20239FosteringaCircularEconomyandCarbonSequestrationforConstructionMaterialsWorkshopReport:AFocusSeptemberNISTNISTSP1500?2120239濟(jì)（CE）中，材料被設(shè)計成對環(huán)境影響較低，并在經(jīng)濟(jì)中盡可能長時間地保留，從而減CO2排放的重要貢獻(xiàn)者。正在努力將水泥和混CE。策略包括優(yōu)化混凝土使用并實(shí)現(xiàn)維修和再利用的基礎(chǔ)設(shè)施設(shè)計，以及CE、勞動力培訓(xùn)以及協(xié)調(diào)的監(jiān)管工作。美國國家標(biāo)準(zhǔn)與技術(shù)研究院（NIST）可以通過推進(jìn)CENISTSP1500-SeptemberTheconstructionsectorisincreasinglyfocusedonimprovingenergyandmaterialefficiencytoreduceitsenvironmentalimpact.Onepromisingapproachgainingtractionistheshiftfromatraditionallineareconomicmodel(extract,make,use,discard)toacircularmodel.Inacirculareconomy(CE),materialsaredesignedtohavelowerenvironmentalimpactsandareretainedintheeconomyforaslongaspossible,therebyreducingresourcedepletion,environmentalimpact,andwastegeneration,whilecreatingnewbusinessopportunitiesandjobs.Concrete,awidelyusedconstructionmaterial,isasignificantcontributortoCO2emissionsduetocementproduction.EffortsareunderwaytotransitionthecementandconcreteindustriestoaCE.Strategiesincludeinfrastructuredesigntooptimizeconcreteuseandenablerepairandreuse,aswellasadvancedmaterialdesignsuchastheuseofalternativecementitiousmaterials,improvedenergyefficiencyinproduction,andcarboncapturefromproductionandsequestrationinconcrete.However,challengeshinderthetransitiontoaCE,includingtheindustry'sestablishedtechnologiesandsupplychains,theneedfordemonstratedreliabilityofnewmaterials,andlackofatrainedworkforcecapableofdesigningandconstructingwithlow-carbonmaterials.Toovercomethesechallengesrequiresacollaborative,systems-levelapproach,withcleargoals,harmonizedmetrics,robustassessmenttools,standardsdevelopment,workforcetraining,andcoordinatedregulatoryefforts.TheU.S.NationalInstituteofStandardsandTechnology(NIST)cansupportthetransitiontoaCEbyadvancingmeasurementscience,developingdataresourcesandmodelingtools,participatinginstandardsdevelopment,andconveningnecessarystakeholderstofacilitatecollaborativeengagement.CircularEconomy,CarbonCaptureandSequestration,Low-CarbonCementandConcrete;CircularBuiltEnvironment.NISTSP1500-SeptemberTableofExecutive NISTSP1500-SeptemberTableofExecutive CementandConcrete:Use,Impacts,andDriversfor CurrentCircularEconomyEfforts,Challenges,andOpportunitiesfor CarbonSequestrationthrough Biomineralizationin CMUReuseand RecycledConcrete PotentialNISTActionItemstoFacilitateaCircularEconomyfor Beyond AppendixA.WorkshopAgendaand AppendixB.SummaryofInvited AppendixC.SlidoPoll AppendixD.RecycledConcrete AppendixE.TheScienceandStateofCarbonMineralizationin AppendixF.Biomineralizationin AppendixG.ACircularEconomyfor NISTSP1500?212023年9月CMU再利用和回收NISTBeyondConcrete.參考文獻(xiàn).BAppendixC.SlidoPoll D附錄E.混凝土中碳礦物化的科學(xué)與現(xiàn)狀.附錄F.