Viscosity
Grade (VG) bitumens
Bitumens are divided into different categories based on the
production method, compounds, and physical properties, such as penetration
bitumen and PG and viscosity (VB) bitumens. In this section, we will review the
Viscosity Grade Bitumens.
This type of bitumen is used to make Hot-mix Asphalt. It has more
thermoplastic properties than other bitumens, so it is harder in cold weather
and softer in warm weather. Nowadays some countries (used mostly in India) use
this type of bitumen which is called viscosity Grade bitumen.
The viscosity bitumens are defined according to the
ASTM standard D3381-09 and the AASHTO method M226-8.
Viscosity bitumens are classified, into VG-10, VG-30,
and VG-40 categories based on the Viscosity test results.
Bitumen viscosity is an important and fundamental
property of bitumen, which indicates how bitumen behaves at a specific
temperature or a temperature range.
Absolute viscosity is introduced based on poise and
Kinematic viscosity in terms of Centistokes (cSt).
The higher the temperature, the softer the bitumen.
In this type of bitumen, the viscosity test is measured at 60 and 135 degrees
Celsius, which is respectively the road surface temperature (RST) in the summer
and the asphalt mixing temperature.
VG-10 Bitumens
It is used in spraying applications such as surface
dressing or cold weather conditions and is almost equivalent to the 85-100
bitumens.
VG-30 Bitumens
For use in Hot Mix Asphalt (HMA), it is approximately
60-70 bitumens.
VG-40 Bitumens
For use in asphalt mixtures and HMA, and are
approximately 40-50 bitumens.