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Viscosity Grade (VG) Bitumen ​

What is Viscosity Grade bitumen?

With the increased use of designed dense mixes, increased traffic volume and loading, higher road users’ expectations and changes in crude quality, new test method was felt essential lately. Hence new standards such as absolute viscosity at 60°C and 135°C were developed.

Bitumen is graded based on absolute viscosity at 60ºC or kinematic viscosity at 135ºC. The SI physical unit of dynamic viscosity is Poise and kinematic viscosity is expressed in Centi Stokes. Pure bitumen has been graded based on AASHTO-M226 and ASTM-D3381 standards. According to viscosity (degree of fluidity) grading, higher the grade, stiffer the Bitumen. Tests are conducted at 60˚C and 135˚C, which represent the temperature of road surface during summer (hot climate) and mixing temperature respectively.

Viscosity Grade Bitumen, often known as Asphalt, is a standard petroleum grade Asphaltum that is manufactured from fractional vacuum bottom from crude oil distillation that is frequently used as paving for road construction and asphalt pavements manufacturing with superior properties.

Viscosity grade bitumen is a petroleum grade bitumen derived from crude oil. Viscosity Grade bitumen is designed to take care of lowest temperature (responsible for cracking) and maximum temperature (responsible for rutting). This grade of bitumen is tested and classified differently from other types of bitumen. After production, refiners test the VGs by a viscometer to classify them according to their level of viscosity in various temperatures.

Bitumen is classified according to its absolute viscosity at 60 degrees Celsius or its kinematic viscosity at 135 degrees Celsius. The nominal viscosity preceded by a V, is often given in specifications for viscosity graded bitumen.

Viscosity Grade (VG) Bitumen most used grades:

GradeViscosity Range at 60°C (Absolute Viscosity) Typical Applications ∞
VG-10 Bitumen 800-1200 Recommended for road construction in cold regions Ideal for spraying Used in production of bitumen emulsion
VG-20 Bitumen 1600-2400 Used in cold regions for road construction
VG-30 Bitumen 2400-3600 Maximizes asphalt performance in hot regions A more reliable choice than bitumen pen 60/70
VG-40 Bitumen 3200-4000 Works in areas with high traffic loads Well suited for road construction in hot weather

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Viscosity Grade (VG) Bitumen most used grades:

  • AC-2.5
  • AC-5
  • AC-10
  • AC-20
  • AC-30
  • AC-40
  • AR-10
  • AR-20
  • AR-40
  • AR-80
  • AR-160
  • VG-10
  • VG-20
  • VG-30
  • VG-40

Viscosity grading

Viscosity grades Bitumen are categorized according to Viscosity (degree of fluidity) grading. In Viscosity Grade, Viscosity tests are conducted at 60°C and 135°C, which represents the temperature of road surface during summer and mixing temperature respectively. The penetration at 25°C, which is annual average pavement temperature, has been also retained in Specifications. The viscosity test results in four VG grades of bitumen including VG10 Bitumen, VG20 Bitumen, VG30 Bitumen, and VG40 Bitumen. The higher the number, the harder the bitumen in the viscosity grading system.

Viscosity grading can be done on original (as-supplied) asphalt binder samples (called AC grading) or aged residue samples (called AR grading). The AR viscosity test is based on the viscosity of aged residue from the rolling thin film oven test. With AC grading, the asphalt binder is characterized by the properties it possesses before it undergoes the HMA manufacturing process. The AR grading system is an attempt to simulate asphalt binder properties after it undergoes a typical HMA manufacturing process and thus, it should be more representative of how asphalt binder behaves in HMA pavements.

Application

Viscosity Grade Bitumen (Asphalt) is a standard grade asphaltum usually used as a Paving Grade asphaltum suitable for road construction and for the production of asphalt pavements with superior properties. This grade is mainly used in the manufacture of hot mix asphalt for bases and wearing courses, and possesses characteristics and qualities unique sand quite different from other agents. They achieve very flexible and tenacious connections with other materials due mainly to viscoelastic response of asphaltum, which behavior depends on how fast charges are applied.

VG Bitumen is primarily employed in the production of hot mix asphalt for bases and wearing courses, and it has traits and properties that distinguish it from other agents. They produce exceptionally flexible and persistent connections with other materials, owing mostly to Asphaltum’s viscoelastic reaction, its usage and the behavior of which are temperature dependent. In addition, Viscosity Grade Bitumen is widely used in spraying applications such as surface-dressing and paving in very cold climate. It is also used to manufacture Bitumen emulsion and Modified Bitumen products.

Each grade of viscosity bitumen has certain applications and performs differently in various temperatures.

Bitumen VG10 is a standard viscosity grade bitumen usually used as a paving grade bitumen suits repairing and spraying applications and suitable for road construction and surface dressing of pavements in very cold climate as per following technical specification.

Due to better resistance to temperature changes, particularly in cold regions, bitumen VG10 can achieve higher efficiency in road projects. It can be used instead of 80/100 penetration bitumen grade and also used to produce Bitumen Emulsion and Modified Bitumen products.

Bitumen VG20 is a standard viscosity grade bitumen used for paving in cold climate & high altitude regions.

Bitumen VG30 is a standard viscosity grade bitumen especially used as a paving grade bitumen suitable for heavy duty road construction where extra heavy traffic is expected to tolerate significant traffic loads as per following technical specification.

It offers better quality and performance for road projects and can be used instead of 60/70 penetration bitumen grade.

Bitumen VG40 is a standard viscosity grade bitumen usually used for heavy duty road construction and highly stressed areas such as intersections, near toll booths and truck parking lots to endure substantial traffic loads and high temperature as per following technical specification.

Due to the higher viscosity, accuracy, predictability, and durability of VG40, stiffer bitumen mixes can be produced to improve paving resistance to shoving and other problems related to higher temperature and heavy traffic loads. VG40 is used in countries with higher temperatures and heavy traffic loads, such as Indian and African countries.

It can be used instead of 30/40 penetration bitumen grade.

Benefits / Advantages of VG Bitumen over Penetration grade:

  • VG system unlike penetration depth, is based on fundamental engineering parameter (not empirical) i.e. actual performance on road and not on the empirical properties.
  • Test temperatures correlate well with: 25°C (77°F) – average pavement temp.60°C (140°F) – high pavement temp.135°C (275°F) – HMA mixing temp.
  • Temperature susceptibility (the change in asphalt binder rheology with temperature) can be somewhat determined because viscosity is measured at three different temperatures (penetration only is measured at 25°C (77°F)).
  • Testing equipment and standards are widely available.
  • Viscosity is measured at 60degree C and 135degree C, which takes care of both low and high-temperature susceptibility of the binder, which is not possible with penetration value at 25degreeC. Hence pavement engineers, contractors/consultants can have a better understanding of the binder’s performance in the field.
  • Any two same viscosity grade bitumen would give similar rutting performance in hot summer unlike Penetration Grade.
  • Greater Mix in ease design and greater ease of handling to customers as Viscosity Value at two different temperatures (60degreeC and 135degree C) is available, which would enable users to measure accurate mixing and compaction temperatures.
  • Longer Durability : The pavement made from VG Bitumen will have better performance, because Viscosity value at 135 degree C gives sufficient idea about mixing and compaction temperature and as a result pavement life is improved.
  • Minimum specified Kinematic Viscosity value at 135degree C helps to minimize the potential of tender mixes during construction.
  • Viscosity graded bitumen are suitable for a wide range of temperature: 25degreeC for raveling/fatigue cracking. 60degreeC for rutting and 135degreeC for construction (mixing and compaction).
  • IS 73 has only 7 tests to evaluate a sample compared to 14 tests in penetration grade system. This reduces time and cost of testing without sacrificing its quality.
  • Takes Higher Traffic: Penetration test was developed in the era of significantly lower pavement loading. In the past, truck weights were less than 30 tons with tire pressure of 75 PSI. Today truck weight has increased to 35 tons with tire pressure of 125 PSI and increased traffic with extreme weather conditions. Therefore, to cope up with these changes shift from PEN Grade to VG Grade is required.

Disadvantages of Viscosity Grading as stated below

  • The principal grading (done at 25°C (77°F)) may not accurately reflect low-temperature asphalt binder rheology.
  • When using the AC grading system, thin film oven test residue viscosities can vary greatly with the same AC grade. Therefore, although asphalt binders are of the same AC grade they may behave differently after construction.
  • The testing is more expensive and takes longer than the penetration test.

Viscosity grade VS. Penetration grade

In comparison to penetration grade bitumen, VG bitumen grades are more reliable and easier to handle (both mixing and compaction) and their resistance to temperature changes is more predictable.

Viscosity grade over penetration grade several key issues are addressed, like:

  • Performance at high temperatures by adopting a viscosity-graded bitumen specification (based on viscosity at 60 °C), in place of the current penetration-graded specification (based on penetration at 25 °C)
  • Issues relating to compaction, which the tender asphalt mixtures create as push and shove under the roller wheels, have also addressed by having a requirement of minimum viscosity at 135°C, it will be helpful in minimizing the tender mix problems in the field.
  • Adoption of viscosity-graded paving bitumen specifications will also reduce the number of total tests to 7 without compromising the quality of bitumen and also no new tests are required in implementing this specification.

Packing

Rumays supplies Viscosity Grade Bitumen in all grades VG10, VG20, VG30 and VG40.

These grades can be supplied in different packages including bulk and Drums.

Drums are available in different sizes of 150 Kg, 180 Kg, 200 Kg, 240 Kg and any other customized size.

Embossing customer’s Logo on drums is applicable as per request.

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