What is Viscosity Grade Bitumen?
Viscosity Grade Bitumen (Asphalt ) is a standard grade Bitumen especially used as a Paving Grade Bitumen suitable for road construction and for the production of asphalt pavements with superior properties. This mainly uses in manufacture of hot mix asphalt for bases-wearing courses, possesses characteristics, qualities unique sand quite different from other agents. They achieve very flexible and tenacious connections with other materials due mainly to visco elastic response of bitumen. It depends on charges rate.
Viscosity Grade Bitumen supplied by pub-ltd is petroleum grade bitumen, manufactured from fractional / vacuum distillation of crude oil, which practical usages and behavior varies according to its temperature. Our bitumen also is produced from vacuum residue (short residue) feedstock.
VG is specified by methods described ASTM Standard D3381-09 _ AASHTO M226-80 (2008). Also it`s spec covers asphalt graded by Viscosity at 60 C (140 °F).
Methods of grading:
In 1960s an asphalt grading system was created who compines rational-scientific viscosity test. Furthermore, replaced empirical penetration test as asphalt binder characterization.
Viscosity grading quantifies the following asphalt binder specs:
- Penetration depth of 100 g needle uses for 5 seconds at 25° C.
- Solubility in trichloroethylene.
- Flash point temperature.
- Viscosity at 60°C
- Viscosity at 135°C
- Ductility at 25°C
- Thin-film oven test(effects of short-term aging)
Standard Viscosity Grade Bitumen (AC):
With AC grading, asphalt binder is specify by properties it possesses before it undergoes HMA making process. Asphalt binder samples Viscosity of standard bitumen measured at 60 ºC .
RTFOT Viscosity Grade Bitumen (AR):
The AR viscosity test is based on the viscosity of aged residue from the rolling thin film oven test. 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.
Viscosity grade have a thermoplastic property which causes material to soften at high temperatures and to harden at lower temperatures. This unique temperature/ viscosity relationship is important when determining performance parameters like adhesion, rheology, durability and application temperatures of bitumen. VG Bitumen spec, emphasis is on Bitumen ductility.
Viscosity Grade Bitumen:
- surface spraying dressing.
- Paving in very cold climate.
- instead of bitumen 80/100 .
It`s also uses in Bitumen Emulsion and Modified Bitumen products.
Uses for paving in cold climate & high altitude regions.
Especially uses to construct extra heavy duty Bitumen pavements that need to tolerate significant traffic loads. It`s an alternative for bitumen 60/70
Highly stressed areas applications, like intersections, near toll booths and truck parking lots instead of 30/40 penetration grade. Because of high viscosity, stiff Bitumen mixes can built to amend stability shoving and other problems related to high temperature and heavy traffic loads.
Viscosity Grade Bitumen benefits:
1. Minimum penetration values were retained in the viscosity grading system to maintain acceptable performance (in terms of resistance to fatigue cracking) at the yearly average service temperature of 25˚C.
2. Unlike penetration grades, same viscosity grade bitumen gave a similar rutting performance in hot weather.
3. Minimum specified values of kinematic viscosity at 135˚C helped to minimize the potential of tender mixes during construction.
4. Viscosity grade bitumen were suitable for a wide range of temperatures: 25˚C for raveling/fatigue cracking; 60˚C for rutting; also 135˚C for construction. Temperature change in asphalt binder rheology (susceptibility) can determined. Because viscosity measures at 3 different temperatures (penetration measured only at 25°C).
5. Minimum specified penetration at 25˚C and minimum specified kinematic viscosity at 135˚C established maximum allowable temperature susceptibility (slope of temperature versus stiffness line).
6. Viscosity measured at 2 temperatures, it causes rational, compaction and exact asphalt mixing. In addition, it`s viscosity is 170 and 280 centistokes, respectively.