混凝土中的生物礦物化.GNISTNISTSP20239國國家標(biāo)準(zhǔn)與技術(shù)研究院（NIST）循環(huán)經(jīng)濟(jì)、二氧化碳移除以及碳捕獲、利用與封存項C&DCE循環(huán)經(jīng)濟(jì)CMU混凝土砌塊CO2二氧化碳，在本報告中通常簡稱為CCSEoLEPDGt吉GHG溫室氣體GPPLCAPCR產(chǎn)品類別RCASCMsupplementaryCementitiousNISTSP1500-SeptemberTheauthorswouldliketothankalloftheworkshopspeakersfortheirwonderfulcontributions.Wewouldalsoliketoshareourappreciationforalltheparticipantswhocontributedtotheworkshopdiscussion.Wearegratefultoourreviewersfortheirvaluablecommentsandfeedbackonthisreport.Finally,wewouldliketothanktheCircularEconomyandCarbonDioxideRemovalandCarbonCaptureUseandStorageprogramsatNISTforfinancialsupport.Listof Constructionanddemolition Circulareconomy Concretemasonry Carbondioxide,generallyreferredtoas‘carbon’throughoutthisreport Carboncaptureandstorage Endof EnvironmentalProductDeclaration Greenhouse GreenPublicProcurement LifeCycleAssessment Productcategory Recycledconcrete NISTSP1500-SeptemberExecutiveMomentumisincreasingtoimprovetheenergyandmaterialefficiencyofourbuiltenvironmentandultimatelyreducetheenvironmentalimpactoftheconstructionsector.Oneapproachgainingtractionisthetransitionawayfromthetraditionallinear–extract,make,use,discard–economicmodeltowardamorecircularmodelwherematerialsenteringtheeconomyhavelowerenvironmentalimpactsthantheirtraditionalcounterpartsandareretainedintheeconomyforaslongaspossible.Acirculareconomy(CE)therebypreservesnaturalresources,reducesenvironmentalimpactsofproduction,lessensdemandforlandfills,andcreatesvalue,newbusinessopportunities,andnewjobs.Concreteisthepredominantconstructionmaterialusedgloballyduetoitsmanybeneficialpropertiesandavailability.However,theproductionofconcrete,particularlythecementbinder,isamajorgeneratorofCO2emissions.Duetotheenormousvolumeproducedannually,cementproductionisthelargestsingleindustrialemitterofCO2,estimatedtoaccountforapproximately8%to10%oftotalglobalanthropogenicCO2emissions[1,2,3].Asaresult,thereisexpandinginterestandeffortaimedattransitioningtoaCEforcementandconcrete.Variousopportunitiesforinnovationexistthatwillhastenthistransition,asdepictedinthehierarchyshowninFigureES-1.Changinghowwedesignmaterialsandinfrastructurehasthegreatestpotentialimpactonreducingtheembodiedcarbon(i.e.,thetotalcarbondioxideemissionsreleasedthroughoutthelifecycleofthematerialorstructure)andfacilitatingaCE.Thecarboncontentofnewconcretecanbereducedbyanumberofstrategies:a)loweringthecementcontentbyusingalternativeandsupplementarycementitiousmaterials(SCMs);b)improvingtheenergyefficiencyofcementproduction(e.g.,electrificationusingrenewableenergysources);andc)capturingcarbonemissionsfromcementproductionandutilizingit(alongwithotherindustrialCO2)inconcrete.Theembodiedcarbonofnewinfrastructurecanalsobereducedthroughoptimizeddesignthatreducesthedemandforconcrete,achievesimprovedservicelife,andenablesrepair,reuse,andrecycling.FigureES-1:Circulareconomyhierarchyprioritizingmosttoleastfavorablepathwaystoextendthelifeofmaterialsandinfrastructureandreduceembodiedcarbon.ThecementandconcreteindustrieshaveinvestedsignificantresourcesintoevaluatingapproachestoenablethetransitiontoaCE.Keyamongtheseareeffortsfocusedoncarboncaptureandsequestrationinconcrete,andadvancingtherecoveryandrecyclingofdeconstructedconcreteforuseinnewstructuralapplications.InJune2022theNationalInstituteofStandardsandTechnology

