ADVANCESINENGINEERED CEMENTITIOUS COMPOSITE
Materials,Structures,and NumericalModeling
Editedby
Y.X.ZHANG
WesternSydneyUniversity,Penrith,NSW,Australia
KEQUAN YU
CollegeofCivilEngineering,TongjiUniversity,Shanghai,China
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Contributors
YaoDing SchoolofCivilEngineering;KeyLaboratoryofNewTechnologyfor ConstructionofCitiesinMountainArea(MinistryofEducation),Chongqing University,Chongqing,China
Wan-YangGao StateKeyLaboratoryofOceanEngineering;ShanghaiKey LaboratoryforDigitalMaintenanceofBuildingsandInfrastructure,Schoolof NavalArchitecture,OceanandCivilEngineering,ShanghaiJiaoTongUniversity,Shanghai,China
Ke-XuHu DepartmentofDisasterMitigationforStructures,TongjiUniversity, Shanghai,China
TingHuang SchoolofEngineeringandInformationTechnology,TheUniversity ofNewSouthWales,Canberra,ACT,Australia;CollegeofCivilEngineering andArchitecture,GuilinUniversityofTechnology,Guilin,China
LiuJiepeng SchoolofCivilEngineering;KeyLaboratoryofNewTechnologyfor ConstructionofCitiesinMountainArea(MinistryofEducation),Chongqing University,Chongqing,China
MdImranKabir SchoolofEngineeringandInformationTechnology,TheUniversityofNewSouthWales,Canberra,ACT,Australia
MuhammadKhubaibIlyasKhan SchoolofEngineeringandInformation Technology,TheUniversityofNewSouthWales,Canberra,ACT;Schoolof Engineering,DesignandBuiltEnvironment,WesternSydneyUniversity, Penrith,NSW,Australia
ChiKingLee SchoolofEngineeringandInformationTechnology,TheUniversityofNewSouthWales,Canberra,ACT,Australia
J.Li SchoolofCivilEngineeringandTransportation,SouthChinaUniversityof Technology,Guangzhou,China;SchoolofEngineeringandInformationTechnology,TheUniversityofNewSouthWales,Canberra,ACT,Australia
JianchunLi SchoolofCivilandEnvironmentalEngineering,UniversityofTechnologySydney,Sydney,NSW,Australia
XiaoshanLin RMITUniversity,Melbourne,VIC,Australia
DanMeng SchoolofEngineeringandInformationTechnology,TheUniversity ofNewSouthWales,Canberra,ACT,Australia
MohammadMasudRana SchoolofEngineeringandInformationTechnology, TheUniversityofNewSouthWales,Canberra,ACT,Australia
KhinThandarSoe SchoolofEngineeringandInformationTechnology,UniversityofNewSouthWales,Canberra,ACT;UBIQTechnologyPtyLtd,Sydney, NSW,Australia
HaiTranThanh SchoolofCivilandEnvironmentalEngineering,Universityof TechnologySydney,Sydney,NSW,Australia
Tian-CiWang StateKeyLaboratoryofOceanEngineering;ShanghaiKeyLaboratoryforDigitalMaintenanceofBuildingsandInfrastructure,SchoolofNaval Architecture,OceanandCivilEngineering,ShanghaiJiaoTongUniversity, Shanghai,China
MaoWeihao SchoolofCivilEngineering;KeyLaboratoryofNewTechnology forConstructionofCitiesinMountainArea(MinistryofEducation),Chongqing University,Chongqing,China
LeiYang RMITUniversity,Melbourne,VIC,Australia
KequanYu CollegeofCivilEngineering,TongjiUniversity,Shanghai,China
LiangchiZhang SchoolofMechanicalEngineering,UniversityofNewSouth Wales,Sydney,Australia
Y.X.Zhang SchoolofEngineering,DesignandBuiltEnvironment,Western SydneyUniversity,Penrith,NSW;SchoolofEngineeringandInformation Technology,TheUniversityofNewSouthWales,Canberra,ACT,Australia
ShiyaoZhu SchoolofEngineeringandInformationTechnology,TheUniversity ofNewSouthWales,Canberra,ACT,Australia
Preface
Cementitiouscompositeshavebeenwidelyusedinconstructionsdue totheirmanyadvantagessuchashighcompressivestrength.However, duetotheinherentweaknessinresistingtension,crackingoftenoccurs incementitiouscompositesduringtheirservicelife,andthusdurability, serviceability,andsustainabilityhavebeenlong-termconcerns.Fiberreinforcedcementitiouscomposites(FRCCs)aresignificantdevelopments incementitiouscompositesandwithshortfiberaddedrandomlytothe composites,high-performanceFRCCscouldbedeveloped.Inrecent decades,numerousresearchworkshavebeenreportedtoachieveFRCC withhighperformance,suchasFRCCwithultrahighstrengthandultrahighductility,andwithdifferentfunctionssuchasimpactandblastresistance.Thedevelopmentofhigh-performanceFRCCpropelstheresearch ofcementitiouscompositesandalsopresentsthestrongpotentialto enhancethedurability,serviceability,andresilienceofinfrastructures. Thebookpresentstherecentdevelopmentonhigh-performanceFRCC inthreeaspects,i.e.,materials,structures,andnumericalmodeling,aimingtoprovidecomprehensiveknowledgeonhigh-performanceFRCC frommaterialdevelopmenttostructuralapplicationandfromexperimentalstudiestoadvancednumericalmodelingtechnique.SectionIpresents theselecteddevelopmentsofthematerialstoachievethespecifichighperformancebyusingdifferenttypesoffibers.SectionIIincludestherecent experimentalstudiesontheperformanceofthestructuralcomponents includingbeams,slabs,andcolumnsusingthehigh-performanceFRCC. Thiswillprovideimportantreferencesfortheexperimentalmethodsand measuringtechniques.Theresearchonstructuresprovidesanimportant referenceforstructuraldesignandinformsthepractitionersaboutthe potentialbenefitsintheapplicationofthesenovelandhigh-performance materialsinengineering.SectionIIIincludestherecentdevelopmentof numericalmethodsandmodelingtechniquesforthemodelingofmaterial propertiesandstructuralbehavior.Themultiscalenumericalmodeling methodandtechniquesonthematerialpropertiesandfiniteelementanalysisofstructuralbehaviorofbeams,slabs,andcolumnsunderstaticloading,fatigue,andimpactloadingarepresented.
