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GuidelinesforResolutionofNon-ConformancesinPrecastConcreteBridgeElements
ReportNo:PCINE-18-RNPCBE
FirstEdition
Report No: PCINE-18-RNPCBE Title: Guidelines for Resolution of Non-Conformances in Precast Concrete Bridge Elements Developing Organization: Precast/Prestressed Concrete Institute Northeast Bridge Technical Committee Phone – 888-700-5670 Email – [email protected] Report Date: 1-16-18 Revision Dates: Status of Report: Final Abstract: These guidelines provide recommendations for the evaluation and repair of non-conformances in precast and prestressed concrete bridge products. The document can serve as a resource for owners, designers, state inspectors, plant production managers, plant quality control Inspectors and plant engineers in reaching informed decisions in addressing non-conformances and repairs. Number of Pages: 89 PCI and PCI Northeast cannot accept responsibility for any errors or oversights in the use of this material. The user must recognize that no guidelines or regulations can substitute for experienced judgment. This guideline is intended for use by personnel competent to evaluate the significance and limitations of its contents and able to accept responsibility for the application of the material it contains.
Guidelines for Resolution of Non-
Conformances in Precast Concrete Bridge Elements
Report Number PCINE-18-RNPCBE
GuidelinesforResolutionofNon-ConformancesinPrecastConcreteBridgeElements
ReportNo:PCINE-18-RNPCBE
Copyright©2018
ByPrecast/PrestressedConcreteInstituteNortheastFirstEdition
ThisdocumentsupersedesthedocumenttitledPCINER-01-BMRG–BridgeMemberRepairGuidelinesdatedOctober2001
Allrightsreserved.Thisguideoranypartthereofmaynotbereproducedinanyform
withoutthewrittenpermissionofthePrecast/PrestressedConcreteInstituteNortheast.
PrintedintheU.S.A
These guidelines should not be considered a standard. Information contained in thisworkhasbeenobtainedfromsourcesbelievedtobereliable.PCIandPCINortheastoritsmembershipsshallnotberesponsibleforanyerrors,omissions,ordamagesarisingoutof this information.PCINortheasthaspublishedthisworkwiththeunderstandingthat PCI Northeast is supplying information only. PCI Northeast is not renderingengineeringorotherprofessionalservicesthroughtheseguidelines.Ifsuchservicesarerequired,pleaseseekanappropriateprofessional.
ContentsForeword........................................................................................................................................1
Section1:Introduction...................................................................................................................2
Howtousethismanual..............................................................................................................2
FinishingofPrecastElements.....................................................................................................3
GradeAFinish.........................................................................................................................3
GradeBFinish(highlyvisible).................................................................................................4
StandardGradeFinish(exposedtoview)...............................................................................4
CommercialGrade(notexposedtoview)..............................................................................4
UnformedSurfaceFinishes.....................................................................................................4
ExposedAggregateFinishesforElementConnections...........................................................5
SpecifyingSurfaceFinishes.....................................................................................................5
SurfaceRepairs.......................................................................................................................5
RepairDecisionProcess..............................................................................................................5
RecommendedDecisionProcessFlowchartKeyFactorsinDecisionsRegardingNoRepair,Repair,orRejection................................................................................................................6
GeneralCommentsonCracking.............................................................................................7
SpallsandVoids......................................................................................................................8
DurabilityofRepairs...............................................................................................................9
EssentialIssuestoBeConsideredInEngineeringEvaluation.................................................9
RepairableNon-conformances.............................................................................................11
Non-RepairableNon-conformances.....................................................................................11
Section2:TroubleshootingGuide................................................................................................12
Section2.1:PrestressedElements............................................................................................12
TS#1:TROUBLESHOOTINGFORTRANSVERSECRACKSORIGINATINGATTOPSOFBEAMS 14
TS#2:TROUBLESHOOTINGVERTICALANDDIAGONALCRACKSATBOTTOMOFBEAMS...17
TS#3:TROUBLESHOOTINGVERTICALTHROUGHCRACKSINBEAMS..................................20
TS#4:TROUBLESHOOTINGHORIZONTALENDCRACKSINWEBSANDFLANGES................22
TS#5:TROUBLESHOOTINGBOTTOMFLANGECRACKSATBEAMENDS..............................24
TS#6:TROUBLESHOOTINGCORNERSPALLSORCORNERCRACKS......................................25
TS#7:TROUBLESHOOTINGPARTIALLYCRACKEDTOPFLANGES.........................................28
TS#8:TROUBLESHOOTINGRANDOMHONEYCOMBINGANDVOIDS..................................30
TS#9TROUBLESHOOTINGRANDOMTOPFLANGECRACKS................................................32
TS#10TROUBLESHOOTINGSHORTPROJECTEDSTRANDORREINFORCING,MISSINGPROJECTEDSTRANDORREINFORCING.................................................................................34
TS#10TROUBLESHOOTINGSHORTPROJECTEDSTRANDORREINFORCING,MISSINGPROJECTEDSTRANDORREINFORCING.................................................................................35
TS#11TROUBLESHOOTINGCRACKSANDHONEYCOMBINGINPRECAST,PARTIALDEPTH 36
DECKPANELS........................................................................................................................36
TS#12TROUBLESHOOTINGPARTIALLYCRACKEDTOPFLANGES–NEXTBEAMS................38
Section2.2:Non-PrestressedPrecastElements...........................................................................41
TS#SS1:TROUBLESHOOTINGCORNERSPALLSINNON-PRESTRESSEDPRECAST...............42
ELEMENTS.............................................................................................................................42
TS#SS2:TROUBLESHOOTINGFORCRACKSINNON-PRESTRESSEDPRECASTELEMENTS...44
TS#SS3:TROUBLESHOOTINGFORHONEYCOMBING,VOIDS,POURLINES,ANDMINOR..46
SURFACEIMPERFECTIONSINNON-PRESTRESSEDPRECASTELEMENTS...............................46
TS#SS4:TROUBLESHOOTINGSHORTPROJECTEDREBARANDMISSINGPROJECTED........48
REBARINNON-PRESTRESSEDPRECASTELEMENTS..............................................................48
TS#SS5:TROUBLESHOOTINGMISSINGORMIS-LOCATEDINSERTS,VOIDS,ORMIS-LOCATEDPROJECTINGREBARINNON-PRESTRESSEDPRECASTELEMENTS.........................50
Section2.3:PrecastFullDepthDeckPanels.............................................................................52
TS#FDDP1:TROUBLESHOOTINGCORNERSPALLSINPRECASTFULL-DEPTHDECKPANELS53
TS#FDDP2:TROUBLESHOOTINGFORCRACKSINFULL-DEPTHPRECASTDECKPANELS.....55
TS#FDDP3:TROUBLESHOOTINGFORTRANSVERSECRACKSINPRESTRESSEDFULL-.........57
DEPTHDECKPANELS.............................................................................................................57
TS#FDDP3:TROUBLESHOOTINGFORTRANSVERSECRACKSINPRESTRESSEDFULL-.........58
DEPTHDECKPANELS.............................................................................................................58
TS#FDDP4:TROUBLESHOOTINGFORHONEYCOMBING,VOIDS,ANDMINORSURFACE...59
IMPERFECTIONSINPRECASTFULL-DEPTHDECKPANELS.....................................................59
TS#FDDP4:TROUBLESHOOTINGFORHONEYCOMBING,VOIDS,ANDMINORSURFACE...60
IMPERFECTIONSINPRECASTFULL-DEPTHDECKPANELS.....................................................60
TS#FDDP5: TROUBLESHOOTINGSHORTPROJECTEDREINFORCINGANDMISSING.......61
PROJECTEDREINFORCINGINPRECASTFULL-DEPTHDECKPANELS.....................................61
TS#FDDP6: TROUBLESHOOTINGMISSINGORMISLOCATEDINSERTS,VOIDS,DUCTSORMISLOCATEDPROJECTINGREINFORCINGINPRECASTFULL-DEPTHDECKPANELS..............64
Section3:StandardRepairProcedures........................................................................................66
STANDARDREPAIRPROCEDURE#1FORCONFINEDSPALLSINSIDEBEARINGAREAS..............67
STANDARDREPAIRPROCEDURE#2FORCONFINEDSPALLLSOUTSIDEBEARINGAREAS.........68
STANDARDREPAIRPROCEDURE#3FORNON-CONFINEDBEARINGAREASPALLS..................69
STANDARDREPAIRPROCEDURE#4FORSPALLSANDVOIDSINTHEBOTTOMFLANGETHATEXPOSEPRESTRESSINGSTRAND...............................................................................................70
STANDARDREPAIRPROCEDURE#5FORHONEYCOMBEDORVOIDEDWEBAREAS................72
STANDARDREPAIRPROCEDURE#6FORDAMAGEDFLANGESREQUIRINGREMOVALANDREPLACEMENTOFCONCRETE..................................................................................................73
STANDARDREPAIRPROCEDURE#7FORTAKINGCORESANDPATCHINGCOREDHOLESINGIRDERS....................................................................................................................................74
STANDARDREPAIRPROCEDURE#8FORMISSHAPENBEARINGRECESSES..............................75
STANDARDREPAIRPROCEDURE#9FORHONEYCOMBEDAREASLEFT-IN-PLACE....................76
STANDARDREPAIRPROCEDURE#10FOREPOXYINJECTIONOFCRACKS................................77
STANDARDREPAIRPROCEDURE#11FORSHORTPROJECTINGMILDREINFORCINGBARSORPROJECTINGPRESTRESSINGSTRANDS.....................................................................................79
STANDARDREPAIRPROCEDURE#12FORREPLACEMENTOFMISSINGPROJECTEDMILDSTEELORPRESTRESSINGSTRAND.......................................................................................................80
STANDARDREPAIRPROCEDURE#13FORMISSINGORINCORRECTLYLOCATEDDIAPHRAGMINSERTS.....................................................................................................................................81
STANDARDREPAIRPROCEDURE#14FORSEALINGCRACKS....................................................82
STANDARDREPAIRPROCEDURE#15FOREDGESPALLSINPRECASTELEMENTS.....................84
Section4:References...................................................................................................................86
1
Foreword These guidelines have been prepared by the Precast Prestressed Concrete Institute Northeast Bridge Technical Committee and contain recommendations for resolution of non-conformances in precast concrete bridge elements occurring during production, handling, transportation and erection. These guidelines are a resource document for owners, designers, state inspectors, plant production managers, plant quality control inspectors and plant engineers in reaching informed decisions regarding non-conformances and repairs. The PCI Northeast would like to acknowledge the members of the Bridge Technical Committee that contributed to the development of these guidelines. RitaSeraderian PCINortheastExecutiveDirector(PCINE);Belmont,MAMichaelP.Culmo CMEAssociates,Inc.,EastHartford,CTEricCalderwood CalderwoodEngineering,Richmond,MEEdBarwicki LinAssociates;Boston,MADarrenConboy JacobsEngineering,Boston,MAJohnByatt CLDEngineers,Manchester,NHScottHarrigan FortMillerGroup,Schuylerville,NYBryanReed ConnecticutDOT,Newington,CTBenCota GCPAppliedTechnologies;Cambridge,MAPaulMoyer GillEngineering;Needham,MAJoeCarrara J.P.Carrara&Sons,Middlebury,VTBrianReeves MaineDOT;Augusta,MERichardMeyers MaineDOT;Augusta,MEMauraSullivan MassachusettsDOT,Boston,MAAlexBardow MassachusettsDOT,Boston,MAEdmundNewton MassachusettsDOT(retired),Boston,MAMichaelMerlis MassachusettsDOT,Boston,MAJasonTremblay NewHampshireDOT,Concord,NHDavidScott NewHampshireDOT,Concord,NHDuaneCarpenter NewYorkStateDOT,Albany,NYMichaelTwiss NewYorkStateDOT,Albany,NYTroyJenkins NortheastPrestressedProducts,LLC,Cressona,PAChrisFowler OldcastlePrecast,Rehoboth,MAMikeSavella RhodeIslandDOT,Providence,RITerrySeymour UnistressCorp.,Pittsfield,MARobYoung VermontAgencyofTransportation,Montpelier,VT
2
Section1:IntroductionPlant-cast prestressed concrete bridge beams and similar products produced in PCI-Certifiedplantsaremanufacturedinaquality-controlledenvironment.Thesefacilitiesmeettheminimumstandards for processes and equipment. They have trained supervisory and certified qualitycontrol staff operating within published procedures that consistently result in high qualityproductsthatmeetprojectandcustomerrequirements.
As with anymanufacturing process, damage or defects can occur in precast concrete bridgeproducts. Examples include surface voids, spalls, cracks in concrete, and improperlyplacedordamagedreinforcementandhardware.Thesefallintooneofthreecategories:
• Productsthatcanbeacceptedwithoutrepair• Productsthatcanbeacceptedwithrepair• Productsthatmustberejected
Thismanualhasbeenpreparedtobearesourcedocumenttoprovideaguidelineforowners,designers, inspectors, and fabricators in reaching informeddecisions regarding repairoptions.To this end, the engineering considerations related to individual defects are provided. Theultimatevalueofthisguidedependsonthesoundengineeringjudgmentofqualifiedindividualswhousethisdocument.
HowtousethismanualThis document is a guideline document that contains recommendations for evaluation andrepair of non-conformances. Owners should consider modifying specification language toincorporatetheserecommendationsintocontractdocuments.
The management of non-conformances is a collaborative process between the Owner (orDesigner) and the Contractor (or Fabricator). At the beginning of a fabrication process, afabrication pre-productionmeeting with all parties involved is recommended. Thismeetingshould establish the process formanaging non-conformances and the responsibilities of eachparty.Thefollowinginformationshouldbediscussedatthepre-productionmeetingregardingthemanagementofnon-conformances:
• Surfacefinishrequirementso Descriptionofacceptablesurfacefeatureso Establishmentofstandardfinishingprocedures
• Repairprocedureso ReviewofPCIRepairManualo Establishacceptablerepairmaterialso Establishpre-approvedownerrepairprocedureso Establishpre-approvedfabricatorrepairprocedures
• DefineresponsibilitiesandNCRprocesso ReviewtheRepairDecisionProcess(flowchart)containedherein
Thereareother itemsthatshouldbediscussedsuchascuringmethods,handlingandstorage,etc.
3
Thesectionsofthismanualareorganizedasdescribedbelow:
Section1: Introduction: Containsgeneral informationon standard finishingprocedures,non-conformancesandmethodsformanagementofnon-conformances. Thissectionalsocontainssignificant informationon the repairprocessand thekey factors that shouldbeconsidered intherepairdecisionprocess.
Section 2 - Troubleshooting Guide: Contains descriptions, by category, of the defect beingconsidered,withcommentaryinside-by-sidecolumns:
• Causes-alistingofpossiblecausesofspecifictypesofdefects• Prevention-correspondingcorrectiveactionstoaidinpreventingeachtypeofdefect• EngineeringEffects -adiscussionof theengineering implicationof thespecific typeof
defecttoprovidethebasisfordecisionsregardingtheoptionofrepairorrejection• Repair Considerations - suggested repair options based upon the Engineering Effects
discussion,withcross-referencestoStandardRepairProcedures(Section3).
Section3-StandardRepairProcedures:Containsspecificinstructionstoimplementrepairsforthevarioustypesofdefectsidentified.
Section 4 - Selected References: Lists sources for additional information on fabrication,materials,andrepairsofprecastandprestressedconcreteproducts.
FinishingofPrecastElementsFinishing refers to the process of stripping the element from the forms, cutting of strandextensions, repair of exposed reinforcing coatings, and providing a uniform appearance tosurfacesthataretobeexposedinthecompletedstructure.Therepairproceduresoutlinedinthis document are not applicable to the finishing process. The minor surface imperfectionsdescribed below are not considered defects and are part of the normal casting and finishingprocess.Itemssuchassmallsurfacevoidsasdescribedinthefinishgradesbelowarearesultofthe process of placing and consolidating high strength, low slump concrete that is commonlyusedinmodernprecastplants.Theuseofself-consolidatingconcretecanbeusedtoreducethenumberofsurfacevoids;however,finishingwillstillberequired.
Standardfinishingprocessescanbedevelopedandagreedtoviathefabricationplant’sQualitySystemManual(QSM).ThefabricatorwillworkwiththeOwner’srepresentativetoidentifyanddocument the standard finishing process to be performed for typical minor surfaceimperfections without the necessity of filing, reviewing, and approving a Non-ConformanceReport(NCR).
Thefollowingfinishdescriptions,takenfromAppendixCofPCIMNL116,maybeusedtodefinespecification requirements. Theminimum finish grade consistentwith a product’s applicationandtheintendeduseofthestructureshouldbespecified.
GradeAFinishGradeAFinish is foruse inspecialarchitecturalapplicationsandnotrecommendedforbridgeproducts.
4
GradeBFinish(highlyvisible)Allairholesover1/4inchinsizeshouldbefilled.Airholesbetween1/8and1/4inchinwidththatoccur in high concentration (more than one per 2 square inches) should be filled. Surfaceblemishesduetoholesordentsinformsshouldberepaired.Discolorationshouldbepermittedatformjoints.
Thisfinishisrecommendedforvisuallyexposedstructuralmemberssuchasfasciabeams.
StandardGradeFinish(exposedtoview)Small surfaceholes causedbyairbubbles (“bug-holes”),normal color variations,normal formjointmarks,andminorchipsandspallsshouldbeconsideredacceptable.
No air holes (bug holes) larger than ½ inch in any direction should be permitted. Air holesbetween¼and3/8inchinwidththatoccurinhighconcentration(morethanoneper2squareinches)shouldbefilled.Large,unsightlysurfaceblemishesorhoneycombingshouldberepaired.Themaximumallowableformjointoffsetshouldbelimitedto1/8inch.Thisfinishmaybeusedwhereproductsareexposedtoviewbutthefunctionofthestructuredoesnotrequireaspecialfinish.Thesurfaceshouldbesuitableforanappliedtexturedcoatingbutnotnecessarilysuitableforpainting.
Thisistherecommendedfinishgradeforallstructuralproductsthatarevisibleinthecompletedstructure.
CommercialGrade(notexposedtoview)Thisisessentiallyan“ascast”finish.Concretemaybeproducedinformsthatimpartatextureto the concrete, (e.g., plywood lumber or steel formswith offset joints, dents or holes). Thesurfacemaycontainairholes(bugholes)andwatermarks,andtheremaybesomeminorchipsand spalls. Theremaybe some scaling and/or scouring. Theremaybepatches and streaksofcolorvariationwithinthesurface,andtheoverallcolortonemayvarybetweenpieces.
