Mr.E.gopalkrishnan FICCI Chennai

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    Repair& DiagnosticMethods

    for RCCStructures

    E. GOPALKRISHNAN,Head-ADL Consultancy ServicesDr.Fixit Institute Structural Protection Rehabilitation

    Chennai 20120210

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    Content

    Introduction

    Servicelife&Deterioration

    CausesofRepairFailures AdvancedDiagnosticMethods

    ApplicationofNDTforDurableRepair

    Summary

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    Class Notional

    Design

    ServiceLife

    (Years)

    Example

    1 1-5 TemporaryStructures

    2 25 ReplaceableStructuralParts

    3 50 BuildingStructuresandother

    commonstructures

    4 100 MonumentalBuildingStructures,

    BridgesandotherCivil Engineering

    Structures.

    ServiceLifeRequirements

    forConcreteStructures-ISO2394&EN1990

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    Durableconcrete

    DesignDetail

    Construction

    Practice

    Materials Mix

    Proportions

    DurableConcrete

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    CauseofDeterioration

    Whether the cause is corroding rebar, poor

    resistance, high impact, abrasion,

    chemical attack or other reasons,addressing and correcting the cause of

    deterioration is the primary requirement in

    a durable repair.

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    SchematicStagesof Corrosion

    InducedDeteriorationofaConcreteStructure

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    Corrosionprocess

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    Stagesofcorrosioninduced

    InitiationPhase Conditionestablishedbymonitoring

    Propagationphase DeteriorationestablishedthroughsurveyandNDT

    11

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    CausesofRepair ailuresIt is very difficult to identify a singlecause for a particular failure, since,

    frequently. There are several reasons

    which are inter-related,Incorrectdesignoftherepair

    Useofincorrectmaterials

    PoorworkmanshipWrongdiagnosis

    Otherfactors

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    UnsatisfactoryRepairs

    Thefailureofrepairsareattributableto-

    DesignorEvaluationerrors,

    InstallationorApplicationerrors

    MaterialsPerformance

    * Source :- U.S.Army Corps of Engineers

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    ApproachtoRepair

    Investigatethecauses&identifythe

    problemsandunderstand

    UseNDTmethodstounderstanddamagesanddefects

    Considerstructuralandoperational

    requirementstoselecttherepair

    method

    SelectionofrightRepairMaterials

    withappropriatemethodology

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    NDTTechniques

    Common Advanced NDTSchmidt Rebound

    Hammer

    Corrosion Analyser

    UltrasonicPulseVelocity

    InfraredThermography

    Cover Meter Petrography

    Cores

    CarbonationDepth Pull offTest

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    SchmidtHammer

    Simplest&Quickestestimationofsurfacehardnessofconcrete

    Carbonationisnottheonlyimportantfactor

    influencingreboundnumbers

    Thestrengthestimatedfromthe

    manufacturer'sregressioncurveistobe

    multipliedbyatimefactor.

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    CorrosionAssessment

    Chlorideionandcarbonationtestinghelptoestablishwhetherpassivefilmhasbeen

    destroyed

    Iffilmnotdestroyed,whenwillitbedestroyed?

    Iffilmhasbeendestroyed,whatisstateof

    corrosion?

    Half-cellpotential

    Concreteresistivity

    Corrosionrate(polarizationresistance)

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    CorrosionRate!

    Source:-StudyconductedbyCECRI,Karaikudi(1993 2003~33fieldstns)

    Chennai2nd mostcorrosionpronecity 0.5

    mm/y

    Sriharikota1.6millimetresperyearmm/y

    Marmogoa 0.45millimetersperyearmm/y

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    CorrosionAnalyser

    Potentialmeasurement(potential mapping),

    corrosion ratemeasurement,galvano static pulsetechnique (GPM)

    Linear polarisationresistance technique(LPR) and servicelife estimate.

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    Rate of corrosion

    measured oncircumference of the

    column

    Degrees

    Half cell potentialmeasured on

    circumference of

    the column

    = - 500 mV

    At the marked point rate of corrosion was 220m.For 20 years [email protected] mm per year = 4.4 mm

    Degrees

    Height(cm)

    Height(cm)

    mailto:[email protected]:[email protected]
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    Howtolocatevoidsand

    delamination? Impact-Echo Impulse Response Method Ground Penetrating Radar Ultrasonic Measurements Infrared Thermography Petrography

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    UPVGoodforassessinguniformityand

    identifyingareasforfurtherinvestigationToidentifythehoneycombs,voids&

    cracksinsidetheconcrete

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    InfraredThermography

    Potential

    seepage

    Potential

    deboning

    plaster

    Potential

    spalling

    concrete

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    Potential

    debonding

    plastertobehackedand

    restored

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    Seepagealong

    groovelines

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    Facadein

    good

    condition,

    donot

    requirerepair

    works

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    Polarised Optical Microscope

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    ApplicationofPetrographyinRepair

    AlkaliSilicaReaction(ASR)

    ChemicalAttack

    DelayedEttringiteFormationFireDamage

    CauseofCracking

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    Microscopephoto of air

    entrained,

    homogeneous concrete

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    Thephotograph

    showsthecracked

    oxidizedpyritegrainatthesurface

    region,and

    extensionof

    crackingandreddishbrownironoxide

    andhydroxide

    oxidationproducts

    intothe

    neighboringpaste.

    Fieldwidthsofall

    photosare5mm

    Photomicrographs of thin

    sections of cores (in plane

    polarized light mode)

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    Directtensilestrength

    Evaluateconditionofconcretesurface

    beforeapplicationofoverlayorrepair

    Material

    Measurebondstrengthofoverlayor

    surfaceofrepairmaterials

    Pull-offTestASTMC1583/C1583M

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    SummaryRegularInspections/Monitoringhelps

    earlydetectionofanydeteriorationDiagnosisofdefectsandcondition

    assessmentsareessentialprerequisites

    forasuccessfulconcreterepairAdvanceNDTmethodhelpstolocate

    exactlytheplaceofseepages,leakages,

    defects,honeycombs,cracksinthestructuressothatrepairbecomesdurable

    Repair cost increases without properdiagnosis

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    ThankYouforYour

    KindAttention!