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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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19
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)
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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!