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Cover of Development of Aspects of a Design Procedure for Stone Mastic Asphalt
Development of Aspects of a Design Procedure for Stone Mastic Asphalt
  • Publication no: AP-T221-13
  • ISBN: 978-1-921991-69-1
  • Published: 16 January 2013

The report examines three aspects of stone mastic asphalt mix design. Gradation curves from Europe, US and Australia were reviewed and it was noted that with few exceptions they were relatively similar. The tolerances imposed on the mix designs were also studied to determine if Australian asphalt plants were capable of manufacturing good performing SMA.

The binder mastic plays a stronger role in SMA compared to dense graded asphalt (asphaltic concrete). A review of five mixes and data from a Queensland trial provided evidence to establish a lower limit for a binder mastic viscosity. There was insufficient data to determine an upper limit. Further data is required to verify the proposed limit and the test procedures.

The final part of the study examined methods to assess the stone-on-stone aggregate skeleton. The dilation approach was found to be unsatisfactory for the aggregates used in this study. SMA designed by the dilation approach tended to be permeable which was likely to lead to poor in-service performance.

The monitoring of shear stress during gyratory compaction did not offer additional insights into SMA behaviour. Use of packing theory to develop mix designs does not appear warranted.

The Bailey method appears to be a practical way of adjusting mix designs though optimisation of the gradations was not undertaken during this study.

The dry rodding process of determining voids in the coarse aggregate was useful for setting a target for controlling mix designs. However, only a limited number of mix designs were studied and further work is warranted.

  • 1. INTRODUCTION
  • 2. SMA GRADINGS
    • 2.1. Background
      • 2.1.1. Nomenclature
    • 2.2. SMA Gradations
      • 2.2.1. European SMA Gradations
      • 2.2.2. US SMA Gradations
      • 2.2.3. Australian SMA Gradations
      • 2.2.4. Summary
  • 3. Binder mastic
    • 3.1. Background
    • 3.2. Method
      • 3.2.1. Filler-binder Ratio
      • 3.2.2. Free and Fixed Binder Fractions
      • 3.2.3. Mastic Viscosity
    • 3.3. Results
      • 3.3.1. An Initial Study of Fillers
      • 3.3.2. Review of Australian SMA Mastics
      • 3.3.3. Gateway Trial Data
      • 3.3.4. Summary
  • 4. STONE-ON-STONE SKELETON
    • 4.1. Background
    • 4.2. Method
      • 4.2.1. Individual Aggregate Fraction Packing
      • 4.2.2. Mix Volume Ratio
      • 4.2.3. Dilation Concept
      • 4.2.4. Shear Stress
      • 4.2.5. Bailey Method
      • 4.2.6. Dry Rodded Density Check
    • 4.3. Individual Aggregate Fraction Packing
      • 4.3.1. Gyratory Compaction
      • 4.3.2. Slab Compactor
      • 4.3.3. Aggregate Breakdown
      • 4.3.4. Shear Stress
    • 4.4. Review of Existing SMA Mixes
      • 4.4.1. Queensland Mix 1
      • 4.4.2. Queensland Mix 2
      • 4.4.3. South Australian Mix
      • 4.4.4. NSW Mix 1
      • 4.4.5. NSW Mix 2
      • 4.4.6. Summary
    • 4.5. Effect of Fine Aggregate on Deformation Resistance
  • 5. CONCLUSIONS
    • 5.1. Aggregate Gradation
    • 5.2. Mastic Properties
    • 5.3. Stone-on-stone Aggregate Skeleton
    • 5.4. Summary
  • REFERENCES
  • Appendix A SUPPORTING DATA FOR PARTICLE INTERMESHING EXPERIMENT
  • Appendix B AUSTRALIAN SMA GRADATIONS FOR NOMINAL SIZE MIXES
  • B.1 SMA 7 Grading
  • B.2 SMA 10 Grading
  • B.3 SMA 14 Grading