advances material characterisation for pavement design · advances material characterisation for...
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Advances Material Characterisation for Pavement Design
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Australian Modulus for Design
• There is no difference between Australian and NCAT testing
• Production mixes do not vary to a great extent • Production mixes are better than currently assumed • Australia can achieve better modelling by grouping
than complex models • Risk around results can be logically assessed
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Why APS-fL
• Australia designs some of, if not, the thickest asphalt pavements in the world
• Fatigue Endurance Limit valid and accepted • Poor correlation between how and when damage
occurs and design models
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Why Material Characterisation Study
• Determine actual material properties of Australian mixes to accurately determine pavement response.
• Allow comparison of the material properties of Australian mixes against US and European mixes
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Why Dynamic Modulus Test
• Characterises material properties over a full range of loading times and temperatures
• Ability to develop “master curves” • Proven Relationship to Performance • Established researched test method internationally
used • Link to overseas performance studies
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Australian Material Database
• 28 mixes – Concentrate on nominal 20mm mixes – Concentrate on stiffer binders
• Design methods Marshal, Gyratory and Superpave
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Gradation Comparison of Australian Mixes (14mm)
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Volumetric Properties
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Dynamic Modulus Test
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Dynamic Modulus Test
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Temperature Shifting
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Temperature Shifting
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Master Curve
log (|𝐸↑∗ |) =𝛼+ 𝛽/1+ 𝑒↑(𝛾+𝛿( 𝑓↓𝑟 ))
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Temperature Shift Factors
𝑎↓𝑇 = 10↑𝑎(𝑇− 𝑇↓𝑟𝑒𝑓 )↑2 +𝑏(𝑇− 𝑇↓𝑟𝑒𝑓 )
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Australian Mix Database
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Grouping of Mixes
• Australian Mixes – Little variance in gradation – Little change in volumetric properties – Master-curve shapes are consistent
• Do we need complex models?
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• Current Models – Witczak, R2 0.9 (log) 0.8(Arithmatic) – Hirsch. R2 0.92 (log)
Accuracy of Grouping Approach
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Grouping of Mixes
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NCAT Sample Comparison
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Correlation with NCAT
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Confidence Intervals
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Use of Confidence Intervals
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Use of Confidence Intervals
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Use of Confidence Intervals
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Use of Confidence Intervals
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Conclusions and Recommendations
• Little variance in Australian Production mixes • No difference in Australian and NCAT testing
– Use NCAT to develop models
• Little change in shape of Australian master-curves or variance within binder and nominal aggregate size.
• Australia can higher degree of accuracy by use of grouping approach than published models
• Confidence intervals can be established from Australian database by using normal distribution and standard error