《土木工程专业英语 第2版》 课件 Unit8 The Greening of Engineered Cementitious Composites

Unit8TheGreeningofEngineeredCementitiousCompositesEnglishforCivilEngineering——Teacher：Prof.ZhengLuE-mail:luzheng111@（SchoolofCivilEngineering,TONGJIUNIVERSITY）Unit8TheGreeningofEngineeredCementitiousComposites8.1Introduction8.2ECCwithGreenBinder/Filler

8.2.1BenefitsofFlyAsh(FA)inECC

8.2.2CombiningFAandOtherAdditives8.2.3EngineeredGeopolymerComposites(EGC)8.2.4CountermeasurestoaPossibleShortageofFA

8.3ECCwithGreenAggregate

8.3.1NaturalSand8.3.2RecycledAggregate8.4ECCwithGreenFibers8.4.1ModificationinPVAFiber—DomesticorUnoiledPVAFiber8.4.2AdoptionofGreenFibers8.4.3FiberHybridization8.5SummaryandConclusions8.1Introduction

Engineeredcementitiouscomposites(ECC),sincetheirdevelopment,havebeenknownasaclassofcementitiousmaterialsuniquelypossessingsuperiorductility,strain-hardeningproperties,andmanyotheradvantagesovernormalconcrete.Forexample,ECCasafamilyofmaterialsattainstensilestraincapacityseveralhundredtimesthatofnormalconcrete.ThegoalofECCdesignistosuppressthewell-knownbrittlenessofcementitiousmaterials,infavorofmultiplemicrocracksundertension.工程用水泥基复合材料ECCstrain-hardening

应变硬化；

brittleness

脆性

；

microcrack微裂缝8.1Introduction

AmongtraditionalECCcompositions,ordinaryPortlandcement(OPC),polyvinylalcohol(PVA)fiber,andsilicasandserveasbinder,fiberreinforcement,andfineaggregate,respectively.Ithasbeenrecommendedthatthesethreekeyingredientsbesubstitutedbygreeneralternativesbecauseofrisingglobalconcernsformoreenvironmentalsustainabilityintheconstructionindustry.HighenergyintensityandreleaseofhighlevelsofcarbondioxideduringtheproductionofcementaswellasthecarbonintensityofthefinemanufacturedsandandthesyntheticoilcoatedPVAfiberhaveattractedmuchattentionfromresearchersandproducers,leadingthemtoengageindevelopingmoreeco-friendlyECCthroughappropriatematerialselection.ECC组分ordinaryPortlandcement普通硅酸盐水泥

；polyvinylalcohol聚乙烯醇

；silicasand硅砂

；ingredient成分

；eco-friendly环境友好型8.1Introduction

Inadditiontothegreeningintheproductionphase,theusephaseofECCalsostronglyinfluencesthesustainabilityofcivilinfrastructureduetothereducedmaintenanceneedsassociatedwiththedurabilityofthematerial.sustainability可持续性

；infrastructure基础设施

；durability耐久性

8.2ECCwithGreenBinder/Filler

Supplementarycementitiousmaterials(SCMs)havebeenrecognizedaspromisingingredientsforenhancingthegreennessand/orperformanceofcementitiousbindersinconcrete.Someareintentionallyproduced,whileothersarefromwastestreamsfromdifferentindustrialsites(e.g.,coal-firedelectricpowerplants,steelmills,andsilica-metalplants).ThesematerialsareconsideredvaluableduetotheirreducedenvironmentalimpactcomparedwithOPC.Inthecaseofwastestreammaterials,theiruseasSCMscontributestosustainablepracticeinotherindustriesbeyondcementproductionandconcreteconstruction.补充胶凝材料的优势binders粘合剂

；intentionally有意地

8.2ECCwithGreenBinder/Filler

8.2.1BenefitsofFlyAsh(FA)inECCProducedasacoalcombustionresidueinthermalpowerstations,FAisawell-knownsubstituteforOPC.TheadvantagesofFAincludethemitigationofheatreleaserate,thereductionofCO2

emissionsandloweringofembodiedenergy,andenhancementofworkability.Becauseofitslowerheatofhydration,cementitiousmaterialsusingFAexperiencelessthermalcrackingrisks,resultinginimprovementoflong-termdurability.FA的优点FA粉煤灰

