Intensive Review of Major 10 Bitumen Tests 

Bitumen Tests

Since Bitumen is one of the main materials in road construction, its properties have to be tested by different bitumen tests before application.

These tests help us to examine bitumen quality before using it and know the behavior of bitumen during its lifetime. Some bitumen tests can also be used to classify bitumen by its physical properties.

If you are interested to know more details about these bitumen tests, follow the Infinity Galaxy Bitumen Test article. Also, we have a brief explanation of the 10 bitumen tests here.

Bitumen Penetration Test

The penetration test of bitumen determines the bitumen consistency. This test is used for grading bitumen based on penetration value or in other words its hardness.

For very soft materials with low viscosity such as tars, penetration tests cannot be carried out.

The procedure of this test is as below:

In a bitumen penetration test, a needle with a loading of 100 grams penetrates the bitumen vertically for five seconds at a temperature of 25 degrees Celsius.

The higher the penetration of the needle in the bitumen, the higher the bitumen grade. Eventually, the softer bitumen.

Bitumen Softening Point Test

It is not very clear at what temperature bitumen becomes totally liquid. Since the bitumen is one of the most important components of asphalt, in hot regions, when the temperature rises, it becomes too soft.

In this condition, it loses its ability of adhering to the aggregates and the asphalt loses its uniformity.

So, by using bitumen softening point test, it is feasible to find out at which temperature the bitumen starts to melt gradually and become soft.

In general, the softening point of penetration grade bitumen and viscosity grade bitumen decreases as penetration increases. In fact, softer bitumen gradually melts at lower temperatures and its thermal resistance is lower.

For this test, the bitumen sample is placed in two brass rings and two steel balls are placed on it. The assembly is placed in a warm water bath. When the bitumen coated steel ball hits the bottom of the beaker, the temperature should be measured. This temperature is the softening point temperature.

Bitumen Ductility Test

If the bitumen binder is ductile enough, it is capable of tolerating deflections that occur on the road. Consequently, the probability of cracking becomes lower and the life span of asphalt is increased.

The tester is filled with bitumen and is placed in a water bath. Then it is pulled at a temperature below its softening point. Ductility is the length before tearing apart a stretched bitumen.

 Bitumen Viscosity Test

Viscosity tests measure the resistance of bitumen to flow. The higher the viscosity of the bitumen, the harder it is to flow. Consequently, it behaves more like a semi-solid matter.

The viscosity of a bitumen can also determine how well bitumen can compact aggregates together to form a uniform asphalt.

To perform this test, first the sample of bitumen should be placed in a viscometer. then  the flow out time should be measured. The viscosity is calculated by multiplying the calibration coefficient of the viscometer by the time in seconds.

• Bitumen in the Road Layers

Bitumen Specific Gravity Test

Bitumen specific gravity test determines the ratio of bitumen weight to the weight of the water with the same volume.

Specific gravity can help to recognize the impurity of bitumen because impure bitumen has a higher specific gravity. Asphalt mixes with high specific gravity bitumen are low quality.

To perform the test measure the following then use the equations:

A= mass of pycnometer

B= mass of the pycnometer that is filled with water

C= mass of pycnometer about half-filled with the bitumen

D = mass of the pycnometer about half-filled with the material and the rest with distilled water

E = mass of the pycnometer filled with the bitumen.

For solid and semi-solid bitumen:

Specific gravity= (C-A)/[(B-A)-(D-C)]

For liquid bitumen:

Specific gravity=(E-A)/(B-A)

Bitumen Solubility Test 

This test shows the impurity of the bitumen sample. The high quality bitumen binder should be 99% soluble in trichloroethylene.

To do the solubility test of bitumen, dissolve the 2 grams of bitumen sample in 125 ml of trichloroethylene. Then weigh the solution and filter it. In the last step wash the insoluble matter, dry it, and weigh it again.

Here is how to calculate the percentage of insoluble material:

Insoluble matter (%)= mass of insoluble materials/mass of bitumen sample

Bitumen Flash and Fire point Test

When flammable or combustible materials are heated, the vapor is generated near their surfaces. Flash point is the lowest temperature at which the vapor burns in the presence of an ignition source with an instant flame.

Fire point is the temperature higher than Flash point.

By Pensky-martens and Cleveland open cup tester these tests can be performed.

In Cleveland open cup testers, add bitumen to the test cup and then heat it. The flame moves over the surface of the cup. The sample vapor is sparking at the flash point, but the fire point is determined by continuing to heat the sample until a flame appears above it.

Bitumen Loss on Heating Test

Bitumen loss on heating tests measures the percentage of volatile components of bitumen. In construction, the bitumen binder loss on heating must be less than 1%.

A bitumen with a high amount of loss on heating will be hardened. As a result it becomes less flexible and brittle.

To calculate the loss in the bitumen heating test, 50 g of the sample is heated in the oven at 163 degrees celsius. A bitumen sample is then weighed.

Here is how you calculate the percentage of loss on heating:

Loss on heating (%) = [(Initial weight – Final weight)/Initial weight]*100

Bitumen Spot Test

During the refinery’s overheating, a spot test is performed on bitumen to ensure it has not been damaged.

To perform this test, add 10 ml of a solvent to a flask containing 2 grams of bitumen. Stir the solution for five seconds and place it in boiling water for 55 seconds. Do this repeatedly until all the bitumen is dissolved.

Place a drop on filter paper after it has cooled at room temperature.

If the trace of the drop is brown the test is negative. Inversely if the drop is brown with a black center the test is positive and the bitumen is damaged.

Bitumen Drop in Penetration Test

Drop in penetration after heating test measures the hardening of bitumen after heating. Also, it measures the percentage of volatile components (materials with low boiling temperature) in bitumen.

To perform this test, put the bitumen in the containers and apply the needle with a load of 100 grams for 5 seconds. Place the bitumen sample at 163 C for 5 hours in the oven.

Then remove the sample and let it cool. In the next step repeat the penetration test.

Drop in penetration value (%) =

[Difference between 2 amounts of penetration/initial amount] * 100

Float Test

Float test is used to determine the consistency of highly viscous bitumen samples.

To perform this test, heat the bitumen and pour into the collar and wait for it to cool.

After screwing the collar to the alumina float, put the assembly in a water bath with a temperature of 5 C. After the assembly reaches the temperature balance, transfer it to a water bath with a temperature of 50 C. Record the time as the water begins to flow through the material.

Infinity Galaxy has presented a complete report for each bitumen test that you can read on its website.

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