MostoftheworkincludedinthisbookarefrommyPhDstudents, researchfellows,andcoworkerswhoworkedwithmeinthelast 10years.Ifeelveryfortunatetohavehadtheopportunitiestoworkwith
thesetalentedanddedicatedresearchers.Isincerelythankthemfortheir hardworkandeffortsandthankallauthorsfortheircontributiontothis book.Iamveryappreciativeoftheassistancefromthecoeditor Dr.KequanYuineditingthisbook. Y.X.Zhang Sydney,Australia
May2021
KequanYua andY.X.Zhangb
aCollegeofCivilEngineering,TongjiUniversity,Shanghai,China, bSchoolof Engineering,DesignandBuiltEnvironment,WesternSydneyUniversity, Penrith,NSW,Australia
1.1Introduction
Concreteisaprimaryconstructionandbuildingmaterialinmodern civilengineering;itpossessesrelativelyhighcompressivestrength,and isconvenienttoconstructwiththewideavailabilityofrawmaterials. However,ordinaryconcreteisaquasibrittlematerialwithlowtensile strengthandlowtensilestraincapacity,resultinginundesirablecracks. Thewidthofthesecracksislargeenoughforthemigrationofharmfulchemicals,suchaschlorideions,triggeringcorrosionofsteelreinforcement. Otherfactors,suchasfreezingandthawingandshrinkage,alsoaffectthe durabilityofordinaryconcretelimitingitsengineeringapplications.
Fiber-reinforcedconcrete(FRC),whichisreinforcedwithdiscontinuousanddiscretefibers,hasdemonstrateditseffectivenessinenhancing thefracturetoughnessandductilityofconcrete.Moreover,thereinforcing fibersarefoundtoplayanimportantbridgingroleinthematrix,which couldcontrolcrackopeningandpropagation,andenhancethedurability ofconcretestructures(Banthia&Sheng,1996; Brandt,2008).Nevertheless, thetensileductilityofFRCremainslowwithtension-softeningpostpeak behaviorasshownin Fig.1.1.
Withthebloomingdevelopmentofmegastructuresandthegradual deteriorationofexistinginfrastructures,higherrequirementsareimposed ontheperformancesofbuildingmaterialsindifferentaspects,including
Multiple cracking (spc,epc) (scc,ecc)
Strain hardening
Strain softening
Strain softening
ductility,durability,andcrackcontrolcapacity.Inrecentdecades,the developmentofhigh-performancefiber-reinforcedcementitiouscomposite(HPFRCC)featuringtensilestrain-hardeningbehavioraccompanied bymultiplecrackingandhighenergyabsorptioncapacityhasbeena focusedresearchareaandattractedwideinterestfromresearchersacross thenations(Naaman,2008).Thepostcrackingstrengthofthecomposites islargerthanitsfirstcrackingstrengthforHPFRCC,thatis, σ pc σ cc (as shownin Fig.1.1).Anobvioustensionstrain-hardeningbranchwithmultiplecrackingisobservedintensionaftertheoccurrenceofthefirstcracking,andthemaximumpostcrackstressandstrain(σ pc, εpc)isachievedat theendofthestrain-hardeningbranch.Onlyonelocalizedcriticalcrack openswiththeincreasingdeformationwhileothercracksnarrowedin width,leadingtoastrain-softeningbranch.ComparedwithHPFRCC, thecrackofFRCislocalizedimmediatelyafterfirstcrackingwithoutmultiplecracksandstrain-hardeningbranches.
Engineeredcementitiouscomposite(ECC),asaspecialtypeofHPFRCC, wasdevelopedby V.Li(2019).ECCdemonstratesrobuststrain-hardening performanceaccompaniedbymultipleself-controlledcracks.Duetoits superiortensileperformance,ECChasreceivedworldwideattention. ECCusinglocalmaterialingredientshavebeensuccessfullyproducedin variouscountrieswiththeresearchefforts.AccordingtoGoogleScholarstatistics,approximately15,000papersonECCwerepublishedinthelasttwo decades.ThesedevelopmentsincludeECCdesigntheory,mixproportion andmaterialdesign,mechanicalproperties,constitutivemodels,energy properties,fiberinterfacialtreatment,durabilityandlong-termtensileproperties,multiscalesimulationoftheuniquetensilebehavior,andreinforced ECCstructuralmembersandtheirstructuralapplication.
ThisbookwillprovidecomprehensiveknowledgeontherecentdevelopmentofECCmaterialsandstructuresincludingitsapplicationfrom experimentalstudiestoadvancednumericalmodelingmethodsand techniques.
FIG.1.1 Typicalstress-straincurveofconcrete,FRC,andHRFRCC. Nopermissionrequired.
Differingfromthetraditionaltrial-and-errormaterialdevelopment methodology,ECCwasdesignedbasedonquantitativemicromechanics andfracturemechanicalmodel.TypicalECCcontainsamixtureof cement,flyash,sand,water,high-rangewaterreducer,andrandomlydistributedshortfibers.Severalkindsofmetallicand/orsyntheticfibers, suchaspolyvinylalcoholfiber(PVA),polyethylenefiber(PE),polypropylenefiber(PP)andsteelfiber(SF)areemployedtoproduceECC (namedasPVA-ECC,PE-ECC,etc.)withtheapplicationofmonoor hybridfibers.Steady-statecrackpropagationcanbeachievedthroughtailoringthepropertiesoffiber,matrixandinterfacebetweenfiberand matrix,usuallywithfibervolumeofnomorethan2%(V.Li,2019).In ordertoguaranteethestrain-hardeningandmultiplecrackingbehaviors oftheECCatcompositelevel,twocriteria,i.e.,strengthcriterionand energycriterionmustbesatisfied(Li&Leung,1992).Thestrengthcriterionstipulatesthatthetensilestressatthefirstcrack(σ ss)mustbelower thanthefiberbridgingstrength(σ o),whichistheprerequisiteforsteadystatecracking.Theenergycriterionrequiresthatthecracktiptoughness (Jtip),whichistheenergyconsumedbybreakingdowncracktipmaterial, shouldbelessthanthecomplementaryenergyoffiberbridging(J0 b),to ensurethedevelopmentofmultiplecracks.Withproperfibertailoring, veryhighductilitywiththemaximumstraincapacityrangingfrom3% to12%underuniaxialtensioncanbeachievedforECC,whichisseveral hundredtimesthatofconventionalconcrete(Yu,Wang,Yu,&Xu,2017). Further,amulticrackingpatternisobservedwithspacingbetweensaturateddistributedmultiplemicrocrackslessthan2mmwiththemaximum crackwidthcontrolledunder150 μmforPE-ECC(Yuetal.,2017)or60 μm forPVA-ECC(Li,Wang,&Wu,2001).
PVAfibershaverelativelyhightenacityandmodulus;theyareeasily dispersedevenlyinthematrixandthushavebeenusedwidelyinproducingECC(Table1.1).However,thehydrophilicpropertyofPVAfiberleads toaconsiderablystrongbondwiththematrix,resultinginprematurefiber ruptureeveninanormalstrengthmatrix.PVA-ECCusuallyhasacompressivestrengthof35–60MPaandatensilestraincapacityof2%–5%. TypicaltreatmentssuchasoilcoatingforPVAfiberandair-entraining agentadditionhavebeenadoptedtoreducethechemicalbondbetween PVAfiberandmatrix.PEfiberspresentrelativelyhightensilestrength andYoung’smodulusandhavebeenconsideredasproperreinforcement toproduceECCpossessinghighstrength(>60MPa)andhighductility (>2%)(Choi,Lee,Ranade,Li,&Lee,2016; Ding,Yu,Yu,&Xu,2018a, 2018b; Kesner&Billington,2005; Kesner,Billington,&Douglas,2003; Ranade,Li,Stults,Heard,&Rushing,2013; Yu,Yu,Dai,Lu,&Shah, 2018).ECCowningall-strengthgradeaccompaniedbyhighductility hasbeendevelopedsuccessfully(Dingetal.2018a,2018b).Theproperties
TABLE1.1 PropertiesofPVAandPEfiber. Fiber
Li(2019)
PEfiber2900–380020–2812–18100–1202–3 Yuetal.(2017)
PEfiber30002812.71003.1 Ranadeetal. (2013)
PEfiber2700121888 – Choietal.(2016)
Kesnerand Billington(2005) PEfiber
Kesneretal.(2003)
TABLE1.2 MajormechanicalandphysicalpropertiesofvarioustypesofECCs.
Compressive strength (MPa)
ofPVAandPEfibersusedindifferentreferencesaregivenin Table1.1 AsummaryofthecriticalmechanicalandphysicalpropertiesofECCis givenin Table1.2 (Yuetal.,2018)().
1.3ResearchanddevelopmentofECCstructurecomponentsand structuralapplications
Traditionalconcretestructuresoftenexperiencebrittlefailureandloss ofstructuralintegrityunderexcessiveloading.Thehightensileductility andfinemultiplecrackingofECCmaterialsareofgreatvalueinimprovingthedurabilityandintegrityofstructures.Extensiveresearchesonthe structuralperformanceofsteelbarreinforcedECC(R/ECC)structural elements,includingR/ECCbeams(Dingetal.,2018b; Xu,Hou,& Zhang,2012;Yuan,Pan,&Leung,2013),R/ECCcolumns(Li,Bai,Yu, Yu,&Lu,2019; Yuan,Chen,Zhou,&Yang,2018),R/ECCbeam-column connection(Qudah&Maalej,2014; Said&AbdulRazak,2016),R/ECC frameandenhancedwallsystemssubjectedtostaticand/orreversed
1.4ResearchanddevelopmentofnumericalmodelingmethodsforECCmaterialsandstructures
cyclicloading(Dehghani,Nateghi-Alahi,&Fischer,2015; Kesner& Billington,2005),havebeenconducted.TheperformanceofR/ECCstructuresisgreatlyenhancedintermsofload-carryingcapacity,deformability,andenergyabsorptioncapacity.Further,studiesonstructural performancesofECC-encasedsteelcompositeelementsundercompressiveandflexuralloadinghavebeenconducted,providinganimportant referenceforstructuraldesignandapplications.
TheoutstandingtensileperformanceofECC,alongwiththeeaseofexecutioninpractice,makesitverypromisinginabroadrangeofpractical applications(V.Li,2019).OnemajorapplicationofECCisusedasthelink slaborbridedecksystemforbridgestructures,whicharesubjectedtomillionsofcyclesofflexuralloadingfromtrafficloadsduringitsservicelife. Hence,itisimportanttostudytheflexuralfatigueperformanceofECCto ensuretheresilienceoftheinfrastructures.However,inthecurrentdesign guideline(JapanSocietyofCivilEngineers,2008),theexaminationofECC structuralperformanceagainstfatigueisrecommendedtofollowthestandardspecificationsforconcretestructures,whichlargelyunderminesthe fatigueperformanceofR/ECC.Somestudiesonfatigueperformanceof ECClinkslabs,overlays,andECClayer-enhancedconcretebeamshave beenconducted(V.Li,2019).Althoughthesteel-reinforcedbeamisone ofthemostpopularstructuralelementsinconstruction,thefatigueperformanceofsteel-reinforcedECCbeamshasnotbeenwellstudied.
Agedand/ordamagedRCinfrastructuresandbuildingsareundergoingdeteriorationandinurgentneedofstrengtheningorrehabilitation. Owingtoitsexcellenttensileproperty,crackcontrolcapacity,andcompatibilitywithsubstratematerialsaswellasnotableconstructability andeconomy,ECChassuccessfullybeenutilizedinrepairing,strengthening,andretrofittingforexistingstructurestoincreasethedurability andtheload-bearingcapacity,ortocompensateforthelossofloadcarryingcapacitycausedbysteelreinforcementcorrosion.
1.4Researchanddevelopmentofnumericalmodelingmethods forECCmaterialsandstructures
Withanever-growingcomputationalcapability,numericalmethods havebeenincreasinglyemployedtostudythemechanicalbehaviorof compositematerialsandthestructuralperformanceofstructuralmembersandsystems,savingtimeandresourcesrequiredforexperiments. Atthematerialscale,verylimitedcomputationalstudieshavebeen conductedtomodelthetensilebehaviorofECC,andthismightbedue tothenumericaldifficultiesanddemandsofcomputingresourcesin modelingcementitiouscompositeswithmulticracks(deBorst, Remmers,Needleman,&Abellan,2004).Spagnolianalyzedthefracture
propagationinECCundertensileloadingusingatwo-dimensionaltriangularlatticemodel(Spagnoli,2009).Kuniedaetal.analyzedthetensile fractureprocessincludingcrackwidthandcrackdistributionforthe SHCCusingathree-dimensionalrigid-body-springmodel(RBSM),in whichthesalientfeaturesofthemesoscalematerialstructuresuchas cementitiousmatrixaswellasthefiberwerediscretized(Kunieda, Ogura,Ueda,&Nakamura,2011).Althoughmesoscalemodelssuchas thelatticeandRBSMmodelcansimulatetheinitiation,propagation,accumulation,andcoalescenceofmicrocrackswithintheinternalmaterial structure,suchfine-resolutionmodelsgenerallytendtobecomputationallyintensive.
