Bitumen Types and Grades

October 2, 2019
8 minutes

Different Types of Bitumen and Their Grades

Bitumen is an organic substance with a complex composition. 

It does not have a specific chemical formula. Therefore, to classify it several methods have been introduced to the industry based on the bitumen origin and its physical properties. 

There are two types of bitumen based on their origin:

  • Natural Bitumen (Gilsonite)

Its composition is similar to refinery bitumen. It is extracted as lumps. But it is mostly used as micronized powder. It contains impurities, including ash. For this reason, it is classified based on the percentage of ash as well as the particle size.

Read more about Gilsonite here.


Gilsonite Lump
Gilsonite Lump
Micronized Powder of Gilsonite
Gilsonite powder
  • Refinery Bitumen

Refinery bitumen, known as bitumen for short, is extracted from crude oil. In the past, there was no exact method for classifying bitumen. Engineers used a chewing test to measure the hardness and softness of bitumen. If the stiffness was sufficient, the sample is approved and otherwise rejected.

infinity galaxy bitumen in new steel drum

By adding different compounds to pure bitumen derived from the refinery, it can be modified for the purposes of use. These modified bitumens are obtained by adding solvents, polymers, emulsifiers, or other compounds. 

The properties of these products are different according to the amount of added matter. Then each type of modified bitumen is classified by bitumen tests. 

Modified bitumens are:

  • Cutback bitumen
  • Emulsion bitumen
  • Polymer modified bitumen

Different tests can be done on different grades of bitumen to ensure the bitumen quality.

If you are interested in reading about them, visit the Bitumen Tests page. 

In addition to the grading and classification mentioned above, there are other types of bitumen that do not belong to any of them, including

  • Oxidized bitumen
  • Crystal bitumen

In the following, we will introduce these bitumen and their classifications.

A) Bitumen Grading Systems:

1-Penetration Grading Method

In the early 20th-century penetration grading system was developed based on penetration test based on penetration test.

Penetration bitumen is produced by performing a series of processes on the vacuum bottom. 

To classify and name this bitumen, a needle with 100 grams load is applied to its surface for five seconds. The amount of needle movement is reported in deci-millimeters. This test performs at 25 ° C.

Penetration grade bitumen is widely used in road construction especially 60/70 and 80/100 grades.

To choose the proper one, the average temperature of the region must be considered. 

Bitumen with a higher degree of penetration is appropriate for cold regions, while bitumen with a lower degree of penetration is ideal for tropical areas.

In the following, the different bitumen penetration grades are:

20/30     30/40    40/50    50/60    60/70    80/100    85/100

See these grades specification in our article about penetration grade of bitumen.

Sometimes the same grade of bitumen penetration has different behavior in high temperatures. 

It is the main weakness of this grading method. As a result, the viscosity grading system is introduced.

Penetrometer
Penetrometer

2-Viscosity Grading Method

Viscosity grading bitumen is the method to classify produced bitumen in a refinery, based on its viscosity at 60 ° C by bitumen viscosity test.

This method was introduced by the United States in the late 20th century. 

The viscosity grading system in India measures the viscosity of bitumen at two temperatures of 60 ° C  and 135 ° C. 

Viscosity at 60 ° C  shows the resistance of bitumen to melting in hot climatic conditions. Viscosity at 135 ° C determines the behavior of bitumen while its temperature is very high for preparing hot mix asphalt.

Viscosity bitumen must be selected according to the average temperature of the region.

Based on Indian Standard, viscosity bitumen is classified into 4 grades:

VG10, VG20, VG30, and VG40

Check their characteristics on bitumen viscosity grade page.


capillary viscometer
Capillary viscometer apparatus
reometer
Reometer apparatus


3-Performance Grade Bitumen

Performance grade is the newest classification method. It is introduced to the industry about 20 years after viscosity grading.

Despite all grading systems, there was a lack of accurate methods that could be able to choose the best bitumen for an area.

The suitable road bitumen should be able to tolerate very low and high temperatures to prevent cracking and rutting respectively.

To evaluate bitumen performance, it is exposed to the average maximum and minimum temperatures for a week.

High temperatures range from 46 to 82 ° C and low temperatures range from -46 to -10 ° C.

Each bitumen grade is given a positive and negative number, which indicates the maximum and minimum temperatures.

For example, PG 64-10 bitumen reaches the yield coefficient at a maximum seven-day pavement temperature of 64 ° C and also at a minimum pavement temperature of -10 ° C.

Note: Due to the black color of asphalt and more heat absorption, the temperature of asphalt can be 20 degrees Celsius higher than ambient temperature.

For more information, see our article about performance grade bitumen


B) Modified Bitumen

1-Cutback Bitumen

Cutback bitumen is used in industries that require low viscosity bitumen.

It is also used in cases where bitumen can not be preheated to make asphalt. 

