IS: 1206 (Part 2) Method for Testing Tar and Bitumen Content: Determination of Absolute Viscosity

test equipment

To measure the absolute viscosity of viscosity graded floor bitumen, the following test equipment is required (IS:73-2006) at 60 C as per IS:1206 (Part 2) (same as .) ASTM D 2171), which uses a vacuum capillary viscometer. It should be noted that any other viscometer like rotational viscometer cannot be used to measure absolute viscosity at 60C because bitumen is non Newtonian in nature at this temperature.

Specify the following requirements when receiving quotations. Although the Asphalt Institute vacuum viscometer and modified Kopper vacuum viscometer may also be used, the following refers only to the Canon–Manning vacuum viscometer.

Absolute viscosity test equipment conforming to IS:1206 (Part 2) Method for testing tar and bitumen content: Determination of absolute viscosity with the following components:

  1. constant temperature bath Bath suitable for immersion of at least 6 vacuum capillary viscometer tubes with a digital temperature controller. The accuracy of the temperature in the bath should be +/- 0.1 C throughout the bath.
  2. silicone bath oil 150 c. suitable to
  3. vacuum system – Capable of maintaining a vacuum including 30 cm of mercury and within +/- 0.05 cm of desired level. The system will include vacuum pump, moisture trap, vacuum regulator, manometer with electronic controller, bleed valve, all interconnecting tubing/piping, and other accessories required to complete the vacuum system.
  4. thermometer for bath – Mercury in glass, range 37.8 to 82 C, and graduation 0.2 C.
  5. timing device , a closed clock Or a stop clock capable of reading up to second.

    Pic-1 Viscosity Test of Bitumen
    Pic-1 Viscosity Test of Bitumen

  6. Cannon-Manning Vacuum Viscometer– With manufacturers calibration certificate, viscometer holder and silicone cork. Size 12 and size 13 (one in each) [Size 12 is suitable for testing VG-10 and Size 13 is suitable for testing VG-20, VG-30, and VG-40 bitumen.]
  7. viscometer stand – To hold 6 viscometers.
  8. Installation of quoted equipment in customer’s laboratory and operational training.

pay attention: Only cannon-manning viscometer At present the tubes need to be imported, rest of the equipment like Bath and Vacuum system are available in India.

Pic-2 Viscosity Test of Bitumen
Pic-2 Viscosity Test of Bitumen

However, be aware that water bath and vacuum control systems manufactured in India do not give the required accuracy and consistency for many tests (viscosity is very sensitive to small changes in temperature and vacuum level). Try them out carefully before buying them. If not satisfactory, these systems may have to be imported.

Testing Process

Sample preparation:

Pic-3 Viscosity Test of Bitumen
Pic-3 Viscosity Test of Bitumen
  1. Heat the bitumen sample to a temperature higher than about 90 C. softening point until enough liquid (such as motor oil) has formed for easy pouring (PIC-1,
  2. Pour about 20 ml into a suitable container (pic-2) and maintain at a temperature of 135 +/- 5.5 °C, stirring occasionally to allow the trapped air to escape.
  3. Pour the hot bitumen into the Canning–Manning vacuum viscometer through the large diameter filling tube A so that the bitumen is within +/- 2 mm of the fill line E. Place the charged viscometer in the oven or bath at 135 +/- 5.5. C for a period of 10 +/- 2 min to allow large air bubbles to escape.

    Pic-4 Viscosity Test of Bitumen
    Pic-4 Viscosity Test of Bitumen


  1. Maintain the temperature of the test bath at 60 +/- 0.1 C. Hold the charged viscometer vertically in the test bath with the help of a holder so that the top time mark is at least 2 cm below the surface of the bath liquid (PIC-3,
  2. Install a vacuum of 30 +/- 0.05 cm Hg in the vacuum system and connect to the viscometer with the valve closed. After the viscometer has been in the bath for 30 +/- 5 minutes, open the valve and allow the bitumen to flow into the viscometer.

    Pic-5 Viscosity Test of Bitumen
    Pic-5 Viscosity Test of Bitumen

  3. Measure the time (within +/- 0.5 seconds) required for the leading edge of the meniscus to pass between successive pairs of time marks (pic-4 and 5,
  4. Considering the identity of the pair of timing marks, report the first flow time that exceeds 60 seconds between a pair of timing marks.


calculate (PIC-6) and report the absolute viscosity in three significant figures as follows:

Pic-6 Viscosity Test of Bitumen
Pic-6 Viscosity Test of Bitumen

Viscosity in Poise = K t


K = calibration factor in poses per second supplied with the viscometer tube for the pair of timing marks where the flow time exceeded 60 seconds.

t = flow time in seconds


Report test temperature and vacuum level with viscosity test results such as viscosity @ 60 C in pois and 300 mm of mercury vacuum.

Pic-7 Viscosity Test of Bitumen
Pic-7 Viscosity Test of Bitumen

pay attention: The kinematic viscosity at 135C should also be determined for the paving bitumen as specified. IS: 73-2006, At this temperature, bitumen flows easily, so no vacuum is needed. Follow IS: 1206 (Part III) methods for testing tar and bituminous materials: Determination of kinematic viscosity, for selecting the appropriate viscometer tube given there. Used oil bath for full viscosity can be used, just the viscometer tube will be different (pic-7) As an alternative, one can also use a rotational viscometer which will give similar results as bitumen is Newtonian in nature at 135 C. Purchase and use of rotational viscometer is encouraged as it can be used for modified binders and also for Superpave Performance Graded (PG) binders, which are expected to be adopted in the near future. Again, the rotational viscometer cannot be used to measure absolute viscosity at 60C.

article written by

Pro. Prithvi Singh Kandhali

Jaipur, India

Er. Mukesh Kumar

Photo of author
Er. Mukesh Kumar is Editor in Chief and Co-Funder at Civil Engineering Website. Mukesh Kumar is a Bachelor in Civil Engineering From MIT. He has work experience in Highway Construction, Bridge Construction, Railway Steel Girder work, Under box culvert construction, Retaining wall construction. He was a lecturer in a Engineering college for more than 6 years.