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Transportation Engineering Lab Experiments

Penetration Test of Bitumen Experiment


To determine the penetration value of the given bitumen sample

IS Standards used: IS 1203 - 1978

Need and scope:Various types and grades of bituminous materials are available for use in road making. One of the ways of grading bitumen is in terms of its penetration value. Penetration grading system of bitumen has been replaced in India by viscosity grading. However, penetration test remains to be an important test which is retained in many binder specifications. The penetration test determines the consistency of bituminous binders for the purpose of grading them and for the purpose of giving an indication of the expected performance. Penetration is determined by measuring the depth (in units of one tenth of a millimetre) to which a standard needle with the needle assembly weighing 100 gm will penetrate vertically at 25°C standard temperature in 5 seconds of standard duration. The softer the bitumen, the larger will be the penetration. The penetration grades of bitumen are generally designated as 80/100, 60/70, or 30/40 grade bitumen. 80/100 bitumen indicates that the penetration value of binder ranges from 8 mm to 10 mm.

Apparatus Required:

  1. Penetrometer
  2. Sample cup
  3. Water bath for maintaining a temperature of 25°C.
  4. Thermometer
  5. Specified needle
  6. Stop watch

Experimental procedure:

  1. Pour the bitumen sample into the container of 35 mm depth.
  2. Cool in atmosphere at a temperature between 15-30°C for 60 to 90 minutes.
  3. Place the container in the water bath maintained at a temperature of 25°C for 60 to 90 minutes.
  4. Place the sample under the penetrometer and adjust the screw so that the tip of needle just touches the surface of the bitumen sample.
  5. Take the initial reading and press the knob for 5 seconds. Take the final reading.
  6. Make at least three such measurements.

Observations and Calculation:


The average penetration value of Sample A =

The average penetration value of Sample B =

General remarks:

Viva Questions:

  1. Which property of bitumen is related to penetration value?
  2. The penetration value of binder is 65; what is the distance in mm which the needle has penetrated through?
  3. What does an 80/100 grade bitumen indicate?
  4. Which bitumen grades are commonly used in warmer regions and why?