Large fins from joint bleeding should be removed, but small fins may remain. Only“honeycombed”and/orbadlyspalledareasshouldberepairedorfinished.Allfacesshouldhavetrue,well-definedsurfaces.Themaximumallowable form jointoffsetshouldbe limitedto3/16in.
This finish is recommended for surfaces of products that are not visible in the completedstructure,orwhenthefunctionofthestructuredoesnotrequireanenhancedsurface.
UnformedSurfaceFinishesThesetypesoffinishesareobtainedbyscreedingandfloatingwithadditionalhandfinishingatprojections. Normal color variations, minor indentations, minor chips, and spalls should bepermitted. No major imperfections, honeycombing, or defects should be permitted. Whereuniformityorotherspecial characteristicsofexposed,unformedsurface finishesare required,specificationsshouldbeclearontheexpectedresults.TheManualforQualityControlforPlantsandProductionofStructuralPrecastConcreteProducts,FourthEdition,MNL-116canbeusedforguidanceonsurfacefinishes.
5
ExposedAggregateFinishesforElementConnectionsExposedaggregatefinishesarerecommendedforthesurfacesoftheelementsthatarewithinthe connections in closure joints to improve the bond of grouts and concretes used in theconnections.Anexposedaggregatefinishcanbecreatedinseveralways:
1. A gelatinous retarder can be applied to the formwork in locationswhere the finish isdesired.Thehydrationreactionofthefreshconcretecontactingtheretarderisdelayed.Afterformremoval,theun-hydratedpastecanbewashedwithwater(ifepoxybarsarepresentinthejoint).
2. Sandblastingorhighpressurewaterblastingcanbeapplied to the formedsurface toexposetheaggregate;however,coatedbarswillneedtobeprotected.
The final finish of an exposed aggregate surface is different than the finish of the top of acomposite beam where a certain amplitude is often specified based on design specificationprovisions. Where joints aredetailedwithmechanical shear keys, a specific amplitude is notrequired.Thegoalofexposedaggregatefinishistoexposethestoneandremoveanysurfacelaitance.
SpecifyingSurfaceFinishesThe designer should identify the required surface finishes for all elements based on therecommendationscontained inthisdocument. Plansshould includeascheduleofallelementsurfaces along with the required surface finish. If the plans do not specify finishes, therecommendationscontainedhereinshouldbefollowed.
SurfaceRepairsAny surface variation that exceeds the limits stated above should be considered a non-conformanceandshouldbetreatedasdescribedinSection2.
RepairDecisionProcessTheevaluationofprecastelementsshouldfollowaprescribedprocesswherepotentialnon-conformancesaresystematicallyreviewedbythefabricator’sstaffandowner’srepresentative(inspector).Thefollowingflowchartisarecommendedprocessthatcanbeusedtoefficientlymanagethedispositionofnon-conformancesandrepairs.Thegoaloftroubleshootingshouldbetoresolvethenon-conformanceasclosetotheshopflooraspossible.ManyitemsmayberesolvedbetweentheshopQCManager,plantengineer,andtheOwner’sinspector.Thisdocumentalsogivesguidanceonwhenanon-conformancerequiresinputfromtheEngineer.
6
RecommendedDecisionProcessFlowchart
Legend
NCR=Non-ConformanceReport
Non-ConformanceNotedintheShopbyQCStafforOwner's
Representative
Non-ConformanceReviewedbyShopQCManagerStaff
ReviewTroubleshootingGuidelineand/orPre-approvedRepairProceduresforApplicability
IsdamageapplicabletoaTroubleshooting
Guideline?
IssueNCR(ownerorfabricator).SubmitProposedRepairProcedure toOwnerfor
approval.
No
Yes
ReviewTroubleshootingGuideline
DetermineMostProbableCause
DetermineMethodofPrevention
ReviewEngineeringEffects
ReviewPotentialRepairMethods
ReviewwithOwner'sRep.
IstheNon-Conformanceminor,
notrequiringdesignerinput?
Yes
FollowRepairProcedureOutlinedinTroubleshootingGuidelineorFabricator'sPre-
approvedRepairProcedure
No
ReviewandapproveRepairprocedureifacceptable
FabricatorStaff
Owner
Fabricator&Owner'sRep.
ActionItemProcessStep
Decision
IssueNCR(ownerorfabricator).SubmitProposedRepair Procedure toOwnerfor
approval.
ReviewandapproveRepairprocedureifacceptable
CantheNon-Conformancebeaddressedwithfinishing orowner
specified standardrepairprocedures?
No
YesFollow FinishingProceduresorOwnerSpecified
StandardRepairProcedures
7
KeyFactorsinDecisionsRegardingNoRepair,Repair,orRejectionEveryefforthasbeenmade toprovidea listof the common typesofdamageordefects thatmay occur in precast and prestressed concrete products during production, handling,transportation,anderection(pre-servicedamage).Othertypesofdefectsordamagemayoccur,however.Theremayalsobeothercauses for the typesofoccurrences listed in thisguideline,othermethodsforprevention,andotherissuestobeconsideredintheengineeringevaluationof thedamage.Engineering judgment shouldbeexercised in thesesituations. Inaddition, theapproachesillustratedinthisguidelinecanbeappliedtoothersimilarsituationsthatmayarise.
Decisions regarding the need for repair or rejection should be established by the owner andincludedinthecontractdocuments. Thereisasignificantcost impactforthefabricator. Ifallbiddersunderstandthatcertaindefectswillnotrequirerepair,orthatstandardrepairsmaybeapplied without the need for excessive review and documentation, the Owner could benefitwith lower bids. The converse, of course, is also true. Defining repair requirements alsobenefitstheOwnerbyreducingthenumberoftime-consumingnon-conformancesthatmustbeevaluated.
Proper design, detailing, and fabrication techniques are essential for the production of high-qualityprecastandprestressedconcreteproducts.Someofthemanyproceduresandprocessesincludeconcretemixdesign,mixingandconsolidationofconcrete,curingofconcrete,methodsandmaterialsfordebondingstrands,placementofdebondedstrands,methodsandsequencesofdetensioningofstrands(includingspecialconsiderationsforharpedordrapedstrands),anddetailing of anchorage zone reinforcement. Discussion of the important aspects for each ofthese issues that contribute to defects or damage to elements is beyond the scope of thisdocument. Additional information on these topics may be found in the PCI Quality ControlManual[1]andthePCIBridgeDesignManual(Section3,Fabrication)[2].
GeneralCommentsonCrackingWhen cracks occur, their cause, effect, and possible consequences must be determined. Astructuralevaluationmayberequireddependingonthenatureandlocationofthecrack.Therepairguidelinescontainedhereinincluderecommendationsforwhenastructuralevaluationiswarranted.
Cracks may occur in sections of prestressed concrete girders where the effects of theprestressingforcedonotdirectlyacttoclosesuchcracks.Itshouldbeunderstoodthatgirdersareprestressed intheir long,axialdirection.Therefore, ingeneral,anycracksthatforminthegirderthatareroughlyparalleltothelongaxisofthememberwillnotcloseundertheeffectofprestressing. An example of such cracking is the horizontal and/or diagonal splitting thatsometimesoccursattheendsofmembers(seeSection2,TS#4).
Cracksperpendiculartothelongaxisofthemembercanoccurpriortotransferoftheprestressforce when the concrete is not yet prestressed. At this time, the strands and forms providerestrainttodimensionalchangesintheconcreteduetoshrinkageandthermalcontraction(seeSection2,TS#3).However,whenthestrandsaredetensioned,thesecracksgenerallycloseduetotheprestressforce.
8
Ifthecracksclosewhenthestrandsaredetensioned,orwhenrestraintsorotherconditionsthatcaused the cracks are resolved prior to de-tensioning, the consequences of the cracking aregenerally minor or nonexistent. The phenomenon of autogenous healing can result in theconcrete "healing" through the crack, reestablishing the tensile capacity of the concrete andrestoringittoitsun-crackedcondition.Ifallowedtoclosewithouttangentialdisplacement,finecracks in fractured concrete, in the rangeof 0.004 in. to0.008 in.wide,will close completelyundermoist conditions.This isespecially true in thepresenceof compressivepressureacrossthe crack. Crackswith a 0.004 in.width can heal over a period of several days,while cracks0.008in.inwidthcanhealoveraperiodofseveralweeks.Thisautogenoushealingisduetothehydrationofpreviouslyun-hydratedcement.Ithasbeenshownthatcrackshealedautogenouslywillperformstructurallyandlong-termlikeun-crackedconcrete.
If the cracks remain open after detensioning, or if they open after detensioning, severalscenariosmustbeconsidered:
• Willthecrackclosewhensubjectedtosubsequentloadsonthestructuresuchasbytheadditionofabridgedeck?
• Willthecrackbeprotectedbyacompositedeck,orotherencasement,fromwaterandsaltthatmaybeplacedonthedeck?
• Isthecracklocatedwithinthetransferlengthofthestrand,inwhichcasethestressinthestrandmaybereducedbythepresenceofthecrack?
• Is thecrack largeenough topermitentryofmoistureandoxygen that couldpromotecorrosionofthestrandsorotherreinforcement?
SpallsandVoidsVoidsor honeycombsmayoccur in the castingof precast andprestressed concreteproducts,especiallybeams,dueto inadequateconsolidationoftheconcrete.Goodconsolidationresultsfrom a good concretemix design, propermixing and placing of concrete, appropriate coarseaggregatesize,aswellasasectionthatisnotoverlycongestedbyprestressingstrandandmildreinforcing steel. Every effort should be taken to detect voids prior to detensioning so thatrepairs,ifpermitted,canbemade,thencuredandpre-compressedwiththeadjacentconcrete.Thisactionensuresthedesignperformanceofthebeamandenhancesthelong-termdurabilityof the repair. Furthermore, the repair of large voids can prevent subsequent damage to thebeamfromdetrimentalredistributionofstressescausedbycross-sectionalvariationsduringthedetensioningprocess.
Promptinspectionofbeamspriortodetensioningisveryimportantbecausedelayintransferoftheprestresscanleadtodamagefromcracking.Crackscanoccurwhenbeamscoolwhiletheyareanchoredtoabutmentsbytheprestressingstrands.Wheninspectiondetectsvoidsorsignsof potential internal voids, measures should be taken during repair investigations to controlconcretecontractionorshorteningoftheexternalprestressingstrandduetocooling.Methodsforinvestigatingthepresenceorextentofinternalvoidsincludesoundingwithhammers,usingpulse-echoequipment,andprobingwithwireorbydrillingexploratoryholes.
9
DurabilityofRepairsThegoalofallrepairsistoprovideanelementthathasequivalentdurabilitywhencomparedtothe adjacent element concrete. The repair procedures contained herein, when constructedcorrectly, haveproven tomeet this goal. Thepresenceofa repair shouldnotbe cause for areductionintheelement’sservicelife.Thematerialsusedforrepairsshouldbeofhighquality.Important parameters for patching materials include low permeability, high bond strength,resistancetofreezethaw,andstrengththatisequaltoorsomewhatgreaterthantheelement.Recentstudieshavebeencompletedoncommonpatchingmaterialsthatincludedteststoverifytheseparameters [5]. This studycanbeused for the selectionofproperpatchingmaterials.Some ownersmaintain approved product lists, and some fabricators alsomaintain approvedproductlists.Ifpreviousapprovedbytheowner,thesematerialscanbeusedfortherepairs.
Voidsdiscoveredfollowingdetensioningorspallscausedbyhandling,transport,anderectionofbeams are, in almost all situations, repairable. The methods and materials used for repair,however, must be carefully considered to ensure the durability of the finished product inservice. The strain compatibility of the repair material with adjacent concrete must beconsidered from the time of repair through full service loading. The owner/engineer mustevaluatethedurability,aswellaslongevity,oftherepairfromthestandpointofpotentialfuturerepairs to a beam incorporated into the completed bridge and must consider methods topreventpatcheslocatedovertrafficfrombecomingdislodged.
Inmanyinstances,therepairofaspallissimplycosmetic(ratherthanrestorationofstrengthorprotection against corrosion of the prestressing or mild steel reinforcement). Considerationshouldbegiventonotrequiringrepairofaspallwhentherepairwillnotenhancestrengthordurabilityandislocatedinanareathatwillbeencasedbyaconcretepour,orwillnotbereadilyexposedtoview.
EssentialIssuestoBeConsideredInEngineeringEvaluationConditionofcracksunderfullserviceload:
1. Ingeneral,thepreferredconditionisthatatservice-levelstresses,precast,prestressedconcretebeamswillnothaveopencracks.This isespeciallytrueforbottomflangesofbeamsinpositivemomentregions.Therefore,anappropriateevaluationofanycrackinthebottomofthebeamwouldconsider,atservicelevel,thatstressesinthevicinityofacrackdonotexceed6√f’canywherealongthelengthofthecrack.
2. Transversecracksoriginatinginthetopofbeamsthatcloseupondetensioningoruponplacementof a composite slab shouldnotbeof concern.Open cracks in a top flangethatservesastheridingsurfacethatareobservedafterdetensioninganduponstorageontemporarysupportsattheirintendedbearinglocationsshouldbeevaluated.
3. Criteriaregardingcracksize,asitrelatestoenvironmentalconditions,arefoundinACICommittee Report ACI 224, "Control of Cracking in Concrete Structures." For beamsused in continuous span applications, negative bending capacity is based on crackedsectionanalysis,bothatserviceandstrengthlevels.Therefore,acrackthroughtheslaband portions of the beam depth are expected. At service level, the crack in the topflangecanbeexpectedtobeintherangeof0.008in.to0.01inches
10
The AASHTO LRFD Bridge Design Specifications contains provisions for control ofcracking[6].Theseprovisionsarebasedonanassumedcrackwidthof0.017inchesforelementsexposedtonormalconditionsand0.013inchesforelementsexposedtomoresevere conditions such as bridge decks. These criteria should be considered whendecidingwhethercracksneedtoberepaired.
AllowableStressesandStrength:
1. Allowable stresses in the repair and concrete bonded to the repair should not beexceeded at service loads. Allowable stresses in the repair material should becompatible or exceed the design stresses computed for the concrete in the originalbeam fabrication. Preloading themember prior tomaking repairs of a void detectedafter detensioning may be necessary if deemed essential to reducing undesirablestressesintherepair.
2. Allowable stressesat strand release shouldnotbeexceeded, considering the reducedsectioncausedbyavoid.
3. Flexuralandshearstrengthmustbeadequatenearbeamends,consideringthelackoffullydevelopedprestressingstrandswhencrackscrossstrandsorvoidsexposestrandswithintheirtransferlength.
4. Bearing stresses must remain within limits at service loads. Consider any reducedbearingareaabovethebearingdeviceduetoavoidinthebeamatitsbearing.
Conditionofthecrackunderdeadloadofgirderalone:
1. If thecrack isatthetopofagirderwhosetopflange istobetheridingsurfaceand isexposedtotensilestresses,itshouldbeinjectedorgravityfilledtopreventintrusionofwater, since the crack may remain open. Check stresses if the section is changedsignificantlybythedepthofcracking.
Conditionofthecrackunderdeadloadofgirderplusdeckslab:
1. Ifthecrackisatthetopofthegirderandisexposedtotensilestressesunderthedeadloadweightofthebeamplusslab, itshouldbe injectedtoprevent intrusionofwater,sincethecrackmayremainopen.Checkstresses if thesection ischangedsignificantlybythedepthofcracking.
2. Inmost cases, the crackwill go into compressionwith theweightof thedeckandnorepairwillberequired,unlessrequiredbyotherconditions.
3. An evaluation of the effects of other incidental issuesmay be required, including theeffects that cracking may have on the deck forming system and post-tensioninganchorages.
Note: Full development of exposedmild steel reinforcement can be restored by a properlyinstalledrepairprocedure.Ifthestrandhaslostsomeorallofitsprestressduetoacrackorvoidneartheend,however,itcannotberestoredatthatlocation.Transfermustoccurbeyondthelocation of the void. On the other hand, exposed strand beyond the transfer length can beassumedtohavefullprestressasthoughitwereneverexposed.
11
RepairableNon-conformancesThestandard repairprocedurescontainedherein include recommended repair criteria for thevariousnon-conformancesthataretypicallyencounteredduringthenormalfabricationprocess.Precastconcreteunitsthatcontainminordefectscausedbymanufactureormishandlingshouldbe repairedat themanufacturingsite. Inaddition,units thatcontainminordefectscausedbymishandlingduringshipmentorinstallationshouldberepairedattheprojectsite.
Non-RepairableNon-conformancesNon-repairablenon-conformancesmaybegroundsforrejectionoftheelement.Rejectionofaprecastelementshouldbeconsideredunderthefollowingconditions:
1. When thenon-conformances indicate a significant lackof conformancewith standardpractices and procedures. This includes elements having a significant number ofrepairable defects indicative of a lack of process management such as properconsolidationofconcreteandinadequatehandlingandstorage.
2. Amajordefectthataffectsthestructuralintegrityordurabilityoftheunit.Thistypeofdefectshouldbethoroughlyevaluatedbyallpartiesthroughanon-conformancereportorsimilarprocess.
Iftheproducerfollowsnormalproceduresandtheelementstillpresentsmanydefects,thenthedesignshouldbereviewedandadesignchangemaybeinorder.Forexample,abeamwithhighreleasetensilestressesmaybemorepronetocracking.
12
Section2:TroubleshootingGuideSection2.1:PrestressedElements
TS#1:TransverseCracksOriginatingatTopsofBeams TS#2:VerticalandDiagonalCracksatBottomofBeams TS#3:VerticalThroughCracksinBeams TS#4:HorizontalEndCracksinWebsandFlanges TS#5:BottomFlangeCracksatBeamEnds TS#6:CornerSpallsorCornerCracks TS#7:PartiallyCrackedTopFlanges TS#8:RandomHoneycombingandVoids TS#9:RandomTopFlangeCracks TS#10:ShortProjectedStrandorReinforcing,MissingProjectedStrandorReinforcing TS#11:CracksandHoneycombinginPrecast,PartialDepthDeckPanels TS#12:PartiallyCrackedTopFlanges–NEXTBeams
13
14
TS#1:TROUBLESHOOTINGFORTRANSVERSECRACKSORIGINATINGATTOPSOFBEAMS
Description: Thesecracksare typicallyperpendicular to the longitudinalaxisof thebeamandextendacrossthetopofthemember,usuallyvisibleonbothverticalfaces,butdonotextendtothe bottom prestress strands.
CAUSESA.Excessivetopfibertension
1. Releasestressesinexcessofmodulusofruptureofconcreteatrelease
2. Inadequatetopreinforcement3. Incorrectplacementoftop
reinforcement4. Lowreleasestrength5. Lackofstranddebondingatbeamends
orinsufficientnumberofdrapedstrands6. Improperlocationofliftingordunnage
points7. Prestressupliftforceatmid-span
hold-downpointsexceedstheweightofthebeamorexceedsthebeam’stopfibertensilecapacity
B. Shrinkage
1. Shrinkageofbeamconcretepriortoorduringcuring
2. Contractionofbeampriortoprestressforcerelease
3. Contractionofexposedstrandinunusedportionofthebed
C. FormExpansionwithTemperatureRiseD. ExcessiveSidetension
DueToLateralDisplacementDuringMovement
PREVENTION
A. ReduceTopFiberTension1. Review/modifydesigntoreducetop
tensionatrelease2. Provideadequatetensilereinforcement
tocontrolcracksoraddtopprestressing.Thisoptionmayincludelightlytensionedstrand(5000psi+).
3. Improveinspectionpriortoconcreteplacement
4. Increasereleasestrength5. Reduceeccentricityatbeamendsby
debondingordrapingstrandpattern,addstrandsattopsofbeamsormodifystrandpatterntoreduceeccentricity
6. Adjustliftingordunnagepoints7. Limitupliftforceathold-downpointsto
75percentofmemberweight
B. ImproveProductionMethods1. MinimizeShrinkage
b. Applycoversrapidlyand/ormistspraywithwater
c. Adjustconcretemixbyreducingcement,addingpozzolansorchangingaggregategradation
d. Provideuniformheatandhumidity
2. Detensionascoversareremovedandpreventrapidcool-downofthebeam
3. Preventexposedstrandfromcoolingdifferentiallywithrespecttothebeam
C. LengthenSetTime-InAccordancewithASTMC4031. Minimizetemperaturedifferential
betweenbeam,exposedstrand,andbed
15
2. Detensionascoversareremovedanddonotallowsectiontocoolrapidly
D. ProvideLateralBracingwith
StrongbacksTS#1:TROUBLESHOOTINGFORTRANSVERSECRACKSORIGINATINGATTOPSOFBEAMS
Description:Thesecracksaretypicallyperpendiculartothelongitudinalaxisofthebeamandextendacrossthetopofthemember,usuallyvisibleonbothverticalfaces,butdonotextendtothebottomprestressstrands.
ENGINEERINGEFFECTS 1. Cracksthatcloseupondetensioningofthe
beam,orthatwillclosewhenthebeamisplaceduponitsdesignatedbearingareas,orcanbeexpectedtoclosewhenthecompositeslabispoured,neednotberepairedforsimplebeamapplications.Forbeamsmadecontinuousforcompositedeadandliveloads,calculationsmayberequiredtodeterminetheneedforrepair.Ifstressesunderserviceloadsdonotexceed3.0√f’c,itmaybepresumedthatthebeamwillbehaveasanun-crackedsection,inwhichcasenorepairsarenecessary.Ifthestressesexceed3.0√f’c,thebeamshouldberepairedbyepoxyinjection.
2. Forcracksthatdonotcloseafter
detensioning,anassessmentoftheneedtorepairbasedoncontinuityconsiderationsaswellasenvironmentalexposurewillberequired.Inthelatterregard,ACICommittee224report“ControlofCrackinginConcreteStructures”statesthattolerablecrackwidthsare0.006-in.forconcreteexposedtoseawaterspraywithwettinganddrying,0.007-in.forconcreteexposedtode-icingchemicals,and0.012-in.forconcreteexposedtohumidity.
REPAIRCONSIDERATIONSBeforeDetensioning.Norepairsarerecommendeduntilafterdetensioning,ascracksmayclose.AfterDetensioning1. Closedcracks–Thedecisiontorepairornot
repairshouldbemadeinconsiderationoftheEngineeringEffects.
2. Cracksover0.006in.-Ifthedecisionis
madethatrepairsarewarranted,thecracksshouldbeepoxyinjectedinaccordancewithStandardRepairProcedure#10.
3. Thesurfaceofcracksnarrowerthan0.006-
inchesshouldbesealed.SeeStandardRepairProcedure#14.
16
17
TS#2:TROUBLESHOOTINGVERTICALANDDIAGONALCRACKSATBOTTOMOFBEAMSDescription: Thiscrackstartsatthebottomofthememberandextendsupward.Inseverecases,crack
willextenddiagonallytowardthemid-height(neutralaxis)ofthebeam.
CAUSE
A. Bondofstrands1. Strandcontamination2. Incorrectplacementofdebonding
shields3. Insufficientvibrationofconcrete4. Excessivedebondingterminationatone
locationB. ShrinkageC. DetensioningProcedure
1. Lowreleasestrength2. Improperdetensioning
sequence/procedures3. Failuretoreleasehold-downmechanism
priortoreleaseofhorizontalstrandsD. Formwork
1. Indentationsorjointoffsetsinforms2. Concretebindingtoforms3. Bottomplatesatbeamendsanchoredor
hungupatbottom(soffit)offormE. IncorrectPrestressForce
1. Inadequateprestressstrandindesign2. Under-estimateofprestresslosses3. Under–tensioningofstrand4. Incorrectnumberofstrandinbed
PREVENTIONA. Ensureagainstunintendedslip
1. Inspectstrandforcleanlinessandabsenceoflubricantsafterstressingstrand
2. Verifypropershieldinginstallation3. Useinternalandexternalvibrationin
congestedendsofbeams4. Staggerdebondingterminations
B. ImproveProductionMethods1. Applycoversrapidlyafterconcrete
pours2. Detensionascoversareremoved3. Preventexposedstrandfromcooling
differentiallywithrespecttothebeam
4. Adjustconcretemixbyreducingcement,addingpozzolansorchangingaggregategradation
5. Provideuniformheatandhumidity
C. Useproperdetensioningprocedure1. Ensureproperconcretestrength
priortorelease2. Keepprestressedforcesbalanced
whiledetensioning,usinganestablishedprocedure
3. Ensurehold-downsarereleasedpriortodetensioningstrandandarenotbindingonthesoffit
D. Inspectformconditionpriortoplacing
Concrete1. Ensuresmoothformalignment2. Oilformsthoroughly3. Ensureanybottomplateswillnot
bindonsoffit
E. ApplyCorrectPrestressForce1. Checkdesigncalculations2. Recomputelosses3. Comparemeasuredelongationof
strandwithcomputedelongation4. Checkshopdrawings
18
5. Checkcamberofbeamversescalculatedcamber
TS#2:TROUBLESHOOTINGVERTICALANDDIAGONALCRACKSATBOTTOMOFBEAMS
Description: Thiscrackstartsatthebottomofthememberandextendsupward.Inseverecases,crackwillextenddiagonallytowardthemid-height(neutralaxis)ofthebeam.
ENGINEERINGEFFECTS1. Forverticalcracksthatinterceptbondedor
debondedstrandwithintheirrespectivetransferlengths,itisrecommendedthattheengineerre-computethemomentandshearcapacitybasedontransferinitiatingatthepointofthecrack.Ifthere-computedcapacitiesareacceptablethebeamcanberepaired.Thesecracksshouldbeinjected.
2. Verticalcracksthatinterceptbondedordebondedstrandbeyondtheirrespectivetransferlengthsandclosetoawidthlessthan0.006-in.afterdetensioning,neednore-evaluation.Cracks0.006-in.orgreaterinwidthshouldbereferredtotheengineerforevaluation,toaffirmadequatedesign.
3. Verticalcracksatanylocationonthebeamthatdonotinterceptstrandneednoevaluationbytheengineer.
4. Diagonalcracksofanysize,atanylocation,requireevaluationbytheengineer,todeterminewhetherthesheardesignforthebeamisadequateortheaccidentalloadingcausingthecrackwillnotbeduplicatedinservice.
REPAIRCONSIDERATIONS1. Itisrecommendedthatcracksnotbe
repairedpriortodetensioningasrepairswillmaskthecauseandseriousnessofthecrack.
2. Allcrackslessthan0.006-in.inwidth,afterdetensioninganddeemedacceptable,shouldbesealed.SeeStandardRepairProcedure#14.Ifthesecracksarewithinthetransferzone,anepoxyinjectionrepairshouldbeconsidered(seebelow).
3. Allcracks0.006-in.orgreaterinwidth,afterdetensioninganddeemedacceptable,shouldberepairedbyepoxyinjectioninaccordancewithStandardRepairProcedure#10.
19
20
TS#3:TROUBLESHOOTINGVERTICALTHROUGHCRACKSINBEAMS
Description:Thesecrackscandevelopinbeamsduringthecuringprocessorcool-downperiodpriortodetensioningofstrand.Thisproblemismorecommontolongbeamsmanufacturedwithhigherstrengthconcrete.
CAUSEA.Shrinkage1. Shrinkageofthebeampriorto
detensioningB.TemperatureEffects1. Contractionofexposedstrandinunused
portionofbed2. Contractionofbeamduetocoolingprior
totransferofprestress3. Unevendistributionofheat
C.Production/Formwork1. Indentationsorjointoffsetsinforms2. Concretebindingtoforms3. Bottomplateatendofmemberanchored
orrestrainedinform
PREVENTIONA.Reviewormodifythemixormodifycuring
methodstoreduceshrinkage1. Considerchangetoalternatemix(seenote)
2. ApplycuringcoversrapidlyB.ControlTemperatureDuringProduction
1. Minimizetemperaturedifferentialbetweenbeam,exposedstrand,andbed
2. Detensionascoversareremovedanddonotallowsectiontocoolrapidly
3. Provideuniformheatandhumidityduringcuring
C.Improveproductionmethods
1. Keepformsingoodrepair;fabricateformswitheven,smoothjoints
2. Keepformscleanandproperlyoiled3. Releaserestraintofallplatesbeforedetensioning
Note:Modificationstomixdesignsmaynotbe
possibleincertainsituationsduetoownerpre-qualificationrequirementsformixes.
Reference:Zia,Paul,andCaner,Alp,“CrackinginLong-SpanPrestressedConcreteAASHTOGirdersDuringProduction”,CenterforTransportationEngineeringStudies,NorthCarolinaStateUniversity,Raleigh,N.C.
21
TS#3:TROUBLESHOOTINGVERTICALTHROUGHCRACKSINBEAMS
Description:Thesecrackscandevelopinbeamsduringthecuringprocessorcool-downperiodpriortodetensioningofstrand.Thisproblemismorecommontolongbeamsmanufacturedwithhigherstrengthconcrete.
ENGINEERINGEFFECTS1. Forcracksfallingwithinthetransferlengthof
bondedordebondedstrand,itisrecommendedthattheengineerre-computethemomentandshearcapacitybasedontransferinitiatingatthepointofthecrack.Ifthere-computedcapacitiesareacceptablethebeamcanberepaired.Thesecracksshouldbeinjected.
2. Forcracksfallingbeyondthetransferlengthofbondedordebondedstrandthathaveawidthof0.006inchorless,afterdetensioning,noreevaluationisneeded.Cracksgreaterthan0.006inchshouldbereferredtotheengineerforevaluation.
3. Fulldepthcracksthatcloseafterdetensioningtoawidthoflessthan0.006-in.,orare0.006-in.orgreaterandrepairedmeettheconstitutiverulesofthemodifiedcompressionfieldtheoryforshearcapacity.Thesubjecttheory,asabasicgiven,presumesafulldepthcrackalongtheinclinedplaneofthetadegrees.Underfulldesignloadifthebottomflangeatthepre-existingcrackgoesintotension,thecrackwillopenalongitsverticalpathuntiltheneutralaxisisreached,atwhichpointthecrackwillturnandextendalongtheinclinedplane,theta.Asthecompressionstrutcantransmitstressacrosstheverticalportionofthecrack,theconstitutiverulesarenotcompromised
REPAIRCONSIDERATIONS1. Itisrecommendedthatcracksnotbe
repairedpriortodetensioningasrepairswillmaskthecauseandseriousnessofthecrack.
2. Allcrackslessthan0.006-in.inwidth,afterdetensioninganddeemedacceptable,shouldbesealed.SeeRepairProcedure#14.Ifthesecracksarewithinthetransferzone,anepoxyinjectionrepairshouldbeconsidered(seebelow).
3. Allcracks0.006-in.inwidth,afterdetensioninganddeemedacceptable,shouldberepairedbyepoxyinjectioninaccordancewithStandardRepairProcedure#10.
22
TS#4:TROUBLESHOOTINGHORIZONTALENDCRACKSINWEBSANDFLANGES
Description: Thiscrackusuallybeginsattheendofthebeamandextendsacrosstheendofthebeamandisvisibleonbothsides.
CAUSEA. Detensioning
1. Improperproceduresfordetensioningstrands
2. ImproperdetensioningsequenceB. Design
1. Lowreleasestrengthspecified2. Inadequateendverticalreinforcing3. Excessiveprestressforceor
concentrationofforce4. Excessivenumberofdebondedstrands
inthebottomplaneand/orlackofconfiningstirrups
5. Excessiveverticalforcefromdeflectedstrands
C. Production
1. Concretebindinginforms2. Bottomplates,sleevesorinsertsatend
ofbeam3. Shrinkageandcuring4. Improperremovalofheaderorstrand
caughtinheader5. Settlementofwetconcretebelowa
concentrationofstrandormildreinforcingnearthetopatbeamend
6. Forboxbeams,delayedwebpourscausingacoldjoint
PREVENTIONA. ProperReleaseProcedure
1. Heatstrandtoallowslowelongation(annealing)andavoidsuddenrelease
2. Keepprestressforcesbalancedusingapre-stablishedprocedure(seeNote)
B. ImproveDesign
1. Establishadequatereleasestrength2. Useadequateanchoragezoneend
reinforcementtocontrolwidthandlengthofcracks
3. Properlyspaceanddistributestrandatbeamends
4. Debondingstrandsforashortdistanceiseffectiveinreducingstressconcentrations.Debondingofanentirerowofstrandordebondingtheouterstrandinalayerarenotrecommended.Provideconfinementreinforcementnearbeamends
5. Fanoutdeflectedstrandsorcombinedebondinganddeflectingstrand
C. ImproveProductionTechnique
1. Keepformswelloiled2. Ensureformswillnotinterferewith
hardwareifformsexpandorduringdetensioning
3. Provideuniformheatandhumidityduringcuring
4. Separateheaderfromformsbeforelifting
5. Improvevibrationtechniques6. Pourwebspriortosetofbottomslabof
boxbeamsNote:Balancingofprestressforceiskeyto
minimizingthepotentialforhorizontalcracks.See“ReleaseMethodologyofPrestressStrands”,KannelJ.,FrenchC.andStolurski,H.,PCIJournalVol.42,No.1,Jan-Feb.1997,pp.42-55
23
TS#4:TROUBLESHOOTINGHORIZONTALENDCRACKSINWEBSANDFLANGES
Description: Thiscrackusuallybeginsattheendofthebeamandextendsacrosstheendofthebeamandisvisibleonbothsides.
ENGINEERINGEFFECTS1. Cracksnotinterceptingstrandarenotof
structuralconsequence,providedtheareaofverticalshearreinforcementinthewebsmeetshorizontalshearrequirements.Afterinstallationofthebeams,thecrackswouldnotbeexpectedtogrow,givenadequatereinforcementagainsthorizontalshear,sincethedeadloadweightoftheslabandotherdeadloadswillinduceverticalcompressioninthebeamsends.
2. Forcracksthatinterceptorareco-linearwithstrands,theshearandmomentcapacitywillrequirere-computationduetoachangeinlocationoftransferlengthofaffectedstrands.
3. Cracksinbeamendsunderexpansionjoints,shouldbeconsideredforepoxyinjectiontoavoidfuturedeteriorationfromwaterandsaltintrusion.Cracksinboxbeams,inside-by-side(butted)configurationsshouldbeepoxyinjectedinanycaseduetopotentialleakagethroughgroutedjoints.
4. Indecidingwhethertoinjectcracksorleavethemunfilled,ACICommittee224report“ControlofCrackinginConcreteStructures”statesthattolerablecrackwidthsare0.006-in.forconcreteexposedtoseawaterspraywithwettinganddrying,0.007-in.forconcretesubjecttode-icingchemicalsand0.012-in.forconcreteexposedtohumidity.
REPAIRCONSIDERATIONS
1. NorepairstobeamsusedincompositeconstructioninaccordancewiththediscussioninENGINEERINGEFFECTS1.
2. ForcracksdiscussedinENGINEERINGEFFECTS2:a. Cracksthathavebeenverifiedby
theownertonothavediminishedthebeamcapacitybelowacceptablelevelsshouldbeinjected,inaccordancewithStandardRepairProcedure#10.
b. Beamsverifiedbytheengineertohavecapacityreducedtounacceptablelevelswillberejected.
3. Durabilityconcerns,discussedinENGINEERINGEFFECTS3and4mayfavorepoxyinjection,inaccordancewithStandardRepairProcedure#10.Thesurfaceofcracksnarrowerthan0.006-inchesshouldbesealed.SeeRepairProcedure#14.
24
TS#5:TROUBLESHOOTINGBOTTOMFLANGECRACKSATBEAMENDSDescription: Thecrackislocatedattheendofthebeamandgenerallyrunsparalleltothelongitudinal
axis.CAUSEA. Production
1. Bindingintheformsduringstripping2. Indentationintheforms3. Improperdetensioningsequence
BReinforcement
1. Incorrectplacementoromissionofconfiningreinforcement
2. Reinforcementimproperlydetailedorfabricated
3. Debondingproblem4. Contaminatedstrand
C. Detensioning
1. Localizeddifferentialstrainsandstressesbetweenthewebandflangeduringdetensioning
D. Handling
1. Non-uniformbearingondunnageorimpactwhilebeingloweredondunnage
PREVENTIONA. ImproveProduction
1. Keepformswell-oiledandclean2. Keepformsingoodrepair3. Keepforcesbalancedduring
detensioningB. AttentiontoReinforcingDetails
1. Verifycorrectplacementofreinforcement
2. Scrutinizedrawingsandfabricatedbarstobeused
3. Allowforswelling(HoyerEffect)ofdetensionedstrandthathavebeendebondedbyprovidingconfinementreinforcingorrelocatingdebondedstrandsawayfromedgesoftheflange.
4. Inspectstrandforcontaminationandoilresiduefrommanufacturing
C. Detensioning
1. Heatstrandtoallowslowelongation(annealing)tominimizeshockofdetensioning
D.Handling
1. Ensureuniformbearingandavoidimpactswhenhandlingbeams
25
TS#5:TROUBLESHOOTINGBOTTOMFLANGECRACKSATBEAMENDS
Description: Thecrackislocatedattheendofthebeamandgenerallyrunsparalleltothelongitudinalaxis.
ENGINEERINGEFFECTS1. Cracksco-linearwithstrandsaffectthe
unbondedlengthanditwillbenecessarytorecomputetheshearandmomentcapacitybasedontherevisedtransferand/ordevelopmentlengthlocationforthestrands.Weakaxisbendingmayneedchecking.
2. Inanyevent,thesecracksshouldberepairedtoensuretheintegrityofthebearingareaandtopreventwaterandsaltintrusionatexpansiondevicesorthroughgroutedshearkeysofside-by-side(butted)boxbeams.
REPAIRCONSIDERATIONS
1. AllbottomflangecracksshouldbeepoxyinjectedinaccordancewithStandardRepairProcedure#10
2. INthecaseofstrandinvolvement,theengineershouldbenotifiedtoassessconditionspriortorepairs.
26
TS#6:TROUBLESHOOTINGCORNERSPALLSORCORNERCRACKS
Description: Thesespallsandcrackscanbefoundatanyedgeorcornerofflangesalongthebeam
CAUSEA. ImproperHandling
1. Impactingedges2. Unevendunnage
B. Production
1. Bindinginformsduringstripping2. Indentationinforms3. Insertshangingupinforms4. Soleplatesnotflushwithsoffitof
forms5. Impropershieldingofstrands6. Thermalexpansionofformspriorto
concretesetting7. Improperbulkheadremoval8. Bleedingofconcreteunderheader
C. ReleaseProcedures
1. Improperdetensioningsequence2. Bindinginformsduringdetensioning3. Draggingofbottomflangeendinduced
bycamberingandshorteningatdetensioning
4. Impactandburstingforcesfromdetensionedstrand
D. Design
1. Inadequateedgereinforcement
PREVENTIONA. CareinHandling
1. Ensureadequateroomfortransportofbeams
2. ProvideuniformdunnageB. ImproveProductionMethods
1. Keepformscleanandwelloiled2. Keepformsingoodconditionand
ensureallseamsaremortartight3. Ensureinsertsarefreeduringstripping4. Ensuresoleplatesareflushwithsoffit
priortoconcretepours5. Shieldinginthebottomrowofstrands
shouldbeminimizedandshieldingofstrandsadjacenttotheedgesofflangesshouldbeavoided
6. Ensureconcretesetpriortostartingcuring
7. Keepbulkheadsingoodconditionandwell-oiledtoavoidtheneedtoprythemloose
8. Providemortar-tightheader
C. ProperReleaseProcedures1. Keepprestressforcesbalancedduring
detensioning2. Providesufficientclearancebetween
formsandbeamduringdetensioning3. Provideskidplates,radii,bevelsor
compressiblematerialforthebottomedgeofflanges
4. Heatstrandsufficientlytoslowlyelongate(annealing)toavoidimpactandtomitigateswellingofstrand(HoyerEffect)atrelease
5. Ensureallstrandsarecompletelyseveredpriortoremovalfromforms
D. Design1. Provideproperreinforcementasclose
toedgesasclearancerequirementsallow
27
TS#6:TROUBLESHOOTINGCORNERSPALLSORCORNERCRACKS
Description: Thesespallsandcrackscanbefoundatanyedgeorcornerofflangesalongthebeam
ENGINEERINGEFFECTS1. Cornerspallsintopflangesusedasthe
ridingsurfaceofthecompletedbridgerequirerepairtoensuresufficientliveloadcapacityanddurability
2. Cornerspallsinbearingareasofbeamsshouldberepairedtoensureproperbearingsaswellastoprotectstrandsfromwaterandsaltintrusionwhenbeamendsareadjacenttoexpansionjoints.
3. Cornerspallsinthebottomflangethatmaysignificantlyreduceprotectionfromsaltandwatersprayfromtrafficunderneathorleakinggroutedjointsfromabove,suchasside-by-sideboxesanddeckbulb-tees,shouldberepaired.
4. Ifstrandsareexposed,theengineeringeffectshouldbereviewedbytheEngineer.
5. Topflangeedgesincorporatedintoslabpoursneednotberepaired
REPAIRCONSIDERATIONS1. Wherecornerspallsaredeemedinneedof
repair,therepairsshouldbemadeinaccordancewithStandardRepairProcedures#3or#4
2. Cornerspallsonedgestobeincorporatedintocompositeslaborenddiaphragmsmaynotneedrepair
3. Minorspallsthatdonotcompromiseprotectionfromwater,saltsprayorhumidity,orarenotexposedtodirectviewneednotberepaired
28
TS#7:TROUBLESHOOTINGPARTIALLYCRACKEDTOPFLANGES
Description: Thecrackwidthisusuallyvisibleandexhibitsacleanbreakline.
CAUSEA. Handling
1. ImpactingedgesB. Production
1. Bindinginformsduringstripping2. Placementofconcreteinexcessively
hotforms3. Thermalexpansionofformspriorto
concretesettingorcontractionduringcool-down
C. ReleaseProcedures
1. Improperdetensioningsequence2. Strandsnotfreefrombulkhead
D. StrandPlacement
1. Concentrationofprestressingforcesattheedgesoftopflanges
PREVENTION
A. ProperHandling1. Ensureadequateroomfortransportof
beamsB. ImproveProductionMethods
1. Keepformscleanandwelloiled.Keepformsingoodrepair,freeofdentsanddimples
2. Ensureformsarecooledtoanappropriatetemperaturepriortoplacingconcrete
3. Regulateheatduringcuringandcool-downuniformly
C. ProperReleaseProcedures
1. Keepprestressforcesbalancedduringdetensioning
2. Ensureanytopstrandsarecompletelyseveredpriortoremovalfromforms
3. Providesufficientclearancebetweenformsandbeamsduringdetensioning
D. ProperDesignDetailing
1. Avoidplacementofprestressnearedgesoftopflange,orifthisisunavoidable,addtransversereinforcementtoflanges
29
TS#7:TROUBLESHOOTINGPARTIALLYCRACKEDTOPFLANGES
Description: Thecrackwidthisusuallyvisibleandexhibitsacleanbreakline.
ENGINEERINGEFFECTS
1. Forbeamswhosetopflangeistobeusedas
theridingsurfaceofthecompletedbridge,cracksinthetopflangecanaffectdurabilityandliveloadcapacity,ifnotrepaired
2. Forbeamstoreceiveacast-in-placeslab,repairsmaynotbewarranted
REPAIRCONSIDERATION1. Whenthetopflangeistobetheriding
surface,andconcreteisdisplaced,fracturedorloose,useStandardRepairProcedure#6.IfthecrackiscleanandnoconcreteisdisplaceduseStandardRepairProcedures#10.
2. Whenthetopflangeistobeencasedinacast-in-placeslab,andconcreteintheflangeisdisplaced,theengineershouldbenotifiedtodetermineiftheflangeshouldberepairedusingStandardRepairProcedures#6orifthedisplacedconcretecanbeleftandencasedintheslab.Ifthecrackiscleanandnoconcreteisdisplaced,norepairsarewarranted.
30
TS#8:TROUBLESHOOTINGRANDOMHONEYCOMBINGANDVOIDSDescription: Missingvolumeofcementpastefromaroundaggregateorvoidscontainingneitherpaste
noraggregate,inflangesandwebs.
CAUSEA. Production
1. Inadequatevibration2. Improperplacementofconcrete3. Shifted/misplacedrebarcage
B. ConcreteMixDesign
1. Mixtoostiff2. Earlysetinplasticizedconcrete3. Delayedplacementofconcrete4. Flashsetofconcreteinforms
C. DesignDetails
1. Congestedreinforcement
PREVENTIONA. ImprovedProductionProcedures
1. Providethoroughinternaland,wherewarranted,externalvibration
2. Startplacementawayfrombulkheadsandusevibrationtocausetheconcretetoflowtowardbulkheads
3. Verifylocationofandanchorreinforcement
B. AdjustMixDesign
1. Considerchangetoalternatemix(seenote)
2. Improvedeliverytimeoftheconcrete3. Coolformspriortoconcrete
placementC. ImproveDetails
1. Reducereinforcementcongestiontotheextentpossible
2. Provideclearspacingbetweenreinforcementlargerthan1½timesthemaximumaggregatesize
Note:Modificationstomixdesignsmaynotbe
possibleincertainsituationsduetoownerpre-qualificationrequirementsformixes.
31
TS#8:TROUBLESHOOTINGRANDOMHONEYCOMBINGANDVOIDS
Description: Missingvolumeofcementpastefromaroundaggregateorvoidscontainingneitherpaste
noraggregate,inflangesandwebs.ENGINEERINGEFFECTS1. Honeycombingandvoidsinbearingareas
notonlyaffectthestrengthanddurabilityofthebearingbut,themomentcapacityifbondonthestrandisimpacted.Undermodifiedcompressionfieldtheory,lossofbondofstrandcanalsoaffectshearcapacity.Theseareasmustberepaired.Honeycombingandvoidsinotherareasofthebottomflangecanaffectmomentcapacity,butmorelikely,onlydurability.
2. Honeycombingandvoidsinwebsaffectshearcapacityandmustberepaired.
3. Honeycombingandvoidsintopflangesthatwillbetheridingsurfaceofthebridgeaffectbothmomentcapacityanddurability,requiringrepair.Wherethetopflangeistobeencasedinacast-in-placeslab,thehoneycombingandvoidsmaysignificantlyaffectthenon-compositestrengthbutnotdurability.
4. Ifstrandsareexposed,theengineeringeffectshouldbereviewedbytheEngineer.
REPAIRCONSIDERATIONS1. ForconditionsdiscussedinEngineering
Effects1,repairusingStandardRepairProcedures#1or#2,asappropriate.
2. ForconditionsdiscussedinEngineeringEffects2,repairusingStandardRepairProcedures#5or#9,asappropriate.
3. ForconditionsdiscussedinEngineeringEffects3,ifrepairsarerequired,useStandardRepairProcedures#6or#9,asappropriate.
32
TS#9TROUBLESHOOTINGRANDOMTOPFLANGECRACKSDescription: Thesecracksaregenerallyorientedlongitudinallyandareshallowindepth,occurringina
randompattern,oftenparallelwithreinforcement.CAUSEA. Shrinkage
1. Excessbleedwateratthetopflangesurface
2. Rapidmoisturelosspriortocuring3. Excessivecuringtemperature4. Delayedstartofcuring
B. ConcretePlacement
1. Settlementofconcretearoundtopreinforcement(subsidence)
2. InsufficientVibration
PREVENTIONA. PreventShrinkage
1. Reducewaterinmixandoravoidover-workingsurfacefinish
2. Useretardantadmixturescoverbeamscompletelyandassoonaspossible(especiallyinwindy,hotanddryconditions).Ifnecessary,mist-sprayexposedtopflangesurface,withwater.
3. Reducecuringtemperature4. Determineproperpre-settimetosuit
curingoperations,usingASTMC403.Limitstartofcuringto2-3hours
B. ImprovePlacementMethods
1. Allowtimeforinitialsettlement,andre-vibrateconcrete
2. Ensurepropervibrationtoconsolidateconcrete
33
TS#9TROUBLESHOOTINGRANDOMTOPFLANGECRACKS
Description: Thesecracksaregenerallyorientedlongitudinallyandareshallowindepth,occurringina
randompattern,oftenparallelwithreinforcement.
ENGINEERINGEFFECTS1. Otherthanconcernfordurabilityfortop
flangesthatwillbecometheridingsurfaceofthecompletedbridge,therearenoconcerns.Thesecrackswillbecoveredbytheslabincompositeconstruction
REPAIRCONSIDERATIONS1. Wherethetopflangewillbetheriding
surface,sealwithalowviscosityepoxyormethylmethacrylateproduct.
2. Wherecompositeconstructionisused,norepairsareneeded.
34
TS#10TROUBLESHOOTINGSHORTPROJECTEDSTRANDORREINFORCING,MISSINGPROJECTEDSTRANDORREINFORCING
Description: Thistypeofdefectisusuallycausedbyimproperproductiondetailing.Itisusuallylimited
toprojectingstrandorreinforcingforcontinuityconnectionsorhorizontalshearreinforcing.
CAUSEA. Formwork
1. BulkheadshiftB. Reinforcement
1. Improperplacement2. Impropercutting3. Improperbending4. Incorrectfabricationdrawingordesign
drawing5. Shiftingduringcasting6. Improperhandling
PREVENTIONA. Formwork
1. CheckbulkheadlocationsandintegrityB. Reinforcement
1. Re-checkreinforcing/strandlocationspriortoconcreteplacement
2. Re-checkstrand/reinforcinglengthsbeforecutting
3. FollowCRSIrequirementsforminimumbendingradius
4. Re-checkfabricationanddesigndrawings
5. Placeadditionaltiesonreinforcement6. Reviewshophandlingpractices
35
TS#10TROUBLESHOOTINGSHORTPROJECTEDSTRANDORREINFORCING,MISSINGPROJECTEDSTRANDORREINFORCINGDescription: Thistypeofdefectisusuallycausedbyimproperproductiondetailing.Itisusuallylimited
toprojectingstrandorreinforcingforcontinuityconnectionsorhorizontalshearreinforcing.
ENGINEERINGEFFECTS1. Missingstirrupscanmateriallyaffectthe
horizontalshearcapacityaswellasverticalshearcapacity.Calculationsmayverifynosignificantreductioninshearcapacity.Ifso,repairmaynotbenecessary.
2. Missingprojectingstrandwillreducethepositivemomentrestraintcapacityattheinteriorsupportsofbeamsmadecontinuousforcompositedeadandliveloads.
3. Whereprojectedstrandaretobedevelopedwithincast-in-placediaphragms,toensureadequatelongitudinaltensiontiecapacityforbeamverticalsheardesignmaybecompromised.RefertoAASHTOLRFDArticle5.8.3.5.
Note1:Repairsshallnotbemadewithoutthedesigner’sapproval;thefollowingaregeneralguidelines:Note2:Ifacceptabletotheowner,asmallamountofconcretecanberemovedandthestrandcanberepairedasashortprojectingstrand
REPAIRCONSIDERATIONS
MissingProjectedStrandreplacedwithgroutedrebar(seeNote2)1. Thisprocedureshouldonlybeusedforrepairing
upto25%oftheprojectingstrand.2. Eachmissingstrandshallbereplacedbytwo#6
rebargroutedadjacenttothemissingelementwith24”ofembedment
3. Thegroutedrebarshallbeascloseaspracticaltothemissingelement.
4. SeeStandardRepairProcedure#12MissingProjectedRebar1. Thisprocedureshouldonlybeusedforrepairing
upto25%oftheprojectedreinforcingatbeamends.
2. EachmissingrebarshallbereplacedbyanequivalentsizedGrade60rebar.
3. Theembedmentshallbesufficienttodevelopafulllapsplicewiththeinternalreinforcingwheretensiontransferisrequired.
4. Theminimumembedmentforothersituationsshallbebasedonthechemicaladhesivemanufacturer’srecommendations.
5. SeeStandardRepairProcedure#12ShortProjectingRebar1. Useamechanicalcouplerthatisapprovedby
theOwner,installedasperthemanufacturer’srecommendations
2. SeeStandardRepairProcedure#11.ShortProjectingStrands1. Thisprocedurecanbeusedforanynumberof
shortprojectingstrandsperbeamthathassufficientstrandremainingthatistightlywoundinordertofollowthisrepairprocedure;ifthiscan’tbemet,treatasamissingstrand.Saw-cutstrandcleanlywithacutoffsawandinstallaself-seatingsplicechuckwithadditionalpieceofstrand.
2. SeeStandardRepairProcedure#11.
36
TS#11TROUBLESHOOTINGCRACKSANDHONEYCOMBINGINPRECAST,PARTIALDEPTH
DECKPANELSDescription:Longitudinal,transverseanddiagonalcracks,andhoneycombinginpanels.CAUSESA. Longitudinalcracksrunningco-linearto
strands1. Improperdetensioningprocedures2. Excessiveprestressingforce3. Inadequateendreinforcement
transversetostrandpattern4. Castingconcreteinhotforms5. Lowreleasestrengthofconcrete
B. Longitudinalcracksnotco-lineartostrand,
transversecracksordiagonalcracksinpanels1. Improperhandling(impact)2. Improperstorage3. Shrinkage4. Improperdetensioningprocedures5. Strandpatterneccentrictopanelmid-
depthC. RandomHoneycombing
1. Impropervibration
PREVENTIONA. Longitudinalcracksrunningco-linearto
strand1. Keepprestressingforcesbalanced
duringdetensioning.Heatstrandtoensureslowelongationofstrand(annealing)duringdetensioning.
2. Keeptheaverageprestressforceovertheendfaceofpanelsto750psi.
3. Providetransversemildreinforcingsteelaboveandbelowthestrandatpanelends.
4. Coolforms,headers,strandandmildreinforcing,thatcomesincontactwithwetconcrete,atorbelow90°F.
5. Increasereleasestrength.B. Longitudinalcracksnotco-lineartostrand,
transversecracksordiagonalcracksinpanels.1. Provideadequatedraftformoving
panels.Avoidimpacts2. Keepdunnageleveland,uniformly
spaced.Provideuniformbearingofpanelstransversetostrands.
3. Avoidrapidcooling,aftercuringhasstoppedanduntildetensioningiscomplete.
4. Keepprestressingforcesbalancedduringdetensioning.
5. Keepstrandplacementatmid-depth.C. RandomHoneycombing
1.Properlyvibrate
37
TS#11TROUBLESHOOTINGCRACKSANDHONEYCOMBINGINPRECAST,PARTIALDEPTH DECKPANELSDescription:Longitudinal,transverseanddiagonalcracks,andhoneycombinginpanels.ENGINEERINGEFFECTS1. Cracksco-linearwithstrand,either
extendingfromthetoporbottomfacetostrands,orthroughcracksareanindicatorofdebonding.Experiencehasshownthatevencracksthatarepartiallengthofstrandwillcontinuetogrowfulllengthofstrandovertime,evenafterepoxyinjection.Theownershouldbeconsultedwhenmorethan6percentofstrandhavesuchcracks.Twoconsecutivestrandhavingcracksshouldbecauseforrejection.