Themultiscalemodelingmethod,whichextractsthematerialpropertiesusingmultiplemodelsthatdescribematerialbehaviorfromdifferent lengthscales(microscale,lower-mesoscale,upper-mesoscale)andthus reducesthecalculationeffortataparticularscalelevel,hasreceived increasingattention.Ahierarchicalmultiscalemodelingapproachbased onarepresentativevolumeelement(RVE)modelhasbeenintroducedfor simulatingthetensilepropertiesofECC,andaseminumericalapproach wasexploitedtoimplementthemultiscalemodelingofmultiple-cracking tensilefracturebehaviorofECCwithimprovedaccuracyandefficiency.
Atthestructuralcomponentlevel,severalnumericalstudieshavebeen reportedtosimulatetheflexuralbehaviorofECCstructures.Toperform numericalsimulationofECCcomponents,theconstitutivebehaviorof ECCisessential.FortensilebehaviorofECCs,calibratedfromuniaxial tensiontests,thetrilineartensilemodelincludingthelinearelasticstage, strain-hardeningstage,andstrain-softeningstagehasbeenwidely adopted(Gencturk&Elnashai,2013).Forthecompressiveconstitutive behavior,ECChasbeenmodeledaslinearelasticmaterialsforsimplicity (Kesner,Billington,&Douglas,2003).Apolylinecompressivemodelwas developed,whichcouldexpresstheprepeakandpostpeakmechanical behaviorofECCunderuniaxialcompressionandbedemonstratedto bemorerealisticforthenonlinearanalysisofECCmaterials(Zhou, Pan,&Leung,2015).NumericalstudiesforECCstructuresareuseful forstructuralanalysis,servingasanaidfordesignpurposesandalsocomplementingexperiments.
1.5Layoutandcontentofthisbook
ThisbookwillpresenttherecentdevelopmentontheresearchofECCs inthreeaspects,i.e.,materialsdevelopment(SectionI),structuralapplication(SectionII),andnumericalmodeling(SectionIII).
SectionI onmaterialsdevelopmentwillshowcasetheexemplardevelopmentofECCmaterialstoachievespecifichighperformancebyusing
differenttypesoffibersincludingPVA,PE,PP,andhybridfibers.Itisnot theaimofthisbooktocoverallaspectsofmaterialsdevelopmentbutto showcasetheresearchinthisareabyusingafewexampleswitheachinvestigatingfromauniqueangle.Thiswillprovideone-stopcomprehensive informationaboutthedevelopmentofthematerialsandtheeffectofdifferenttypesoffibersontheperformanceofthefiber-reinforcedcementitiouscomposite.SectionIincludesfourchaptersfrom Chapters2to5.
Chapter2 presentsthedevelopedPVA-ECCusinglocaldunesand, aimingforareducedmaterialcostwhilemaintainingatensilestrain capacitythatcouldmatchtheductilityofsteelreinforcement commonlyusedinreinforcedconcretestructures.Athoroughstudyon themechanicalpropertiesofthedevelopedPVA-ECCunderstatic loadingwasconductedviaexperimentalandstatisticalinvestigations.
Chapter3 introducesthemechanicalenergyparametersand performance-baseddesignmethodofall-strength-gradePE-ECC.The basiccompressiveandtensileparametersandthecorresponding constitutivemodelswerestudied.Thestrainenergydensityandthe fractureenergyunderuniaxialtensionwereinvestigated. Aperformance-baseddesign(PBD)methodwasproposedtofacilitate thedesignationofPE-ECCaccordingtopracticalrequirements.
Chapter4 presentstheexperimentalinvestigationofmechanical propertiesandimpactstheperformanceofahybrid-fiberimpactresistantECCmaterialwithenergyabsorptioncapability.
Chapter5 presentsthehybridPE/steelECC(PE/S-ECC)which investigatedthebondbetweenrebarandPE/S-ECC.Adesignmethod fortheanchoragelengthofrebarinPE/S-ECCwasproposed.
SectionII onstructuralapplicationincludestherecentexperimental studiesonthestructuralperformanceofhigh-performancefiberreinforcedcementitiouscompositecomponentsincludingbeams,slabs, andcolumns.Theexperimentmethodsandmeasuringtechniquesdevelopedfromavaluablereference.Theresearchonstructuresprovides importantreferenceforstructuraldesignandinformthepractitioners aboutthepotentialbenefitsintheapplicationofthisnovelandhighperformancematerialsinengineering.Structuralstrengtheningusing thehigh-performancefiber-reinforcedcementitiouscompositeisalso included.SectionIIincludesfourchaptersfrom Chapters6to9.
Chapter6 presentsanexperimentalinvestigationontheflexuraland shearbehaviorsofsteel-reinforcedPVA-ECCbeamsunderstatic loadingandcyclicloading.Thestructuralperformances,includingthe load-deformationbehavior,ductilityratio,moment-curvature relationship,crackingbehaviorandstraindistributioninreinforcement bars,wereinvestigated.
Chapter7 presentstheresultsofacomprehensiveexperimentalstudy whereECCisemployedasanalternativetoconcretetoencasethesteel sectionandtherebypreventthestructuralinstabilitiesofthebaresteel beam.TheenhancementoftheflexuralbehaviorofECC-encasedsteel compositebeamswasdiscussedintermsofload-deformationresponse, failuremode,andstrainanalysis.
Chapter8 examinesthepotentialofusingECCasanalternative confinementmaterialforhigh-strengthconcrete(HSC).Theaxial compressivebehaviorofECCconfinedHSCwasinvestigated.The effectofECCencasementtocontroltheprematurecoverspallingand explosivebrittlefailureofHSCwasstudiedexperimentallytoevaluate theimprovementinitsfailurebehavior,postpeakductility,andenergy dissipationcapacity.
Chapter9 proposesaninnovativebasaltfabric-reinforcedECCsystem fortheflexuralstrengtheningoffire-damagedRCslabs.Anextensive experimentalprogramwasconductedtovalidatethisnewfabricreinforcedcementitiousmatrixsystem.TheuseofECCasa cementitiousmatrixwasfoundtobeanattractivesolutionastheslabs strengthenedusingECCachievinggoodresultsintermsofthecracking controlandultimateload,ductilityperformanceaswellasenergy dissipationcapacity.
