What is Bitumen?

Bitumen is found in nature and also can be extracted from crude oil.

Crude oil is a mixture of different compounds that is separated by a distillation tower. The remnants of the distillation tower, called vacuum bottom, are transferred to be processed and turned into bitumen. It is composed of complex, heavy hydrocarbons and used in various industries. It is generally composed of asphaltene resin and other petroleum compounds.

As a viscous substance, bitumen exists in a liquid to a semi-solid phase. It appears mostly in a blackish-brown color.

Different compositions of bitumen result in different properties.

The main application of bitumen is in road construction. More than 85% of the world’s bitumen production is used for road construction, 10% is used in other constructions and 5% is used in a variety of other industries, including insulation.

Types of Bitumen

Since different kinds of crude oils results in various types of bitumen with completely different properties, grading bitumen is essential.

For grading bitumen based on its properties, refineries use a number of standard tests to measure the viscosity level, penetration value, performance, and consistency of bitumen.

The result of these tests is bitumen penetration grades and viscosity grades.

Other grades of bitumen, including cutback bitumen, oxidized bitumen, and bitumen emulsions are classified based on their production process.

1- Gilsonite (Natural bitumen):

Gilsonite is natural bitumen with a shiny, smooth and solid appearance. Types of Gilsonite are classified based on their ash contents and the solubility in organic solvents.

Since it is a hard and brittle material, it is mostly used in powder form. Gilsonite composition is close to refinery bitumen.

Sometimes in the road construction industry, the combination of gilsonite with refined bitumen is used. Although it has a higher resistance to water penetration, its degree of penetration and deformation is low.

Applications of gilsonite:

Printing industries
Painting industry
Drilling mud and cement
Asphalt and road construction
Casting sand additive
Chemical products
Improving the quality of bitumen

2- Penetration grade bitumen

Penetration bitumen is the most commonly used bitumen for road construction.

After production in the refinery, it is classified by penetration test using a penetrometer apparatus. The deeper the needle penetrates into the bitumen surface, the softer it will be and suitable for colder weather. The most widely used bitumen for road construction is penetration bitumen of 60/70 grade and then grade of 80/100. Furthermore, 60/70 grade is widely used as a insulation material in buildings.

3- Viscosity grade bitumen

Viscosity grade bitumen is classified based on its viscosity after production in refineries. This classification is more recent than the penetration classification.

Viscosity bitumen has four different grades that are VG10, VG20, VG30, and VG40. They have different applications.

The reason for using viscosity grading instead of penetration is the change in viscosity of bitumen at high temperatures.

Here are some advantages of VG bitumen to Pen grades:

This grading system is designed to increase the accuracy of bitumen in hot temperatures. A specific grade of pen bitumen may show various results at a specific temperature, but VG bitumen behaves always the same.
When there is a need to predict bitumen behavior in the hottest time of the year as well as its properties in normal weather conditions, VG bitumen is a better choice. Since viscosity testing is based on experimenting with bitumen’s properties at three different temperatures (25° C, 60° C, and 135° C), all grades of VG bitumen come with an easier application.

4- Cutback bitumen

This bitumen is used in industries that require low viscosity product. Cutbacks are also used in cases where bitumen cannot be preheated to make asphalt.

To prepare cutback bitumen, penetration bitumen is mixed with organic solvents in a certain amount. These organic solvents include gasoline, naphtha, diesel oil, and furnace oil.

This type of bitumen is suitable for cold climates. The solvents evaporate when bitumen is used.

The cutback is suitable for primer sealing and sprayed sealing.

The only concern is the effect cutback bitumen has on the environment. The volatile solvents were hazardous to nature, humans, and the environment.

5- Emulsion bitumen

Bitumen emulsion is named based on its production process. This type of bitumen is a chemical combination of bitumen and water.

Since water is a reliable alternative to organic solvents to dilute bitumen sufficiently for special applications, this product came to the industry to avoid the environmental damages of cutback bitumen.

Emulsion bitumen is beneficial to waterproofing, spraying, and tack coats between layers of asphalt pavement.