NISTSP20239且盡可能長時間地保留在經(jīng)濟(jì)中。因此，循環(huán)經(jīng)濟(jì)（CE）可以保護(hù)自然資源，減少生產(chǎn)CO2排放源。由于每年生產(chǎn)的巨大數(shù)量，CO2CO28至10%[1,2,3]。因此，人們越來越關(guān)注和努力推動水泥和混凝土向循環(huán)經(jīng)濟(jì)（CE）轉(zhuǎn)型。ES?1（SCMs）降低水泥含量；通過使用可再生能源進(jìn)行電氣化等方式提高水泥生產(chǎn)的能源效率；以及捕獲水泥生產(chǎn)的碳排放并將其（CO2）用于混凝土，可以降低圖ES?1混凝土中的碳捕獲和封存，以及推進(jìn)拆除混凝土的回收和再利用，用于新的結(jié)構(gòu)應(yīng)用。2022年6月，美國國家標(biāo)準(zhǔn)與技術(shù)研究院 NISTSP1500-September(NIST)heldavirtualworkshopconveningindustry,research,andgovernmentstakeholderstodiscussthestateofpracticeandscienceintheareasoflow-carbonandcircularcementsandconcreteinfrastructure,andidentifychallengesfacingtheiradvancement,whatisneededtoovercomebarriers,andpotentialNISTactionitemsthatcouldhelpmovetoaCEforcementandconcrete.ChallengesfacingtheadvancementofaCEforcementandconcreterangefromtechnical,cultural,andpolitical.Keychallengesidentifiedintheworkshopinclude:Theconstructionindustryiswell-establishedwithcapitalintensivetechnologieswithlonglifetimes,establishedsupplychains,andrelativelylowprofitmargins.Itisthereforetechnicallyandeconomicallychallengingtodeploynewformulationsandprocesses.Itisdifficulttobringnewmaterialsandprocessesintothemarketplaceuntiltheyhavefullydemonstratedcomparableorbetterreliabilityanddurabilityrelativetoincumbents.Currentstandardsandprocurementpolicies(often)precludetheadoptionofnewmaterials,orinclusionofrecycledconcrete.Lackofatrainedworkforcecapableofdesigningandconstructinginfrastructureusingnovellow-carbonmaterialsaswellasdeconstructingandreusingexistinginfrastructure.Thesequestrationofcarboninconcretelacksthequality-assuredmeasurementstoverifyhowmuchCO2isreliablycapturedthroughbothnaturalandacceleratedcarbonation.Biomineralization(i.e.,useofmicroorganisms)ofcarboninconcreteischallengedbylimitedinsitumeasurementandcharacterizationtechniquesaswellasunderstandingofthelong-termviabilityandsurvivalofmicroorganismsinconcrete(e.g.,forself-healingconcreteapplicationsandtotallynewmaterials).Toaddressthesechallengesandimprovethecircularityofthecementandconcreteindustryrequiresaharmonized,systems-level,collaborativeapproach.Severalopportunitiesforadvancementincludethefollowing:andpathways.CEpathwayscanalsobeappliedtoothercommonconstructionmaterialssuchasgypsum,steel,asphalt,glass,andwood.Whilethesematerialsmayhaveuniquechallengesassociatedwithimprovingtheircircularity,theyalsofacemanyofthesameindustry-widebarriersascementandconcrete.NISTcouldsupportmanyoftheneedsandopportunitiesidentifiedintheworkshop:thedevelopmentandhostingofdataregistriesandrepositories;advancementoftraceability,assessment,andmodelingtools;supportingthedevelopmentofstandards,specifications,andguidelines;aswellasappliedresearchincludingcharacterizationandmeasurementmethodsfornovelandrecycledconcretematerials.Furthermore,NISTiswell-suitedtoserveasaconvenerofthewiderangeofstakeholdersincludedintheconstructionsector,bothprivateandpublic,andacrossthesocialandtechnicaldisciplines.

