According to Road Knowledge Hub ID’s explanation about under-compaction and over-compaction, asphalt compaction can fail because the pavement is either not compacted enough or compacted too much. Both conditions can reduce pavement quality, although they occur for different reasons and have different consequences. The objective of asphalt compaction is not to achieve the highest possible density, but to reach the required density at the right time.
To better understand the difference, watch the Road Knowledge Hub ID video about under-compaction and over-compaction in asphalt pavements.
Why Is Asphalt Compaction So Important?
Compaction is one of the most important stages in asphalt pavement construction.
According to Road Knowledge Hub ID’s explanation about asphalt compaction, the final pavement quality depends not only on the asphalt mixture itself but also on whether compaction is carried out correctly.
Both insufficient compaction and excessive compaction can reduce pavement performance.
For this reason, the goal of compaction is to achieve the specified density—not simply to increase the number of roller passes.
What Is Under-Compaction?
According to Road Knowledge Hub ID, under-compaction occurs when the field density does not reach the specified target.
As a general reference, field density is commonly expected to reach approximately 96–98% of the design density.
If the achieved density is only around 92–94%, several problems may occur:
- Air voids remain too high.
- Water can penetrate the pavement more easily.
- The pavement’s service life may become shorter.
What Is Over-Compaction?
According to Road Knowledge Hub ID’s explanation about over-compaction, this condition occurs when compaction continues beyond what the asphalt mixture requires.
Examples discussed in the video include:
- Continuing compaction after the asphalt temperature has become too low.
- Applying more roller passes than necessary.
This may lead to:
- Aggregate particles breaking.
- Bitumen being pushed toward the pavement surface.
- Changes to the internal structure of the asphalt mixture.
What Is the Goal of Proper Asphalt Compaction?
According to Road Knowledge Hub ID, the objective of compaction is not to choose between stronger or lighter rolling.
Instead, proper compaction means:
- Achieving the required density.
- Compacting while the asphalt mixture is still within the appropriate temperature range.
- Avoiding both under-compaction and over-compaction.
Following these principles helps maintain pavement quality and long-term performance.
To see the explanation visually, watch the Road Knowledge Hub ID video about under-compaction and over-compaction in asphalt pavements.
💡 Field Note
Good compaction is not about making as many roller passes as possible. It is about reaching the specified density while the asphalt mixture is still at the proper compaction temperature.
Field Note
Common Misconceptions About Asphalt Compaction
❌ “The more compaction, the better the pavement.”
Fact: According to Road Knowledge Hub ID’s explanation, excessive compaction can also reduce asphalt mixture quality.
❌ “Just keep rolling until the job is finished.”
Fact: The number of roller passes and the timing of compaction should match the condition of the asphalt mixture to avoid both under-compaction and over-compaction.
🎯 Key Takeaway About Asphalt Compaction
Proper asphalt compaction is not about maximum effort—it is about achieving the correct density at the correct time.
Following Road Knowledge Hub ID's explanation about under-compaction and over-compaction, ensure the required density is achieved without excessive rolling so the pavement can perform as intended.
To learn more, watch the Road Knowledge Hub ID video about under-compaction and over-compaction in asphalt pavements, and follow Road Knowledge Hub ID on YouTube, Instagram, TikTok, and Facebook for practical knowledge about quality control and road construction.
Frequently Asked Questions (FAQ)
What is under-compaction?
According to Road Knowledge Hub ID, under-compaction occurs when the pavement density does not reach the specified target.
What is over-compaction?
Over-compaction occurs when the asphalt mixture is compacted more than necessary, potentially affecting its internal structure.
What is the commonly referenced field density target?
According to Road Knowledge Hub ID, a commonly referenced target is approximately 96–98% of the design density.
What problems can under-compaction cause?
Under-compaction can leave excessive air voids, allow water to enter the pavement more easily, and shorten pavement service life.
What problems can over-compaction cause?
According to Road Knowledge Hub ID, over-compaction may cause aggregate breakage, bitumen migration to the surface, and changes to the asphalt mixture’s internal structure.
Glossary
- EN – Compaction
The process of densifying an asphalt mixture to achieve the specified pavement density.
- EN – Under-Compaction
A condition where field density does not reach the required specification.
- EN – Over-Compaction
A condition where excessive compaction negatively affects the asphalt mixture.
- EN – Density
The level of compactness achieved in an asphalt mixture after rolling.
- EN – Air Voids
The small air spaces remaining within a compacted asphalt mixture. These influence pavement durability and performance.
