Bitumen – The Key Material in Road Construction

Bitumen is black and sticky material. It is the same as the glue that can bond aggregates in road construction well to each other.

This material can be obtained in the oil refinery. But there exists another type of this material which is natural bitumen or Gilsonite that can be extracted from mines. To know more about types of bitumen, read the article below.

Bitumen types

Generally, bitumen has different types including:

• Penetration Grade
• Viscosity Grade
• AH Grade
• Performance Grade
• Oxidized or Blown Grade 

The above types of bitumen are produced in the crude oil refinery. Each of them has its own grades that have been classified based on different factors. Using AH grades is not very common but the other 4 types are highly demanded in the civil engineering operational sites.

Penetration Grades Bitumen

Penetration grades are classified based on their penetration degree that can be obtained by a bitumen penetration test. This type of bitumen is widely used in the world. It has different grades including:

• 30/40
• 40/50
• 60/70
• 80/100

Bitumen Penetration 60/70 is the most popular bitumen in different industries.

Viscosity Grades Bitumen 

Viscosity grade bitumen is another type of bitumen that is replaced by penetration grades according to Indian Standard. This type of bitumen is classified based on its viscosity. Different grades of this bitumen are as below:

• VG10
• VG20
• VG30
• VG40

Among the above grades of viscosity bitumen, VG30 and VG40 are very popular in the market. Based on the regulation of the MINISTRY OF ROAD TRANSPORT & HIGHWAYS, Government of India, VG40 should be used in bituminous concrete.

Performance Grades Bitumen

Performance grade bitumen is a type of bitumen that is graded based on performance at different temperatures. 

In the classification of this type of bitumen, each type is defined by positive and negative numbers, where the positive number corresponds to the average temperature of seven consecutive days of the highest pavement temperature in the summer season and the negative number corresponds to the minimum pavement temperature in seven consecutive days of the winter season.

Oxidized or Blown Bitumen

It is a type of bitumen that is oxidized by blowing air into the pure bitumen. This type of bitumen has a lower penetration grade and more softening point in comparison to penetration and viscosity grade bitumen. These types of bitumen have different grades but the most used grades in industries are as below:

• 85/25
• 95/25
• 115/15

The above bitumen types can be used in road construction on hot asphalt. Besides the hot asphalt, there exists cold asphalt. In cold asphalt, two other types of liquid bitumen can be used which are cut back and emulsion bitumen.

Cut Back Bitumen 

Cut-back bitumen is a type of bitumen that is diluted by a petroleum-based solvent. Due to the petroleum-based solvent, it is more expensive than other types of bitumen. Altogether it is recommended not to use this bitumen very much.

Emulsion Bitumen 

This type of bitumen is a combination of bitumen, cationic or anionic emulsifier, and water. The viscosity of this type of bitumen is too low. It is not necessary to heat this bitumen before using it.

 It is better to use bitumen emulsion instead of cut back bitumen regarding the environmental side effects of petroleum solvents in cut back bitumen. 

Bitumen Application in Road Construction 

All of the above bitumen grades can be used in road construction. Some of them, the same as penetration and viscosity grades, can be used as the main bitumen in the road but bitumen like oxidized bitumen should be used as an additive in road construction to improve the performance of the asphalt. Cut back and emulsion bitumen are used in protective asphalt to maintain the roads and fill the cracks.

In the Infographic below which is prepared by Infinity Galaxy team, the application of different grades of bitumen in road construction is clarified well: