Effect of Aggregate Degradation on Specimens Compacted by Superpave Gyratory Compactor

Aggregate degradation during gyratory compaction may cause changes in the original gradation of the aggregate, and it may also affect volumetric requirements for Superpave Level I mix design. The effect of aggregate degradation on the design gradation and final volumetric properties of the asphalt mix compacted by the Superpave gyratory and Astec vibratory compactors was evaluated. Because vibratory compaction is an alternative compaction method that simulates field compaction, a vibratory compactor developed by Astec Industries, Inc., was used for comparison with the Superpave gyratory compactor. Aggregates with high and low Los Angeles abrasion losses were used to evaluate the effect of aggregate toughness or abrasion resistance on gradation change and volumetric properties. The changes in the amount of material passing the 0.075-mm sieve due to aggregate degradation during compaction were not significant enough to prevent specimens from meeting dust proportion requirements, regardless of whether low-or high-abrasion loss aggregates were used. A mix containing high-abrasion aggregate was less likely to meet restricted zone requirements than a mix using low-abrasion aggregate after degradation resulting from compaction.