Is Pen 60/70 Suitable for Every Road Condition?

Pen 60/70 is one type of penetration-grade bitumen that is still widely used. However, penetration grade provides information about certain binder characteristics based on testing under specified conditions.

Performance Grade (PG), on the other hand, is designed to relate binder characteristics to the service temperature range and relevant pavement performance requirements.

Simply put:

Penetration Grade → classifies binder based on conventional test characteristics

Performance Grade → relates binder performance to pavement service conditions

Therefore, binder selection should not only ask:

“What penetration grade is this asphalt?”

It should also ask:

“What temperature, traffic loading, and environmental conditions will this binder have to handle?”

What Is Penetration Grade?

Penetration grade is a binder classification system based primarily on the results of a penetration test.

In this test, the depth to which a standard needle penetrates the binder is measured under specified temperature, loading, and testing conditions.

For Pen 60/70, the numbers correspond to a specified penetration range under the applicable test conditions.

In simplified terms:

Lower penetration value → relatively harder binder

Higher penetration value → relatively softer binder

However, this test only provides information about binder behavior under a particular set of conditions.

And that is where its limitation lies.

Why Isn’t Penetration Alone Enough?

Imagine two roads.

Road A

Located in an area with high pavement temperatures and subjected to heavy traffic.

Road B

Located in a cooler area with significant temperature variation.

Both roads may require binders with different performance characteristics.

The problem is that a penetration test is conducted at a specified test temperature, rather than across the entire range of temperatures that pavement may experience during its service life.

Therefore, penetration value alone cannot fully describe binder behavior under:

• High temperatures.
• Low temperatures.
• Repeated loading.
• Aging.
• Permanent deformation.
• Cracking.

What Is Performance Grade?

Performance Grade (PG) is a binder grading system that relates binder characteristics to pavement service temperatures and performance requirements.

For example:

PG 64-22

In simplified terms:

64 → high-temperature grade

-22 → low-temperature grade

These numbers should not be interpreted as meaning that the binder is guaranteed to perform perfectly at exactly those temperatures.

PG is part of a specification system that classifies binder performance under defined testing and conditions.

So PG attempts to answer a more practical question:

“What range of pavement temperatures is this binder designed to handle?”

Why Is High-Temperature Performance Important?

As pavement temperature increases, asphalt binder becomes softer.

If the binder becomes too soft while carrying repeated heavy traffic loads, the mixture can become more susceptible to permanent deformation.

One common form is:

Rutting

Rutting is permanent deformation that creates wheel-path depressions.

It can be influenced by:

• High pavement temperatures.
• Heavy traffic loading.
• Repeated loading.
• Binder that is too soft.
• Inappropriate mix design.
• Inadequate compaction.

Therefore, high-temperature binder performance is particularly important for heavily trafficked roads exposed to high pavement temperatures.

What About Low Temperatures?

At low temperatures, asphalt binder becomes increasingly stiff.

When pavement temperature drops significantly, thermal stresses can develop.

If the binder and mixture cannot adequately accommodate these stresses, cracking may occur.

One type of distress associated with low temperatures is:

Thermal Cracking

Cracking associated with thermal contraction as pavement temperature decreases.

Therefore, binder performance at low temperatures also needs to be considered.

What About Fatigue Cracking?

This distinction is important.

Fatigue cracking is primarily associated with repeated traffic loading and the structural response of the pavement.

Temperature and binder properties can influence mixture behavior, but fatigue cracking is not simply caused by “cold temperatures.”

So it would be misleading to say:

Cold temperature = fatigue cracking

A more accurate explanation is:

Fatigue cracking develops through accumulated damage from repeated loading and is influenced by pavement structure, materials, temperature, and other factors.

Pen 60/70 vs Performance Grade

Aspect	Penetration Grade	Performance Grade
Classification basis	Penetration test and other conventional parameters	Binder performance characteristics
Temperature	Tested under specified conditions	Related to pavement service temperatures
High-temperature behavior	Limited indication of performance	Evaluated through performance-related parameters
Low-temperature behavior	Limited information	Specifically considered
Aging	Does not fully characterize aging effects	Testing can include aged binder conditions
Main purpose	Conventional material classification	Relating binder to pavement service conditions

Does This Mean Pen 60/70 Is Outdated or Useless?

No.

This is important.

Penetration grade is not automatically “wrong” or “bad.”

It remains widely used and can be appropriate for certain applications when selected according to the applicable specifications and project conditions.

The problem occurs when:

One binder grade is assumed to be suitable for every condition without considering temperature, traffic, aging, and pavement characteristics.

So the message should not be:

Pen 60/70 = bad

It should be:

Binder selection without considering service conditions = risky.

Does a Higher PG Automatically Make a Road Last Longer?

No.

Binder is only one part of the pavement system.

A road can still fail if:

• Pavement structure is inadequate.
• Subgrade is weak.
• Drainage is poor.
• Mix design is inappropriate.
• Aggregate is unsuitable.
• Compaction is inadequate.
• Traffic exceeds the design assumptions.
• Construction quality is poor.

So don’t assume:

Higher PG = guaranteed longer pavement life.

Instead:

The binder needs to be appropriate for the service conditions and work together with a properly designed pavement system.

Why Can’t Indonesia Be Treated as One Climate?

Indonesia has highly varied road environments.

Differences can occur in:

• Temperature.
• Elevation.
• Rainfall.
• Solar radiation.
• Traffic loading.
• Vehicle types.
• Soil conditions.
• Drainage conditions.

Even within the same region, pavement requirements can differ because of traffic loading and environmental exposure.

Therefore, binder selection should consider the actual conditions of the project.

💡 Field Note

Don’t only ask: “What penetration grade is it?” Also ask: “What is the pavement service temperature?” “What is the traffic loading?” “What are the environmental conditions?” “What distress mechanism is most critical?” Then select the binder accordingly.

Field Note

Simple Analogy: Engine Oil

The logic is somewhat similar to choosing engine oil.

You don’t choose oil simply because:

“It’s engine oil.”

You consider:

• Operating temperature.
• Engine load.
• Operating conditions.
• Engine specifications.

The same basic thinking applies to asphalt binder.

Not every road requires exactly the same binder characteristics.

However, this analogy is only for explaining the concept. Engine-oil grading and asphalt-binder grading are not technically identical systems.

🎯 Key Takeaway

This does not mean Pen 60/70 cannot be used. The problem is assuming that one grade is suitable for every condition.

Penetration grade provides specific information about binder characteristics.

Performance Grade takes a more performance-oriented approach by relating binder characteristics to service temperatures and pavement performance requirements.

At high temperatures, the binder needs to help the mixture resist deformation.

At low temperatures, the binder needs to accommodate conditions that can contribute to cracking.

And everything still needs to be considered together:

Binder + Aggregate + Mix Design + Pavement Structure + Traffic + Climate + Construction

Therefore:

Different road conditions can require different binder characteristics.

As part of materials and pavement knowledge, Road Knowledge Hub ID places binder selection in the context of service conditions, materials, pavement structure, traffic, climate, and construction—not only a single penetration-grade number.

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