SectionIII onnumericalmodelingincludestherecentdevelopmentof numericalmethodsandmodelingtechniquesonthemodelingoftheECC mixingprocess,mechanicalbehaviorofECCmaterials,andstructural behaviorofECCcomponents.Multiscalenumericalmodelingmethods andtechniquesontensilematerialpropertiesincludingtheunique strain-hardeningbehaviorofECCarepresented.Thenumericalmodel developedforsimulatingtheflowofself-consolidatingECC(SC-ECC) usingsmoothedparticlehydrodynamics(SPH)methodisalsopresented. FiniteelementanalysisofECCstructuresincludingECCbeams,slabs,and columnsarepresented.Thisbookpresentsasignificantcollectionof numericalmethodsandmodelingtechniquesandprovidesusefulreferencesforresearchersandengineerpractitioners.SectionIIIincludesseven chaptersfrom Chapters10to16.
Chapter10 reportsanumericalmodeldevelopedforsimulatingthe flowofself-consolidatingECC(SC-ECC)usingtheSPHmethod.The numericalmodelwasvalidatedusingstandardflowtests.Theresults werefoundtobeconsistentwiththeexperimentaldataobtainedfrom theliterature,providinginsightsintoSC-ECC’sflowbehavior.
Chapter11 presentsahierarchicalmultiscalemodelingmethodto characterizetheuniquetensilebehaviorofECCsubjectedtobothstatic andfatigueloading.Thismultiscalemodelingmethodhasaccounted foressentialcharacteristicfeaturesofECC,includingfiberbridging,
multiplecracking,andmaterialrandomness.Thismodelingmethod wasdemonstratedtobeabletosimulateECC’smultiple-crackingand tensilestrain-hardeningbehaviorunderstaticloadingaswellas bridgingstressdegradationunderfatigueloadingwithgreataccuracy.
Chapter12 introducesaconstitutivemodelforsteelfiber-reinforced concrete(SFRC)anditsdeterminationprocess.Numericalstudiesof SFRCundertriaxialquasistaticload,blastload,andprojectileimpact werethenconductedbyincorporatingtheconstitutivemodelinto LS-DYNAasausersubroutine.
Chapter13 reportsthe3Dfiniteelementmodelsfortheanalysisof structuralbehaviorofECCslabsunderstaticloading.
Chapter14 investigatesthestructuralperformanceoftheECCslab underimpactloadingnumerically.Anappropriatematerialmodelfor ECCmaterialsunderdynamicloadingwasproposed.Thesizeeffect, strainrateeffect,andthespecificequationofstateonthedynamic materialbehaviorwereinvestigatedusingthenumericalmodeling method.Theproposedmaterialmodelwasvalidatedvianumerical simulationoftheimpactprocessofahybrid-fiberECCslabstruckbya high-velocityprojectile.
Chapter15 presentsthedevelopmentofaFEmodelcorrespondingto theexperimentalinvestigationdescribedin Chapter7.Thedeveloped FEmodelwasvalidatedandtheparametricstudywascarriedoutto investigatetheinfluenceofdifferentmaterialandgeometric parametersontheflexuralbehaviorofECC-encasedsteelbeams.
Chapter16 presentsthedevelopmentandvalidationofaFEmodel correspondingtotheexperimentalinvestigationdescribedin Chapter8.
References
Banthia,N.,&Sheng,J.(1996).Fracturetoughnessofmicro-fiberreinforcedcementcomposites. CementandConcreteComposites, 18(4),251–269. https://doi.org/10.1016/0958-9465 (95)00030-5
Brandt,A.(2008).Fibrereinforcedcement-based(FRC)compositesafterover40yearsof developmentinbuildingandcivilengineering. CompositeStructures, 86(1–3),3–9. https://doi.org/10.1016/j.compstruct.2008.03.006 Choi,J.,Lee,B.,Ranade,R.,Li,V.,&Lee,Y.(2016).Ultra-high-ductilebehaviorofapolyethylenefiber-reinforcedalkali-activatedslag-basedcomposite. CementandConcreteComposites, 70,153–158. https://doi.org/10.1016/j.cemconcomp.2016.04.002
deBorst,R.,Remmers,J.,Needleman,A.,&Abellan,M.(2004).Discretevssmearedcrack modelsforconcretefracture:Bridgingthegap. InternationalJournalforNumericalandAnalyticalMethodsinGeomechanics, 28(7–8),583–607. https://doi.org/10.1002/nag.374.
Dehghani,A.,Nateghi-Alahi,F.,&Fischer,G.(2015).Engineeredcementitiouscomposites forstrengtheningmasonryinfilledreinforcedconcreteframes. EngineeringStructures, 105, 197–208. https://doi.org/10.1016/j.engstruct.2015.10.013.
Ding,Y.,Yu,J.,Yu,K.,&Xu,S.(2018a).Basicmechanicalpropertiesofultra-highductility cementitiouscomposites:From40MPato120MPa. CompositeStructures, 185,634–645. https://doi.org/10.1016/j.compstruct.2017.11.034
Ding,Y.,Yu,K.,Yu,J.,&Xu,S.(2018b).Structuralbehaviorsofultra-highperformanceengineeredcementitiouscomposites(UHP-ECC)beamssubjectedtobending-experimental study. ConstructionandBuildingMaterials, 177,102–115. https://doi.org/10.1016/j. conbuildmat.2018.05.122
Gencturk,B.,&Elnashai,A.(2013).NumericalmodelingandanalysisofECCstructures. MaterialsandStructures/MateriauxetConstructions, 46(4),663–682. https://doi.org/ 10.1617/s11527-012-9924-0.
JapanSocietyofCivilEngineers(2008). Recommendationsfordesignandconstructionofhigh performancefibrereinforcedcementcompositeswithmultiplefinecracks(HPFRCC).
Kesner,K.,&Billington,S.(2005).Investigationofinfillpanelsmadefromengineeredcementitiouscompositesforseismicstrengtheningandretrofit. JournalofStructuralEngineering, 131(11),1712–1720. https://doi.org/10.1061/(ASCE)0733-9445(2005)131:11(1712)
Kesner,K.,Billington,S.,&Douglas,K.(2003).Cyclicresponseofhighlyductilefiberreinforcedcement-basedcomposites. ACIMaterialsJournal, 100(5),381–390. Kunieda,M.,Ogura,H.,Ueda,N.,&Nakamura,H.(2011).Tensilefractureprocessofstrain hardeningcementitiouscompositesbymeansofthree-dimensionalmeso-scaleanalysis. CementandConcreteComposites, 33(9),956–965. https://doi.org/10.1016/j.cemconcomp. 2011.05.010.
