土木工程外文文献及翻译本科毕业论文设计

外文文献MATERIALSANDSTRUCTURESRILEM2010101617/S115270109700YORIGINALARTICLEIMPACTOFCRACKWIDTHONBONDCONFINEDANDUNCONFINEDREBARDAVIDWLAW1,DENGLEITANG2,THOMASKCMOLYNEAUX3ANDREBECCAGRAVINA31SCHOOLOFTHEBUILTENVIRONMENT,HERIOTWATTUNIVERSITY,EDINBURGH,EH144AS,UK2VICROADS,MELBOURNE,VIC,AUSTRALIA3SCHOOLOFCIVIL,ENVIRONMENTALANDCHEMICALENGINEERING,RMITUNIVERSITY,MELBOURNE,VIC,3000,AUSTRALIADAVIDWLAWEMAILDWLAWHWACUKRECEIVED14JANUARY2010ACCEPTED14DECEMBER2010PUBLISHEDONLINE23DECEMBER2010ABSTRACTTHISPAPERREPORTSTHERESULTSOFARESEARCHPROJECTCOMPARINGTHEEFFECTOFSURFACECRACKWIDTHANDDEGREEOFCORROSIONONTHEBONDSTRENGTHOFCONFINEDANDUNCONFINEDDEFORMED12AND16MMMILDSTEELREINFORCINGBARSTHECORROSIONWASINDUCEDBYCHLORIDECONTAMINATIONOFTHECONCRETEANDANAPPLIEDDCCURRENTTHEPRINCIPALPARAMETERSINVESTIGATEDWERECONFINEMENTOFTHEREINFORCEMENT,THECOVERDEPTH,BARDIAMETER,DEGREEOFCORROSIONANDTHESURFACECRACKWIDTHTHERESULTSINDICATEDTHATPOTENTIALRELATIONSHIPBETWEENTHECRACKWIDTHANDTHEBONDSTRENGTHTHERESULTSALSOSHOWEDANINCREASEINBONDSTRENGTHATTHEPOINTWHEREINITIALSURFACECRACKINGWASOBSERVEDFORBARSWITHCONFININGSTIRRUPSNOSUCHINCREASEWASOBSERVEDWITHUNCONFINEDSPECIMENSKEYWORDSBONDCORROSIONREBARCOVERCRACKWIDTHCONCRETE1INTRODUCTIONTHECORROSIONOFSTEELREINFORCEMENTISAMAJORCAUSEOFTHEDETERIORATIONOFREINFORCEDCONCRETESTRUCTURESTHROUGHOUTTHEWORLDINUNCORRODEDSTRUCTURESTHEBONDBETWEENTHESTEELREINFORCEMENTANDTHECONCRETEENSURESTHATREINFORCEDCONCRETEACTSINACOMPOSITEMANNERHOWEVER,WHENCORROSIONOFTHESTEELOCCURSTHISCOMPOSITEPERFORMANCEISADVERSELYAFFECTEDTHISISDUETOTHEFORMATIONOFCORROSIONPRODUCTSONTHESTEELSURFACE,WHICHAFFECTTHEBONDBETWEENTHESTEELANDTHECONCRETETHEDETERIORATIONOFREINFORCEDCONCRETEISCHARACTERIZEDBYAGENERALORLOCALIZEDLOSSOFSECTIONONTHEREINFORCINGBARSANDTHEFORMATIONOFEXPANSIVECORROSIONPRODUCTSTHISDETERIORATIONCANAFFECTSTRUCTURESINANUMBEROFWAYSTHEPRODUCTIONOFEXPANSIVEPRODUCTSCREATESTENSILESTRESSESWITHINTHECONCRETE,WHICHCANRESULTINCRACKINGANDSPALLINGOFTHECONCRETECOVERTHISCRACKINGCANLEADTOACCELERATEDINGRESSOFTHEAGGRESSIVEAGENTSCAUSINGFURTHERCORROSIONITCANALSORESULTINALOSSOFSTRENGTHANDSTIFFNESSOFTHECONCRETECOVERTHECORROSIONPRODUCTSCANALSOAFFECTTHEBONDSTRENGTHBETWEENTHECONCRETEANDTHEREINFORCINGSTEELFINALLYTHECORROSIONREDUCESTHECROSSSECTIONOFTHEREINFORCINGSTEEL