Components, systems and materials › Construction materials › Viscosity-grade bitumen
Viscosity-grade bitumen
What it is
Viscosity-graded bitumen classifies paving binder by its viscosity.
Where it is used
Hot-mix asphalt layers such as dense bituminous macadam and bituminous concrete, surface dressings, and as a base for emulsions and modified binders.
How it works
Bitumen is a thermoplastic binder: hot, it is fluid enough to coat aggregate; cooled, it becomes a stiff, adhesive glue that holds the mix together and seals it against water. Its stiffness changes with temperature, so a grade must be stiff enough not to rut in hot summers and flexible enough not to crack in cold weather.
Types
- VG 10, VG 20, VG 30, VG 40
Materials
Petroleum bitumen.
IS 73 grades paving bitumen by absolute viscosity at 60 degrees C, giving VG 10, VG 20, VG 30 and VG 40; the higher the number, the stiffer the binder. Softer grades suit cold regions and sprays; stiffer grades suit hot climates and heavy traffic. Grade selection follows the pavement design guidelines and climate. EN 12591 grades paving bitumen in Europe by penetration.
Installation and QA steps
- Check test certificates for each tanker
- Heat to the mixing temperature range without overheating, which ages the binder
- Mix with dry, hot aggregate at the plant
- Lay and compact while the mix is within the specified temperature window
- Test binder content and density
- Overheating that hardens the binder and causes early cracking
- Bleeding from too much binder or too soft a grade
- Stripping where water breaks the bond to aggregate
- Rutting in hot weather with too soft a grade
Codes cited
- IS 73 (India): Paving bitumen: viscosity-graded (VG) specification.
- EN 12591 (Europe): Bitumen and bituminous binders: paving grade bitumens.
Cited by number only. We do not reproduce code text, tables or figures.
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Generic description for education. We do not name, endorse or compare manufacturers or products.
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