2. Longitudinalcracks,parallelbutnotco-lineartostrandareofnostructuralconsequence.
3. Transverseanddiagonalcracksthatcrossmorethan6percentofstrandrequireanassessmentbytheowner.Becauseoftherelativelyshortlengthofpanels,comparedtothetransferanddevelopmentlengthofthestrandsitislikelythatanycrackinterceptingstrandswillcausedebonding.
4. Honeycombingnotmorethanone-inchdeep,inthetoporbottomfaceofpanelsandnotofextensiveplanareaareofnostructuralconsequenceifrepaired.Honeycombingdeeperthanone-inchmaycompromisestrandbond.
REPAIRCONSIDERATIONS1. Cracksco-linearwithstrandandextending
fromonefacetothestrand,orthroughcracksco-linearwithstrandovermorethan12percentofstrandshouldberejected.
2. Longitudinalcracksparalleltobutnotco-linearwithstrandthatexceed0.007inchesinwidthshouldbeconsideredforepoxyinjectioninaccordancewithStandardRepairProcedure#10.
3. Transverseordiagonalcracksextendingovermorethan12percentofstrandshouldberejected.
4. Honeycombingnotexceedingone-inchindepthateitherface,ofanacceptableplanarea,shouldberepairedinaccordancewithStandardRepairProcedures#1,#2or#5.
38
TS#12TROUBLESHOOTINGPARTIALLYCRACKEDTOPFLANGES–NEXTBEAMSDescription: Crackrunningparalleltobeamcenterlinealonginsidefaceofstem.
Thiscrackisexpectedinobtusecornersofskewedbeamsadjacenttotheinteriorfaceofthestem,butcanoccurinanybeam.
CAUSE PREVENTION
A. Detensioning
1. Releasestressesbroughtonbyskeweffects.Unevenlift-offofbeamstemsbroughtonbyskew[8].
2. Releasestressesduetounevendetensioningsequencebetweenbeamstems.
3. Bindinginformsduringstripping
A. AdjustReinforcementanddetensioningsequence1. Verifythatadditionalreinforcingsteel
thatisshowninthecurrentPCINortheastrecommendedguidedetailsarebeingusedandinstalledproperly.Note:ThereinforcementdescribedabovewasaddedtothetypicaldetailsonOctober25,2012.
2. Releaseonestrandatatimealternatingfromstemtostem.
3. Keepformscleanandwelloiled.Keepformsingoodrepair,freeofdentsanddimples.
B. Shrinkage
1. Shrinkageoftopflangeconcreterestrictedbythefixed2stemform.
B. ModifyFabricationMethods1. Avoidrapidcooling,aftercuringhasstopped
anduntilbeamisremovedfromform.
39
TS#12TROUBLESHOOTINGPARTIALLYCRACKEDTOPFLANGES–NEXTBEAMS
Description Crackrunningparalleltobeamcenterlinealonginsidefaceofstem.
Thiscrackisexpectedinobtusecornersofskewedbeamsadjacenttotheinteriorfaceofthestem,butcanoccurinanybeam.
ENGINEERINGEFFECT REPAIRCONSIDERATIONS1. Forbeamsthatwillbetoppedwitha
compositeconcreteslab(NEXTF),therearenoconcerns.Thesecrackswillbecoveredbytheslabincompositeconstruction.
2. Forbeamswhosetopflangeistobeusedastheridingsurfaceofthecompletedbridge(NEXTD),cracksinthetopflangecanaffectdurability,ifnotrepaired.
1. Whereacompositeconcretedeckisembeddedinconcreteinthefinishedstructure(integralabutment),nostructuralrepairsareneeded.
2. NEXTF:Ifthecrackisexposedontheundersideofthefinishedstructureandthebridgeisinacorrosiveenvironment:• Crackslessthan0.006inchwideshouldbe
ignored(SeeNote).• Cracksgreaterthanorequalto0.006inch
wideandlessthan0.016inchwideshouldbesealedwithepoxypaste.SeeStandardRepairProcedure#14.
• Cracksgreaterthanorequalto0.016”wideshouldbesealedusingepoxyinjectionbythepressureinjectionmethod.SeeStandardRepairProcedure#10.
3. NEXTD:Wherethetopflangewillbetheridingsurfaceandthecrackwidthisgreaterthan0.006inches,thecrackatthetopsurfaceofthedeckcanbesealedwithalowviscosityepoxyormethylmethacrylateproduct.SeeStandardRepairProcedure14.
Note:TheAASHTOLRFDBridgeDesignSpecificationslimitscrackwidthsinClass2exposureconditions(bridgedecks)to0.0085inches(Article5.7.3.4).Thereforetheserecommendationsareconservative.
40
41
Section2.2:Non-PrestressedPrecastElements
TS#SS1:CornerSpallsTS#SS2:CracksTS#SS3:Honeycombing,Voids,PourLines,andMinorSurfaceImperfectionsTS#SS4:ShortProjectedRebarandMissingProjectedRebarTS#SS5:MissingorMis-LocatedInserts,Voids,orMis-LocatedProjectingRebar
42
TS#SS1:TROUBLESHOOTINGCORNERSPALLSINNON-PRESTRESSEDPRECAST
ELEMENTSDescription Thesespallsandcracksmaybefoundatanyedgeorcorneroftheelement
ThefollowingelementsarecoveredunderthisTroubleShootingGuide:PierElements(columns,caps),AbutmentandWallElements(stems,caps),Foundationelements(footings),orothersimilarnon-prestressedprecastelements.
CAUSE PREVENTIONA. ImproperHandling
1. Impactingedges2. Unevendunnage
A. CareinHandling1. Ensureadequateroomfortransportof
elements2. Provideuniformdunnage.Non-rigid
materialssuchastimberorelastomericpadsarerecommended
B. Production1. Bindinginformsduringstripping2. Indentationinforms3. Insertshangingupinforms4. Thermalexpansionofformspriorto
concretesetting5. Bleedingofconcreteunderheader
B. ImproveProductionMethods1. Keepformscleanandwelloiled2. Keepformsingoodcondition(repair
dents,removeprojections,andmakeseamsmortartight)
3. Ensureinsertsarefreeduringstripping4. Ensureconcretesetpriortostarting
curing5. Providemortar-tightheader
C. Design
1. Inadequateedgereinforcement
D. VerifyDesign1. Provideproperreinforcementascloseto
edgesasclearancerequirementsallow
43
TS#SS1:TROUBLESHOOTINGCORNERSPALLSINNON-PRESTRESSEDPRECAST ELEMENTSDescription Thesespallsandcracksmaybefoundatanyedgeorcorneroftheelement
ENGINEERINGEFFECTS REPAIRCONSIDERATIONS1. Cornerspallsinbeamelementsrequire
repairtoensuresufficientloadcapacityanddurability.
2. Cornerspallsinbearingareasofbeamelementsshouldberepairedtoensureproperbearings.
3. Ifstrandsareexposed,theengineeringeffectshouldbereviewedbytheEngineer.
1. Spallsinareasthatareexposedtotheenvironmentinthefinishedbridgeshouldberepaired.
2. Minorspallsthatdonotcompromiseprotectionfromwater,saltspray,humidity,orarenotexposedtodirectviewneednotberepaired.Forexample:spallsincorporatedintoconcreteclosurepoursorgroutedjoints.
3. Crackslocatednearcornershavethepotentialtobecomeaspallandshouldberepairedafterremovalofcrackedconcrete.
4. Wherecornerspallsaredeemedinneedofrepair,therepairsshouldbemadeinaccordancewithStandardRepairProcedure#15.
44
TS#SS2:TROUBLESHOOTINGFORCRACKSINNON-PRESTRESSEDPRECASTELEMENTSDescription Thesecracksaretypicallyperpendiculartothelongitudinalaxisoftheelementandextend
acrossthemember,oftenvisibleonmultiplefaces.ThefollowingelementsarecoveredunderthisTroubleShootingGuide:PierElements(columns,caps),AbutmentandWallElements(stems,caps),Foundationelements(footings),orothersimilarnon-prestressedprecastelements.
CAUSE PREVENTIONA. Shrinkage
1. Shrinkageofconcreteduringcuringcausingfrictionforcesbetweentheelementandtheform,leadingtoabuild-upofstressesintheelement
A.Reviewormodifythemixormodifycuringmethodstoreduceshrinkage1. Considerchangetoalternatemix(seenote)2. Applycuringcoversrapidly
B. Design1. Inadequatetemperatureandshrinkage
reinforcement
1. VerifyDesign1. Verifythatthereisadequatetemperatureand
shrinkagereinforcementandthatthereinforcementisproperlydistributedwithintheelement.
2. FormExpansionwithTemperatureRise1. Thermalexpansionoftheformcausing
frictionforcesbetweentheelementandtheform,leadingtoabuild-upofstressesintheelement.
C. LengthenSetTime-InAccordancewithASTMC4031. Minimizetemperaturedifferentialbetween
elementandform2. Preventrapidcool-downoftheelement
D. HandlingStresses
1. Highstressesduetoinadequatenumberofpickpointsorpickpointlocations.
2. Removalfromformpriortoreachingsufficientstrippingstrength.
3. Elementbindinginformsorhighsuctionforcesduringremovalfromform.
4. Unevendunnage.
3. ImproveHandlingMethods1. Checkliftingandhandlingstressesaccordingto
thePCIDesignManual.2. Verifyconcretestrengthpriortostripping.3. Adjustcalculationsforstripping.Mayleadto
higherstrippingstrengthrequirement.4. Checkelevationandseatingofdunnage.If
supportedbymorethantwopoints,checkforgapsinseatingpoints.Avoidstackingelementsontopofeachotherunlessdunnageissupportedwell(concreteslab).
Note:Modificationstomixdesignsmaynotbepossible
incertainsituationsduetoownerpre-qualificationrequirementsformixes.
45
TS#SS2:TROUBLESHOOTINGFORCRACKSINNON-PRESTRESSEDPRECASTELEMENTSDescription Thesecracksaretypicallyperpendiculartothelongitudinalaxisoftheelementandextend
acrossthemember,oftenvisibleonmultiplefaces.
ENGINEERINGEFFECTS REPAIRCONSIDERATIONS1. Thedesignanddetailingofreinforcementin
theelementshouldbecheckedinaccordancewithAASHTOtemperatureandshrinkageprovisions.
2. Anassessmentoftheneedtorepairaswellasenvironmentalexposurewillberequired.ItshouldbenotedthatAASHTOprovisionsarebasedonanassumedcrackwidthof0.017-in.withClass1Exposureand0.013-in.forClass2Exposure.Class1Exposureappliestoconditionswhencrackscanbetoleratedduetoreducedconcernsofappearanceand/orcorrosion.Class2Exposureappliestowhenthereisincreasedconcernofappearanceand/orcorrosion.
3. ACICommittee224report“ControlofCrackinginConcreteStructures”statesthattolerablecrackwidthsare0.006-in.forconcreteexposedtoseawaterspraywithwettinganddrying,0.007-in.forconcreteexposedtode-icingchemicals,and0.012-in.forconcreteexposedtohumidity.
1. Minorcracksthatareincorporatedintoconcreteclosurepoursorgroutedjointsneednotberepaired.
2. Ifthedecisionismadethatrepairsarewarranted,thecracksshouldbeepoxyinjected,inaccordancewithStandardRepairProcedure#10.
3. Experiencehasshownthatcracksasnarrowas0.002-in.canbeinjectedsuccessfully.However,thesurfaceofcracksnarrowerthan0.006-inchesshouldbesealed.SeeStandardRepairProcedure#14.
46
TS#SS3:TROUBLESHOOTINGFORHONEYCOMBING,VOIDS,POURLINES,ANDMINOR
SURFACEIMPERFECTIONSINNON-PRESTRESSEDPRECASTELEMENTSDescription Missingvolumeofcementpastefromaroundaggregateorvoidscontainingneitherpaste
noraggregate.Apourlineisadiscolorationofthesurfaceconcretebetweenadjacentconcreteplacements.Itisnotacoldjoint,wheretheearlierconcretehassetpriortoplacementofthelatterconcrete.
ThefollowingelementsarecoveredunderthisTroubleShootingGuide:PierElements(columns,caps),AbutmentandWallElements(stems,caps),Foundationelements(footings),orothersimilarnon-prestressedprecastelements.
CAUSE PREVENTIONA. Production
1. Inadequatevibration2. Improperplacementofconcrete3. Shifted/misplacedrebarcage
A. ImproveProductionMethods1. Providethoroughinternalvibrationand,
wherewarranted,externalvibration.2. Startplacementawayfrombulkheadsand
usevibrationtocausetheconcretetoflowtowardbulkheads.
3. Verifythatreinforcingissecuredintheformsandlocatedcorrectly.
B. ConcreteMixDesign1. Inadequatemixing2. Mixtoostiff3. Earlysetinplasticizedconcrete4. Delayedplacementofconcrete5. Flashsetofconcreteinforms6. Excessiveaggregatesize,gapgrading,or
detrimentalshape
B. AdjustMixDesign1. Mixconcretethoroughly2. Adjustmixoradditivedosagerates:(add
plasticizers,reduceaggregatesize,adjustself-consolidatingadditivedose,etc.).
3. Improvedeliverytimeoftheconcrete4. Improvedeliverytimeoftheconcrete5. Coolformspriortoconcreteplacement6. Considerusingsmallerand/ordifferent
typeofaggregate.
C. DesignDetails1. Congestedreinforcing.
C. ImproveDetails1. Reducereinforcementcongestiontothe
extentpossibleProvideclearspacingbetweenreinforcementlargerthan1½timesthemaximumaggregatesize
47
TS#SS3:TROUBLESHOOTINGFORHONEYCOMBING,VOIDS,POURLINES,ANDMINOR
SURFACEIMPERFECTIONSINNON-PRESTRESSEDPRECASTELEMENTSDescription–Missingvolumeofcementpastefromaroundaggregateorvoidscontainingneitherpaste
noraggregate.Apourlineisadiscolorationofthesurfaceconcretebetweenadjacentconcreteplacements.Itisnotacoldjoint,wheretheearlierconcretehassetpriortoplacementofthelatterconcrete.
ENGINEERINGEFFECTS REPAIRCONSIDERATIONS1. Honeycombingandvoidscanaffectshear,
bendingandaxialcapacityandmustberepaired.
2. Wheretheareaistobeencasedinacast-in-placeconcreteoragroutedjoint,thehoneycombingwillnotaffectdurability.Removaloflooseaggregateandconcretepriortothepourwillbeasufficientrepairinmostcases.
1. Wheretheareaistobeexposedinthefinalcondition,considermatchingthecolorofthepatchwiththeelement.
2. Ifaestheticsarenotaconsideration,therepairofapourlineisnotnecessary,otherwisethesurfacefinishshouldrepairedbyrubbing,bagging,ordressed(similartoexposedcast-in-placeconcrete).
3. Forotherconditions,repairusingStandardRepairProcedures#5or#9,asappropriate.
48
TS#SS4:TROUBLESHOOTINGSHORTPROJECTEDREBARANDMISSINGPROJECTED
REBARINNON-PRESTRESSEDPRECASTELEMENTSDescription Thisconsistsalackof,orshortprojectingreinforcing.
ThefollowingelementsarecoveredunderthisTroubleShootingGuide:PierElements(columns,caps),AbutmentandWallElements(stems,caps),Foundationelements(footings),orothersimilarnon-prestressedprecastelements.
CAUSE PREVENTIONA. Formwork
1. Bulkheadshift
A. ImproveProductionMethods1. Checkbulkheadlocationsandintegrity
B. ReinforcementProduction1. Improperplacement2. Impropercutting3. Improperbending4. Incorrectfabricationdrawingordesign
drawing5. Shiftingduringcasting6. Improperhandling
B. ImproveProductionMethods1. Re-checkrebarlocationspriortoconcrete
placement2. Re-checkrebarlengthsbeforecutting3. FollowCRSIrequirementsforminimum
bendingradius4. Re-checkfabricationanddesigndrawings5. Placeadditionaltiesonreinforcement6. Reviewshophandlingpractices
49
TS#SS4:TROUBLESHOOTINGSHORTPROJECTEDREBARANDMISSINGPROJECTEDREBARINNON-PRESTRESSEDPRECASTELEMENTS
Description–Thisconsistsalackof,orshortprojectingreinforcing.
MissingExternalProjectedRebarwithCorrespondingInternalBarPresent1. DrillandGroutNewExternalBar• EachmissingexternalprojectingrebarshallbereplacedbyanequivalentsizedGrade60rebar.A
newbarcanbeinstalledbydrillingandgroutinganewbarusingRepairProcedure#12.Theembedmentshallbesufficienttodevelopafulllapsplicewiththeinternalreinforcingwheretensiontransferisrequired.
• Theminimumembedmentforothersituationsshallbebasedonthechemicaladhesivemanufacturer’srecommendations.SeeStandardRepairProcedure#12
• Notethatthisrepairproceduremaynotbeacceptableiftheprojectingbaristobesplicedwithamechanicalcouplerintheadjacentelementduetopotentialalignmentissues.
ShortProjectingRebar1. UseamechanicalcouplerthatisapprovedbytheOwner.Partialremovaloftheconcrete
surroundingthebarmayberequiredinordertoattachthecoupler.Useacouplerthatcandevelopatleast125%oftheminimumspecifiedyieldstrengthofthebar.Forseismicconnections,thecouplermayneedtodevelop100%oftheminimumspecifiedtensilestrengthofthebar.
2. Installbarextensionusingcouplermanufacturer’srecommendations.SeeStandardRepairProcedure#11.
3. Ifpartialremovalofconcreteisrequired,twooptionscanbefollowed:• Iftheremovedconcreteareaiswithinaclosurepourorgroutedjointinthecompleted
structure,norepairoftheremovedconcreteisrequired.• Iftheremovedconcreteiswithintheexposedareaofconcreteinthecompletedstructure,
repairtheareausingRepairProcedure#6.
ENGINEERINGEFFECTS REPAIRCONSIDERATIONSRepairsshallnotbemadewithoutthedesigner’sapproval;thefollowingaregeneralguidelines:1. Missingprojectingreinforcementcanmateriallyaffectthedesign
oftheadjacentconnection.Ifcalculationsverifynosignificantreductionincapacity,arepairmaynotbenecessary.Ifthebarismissingwithintheelement,anengineeringassessmentoftheelementisinorder.Ifthebarisrequiredforthedesign,thenrejectionoftheelementisinorder.