,WHICHCANAFFECTTHEDUCTILITYOFTHESTEELANDTHELOADBEARINGCAPACITY,WHICHCANULTIMATELYIMPACTUPONTHESERVICEABILITYOFTHESTRUCTUREANDTHESTRUCTURALCAPACITY12,25PREVIOUSRESEARCHHASINVESTIGATEDTHEIMPACTOFCORROSIONONBOND25,7,12,20,2325,27,29,WITHANUMBEROFMODELSBEINGPROPOSED4,6,9,10,18,19,24,29THEMAJORITYOFTHISRESEARCHHASFOCUSEDONTHERELATIONSHIPBETWEENTHELEVELOFCORROSIONMASSLOSSOFSTEELORTHECURRENTDENSITYDEGREECORROSIONCURRENTAPPLIEDINACCELERATEDTESTINGANDCRACKWIDTH,ORONTHERELATIONSHIPBETWEENBONDSTRENGTHANDLEVELOFCORROSIONOTHERRESEARCHHASINVESTIGATEDTHEMECHANICALBEHAVIOUROFCORRODEDSTEEL1,11ANDTHEFRICTIONCHARACTERISTICS13HOWEVER,LITTLERESEARCHHASFOCUSEDONTHERELATIONSHIPBETWEENCRACKWIDTHANDBOND23,26,28,APARAMETERTHATCANBEMEASUREDWITHRELATIVEEASEONACTUALSTRUCTURESTHECORROSIONOFTHEREINFORCINGSTEELRESULTSINTHEFORMATIONOFIRONOXIDESWHICHOCCUPYALARGERVOLUMETHANTHATOFTHEPARENTMETALTHISEXPANSIONCREATESTENSILESTRESSESWITHINTHESURROUNDINGCONCRETE,EVENTUALLYLEADINGTOCRACKINGOFTHECOVERCONCRETEONCECRACKINGOCCURSTHEREISALOSSOFCONFININGFORCEFROMTHECONCRETETHISSUGGESTSTHATTHELOSSOFBONDCAPACITYCOULDBERELATEDTOTHELONGITUDINALCRACKWIDTH12HOWEVER,THEUSEOFCONFINEMENTWITHINTHECONCRETECANCOUNTERACTTHISLOSSOFBONDCAPACITYTOACERTAINDEGREERESEARCHTODATEHASPRIMARILYINVOLVEDSPECIMENSWITHCONFINEMENTTHISPAPERREPORTSASTUDYCOMPARINGTHELOSSOFBONDOFSPECIMENSWITHANDWITHOUTCONFINEMENT2EXPERIMENTALINVESTIGATION21SPECIMENSBEAMENDSPECIMENS28WERESELECTEDFORTHISSTUDYTHISTYPEOFECCENTRICPULLOUTORBEAMENDTYPESPECIMENUSESABONDEDLENGTHREPRESENTATIVEOFTHEANCHORAGEZONEOFATYPICALSIMPLYSUPPORTEDBEAMSPECIMENSOFRECTANGULARCROSSSECTIONWERECASTWITHALONGITUDINALREINFORCINGBARINEACHCORNER,FIG1AN80MMPLASTICTUBEWASPROVIDEDATTHEBARUNDERNEATHTHETRANSVERSEREACTIONTOENSURETHATTHEBONDSTRENGTHWASNOTENHANCEDDUETOATRANSVERSECOMPRESSIVEFORCEACTINGONTHEBAROVERTHISLENGTHFIG1BEAMENDSPECIMENDEFORMEDREBAROF12AND16MMDIAMETERWITHCOVEROFTHREETIMESBARDIAMETERWEREINVESTIGATEDDUPLICATESETSOFCONFINEDANDUNCONFINEDSPECIMENSWERETESTEDTHECONFINEDSPECIMENSHADTHREESETSOF6MMSTAINLESSSTEELSTIRRUPSEQUALLYSPACEDFROMTHEPLASTICTUBE,AT75MMCENTRESTHISREPRESENTSFOURGROUPSOFSPECIMENSWITHACOMBINATIONOFDIFFERENTBARDIAMETERANDWITH/WITHOUTCONFINEMENTTHESPECIMENSWERESELECTEDINORDERTOINVESTIGATETHEINFLUENCEOFBARSIZE,CONFINEMENTANDCRACKWIDTHONBONDSTRENGTH22MATERIALSTHEMIXDESIGNISSHOWN,TABLE1THECEMENTWASTYPEIPORTLANDCEMENT,THEAGGREGATEWASBASALTWITHSPECIFICGRAVITY299THECOARSEANDFINEAGGREGATEWEREPREPAREDINACCORDANCEWITHAS11412000MIXINGWASUNDERTAKENINACCORDANCEWITHAS101221994SPECIMENSWERECUREDFOR28DAYSUNDERWETHESSIANBEFORETESTINGTABLE1CONCRETEMIXDESIGNMATERIALCEMENTW/CSAND10MMWASHEDAGGREGATE7MMWASHEDAGGREGATESALTSLUMPQUANTITY381KG/M3049517KG/M3463KG/M3463KG/M31884KG/M314025MMINORDERTOCOMPAREBONDSTRENGTHFORTHEDIFFERENTCONCRETECOMPRESSIVESTRENGTHS,EQ1ISUSEDTONORMALIZEBONDSTRENGTHFORNONCORRODEDSPECIMENSASHASBEENUSEDBYOTHERRESEARCHER81WHEREISTHEBONDSTRENGTHFORGRADE40CONCRETE,EXPTLISTHEEXPERIMENTALBONDSTRENGTHANDFCISTHEEXPERIMENTALCOMPRESSIVESTRENGTHTHETENSILESTRENGTHOFTHE12AND16MMSTEELBARSWASNOMINALLY500MPA,WHICHEQUATESTOAFAILURELOADOF565AND1005KN,RESPECTIVELY23EXPERIMENTMETHODOLOGYACCELERATEDCORROSIONHASBEENUSEDBYANUMBEROFAUTHORSTOREPLICATETHECORROSIONOFTHEREINFORCINGSTEELHAPPENINGINTHENATURALENVIRONMENT2,3,5,6,10,18,20,24,27,28,30THESEHAVEINVOLVEDEXPERIMENTSUSINGIMPRESSEDCURRENTSORARTIFICIALWEATHERINGWITHWET/DRYCYCLESANDELEVATEDTEMPERATURESTOREDUCETHETIMEUNTILCORROSION,WHILEMAINTAININGDETERIORATIONMECHANISMSREPRESENTATIVEOFNATURALEXPOSURESTUDIESUSINGIMPRESSEDCURRENTSHAVEUSEDCURRENTDENSITIESBETWEEN100A/CM2AND500MA/CM220RESEARCHHASSUGGESTEDTHATCURRENTDENSITIESUPTO200A/CM2RESULTINSIMILARSTRESSESDURINGTHEEARLYSTAGESOFCORROSIONWHENCOMPAREDTO100A/CM221ASSUCHANAPPLIEDCURRENTDENSITYOF200A/CM2WASSELECTEDFORTHISSTUDYREPRESENTATIVEOFTHELOWERENDOFTHESPECTRUMOFSUCHCURRENTDENSITIESADOPTEDINPREVIOUSRESEARCHHOWEVER,CAUTIONSHOULDBEAPPLIEDWHENACCELERATINGTHECORROSIONUSINGIMPRESSEDCURRENTASTHEACCELERATIONPROCESSDOESNOTEXACTLYREPLICATETHEMECHANISMSINVOLVEDINACTUALSTRUCTURESINACCELERATEDTESTSTHEPITSARENOTALLOWEDTOPROGRESSNATURALLY,ANDTHEREMAYBEAMOREUNIFORMCORROSIONONTHESURFACEALSOTHERATEOFCORROSIONMAYIMPACTONTHECORROSIONPRODUCTS,SUCHTHATDIFFERENTOXIDATIONSTATEPRODUCTSMAYBEFORMED,WHICHCOULDIMPACTONBONDTHESTEELBARSSERVEDASTHEANODEANDFOURMILDSTEELMETALPLATESWEREFIXEDONTHESURFACETOSERVEASCATHODESSPONGESSPRAYEDWITHSALTWATERWEREPLACEDBETWEENTHEMETALPLATESANDCONCRETETOPROVIDEANADEQUATECONTACT,FIG2FIG2ACCELERATEDCORROSIONSYSTEMWHENTHEREQUIREDCRACKWIDTHWASACHIEVEDFORAPARTICULARBAR,THEIMPRESSEDCURRENTWASDISCONTINUEDFORTHATBARTHESPECIMENWASREMOVEDFORPULLOUTTESTINGWHENALLFOURLOCATIONSEXHIBITEDTHETARGETCRACKWIDTHAVERAGESURFACECRACKWIDTHSOF005,05,1AND15MMWEREADOPTEDASTHETARGETCRACKWIDTHSTHESURFACECRACKWIDTHWASMEASUREDAT20MMINTERVALSALONGTHELENGTHOFTHEBAR,BEGINNING20MMFROMTHEENDOFTHEPLASTICTUBEBONDBREAKERUSINGANOPTICALMICROSCOPETHELEVELOFACCURACYINTHEMEASUREMENTSWAS002MMMEASUREMENTSOFCRACKWIDTHWERETAKENONTHESURFACENORMALTOTHEBARDIRECTIONREGARDLESSOFTHEACTUALCRACKORIENTATIONATTHATLOCATIONBONDSTRENGTHTESTSWERECONDUCTEDBYMEANSOFAHANDOPERATEDHYDRAULICJACKANDACUSTOMBUILTTESTRIGASSHOWNINFIG3THELOADINGSCHEMEISILLUSTRATEDINFIG4APLASTICTUBEOFLENGTH80MMWASPROVIDEDATTHEENDOFTHECONCRETESECTIONUNDERNEATHTHETRANSVERSEREACTIONTOENSURETHATTHEBONDSTRENGTHWASNOTENHANCEDBYTHEREACTIVECOMPRESSIVEFORCEACTINGNORMALTOTHEBARTHESPECIMENWASPOSITIONEDSOTHATANAXIALFORCEWASAPPLIEDTOTHEBARBEINGTESTEDTHERESTRAINTSWERESUFFICIENTLYRIGIDTOENSUREMINIMALROTATIONORTWISTINGOFTHESPECIMENDURINGLOADINGFIG3PULLOUTTEST,16MMBARUNCONFINEDFIG4SCHEMATICOFLOADINGNOTEONLYTESTBARSHOWNFORCLARITY3EXPERIMENTALRESULTSANDDISCUSSION31VISUALINSPECTIONFOLLOWINGTHEACCELERATEDCORROSIONPHASEEACHSPECIMENWASVISUALLYINSPECTEDFORTHELOCATIONOFCRACKS,MEANCRACKWIDTHANDMAXIMUMCRACKWIDTHSECT23WHILEEACHSPECIMENHADAMEANTARGETCRACKWIDTHFOREACHBAR,VARIATIONSINTHISCRACKWIDTHWEREOBSERVEDPRIORTOPULLOUTTESTINGTHISISDUETOCORROSIONANDCRACKINGBEINGADYNAMICPROCESSWITHCRACKSPROPAGATINGATDIFFERENTRATESTHUS,WHILEINDIVIDUALBARSWEREDISCONNECTED,ONCETHETARGETCRACKWIDTHHADBEENACHIEVED,CORROSIONANDCRACKPROPAGATIONCONTINUEDTOSOMEEXTENTUNTILALLBARSHADACHIEVEDTHETARGETCRACKWIDTHANDPULLOUTTESTSCONDUCTEDTHISRESULTEDINARANGEOFDATAFORTHEMAXIMUMANDMEANCRACKWIDTHSFORTHEPULLOUTTESTSTHEVISUALINSPECTIONOFTHESPECIMENSSHOWEDTHREESTAGESTOTHECRACKINGPROCESSTHEINITIALCRACKSOCCURREDINAVERYSHORTPERIOD,USUALLYGENERATEDWITHINAFEWDAYSAFTERTHAT,MOSTCRACKSGREWATACONSTANTRATEUNTILTHEYREACHED1MM,34WEEKSAFTERFIRSTCRACKINGAFTERCRACKSHADREACHED1MMTHEYTHENGREWVERYSLOWLY,WITHSOMECRACKSNOTINCREASINGATALLFORTHECONFINEDANDUNCONFINEDSPECIMENSTHESURFACECRACKSTENDEDTOOCCURONTHESIDEOFTHESPECIMENSASOPPOSEDTOTHETOPORBOTTOMANDTOFOLLOWTHELINEOFTHEBARSINTHECASEOFTHEUNCONFINEDSPECIMENSINGENERALTHESEWERETHEONLYCRACKWHILEITWASCOMMONINTHECASESOFCONFINEDSPECIMENSTOOBSERVECRACKSTHATWEREALIGNEDVERTICALLYDOWNTHESIDEADJACENTTOONEOFTHELINKS,FIG5FIG5TYPICALCRACKPATTERNSDURINGTHEPULLOUTTESTINGTHEMOSTCOMMONFAILUREMODEFORBOTHCONFINEDANDUNCONFINEDWASSPLITTINGFAILUREWITHTHEINITIALPRETESTCRACKSCAUSEDBYTHECORROSIONENLARGINGUNDERLOADANDULTIMATELYLEADINGTOTHESECTIONFAILINGEXHIBITINGSPALLINGOFTHETOPCORNER/EDGE,FIG6HOWEVERFORSEVERALOFTHECONFINEDSPECIMENS,ASECONDMODEOFFAILUREALSOOCCURREDWITHDIAGONALSHEARLIKECRACKSAPPEARINGINTHESIDEWALLS,FIG7THEAPPEARANCEOFTHESECRACKSDIDNOTAPPEARTOBERELATEDTOTHEPRESENCEOFVERTICALCRACKSOBSERVEDINSPECIMENSWITHSTIRRUPSDURINGTHECORROSIONPHASEASREPORTEDABOVEFIG6LONGITUDINALCRACKINGAFTERPULLOUTFIG7DIAGONALCRACKINGAFTERPULLOUTTHEBARSWEREINITIALLYPRECASTINGCLEANEDWITHA12HYDROCHLORICACIDSOLUTION,THENWASHEDINDISTILLEDWATERANDNEUTRALIZEDBYACALCIUMHYDROXIDESOLUTIONBEFOREBEINGWASHEDINDISTILLEDWATERAGAINFOLLOWINGTHEPULLOUTTESTS,THECORRODEDBARSWERECLEANEDINTHESAMEWAYANDWEIGHEDAGAINTHECORROSIONDEGREEWASDETERMINEDUSINGTHEFOLLOWINGEQUATIONWHEREG0ISTHEINITIALWEIGHTOFTHESTEELBARBEFORECORROSION,GISTHEFINALWEIGHTOFTHESTEELBARAFTERREMOVALOFTHEPOSTTESTCORROSIONPRODUCTS,G0ISTHEWEIGHTPERUNITLENGTHOFTHESTEELBAR0888AND158G/MMFOR12AND16MMBARS,RESPECTIVELY,LISTHEEMBEDDEDBONDLENGTHFIGURES8AND9SHOWSTEELBARSWITHVARYINGDEGREEOFCORROSIONTHEMAJORITYEXHIBITEDVISIBLEPITTING,SIMILARTOTHATOBSERVEDONREINFORCEMENTINACTUALSTRUCTURES,FIG9HOWEVER,ASMALLNUMBEROFOTHERSEXHIBITEDSIGNIFICANTOVERALLSECTIONLOSS,WITHAMOREUNIFORMLEVELOFCORROSION,FIG8,WHICHMAYBEAFUNCTIONOFTHEACCELERATIONMETHODOLOGYFIG8CORRODED12MMBARWITHAPPROXIMATELY30MASSLOSSFIG9CORRODED16MMBARWITHAPPROXIMATELY15MASSLOSS32BONDSTRESSANDCRACKWIDTHFIGURE10SHOWSTHEVARIATIONOFBONDSTRESSWITHMEANCRACKWIDTHFOR16MMBARSANDFIG11FORTHE12MMBARSFIGURES12AND13SHOWTHEDATAFORTHEMAXIMUMCRACKWIDTHFIG10MEANCRACKWIDTHVERSUSBONDSTRESSFOR16MMBARSFIG11MEANCRACKWIDTHVERSUSBONDSTRESSFOR12MMBARSFIG12MAXIMUMCRACKWIDTHVERSUSBONDSTRESSFOR16MMBARSFIG13MAXIMUMCRACKWIDTHVERSUSBONDSTRESSFOR12MMBARSTHEDATASHOWANINITIALINCREASEINBONDSTRENGTHFORTHE12MMSPECIMENSWITHSTIRRUPS,FOLLOWEDBYASIGNIFICANTDECREASEINBOND,WHICHISINAGREEMENTWITHOTHERAUTHORS12,15FORTHE16MMSPECIMENSANINCREASEONTHECONTROLBONDSTRESSWASOBSERVEDFORSPECIMENSWITH028AND