；emission排放物

；workability和易性

；thermalcrackingrisk热裂风险

8.2ECCwithGreenBinder/Filler

8.2.2CombiningFAandOtherAdditivesSCMscombiningFAandotheradditiveshavebeenstudied,asameansoffurthergreeningECCwhilemaintainingductilityanddurability.Remarkably,FAisnotonlybeneficialasanOPCsubstitutebutalsopossessesfavorableinteractionswithothereco-friendlymaterials,asdiscussedbelow.FA与其他添加剂的组合additive添加剂

；substitute替代品

8.2ECCwithGreenBinder/Filler

1.HollowGlassMicrospheresandFAHollowglassmicrospheres(HGM),acontrolleddimensionhollowglassmaterialwithencapsulatedair,isconsideredasaneco-friendlyandeconomicalfillerinECCmixtures.HGMeffectivelylightenstheoverallmaterial,resultinginlowercompositedensityandinertia.Anotheradvantageofincorporatingthesphericalandsmooth-surfacedHGMinECCistheimprovedfreshproperties(e.g.,workability,flowability,compactability,ordispersionoffiber)ofthecomposite,whichislimitedbyalowwatertocementratioandthepresenceofmicrofibers.中空玻璃微珠HGMflowability流动性

；compactability密实性

；dispersion分散性

8.2ECCwithGreenBinder/Filler

2.MagnesiumOxide(MgO)andFAMagnesiumoxide(MgO)isapromisingcandidaterequiringlessenergythanOPCforthecalcinationprocess,whichinvolvestheheatingofinorganicmaterialstoremovevolatilecomponents.MgObindswithotheringredients(e.g.,fineaggregateorsyntheticfiber)inECCmixturewhenmixedwithaconcentratedsolutionofmagnesiumchloride(MgCl2),resultinginmagnesiumoxychloridecement(MOC).MgOcanserveasabinderinanotherwaythroughmineralcarbonation,whereCO2canbepositivelyutilizedtoactivatethebindingcapability.Inthiscase,incorporationofFA,aswellasMgOinECC,wasfoundeffectivetofurthersecuretheenvironmentalandeconomicadvantages,whileconsideringthemechanicalanddurabilityproperties.氧化镁calcination煅烧

；inorganic无机

；magnesiumoxychloridecement氯化氧镁水泥

8.2ECCwithGreenBinder/Filler

3.SolidWasteCeramicsandFASolidwasteceramicsderivedfromthemanufacturingoftablewareceramics,bathroomceramics,exteriorwallceramics,andfloortileceramicsraisegrowingconcernfortheenvironmentastheyarenotdegradableandarelikelytocontainharmfulsubstancesforland,air,orwaterresources.Attemptshavebeenmadetoutilizesuchwasteafterfabricationorcrushingandgrindingasbindersorascoarse/fineaggregateincementitiousmaterials.固废陶瓷ceramic

陶瓷

；

exterior煅烧8.2ECCwithGreenBinder/Filler

8.2.3EngineeredGeopolymerComposites(EGC)FAisoneofthemostimportantingredientsinengineeredgeopolymercomposite(EGC),whichisdistinctfromECCintermsofthemechanismofchemicalreactionforhardening.ThatisbecauseOPCcanbecompletelysubstitutedbyFA(orotherindustrialbyproductssuchasGGBFS)forOPCastheprimarybinder.Whilethebinderisdifferent,EGCandECCshareacommoncompositedesignbasisfortensilestrain-hardening.Besidesitseco-friendliness,welldesignedFA-basedEGCpossessessimilartensile/flexuralproperties(e.g.,strain-hardeningbehaviorsalongwithdecentstrengthandductility)andperhapsbetterdurability(e.g.,lowerdryingshrinkageandbetterresistancetofreeze-thaw/wet-drycyclesoracidattack),comparedwithECC,althoughthecompressivestrengthislikelylower.工程地聚合物复合材料EGCfreeze-thaw/wet-drycycles冻融/干湿循环

