Blown Bitumen (Oxidized Bitumen): Grades, Properties, and Applications

Bitumen stands as one of the most widely used and critical derivatives, playing a vital role across various industries like road construction, waterproofing, and building. Alongside natural bitumen, cutback bitumen, and emulsion bitumen, blown bitumen (also known as oxidized bitumen) is considered among the best types of modified bitumen. These bitumens are produced through the air blowing process (oxidation) of pure bitumen or vacuum bottom (V.B.) at high temperatures. This chemical process leads to the polymerization of bitumen and the removal of its volatile compounds, significantly altering its physical properties. As a result, the resulting bitumen gains higher heat resistance, a higher softening point, and lower penetration compared to the initial pure bitumen. These enhanced characteristics make blown bitumen an ideal material for diverse applications in road construction, waterproofing, and civil engineering.

 

Production Process and Advantages of Blown Bitumen

The production of blown bitumen involves passing hot air through bitumen in specialized reactors at high temperatures (typically between 200°C and 280°C). This oxidation process increases the molecular weight and promotes the formation of more asphaltenes in the bitumen, leading to improved properties.

Key advantages of blown bitumen include:

• High Softening Point: Blown bitumen softens at higher temperatures, increasing its resistance to deformation during hot weather.
• Low Penetration: This characteristic enhances the bitumen’s resistance to water and moisture penetration, making it suitable for waterproofing applications.
• Improved Elasticity: Blown bitumen offers greater flexibility than straight-run bitumen, providing higher resistance to cracking caused by temperature fluctuations.
• Aging Resistance: Its enhanced chemical stability reduces the rate of degradation and extends its useful life.

Due to these unique properties, blown bitumen is an ideal choice for applications requiring high thermal stability, flexibility, and resistance to environmental factors.

 

Blown Bitumen Grades Based on ASTM/AASHTO Standard (Penetration Grade)

Penetration grade bitumens are categorized based on their hardness and viscosity at 25°C. A lower penetration grade number indicates a harder, more viscous bitumen, while a higher number signifies a softer bitumen. These grades are widely used in asphalt paving and road construction, with the selection of the appropriate grade depending on climatic conditions and traffic load.

 

40/50

This grade is one of the hardest types of penetration bitumen.

Applications: Primarily used in very hot regions with heavy traffic, or in the production of asphalt mixtures requiring high resistance to deformation. Also used in some industrial and waterproofing applications.

 

60/70

A common grade with medium hardness, offering a balance between hardness and flexibility.

Applications: Suitable for regions with temperate climates, for paving highways, airports, and high-traffic surfaces.

 

85/100

This grade is softer than 60/70 and offers greater flexibility.

Applications: Primarily used in colder regions to prevent asphalt cracking due to thermal expansion and contraction. Also used in protective asphalt layers and surface courses.

 

120/150

This grade is much softer and more flexible than the previous grades.

Applications: Suitable for very cold regions or for specific applications requiring exceptionally high flexibility, such as polymer-modified asphalt or sealants.

 

180/200

One of the softest penetration grades, with high fluidity.

Applications: Typically used for cold asphalt mixes, bitumen emulsions, and some industrial applications requiring more fluid bitumen.

 

200/300

This grade is even softer than 180/200 and is used for specific applications requiring very low viscosity.

Applications: Similar to the 180/200 grade, but where greater fluidity is needed.

 

160/220

A soft penetration grade, commonly used in general asphalt paving and in regions with cold to temperate climates.

 

250/330

The softest grade in this category, with very low viscosity.

Applications: Primarily used for producing bitumen emulsions, cold asphalt mixes, or as a raw material in certain industrial processes.

 

Table 1: Technical Specifications of Blown Bitumen Grades (Penetration Grade – ASTM/AASHTO)

Blown Bitumen Grades Based on EN Standard (Penetration Grade)

This classification is also based on penetration, but defined according to European Standards (EN). Like ASTM/AASHTO, these grades indicate the hardness of bitumen and are common in road construction and building applications in Europe.

 

30/45

One of the hardest penetration grades according to the EN standard.

Applications: In very hot regions or for asphalt layers requiring high resistance to deformation.

 

35/50

Harder than 40/60, suitable for specific applications requiring greater hardness.

Applications: In hot regions or for pavements subjected to high mechanical stresses.

 

40/60

A relatively hard penetration grade.

