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Bitumen tests

Bitumen tests

:Some tests are carried out on the bitumen samples among which the following tests could be mentioned

1. Penetration grade test


Bitumen stiffness is generally determined using the penetration test. The test is carried out on a sample which is placed under a needle. The needle is loaded with a 100 g weight. The penetration of the needle into the bitumen sample after 5 seconds is measured in units of 0.1 mm which is called the penetration grade. The bitumen temperature in this test should be 25 ºC. The low penetration value means that the bitumen is stiffer.

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2. Viscosity test

The bitumen viscosity value has an important effect on the determination of bitumen properties so that the higher viscosity value shows the higher solidity of the bitumen. It is obvious that the rise in temperature leads to the reduction of viscosity. This test is done using the Saybolt Furol apparatus or according to the kinematic method.

3. Flash point test

According to the definition, the flash point is the temperature at which the gases resulted from bitumen heating ignite when a flame is brought into contact with them. Knowing this temperature is important to determine the maximum temperature that bitumen could be heated which should be less than the flash point.

4. The Thin Film Oven Test:

Oils and other compositions existing in the bitumen are separated from it at high temperatures and this leads to the reduction of bitumen weight which is called weight loss. Weight loss is one of the important properties of bitumen. According to the test method, the temperature and time of the experiment should be 163 ºC and 5 hours respectively which approximate the construction conditions of hot mix bitumen.   

5. Ductility test

If a bitumen sample with a 1 cm2 area is stretched at the rate of 5 cm/minute, the length of the sample before breaking is named the ductility of the bitumen.

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6. Solubility test

If a bitumen sample is dissolved in trichloroethylene or carbon disulfide, an amount of impurity remains in the solution which could be measured to determine the purity of bitumen. In fact, if the impurity weight is subtracted from the whole weight of the bitumen and is divided into it, the result indicates the purity of bitumen.

7. Softening point

The softening point is the temperature at which the bitumen transforms from solid to liquid or starts flowing. In fact, the higher softening point shows the less sensitivity of the bitumen against the temperature change. The softening point of bitumen is generally 60 to 70. 

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