannon-Manning Vacuum Viscometers (Size 12 & Size 13).
• Viscometer Stand (for 6 tubes).

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3. PROCEDURE

1. Collect bitumen sample in a clean container.
2. Heat the sample to 135 ± 5.5 °C.
3. Pour into viscometer up to the fill mark (±2 mm of line E).
4. Allow sample to stand for 10 ± 2 minutes to release air bubbles.
5. Transfer viscometer into the bath maintained at 60 °C.
6. Connect the viscometer to vacuum pump and apply 30 cm Hg vacuum.
7. Start the stopwatch and record the time (T sec) for bitumen to flow from Mark G to Mark H.

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4. CALCULATION

Formula for Absolute Viscosity

Absolute Viscosity (Poises) = K × T

• K = Calibration factor of viscometer (Poises/sec)
• T = Flow time in seconds

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5. RESULTS

The absolute viscosity of the bitumen sample is reported in Poises at 60 °C under a vacuum of 30 cm Hg.