Abstract: This study examines the influence of needle flake aggregate content on the gradation of asphalt concrete aggregate, using a stepwise filling method and adopting skeletal stability as the sole criterion for assessing the quality of aggregate skeleton. A vertical vibration compaction device is used to prepare the specimens with needle flake contents of 0%, 20%, 25%, 30%, and 35%, respectively; Skeletal stability is evaluated comprehensively by combining the California bearing ratio (CBR) value, skeletal density, and porosity to determine the coarse aggregate gradation for different specimen sets. Aggregate gradation is designed using a composite gradation design method through blending coarse and fine fractions across the full-size range. The findings indicate that with an increasing content of needle-like aggregates, the stability of aggregate skeleton takes a trend of initial increase and then decrease. The optimal stability is observed at a needle flake content of 30%, while the least favorable is at the content of 35%.

Key words: hydraulic asphalt concrete, needle-shaped flake aggregate, aggregate gradation, vertical vibration compaction, CBR index