NISTSP20239(NISTNIST率。因此，部署新配方和工藝在技術(shù)和經(jīng)濟(jì)上都具有挑戰(zhàn)性. 證明相對于現(xiàn)有產(chǎn)品具有可比或更好的可靠性和耐久性，否則很難將其引入市場. 的標(biāo)準(zhǔn)和采購政策（通常）禁止采用新材料，或包含再生混凝土. 使用新型低碳材料的設(shè)施以及拆除和再利用現(xiàn)有設(shè)施的訓(xùn)練有素的勞動力. 碳封存缺乏經(jīng)過質(zhì)量保證的測量方法來驗(yàn)證通過自然和加速碳化可靠捕獲了多少CO2.建立清晰、優(yōu)先的技術(shù)、環(huán)境、社會和經(jīng)濟(jì)目標(biāo)，以減少混凝土的隱含碳，并向循環(huán)經(jīng)濟(jì)轉(zhuǎn)型。 協(xié)調(diào)術(shù)語、指標(biāo)、方法、措施和數(shù)據(jù)，以支持決策策略框架。 推進(jìn)穩(wěn)健、統(tǒng)一透明的評估工具，如生命周期評估。 制定自愿性、基于共識的標(biāo)準(zhǔn)，以支持低碳水泥和混凝土的采用，包括設(shè)計標(biāo)準(zhǔn)和再生混凝土的使用。 協(xié)調(diào)監(jiān)管和市場杠桿，以推廣新技術(shù)。 CE性障礙。NIST究，包括新型和再生混凝土材料的表征和測量方法。此外，NIST NISTSP1500-SeptemberIntroduction Interestsandeffortstotransitiontowardmoreclimate-neutralconstructionmaterialsandpracticeshaverisensignificantlyinrecentyears.Constructingandusingthebuiltenvironment,whichincludesbuildings,roadways,bridgesandotherphysicalinfrastructure,accountsforasignificantportionofglobalenergydemandandassociatedgreenhousegas(GHG)emissions.Inaddition,decommissionedinfrastructureisasignificantsourceofsolidwaste.Throughadvancesinmaterialsscience,improvedmanufacturingapproaches,andmodifiedconstructionmethods,amoresustainablevisionofthefuturecanbecomereality.Afutureinwhichconstructionmaterialsareenvironmentallybenignwithasgoodorevenbetterperformance;whereconstructionproduction,quality,andthroughputaremoreefficientandhavelowerenvironmentalimpacts;andthecomponentsofthebuiltenvironmentaremaintainedandreusedattheendoftheirserviceliferatherthandiscarded.Forinstance,fastsettingcarbon-neutralconcretescanbeformulatedtobe3D-printedintostructuralelementsthatcanbemanufacturedinlarge-scaleroboticfabricationsystemsandundergomodularconstructionsuchthattheycanbedeconstructedforreuseinthefuture.Thiscircular,low-carbonvisioncanbereached;however,significantworkisneededtomakeitareality.Reducingtheenvironmentalimpactsofconstructionmaterialsnecessitatestransitioningtowardamorecirculareconomy(CE)–thatis,aneconomyinwhichatomsandmoleculesareretainedintheeconomyandoutofunwantedsinks,suchastheenvironmentandlandfills.Thisincludescarbonatoms,whichmustbekeptwithintheeconomybyreducingCO2emissions,extendingthelifeofexistinginfrastructureandmaterials,andcapturingandsequesteringCO2emissionsgenerated.Afewmaterialsareresponsibleforthemajorityofemissionsgeneratedbytheconstructionsector,andcements/concretesaretopamongthem,particularlyduetothesignificantvolumeofconcretemanufacturedannually.Infact,concreteisthesecondmostusedsubstanceintheworldafterwater,andconcreteconstructioncomprisesasubstantialproportionofthebuiltenvironment,anditsusewillcontinuetoincreasealongwithpopulationgrowthandglobaldevelopment[1].However,itsproduction,particularlythecalcinationoflimestoneinthecementproductionprocess,rendersitthelargestsingleindustrialgeneratorofCO2duetothesignificantvolumeproducedannually[1,2,3].Theneedthusexiststoimprovethecircularityofconcretebyextendingthelifeofcomponentsthroughincreaseddurability,reuse,andrecycling;loweringtheembodiedcarbonofcementandconcreteproduction;andsequesteringcarboninconcretethroughcarbonmineralization.TheU.S.NationalInstituteofStandardsandTechnology(NIST)hasextensiveexperienceinseveralareasthatcancontributetowardthiseffort.NISTcanhelptoadvancethemetrology,materialsscience,referencematerialdevelopment,dataregistriesandrepositories,standardsdevelopment,andlifecycleassessmenttoolsneededtofacilitateaCEforconstructionmaterialsgenerally,andcements/concretesinparticular.TobetterunderstandbarriersfacingthiseffortandapotentialroleforNISTtohelpovercomethem,NISTheldavirtualworkshopentitled“FosteringaCircularEconomyandCarbonSequestrationforConstructionMaterials”inJune2022.