2. Forbarsthataretobeinsertedintogroutedsleeves,specialcareshouldbetakentoensurethattherepairedbarwillproperlyalignwiththecoupler.
SeeBelow:
50
TS#SS5:TROUBLESHOOTINGMISSINGORMIS-LOCATEDINSERTS,VOIDS,ORMIS-LOCATEDPROJECTINGREBARINNON-PRESTRESSEDPRECASTELEMENTSDescription Thistypeofdefectconsistsofmissingormis-locatedvoidsandhardware,andmis- locatedrebar.
ThefollowingelementsarecoveredunderthisTroubleShootingGuide:PierElements(columns,caps),AbutmentandWallElements(stems,caps),Foundationelements(footings),orothersimilarnon-prestressedprecastelements.
CAUSE PREVENTIONA. ProductionOversight
1. Bulkheadortemplateshift
A. ImproveProductionMethods1. Checkbulkheadlocationsandintegrity
B. ReinforcementProduction1. Improperplacement2. Incorrectfabricationdrawingordesign
drawing3. Shiftingduringcasting
B. ImproveProductionMethods1. Re-checkrebarandvoidlocationspriorto
concreteplacement2. Re-checkfabricationanddesigndrawings3. Placeadditionaltiesonreinforcement
51
TS#SS5:TROUBLESHOOTINGMISSINGORMIS-LOCATEDINSERTS,VOIDS,ORMIS-LOCATEDPROJECTINGREBARINNON-PRESTRESSEDPRECASTELEMENTS
Description Thistypeofdefectconsistsofmissingormis-locatedvoidsandhardware,andmis- locatedrebar.
ENGINEERINGEFFECTS REPAIRCONSIDERATIONS1. Repairsshallnotbemadewithoutthe
designer’sapproval;thefollowingaregeneralguidelines:
2. Mis-locatedreinforcementorinsertsmayleadtoimproperfit-up.Lossofthebarconnectioncanmateriallyaffectthedesignoftheadjacentconnection.Ifcalculationsverifythatthereisnosignificantreductionincapacityoftheconnection,arepairmaynotbenecessary.
3. Iftheadjacentelementhasnotyetbeencast,as-builtdimensionsmaybeappliedtotheshopdrawingsforthesubsequentelementprovidedthatthevariationdoesnotaffecttherequiredstructuralcapacityoftheconnection.
Theminimumembedmentforothersituationsshallbebasedonthechemicaladhesivemanufacturer’srecommendations.SeeStandardRepairProcedure#12
1. Ifmis-locatedinsertsandbarscannotbeeliminatedasstatedinItem1totheleft,considerdrillingandgroutinganewbarinthecorrectlocation,usingStandardRepairProcedure#12.ThenewprojectingrebarshallbeanequivalentsizedGrade60rebar.Theembedmentshallbesufficienttodevelopafulllapsplicewiththeinternalreinforcingwheretensiontransferisrequired.Ifthemis-locatedrebarlocationresultsininsufficientconcretecover,alternatecorrosionprotectionstrategiesshouldbeconsideredsuchassealersorinstallationofpassivecathodicdevices.
52
Section2.3:PrecastFullDepthDeckPanelsThereare several different typesofdetails used forprecast full-depthdeckpanels. Commondetailsinclude:
1. Fulldepthshearconnectorpockets2. Partialdepth(hidden)shearconnectorpockets3. Projectingreinforcingusedforconnections4. Panelswithpost-tensionedconnections
The graphics contained herein show several different types of details depending on theapplicabletroubleshootingguideline.
Ingeneral,thenon-conformancesnotedinthissectionareapplicabletopanelsthatareprecastorprestressed.Non-conformancesthatareonlyapplicabletoprestressedpanelsaresonoted.
TS#FDDP1:CornerSpallsTS#FDDP2:CracksTS#FDDP3:TransverseCracksTS#FDDP4:Honeycombing,Voids,andMinorSurfaceImperfectionsTS#FDDP5:ShortProjectedReinforcingandMissingProjectedReinforcingTS#FDDP6:MissingorMislocatedInserts,Voids,DuctsorMislocatedProjectingReinforcing
53
TS#FDDP1:TROUBLESHOOTINGCORNERSPALLSINPRECASTFULL-DEPTHDECKPANELSDescription Thesespallsandcracksmaybefoundatanyedgeorcorneroftheelement
Note: Thistroubleshootingguideisapplicabletobothprecastandprestressedfull- depthdeckpanels
CAUSE PREVENTIONA. Design
1. Inadequateedgereinforcement
A. VerifyDesign1. Provideproperreinforcementascloseto
edgesasclearancerequirementsallow
B. ImproperHandling1. Impactingedges2. Unevendunnage
B. CareinHandling1. Ensureadequateroomfortransportof
elements2. Provideuniformdunnage.Non-rigid
materialssuchastimberorelastomericpadsarerecommended
C. Production1. Bindinginformsduringstripping2. Indentationinforms3. Insertshangingupinforms4. Thermalexpansionofformspriorto
concretesetting5. Bleedingofconcreteunderheader
C. ImproveProductionMethods1. Keepformscleanandwelloiled2. Keepformsingoodcondition(repair
dents,removeprojections,andmakeseamsmortartight)
3. Ensureinsertsarefreeduringstripping4. Ensureinitialconcretesetpriortostart
ofcuring5. Providemortar-tightheader
Note:Onetypeofdeckpanelshown,otherssimilar
54
TS#FDDP1:TROUBLESHOOTINGCORNERSPALLSINPRECASTFULL-DEPTHDECKPANELSDescription Thesespallsandcracksmaybefoundatanyedgeorcorneroftheelement
ENGINEERINGEFFECTS REPAIRCONSIDERATIONS1. Spallsinareasoffull-depthdeckpanelsthat
areexposedtotheenvironmentinthefinishedbridgeshouldberepaired.
2. Minorspallsthatdonotcompromiseprotectionofreinforcingfromwater,saltspray,excessivehumidity,orarenotexposedtodirectviewneednotberepaired.Forexample:spallsincorporatedintoconcreteclosurepoursorgroutedjoints.
1. Crackslocatednearcornershavethepotentialtobecomeaspallandshouldberepairedafterremovalofcrackedconcrete.
2. Wherecornerspallsaredeemedinneedofrepair,therepairsshouldbemadeinaccordancewithStandardRepairProcedure#15.
Note:Onetypeofdeckpanelshown,otherssimilar
55
TS#FDDP2:TROUBLESHOOTINGFORCRACKSINFULL-DEPTHPRECASTDECKPANELSDescription Thesecracksaretypicallyperpendiculartotheaxisoftheelementandextendpartiallyor
entirelyacrossthemember,oftenvisibleonmultiplefaces.Othercracksshownbelowalsoapply.
Note: Thistroubleshootingguideisapplicabletoprecastpanelsdesignedwithmildreinforcingorpanelswithminoramountsofprestressingforhandling.Panelsdesignedwithprestressingforstrengthshouldbetreatedsimilartoaprestressedbeam.
CAUSE PREVENTIONA. Design1. Inadequatetemperatureandshrinkage
reinforcement
A. VerifyDesign1. Verifythatthereisadequatetemperatureand
shrinkagereinforcementandthatthereinforcementisproperlydistributedwithintheelement
B. Shrinkage1. Shrinkageofconcreteduringcuringcauses
frictionforcesbetweentheelementandtheform,leadingtothebuild-upofstressesintheelement
A. Reviewormodifythemixormodifycuringmethodstoreduceshrinkage
1. Considerchangetoalternatemix(seenote2)2. Applycuringcoversrapidly
B. Production/Formwork1. Thermalexpansionoftheformcausing
frictionforcesbetweentheelementandtheform,leadingtoabuild-upofstressesintheelement
2. Concretebindingtoforms3. Indentationsorjointoffsetsinforms4. Insertsinformsanchoredorrestrainedby
forms
A. ImproveProductionmethods1. Preventrapidcool-downoftheelement2. Keepformsingoodcondition;fabricateforms
withevensmoothjoints3. Keepformscleanandproperlyoiled4. Releaserestraintofallinsertsafterinitialset
C. HandlingStresses1. Highstressesduetoinadequatenumberof
pickpointsorpickpointlocations2. Removalfromformpriortoreaching
sufficientstrippingstrength3. Elementbindinginformsorhighsuction
forcesduringremovalfromform4. Unevendunnage
B. ImproveHandlingMethods1. Checkliftingandhandlingstressesaccordingto
thePCIDesignManual2. Verifyconcretestrengthpriortostripping.3. Adjustcalculationsforstripping.Mayleadto
higherstrippingstrengthrequirement4. Checkelevationandseatingofdunnage.If
supportedbymorethantwopoints,checkforgapsinseatingpoints.Avoidstackingelementsontopofeachotherunlessdunnageissupportedwell(concreteslab)
Notes:1.Onetypeofdeckpanelshown,otherssimilar2.Modificationstomixdesignsmaynotbepossibleincertainsituationsduetoownerpre-qualificationrequirementsformixes.
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TS#FDDP2:TROUBLESHOOTINGFORCRACKSINFULL-DEPTHPRECASTDECKPANELSDescription Thesecracksaretypicallyperpendiculartotheaxisoftheelementandextendpartiallyor
entirelyacrossthemember,oftenvisibleonmultiplefaces.
ENGINEERINGEFFECTS REPAIRCONSIDERATIONS1. Thedesignanddetailingofreinforcementin
theelementshouldbecheckedinaccordancewithAASHTOtemperatureandshrinkageprovisions.
2. Anassessmentoftheneedtorepairaswellasenvironmentalexposurewillberequired.ItshouldbenotedthatAASHTOprovisionsarebasedonanassumedcrackwidthof0.017-in.withClass1Exposureand0.013-in.forClass2Exposure.Class1Exposureappliestoconditionswhencrackscanbetoleratedduetoreducedconcernsofappearanceand/orcorrosion.Class2Exposureappliestoanincreasedconcernofappearanceand/orcorrosion.
3. ACICommittee224report“ControlofCrackinginConcreteStructures”statesthattolerablecrackwidthsare0.006-in.forconcreteexposedtoseawaterspraywithwettinganddrying,0.007-in.forconcreteexposedtode-icingchemicals,and0.012-in.forconcreteexposedtohumidity.
4. Minorcracksthatareincorporatedintoconcreteclosurepoursorgroutedjointsneednotberepaired.
1. Ifthedecisionismadethatrepairsarewarranted,thecracksshouldbeepoxyinjectedinaccordancewithStandardRepairProcedure#10.
2. Experiencehasshownthatcracksasnarrowas0.002-in.canbeinjectedsuccessfully.However,thesurfaceofcracksnarrowerthan0.006-inchesshouldbesealed.SeeStandardRepairProcedure#14.
Note:Onetypeofdeckpanelshown,otherssimilar
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TS#FDDP3:TROUBLESHOOTINGFORTRANSVERSECRACKSINPRESTRESSEDFULL-
DEPTHDECKPANELSDescription Thesecracksaretypicallyperpendiculartothelongitudinalaxisoftheelementandextend
partiallyorentirelyacrossthemember,oftenvisibleonmultiplefaces.
Notes: Thistroubleshootingguideisapplicabletotransversecracksinprecastfull-depthdeckpanelswithprestressingforhandlingrunningperpendiculartothecracks.Panelswithprestressingforstrengthshouldbetreatedsimilartoaprestressedbeam.Forothercracksinprestresseddeckpanels,seeTS#FDDP2.
CAUSE PREVENTIONA. BondofStrand/StrandSlip1. StrandContamination2. Insufficientvibrationofconcrete
A. Ensureagainstunintendedstrandslip1. Inspectstrandforcleanlinessandabsenceof
lubricantsafterstressingandpriortocasting2. Useinternalandexternalvibrationincongested
endsofpanelsB. Shrinkagepriortodetensioning5. Shrinkageofconcreteduringcuringcausing
frictionforcesbetweentheelementandtheform,leadingtoabuild-upofstressesintheelement
B. Improveproductionmethods1. Applycoversrapidlyafterconcretepours2. Detensionascoversareremoved3. Preventexposedstrandfromcoolingdifferentially
withrespecttothepanel4. Adjustconcretemixbyreducingcement,adding
pozzolansorchangingaggregategradation5. Provideuniformheatandhumidity
C. DetensioningProcedure1. Lowreleasestrength2. Improperdetensioning
sequence/procedures
C. Useproperdetensioningprocedure1. Ensureproperconcretestrengthpriortorelease2. Keepprestressedforcesbalancedwhile
detensioning,usinganestablishedprocedure
D. Formwork1. Indentationsorjointoffsetsinforms2. Concretebindingtoforms
D. Inspectformconditionpriortocasting1. Ensuresmoothformalignment2. Oilformsthoroughly
E. Incorrectprestressforce1. Inadequateprestressstrandindesign2. Under-estimationofprestresslosses3. Under-tensioningofstrand4. Incorrectnumberofstrandinbed
E. Applycorrectprestressforce1. Checkdesigncalculationsandshopdrawings2. Recomputelosses3. Comparemeasuredelongationofstrandwith
computedelongation
Note:Onetypeofdeckpanelshown,otherssimilar
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TS#FDDP3:TROUBLESHOOTINGFORTRANSVERSECRACKSINPRESTRESSEDFULL-
DEPTHDECKPANELSDescription Thesecracksaretypicallyperpendiculartothelongitudinalaxisoftheelementandextend
partiallyorentirelyacrossthemember,oftenvisibleonmultiplefaces.ENGINEERINGEFFECTS REPAIRCONSIDERATIONS1. Forverticalcracksthatinterceptbonded
ordebondedstrandwithintheirrespectivetransferlengths,itisrecommendedthattheengineerre-computethemomentandshearcapacitybasedontransferinitiatingatthepointofthecrack.Ifthere-computedcapacitiesareacceptablethepanelcanberepaired.Thesecracksshouldbeinjected.
2. Verticalcracksthatinterceptbondedordebondedstrandbeyondtheirrespectivetransferlengthsandwithawidthlessthan0.006-in.afterdetensioning,neednore-evaluation.Cracks0.006-in.orgreaterinwidthshouldbeevaluatedtoaffirmadequateprestress.
3. Verticalcracksatanylocationonthepanelthatdonotinterceptstrandneednoevaluationbytheengineer.
1. Itisrecommendedthatcracksnotberepairedpriortodetensioningasrepairswillmaskthecauseandseriousnessofthecrack
2. Allcrackslessthan0.006-in.inwidth,afterdetensioninganddeemedacceptable,shouldbesealed.SeeStandardRepairProcedure#14.Ifthesecracksarewithinthetransferzone,anepoxyinjectionrepairshouldbeconsidered(seeItem3below).
3. Allcracks0.006-in.orgreaterinwidth,afterdetensioninganddeemedacceptable,shouldberepairedbyepoxyinjectioninaccordancewithStandardRepairProcedure#10.
Note:Onetypeofdeckpanelshown,otherssimilar
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TS#FDDP4:TROUBLESHOOTINGFORHONEYCOMBING,VOIDS,ANDMINORSURFACE IMPERFECTIONSINPRECASTFULL-DEPTHDECKPANELSDescription Missingvolumeofcementpastefromaroundaggregateorvoidscontainingneitherpaste
noraggregate.
CAUSE PREVENTIONA. DesignDetails6. Congestedreinforcing
A. ImproveDetails1. Reducereinforcementcongestiontothe
extentpossibleProvideclearspacingbetweenreinforcementlargerthan1½timesthemaximumaggregatesize
B. Production1. Inadequatevibration2. Improperplacementofconcrete3. Shifted/misplacedreinforcing
B. ImproveProductionMethods1. Providethoroughinternalvibrationand,
wherewarranted,externalvibration2. Startplacementawayfrombulkheadsand
usevibrationtocausetheconcretetoflowtowardbulkheads
3. Verifythatreinforcingissecuredintheformsandlocatedcorrectly
C. ConcreteMixDesign1. Inadequatemixing2. Mixtoostiff3. Earlysetinplasticizedconcrete4. Delayedplacementofconcrete5. Flashsetofconcreteinforms6. Excessiveaggregatesize,gapgrading,or
detrimentalshape
C. AdjustMix1. Mixconcretethoroughly2. Adjustmixoradditivedosagerates:(add
plasticizers,reduceaggregatesize,adjustself-consolidatingadditivedose,etc.)
3. Improvedeliverytimeoftheconcretelformspriortoconcreteplacement
4. Considerusingsmallerand/ordifferenttypeofaggregate
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TS#FDDP4:TROUBLESHOOTINGFORHONEYCOMBING,VOIDS,ANDMINORSURFACE IMPERFECTIONSINPRECASTFULL-DEPTHDECKPANELSDescription Missingvolumeofcementpastefromaroundaggregateorvoidscontainingneitherpaste
noraggregate.
ENGINEERINGEFFECTS REPAIRCONSIDERATIONS1. Wheretheareaistobeencasedinacast-in-
placeconcreteoragroutedjoint,thehoneycombingwillnotaffectdurability.Removaloflooseaggregateandconcretepriortothepourwillbeasufficientrepairinmostcases.
1. Forotherconditions,repairusingStandardRepairProcedures#5or#9,asappropriate.
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TS#FDDP5: TROUBLESHOOTINGSHORTPROJECTEDREINFORCINGANDMISSING
PROJECTEDREINFORCINGINPRECASTFULL-DEPTHDECKPANELS
Description Thisconsistsofalackoforshortprojectingreinforcing.
CAUSE PREVENTIONA. Formwork1. Bulkheadshift
A. ImproveProductionMethods1. Checkbulkheadlocationsandintegrity2. Reviewqualitycontrolproceduresforpre-
pourandadjustasneeded
B. ReinforcementProduction1. Improperplacement2. Impropercutting3. Improperbending4. Incorrectfabricationdrawingordesign
drawing5. Shiftingduringcasting6. Improperhandling
B. ImproveProductionMethods1. Re-checkreinforcinglocationspriorto
concreteplacement2. Re-checkreinforcinglengthsbeforecutting3. FollowCRSIrequirementsforminimum
bendingradius4. Re-checkfabricationanddesigndrawings5. Placeadditionaltiesonreinforcement6. Reviewqualitycontrolproceduresforpre-
pourandadjustasneeded7. Reviewshophandlingpractices
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TS#FDDP5: TROUBLESHOOTINGSHORTPROJECTEDREINFORCINGANDMISSING
PROJECTEDREINFORCINGINPRECASTFULL-DEPTHDECKPANELS
Description–Thisconsistsofalackof,orshortprojectingreinforcing.
