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SES_2008_presentation-Pour-Ghaz et al. 2008.pdf - Central Concrete

SES_2008_presentation-Pour-Ghaz et al. 2008.pdf - Central Concrete

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Purdue UniversitySchool of Civil EngineeringMultisc<strong>al</strong>e Modeling ofRestrained Volume Change inCement Based CompositesPrepared byM. <strong>Pour</strong>-<strong>Ghaz</strong>, R. Henkensiefken, G. Sant, J. H. MoonW. J. WeissPrepared forSoci<strong>et</strong>y of Engineering Science, 45 th Annu<strong>al</strong> Technic<strong>al</strong> Me<strong>et</strong>ingUniversity of Illinois at Urbana-ChampaignSoci<strong>et</strong>y of Engineering Science Oct 12-15, <strong>2008</strong>, Slides Developed by Jason Weiss Slide 1 of 29


OutlineShrinkageMacrosc<strong>al</strong>eShrinkageMesosc<strong>al</strong>eShrinkageMicrosc<strong>al</strong>eSoci<strong>et</strong>y of Engineering Science Oct 12-15, <strong>2008</strong>, Slides Developed by Jason Weiss Slide 2 of 29


OutlineShrinkageMacrosc<strong>al</strong>eShrinkageMesosc<strong>al</strong>eShrinkageMicrosc<strong>al</strong>eSoci<strong>et</strong>y of Engineering Science Oct 12-15, <strong>2008</strong>, Slides Developed by Jason Weiss Slide 3 of 29


Residu<strong>al</strong> Stress Developmentat the Macrosc<strong>al</strong>eC<strong>al</strong>culated Tensile Stress ( MPa )Creep/Cracking Effectdt,Initi<strong>al</strong> SpecimenShrinkage EffectRestraint Effectd t,Stress RelaxationdEdEdSHRFin<strong>al</strong> Stress StateddSHRt,E28StressRelaxation0 7 14 21 28Age of Specimen (Days)Weiss <strong>et</strong> <strong>al</strong>. 1998, JEMSoci<strong>et</strong>y of Engineering Science Oct 12-15, <strong>2008</strong>, Slides Developed by Jason Weiss Slide 4 of 2912840Stress BasedOn Hooke’s LawStrengthStress InSpecimen


Res. Stresses/ Strength (MPa)Residu<strong>al</strong> Stress Developmentat the Macrosc<strong>al</strong>eAverage Stress / Strength (~)1.203.53.02.52.0ft. saw-cutRes. Stress (No Saw-cut)Tensile StrengthRes. Stress (a/D = 0.33 at 6 Hours)1.000.800.600.40flawmax'ftaKfIf'taD1.51.00.200.50.0-0.50 4 8 12 16 20 24Time (hours)0.000.00 0.20 0.40 0.60 0.80 1.00Saw-Cut to Depth Ratio (a/D)a critic<strong>al</strong>DRaoufi and Weiss 2006Soci<strong>et</strong>y of Engineering Science Oct 12-15, <strong>2008</strong>, Slides Developed by Jason Weiss Slide 5 of 29


VoltageUsing Acoustic EmissionTo Assess Damage - Basic Terms• Hits (Event Counting) – Counts Each Event OnlyOnce By Using a Time Threshold, Typic<strong>al</strong>ly from theLast Count• Duration – Length of Sign<strong>al</strong>• Amplitude – Maximum Voltage (dB) Recorded1 EventLengthThresholdTimeWe May ‘Assume’ a Hit Refers to a Micro-CrackSoci<strong>et</strong>y of Engineering Science Oct 12-15, <strong>2008</strong>, Slides Developed by Jason Weiss Slide 6 of 29


Using Acoustic EmissionTo Assess Damage at Macrosc<strong>al</strong>e• Strain Measurementon Steel• Acoustic EmissionEnergyHossain and Weiss 2003Soci<strong>et</strong>y of Engineering Science Oct 12-15, <strong>2008</strong>, Slides Developed by Jason Weiss Slide 7 of 29


Using Acoustic EmissionTo Assess Damage at Macrosc<strong>al</strong>e• Strain Measurementon Steel• Acoustic EmissionEnergyHossain and Weiss 2003Soci<strong>et</strong>y of Engineering Science Oct 12-15, <strong>2008</strong>, Slides Developed by Jason Weiss Slide 8 of 29