NISTSP1500?2120239 GHG）排放的很大一部分。此外，退役基礎(chǔ)設(shè)施是固體廢物的重要來源。3DCO2排放、延長現(xiàn)有基礎(chǔ)設(shè)施和材料的使用壽命以及捕獲和封存水泥生產(chǎn)過程中產(chǎn)生的CO2[1]。然而，其生產(chǎn)，特別是水泥生產(chǎn)過程中石灰CO2[1,2,3]。因此，需要通這些領(lǐng)域可以為此項工作做出貢獻(xiàn)。NISTNIST克服這些障礙，NIST20226 NISTSP1500-SeptemberWorkshopTheone-dayvirtualworkshopincluded12expertspeakersfromacademia,nationallabs,andindustry,andbroughttogether≈230participantssimilarlyassociatedwiththeconstructionindustry.Whiletheworkshopprimarilyfocusedonthecircularityofconcreteincludingdecarbonizationandmineralization,somecontentfocusedongypsum.Speakersineachsessionpresentedthestateofresearchand/orpracticeonthesessiontopicaswellaspersistentchallenges.Recordingsofthepresentationswithpermissionbythespeakersareavailableonline[4].Thesessiontopicsincludedthefollowing:

NISTSP1500-September12≈230參與者。雖然研討會主要關(guān)注混凝土的循環(huán)性，包[4]。環(huán)節(jié)CarbonSequestrationCarbonSequestrationandAdvancesinCarbonReuseofConcreteCircularEconomyforBuildingSessionSessionInadditiontothespeakerpresentations,attendeeparticipationwasgarneredthroughtheSlidopollingapplication.ThefollowingpollquestionswereposedtoallparticipantsaswellasWhatarethemainchallengesfacingcarbonsequestrationandmineralizationinconcreteandhowcanstandardshelp?Whatmeasurementscienceisneededtosupportstandardsforreducingtheembodiedcarbonofconcrete?WhatmeasurementscienceisneededtosupportstandardsforconcretereuseandWhatarethemainchallengesfacingtheuseofrecycledaggregateandcementinnewconcreteandhowcanstandardshelp?HowshouldNISTprioritizenear-termmeasurementscienceneedsthatsupportstandardizationeffortsinsupportingacirculareconomyandreducingtheembodiedcarbonofconcrete?Thisreportsummarizesthekeytakeawaysfromtheworkshopincludingthestateofresearch/industry,aswellaspersistentchallengesandpotentialNISTactionitems.1Section2providesabackgroundontheproduction,use,andenvironmentalimpactsofcementandconcreteaswellasdriversforandadescriptionofaproposedCEforthesematerialsandproducts.Section3divesintocurrenteffortsunderwaytofacilitateaCEforcementandconcrete,includingcarboncaptureandsequestrationinconcretethroughcarbonationandbiomineralizationaswellasconcretereuseandrecycling.Challengesfacingthesepathwaysaredescribedalongwithneedstoovercomethosebarriers.Section4thenofferspotentialaction1Theviewpointoftheexpertsattendingtheworkshoparepresented,however,theymaynotreflecttheviewsofthebroadercommunityorNIST.

