What is penetration grade bitumen?
Bitumen classified by how far a standard needle penetrates the sample at 25 °C, written as 60/70 or 80/100. Lower numbers mean harder bitumen; 60/70 is the global paving workhorse.
Key points
- Measures needle penetration at 25 °C, in tenths of a millimetre.
- Lower number means harder binder.
- Says nothing about ageing or fatigue — pair it with softening point.
At a glance
| Test temperature | 25 °C |
|---|---|
| Load and time | 100 g for 5 seconds |
| Unit | Tenths of a millimetre |
| 60/70 | Global paving workhorse; temperate to hot climates |
| 80/100 | Softer; better in cold climates |
How the grade is measured
Penetration grading measures how far a standard needle under a 100 gram load sinks into a bitumen sample held at 25 °C for five seconds, expressed in tenths of a millimetre. A grade written as 60/70 means the result falls between 60 and 70 of those units.
Lower numbers mean harder, stiffer bitumen; higher numbers mean softer. The test is old, simple and empirical, which is both its weakness and the reason it remains in use worldwide.
Choosing a grade
Grade selection is mostly about climate and traffic. 60/70 is the global paving workhorse, suited to temperate and hot conditions and heavy loading. 80/100 is softer and better in colder climates where a stiff binder would crack.
Harder grades such as 40/50 appear in very hot regions and on heavily trafficked pavements where rutting is the dominant failure mode.
What penetration grading does not tell you
Because the test is at a single temperature, it says nothing directly about behaviour at service temperatures, ageing or fatigue. Viscosity grading and the Superpave performance grade system were developed to address exactly that.
In practice much of the world still trades on penetration grade, so a specification should pair it with softening point, ductility and solubility rather than relying on the penetration number alone.
Frequently asked questions
- What does 60/70 bitumen mean?
- That a standard needle penetrates the sample between 60 and 70 tenths of a millimetre at 25 °C. It is the most widely used paving grade globally.
- Which is harder, 60/70 or 80/100?
- 60/70. Lower penetration numbers indicate harder, stiffer bitumen; 80/100 is softer and better suited to colder climates.
- How does penetration grading compare to performance grading?
- Penetration grading is a single-temperature empirical test. Performance grading classifies binders by the temperature range over which they perform, which predicts service behaviour better but requires more testing.
Related terms
The laboratory document stating the measured composition of a specific parcel — purity, contaminants, moisture. It refers to the lot actually shipped, unlike a typical or datasheet analysis which describes what a plant usually produces.
The seller delivers the goods on board the vessel at the named load port and clears them for export. Risk and cost transfer to the buyer once the cargo is loaded, so the buyer arranges and pays for ocean freight and insurance.
Trading this, or trying to price it?
CommoFlow sources, buys, sells and ships physical commodities from the Middle East, Central Asia, the Caucasus, Africa and Australia. If a contract term is deciding your economics, our desk deals with it daily.
Contact our desk