a new performance-based mix design concept for co2-reduced concrete by the use of local raw mater

1、AnewperfmancebasedmixdesignconceptfCO2reducedconcretebytheuseoflocalrawmaterialsKraussH.W.1WachsmannA.1HermerschtW.1BudelmannH.1BegemannC.2LohausL.2HeidmannM.3WolterA.31.InstitutefBuildingMaterialsConcreteConstructionFir

2、eProtectionTechnicalUniversityofBraunschweigD38106BraunschweigGermany2.InstituteofBuildingMaterialsScienceLeibnizUniversityHannoverD30167HannoverGermany3.InstituteofNonMetallicMaterialsClausthalUniversityofTechnologyD386

3、76ClausthalGermanyAbstractThereductionofgreenhousegasisoneofthecentralchallengesinsciencetechnology.DuetothehugeshareoftotalCO2emissionscausedbytheproductionofPtlcementclinkerstrategiesfCO2reductionintheconcreteindustrya

4、reneeded.MostoftentheCO2reductionisaccomplishedbythesubstitutionofcementthroughotherreactivenonreactivematerials.Indertoensureaminimumtechnicalperfmancefacertainapplicationdifferentconcretemixoptimizationstrategiesarecon

5、ceivable.Onecentralissueistofindoutwhichofthenumerousconcretemixesissuitablefaspecificpurpose.AnimptantdrawbackofalmostallCO2–reducedconcretesisthatthetechnicalperfmanceisachievedbytheuseofclearlydefinedhighqualityrawmat

6、erials.Inmanycasesanoptimizationoftheparticlesizedistributionotheraggregatesproperties(e.g.particleshapeganiccontent)cannotberealizedbecauselocallyavailablematerialshavetobeusedduetoeconomicreasons.Meoverdifferentqualiti

7、esofcementSCMs(supplementarycementitiousmaterials)fillershavetobecopedwith.Inthispaperanewmethodfthedesignofconcretemixeswithverylowcementcontent(CO2–reduced“RedCarb”concrete)ispresented.Themixdesignconceptisbasedonthead

8、ditionofhighamountsofsuperplasticizerleadingtoamaximumdispersioneffectconsequentlytoameefficientuseofcementSCMsfillers.Asasecondeffectthewatercontent(watercementratio)canbereducedmarkedly.Therebythelossofstrengthdurabili

9、tyduetothelowcementcontentispartlycompensated.Anotherimptantfeatureofthemixdesignconceptistheimprovedwkabilityascomparedtoconcreteswithmaximumparticlepackingduetoahigherpastevolumetheoptimizationofthepastesvolumeratio.As

10、willbeshownthenewconceptleadstoverygoodmechanicalconcretepropertiesevenif80%ofthecementcontentisreplacedbymineraladditiveswithoutfurtherchemicaloptimizationofthesystem.Facomprehensivevaluationoftechnicalperfmancefurtherp

11、erfmancecriterialikedurabilitywkabilityareinvestigated.Duetoalackofabsolutelimitvaluesevenpropertestmethodstheperfmanceiscomparedtofivedifferentreferenceconcretemixestypicallyusedinpractice.ThedifferentCO2reducedconcrete

12、mixesareclassifiedintoonemeoftheperfmanceclassesbysatisfyingtheminimumperfmancecriteriaofeachclass.Finallythepossibleimplicationsfexistingconcretedesignengineeringmodelsareaddressed.Tothesebelonga)thedifferentwkabilityb)

13、themodifiedmechanicaldurabilitypropertiesc)theneedfnewmodifieddesignengineeringmodels.iginalityThiscontributiondisplaysanewmixdesignvaluationconceptaswellassomeimptantresultsfromacpatescientificprojectoftheTechnicalUnive

14、rsityofBraunschweigtheLeibnizUniversityofHannovertheClausthalUniversityofTechnologyfundedbytheNiedersachsenInstitutesofTechnologyboard(Germany).ThemaximumreductionofPtlcementclinkere.g.byaddingSCMsfillersisofgreatinteres