NIST4NIST NISTSP1500-SeptemberitemsNISTcouldpartakeintohelpaddresschallenges.Section5looksbeyondconcrete,usinggypsumasanexampleofothercommonconstructionmaterialswithgreatneedforincreasedcircularityyetwithitsownseriesofchallengesandopportunities.AseriesofAppendicesoffersmoredetailedcontentincludingtheworkshopagenda(AppendixA),overviewsofsessionpresentations(B),workshoppollresponsesinSlido(C),descriptionofrecycledconcreteaggregate(RCA)properties,performance,andresourcesforuse(D),thestateofscienceandpracticeforcarbonsequestrationviacarbonation(E)andbiomineralization(F),aswellastheproductionandcircularityofgypsumbuildingmaterials(G).CementandConcrete:Use,Impacts,andDriversforChangeConcreteisthe2ndmostusedmaterialonearth,ledonlybypotablewater.Therearemanyreasonsforthisasconcretehasmanyadvantagesasabuildingmaterial,including:Availability:rawmaterialssuchaslimestoneandclayaregeographicallyavailableacrosstheworldDurability:well-constructedconcretestructurescanlastfordecadeswithminimalFireresistance:concretedoesnotemittoxicfumes,smokeordripmoltenparticleswhenexposedtofireResilience:concretestructurescanwithstandamultititleofhazards(e.g.,fire,wind,water,mold,insects)anddisastersVersatility:concretecanbemoldedorformedintoanyshapewhennewlyThermalproperties:ConcretehasahighthermalmassandthuscanabsorbheatfromtheatmosphereinwarmweatherandreleaseitduringcoolerperiodsBecauseoftheseproperties,concretehasbeenusedasabuildingmaterialineveryregionoftheworldsinceancienttimes.Aspopulationscontinuetoincrease,sotoodoesthedevelopmentofinfrastructuresuchasroads,bridges,buildings,andwatertreatmentplants,mostofwhichutilizeconcrete.In2020,anestimated14billioncubicmeters(m3)ofconcretewasutilizedinnewconstructionglobally,withmorethan40%ofthatusedinresidentialinfrastructure[5].Todayabout55%oftheworld’spopulationliveincities,whereresidentialunitscomposeverticallyconstructed,multi-familystructures,predominantlymadewithconcrete.Projectionsestimatethatby2050closerto70%ofthepopulationwillliveinurbancenters,suggestingthedemandforconcretewillcontinuetoincrease[5].Atpresent,noothermaterialcanreplaceconcreteatthesamescale.Whiledemandfornewconcreteconstructionisincreasing,soistherateofdemolition.IncitiessuchasLosAngeles,California,thebuildingstockturnsoveronceevery30to40years[6].Thereasonforthisisnotnecessarilyduetostructuraldeficiency,butratherbecausethebuildingsareattheendoftheirdesigneduseorfunction.Assuch,asignificantvolumeofconcreteisdemolishedfromstructuresthattheoreticallyretainstheirdesignedfunctionalityandintegrity.

NISTSP20239NIST5系列附錄提供了更詳細(xì)的內(nèi)容，包括研討會議程（A）、各環(huán)節(jié)發(fā)言概述（B）、Slido（C）、再生混凝土骨料（RCA）的特性、性能和使用資源（D）、碳化固碳的科學(xué)與實(shí)踐現(xiàn)狀（E）和生物礦化（F），以及石膏建筑材料的生產(chǎn)行為和循環(huán)利用（G）。諸多原因，包括： 多功能性：混凝土在剛混合時可以被塑形或成型為任何形狀 大多數(shù)都使用混凝土。2020140（m3）的混凝40[5]55205070[5]。目前，沒3040[6]。其原因不一定是因?yàn)榻Y(jié)構(gòu)缺陷，而是因?yàn)榻ㄖ镆堰_(dá)到其 