To prepare this product, viscosity bitumen is mixed with organic solvents in a certain amount. These organic solvents include diesel, naphtha, diesel oil, and fuel oil. They have a low boiling point and evaporate easily. When bitumen is used on the surface, the solvent evaporates and bitumen remains. The speed of evaporation and remaining bitumen is considered curing time. Cutback bitumen has different curing, which include:

  • Slow Curing(SC)
  • Medium Curing(MC)
  • Rapid Curing(RC)

Know more about cutback bitumen here.


Infinity-Galaxy-Cutback-and-Emulsion-bitumen
Infinity Galaxy Cutback & Emulsion bitumen samples



2-Emulsion Bitumen

Emulsion bitumen is produced by combining a certain volume of water in the bitumen. In order to dissolve bitumen in water, a suitable emulsifier is used.

Emulsion bitumen is classified based on two main factors: 

  • Particles’ electrostatic charge of the emulsifier:
  1. Cationic
  2. Anionic
  • Breaking or setting time, the time that takes to evaporate the water:
  1. Slow setting (SS)
  2. Medium setting (MS)
  3. Rapid setting (RS)

Are you interested to know more details? Check out emulsion bitumen page.

Bitumen Emulsion Types & Grades
 Cationic Emulsion Anionic Emulsion
Rapid setting type (RS)·CRS-1
·CRS-2
·CRS-1h
·K1-60
·K1-40
·K1-70
·RS-1
·RS-2
Medium setting type (MS)·CMS-1
·CMS-2
·CMS-2h
·K2
·K3
·MS-1
·MS-2
·MS-2h
·HFMS-1
·HFMS-2
·HFMS-2h
·HFMS-2S   
Slow setting type (SS)·CSS-1
·CSS-1h
·Modified CSS-1h
·SS-1
·SS-1h
·Modified SS-1h



3-Polymer Modified Bitumen (PMB)

To improve the performance of bitumen in asphalt paving, using the various types of polymers in bitumen became common in the mid-twentieth century.

These materials are added to bitumen with a weight ratio of 1-5 %.

The most commonly used amount is 3% by weight. The amount of additive polymers in some cases can reach 7% by weight.

Types of polymers used in bitumen include the following list:

  1. Natural Polymers
    1. Lignin
  2. Thermoplastics/ plastomers
    1. Polypropylene
    2. Polyethylene
    3. Ethylene-vinyl acetate 
  3. Elastomers
    1. Natural rubber
    2. Synthetic rubber
    3. Polybutadiene
    4. Butyl rubber
  4. Thermoplastic Elastomers
    1. Styrenic block copolymers
    2. Polyolefin blends
    3. Thermoplastic polyurethane
  5. Ground Tyre Rubber
    1. Reclaimed scrap tyres

Among the above cases, thermoplastic elastomers are the most widely used. The reason for the popularity of this polymer is that:

  • Adding it to the bitumen leads to an increase in the elasticity of the bitumen, which makes it possible to use a smaller amount of polymer bitumen than ordinary bitumen to bond the aggregates.
  • Increased ductility resistance to fatigue, stripping, and deformation
  • Increases bitumen resistance to softening at high temperatures and reduces bitumen cracking at low temperatures. 
  • In fact, the addition of polymer reduces the temperature sensitivity of bitumen and instead increases its ductility and adhesion.

Polymer bitumen using ground tyre rubber is more common in the United States. This type of polymer generally makes up between 5% to 20% of the weight of the binder.

This modified bitumen helps protect the environment because it reuses unusable tyres.

On the other hand, it has advantages such as increased skid resistance, improved flexibility and crack resistance, and reduced traffic noise.

4-Oxidized Bitumen

Oxidized bitumen is produced by blowing hot air in a vacuum bottom. This method generates hard and brittle bitumen. 

Sometimes pure bitumen is transferred to another oxidation tower for applying the processes. 

Oxidized bitumen has a lower degree of penetration and higher softening point compared to pure bitumen. It is classified based on these two properties and the degree of oxidation.

Different types and grades of oxidized bitumen are listed below.

See our article about Oxidized Bitumen for more information.


Low oxidized Bitumen
  • R75/30 
  • R85/25 
  • R85/40 
  • R90/40 
  • R95/25
Medium oxidized bitumen
  • R90/10
  • R90/15
Hard oxidized bitumen
  • R105/35
  • R115/15

C) Other Types of Bitumen

1-Crystal Bitumen

After applying processes to make different products from crude oil, a hard and brittle organic material remains in the distillation tower. This residue is named crystal bitumen.

Its penetration and ductility are below 30 and 10 cm, respectively.

See the crystal bitumen page for more information.


crystal bitumen
Crystal bitumen

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2 comments

ikram

April 1, 2023

Very useful article and information.

Mozhdeh Darbandizadeh

April 6, 2023

How nice of you dear friend, Thanks😊

Mona Zahedi

October 2, 2019
8 minutes
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