Lecture6_Asphalt_testing_-_superpave

Lecture6_Asphalt_testing_-_superpave - Asphalt Cements New...

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1 Asphalt Cements 1 New Superpave P erformance G raded Specification Some slides are courtesy of FHWA PG Specifications ± Fundamental properties related to pavement performance Environmental factor ± Environmental factors ± In-service & construction temperatures ± Short and long term aging 2 PG Specifications ± Based on rheological testing ± Rheology: study of flow and deformation ± Asphalt cement is a viscoelastic material ± Behavior depends on: ± Temperature ± Time of loading ± Aging (properties change with time) 3
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2 High Temperature Behavior ± High in-service temperature ± Desert climates ± Summer temperatures Viscous Liquid ± Sustained loads ± Slow moving trucks ± Intersections 4 Pavement Behavior (Warm Temperatures) ± Permanent deformation (rutting) ± Mixture is plastic ± Depends on asphalt source, additives, and aggregate properties 5 Permanent Deformation 6 Function of warm weather and traffic Courtesy of FHWA
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3 Low Temperature Behavior ± Low Temperature ± Cold climates ± Winter Elastic Solid ± Rapid Loads ± Fast moving trucks 7 σ = ε E Hooke’s Law Pavement Behavior (Low Temperatures) ± Thermal cracks ± Stress generated by contraction due to drop in temperature Crack forms when thermal stresses exceed ± Crack forms when thermal stresses exceed ability of material to relieve stress through deformation ± Material is brittle ± Depends on source of asphalt and aggregate properties 8 Thermal Cracking 9 Courtesy of FHWA
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4 Aging ± Asphalt reacts with oxygen ± “oxidative” or “age hardening” ± Short term ± Volatilization of specific components ±
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Lecture6_Asphalt_testing_-_superpave - Asphalt Cements New...

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