NISTSP1500-SeptemberNISTSP1500-SeptemberTheAmericanSocietyofCivilEngineers(ASCE)gradescivilinfrastructureonanA-Fscale(Arepresentingexceptional,fitforthefutureandFfailing/critical,unfitforpurpose)basedoncondition,capacity,resilience,andotherfactors.Accordingtotheirassessment,America’sinfrastructurescoresanoverallC-score.Dams,levees,androadsallscoredaD,whilebridgesscoredaC[7].Thatsaid,accordingtoU.S.FederalHighwayAdministration’s(FHWA)NationalBridgeInventory[8],currentlymorethan40%ofAmerica’sroughly620,000bridgesareover50yearsold,andabout43,000,orroughly7%ofthenation’sbridgeinventory,areconsideredstructurallydeficient.Concreteistheprimarymaterialofbridgeconstruction,whetherforsubstructure,superstructure,ordeck.ThissuggeststhatmanyU.S.bridgesmayneedtobereplacedintherelativelynearfuture,whichwillresultinthesignificantgenerationofconcretedebrisaswellastheneedfornewconcreteintheconstructionofreplacementinfrastructure.Traditionally,concreteelementsorstructuresfollowalinear–take,make,use,discard–path.AsdepictedinFigure1,eachstageoflifeforconcretehasenvironmentalinputsandoutputs,and,therefore,environmentalimpacts.Theextractionoftherawmaterials,includinglimestoneandclayaswellashigh-qualitysandsandaggregates,hasaneffectontheenvironmentandisenergyandwaterintensive.Further,localconsumptionofthesematerialscanleadtolocalresourceshortages[9].CementmanufacturingreliesonhighenergydemandsandisamajorsourceofGHGemissions.Theconstructionofconcreteelementsalsorequiresformworkandreinforcingsteel,whichhavetheirownenvironmentalcosts,namelyresourceuseandenergyconsumption.Well-constructedconcreteelementstendnottorequiresignificantmaintenance.Thedemolitionandend-of-life(EoL)managementofconcreteelementsisalsoenergyintensiveandresultsinthemassgenerationofsolidwaste.Naturally,eachofthesestagesrequirestransportation,whichcancomeatahighenvironmentalcostduetotheimmensemassandvolumeconsidered.Figure1:Environmentalimpactsof20239美國土木工程師協(xié)會（ASCE）根據(jù)狀況、容量、韌性等因素，對民用基礎(chǔ)設(shè)施進(jìn)行C[7]。然而，根據(jù)美國聯(lián)邦公路管理局（FHWA）[8],，目前美國62405043,0007%，被認(rèn)為結(jié)構(gòu)缺陷?；炷潦菢蛄菏┕さ闹饕牧?，無論是用于基礎(chǔ)結(jié)構(gòu)、上部[9]。水泥制造依賴于高能源需求，是的拆除和報廢（EoL）管理也是能源密集型的，并導(dǎo)致大量固體廢物的產(chǎn)生。當(dāng)然，每NISTSP1500-SeptemberButperhapsthemostrecognizedenvironmentalimpactofconcreteisthecarbondioxide(CO2)emissionsresultingfromtheproductionoftraditionalPortlandcementclinker,acomponentofcement.Inthisprocess,calciumcarbonate(i.e.,limestone)alongwithasilicasourceisheatedinarotarykilnupto1,450°C(~2,642°F)toinduceaseriesofcomplexchemicalreactionsultimatelyresultingintheproductionofcalciumsilicateclinkernodules,withCO2releasedasaby-product[3].NotonlydoesthisprocessresultinthedirectemissionofCO2,buttheprocessitselfnecessitatesaheavyuseoffossilfuelstoreachthenecessarytemperaturesinthekiln.Fossilfuelcombustionisestimatedtoberesponsibleforabout40%oftotalCO2emissionsincementproduction,someofwhichisforgrindingtheclinkerintopowder,whilelimestonedecompositionduringcalcinationisresponsiblefortheremaining60%[1].Onaverage,about900kilograms(kg)ofCO2isemittedforevery1,000kgofcementproduced[10].In2020,roughly4.2billiontonnesofcementwereproduced,thereforeamountingtotheemissionofabout3.8billiontonnesofCO2[5].Assuch,duetotheenormousvolumeproducedannually,cementproductionisconsideredthelargestsingleindustrialemitterofCO2andisnowestimatedtoaccountforapproximately8%to10%oftotalanthropogenicCO2emissions[1,2,3].ThetotalamountofCO2emittedisanticipatedtorisesteadilyasglobaldemandforconcreteincreases[11].Furthermore,thisvalueincreasessomewhatwhenthefullproductionofconcreteisconsideredsuchasaggregateextractionandprocessing,transportandplacing,andtheproductionanduseofreinforcementsteel.Concretestructuresarecontinuouslydecommissioned,generatingasignificantamountofwaste.AccordingtotheU.S.EnvironmentalProtectionAgency(USEPA)[12],in2018roughly600milliontonsofconstructionanddemolition(C&D)debrisweregeneratedintheU.S.fromconstruction,renovation,anddemolitionactivitiesforbuildings,roads,bridges,andotherstructures.Morethan90%oftheC&Ddebrisgeneratedin2018wastheresultofdemolitionactivitiesalone,theremaindergeneratedbyconstructionwaste.AsdepictedinFigure2,C&Ddebriscomprisesavarietyofmaterials,withconcreteaccountingforthelargestportionatnearly68%.Figure2:Materialcompositionofthe~600milliontonsofC&DdebrisgeneratedintheU.S.in2018(perUSEPAdata,[12])

