Effect Of Aggregate Gradation On Workability Of Hot Mix Asphalt Mixtures

The ease of using hot mix asphalt (HMA) for compacting underscores the workability of the HMA mixture. This study developed a simple workability index (WI) and applied it to investigate effects of aggregate gradation on workability of HMA mixtures. Such mixture specimens were prepared with 6 types of aggregate gradation. The Marshall compactor and 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 displace by compaction. WI of HMA mixture can be high, when the mixture uses aggregate gradation falling slightly above the Fuller curve. Sand particles within 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.