Transporting, handling, and storing bitumen emulsion are very easy, economical, and safe.

Bitumen emulsions are classified based on two main factors:

- Particles’ electrostatic charge

- Breaking or setting time

According to their electronic charge, bitumen emulsions can be anionic (with a negative charge) and cationic (with a positive charge).

The second grading system is based on the time that is needed for a bitumen emulsion to lose water and become sticky enough to bind aggregates.

Considering that different grades of bitumen emulsions have different properties, each type is suitable for a particular type of application.

Three factors of “viscosity level”, “setting time”, and “electronic charge of bitumen particles”, affect the application of each type of bitumen emulsions.

Bitumen emulsions are less viscous than other grades of bitumen because they are mixed with water and emulsifiers. As a result, we use this type of bitumen for spraying applications.

Bitumen emulsions are also ideal for pavement maintenance and renovating old roads.

Major applications of bitumen emulsions in today’s bitumen industry are tack coats, chip seals, slurry seals, and micro surfacing.

6- Oxidized bitumen

Oxidized bitumen is acquired in the refinery by blowing hot air into the penetration bitumen. The bitumen obtained from this process is chemically stable and has high durability. It is also impermeable to water and is suitable for insulation.

Oxidized bitumen has a lower degree of penetration and higher softening point compared to pure bitumen. Also, it is classified based on these two properties.

Applications of oxidized bitumen include waterproofing in dam construction projects, buildings etc. Also, it is applicable in road construction in combination with other types of bitumen. In other industries, especially oil and gas, it is used to cover pipelines to prevent corrosion.

7- Performance Grade bitumen (PG bitumen)

Bitumen Performance Grade is a type of bitumen grading system according to its performance at different temperatures.

Bitumen is more suitable if it can endure at a wide range of temperatures.

Classification of PG bitumen is handled at high and low temperatures.

The major issue for high-temperature performance is rutting, which normally takes a while to amass. It takes some time for rutting to disappear.

At low temperatures the probability of cracking increases.

To evaluate bitumen’s performance, the average maximum and minimum environment temperatures of asphalt production are chosen.

The bitumen is then exposed to these two temperatures for a week.

The average high and low temperature is increased by 6 °C.

The high temperature in these grades is in the range of 46 to 82 °C and the low temperature in the range is -46 to -10 °C.

Grading bitumen is based on a positive number and a negative number, which indicates the maximum and minimum temperature.

For instance, bitumen PG 64-10 meets the performance factor at an average seven-day maximum pavement temperature of 64 °C and also at a minimum pavement temperature of -10 °C.

If the sum of high and low temperature numbers is more than 90, it will be polymer modified bitumen, and if it is less than 90, it will be unmodified polymer bitumen.

As an example, a PG 76-22 is considered as a polymer-modified binder since the sum is 98. Another example, a PG 64-10 is an unmodified binder.

Thermal cracking is less likely to occur in PG grades 58-34, 64-22, 64-28, and 76-22. In addition, the PG 70-22, 70-28, 76-28, and 82-22 grades are more resistant to rutting.

Performance grade bitumen is commonly used in construction and reconstruction pavement, sealing edges, sealing cracks in both dense and open grade Hot Mix Asphalt (HMA).

Bitumen tests

Bitumen quality tests are a criterion for diagnosing the quality and classification of bitumen in the industry. These tests are also taken to control the quality and guarantee of the bitumen load issued and imported in the ports of origin and destination.

According to SGS standard, bitumen quality control tests or “bitumen tests”, are as follows:

1- Penetration test:

The penetration test is used to measure the hardness and softness of bitumen. Penetration bitumen obtained from the refinery is classified based on this test. The degree of penetration of bitumen has a direct relation to its ductility and shows that asphalt has a higher loading capacity.

High penetration bitumen is suitable for cold climates and low penetration bitumen is suitable for hot climates.

To perform this test, a needle is penetrated into the bitumen surface with a load of 100 grams for 5 seconds. The degree of penetration is equal to the amount of needle penetrating. Its unit of measurement is 0.1mm.

2- Viscosity test:

Viscosity test is used to determine the adhesion of bitumen to asphalt aggregates. Bitumen must have an optimal viscosity value. This means that very viscous or very low viscosity bitumen would not be suitable for road construction. In addition, viscosity is highly sensitive to temperature changes. Increasing the temperature would lead to decrease in viscosity and so, its cohesion would be lost. Conclusively, the viscosity is measured at temperatures of 60 °C and 135 °C. By measuring these two viscosity levels, we can have enough information on the best temperature to mix and compact bitumen with aggregates.

To measure the viscosity using the viscometer apparatus, the time required to remove a certain amount of bitumen from the viscometer is measured and multiplied by the correction factor of the device. The number obtained shows the viscosity of the bitumen.

3- Softening point test:

As a combination of different hydrocarbon materials such as asphaltene and resin, bitumen does not have a specific melting point. By applying the heat, it becomes soft and melts slowly.

The temperature at bitumen starts to melt is called the softening point. This point is vital for engineers as it indicates the temperature that bitumen loosens and its adhesive drops.

The laboratory method of measuring the softening point is the ring and ball method.

To perform the test, the bitumen sample is taken in two brass rings. Two steel balls are placed on the bitumen samples. Then, the assembly is placed in a water bath and heated.

The softening point is the temperature at which the steel ball coated with bitumen hits the bottom of the glass beaker.

4- Ductility test:

As long as the bitumen has good ductility, it will be resistant to road traffic as well as expansion and contraction of bitumen due to temperature changes; the possibility of asphalt cracking will decrease and asphalt life will increase.

To measure this property, bitumen is poured into a special mold and the mold is pulled from both sides at a constant speed of 5 cm per minute. The amount of bitumen stretched to the moment of rupture is reported as ductility. The longer the length, the greater the ductility.

5- Specific gravity test

Specific gravity is the ratio of the mass of bitumen to the mass of water, while both have the same volume.

Each bitumen has a certain amount of specific gravity. As a result, this property is used to measure the degree of impurities in the bitumen. It is also used for calculations.

A pycnometer is used to measure this property. The ratio of bitumen weight to water weight is equal to the specific gravity of bitumen (subtracting the weight of the device).

6- Solubility in TCE

This test is performed to measure the purity of bitumen by detecting the non-oil impurities. For this purpose, 2 grams of bitumen is dissolved in 125 ml of trichloroethylene. The solution is weighed and then filtered through Whatman paper. Impurities are washed and dried and finally weighed. The percentage of impurities should not be more than 1% because it indicates the low quality of bitumen. High impurity in bitumen will have low adhesion strength.

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

7- Flash and Fire point test

There are also risks in transporting and storing flammable materials. As a result, it is more important to notice the flash and fire point of bitumen.

Heat causes liquid materials to evaporate. With flammable liquids, it will catch fire if there is an ignition source like a spark.

Two devices are used to obtain the flash point and fire point:

- Pensky-martens

- Cleveland open cup tester

The procedure of the test is that bitumen is poured into the cup of the apparatus and then it is heated.

During heating, the flame passes over the liquid surface and through the vapors once every 2 seconds.

The temperature at which an instant flame appears on the surface of bitumen is called a flash point.

To obtain the flash point, heat is continued and the flame continues to pass over the surface of the liquid until an instant flame reappears on the liquid surface for a moment.

Compared to the previous flame, this one lasts longer. Its temperature is reported as the fire point.

8- Loss on heating test

The amount of volatiles in the bitumen is measured by the loss on heating test. Volatiles are compounds that have a lower boiling point than water and evaporate at a lower temperature.

The higher the percentage of volatile materials in the bitumen, the harder it becomes for the asphalt during the heating process and it loses its elasticity. A suitable bitumen binder should contain less than 1% volatiles.

To perform this test, 50 g of bitumen sample is heated in the oven at 163 °C for 5 hours. After that, the bitumen sample is weighed.