Li,V.,&Leung,C.(1992).Steady-stateandmultiplecrackingofshortrandomfibercomposites. JournalofEngineeringMechanics, 118(11),2246–2264. https://doi.org/10.1061/ (ASCE)0733-9399(1992)118:11(2246).
Li,V.(2019). Engineeredcementitiouscomposites(ECC):Bendableconcreteforsustainableandresilientinfrastructure. Springer.
Li,L.,Bai,Y.,Yu,K.,Yu,J.,&Lu,Z.(2019).Reinforcedhigh-strengthengineeredcementitiouscomposite(ECC)columnsundereccentriccompression:Experimentandtheoretical model. EngineeringStructures. 198, https://doi.org/10.1016/j.engstruct.2019.109541. Li,V.,Wang,S.,&Wu,C.(2001).Tensilestrain-hardeningbehaviororpolyvinylalcohol engineeredcementitiouscomposite(PVA-ECC). ACIMaterialsJournal, 98(6),483–492. Li,V.C.,&Wang,S.(2002).Flexuralbehaviorsofglassfiber-reinforcedpolymer(GFRP)reinforcedengineeredcementitiouscompositebeams. ACIMaterialsJournal, 99(1),11–21. High performancefiberreinforcedcementcomposites.Naaman,A.(Ed.).(2008). Highperformanceconstructionmaterials:Scienceandapplications (pp.91–153).WorldScientific Publishing.
Qudah,S.,&Maalej,M.(2014).Applicationofengineeredcementitiouscomposites(ECC)in interiorbeam-columnconnectionsforenhancedseismicresistance. EngineeringStructures, 69,235–245. https://doi.org/10.1016/j.engstruct.2014.03.026
Ranade,R.,Li,V.,Stults,M.,Heard,W.,&Rushing,T.(2013).Compositepropertiesofhighstrength,high-ductilityconcrete. ACIMaterialsJournal, 110(4),413–422.(2013). http:// www.concrete.org/Publications/GetArticle.aspx?m¼ojs&pubID¼51685798
Said,S.,&AbdulRazak,H.(2016).StructuralbehaviorofRCengineeredcementitiouscomposite(ECC)exteriorbeam-columnjointsunderreversedcyclicloading. Constructionand BuildingMaterials, 107,226–234. https://doi.org/10.1016/j.conbuildmat.2016.01.001. Spagnoli,A.(2009).Amicromechanicallatticemodeltodescribethefracturebehaviourof engineeredcementitiouscomposites. ComputationalMaterialsScience, 46(1),7–14. https:// doi.org/10.1016/j.commatsci.2009.01.021.
Xu,S.,Hou,L.J.,&Zhang,X.F.(2012).Shearbehaviorofreinforcedultrahightoughness cementitiouscompositebeamswithouttransversereinforcement. JournalofMaterials inCivilEngineering, 24(10),1283–1294. https://doi.org/10.1061/(ASCE)MT.1943-5533. 0000505
Yu,K.,Wang,Y.,Yu,J.,&Xu,S.(2017).Astrain-hardeningcementitiouscompositeswiththe tensilecapacityupto8%. ConstructionandBuildingMaterials, 137,410–419. https://doi. org/10.1016/j.conbuildmat.2017.01.060
Yu,K.,Yu,J.,Dai,J.,Lu,Z.,&Shah,S.(2018).Developmentofultra-highperformanceengineeredcementitiouscompositesusingpolyethylene(PE)fibers. ConstructionandBuilding Materials, 158,217–227. https://doi.org/10.1016/j.conbuildmat.2017.10.040
Yu,K.,Li,L.,Yu,J.,Wang,Y.,Ye,J.,&Xu,Q.F.(2018).Directtensilepropertiesofengineered cementitiouscomposites:Areview. ConstructionandBuildingMaterials, 165,346–362. https://doi.org/10.1016/j.conbuildmat.2017.12.124
Yuan,F.,Chen,M.,Zhou,F.,&Yang,C.(2018).Behaviorsofsteel-reinforcedECCcolumns undereccentriccompression. ConstructionandBuildingMaterials, 185,402–413. https:// doi.org/10.1016/j.conbuildmat.2018.07.100
Yuan,F.,Pan,J.,&Leung,C.K.Y.(2013).FlexuralbehaviorsofECCandconcrete/ECCcompositebeamsreinforcedwithbasaltfiber-reinforcedpolymer. JournalofCompositesforConstruction, 17(5),591–602. https://doi.org/10.1061/(ASCE)CC.1943-5614.0000381
Zhou,J.,Pan,J.,&Leung,C.(2015).Mechanicalbehavioroffibre-reinforcedengineered cementitiouscompositesinuniaxialcompression. JournalofMaterialsinCivilEngineering, 27(1).
Mechanicalbehaviorofa polyvinylalcoholengineered cementitiouscomposite (PVA-ECC)usinglocal ingredients
DanMeng,TingHuang,Y.X.Zhang,andChiKingLee SchoolofEngineeringandInformationTechnology,TheUniversityofNew SouthWales,Canberra,ACT,Australia
2.1Introduction
Engineeredcementitiouscomposite(ECC),designedbasedonmicromechanicsandfracturemechanics(Li,2019),isaspecialtypeofhighperformancefiber-reinforcedcementcomposites(HPFRCC).ECCexhibits excellenttensilestrainhardeningbehaviorsimilartothatofductile metals,anditstensilestraincapacityisseveralhundredtimesthatofconventionalconcrete(Yang,2008).Moreover,ECCshowsmultiplemicrocrackingswithtightcrackwidth,indicatingimproveddurability.