；acidattack酸侵蚀

8.2ECCwithGreenBinder/Filler

8.2.4CountermeasurestoaPossibleShortageofFAAspresentedabove,FAhasplayedanimportantroleinpartiallyreplacingOPCasagreenerbinderinECC.Thereis,however,agrowingconcernoverthesupplyofFAduetodecreasingrelianceoncoalcombustionasameansofelectricitygenerationacrosstheworld,especiallyintheUSAandCanada.Theuseoftypicallyinexpensivenaturalgasorotherrenewablesources(e.g.,wind,geothermal,orsolarpower)hasbeenincreasingandisexpectedtokeepgrowing,insteadofcoalcombustionsecondarilyproducingFA.ThistrenddoesnotimplyanurgentneedtoshiftfromFAtootherSCMsbecausemorethan40%oftotalFAproducedisnotbeneficiallyutilized.DespitesuchoptimismregardingtheavailabilityofFA,thereareincreasingstudiesonalternativematerialstoFA,assummarizedinthesectionbelow.FA短缺的对策renewablesource可再生能源

8.2ECCwithGreenBinder/Filler

1.RiceHuskAsh(RHA)Ricehuskash(RHA)isanagriculturalmaterialobtainedbyburningricehusk.Aftercombustion,itistraditionallydisposedofinwaterstreamsorlandfillsaswaste.IthasbeenfoundthatRHAbecomessimilartosilicafume(SF)initschemicalcompositionwhenburntatacontrolledtemperatureandcondition,therebyattractingtheattentionofresearchers.稻壳灰combustion燃烧；silicafume硅灰8.2ECCwithGreenBinder/Filler

1.RiceHuskAsh(RHA)BothexperimentalstudiesclarifiedthattheinclusionofRHArefinedtheporedistributionandincreasedthetotalporevolume.Specifically,theportionoflargecapillarypores(e.g.,greaterthan100nm)wasreducedandthatofmiddle-sizedpores(e.g.,50-100nm)wasincreased.Themodifiedporestructurewasfoundtoimprovethecompressivestrength,tensilestrength,andtensilestraincapacity,comparedwithconventionalECC.TheenhancementofcompressiveandtensilestrengthwasattributedtothehigherdensityofRHA-includedECCmixtureowingtothepackingeffectandfillereffectofRHA.ThefinerparticlesizeofgroundRHA(comparedwithFA)reducesphysicalvoids,anditslargersurfaceareacreatesmoreagglomerationsitesforcementparticles.Theimprovementofthetensilestrainpropertywasattributedtoanarrowercrackwidthandalargernumberofcracks,resultingfromanincreasedpseudostrain-hardening(PSH)index.porestructure孔隙结构

；pseudostrain-hardening伪应变硬化8.2ECCwithGreenBinder/Filler

2.Ground-GlassPozzolans(GP)Ground-glasspozzolans(GP),alsoknownasglasspowder,hasbeenusedtocompletelyreplaceFAinECCbinders.GPisobtainedbygrindingpost-consumptionglassandisconsideredenvironmentallyfriendlywithacarbonfootprintof0.063kgCO2/kg.Forcomparison,FAhasacarbonfootprintof0.01kgCO2/kgorless,whichisnearlynegligible.TheparticlesizeofGPiscontrolledfrom1μmto100μmequivalenttothefinenessofFA.GPwasfoundtodensifyECC,improvingcompressive,tensile(thefirstcrackorpostcrackstrength),andflexurestrengthatearlyages.Thiswasattributedtothepackingeffectandfiller/nucleationeffect.Theirregularly-shapedGPprovidesalargersurfaceareathanthespherically-shapedFAfornewpozzolaniccalciumsilicatehydrate(C-S-H)withalowCalcium/Silicaratioandhighalkalioraluminumcontent,whichendowsECCwithadenserstructure.玻璃粉alkali碱