The percentage of loss on heating is calculated as follows:

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

9- Spot test of bitumen

The spot test of bitumen is used to indicate that the bitumen is not damaged during the refinery’s overheating.

Applying high temperature in a refinery causes cracking in bitumen. Cracked bitumen is not sticky enough to hold aggregates together. Furthermore, it cannot tolerate the preheated process in road constructions.

To perform the test, 10 ml of a solvent is put in a flask containing 2 grams of bitumen sample. The solution is rotated and placed in boiling water until it is dissolved completely.

After it cools at room temperature, drop is put on a filter paper.

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.

10- Drop in penetration after heating test

Drop in penetration tests measure the hardness and volatile content of bitumen.

When bitumen is heated for construction purposes, the volatile component evaporates and causes the material to harden. The more the volatile content, the harder the bitumen.

To perform the drop in penetration after the heating test, the needle with a load of 100 grams is applied on the bitumen surface for 5 seconds and the amount of penetration in 0.1 mm is measured.

Then the bitumen sample is placed in the oven at 163 degrees Celsius for 5 hours.

After removing the sample, it is allowed to cool. In the next step, the penetration test is repeated.

Drop in penetration value (%) =

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

Bitumen manufacturers in Iran

1	Azar Pasargad Co.
2	Negin Gam Pars Co.
3	Azarbam Ayegh Kar Co.
4	Azar Davam Youl Co. (ADYCO)
5	Negin Siyah Azerbaijan Co.
6	RK Northwest Refining and Energy Company
7	Negin Fakhr Azerbaijan Co.
8	Azerbaijan Tekin Petroleum Refining Industries
9	Bam Gostaran Co.
10	Petro Sanat Zomorod Co.
11	Jey Oil Refining Company
12	Miladco Industrial Company
13	Ayegh Isfahan Manufacturing Company
14	Tavan Gostaran Ayegh Co.
15	Pasargad Oil Company
16	Ghiran Pakhsh Setareh Iranian Co.
17	Palayesh-e Hesar Mehran Co.
18	Dejpa Bitumen Company
19	Siahfam Company
20	Behboud Sanat Group
21	Zarrin Bitumen Refinery Technology Co.
22	Gohar Ghir Shargh Co.
23	Negin Asphalt Mahneshan Co.
24	Sang va Kooh Company
25	Shiraz Oil Refinery Company
26	Dena Bam Golestan Co.
27	Green Star Company
28	Bitumen Hormoz Pars Co.
29	Jey Sepahan Bitumen Co.
30	Matin Saz Company
31	Asphalt & Bitumen West Co.
32	Alvan Ghir Delijan Co.
33	Janat Oil Refining Co.
34	Dorsa Group Co.
35	Sinarad Bitumen Company
36	Hormozan Oil Company
37	Akam Bitumen Company
38	Kimia Jey Bitumen Company
39	Spadana Bitumen Pasargad Co.
40	Binas Energy Company
41	Satrap Jam Bitumen Refinery Co.
42	Petropad Hafez Co.
43	Petrotar Farasahel Oil Co.
44	Kasra Bitumen Refining Co.
45	Roham Sperlus Co.
46	Fouman Chemie Gostar Co.
47	Petroakam Pasargad Co.
48	Mehr Parsian Bitumen Company
49	Almas Bitumen Nanotech Co.
50	Ace Oil Co.
51	Black Gold Co.
52	Parsian Energy Co.
53	Aftab Oil Refining Co.
54	Phoenix Bitumen Co.
55	Energy Tejarat Sam Co.
56	Petro Pasargad Group
57	Shimi Tejarat Naghsh Jahan Co.
58	Environment Structure Development Co.
59	Corus Energy Development Co.
60	Hormozgan Tar Industrial Producing Co.
61	Shimi Palayesh Sadaf Co.
62	Pars Kinetic Multiplier Co.
63	Naft Gostar Anahita Co.
64	Varziran Company
65	Ghire Shargh Co.
66	Jahan Ara Bitumen Co.
67	Petro Ghir Azhand Co.

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