MissingExternalProjectedReinforcingwithCorrespondingInternalBarPresent1. DrillandGroutNewExternalBar• Eachmissing external projecting reinforcing shall be replaced by a bar of equivalent size and
grade. A new bar can be installed by drilling and grouting a new bar using Standard RepairProcedure#12.Theembedmentshallbesufficienttodevelopafull lapsplicewiththeinternalreinforcingwheretensiontransferisrequired.
• The minimum embedment for other situations shall be based on the chemical adhesivemanufacturer’srecommendations.SeeStandardRepairProcedure#12
• Notethatthisrepairproceduremaynotbeacceptableiftheprojectingbaristobesplicedwithamechanicalcouplerintheadjacentelementduetopotentialalignmentissues.
ShortProjectingReinforcing1. Use a mechanical coupler that is approved by the Owner. Partial removal of the concrete
surroundingthebarmayberequiredinordertoattachthecoupler.Useacouplerthatcandevelopat least 125% of theminimum specified yield strength of the bar. For seismic connections, thecouplermayneedtodevelop100%oftheminimumspecifiedtensilestrengthofthebar.
2. Install bar extension using coupler manufacturer’s recommendations. See Standard RepairProcedure#11.
3. Ifpartialremovalofconcreteisrequired,twooptionscanbefollowed:• Iftheremovedconcreteareaiswithinaclosurepourorgroutedjointinthecompletedstructure,
norepairoftheremovedconcreteisrequired.• Iftheremovedconcreteiswithintheexposedareaofconcreteinthecompletedstructure,repair
theareausingStandardRepairProcedure#6.
ENGINEERINGEFFECTS REPAIRCONSIDERATIONSRepairsshallnotbemadewithoutthedesigner’sapproval;thefollowingaregeneralguidelines:1. Missingprojectingreinforcementcanmateriallyaffectthedesign
oftheadjacentconnection.Ifcalculationsverifynosignificantreductionincapacity,arepairmaynotbenecessary.Ifthebarismissingwithintheelement,anengineeringassessmentoftheelementisinorder.Ifthebarisrequiredforthedesign,thenrejectionoftheelementisinorder.
SeeBelow:
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64
TS#FDDP6:TROUBLESHOOTINGMISSINGORMISLOCATEDINSERTS,VOIDS,DUCTSORMISLOCATEDPROJECTINGREINFORCINGINPRECASTFULL-DEPTHDECKPANELS
Description Thistypeofdefectconsistsofmissingormis-locatedvoids,ducts,hardware,andmis- locatedreinforcing.
CAUSE PREVENTIONA. ProductionOversight1. Bulkheadortemplateshift
A. ImproveProductionMethods1. Checkbulkheadlocationsandintegrity2. Reviewqualitycontrolproceduresforpre-
pourandadjustasneeded
B. ReinforcingProduction1. Improperplacement2. Incorrectfabricationdrawingordesign
drawing3. Shiftingduringcasting
B. ImproveProductionMethods1. Re-checkreinforcingandvoidlocationsprior
toconcreteplacement2. Re-checkfabricationanddesigndrawings3. Placeadditionaltiesonreinforcement
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TS#FDDP6:TROUBLESHOOTINGMISSINGORMISLOCATEDINSERTS,VOIDS,DUCTSORMISLOCATEDPROJECTINGREINFORCINGINPRECASTFULL-DEPTHDECKPANELS
Description Thistypeofdefectconsistsofmissingormis-locatedvoids,ducts,hardware,andmis- locatedreinforcing.
ENGINEERINGEFFECTS REPAIRCONSIDERATIONSRepairsshallnotbemadewithoutthedesigner’sapproval;thefollowingaregeneralguidelines:
1. Mislocated reinforcement or inserts maylead to improper fit-up. Loss of the barconnection can materially affect the designof the adjacent connection. If calculationsverifythatthereisnosignificantreductionincapacityoftheconnection,arepairmaynotbenecessary.
2. If themislocated reinforcing location resultsin insufficient concrete cover, alternatecorrosion protection strategies should beconsidered such as sealers or installation ofpassivecathodicdevices.
3. Thecontractorcanattempttodetermineifamislocated shear connector void is able toaccommodatetherequirednumberofshearconnectors. If it is feasible to install theconnectors within the misaligned void, itmaybepossibletousethepanel.
4. Ifapost-tensioningductisslightlymisaligned(beyond the specified tolerances), theContractor can attempt to determine if themisaligned duct can be properly connectedand sealed with the duct in the adjacentpanel.TheContractorshallalsodetermineifthe tendons can be installed in themisaligned duct. If the misaligned ductcannotbeused,thepanelshouldberejectedandanewpanelcast.Ifitisdeterminedthatthe misalignment is acceptable, theContractor will be responsible for anyproblemsthatariseduringinstallation.Ifthemisalignment of the duct results in aneccentricity of the tendon, a review by theEngineerisrequired.
1. If mislocated inserts and bars cannot beeliminated as stated in Item 1 to the left,considerdrillingandgroutinganewbarinthecorrect location, using Standard RepairProcedure #12. The new projectingreinforcing shall be an equivalent size andgradeofreinforcing.Theembedmentshallbesufficienttodevelopafull lapsplicewiththeinternal reinforcingwhere tension transfer isrequired.
2. The minimum embedment for othersituations shall be based on the chemicaladhesive manufacturer’s recommendations.SeeStandardRepairProcedure#12
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Section3:StandardRepairProcedures
1. ConfinedSpallsInsideBearingAreas 2. ConfinedSpallsOutsideBearingAreas 3. Non-ConfinedBearingAreaSpalls 4. SpallsandVoidsintheBottomFlangeThatExposePrestressingStrand 5. HoneycombedorVoidedWebAreas 6. DamagedFlangesRequiringRemovalandReplacementofConcrete 7. TakingCoresandPatchingCoredHolesinGirders 8. MisshapenBearingRecesses 9. HoneycombedAreasLeft-in-Place 10. EpoxyInjectionofCracks 11. ShortProjectingMildReinforcingBarsorProjectingPrestressingStrands 12. ReplacementofMissingProjectedMildSteelorPrestressingStrand 13. MissingorIncorrectlyLocatedDiaphragmInserts 14. SealingCracks
15. EdgeSpallsinPrecastElements AsuggestedreferenceforguidanceonrepairmethodsisthePCIDocumententitledManualfortheEvaluationandRepairofPrecast,PrestressedConcreteBridgeProducts[6].Thisdocumentcontainssimilarinformationasthisdocument,howeveralsocontainsachapteronMethodsofPatching.
67
STANDARDREPAIRPROCEDURE#1FORCONFINEDSPALLSINSIDEBEARINGAREAS
CASE1:NOSTRANDSEXPOSEDA. Remove all loose concrete, taking care to not damage
reinforcingorstrand.
B. Square all sides of the depression. Take care to notdamageanymildreinforcement.
C. Cleantheexcavatedareaandreinforcingwithastiffwire
brush,blowingawaydust,withhighpressureair.
D. Repair Option 1 – Fill the voided area using approvedpolymermodifiedcementitious,shrinkage-compensatedpatchingmaterial,withacompressivestrengthequaltoor greater than the specified design strength of thebeam. Prepackaged patching material is preferred tocontrolquality.Cureproperly.
E. RepairOption2–Coatsurfacetobeadheredtowithan
approvedbondingagent, followingthemanufacturer’s instructions.Fill thevoidedareawithahigh strength, cement based, shrinkage-compensated mortar, following the manufacturer’sinstructions.Cureproperly.
F. Usecaretoensurethattherepairedareadoesnotprojectbelowthebottomoftheflangenear
thebearingarea.NOTE:Withthepriorapprovaloftheowner/engineer,spallsthatinvolvenomorethan20%ofthebearingareamaybepatched,inthepresenceoftheowner’sinspectorwithoutsubmittingtherepairforformalapproval.Repairsofspallsinexcessof20%ofthebearingareawillrequiresubmissionofarepairplantotheowner/engineerforapproval.CASE2:STRANDSEXPOSEDThefullextentofstrandexposureshallbedeterminedandarepairplansubmittedforapprovalbytheowner/engineer,regardlessofthesizeofthespall,asthedesigncapacitymaybeaffected.Generally,ifthedesigncapacityisjudgedtohavenotbeendiminished,ordiminishedanacceptableamount,therepairproceduresforCase1willremainapplicable.
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STANDARDREPAIRPROCEDURE#2FORCONFINEDSPALLLSOUTSIDEBEARINGAREASCASE1:Nostrandsexposed;spalllocatedbetweentheendofthebeamandthe¼point.
A. Withthepriorapprovaloftheowner/engineer,individualspallsorcollectivemultiplespallsnotexceeding10%ofthebottomflangeplanarea,withinthedefinedlimits,mayberepairedinthepresenceoftheinspectorutilizingeitherrepairoptionspecifiedinStandardRepairProcedure#1.
B. Ifanindividualspallorcollectivemultiplespallsexceed10%ofthebottomflangeplanarea,arepairplanmustbesubmittedtotheowner/engineerforapproval.
CASE2:NoStrandsExposed:Spalllocatedbetweenthe¼pointand½pointofthebeam.
A. Withthepriorapprovaloftheowner/engineer,individualspallsorcollectivemultiplespallsnotexceeding10%ofthebottomflangeplanarea,withinthedefinedlimits,mayberepairedinthepresenceoftheinspector.TherepairoptionsdescribedinStandardRepairProcedure#1maybeused,howeveranapprovedshrinkagecompensatingpatchmaterial,withacompressivestrengthmeetingthedesignstrengthofthebeam,mustbeused.
CASE3:StrandsExposed
A. Spallslocatedanywhereonthebottomofthebeamflangethatexposesstrandsrequiressubmissionofarepairplanforapprovalbytheowner/engineer.Thefullextentofstrandexposureshouldbeidentified.Generally,ifthedesigncapacityisjudgedtohavenotbeendiminishedordiminishedanacceptableamount,therepairproceduresforCases1&2,asapplicable,maybeused.
Note:Incaseswherethepatchislocatedovervehiculartrafficorpedestrianwalkways,thepatchingmaterialmustbemechanicallyanchoredeitherbyencapsulatingexistingreinforcement,beanchoredbysupplementalreinforcement,orbyotheranchoringdevices.
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STANDARDREPAIRPROCEDURE#3FORNON-CONFINEDBEARINGAREASPALLS
A. Removealllooseconcrete.
B. Square interface with existing concrete to be incontact with the patch, to the extent practical. Takecare to not damage any mild reinforcement orprestressingstrands.
C. Cleantheexcavatedarea,blowingawaydust.
D. Repair Option 1 – Fill the spall area with approved
polymer modified cementitious, shrinkage-compensated patching material, with a compressivestrengthequaltoorgreaterthanthespecifieddesignstrengthofthebeam.Pre-packagedpatchingmaterialispreferredtocontrolquality.
E. RepairOption2–Coatsurfacetobeadheredtowith
an approved bonding agent, following themanufacturer’s instructions. Fill the spall areawith ahighstrength, cementbased, shrinkage-compensatedmortar,followingthemanufacturer’sinstructions.
F. Incaseswherethepatchis locatedovervehiculartrafficorpedestrianwalkways,thepatching
material must be mechanically anchored either by encapsulating existing reinforcement, beanchoredbysupplementalreinforcement,orbyotheranchoringdevices.
NOTE:Withthepriorapprovaloftheowner/engineer,spallsintheendregionsofthebeam,withintheboundsstatedherein,maybepatched,inthepresenceoftheowner’sinspectorwithoutsubmittingtherepairforformalapproval.Repairsofspallslargerthanshownhereinwillrequiresubmissionofarepairplantotheowner/engineerforapproval.
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STANDARDREPAIRPROCEDURE#4FORSPALLSANDVOIDSINTHEBOTTOMFLANGETHATEXPOSEPRESTRESSINGSTRANDRepairs at beam ends should be made after detensioningbecause any repairs made prior to detensioning will mostlikelyfailduetohightransferstresses.Repairs away from beam ends should be made prior todetensioningsothatprecompressionstressesare induced inthepatchmaterial.
A. Removealllooseconcrete.
B. Square interfaces with existing concrete to be incontactwiththepatch.
C. Cleantheexcavatedarea,blowingawaydust.
RepairOption1–Fillthevoidedareawithapprovedpolymer modified cementitious, shrinkage-compensated patchingmaterial, with a compressivestrengthequaltoorgreaterthanthespecifieddesignstrengthofthebeam.Prepackagedpatchingmaterialispreferredtocontrolquality.
D. RepairOption2–Coatsurfacetobeadheredtowithanapprovedbondingagent,followingthemanufacturer’sinstructions.Fillthevoidedareawithahighstrength,cementbased,shrinkage-compensatedmortar,followingthemanufacturer’sinstructions.
E. Detensioning should not occur until the patch reaches the specified compressive release
strength.
F. For largerspallsofasimilarnatureand/or involvingmorestrands,thesamerepairtechniquesmaybeemployedbutmustbesubmittedtotheowner/engineerforevaluationandapproval.
G. Forareaswithextremeexposure, silaneorothersealantsmayalsobeappliedover thepatcharea.
NOTES:
1. Incaseswherethepatchis locatedovervehiculartrafficorpedestrianwalkways,thepatchingmaterial must be mechanically anchored either by encapsulating existing reinforcement, beanchoredbysupplementalreinforcement,orbyotheranchoringdevices.
2. Thisrepairappliesonlytothosevoidswhichdonotexceed4 inches indepth,4feet in lengthandexposenomorethan2strands,andwhennomorethanonespallorvoidappearsinagivensectionof thegirder.Asection isdefinedas¼ the lengthof thegirder.No twosuchspallsorvoids shall have their closest dimensions nearer than two beamdepths apart.With the priorapproval of the owner/engineer, this repair may be made, in the presence of the owner’sinspectorwithoutsubmittingtherepairforformalapproval.
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STANDARDREPAIRPROCEDURE#5FORHONEYCOMBEDORVOIDEDWEBAREASCASE1:Nostrandexposed,butreinforcingexposed
A. Remove all loose concrete with a maximum 15 poundpneumaticchippinghammer.
B. Squareallsidesofthedepressionexceptthetopofthevoid.
Bevelthesurfaceasshowninthedetailonthissheet.
C. Cleantheexcavatedarea,blowingawaydust.
D. Repair Option 1 – Fill the voided area with an approvedmodified cementitious shrinkage compensated patchingmaterial with a compressive strength equal to or greaterthanthespecifieddesignstrengthofthebeam.Prepackagedpatchingmaterialispreferredtocontrolquality.
E. Repair Option 2 – Coat surface to be adhered with an
approved bonding agent, following the manufacturer’sinstructions.Fillthevoidedareawithahighstrength,cementbased, shrinkage-compensated mortar, following themanufacturer’sinstructions.
NOTE:Withthepriorapprovaloftheowner/engineer,individualareaswithawidth,measuredverticallynotgreaterthan20%ofthewebdepthandalength,measuredhorizontallynotgreaterthan½thewebdepthmayberepaired,inthepresenceoftheowner’sinspector,withoutformalsubmissionofarepairplanforapproval.CASE2:StrandsexposedorareasexceedingthosedefinedinCase1:
A. Itmaybepossibletoemploythesamerepairtechniquesasabove,butarepairplanthatindicatestheextentofstrandexposuremustbesubmittedtotheowner/engineerforevaluationandapproval.
SPECIALDETAILFORVERTICALPATCHING
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STANDARDREPAIRPROCEDURE#6FORDAMAGEDFLANGESREQUIRINGREMOVALANDREPLACEMENTOFCONCRETEPreferably, these repairs should be made prior to detensioning,however, this type damage can occur in handling afterdetensioning.CASE1:Thebeamwillsubsequentlybetopped with a compositestructuralslab
A. Removealllooseconcrete
B. Preserve and thoroughly clean allmild reinforcement. Ifreinforcement is epoxy coated, touch-up all damagedareas
C. Cleantheremainingconcretecontactsurfaces
D. Repair Option 1 – Re-pour the missing section with
approved polymer modified, cementitious, shrinkagecompensated patching material, with a compressive andtensile strength equal to or greater than the designstrength of the beam. Prepackaged material is preferredforqualitycontrol.
E. RepairOption2–Coatthesurfacestobeadheredtowith
anapprovedbondingagent, following themanufacturer’sinstructions. Re-pourwithconcretehavingacompressivestrength equal to or greater than the design strength ofthe beam. Moist cure in accordance with contractspecifications.
CASE 2: The beam flange is the final riding surface or will beoverlaidbyanon-structuralridingsurface.Undertheseconditionstheowner/agentshouldbeconsultedastoareasthatmayberepairedusingStandardRepairProcedures.NOTE:With prior approval of the owner/engineer, areas definedmayberepairedinthepresenceoftheowner’sinspectorwithoutformal submission of a repair plan. Larger area repairs require aformal submission of a repair plan to the owner/engineer forapproval.
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STANDARDREPAIRPROCEDURE#7FORTAKINGCORESANDPATCHINGCOREDHOLESINGIRDERSThisprocedureappliestothesamplingbycoringandthepatchingofholes.Coresmayberequiredforsituationswheretheconcretestrengthofthegirderisinquestion.
A. Obtain coresof thediameter specifiedby theowner/engineer. Theengineer shall determinethe location of the core in the member. Preference should be given to areas that will becovered with concrete in the completed structure (i.e. within cast diaphragms, top of topflanges,etc.)
B. Locateandmarkallreinforcementandprestressingstrandinthevicinityofthecore.
C. Coreholes,avoidingreinforcingsteelandprestressingstrands.
D. Coatthecoredholeswithanapprovedbondingagent.
E. Patchusinganapprovedhighstrengthnon-shrinkorpolymermodified,cementitiousshrinkage
compensated prepackage patching material in accordance with the manufacture’srecommendations.
F. Allworkmustbewitnessedbytheowner’sinspector.
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STANDARDREPAIRPROCEDURE#8FORMISSHAPENBEARINGRECESSESThisrepairappliestothosebearingrecessesthatareconcave,convex,slopinginthewrongdirectionordimensionallyoutoftolerance.
