Effect of Aggregate Gradation on Workability of Hot Mix Asphalt Mixtures

Iman Haryanto, Osamu Takahashi


The ease of hot mix asphalt (HMA) mixture for compacting describes workability of the HMA mixture. This study developed a simple workability index (WI) and applied it to investigate effect of aggregate gradation on workability of HMA mixtures. Such mixture specimens were prepared with 6 types of aggregate gradation. The Marshall compactor and the steel roller compactor were employed to fabricate the specimens. The index was applied to identify workability of HMA specimens, even though they were fabricated with different compactors. WI of HMA mixture was low, when the fraction of stone or sand within the HMA mixture was high. Interlocking makes the aggregates difficult to displacement by compaction. WI of HMA mixture can be high, when the mixture uses aggregate gradation falling slightly above the Fuller curve. Sand particles within the aggregate gradation, contacts disappear between stone particles, so interlocking of stone particles is weak. As a result, the stone particles are easily shifted by the compaction load.


workability; index; HMA mixture; compaction; aggregate gradation; interlocking; aggregates packing

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