asphalt aging and fatigue - western...
TRANSCRIPT
Asphalt Aging and Fatigue
Ron Glaser Mike FarrarShin-Che HuanggJohn SchabronFred Turner
Program Review
January 27, 2011
Aging Studies
• SUBTASK 2‐2.1 IMPACT OF WATER ON AGING
• SUBTASK 2‐2.2 SUPPORT OF THE MECHANISTIC‐EMPIRICAL PAVEMENT DESIGN GUIDE Aging StudyPAVEMENT DESIGN GUIDE‐ Aging Study
• SUBTASK 2‐2.3 AUTOMATED ON‐COLUMN PRECIPITATION AND RE‐DISSOLUTION ANALYSIS
• SUBTASK 3‐2D LABORATORY AND FIELD AGING INFLUENCE ON EMBRITTLEMENT
Problem
• How does aging affect asphalt pavement durability?
• What changes in chemical composition with aging cause reductions in endurance performance?reductions in endurance performance?
• Can we adjust binder composition or pavement section design to increase service life ?
• What maintenance procedures make sense to extend service life ?
What happens when asphalt ages (oxidizes)(oxidizes)
• Asphalt ages through oxidation, changing the chemical composition
• Changes in the chemical composition change the mechanical propertiesmechanical properties
• Aged Pavements are more brittle and relieve stress much more slowly than new pavements
• Aged Pavements heal more slowly accumulate damage• Aged Pavements heal more slowly, accumulate damage more quickly
• The service life of the pavement is greatly affected by aging
Design for Aging
Aging Study
Aging Study Characterization
• FTIR‐Multi‐solvent – to obtain rate expressions
• CHNS‐DO – to investigate rates based upon oxygen uptake
DSR t bt i h l i l ti• DSR – to obtain rheological properties
• DSC – to evaluate changes in glass transition width
• LAST – to quantify fatigue resistance• LAST – to quantify fatigue resistance
• AD – speciation of asphaltenes
• SARA + IR – solvent defined fraction changes, reactants and g ,products fates
• AFT – solvation shell dimension and compatibility
• NMR – aromatization changes
Aging Study Materials
• ALF 70‐22 RTFO binder
• ManitobaManitoba• Tank, RTFO in support of warm mix studies
• Minnesota • A,B,C RTFO binder
• SHRP RTFO binders (4)
• 2 ARC RTFO binders• 2 ARC RTFO binders
Progress to date
• Aging – first set of samples recently completed
• Elemental Analysis – selected ALF samples
• FTIR – over 50% complete
AD T k 3D li i k l t ALF l• AD – Task 3D preliminary work complete on ALF samples
• SARA + IR – just started
• DSC – selected ALF samples• DSC selected ALF samples
• AFT – not started
• NMR – not started
• DSR – not started
• LAST – not started
Preliminary Results and Observations
Good correlations exist between the following metrics d f iand extent of aging:
• Sulfoxide plus carbonyl IR absorbance
• Direct oxygen from elemental Analysisyg y
• Toluene/heptane peak ratio from AD
• Glass transition width from DSC
Design for Aging
Design for Aging
• Parallel first and zero order rate expressions fit the data welldata well.
• Film diffusion model is more fundamental• Film modeling fits suggests mass transfer inside
the binder is rate limiting
Design for Aging
• Simple expressions produce activation energy values near viscous flow values
• The film diffusion model explicitly accounts for viscosity changes
• Differences in AAD and AAG reconciled with anDifferences in AAD and AAG reconciled with an internal diffusion length adjustment
• Simpler testing of this physical parameter may d d di iproduce good rate predictions
• A practical, fundamentally based spec test for aging rate may be possible (AFT)g g y p ( )
Design for Aging
Design for Aging
Design for Aging
Stress profiles due to property gradientsgradients
• Asphalt binders exhibit dramatic changes in elasticity with temperature
• Asphalt binders also exhibit dramatic changes in elasticity• Asphalt binders also exhibit dramatic changes in elasticity as they age
• Asphalt binders age more near the surface of the pavement
Property Gradients
Property Gradients
Static‐Elastic Modeling of Thermal Stresses Aging and Block CrackingStresses… Aging and Block Cracking
So What?
Products (Asphalt Research Community)Community) ….
• Multivariate Regression of Over Defined Data‐Beta release in progress (VB.NET)
• Master Curve Shift Factor Parameter Fits with extent of• Master Curve‐Shift Factor Parameter Fits with extent of aging
• Multi‐solvent method for high resolution IR studies
• Advanced Spectral Subtraction methods
• Peak series decomposition program
Products (Asphalt Paving Community)Community) ….
• Correlation of IR response to rheology
• Micro‐sampling of pavement for stiffness evaluation using IRIR
• Aging rate prediction spec test
• DSR replacement of BBR using 4mm platesDSR replacement of BBR using 4mm plates
• Improvements in the MEPDG, particularly the Global Aging System and TCModel to account for aging effects
Thanks for Your Attention...
• Questions ?
• Comments ?
Di i ?• Discussion ?
• rglaser@uwyo edu• [email protected]