Applications: Common in asphalt paving in hot to temperate climates, for asphalt wearing courses.

 

50/70

A balanced penetration grade with medium hardness.

Applications: The most commonly used grade in asphalt paving in most regions with temperate climates, suitable for various road construction projects.

 

70/100

Softer than 50/70, with greater flexibility.

Applications: In colder regions to reduce the risk of asphalt cracking due to temperature changes, and also in pavement base layers.

 

100/150

A soft grade, with high flexibility.

Applications: In very cold regions or for specific applications requiring exceptionally high flexibility.

 

Table 2: Technical Specifications of Blown Bitumen Grades (Penetration Grade – EN)

Blown Bitumen Grades Based on Performance Grade (PG)

The Performance Grade (PG) system is a newer approach to classifying bitumen based on its actual performance under various climatic conditions. These grades specify the higher and lower temperatures that bitumen can withstand without permanent deformation (at high temperatures) or cracking (at low temperatures). The first number indicates the maximum pavement service temperature, and the second number indicates the minimum pavement service temperature (with a negative sign).

 

PG-52/10

This grade indicates bitumen suitable for performance at high temperatures up to 52°C and low temperatures down to -10°C.

Applications: Generally suitable for regions with temperate to cold climates.

 

PG-58/22

Indicates suitable performance at high temperatures up to 58°C and low temperatures down to -22°C.

Applications: For regions with hot and colder climates, experiencing high temperature fluctuations.

 

PG-58/16

Suitable performance at high temperatures up to 58°C and low temperatures down to -16°C.

Applications: For regions with hot and temperate climates.

 

PG-58/10

Suitable performance at high temperatures up to 58°C and low temperatures down to -10°C.

Applications: For regions with hot and temperate climates.

 

PG-64/22

Suitable performance at high temperatures up to 64°C and low temperatures down to -22°C.

Applications: For very hot and cold regions, requiring high resistance to deformation in heat and cracking resistance in cold.

 

PG-64/16

Suitable performance at high temperatures up to 64°C and low temperatures down to -16°C.

Applications: For very hot and temperate regions.

 

PG-64/10

Suitable performance at high temperatures up to 64°C and low temperatures down to -10°C.

Applications: For very hot and temperate regions.

 

PG-70/10

Suitable performance at high temperatures up to 70°C and low temperatures down to -10°C.

Applications: For very hot regions.

 

PG-70/16

Suitable performance at high temperatures up to 70°C and low temperatures down to -16°C.

Applications: For very hot regions with a need for flexibility in cold.

 

Table 3: Technical Specifications of Blown Bitumen Grades (Performance Grade – PG)

Blown Bitumen Grades Based on Viscosity Grade (VG)

The Viscosity Grade (VG) system classifies bitumen based on its absolute viscosity at 60°C. This system is particularly common in Asia and the Middle East, serving as an alternative to the penetration grading system. A higher VG number indicates a stiffer and more viscous bitumen.

 

VG10

This grade has the lowest viscosity among VG grades.

Applications: Suitable for cold and temperate regions, or for producing bitumen emulsions and cold asphalt mixes.

 

VG20

A medium viscosity grade.

Applications: The most common grade in temperate to hot climates, for asphalt wearing and base courses.

 

VG30

Higher viscosity than VG20, suitable for hotter regions.

Applications: In hot regions with moderate to heavy traffic, to increase the asphalt’s resistance to deformation.

 

VG40

The highest viscosity in this category.

Applications: For very hot regions with heavy traffic, requiring very high asphalt stability against rutting.

 

Table 4: Technical Specifications of Blown Bitumen Grades (Viscosity Grade – VG)

 

Conclusion and Importance of Selecting the Appropriate Grade

Blown bitumen, due to its specific production process, exhibits enhanced properties including high thermal resistance, low penetration, and suitable flexibility. These characteristics make it ideal for a wide range of applications in various industries, especially road construction and waterproofing. The different classifications of blown bitumen, including Penetration Grade (ASTM/AASHTO and EN), Performance Grade (PG), and Viscosity Grade (VG), allow engineers and specialists to select the most suitable bitumen grade based on environmental conditions, project type, and performance requirements.

The correct selection of blown bitumen grade not only directly impacts the project’s performance and durability but also helps optimize costs and extend the service life of the structure. By thoroughly understanding the properties of each grade and comparing them with project needs, the best results can be achieved.