Stress (MPa)Cumulative AcousticEnergy ( VS)Stages of Crack Propagation3.214Residu<strong>al</strong> Stress122.8StableMicrocrackingDamageLoc<strong>al</strong>ization102.482.0Acoustic EnergyPropagationOf Crack7 8 9 10Time (Days)Soci<strong>et</strong>y of Engineering Science Oct 12-15, <strong>2008</strong>, Slides Developed by Jason Weiss Slide 9 of 2964Hossain <strong>et</strong> <strong>al</strong>., TRB, 2003


OutlineShrinkageMacrosc<strong>al</strong>eShrinkageMesosc<strong>al</strong>eShrinkageMicrosc<strong>al</strong>eSoci<strong>et</strong>y of Engineering Science Oct 12-15, <strong>2008</strong>, Slides Developed by Jason Weiss Slide 10 of 29


Shrinkage of DifferentCement Based Materi<strong>al</strong>sMeasured Shrinkage• Shrinkage -Volum<strong>et</strong>ric ChangeAssociated With ALossLoss OfOf WaterWater• Measure LengthChange in Concr<strong>et</strong>e• Measure Length inthe Components(Paste andAggregate)• Shrinkage is aPaste PropertyAfter L’Hermite 1962Aggregate (Gener<strong>al</strong>lyPasteDrying TimeConcr<strong>et</strong>eSoci<strong>et</strong>y of Engineering Science Oct 12-15, <strong>2008</strong>, Slides Developed by Jason Weiss Slide 11 of 29


Shrinkage is a Paste PropertyStiffer Aggregate MoreEffective In Restraining(1 V )nConcr<strong>et</strong>e Paste fAgg2DPlane StressSimulationsPick<strong>et</strong>t 1955Moon <strong>et</strong> <strong>al</strong>. 2006Soci<strong>et</strong>y of Engineering Science Oct 12-15, <strong>2008</strong>, Slides Developed by Jason Weiss Slide 12 of 29


Mesosc<strong>al</strong>e Modeling of Shrinkage• Observation of the Role of Aggregates(Intern<strong>al</strong> restraint, Interlocking, <strong>et</strong>c.)• Object Oriented Finite Element An<strong>al</strong>ysisCode Developed by NIST (OOF)Specimen Obtain an actu<strong>al</strong> image OOF SimulationSoci<strong>et</strong>y of Engineering Science Oct 12-15, <strong>2008</strong>, Slides Developed by Jason Weiss Slide 13 of 29


Modeling Multi-Phasesat the Mesosc<strong>al</strong>eSoci<strong>et</strong>y of Engineering Science Oct 12-15, <strong>2008</strong>, Slides Developed by Jason Weiss Slide 14 of 29


Modeling Multi-Phasesat the Mesosc<strong>al</strong>eSoci<strong>et</strong>y of Engineering Science Oct 12-15, <strong>2008</strong>, Slides Developed by Jason Weiss Slide 15 of 29


Modeling Multi-Phasesat the Mesosc<strong>al</strong>eSoci<strong>et</strong>y of Engineering Science Oct 12-15, <strong>2008</strong>, Slides Developed by Jason Weiss Slide 16 of 29


Modeling Multi-Phasesat the Mesosc<strong>al</strong>eSoci<strong>et</strong>y of Engineering Science Oct 12-15, <strong>2008</strong>, Slides Developed by Jason Weiss Slide 17 of 29


OutlineShrinkageMacrosc<strong>al</strong>eShrinkageMesosc<strong>al</strong>eShrinkageMicrosc<strong>al</strong>eSoci<strong>et</strong>y of Engineering Science Oct 12-15, <strong>2008</strong>, Slides Developed by Jason Weiss Slide 18 of 29


A Few Main Concepts• Chemic<strong>al</strong> Shrinkage – A Measure of VolumeReduction Associated with Hydration• Autogenous Shrinkage – A Measure of theExtern<strong>al</strong> Volume Change in A Se<strong>al</strong>ed Sample• Cavitation – The Formation of Vapor FilledSpace in the Pore SpaceSoci<strong>et</strong>y of Engineering Science Oct 12-15, <strong>2008</strong>, Slides Developed by Jason Weiss Slide 19 of 29


Volume ChangeVolume ChangeVolume ChangeEarly Age Volume ChangesAge of SpecimenAge of SpecimenAge of SpecimenAir VoidsEmptySpaceAmerican Concr<strong>et</strong>e Institute April 1, <strong>2008</strong>, Slides Developed by Jason Weiss Slide 20 of 29