8.2ECCwithGreenBinder/Filler

3.Limestonecalcinedclay(LCC)Limestoneandkaoliniteclayareabundantacrosstheworld.Limestonecalcinedclay(LCC)isproducedbyblendinglimestoneandcalcinedclay.Calcinedclay,whichisalowpuritymetakaolin,isobtainedbycalcinationoflow-gradekaoliniteclayat600-800℃,whereasOPCrequiresso-calledclinkerwhichisaprimaryingredientofOPCandisobtainedthroughcalcinationatupto1450℃,muchhigherthanthatformetakaolin.LCCdisplacespartofOPCtomake

limestonecalcinedclaycement(LC3).TheoverallenergyrequiredtoproduceLC3,andcorrespondingCO2emissionsaremuchless(e.g.,22%lessenergyconsumptionand20%-35%lessCO2emissions)thanthoseforOPC.石灰石煅烧粘土limestone石灰石

；kaoliniteclay高岭土；metakaolin偏高岭土；8.3ECCwithGreenAggregate

8.3.1NaturalSandOneofthemostefficientwaystoreducetheeconomicandenvironmentalimpactsinvolvedwiththeproductionandtransportofsandistoprioritizelocallyavailablematerialsformassiveinfrastructureprojects.Specificallyformarineorcoastalconstructions,seasandcanbeattractive.UseofseasandandseawaterfornormalECC(containingPVAfiberandFA),wasfoundtoslightlydecreasetensilestrainandtensilestrengthbutpromotecompressivestrengthandsettingtime.Alternatively,river-sand(RS)iseconomicalincomparisontoultrafinesilicasand(USS).天然砂ultrafinesilicasand超细硅砂

8.3ECCwithGreenAggregate

8.3.2RecycledAggregateApartfromnaturalaggregates,recycledaggregateoffersaplausiblegreenalternative.Constructionanddemolition(C&D)debrisisatypeofwastethatisnotincludedinmunicipalsolidwasteandincludesconcrete,asphaltconcrete,steel,woodproducts,drywallandplaster,brickandclaytile,andasphaltshingles.In2018,C&Ddebrisof540megatonswasproducedandalmost25%ofitwasdisposedofinlandfillsintheUnitedStates,accordingtotheU.S.EnvironmentalandProtectionAgency.Therehasbeenagrowinginterestinre-purposingthatlandfillwastebyusingitasrecycledindustrialaggregate,eventuallyaimingatacleanerandmoreeconomicalsubstitutionforUSS(e.g.,recycledconcreteaggregatecosts11timeslessthanUSS).再生骨料naturalaggregate天然骨料

；recycledaggregate再生骨料

；debris碎片8.4ECCwithGreenFibers

Polyvinylalcohol(PVA)isasyntheticpolymerthathasreceivedconsiderableattentioninawiderangeofapplicationsbecauseofitsexcellentmechanicalproperties,thermalstability,andchemicalresistance.Further,thefiberdiameter(about40μm)issmallenoughtoenhancefiber/matrixinterfacialsurfaceareacriticalforcompositeductilityinthehardenedstatebutlargeenoughtoenablegoodworkabilityinthefreshstate.PVAfiberwasfirstcommercializedin1950,withKurarayCo.,Ltd(Japan)astheworldwideproducer.TheuseofPVAfiberimportedfromJapaninothercountries,however,isexpensive,whichcanconstituteroughly50%~90%ofthetotalcostneededtoproduceconventionalECC.Furthermore,PVApossessesarelativelyhighembodiedcarbonandenergyfootprintasitisderivedfromvinylacetaterefinedfromfossilfuels.聚乙烯醇PVAsynthetic合成的

