Bitumen Grading Systems
Bitumen is sold in different grades that indicate its hardness, viscosity, and temperature performance. There are three main grading systems used globally.
1. Penetration Grade Bitumen
The oldest and most widely used system globally (UK, Europe, Australia, Asia).
How it works: A standard 100g needle is applied to a bitumen sample at 25°C for 5 seconds. The depth of penetration in units of 0.1mm (dmm) gives the grade.
| Grade | Penetration (dmm) | Consistency | Typical Use |
|---|---|---|---|
| 30/40 | 30–40 | Very hard | Very hot climates |
| 40/50 | 40–50 | Hard | Hot climates, heavy traffic |
| 60/70 | 60–70 | Medium | Most common worldwide |
| 80/100 | 80–100 | Soft | Cool climates |
| 120/150 | 120–150 | Very soft | Cold climates |
Lower penetration = harder bitumen = better for hot weather.
Higher penetration = softer bitumen = better for cold weather.
2. Viscosity Grade (VG) Bitumen
Used in India (IS 73:2013) and increasingly in other Asian countries.
| Grade | Equivalent Pen Grade | Key Properties |
|---|---|---|
| VG-10 | 80/100 | For spray applications, low-volume roads |
| VG-20 | 60/70 | General road use |
| VG-30 | 50/60 | Most common grade in India |
| VG-40 | 35/50 | High-traffic, high-temperature areas |
Classified by Absolute Viscosity at 60°C (in Poise).
3. Performance Grade (PG) Bitumen — Superpave
Used in USA and Canada (AASHTO M 320 / ASTM D6373).
Format: PG HH-LL
- HH = maximum pavement design temperature (°C)
- LL = minimum pavement design temperature (°C)
| Grade | High Temp | Low Temp | Typical Use |
|---|---|---|---|
| PG 52-34 | 52°C | -34°C | Cold climate, low traffic |
| PG 58-28 | 58°C | -28°C | Moderate climate |
| PG 64-22 | 64°C | -22°C | Most common US grade |
| PG 70-22 | 70°C | -22°C | High traffic |
| PG 76-10 | 76°C | -10°C | Very hot climate, heavy traffic |
How to Choose the Right Grade
- 1Check local specifications first — most regions have standard approved grades.
- 2Consider climate: Use harder grades (lower penetration, higher PG) in hot climates.
- 3Consider traffic: Heavier traffic requires harder, stiffer bitumen.
- 4For modified applications: Polymer Modified Bitumen (PMB) should be selected per AASHTO M 332 or local PMB specifications.
Grade Conversion Reference
| Pen Grade | VG Grade | Approx. PG Grade |
|---|---|---|
| 30/40 | — | PG 76-10 |
| 60/70 | VG-30 | PG 64-16 |
| 80/100 | VG-20 | PG 58-22 |
| 120/150 | VG-10 | PG 52-28 |
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