NISTSP1500-20239（CO2）排放，而硅酸鹽水泥熟料是水泥的組成部分。在這個過程中，碳酸鈣（即石灰CO2[3]。這個過程不僅會導(dǎo)致CO2的直接排放，而且本身需要大量使用化石燃料來達(dá)到窯內(nèi)所需的溫度。據(jù)估計，化石CO240%，其中一部分用于將熟料磨成粉末，而煅燒60[1]1,000kg900kgCO2[10]。20204.23.8CO2[5]的排CO2排放源，CO2810[1,2,3]。隨著全球?qū)炷列枨蟮脑黾?，CO2[11]。此外，當(dāng)考慮混凝土生產(chǎn)的全部過程時，如骨料混凝土結(jié)構(gòu)持續(xù)被報廢，產(chǎn)生大量廢棄物。根據(jù)美國環(huán)保署（USEPA）[12],在2018（C&D）垃圾約為62018C&D902C&D68%。22018~600C&D（USEPA[12] NISTSP1500-SeptemberIntheU.S.,concretedebrisisusedasrecycledconcreteaggregate(RCA)inpavementsubbase(i.e.,road-base),non-structuralbackfill,ordisposedofinlandfills[12,13,14].AccordingtoU.S.EPAdata,in2018,over300milliontonsofconcreteC&Ddebriswasutilizedinsomeform,while71milliontonswasdiscardedinU.S.landfills[12].AsdiscussedfurtherinSection3.2.2,mostRCAisnotutilizedinstructuralapplications,andtherebyisnotusedasanaggregatereplacementinnewconcrete,whichwouldhaveincreasedenvironmentalbenefitsbyreducingthedemandforandtransportationofvirginhigh-qualityaggregates.Despiteitspotential,usingRCAinnewconcreteisnotyetcommonpracticeduetoconcernsovervariationinmechanicalpropertiesanddurabilityperformance[13,15,16,17]. DriversforMomentumisincreasingtoimprovetheenergyandmaterialefficiencyofourbuiltenvironmentandultimatelylessentheenvironmentalimpactoftheconstructionsector.Architects,designers,engineers,buildingowners(e.g.,customers),policymakers,andusersofcivilinfrastructureareincreasinglycallingforinfrastructureconstructedwiththeenvironmentinmind,withreducedGHGemissionsandimprovedrecoveryattheendofservicelife.Economicsareanotherfactordrivingashifttowardcircularity.Theeasyavailabilityofvirginmaterials,particularlyvirginaggregates,closetourbanareasisdecreasingandthusthecostofthesematerialsisrising,inparticularthetransportationcosts.TheNewYorkDepartmentofTransportation(DoT)reportedlyspends$1.45millioneveryyeartodisposeofwasteconcrete[18].Recyclingthiswastestreamintonewinfrastructurenotonlysavesondisposalcosts,butalsoreducestheneedforvirginmaterials.GreenPublicProcurement(GPP)programsarealsodrivingeffortstoreducetheenvironmentalimpactsofconcreteandtoprovidestrongsignalformarketdemandtohelptransitiontheindustry.Publicprocurementisprimarilycarriedoutbylocal,state,andfederalgovernments,whichuseGPPsinthepursuitofstrategicobjectives.Inthissense,GPPinitiativesutilizethepurchasingpowerofpublicauthoritiestoprocuregoodsandserviceswithreducedenvironmentalimpact,andmayincludemeasurestoincentivizematerialefficiency,circulareconomy,andtheuseoflow-carbonmaterials[19,20].Theactualaccuratemeasurementof“reducedenvironmentalimpact”isacurrentresearchquestion.Thisapproachcanstimulatethemarketforthesematerialsbyinfluencingtheprivatesectorandrewardingbusinessesthatprovideproductsorserviceswithlowerenvironmentalimpact[21].Intheconstructionsector,GPPmeasurescanbeattheprojectortheproductlevel;theformerincentivizingenvironmentalimpactreductionsoftheov