Volume Reduction (ml/g cem)Initi<strong>al</strong> S<strong>et</strong>Fin<strong>al</strong> S<strong>et</strong>Acoustic Emission Events(Counts)Using AE to D<strong>et</strong>ect CavitationChemic<strong>al</strong> and Autogenous Shrinkage0225-3000-6000-9000w/c = 0.30Chemic<strong>al</strong> ShrinkageAutogenous StrainAcoustic EmissionVapor Space Creation20017515012510075-120005025-150000 2 4 6 8 10 12 14 16 18 20 22 24Age of Specimen (Hours)0Couch <strong>et</strong> <strong>al</strong>. 2006Soci<strong>et</strong>y of Engineering Science Oct 12-15, <strong>2008</strong>, Slides Developed by Jason Weiss Slide 21 of 29


Conceptu<strong>al</strong> Illustration• Pore Fluidin Blue• Pore W<strong>al</strong>ls ingray• Pores ofdifferent sizesrIniti<strong>al</strong>ly FilledSoci<strong>et</strong>y of Engineering Science Oct 12-15, <strong>2008</strong>, Slides Developed by Jason Weiss Slide 22 of 29


Background on One ShrinkageMechanism - Capillary Tension• A liquid-vapor interfaceresults in a meniscus• The meniscus exerts astress on the pore w<strong>al</strong>ls• This stress isresponsible for thevolume change c<strong>al</strong>led“shrinkage”• The Young-Laplaceequation can be used tocompute the stressSe<strong>al</strong>ed 2- Plain cos( )Cap. .rSoci<strong>et</strong>y of Engineering Science Oct 12-15, <strong>2008</strong>, Slides Developed by Jason Weiss Slide 23 of 29


Surface Tension (N/m)Shrinkage Mitigation Strategies• SRAs - <strong>al</strong>ter the surface tension of the pore fluid• SLWA - supply addition<strong>al</strong> water during hydration0.080.07Pure De-Ionized Water0.06De-Ionized WaterSynth<strong>et</strong>ic Pore Solution0.05Cap. .2cos(rSe<strong>al</strong>ed - Plain)0.04Se<strong>al</strong>ed - SRA0.030 3 6 9 12 15SRA Concentration (%)Soci<strong>et</strong>y of Engineering Science Oct 12-15, <strong>2008</strong>, Slides Developed by Jason Weiss Slide 24 of 29


Shrinkage Strain ( )Drying Response of Pastes0-1000w/c = 0.30w/c = 0.30+5%SRA-2000-3000-4000-500020 40 60 80 100Relative Humidity (%)Soci<strong>et</strong>y of Engineering Science Oct 12-15, <strong>2008</strong>, Slides Developed by Jason Weiss Slide 25 of 29


Relative Humidity (%)Intern<strong>al</strong> RH and Stress MitigationKelvin’s equation:Young-Laplace’sequation:capCap. .RT ln( RH )2Vmcos(r)1009896949290888684828033.0%k29.3%k25.3%k18.3%k14.3%k11.0%k7.3%k0.0%0 1 2 3 4 5 6 7Age of Specimen (Days)Henkensiefken <strong>et</strong> <strong>al</strong>. <strong>2008</strong>Soci<strong>et</strong>y of Engineering Science Oct 12-15, <strong>2008</strong>, Slides Developed by Jason Weiss Slide 26 of 29


Strain ( )Shrinkage Cracking100-10-20-30-40-50-600 2 4 6 8 10 12 14 16 18 20Age of Specimen (Days)25.3%k14.3%k11.0%k7.3%k3.8%k0.0%Henkensiefken <strong>et</strong> <strong>al</strong>. <strong>2008</strong>Soci<strong>et</strong>y of Engineering Science Oct 12-15, <strong>2008</strong>, Slides Developed by Jason Weiss Slide 27 of 29


Summary• Shrinkage on the Macrosc<strong>al</strong>e– Models are developed; however they do notconsider specific mechanisms• Shrinkage on the Mesosc<strong>al</strong>e– Separate into shrinkage into paste andaggregate, however more work is needed tounderstand time dependence• Shrinkage on the Microsc<strong>al</strong>e– Pore space, pore size, and surface tension canbe used to describe shrinkage – lead to newstrategiesSoci<strong>et</strong>y of Engineering Science Oct 12-15, <strong>2008</strong>, Slides Developed by Jason Weiss Slide 28 of 29


Thanks,M. <strong>Pour</strong>-<strong>Ghaz</strong>, R. Henkensiefken, G. Sant, J. H. Moonand W. J. WeissSoci<strong>et</strong>y of Engineering Science Oct 12-15, <strong>2008</strong>, Slides Developed by Jason Weiss Slide 29 of 29

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