Bitumen
Bitumen Standards & Grades
The four grading systems in commercial use — penetration, viscosity, performance and Australian standard — and how to read a specification.
There is no single global standard for bitumen. Different regions grade the same material by different properties, which is why one product can be sold as 60/70, as AC-20 and as PG 64-16 depending on the destination. Knowing which system your specification uses, and what it actually measures, avoids expensive substitution errors.
Penetration grading
The oldest and still the most widely used system across the Middle East, Africa, South Asia and much of Europe. A standard needle is loaded with 100 g for five seconds at 25 °C, and the depth it sinks, in tenths of a millimetre, is the penetration value. Grades are written as a range: 40/50, 60/70, 80/100, 85/100, 120/150.
It is a simple, reproducible consistency test, but it describes behaviour at one temperature only and says nothing about how the binder will perform in summer heat or winter cold.
Viscosity grading
Used principally in North America and parts of Latin America and India. Viscosity is measured at 60 °C, close to the maximum service temperature of a pavement, which makes it more relevant to hot-weather performance than penetration. AC grades are measured on the original binder; AR grades are measured after rolling thin film oven ageing, which better reflects the material as it leaves the paver.
Performance grading
Developed by the SHRP programme and codified in AASHTO M320. A PG 64-22 binder is certified to resist rutting up to 64 °C and cracking down to −22 °C. Rather than a single consistency measure, the specification applies dynamic shear rheometry, bending beam rheometry and pressure ageing to test the binder in the condition and at the temperatures it will actually experience.
Australian standard grading
AS 2008 classifies binders primarily by viscosity at 60 °C in pascal-seconds — Class 170, Class 320, Class 600 and the multigrades. The system was written for high ambient temperatures and heavy axle loads, and it is used in Australia, New Zealand and increasingly in comparable climates elsewhere.
Reference specifications
- EN 12591 — Bitumen and bituminous binders, paving grade specifications
- ASTM D946 — Penetration-graded asphalt cement for pavement construction
- ASTM D3381 — Viscosity-graded asphalt cement
- AASHTO M320 — Performance-graded asphalt binder
- AS 2008 — Australian standard for residual bitumen for pavements
- EN 13924 — Hard paving grade bitumens
Typical specification
| Hot climate, heavy traffic | 40/50 · AC-40 · PG 76-10 · Class 600 |
|---|---|
| Hot climate, normal traffic | 60/70 · AC-20 · PG 70-10 · Class 320 |
| Temperate climate | 80/100 · AC-10 · PG 64-22 · Class 170 |
| Cold climate | 120/150 · AC-5 · PG 58-28 |
Values are indicative and given for guidance. Contract specification is agreed in writing and certified per batch on the certificate of analysis issued with each shipment.