；thermalstability热稳定性

；vinylacetate醋酸乙烯酯8.4ECCwithGreenFibers

8.4.1ModificationinPVAFiber—DomesticorUnoiledPVAFiberThePVAfiberdesignedforECChasanoilcoatingthatintentionallyreducestheinterfacialfrictional/chemicalbondsbetweenthefiberandcementmatrixtoinducecontrolledfiberslippageforsuperiorductilityandstrain-hardeningbehaviorofECC.ForgreenerECC,thefocusinthispaper,somestudieshaveattemptedtousedomesticallyproducedunoiledPVAfiber.ThedomesticPVAfiberiseffectiveforreducingtheenergyinvolvedintransportationandisfourtoeighttimeslessincostthanthatofconventional(i.e.,importedandoil-coated)PVAfiber.Wangetal.investigatedECCreinforcedwithunoiledPVAfiberlocallyproducedinChina.Theauthorsconfirmedreducedcompositetensilestraincapacitybutretainedcompressiveandflexuralstrength.Possiblecountermeasuresmaybetoincreasethewatertocementratioorflyashreplacement(ofcement)ratio.Despitetheexpectedreducedcompressivestrength,theresultingECCmaybesuitableforcertainapplications.Otherattemptsinvolvinglocallyproducedoil-coatedPVAfiberresultedinECCswithcompetitivetensilepropertiesandotherswithrelativelylowtensileductility.PVA纤维的改性frictional/chemicalbond摩擦/化学键

；oil-coated涂油的

8.4ECCwithGreenFibers

8.4.2AdoptionofGreenFibersFromtheenvironmentalandeconomicpointsofview,somemanmadeandnaturalfibershavethepotentialtoreplaceconventionalPVAfiber.Theseincludepolypropylene(PP)fiber,polyethylene(PE)fiber,basaltfiber(BF),glassfiber(GF),andplantfiber,whichshallbeintroducedinthissection.绿色纤维polypropylenefiber聚丙烯纤维

；polyethylenefiber聚乙烯纤维

；basaltfiber玄武岩纤维

；glassfiber玻璃纤维

；plantfiber植物纤维

8.4ECCwithGreenFibers

1.Polypropylene(PP)FiberPolypropylene(PP)fiberischeaperandlessenergy-intensivethancoatedPVAfiberaswellasmoredomesticallyaccessibleinmanycountrieswherePVAfiberisimportedfromJapan.ThisalternativefiberhasgeneratedECCswithcomparableorhighertensileductilityordurabilityofPVA-ECC.SomePPfibersalsorequiresurfacetreatmentoverconcerninaging,relativelylowchemicalbonding(duetoitshydrophobicity),andtoimprovefiberdispersionduringmixingcausedbyitshighaspectratio(i.e.,lengthtodiameterratio).Toenhancetheirtensilestrength,PPfibershavehighdrawratiosresultinginalowerdiameter(e.g.,12μm)comparedtothatofPVAfibers(~40μm).Thissmallerdiameterenhancescompositetensilepropertiesbyhavingalargerfiber/matrixcontactsurfaceareabutalsoworsensworkabilityandfiberdispersionuniformity.hydrophobicity疏水性

；fiber/matrixcontactsurfacearea纤维/基体接触表面积

8.4ECCwithGreenFibers

2.HighModulusPolyethylene(PE)FiberPolyethylene(PE)fiberpossesseshighertensilestrength(tenacity),higherYoung’smodulus,lowerdensity,butslightlyhigherembodiedenergyandCO2(i.e.,perunitmass)thanthoseofPVAfiber.PEfiberendowsECCwiththemostoutstandingtechnicalperformancecapabilitiesbeyondPVAfiberbyachievinghightensile/compressivestrengthandstraincapacity.Tofullyutilizeitsextraordinarytensilestrength,surfacetreatmentsusingozone,silanecouplingagents,orgrapheneoxidehavebeenexploitedtoenhanceinterfacialbondinglimitedbyPE’shydrophobicity.Young’smodulus疏水性

