Viscosity testing to determine the strength of the asphalt is done by grading original (as-supplied) asphalt binder samples (called AC grading) or by grading aged residue samples (called AR grading). Based on the results of a rolling thin film oven test, the AR viscosity test evaluates the viscosity of aged residue. A binder is graded according to the properties it possesses before going through the HMA production process. This grading system was developed in order to model the asphalt binder behaviour in HMA pavements after the asphalt binder had undergone a typical HMA manufacturing process.

Advantages and Disadvantages of Viscosity Grades are stated below:

Advantages Disadvantages
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 temperature
  • 60°C (140°F) – high pavement temperature
  • 135°C (275°F) – HMA mixing temperature
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.
viscosity grade bitumen

We have two methods of grading:

  • Standard Bitumen Viscosity Grade (AC-Grades), in which the Viscosity of the standard bitumen (asphalt) is measured at 60 ºC (140 ºF).
  • RTFOT Bitumen Viscosity Grade (AR-Grades), in which the Viscosity of bitumen (asphalt) is measured at 60 °C (140 °F) after the roll of thin-film oven test.
Standard Grading based on Original Asphalt (AC) Grading based on Aged Residue (AR)
AASHTO M 226 AC-2.5 AC-5 AC-10 AC-20 AC-30 AC-40 AR-10 AR-20 AR-40 AR-80 AR-160
ASTM D 3381 AC-2.5 AC-5 AC-10 AC-20 AC-30 AC-40 AR-1000 AR-2000 AR-4000 AR-8000 AR-16000
Standard Grades Minimum of Absolute Viscosity, Poise@ 600°C Approximate penetration grade
IS73:2013 VG 10 800 80-100
VG 20 1600 -
VG 30 2400 60-70
VG 40 3200 30-40/40-50

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

  • 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) will improve performance at high temperatures.
  • With a requirement for minimum viscosity at 135°C, the compaction of tender asphalt mixtures created by push and shove under the roller wheels have also been addressed. This will minimize the tender mix problems in the field.
  • With the adoption of viscosity-graded paving bitumen specifications, the number of total tests will also decrease to seven without compromising bitumen quality, and there will also be no new tests required for implementing this specification. To know more about this, contact best bitumen suppliers in the UAE.

Viscosity Grade Bitumen Specification (ASTM D3381-09)

Property Units AC-10 AC-20 AC-30 AC-40 Test 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)

Property Units VG-10 VG-20 VG-30 VG-40 Test 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

Uses of Viscosity Grade Asphalt

  • Bitumen with high viscosity is widely used in cold climates for surface-dressing, paving, and a variety of other spraying applications. Also, it is used to make modified bitumen products and bitumen emulsions.
  • A very cold climate prefers the use of VG-10 instead of 80/100 penetration bitumen grade for spraying applications like surface dressing and paving. Also, it is used to produce modified bitumen as well as bitumen emulsion.
  • In cold climates and high altitudes, VG-20 is used for paving.
  • VG-30 is recommended for constructing extra heavy-duty Bitumen pavements that have to withstand significant traffic loads. As an alternative to 60/70 penetration bitumen grade.
  • When high-stress areas are present such as intersections, toll booths, and truck parking lots, VG-40 is used instead of 30/40 penetration grade. Because bitumen mixes have a higher viscosity, they can be produced in stiffer forms to better withstand shoving caused by higher temperatures and heavy traffic.

Gulf Bitumen

With respect and confidence, we are well known for providing exceptional service quality, technical expertise, customer support, and rapid and accurate response to the customer's needs.



Get notified about new releases.