ThemechanicalbehaviorofECCsisaffectedbymatrixpropertiesand fiberbridgingbehavior,whichdependonfiberpropertiesandinterfacial bondbetweenfibersandmatrix(Zhang&Li,2017).Differenttypesoffibers, includingpolyvinylalcohol(PVA)(Huang,2016; Lietal.,2001,2002),polyethylene(PE)(Choietal.,2016; Yuetal.,2017; Yu,Li,etal.,2018; Yu,Yu,etal., 2018),polypropylene(PP)(Takashimaetal.,2003; Yang&Li,2010),steel (Lietal.,1996),as-spunpoly(p-phenylene-2,6-benzobisoxazole)(PBO)fibers (Curosuetal.,2017),andhybridfibers(Maalejetal.,2005; Soeetal.,2013), havebeensuccessfullyemployedinECCswithdistinctmeritsanddemerits. TheECCreinforcedwithhighmodulusfibers,i.e.,steelfibersandPBOfibers, exhibitshightensilestrengthbutrelativelylowtensilestraincapacity
(Lietal.,1996).High-tenacityPPfiberswithenhancedfiberstrengthhave beenutilizedinPP-ECCandobtainedincreasingacceptance(Yang&Li, 2010),butthemaindisadvantageofPPfiberisitslowtensilestrength.On theotherhand,PEfibershavehightensilestrengthandelasticmodulus (Yuetal.,2017; Yu,Li,etal.,2018; Yu,Yu,etal.,2018).Thehydrophobicity ofPEfiberscouldresultinweakinterfacialbondingbetweenthematrix andPEfibers(D.Zhangetal.,2020).Thus,theyaremoresuitablefor high-strengthECC(D. Zhangetal.,2020).Withrelativelylowcost,sufficient tensilestrength,andwideproductioninthesyntheticfiberindustry,PVA fibershavebeenregardedasthemostpracticalreinforcingfiberofECC forfieldapplications(Huang,2016).
Aggregates,whichusuallyoccupyalargevolumefractioninthematrix, playanimportantroleincontrollingthedimensionalstabilityofcementitiousmaterials(Huang&Zhang,2014; Şahmaranetal.,2009).Aggregates withgrainsizeslargerthantheaveragefiberspacingmayhindertheuniformdispersionoffibersandincreasethematrixfracturetoughness,which willhaveanegativeeffectonthetensilestrainhardeningbehaviorofthe matrix(Şahmaranetal.,2009).Thus,microsilicasandwithamaximum grainsizeof200 μmwasemployedforECCsinmostofthepreviousstudies. TheeffectofaggregatetypeandsizeonthemechanicalbehaviorofPVAECCwasinvestigated(Şahmaranetal.,2009),anditwasfoundthatby increasingthevolumeofmineraladmixtures,boththegravelsandand thecrushedsandwithrelativelylargerparticlesizecouldalsobesuccessfullyadoptedtoproduceECC.However,theincreaseinaggregatesizehad anegativeeffectontensileductility,resultinginaslightlylowertensile straincapacitythanthepreviousPVA-ECCusingmicrosilicasand.
RecentresearchshowsthatthereisroomtoemployanECCwitha slightlylowertensilestraincapacityinECCstructuralmembers(Kim etal.,2004). Kimetal.(2004) foundthattheminimumrequiredtensilestrain capacityofECCforalinkslabapplicationwas0.8%anditwouldbe1.6% withasafetyfactoroftwo.Furthermore,anumericalstudyontheflexural behaviorofsteel-reinforcedECCbeamsindicatedthattheincreaseofthe ultimatetensilestraincapacity(from1%to4%)hadalmostnoeffecton theultimatemomentcapacity(Yuanetal.,2014).Itshouldbenotedthat withtherecenttrendofusingreinforcementbarswithahighyieldstrength (e.g.,600MPaorevenhigher)inreinforcedconcrete(RC)structures,aminimumtensilestrainof0.5%oftheECCmatrixisessentialinordertoensure thattheECCwillnotfailbeforethereinforcementbarsyield.However,tensilestraincapacitybeyond1%,whichfarexceedstheyieldstrainofeven high-strengthsteel( 0.5%),willonlyleadtoperformanceimprovement atthematerialorlocallevel(e.g.,controlofcracksizeandtheirnumbers) butgenerallywillnotimprovesignificantlyonthestructuralperformance ofRCstructuresinmostnormalstructuralengineeringapplications.Thus, anECCmatrixwithaslightlylowertensilestrainisdesiredforoptimal designandtotakefulladvantageoftheECCmaterial.
Inmanysituations,usinglocalsandasthemainconstructionmaterialis notonlyacost-savingoptionbutalsoagoodsolutionforthecomplex socialandenvironmentalproblemscausedbytheproductionofconstructionmaterial.Aquitenotablesituationistheimport/exportoffinesandas themainingredientforconcreteproductionintheSoutheastAsiaregion. Manycountriesimposeexportrestrictionsonriver/seafinesanddueto thesubstantialsocialandenvironmentalproblemsgeneratedduring extraction.Thus,theuseoflocalsandwouldbepreferredforlarge-scale applicationsofECCasitiscosteffective,readilyavailable,andenvironmentallysustainable.
Inthischapter,wepresentaPVA-ECCwedevelopedrecentlyusing localingredients,aimingforareducedmaterialcostwhilemaintaining atensilestraincapacitythatcouldmatchtheductilityofsteelreinforcementcommonlyusedinreinforcedconcretestructures.Athoroughstudy onthemechanicalpropertiesofthePVA-ECCunderstaticloadingwas conductedviaexperimentalinvestigations.MechanicalpropertiesincludingYoung’smodulus,compressivestress-strainrelationship,tensile stress-strainrelationship,andflexuralpropertiesarereported.Consideringtherandomfiberdistributioninthematrix,18dog-bonespecimens weretestedundercarefullyplanneduniaxialtensiontestssoastoobtain reliableresults.Digitalimagecorrelationtechniquewasemployedto monitorandconfirmthealignmentofthedog-bonespecimensduringtensiletesting.Inaddition,statisticalanalysiswascarriedouttoinvestigate theprobabilitydistributionofthebasicmechanicalpropertiesofthePVAECC.
2.2Materialsandspecimens
2.2.1Materialsandmixproportions
TheingredientsusedinthedevelopedPVA-ECCwerePortlandcement,flyash,localdunesand,water,high-rangewaterreducer(HRWR), andPVAfibers.Localdunesandwithanaveragegrainsizeof200 μm andamaximumgrainsizeof300 μmwasemployed.General-purpose cementfromCementAustraliaPty.Ltd.andASTMclassFflyashwere used.Thechemicalpropertiesofthecementandflyasharelistedin Table2.1.ThePVAfibersusedinthisstudy(asshownin Fig.2.1)were KURALONK-IIREC15fiberssuppliedbyKurarayCo.Ltd.,andtheir specificationsareshownin Table2.2.Apolymer-basedADVA142from GraceAustraliaPty.Ltd.wasemployedastheHRWR.ThemixedproportionsofthePVA-ECCareshownin Table2.3.Thecontentoffiberisby volumefraction,whileallothercomponentsarebymass.