；silanecouplingagents硅烷偶联剂

；graphene石墨烯

8.4ECCwithGreenFibers

3.BasaltFiber(BF)Basaltfiber(BF),aninorganicmaterialproducedbymeltingbasaltathightemperatures(approximately1200℃to1500℃),hasattractedattentionasahigh-temperatureresistant,relativelyinexpensive,chemicallystable,andeco-friendlyalternativetoPVAfiber.TherelativelyhighembodiedcarbonofBFwhenmeasuredonaunitvolumebasisisduetothehigherdensityofthismineralfibercomparedespeciallytolowdensitysyntheticfibers.ThisimpliesacarbonfootprintpenaltytoBFasfiberreinforcementperformanceinacompositeisbasedonvolumefractionratherthanweightfractionofitsingredients.Xuetal.reportedtensilepropertiesofBF-ECC.Whiletensilestrainhardeningwasachieved,thetensileductilitywaslimitedtolessthan1%.AmajoradvantageofBF-ECCisthatthemicrocrackwidthisextremelytight,typicallybelow10μm.Thistightcrackisassociatedwiththehighstiffnessofbasaltfibersanditsstrongbondtothecementitiousmatrix.玄武岩纤维

8.4ECCwithGreenFibers

4.GlassFiber(GF)Glassfiber(GF),mostlyderivedfromsilicateglasses,haslowermaterialsustainabilityindicatorswhencomparedwithPVAfiber.Forexample,theembodiedenergyandCO2emissionspervolumeofGFareroughlytwoandfivetimeslessthanthoseofPVAfiber.GFispronetocorrodeorbreakinhighalkalienvironments;however,mineraladmixture(e.g.,flyash,silicafume,orslag)canmitigatethehighalkalinitygeneratedbycementhydration,leadingtofurthergreeninginECC.Alkali-resistant(AR)glassfiberhasbeendeveloped.However,durabilityconcernappearstoremain.Theflexuraltoughnessandductilityaswellasmodulusofrupture(MOR),slightlyincreasedwithincreasingGFcontent.TheMORofGF-ECCincreasedwithtimeasaresultofincreasedmortarmatrixstrengthandfiber/matrixbondstrength.silicateglasses硅酸盐玻璃；mineraladmixture矿物掺合料；modulusofrupture断裂模量

8.4ECCwithGreenFibers

5.PlantFibersAsafamilyofnaturalfibers,plantfibersfromtheagriculturalsectorareconsideredsustainablesincetheyarebiodegradable,renewable,andtherebylesscarbon/cost-intensivethanmostman-madefibers.Themechanicalpropertiesofsuchnaturalfibers,whichvaryduetotheirvariouschemicalcompositionsandmicrostructures,aresubstantiallybelowthoseofPVAfiber,evenaftersomefiberprocessing(e.g.,shapingorheat/seawatertreatment).Plantfibersgenerallyhavelowerdensityandthermalconductivity.Thesepropertiesimplythatplantfiberscanplayacertainroleinnon-structuralelementssuchasbuildingcladdingorfacade,wherenosignificantloadingisexpected.Concernsoflowdurabilityofplantfibersinanalkalineenvironmentinthecementitiousmatrixcanbeaddressedtosomedegreebyeitherproperfibertreatmentormatrixmodification.biodegradable可生物降解的；facade立面

8.4ECCwithGreenFibers

8.4.3FiberHybridization1.PolyethyleneTerephthalate(PET)FiberandPVAFiberPolyethyleneterephthalate(PET)iswidelyusedinplasticproducts,especiallyinthefoodandbeverageindustry.AsignificantamountofPETisdisposedofinlandfillsaswasteatendoflife(e.g.,morethan75%of32megatonsofPETproductintheU.S.endedupinlandfillin2018),eventhoughtherecyclingofPEThasbeengraduallyincreasing.TheembodiedenergyandcostofthehybridPET-PVA-ECCshowedover40%reduction,whileCO2emissionwasreducedbymorethan50%ofthoseoftypicalECCwithPVAfiberonly.ThesegreencredentialscouldbediminishedifadditionalprocessingincludingsurfacetreatmentsareemployedtoimprovethePETfiber.ThesignificantneedtorecyclewastePETfromconsumerproductsprovidesimpetustofurtherinvestigationsofPETfiberandECCcontainin