Numerous studies have shown that the air void ratio of constructed asphalt mixture has a significant effect on the durability and long-term performance of asphalt pavements. In United States, asphalt mixtures are designed for 4% air voids and are typically constructed at 7% air voids or higher in the mat and often exceed 10% in longitudinal joints. Recent efforts by Indiana Department of Transportation and Purdue University have shown that a new mix design method, called Superpave 5, can enhance the compaction of asphalt pavement by small adjustments of the aggregate gradation. The result is a laboratory mix design at 5% air voids and successful compaction of the mixtures in the field at the same 5% air voids, a significant decrease compared to current practice. Motivated by the work done on developing this new mix design, an investigation is performed to better understand the effects of aggregates gradation on compaction. In this investigation, aggregate gradation is characterized using Bailey method parameters and the distance to the maximum dense line. The compactability of mixtures is evaluated using gyratory compaction curves obtained in laboratory conditions. The relationship between the aggregate gradation and compactability is analyzed using correlation analysis. The results show that the compactability of asphalt mixtures is clearly related to Bailey method parameters and the distance to maximum dense line. The relationships between aggregate gradation and compactability identified in this study can be used to design and construct denser and more durable asphalt pavements. Keywords: high-density asphalt mixture, compaction, aggregate gradation, Bailey method

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