Australian Grade (C Class)
Australian Grade Bitumen, commonly referred to as C-Class Bitumen, is a performance-based asphalt binder classification system used primarily in Australia and some Asia-Pacific regions. Unlike penetration or viscosity grading systems, the C-Class system is designed based on pavement performance requirements, considering climate variation, heavy traffic loads, and long-term durability in road structures.
The letter “C” (Class) indicates that the bitumen is engineered to meet specific performance and rheological criteria suitable for Australian road standards, particularly under high-temperature conditions and heavy axle loads.
| Specifications of Australian Grade (C Class) Bitumen | |||||
|---|---|---|---|---|---|
| Property | Test Method | C170 | C320 | C450 | Unit |
| Viscosity at 60°C | AS 2341.10 | 170 | 320 | 450 | cSt |
| Penetration at 25°C | AS 2341.1 | 60-80 | 50-70 | 40-60 | 0.1 mm |
| Softening Point (Ring & Ball) | AS 2341.3 | 48-52 | 50-56 | 54-60 | °C |
| Flash Point | AS 2341.4 | >230 | >230 | >230 | °C |
| Specific Gravity at 25°C | AS 2341.2 | 1.02-1.05 | 1.03-1.06 | 1.04-1.07 | g/cm³ |
| Penetration Index | – | -1.0 to -0.5 | -0.8 to -0.3 | -0.5 to 0.0 | – |
Characteristics of C-Class Bitumen
C-Class bitumen grades are formulated with high stability and strong resistance to rutting, aging, and deformation. Some of their key features include:
- High temperature resistance
- Strong durability under heavy and commercial traffic
- Improved elastic recovery
- Superior resistance to cracking and oxidation
- Better adhesion to aggregates
These properties make it suitable for modern road networks where traffic intensity and environmental stress are significant factors.
Common C-Class Grades
Australian bitumen is generally categorized into different viscosity ranges, commonly recognized as:
The numbers represent the typical viscosity levels at 60°C, where a higher number indicates a stiffer binder suitable for hotter climates or heavier road loading.
For example:
- C170 is softer and more flexible—ideal for cooler areas or light traffic.
- C320 and C450 are harder grades used for high-temperature regions and heavy-duty roads, such as highways and industrial routes.
Applications of C-Class Bitumen
C-Class binders are widely used in:
- Hot Mix Asphalt (HMA)
- Heavy-duty highway pavements
- Urban and rural road networks
- Industrial and airport pavements
- Asphalt surfacing and wearing courses