A. Chip out surface to achieve correct profile or to intentionally roughen to accept patchingmaterial.
B. Cleanbearingrecessofallunsoundmaterial.
C. Applyasolutionofwaterandlatexorotherapprovedbondingagenttotheareatobefilled.
D. Mixamortarconsistingof5partsNo.70silicasandand4partscementwithlatexandwaterto
a dry consistency. (For more information on dry consistency, see Section 4) Use of a highstrength,non-shrinkgroutisalsoacceptable.
E. Applythismortarmixtoproducethespecifiedrecessdimensions.
F. Re-checkthebearingsurface,toensurethatalldimensionaltolerancesaresatisfiedassetforth
inowner’sStandardSpecifications.
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STANDARDREPAIRPROCEDURE#9FORHONEYCOMBEDAREASLEFT-IN-PLACENOTE:Repairprocedures#1through#5coverspallsandvoids. They are equally applicablewhere it isdeemedappropriatetoremove honeycombed constituents and fill the voids with cementitiousmaterials used for patching. Inmany cases it is desirable to repair honeycombed areas by filling thevoidswithpressureinjectedepoxyresinbinders.
A. Chipout½to1inchoftheexposedfaceofhoneycombedarea.
B. Apply a seal coat of polymer modified cementitiousshrinkage-compensated patching material, having acompressive strength equal to or greater than the designstrengthofthebeam.
C. Insert injection tubes through the freshly applied seal coat
such that the tubes penetrate beyond the coating into thehoneycombedarea(asanalternatetoBandC, inserttubesthrough hole drilled into hardened seal coat and then sealtheannularspacebetweenholesandtubes.)
D. InjectlowviscosityepoxyorPortlandcementgroutintothe
honeycombed area, using successive port-to-port injectionmethods,startingatthelowesttubelocation,takingcarenottoentrapairpockets
E. Pinchofftubesasinjectionofitspartiscompleted.
NOTE:UseofPortlandcementgroutisequallyacceptabletoepoxyforfillingthevoids.NOTE:Withpriorapprovaloftheowner/engineer,honeycombedvoidswithinthelimitationsdescribed
in standard repairprocedures#1 through#5maybe injectedwithapprovedepoxymaterialorPortland cement grout, in the presence of the owner’s inspector. For areas greater than thelimitationsinprocedures#1through#5,formalsubmissionofrepairproceduresarerequired.
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STANDARDREPAIRPROCEDURE#10FOREPOXYINJECTIONOFCRACKSThis procedure applies to cracks that occur in the precastmemberwithacrackwidthgreaterthan0.006inches.All workmen engaged in the injection process shall havesatisfactorily completed a program of instruction in thespecificepoxyinjectionprocesstobeused.The specific epoxy resin adhesive usedmust be approvedbytheowner/engineer.Surfacesealmaterial,usedtoconfinetheinjected adhesive, must have adequate strength to hold anyinjection fittings firmly in place and to resist injectionpressuresandpreventleakage.Epoxy components shall be mixed in accordance with themanufacturer’srecommendationsandexpendedordiscardedinaccordancewiththemanufacturer’sdesignatedpotlife.Injection equipment used must be capable of delivering thepressureappropriatefortheinjectionrequirements.CASE1:Cracksaccessibleandvisiblefrombothsides
A. Prepare areas adjacent to the crack, cleaning away dirt, dust, grease, oil and other foreignmatterdetrimentaltothebondingoftheinjectionsurfacesealsystem.Corrosivesshouldnotbeusedforcleaning.
B. For cracks of sufficient width to permit entry of loose particles, blow out debris using highpressureairequipmentcapableoffilteringoutanyoilsfromthecompressor.
C. Applyanappropriatesurfaceseal,tobothsidesofthecrack,allowingsufficientcuringtime.
D. Installinjectionportsatintervalsnotlessthaneightinches.(Note:Themaximumportspacingisafunctionofcrackwidthandpumppressureandreliesonjudgementandinjectionequipmentused).
E. For essentially horizontal cracks, begin at either end of the crack. For cracks exhibiting any
verticality inorientation,startat the lowestport.Beginandcontinue injectingepoxyuntil theadhesivereachesthenextport.
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STANDARDREPAIRPROCEDURE#10FOREPOXYINJECTIONOFCRACKS(CONTINUED)
F. Clamp or otherwise seal off the port and begin injecting through the next port. Do not skip
successiveports, inordertoavoidentrapmentofairwhichwillpreventcompletefillingofthecrack.
G. Performtheinjectionprocedurecontinuouslyuntiltheentirecrackisfilled.Ifport-to-porttravel
oftheadhesiveisnotindicated,immediatelyceaseinjectionandnotifytheengineer.Determinethecauseofproblembeforecontinuing.
H. Wheninjectioniscomplete,allowtheadhesivetocurethelengthoftimeandmannerspecified
bythemanufacturer.
I. Remove the surface seal by grinding so that the face of the crack is flush with the adjacentconcretesurfaces,withnodepressionsattheentryports.
J. Ifthefacesofthebeamarenottobesubsequentlytexturecoated,applyacolor-matchingsand
andcementmix.CASE2:BlindCracks,NotVisibleorAccessibleFromBothSides
Use the same procedures described in Case 1 with the exception that port spacing shall notexceedthethicknessofthememberforthroughcracks.(Examplesarecracksthroughtheweborflangesofboxbeams.)
NOTE: Sample cores of completed injections may be needed to verify the effectiveness of the
proceduresusedinbothCase1and2.Allworkshouldbeaccomplishedinthepresenceoftheowner’sinspector.
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STANDARDREPAIRPROCEDURE#11FORSHORTPROJECTINGMILDREINFORCINGBARSORPROJECTINGPRESTRESSINGSTRANDSCASE1:BrokenorShortMildSteelReinforcementusedasStirrupsorEndProjections
A. MechanicalCouplerAn approved coupler may be used, provided enough bar projection remains to install thecoupler.Thecouplershallbeinstalledaccordingtothemanufacturer’srecommendations.
B. Welding
Asanalternativetoacoupler,weldingmaybeconsidered.Fornormallynon-weldablegradesofreinforcing,suchasASTMA615,weldingofthesteelshouldbeapproachedwithcautionsinceno specific provisions have been included in the particular ASTM specification to enhanceweldability.Whennominallynon-weldablesteel is tobewelded,aweldingproceduresuitablefor the chemical composition and intended use of the barmust be prepared. The use of thelatesteditionofANSI/AWSD1.4isrecommended.Forweldablegradesofmildreinforcement,useofANSI/AWSD1.4negatestheneedforaseparateweldprocedure.
Butt weld the additional segment to achieve the plans projection. All welding must be inconformance with AWS welding procedures for reinforcing steel. Bar preheat should bedetermined from the carbon content and carbon equivalent (Determined from millcertifications).Weldinggroundmustbeplaceddirectlyonthereinforcingbarbeingweldedandimmediatelyadjacenttotheweld.Groundingthroughthegirderisstrictlyprohibited.
Allworkistobewitnessedbytheowner’sinspector.
CASE2:BrokenorShortPrestressingStrandEndProjections
A. Selectaproprietarystrandcouplingdevicecapableofreachingorexceedingtheyieldstrengthoftheprestressingstrand.
B. Cutoffstrandtoalengthappropriateforsplicingandjointheadditionallengthstrandrequired.
NOTE:Asanalternate to the repairsoutlined inCase1and2, itmaybeacceptable todrillandgroutreplacementbarorstrand.SeeStandardRepairProcedure#12.
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STANDARDREPAIRPROCEDURE#12FORREPLACEMENTOFMISSINGPROJECTEDMILDSTEELORPRESTRESSINGSTRANDNOTE:Unlessotherwiserequiredbytheowner/engineertosatisfydesignrequirements,thefollowing
procedureisdeemedacceptable.
A. Drilltheholediametertotheoversizedimensionsuggestedbythechemicaladhesivemanufacturer’srecommendation,accountingfortheupsetlugs.RefertotheTroubleshootingGuide#10fortherequireddepthofthehole.Theholeshallbeaminimumof3”fromanybeamedge,measuredfromtothecenterlineofthebar.
B. Afterdrillingthehole,blowoutanyresidueusingfilteredcompressedair.
C. Packtheholewithchemicaladhesiveoftheproperviscosityasrecommendedbythe
manufactureroftheadhesive,whichdependsontheorientationofthehole.
D. Rotateandpushthebarorstrandintotheholeuntilseatedatthebottom.Donotdrivethebarwithpercussiontools.
E. Thechemicaladhesiveshallbeontheowner/engineerapprovedproductslist,forthe
applicationintended,orotherwisesubmittedforapprovalpriortouse.
F. Allworkshouldbewitnessedbytheowner’sinspector.
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STANDARDREPAIRPROCEDURE#13FORMISSINGORINCORRECTLYLOCATEDDIAPHRAGMINSERTS
A. Drillhole¼-inchgreaterthanthenominaldiameterofthebar.Thedepthofholeshouldbe1-inchlessthanstemwidth.
B. Fillholewithnon-sagchemicaladhesivefollowingmanufacturer’sinstructions.
C. Insert rebar and maintain in position until the chemical adhesive cures per manufacturer’s
instructions.NOTE: The path of the deflected strand should be determined and marked along the web prior to
drilling.
SECTION
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STANDARDREPAIRPROCEDURE#14FORSEALINGCRACKSCRACKSONHORIZONTALSURFACESNOTE:This repairprocedureaddressessealingcracksonhorizontal surfaceswitha lowmodulus,high
molecularweightmethacrylatepenetratingsealerandcrackfiller.
A. FollowtheManufacturer’srecommendationsfortheapplicationofthematerial.
B. Thespecificmethacrylatesealermaterialshallbeapprovedbytheowner/engineer.
C. Substrateshallbeclean,soundandfreeofsurfacemoisture. Removedust, laitance,andoils,curingcompoundsandallotherforeignmaterialbymechanicalmeans.
D. Cracks extending through the entiremember thickness shall be sealed from theunderside to
preventleakage.
E. The methacrylate sealer shall be applied to the surface according to manufacturer’srecommendationsandallowedtopondover thecrack. In somecases itmaybenecessary tobuildatemporarydamoneithersideofthecracktofacilitateponding.
F. The treated surface can become smooth after curing. A dry sand can be broadcast on the
partiallycuredsurfaceifasmoothsurfaceisundesirable.CRACKSONVERTICALSURFACESNOTE: Thisrepairprocedureaddressessealingcracksonverticalsurfaceswithvariousmaterials.I.EPOXYPASTE:
Anepoxypasteappliedbyhandandworkedintocrackscanprovideaneffectivemoistureseal.Thistypeofrepairistypicallyusedtosealindividualcracks.Thematerialusedshallbeapprovedbytheowner/engineerandappliedaccordingtomanufacturer’srecommendations.
A. Surfacepreparation
1. Surfacetobecleanandsound2. Surfacemaybedampordry3. Substratemust be 40 degrees F and rising with preferred temperatures ranging from 40
degreesFtonohigherthan80degreesF
B. Applicationoftheepoxypaste1. Preparetheepoxypasteaccordingtothemanufacturer’srecommendations2. Usinga thin, flexible,andsquareended,plasticornylonspatula, force theepoxygelwith
uniformpressurebysqueegeeactionintothecracks3. Fingerapplicationtothecracks ispermissible,butuniformity infillingofthecracks isbest
accomplishedwiththeactionofaspatula4. Allowtosetuntiltackfree.NoteWell:thisisatemperaturedependentprocessandat40F
andrisingthesettimewillbelongerthanat75degreesF5. Lightlyhandsandtheareatomatchtextureandappearanceofadjacentareasnotrepaired
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STANDARDREPAIRPROCEDURE#14FORSEALINGCRACKS(CONTINUED)
II.SILANEANDSILOXANESYSTEMS:
Asilaneorsiloxanebasedwater repellentscanbeapplied to thesurfacesurroundingacrack.Experiencehasshownthatthesealerswillwickintoandsealcracks≤0.013”inwidth.Multipleapplicationsmayberequired.Thistypeofrepairistypicallyusedonalargenetworkorseriesoffinecracks.Thematerialusedshallbeapprovedbytheowner/engineerandappliedaccordingtomanufacturer’srecommendations.
A. Applicationofbreathablewaterrepellent:silaneorsiloxanesytems
1. Power mix materials per manufacturer’s recommendations for the time specified, andperiodicallythereaftertoensureuniformproduct
2. Applywithpaintbrush,rollerorsprayerfromthebottomuponverticalsurfaces3. Applytosaturationpermanufacturersrecommendations
METHACRYLATE:
Alowmodulus,highmolecularweightmethacrylatesealercanbeintroducedintocracksatanyorientationusingavacuum-impregnationprocess.Thistypeofrepaircanbeusedonaseriesoffine cracks and on individual cracks. The cracks are prepared in a similar fashion to thoseundergoing an epoxy injection repair. The vacuum-impregnation process is patented byBALVAC,Inc.
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STANDARDREPAIRPROCEDURE#15FOREDGESPALLSINPRECASTELEMENTSNOTE:Thisrepairappliesonlytothosevoidsinprecast(includingprecastelementswithprestressingforhandling) which do not exceed 4 inches in depth, 4 feet in length. With the prior approval of theowner/engineer,thisrepairmaybemade,inthepresenceoftheowner’sinspectorwithoutsubmittinganon-conformancereportforformalapproval.
A. Removealllooseconcrete.
B. Squareinterfaceswithexistingconcretetobeincontactwiththepatch.
C. Cleantheexcavatedarea,blowingawaydust.
D. RepairOption1–Fillthevoidedareawithapprovedpolymermodifiedcementitious,shrinkage-compensated patching material, with a compressive strength equal to or greater than thespecifieddesignstrengthoftheelement.Prepackagedpatchingmaterialispreferredtocontrolquality.
E. RepairOption2–Coatsurfacetobeadheredtowithanapprovedbondingagent,followingthe
manufacturer’sinstructions.Fillthevoidedareawithahighstrength,cementbased,shrinkage-compensatedmortar,followingthemanufacturer’sinstructions.
F. Forlargerspallsofasimilarnatureand/orinvolvingreinforcing,thesamerepairtechniquesmay
beemployedbutmustbesubmittedtotheowner/engineerforevaluationandapproval.NOTE: Incaseswhere thepatch is locatedovervehicular trafficorpedestrianwalkways, thepatchingmaterialmustbemechanicallyanchoredeitherbyencapsulatingexistingreinforcement,beanchoredbysupplementalreinforcement,orbyotheranchoringdevices.
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Section4:ReferencesGENERAL
1. Precast/PrestressedConcreteInstitute.ManualforQualityControlforPlantsandProductionof
Structural Precast ConcreteProducts,Fourth Edition,MNL-Il6. Chicago, IL: Precast/PrestressedConcreteInstitute,1999.
2. Precast/Prestressed Concrete Institute. Bridge Design Manual, Third Edition, MNL-133-11.Chicago,IL:Precast/PrestressedConcreteInstitute,2011.
3. Neville,A.M.PropertiesofConcrete,FourthandFinalEdition.NewYork,NY:JohnWiley&Sons,Inc.,1996.
4. Zia, P. and Caner, A. October 1993. Cracking in Large-Sized Long-Span Prestressed ConcreteAASHTO Girders, Final Report, Research Project 23241-93-3 (FHWAINC/94-003). Center forTransportation Engineering Studies, Department of Civil Engineering. Raleigh, NC: NorthCarolinaStateUniversity.
5. Zhifu, Y., Brown, H., Huddleston, J. and Segar, W, Performance evaluation of rapid-setprepackaged cementitious materials for rehabilitation of surface distress of concretetransportationstructures,PCIJournal,Precast/PrestressedConcreteInstitute,March-April2016
6. Precast/Prestressed Concrete Institute. Manual for the Evaluation and Repair of Precast,Prestressed Concrete Bridge Products, First Edition, MNL-137-06-E. Chicago, IL:Precast/PrestressedConcreteInstitute,1999.
7. Arancibia,M.D. and Okumus, P., Causes of Excessive Detensioning Stresses in the NortheastExtremeTee(NEXT)Beams,PCIJournal,Precast/PrestressedConcreteInstitute,May-June2017
AASHTO
8. “LRFDBridgeDesignSpecifications,SeventhEdition,AmericanAssociationofStateHighwayandTransportationOfficials,Washington,D.C.,2014
9. LRFDBridgeConstructionSpecifications, ThirdEdition,AmericanAssociationof StateHighwayandTransportationOfficials,Washington,D.C.,2002
10. AASHTO T197, "Standard Methods of Test for Time of Setting of Concrete Mixtures byPenetration Resistance, “American Association of State Highway and Transportation Officials,Washington,D.C.
11. AASHTOT24, “StandardMethodsofObtainingandTestingDrilledCoresandSawedBeamsofConcrete”, American Association of State Highway and Transportation Officials, Washington,D.C.
12. AASHTO Highway Subcommittee on Construction, "Implementation Manual for QualityAssurance, (AASHTO IMQA), American Association of State Highway and TransportationOfficials,Washington,D.C.,1996
13. AASHTO Highway Subcommittee on Construction, "Quality Assurance Guide Specifications,(AASHTO QA)”, American Association of State Highway and Transportation Officials,Washington,D.C.,1996
ACI
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14. ACICommittee211,"StandardPracticeforSelectingProportionsforNormal,HeavyweightandMassConcrete",(ACI211.1-91)AmericanConcreteInstitute,FarmingtonHills,MI,1991
15. ACICommittee212,“ChemicalAdmixturesforConcrete",(ACI212.3R-91),AmericanConcreteInstitute,FarmingtonHills,MI,1991
16. ACICommittee221,"GuidetoUseofNormalWeightAggregates inConcrete", (ACI-221R-89),AmericanConcreteInstitute,FarmingtonHills,MI,1989
17. ACI Committee 224, “Control of Cracking in Concrete Structures”, (ACI 224R-90), AmericanConcreteInstitute,FarmingtonHills,MI,1990
18. ACICommittee503,“UseofEpoxyCompoundswithConcrete",(ACI503R-93,reapproved1998),AmericanConcreteInstitute,FarmingtonHills,MI,1998
19. ACI Committee 503, "Guide for the Selection of Polymer Admixtures with Concrete”, (ACI503.5R-92,reapproved1997),AmericanConcreteInstitute,FarmingtonHills,Ml,1997
20. ACI Committee 503, “Guide for the Application of Epoxy and Latex Adhesives for BondingFreshly Mixed and Hardened Concrete”, (ACI 503.6R-97), American Concrete Institute,FarmingtonHills,MI,1997