Tests on bitumen 

There is a variety of criteria for the assessment of the properties of bituminous materials. These are some of the tests that are conducted to evaluate the features of bituminous materials. 

1. Ductility test 

2. Penetration test 

3. Softening point test 

4. Specific gravity test 

5. Viscosity test 

6. Flash and Fire point test 

7. Float test 

8. Water content test 

9. Loss on heating test 

Penetration test 

This test is for measurement of the hardness or softness of bitumen calculating the depth in tenths of a millimeter to which a standard loaded needle will penetrate vertically in 5 seconds.

 BIS has a standardized test procedure and equipment. The penetrometer made of a needle assembly weighing 100g and a device for releasing and locking in any position.

 The bitumen is softened to a pouring consistency, stirred thoroughly and poured inside containers at a depth of at least 15 mm more than the expected penetration. The test must be done at a specific temperature ( 25 C ).

It is noteworthy that inaccuracies mainly influence the value of penetration regarding the warmth of the pouring, the size of the needle, the weight imposed on the needle, and the temperature of the test. 40/50 grade bitumen has the meaning that it penetrates in between the variance of 40 and 50 with usual conditions.

In hotter climates, it is usually preferable to go with a lower grade of penetration. Refer to the figures.    

Testing Ductility

The ductility within bitumen at varying amounts can cause different effects and will undergo large deformation, or it will become elongated depending on the case.

Ductility is the distance measured in centimeters that a standardized amount or a briquette of the sample can be elongated without breaking. The briquette is always measured as a perfect single centimeter cube. They start by heating the briquette of bitumen and then place in in a mould and set it on a plate.

Afterward, the temperature is dropped via air cooling and then again utilizing water cooling until it reaches 27º Celsius. Any excess bitumen will be removed.

 The surface will then be leveled with a hot knife, and then the mould, including the assembly with its sample will remain in a water bath inside the ductility machine for close to 90 minutes.

Finally, the sides of the moulds will be taken away, then the clips are hooked to the apparatus, and it is then operated. From here, the distance it will stretch before breaking will be what is considered its Ductility value, and this will be measured in centimeters.

Everything from pouring temperature to test temperature to the speed with which it is stretched will all affect the ductility value. BIS has given 75 centimeters as the minimum value for ductility.

See the Figure for ductility moulds which will house bitumen.

The Softening Point Test

The temperature in which bitumen reaches a certain degree of softening and the specified test is the Softening Point. This is usually done by using a ring and ball to test.

First, a ring made from brass which contains the sample of bitumen will be placed in a suspended manner into a liquid, usually water but sometimes glycerin, at a specific temperature.

 Then a steel ball is placed on top of the sample. Finally, the cash will be incrementally heated at a rate of 5ºC per minute. 

The temperature will be recorded at the time that the softened bitumen touch’s the place at a specified distance beneath it. Usually, when the softening point is higher, it indicates upon a lower susceptibility to temperature, and this would be preferred in hotter climates.

See the Figure for the setup of the Softening Point Test.

The Specific Gravity Test

For paving applications, classifying a binder, the density property is the most useful. For a majority of applications, bitumen will be weighed, but in the even, it is used with aggregates, then the bitumen will be converted to volume instead by using density values. Its chemical composition has a significant influence on the density of the bitumen