Penetration grade bitumen is a paving-grade bitumen classified by how hard or soft it is. The grade is determined by the penetration test (Bitumen Penetration Test), which measures how far a standard needle penetrates the bitumen under controlled conditions.

Test conditions:

  • Temperature: 25°C
  • Load: 100 g
  • Time: 5 seconds

The penetration value is expressed in 0.1 mm (dmm).

Common penetration grades

Grade Penetration (dmm) Hardness Typical use
20/30 20–30 Very hard Heavy-duty roads, hot climates
35/50 35–50 Hard High-traffic pavements
40/50 40–50 Hard Road construction
50/70 50–70 Medium-hard Roads in warm climates
60/70 60–70 Medium Most common paving grade
70/100 70–100 Softer Moderate and cold climates
80/100 80–100 Soft Flexible pavements
100/150 100–150 Very soft Cold climates

How it works

  • Lower penetration number = harder bitumen
  • Higher penetration number = softer bitumen

For example:

  • Bitumen 35/50 is harder than Bitumen 60/70.
  • Bitumen 80/100 is softer than Bitumen 50/70.

Main applications

Penetration grade bitumen is widely used for:

  • Asphalt pavement
  • Highways
  • Airport runways
  • Parking lots
  • Urban roads

The appropriate grade depends on climate, traffic load, and pavement design. Hot regions generally use harder grades (e.g., 35/50 or 50/70), while colder regions often use softer grades (e.g., 70/100 or 80/100) to reduce cracking.