2.MechanicalbehaviorofaPVA-ECCusinglocalingredients
TABLE2.1 Chemicalpropertiesofthecementandflyash.
FIG.2.1 ThePVAfibersREC15. Nopermissionrequired.
TABLE2.2 SpecificationsofPVAfibers(Huang,2016).
TABLE2.3 MixproportionsofthedevelopedPVA-ECC(Huang,2016).
CementFlyashSand/binderWater/binderHRWRFiber(vol.%) 1.01.20.36 0.3 0.012.2
2.2.2Specimenpreparation
Twocylinderspecimensof200mminheightand100mmindiameter werecastfortheYoung’smodulustest.Fivecylinderspecimens (Ø100 200mm)werecastfortheuniaxialcompressiontesttoobtain thecompressivestress-strainrelationship.Eighteendog-bonespecimens withacross-sectionalareaof36mm 20mminthereducedsectionanda gaugelengthof80mmwereusedfortheuniaxialtensiontest(Fig.2.2) (Huang,2016).Forthe4-pointbendingtest,6beamspecimenswith dimensionsof350mminlength,100mminwidth,and100mmindepth wereemployed.
ThePVA-ECCwasmixedinthelaboratoryusingamortarmixerwitha rotatingblade.First,thesolidingredients,includingcement,flyash,and sand,werefullymixedforafewminutes.Meanwhile,theHRWRwas addedintothemeasuredwatertoformaliquidsolution.Subsequently, theHRWRsolutionwasslowlyaddedintothemix.Afterthemixture becameuniformandconsistent,thefiberswereaddedgraduallyto achieveanevendispersion.Finally,alltheingredientswereblendedfor 5–10minuntilthoroughlymixed.Afterthemixingprocesswascomplete, thefreshmixturewaspouredintogreasedmoldsandvibratedonavibratingtableforafewminutes.Aftercasting,thespecimenswerecovered withlidsanddemoldedafter24h.Thespecimenswerethencuredata constanttemperatureof23°Candrelativehumidityof100%inacuring roomuntilthedayoftesting.Allthesespecimensweretestedatthe ageof28days.
Onedaybeforetheuniaxialtensiontest,thedog-bonespecimenswere takenoutofthecuringroom.3mmthickaluminumplatesweregluedon theendsofspecimensfortransferringtheloadfromthemachinetothe
FIG.2.2 DimensionsofthePVA-ECCdog-bonespecimen(dimensions:mm). From Meng,D.,Huang,T.,Zhang,Y.,&Lee,C.(2017).Mechanicalbehaviourofapolyvinylalcoholfibre reinforcedengineeredcementitiouscomposite(PVA-ECC)usinglocalingredients. Constructionand BuildingMaterials, 141,259–270. https://doi.org/10.1016/j.conbuildmat.2017.02.158
20 2.MechanicalbehaviorofaPVA-ECCusinglocalingredients
specimen(Soeetal.,2013; Tianetal.,2015).Toensurethatvalidresults wereobtainedfromtheuniaxialtensiontest,thespecimenhadtobeperfectlyalignedlongitudinallybeforetesting.Greatcarewastakentoattach thealuminumplatestotheendsofthespecimen.Towardthisend,center linesofaluminumplatesanddog-bonespecimensweremarkedtokeep thealignmentbetweenaluminumplatesandspecimens.Furthermore, thesameamountofgluewasusedforeachcontactsurface.Aftertheglue wasapplied,clipswereusedtohelpbondthealuminumplatesandspecimenstogether(Fig.2.3).Twoclampswereusedsoastopreventany movementofthealuminumplateswhentheclipswereapplied.Theclips wereremovedafterthecuringoftheglue. Fig.2.4 showsthedog-bone specimenwithaluminumplatesafterthepreparation.
FIG.2.3 Setupforapplyingaluminumplatesonthedog-bonespecimen. Nopermission required.
FIG.2.4 Thedog-bonespecimenwithaluminumplates. Nopermissionrequired.
2.3.1Uniaxialcompressiontest
Uniaxialcompressiontestswerecarriedoutoncylindersinaccordance withASTMC39(ASTM,2012)tostudythecompressivestress-strainrelationshipofthePVA-ECC.Thetestswereperformedusinga3000kNload capacityTecnotestmachine.Thetopsurfacesofthespecimenswerepreparedpriortotestingbyusingaconcretecylinderendgrinderinorderto obtainsmoothsurfacesandavoidstressconcentrations.Thetestswere conductedunderdeformationcontrolwithadisplacementrateof 0.05mm/min.Inordertomeasurethecompressivestrain,twolinearvariationdisplacementtransducers(LVDTs)wereattachedatthecenterof thecylinderwithagaugelengthof100mm.However,astheLVDTreadingscouldbeunstableinthepostpeakpartduetoextensivecracking (Zhouetal.,2015),anotherLVDTwasattachedtothebaseofthetestplate andwasusedtomeasurethedeformationduringthepostpeakstage.The testsetupisshownin Fig.2.5
2.3.2Young’smodulustest
Young’smodulustestswereconductedonthecylindersaccordingto ASTMC469(ASTM,2014).TwoLVDTsweresetuponeachsideofthe cylinders,asshownin Fig.2.6.Specimenswereloadedupto40%ofthe averagevalueoftheultimateloadobtainedfromuniaxialcompression tests,afterwhichthespecimenswereunloaded.TheloadingandunloadingwererepeatedfourtimestoobtaintheaverageYoung’smodulusofthe specimens.Aloadingrateof117kN/minwasapplied.Thereported Young’smoduluswastheaverageresultfromthelastthreeloadings. Theresultfromthefirstloadingwasnotincludedasthefirstloading wasprimarilyfortheseatingoftheLVDTs(Tekle,2017).Thelab-viewprogramwasusedtorecordthedataduringthetesting.
2.3.3Uniaxialtensiontest
Uniaxialtensiontestswerecarriedouttostudythetensilepropertiesof thePVA-ECCfollowingtheproceduresdescribedinthepreviousstudies (Soeetal.,2013; Tianetal.,2015).Thetestswereperformedusingthe100 kNShimadzuAutographAG-Xmachine,andthetestsetupisshownin Fig.2.7.Universaljointswereplacedatthetopandbottommachinegrips toallowfreerotationandensurethealignmentofthespecimenduring testing.Thedog-bonespecimenwithaluminumplatesatbothendswas connectedtotheuniversaljointthroughapinof10mmindiameter.
