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Viscosity Grade Bitumen Definition

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. Table 1 lists key advantages and disadvantages of the viscosity grading system. Huei Jie Oil is a Big supplier of Viscosity grade Bitumen In Middle East.



Advantages and Disadvantages of Viscosity Grading as stated below

Unlike penetration depth, viscosity is a fundamental engineering parameter. The principal grading (done at 25°C (77°F)) may not accurately reflect low-temperature asphalt binder rheology.
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. 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.
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)). The testing is more expensive and takes longer than the penetration test
Testing equipment and standards are widely available.  

The new method of grading the product has now rested on the viscosity of the Bitumen (at 60°C and 135°C). The new grades have thus evolved with nomenclature:


StandardGrades Minimum of AbsoluteViscosity, Poise@ 600°CApproximate penetration grade
IS73:2013 VG 10 800 80-100
IS73:2013 VG 20 1600
IS73:2013 VG 30 2400 60-70
IS73:2013 VG 40 3200 30-40/40-50

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

  • Performance at high temperatures by adopting a viscosity-graded bitumen specification (based on viscocity 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.

Viscosity grades Bitumen are categorized according to Viscosity (degree of fluidity) grading. The higher the grade, the stiffer the Bitumen. 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.

Viscosity Grade Bitumen Specification (ASTM D3381-09)

PropertyUnitsAC-10AC-20AC-30AC-40Test Methods
Viscosity, 140°F (60°C) P 1000±200 2000±400 3000±600 4000±800 ASTM D-2171
Viscosity, 275°F (135°C), Min cSt 150 210 250 300 ASTM D-2171
Penetration, 77°F (25°C), 100g, 5sec, Min 0.1MM 70 40 30 20 ASTM D-5
Flash point, Cleveland open cup, Min °C 219 232 232 232 ASTM D-92
Solubility in trichloroethylene, Min %Wt 99 99 99 99 ASTM D-2042
Tests on residue from thin-film oven test:
  – Viscosity, 140°F (60°C), Max P 5,000 10,000 15,000 20,000 ASTM D-2171
  – Ductility, 77°F (25°C), 5cm/min, Min CM 50 20 15 10 ASTM D-113

Viscosity Grade Bitumen Specification (IS 73:2013)

PropertyUnitsVG-10VG-20VG-30VG-40Test Methods
Penetration at 25°C, 100g, 5sec, Min 0.1MM 80 60 45 35 IS 1203
Absolute viscosity at 60°C P 800-1200 1600-2400 2400-3600 3200-4800 IS 1206 (Part 2)
Kinematic viscosity at 135°C, Min cSt 250 300 350 400 IS 1206 (Part 3)
Flash point (Cleveland open cup), Min °C 220 220 220 220 IS 1448 [P : 69]
Solubility in trichloroethylene, Min %Wt 99 99 99 99 IS 1216
Softening point (R&B), Min °C 40 45 47 50 IS 1205
Tests on residue from thin film oven test:
  – Viscosity ratio at 60°C, Max   4 4 4 4 IS 1206 (Part 2)
  – Ductility at 25°C, Min CM 75 50 40 25 IS 1208


  • Viscosity Grade Bitumen 10

  • Viscosity Grade Bitumen 20

  • Viscosity Grade Bitumen 30

  • Viscosity Grade Bitumen 40

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