035MMMEANCRACKWIDTHS,HOWEVER,ADECREASEINBONDSTRESSWASOBSERVEDFORATTHEMEANCRACKWIDTHOF005MMTHE12MMBARSWITHSTIRRUPSDISPLAYEDANINCREASEINBONDSTRESSOFAPPROXIMATELY25FROMTHECONTROLVALUESTOTHEMAXIMUMBONDSTRESSANINCREASEOFAPPROXIMATELY14WASOBSERVEDFORTHE16MMSPECIMENSOTHERRESEARCHERS17,24,25HAVEREPORTEDENHANCEMENTSOFBONDSTRESSOFBETWEEN10AND60DUETOCONFINEMENT,SLIGHTLYHIGHERTOTHATOBSERVEDINTHESEEXPERIMENTHOWEVERTHELOADINGTECHNIQUESANDCOVERDEPTHSHAVENOTALLBEENTHESAMEVARIATIONSINEXPERIMENTALTECHNIQUESINCLUDEASHORTEREMBEDDEDLENGTHANDALOWERCOVERTHEVARIATIONONTHEPROPOSEDEMPIRICALRELATIONSHIPBETWEENBONDSTRENGTH,DEGREEOFCORROSION,BARSIZE,COVER,LINKDETAILSANDTENSILESTRENGTHPREDICTEDBYRODRIGUEZ24HASBEENDISCUSSEDINDETAILINTANGETAL28THEANALYSISDEMONSTRATESTHATTHEREWOULDBEANEXPECTEDENHANCEMENTOFBONDSTRENGTHDUETOCONFINEMENTOFAPPROXIMATELY25CORRESPONDINGTOACHANGEOFBONDSTRENGTHOFAPPROXIMATELY075MPAFORTHE16MMBARSASSESSEDATA2SECTIONLOSSFORTHE12MMBARSTHECORRESPONDINGEFFECTOFCONFINEMENTISFOUNDTOBEAPPROXIMATELY35CORRESPONDINGTOA10MPADIFFERENCEINBONDSTRESSTHEEXPERIMENTALRESULTS14AND25,ABOVEARE6070OFTHESEVALUESBOTHSETSOFDATAINDICATEARELATIONSHIPSHOWINGDECREASINGBONDSTRENGTHWITHVISIBLESURFACECRACKWIDTHAREGRESSIONANALYSISOFTHEBONDSTRENGTHDATAREVEALSABETTERLINEARRELATIONSHIPWITHTHEMAXIMUMCRACKWIDTHASOPPOSEDTOTHEMEANCRACKWIDTHEXCLUDINGTHEUNCRACKEDCONFINEDSPECIMENS,TABLE2TABLE2BESTFITPARAMETERS,CRACKWIDTHVERSUSBONDSTRENGTHUNCONFINED12MMCONFINED12MMUNCONFINED16MMCONFINED16MMMEANCRACKWIDTHR20920063706720659SLOPEM3997365329998848INTERCEPTB7560812264968746MAXIMUMCRACKWIDTHR20937085507140616UNCONFINED12MMCONFINED12MMUNCONFINED16MMCONFINED16MMSLOPEM2719296818155330INTERCEPTB7805840367079636THEREWASALSOASIGNIFICANTLYBETTERFITFORTHEUNCONFINEDSPECIMENSTHANTHECONFINEDSPECIMENSTHISISCONSISTENTWITHTHEOBSERVATIONTHATINTHEUNCONFINEDSPECIMENSTHEBONDSTRENGTHWILLBERELATEDTOTHEBONDBETWEENTHEBARSANDTHECONCRETE,WHICHWILLBEAFFECTEDBYTHELEVELOFCORROSIONPRESENT,WHICHITSELFWILLINFLUENCETHECRACKWIDTHINCONFINEDSPECIMENSTHECONFININGSTEELWILLIMPACTUPONBOTHTHEBONDANDTHECRACKING33CORROSIONDEGREEANDBONDSTRESSITISAPPARENTTHATFIG14FORCORROSIONDEGREESLESSTHAN5THEBONDSTRESSCORRELATEDWELLHOWEVER,ASTHEDEGREEOFCORROSIONINCREASEDTHEREWASNOOBSERVABLECORRELATIONATALLTHISCONTRASTSWITHTHERELATIONSHIPBETWEENTHEOBSERVEDCRACKWIDTHANDBONDSTRESS,WHICHGIVESAREASONABLECORRELATION,EVENASCRACKWIDTHSINCREASETO2AND25MMAPOSSIBLEEXPLANATIONFORTHISVARIATIONISTHATINTHEINITIALSTAGESOFCORROSIONVIRTUALLYALLTHEDISSOLVEDIRONIONSREACTTOFORMEXPANSIVECORROSIONPRODUCTSTHISREACTIONIMPACTSONBOTHTHEBONDSTRESSANDTHEFORMATIONOFCRACKSHOWEVER,ONCECRACKSHAVEBEENFORMEDITISPOSSIBLEFORTHEIRONIONSTOBETRANSPORTEDALONGTHECRACKANDOUTOFTHECONCRETEASTHEBONDHASALREADYBEENEFFECTIVELYLOSTATTHECRACKANYIRONIONSDISSOLVINGATTHECRACKANDBEINGDIRECTLYTRANSPORTEDOUTOFTHECONCRETEWILLCAUSEANINCREASEINTHEDEGREEOFCORROSION,BUTNOTAFFECTTHESURFACECRACKWIDTHTHELOCATION,ORIENTATIONANDCHEMISTRYWITHINTHECRACKWILLCONTROLTHERELATIONSHIPBETWEENBONDSTRESSANDDEGREEOFCORROSION,WHICHWILLVARYFROMSPECIMENTOSPECIMENHENCETHELARGEVARIATIONSINCORROSIONDEGREEANDBONDSTRESSFORHIGHLEVELSOFCORROSIONFIG14BONDSTRESSVERSUSCORROSIONDEGREE,12MMBARS,UNCONFINEDSPECIMENSIGNIFICANTLYLARGERCRACKWIDTHSWEREOBSERVEDFORTHEUNCONFINEDSPECIMENS,COMPAREDTOTHECONFINEDSPECIMENSWITHSIMILARLEVELSOFCORROSIONANDMASSLOSTTHELARGESTOBSERVEDCRACKFORUNCONFINEDSPECIMENSWAS25MMCOMPAREDTO14MMFORTHECONFINEDSPECIMENSTHISISASEXPECTEDANDISADIRECTRESULTOFTHECONFINEMENTWHICHLIMITSTHEDEGREEOFCRACKING34EFFECTOFCONFINEMENTTHEUNCONFINEDSPECIMENSFORBOTH16AND12MMBARSDIDNOTDISPLAYTHEINITIALINCREASEINBONDSTRENGTHOBSERVEDFORTHECONFINEDBARSINDEEDTHEUNCONFINEDSPECIMENSWITHCRACKSALLDISPLAYEDAREDUCEDBONDSTRESSCOMPAREDTOTHECONTROLSPECIMENSTHISISINAGREEMENTWITHOTHERAUTHORS16,24FINDINGSFORCRACKEDSPECIMENSINCRACKEDCORRODEDSPECIMENSFANGOBSERVEDASUBSTANTIALREDUCTIONINBONDSTRENGTHFORDEFORMEDBARSWITHOUTSTIRRUPS,WHILERODRIGUEZOBSERVEDBONDSTRENGTHSOFHIGHLYCORRODEDCRACKEDSPECIMENSWITHOUTSTIRRUPSWERECLOSETOZERO,WHILEHIGHLYCORRODEDCRACKEDSPECIMENSWITHSTIRRUPSRETAINEDBONDSTRENGTHSOFBETWEEN3AND4MPAINUNCORRODEDSPECIMENSCHANANOTEDANINCREASEINBONDSTRENGTHDUETOSTIRRUPSOFBETWEEN10AND2014HOWEVERRODRIGUEZANDFANGOBSERVEDNOVARIATIONDUETOTHEPRESENCEOFCONFINEMENTINUNCORRODEDBARSTHEDATAISPERHAPSUNEXPECTEDASITCOULDBEANTICIPATEDTHATTHECORROSIONPRODUCTSWOULDLEADTOANINCREASEINBONDDUETOTHEINCREASEININTERNALPRESSURES,CAUSEDBYTHECORROSIONPRODUCTSINCREASINGTHECONFINEMENTANDMECHANICALINTERLOCKINGAROUNDTHEBAR,COUPLEDWITHINCREASEDROUGHNESSOFTHEBARRESULTINGINAGREATERFRICTIONBETWEENTHEBARANDTHESURROUNDINGCONCRETEHOWEVER,THESEPRESSURESWOULDTHENRELIEVEDBYTHESUBSEQUENTCRACKINGOFTHECONCRETE,WHICHWOULDCONTRIBUTETOTHEDECREASEINTHEBONDSTRENGTHASCRACKWIDTHSINCREASEAPOSSIBLEHYPOTHESISISTHATDUETOTHELEVELOFCOVER,THREETIMESBARDIAMETER,THEEFFECTOFCONFINEMENTBYTHESTIRRUPSISREDUCED,SUCHTHATITHASLITTLEIMPACTONTHEBONDSTRESSINUNCRACKEDCONCRETEHOWEVER,ONCECRACKINGHASTAKENPLACETHECONFINEMENTDOESHAVEABENEFICIALEFFECTONTHEBONDITMAYALSOBETHATTHECOMPRESSIVESTRENGTHOFTHECONCRETECOMBINEDWITHTHECOVERWILLHAVEANEFFECTONTHEBONDSTRESSESFORUNCORRODEDSPECIMENSTHEDATAPRESENTEDHEREHASACOVEROFTHREETIMESBARDIAMETERANDASTRENGTHOF40MPA,OTHERRESEARCHRANGESFROM15TOFOURTIMESCOVERWITHCOMPRESSIVESTRENGTHSFROM40TO77MPA35COMPARISONOF12AND16MMREBARTHEMAXIMUMBONDSTRESSFOR16MMUNCONFINEDBARSWASMEASUREDAT806MPAANDFORTHE12MMBARSITWAS843MPATHESEBOTHCORRESPONDEDTOTHECONTROLSPECIMENSWITHNOCORROSIONTHEUNCONFINEDSPECIMENSFORBOTHTHE12AND16MMBARSSHOWEDNOINCREASEINBONDSTRESSDUETOCORROSIONFORTHECONFINEDSPECIMENSTHEMAXIMUMBONDSTRESSFORTHECONTROLSPECIMENSWERE729MPAFORTHE12MMBARSAND634MPAFORTHE16MMBARSTHEMAXIMUMBONDSTRESSFORBOTHSETSOFCONFINEDSPECIMENSCORRESPONDEDTOPOINTOFTHEINITIALCRACKINGTHEMAXIMUMBONDSTRESSESWEREOBSERVEDATAMEANCRACKWIDTHOF001MMFORTHE12MMBARSAND028MMFORTHE16MMBARSTHECORRESPONDINGBONDSTRESSESWERE,845AND720MPAOVERALLTHE12MMBARSDISPLAYEDHIGHERBONDSTRESSESCOMPAREDTOTHE16MMBARSATALLCRACKWIDTHSTHISISATTRIBUTEDTOADIFFERENTFAILUREMODETHE16MMSPECIMENSDEMONSTRATESPLITTINGFAILUREWHILETHE12MMBARSBONDFAILURE36EFFECTOFCASTINGPOSITIONTHEREWASNOSIGNIFICANTDIFFERENCEOFBONDSTRENGTHDUETOTHEPOSITIONOFTHEBARTOPORBOTTOMCASTONCECRACKINGWASOBSERVED,FIG15FORCONTROLSPECIMENS,WITHNOCORROSION,HOWEVER,THEBOTTOMCASTBARSHADASLIGHTLYHIGHERBONDSTRESSTHANTHETOPCASTBARSTHESEOBSERVATIONSAREINAGREEMENTWITHOTHERAUTHORS4,11,15,22ITISGENERALLYACCEPTEDTHATUNCORRODEDBOTTOMCASTBARSHAVESIGNIFICANTLYIMPROVEDBONDCOMPAREDTOTOPCASTBARSDUETOTHECORROSIONPRODUCTSFILLINGTHEVOIDSTHATAREOFTENPRESENTUNDERTOPCASTBARSASTHECORROSIONPROGRESSES14THECORROSIONALSOACTSASANANCHOR,SIMILARTOTHERIBSONDEFORMEDBARS,TOINCREASETHEBONDOVERALL,THEMEANVALUEOFBONDSTRESSFORALLBARSCORRODEDANDUNCORRODEDLOCATEDINTHETOPWEREWITHIN1OFTHEMEANBONDSTRESSOFALLBARSLOCATEDINTHEBOTTOMOFTHESECTIONFO