15、tfglobalsocietyindertoreducegreenhousegasemissions.TheperfmancebasedmixdesignconceptpresentedhereafterourknowledgeisthefirstmethodthatenablestheuseofSCMsfillerswithverydifferentpropertieswhileotherconceptsdemclearlydefin

16、edhighqualityrawmaterials.ThenewconceptenablestheuseoflocallyavailablerawmaterialssuchascementSCMsfillersaggregatesindifferentqualities.Consequentlythenewmethodbasicallyhasthepotentialfawldwideapplication.Thepresentedval

17、uationmethodenablesacombined“fair”assessmentofecologicaltechnicalconcreteperfmance.Allthestrategiesinstrumentsuseddevelopedwithintheprojectareinalignmentwithconcreteindustries’designers’contracts’intereststherefeareconve

18、nientfpracticalapplication.Keywds:concretemixdesignCO2reducedconcreteperfmancebasedSCMsfillers1Crespondingauth:Tel495313915487Fax495313915900Figure1Influenceofcementsubstitutionrateonmtarcompressivestrength:theroleofdilu

19、tioneffectfillereffecthydrationeffectalowerwatercontentafter(CyrM.etal.2006)modifiedOneoftheimplicationsofthegranulometricoptimizationstrategiesisthatthelowwatercontentthehighnumberofparticlecontactscauseaveryhighconcret

20、eviscositythusaverypowkability.Asaconsequencethoseconcretesarenotwellacceptedinpracticeduetotheincreasedefftftransptplacingcompaction.Anothercriticalpointistheclearlydefinedparticleacteristics(e.g.particlesizedistributio

21、nspecificsurface)thathavetobesatisfiedindertorealizeahighparticlepackingwhichisprerequisitefwaterreductionhighstrength.Thekeyproblemisthatthegranulometricallyoptimizedconcretemixesmostoftenarevalidonlyfthespecificrawmate

22、rialsusedfoptimizationwhereasothercomponents(e.g.withdifferentchemicalphysicalacteristics)exhibitalowerperfmance.Howeverrawmaterialswiththephysicalchemicalacteristicsrequiredffullgranulometricoptimizationarenotavailablei

23、neveryregion.ToovercomethisproblemstheauthssuggestanewperfmancebasedmixdesignconceptfconcretewithverylowOPCcontentthatwillbepresentedinthefollowing.2.NewmixdesignconceptfCO2reducedconcrete2.1BasicconceptAsalreadymentione

24、dCO2reduced(RedCarb)concretesshowdifferenttechnicalproperties(e.g.lowerwkabilitydifferentmechanicaldurabilityperfmance)ascomparedtonmalconcretewithOPC(referenceconcrete).Indertochoseanadequateconcretemixfaspecificconstru

25、ctiontaskplannerscontractsneedshtreliableinfmationontheecologicalperfmance(e.g.totalequivalentCO2emissions)onthemostimptanttechnicalproperties.OnekeyproblemftheapplicationofRedCarbconcretesinpracticeisthelackofafairvalua

26、tionmethodthattakesintoaccountecologicaltechnicalaspects.Suchavaluationmethodisalsopartofthenewconcretedesignconceptispresentedelsewheresee(BudelmannH.etal.2014)whereasthepresentarticlefocusesonthetechnicalaspects.Toachi

27、eveagoodacceptanceinpracticetheRedCarbconcreteshavetoaccomplishminimumtechnicalrequirementsinadditiontothelowCO2emission.Duetothedifferentcompositionsnotallofthetechnicalacteristicsofthereferenceconcretewillbematchedbyth

28、ecrespondingRedCarbconcrete.Howeverfaspecificconstructiontasksomeofthetechnicalpropertiesareindispensable.ThoseindispensablerequirementshavetobeverifiedvaluatedfeachindividualRedCarbmixincombinationwiththeecologicalparam

29、eters.Theprincipleisillustratedinfigure2.2.2ReferenceconcretemixesperfmanceclassesFcategizationdifferentperfmanceclasses(PC)werepredefinedseetable1.Ascanbeseennotonlyindostardoutdoconcretestructuresareaddressedbutalsodem