$\rightarrow$ Theory

1. In order to known the hardness or softness of bitumen which is used for road construction, this test is carried out.

2. In this test, the sample is prepared by softening the material to a pouring consistency between 75° C to 100° C above the approximate softening point determined by ring and ball apparatus.

3. The test is carried out with a standard penetrometer as shown in Fig. 4.10.1. Weight with a needle loaded with 100 gm.

$\rightarrow$ Procedure.

1. The sample to be tested is maintained at a constant temperature of 25°C.

2. At the start of the test, the needle is kept in such a way that its point just touches the surface of sample.

3. The needle is then released and is allowed to penetrate into the sample under the full action of the load.

1. The penetration at the end of 5 seconds is measured.

2. Similarly, minimum three readings are taken at different point not within 10 mm from the edge of the container or from the point where it was previously tested.

3. The mean of three penetrations is always taken as the penetration value.

4. The results of three independent observations should not differ more than the following limits; otherwise the test should be repeated.

1. The bitumen grade is specified in terms of penetration value. For example 80/100 grade bitumen means the range of penetration is in between 80 to 100.

2. The IRC has recommended bitumen grade.

1] 30/40 grade bitumen

2] 60/ 70 grade bitumen

3] 80 / 100 grade bitumen

$\rightarrow$ Ductility test on Bitumen.

Q. State the values for minimum ductility of bitumen as per IRC.

$\rightarrow$ Minimum ductility of bitumen.

Minimum ductility of bitumen is 7 cm for bitumen grade of 45 and above 50 cm for bitumen grade of 535.

• To determine the ductility of bitumen, the sample is cast in standard briquette mould whose cross section at the minimum width is 100 x 10 mm.

• The ductility value is expressed as the distance in centimeter’s to which a standard briquette of bitumen can be stretched before the thread breaks as shown in Fig. 4.10.3.

• The test is conducted at a temperature of 27°C $\pm$ 0.5°C at the rate of pull of 50 mm $\pm$ 2.5 mm per minute.

• The ductility values of bitumen may vary from 5 to over 100 different grade of bitumen.

• Usually ductility value of bitumen should not be less than 50 for satisfactory performance