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ThemiddlerouteofthesouthtoNorthWaterTransfetProjectisanimportsntinfrastructureprojecttooptimizetheallocationofwaterresourcesandsolvethewatershortageinthenorthofChina.Itplaysastrategicroleinrealizingthesustainabledevelopmentofthenorthernregion・Theprojectis1273.4km,ChinaisfollowingtheYangtzeRiverThreeGorgesProjectafteranotherlargewaterconservancyproject,projectoflargescale,complexgeologicalconditions,thestructureofbuildingcomplex,thenewpumpingstations,channels,largeaqueduct,invertedsiphonconcretebuildingengineeringmorethan1000.Thehugevolumeofconcrete,concretetechnicalrequirementsfordifferentkindsofbuildings,concretestrengthgrade,fromCIOtoC60thelowestlayerofconcrete,prestressedconcretePCCPpipelineproject,fromnormalconcretetothepump,selfcompactingconcrete,thesetechnicalrequirementsneeddifferenttypesandvarietiesofadditives,inordertomeettheneedsofdesignandconstructionthe・Therefore,howtoselectandapplytheadmixturereasonably,improvethedurabilityofconcreteandguaranteetheconstruct!onqualityoftheprojectwilldirectlyaffectthesafeoperationandservicelifeofthemiddlerouteproject・ThispaperbrieflyintroducestheapplicationofpolycarboxylatesuperplasticizerinthePCCPprojectofthemiddlerouteofSouthtoNorthWaterDiversionProject,andprovidesreferenceandreferenceforsimilarprojects・PCCPpipelineengineering1.projectbriefintroduction:theBeijingsectionoftheMiddleRouteProjectofthesouthtoNorthWaterTransfer Projecthasatotallengthof80.4km,ofwhichthetotallengthofthePCCPprojectis56.359km,andthedoublerowDN4000prestressedsteelcylinderconcretepipe(PCCP)isusedforcarryingwater・Themaximumworkingpressureofthepipelinedesignis0.8MPa,themaximumdesignsoildepthis10m,andthecoreconcretestrengthdesigngradeisC50toC60,whichbelongstohighstrengthandhighperformanceconcrete,andthetotalconcreteamountisabout420thousandm3.PCCP(PrestressedConcreteCylinderPipe)istheabbreviationofEnglishprestressedconcretecylinderpipe,isinthecoreofprestressedsteelwirewindingsteeldrumconcretepipe,waterpipeandspraytheprotectivelayerofcementmortarmade・Itisacollectionofsteelandprestressedreinforcedconcretepipehastheadvantages,alsohasitsuniquecharacteristics,hastheadvantagesofwideapplicationrange,goodseismicperformance,lowoperationcost,convenientinstallation,noWaterLeakage,longservicelife,canbewidelyusedinlongdistancewaterdiversionandwaterdiversionproject,citywatersupplyengineeringetc・・Beforethewaterdiversionproject,thelargestdiameterofPCCPapplicationinChinafor3.6m,theprojectisthelargestofShanxiWanjiazhaiYRDP(diameter3M,length5m,43.25km,thelayingdistance)engineeringdifficultyisthemostinAsiaatthattime・TheBeijingsectionofthemiddlerouteofthesouthtoNorthWaterTransferProjectselectsthe4moftheinnerdiameterandthelengthof5mPCCPasthepipeofwaterdelivery.ItisthelargestPCCPprojectinChinaandeveninasia・2.technicalproblemstobesolvedControlthetotalalkalicontentinconcrete・AccordingtotheformulationofSouthNorthWaterDiversionProjectConstruction ManagementBureau"thepreventionofalkaliaggregatereactioninconcreteengineeringtechnicalregulations",thePCCPprojectisaclassIIIhumidenvironmentengineering,thetotalalkalicontentinconcreteshallnotbegreaterthan2.5kg/m3,andshouldnotusealkaliactiveaggregate・Thisrequirementhascertaintechnicaldifficultyforhigh-strengthconcreteofthehigheststrengthgradeofC60.Earlystrengthrequirements・Havingacertainearlystrengthisnotonlythestandardrequirement,butalsotheactualneedsoftheproject・AccordingtotheprovisionsofChinaandtheUnitedStatesAWAC301,PCCPfi.1amentstrengthforthedesignofconcretestrengthof70%,ifnotmeettherequirements,youneedtemporarystoragetotherequiredwindingstrength・4mwithinnerdiameterofPCCPbelongstosuperlargecaliberpipe,anditneedsalotofspaceforstorage・Therefore,oneofthekeyfactorsthatrestricttheproductioncycleistheearlywindingstrengthandsitefactor・Accordingtotheregulations,PCCPcanbesteamcured,butthesteamcuringtemperatureshallnotexceed52degreescentigrade・Therefore,thetwoaspectsoftherestrictions,thesouthtoNorthWaterDiversionProjectPCCPrequirementsofthesteamaftertheconcretemeetstherequirementsofwindingstrength,inordertomeetthesiteturnoverandtimelycompletionoftheprojectconstructionneeds・Workabilityrequirements・ThelargediameterPCCPpipewithverticalpouring,waterdiversiontubecorePCCP，sthicknessof380mm,high5m,singlepipeconcreteisabout24m3,acasting,sotheconcretehasgoodworkability,Toensurethatthevibrationcompactingconcretesurface,nopits,withoutsegregationandbleedingandlaitance,thusaffectingtheappearanceandperformanceofconcretesocket,sotheconcreteslumpcontrolin5cm、7cm,smalllossandslump・Crackresistancerequirement・PCCPisaprestressedconcretecompositestructure, strictcontrolofconcretecrack,howtoimprovethecrackresistanceandvolumestabilityofconcrete,reducethetemperatureshrinkagestress,improvetheyieldofpipesisoneofthekeytechnicalproblemsthatmustbesolvedintheprocessofmanufacturing・Experimentalstudy1.concreterawmaterialsCement:inordertomeetthespecifiedrequirementsofthetotalalkalicontentinconcrete,thealkalicontentofcementislessthan0.6%.TheexperimentselectstheTaihangMountainprospectinBeijingandthe042・5PortlandcementproducedbytwocementplantsinTianjintorevitalizetheP.ThetestresultsshowthatthealkalicontentofcementinTaihangprospectis0.58%,andthatofTianjinis0.44%,whichmeetsthetechnicalrequirementofalkalicontentoflowalkalicementby0.6%.Flyash:twogradesIash,themeasuredalkalicontentis1.34%and1.11%.Gravelaggregate:theactualnaturalriversand,thelargestparticlesizeof25mmlimestoneartificialrock・Admixture:additivevarietiesselectedwithlowdosage,highwaterreducingrate,lowshrinkage,highslumpandmanyotheradvantdgesofpolycarboxylatesuperplasticizer,toreducetheintroductionofeffectivealkaliinconcrete,andreduceconcreteunilateraluseofwater,therebyreducingtheamountofcementitiousmaterials,reducingtheeffectivealkalicontentintroducedbycementandflyashetc・・Atthesametime,itisalsorequiredtoadapttothe steamcuringconcreteprocessandhashigherearlystrength,sotheoptimizationoftheadmixtureisveryimportant.Testswereconductedon8batchesofpolycarboxylateadmixturesatdifferentsuppliers・Theresultsshowthatseveralearlystrengthpropertiesandcuringpropertiesofpolycarboxylatesuperplasticizerintherecommendeddosageexhibitedstrongthixotropyandcohesiveness,mixingtime,mixingandformingartificialturningdifficult,therearealsosomeadditivesandeasyproblems・Therefore,aftertheadjustmentandoptimizationofpolycarboxylatesuperplasticizer,theselectionof1manufacturersofwaterreducingagentswascarriedouttooptimizethemixingratioandtest・2.optimizationtestofconcretemixtureratioThestrengthgradeofPCCPcoreconcreteisdividedinto3grades:C50,C55andC60accordingtodifferentworkingpressureandenvironment・Thestrengthguaranteerateis95%,standarddeviationis5.OMPa,andthemixingstrengthis58.2MPa,63.2MPaand68.2MParespectively.Theparametersofmixtureratioincludeaggregategradation,optimumsandrate,optimumdosageofadmixture,amountofflyash,watercementratio,etc・・Thecontentofflyashhasconsideredthelimitationofthemaximumamountofflyashandtheinhibitioneffectofaggregatealkaliactivity.Themaximumcontentofflyashis20%.Theoptimumselectionofadmixtureistheworkab订ityoffreshconcrete,andtheoptimumdosageofadmixtureis1.1%(solidcontent20%)・Theoptimumsandrateandaggregategradationaredeterminedbyexperiments・Throughtheconcretemixingofdifferentsandratio,accordingtoitsworkability,vibrationandpanslurry,factoryproductionofhigh5mPCCPverticalpipeofacontinuouspouringcompletedbycoreconcreteandotherfactors,thefinalselectionoftheoptimalsandratiois38%・Accordingto thevibrationtestandaggregategradationworkabilityoffreshconcrete,the5mm~25mmgravelbytwogradationprocessing,lessforthe5mm~10mmparticlecontent,appropriatetoincreasethesmallstonecontent,inordertoimprovethepackingdensityofcoarseaggregate,reducetheporosity・Inthesandratioandflyashadmixturetodeterminetheoptimaldosage,anddeterminethedifferentcombinationsofcementandflyashconcretecompressivestrengthandwatercementratiobyfittingtest,optimizedtomeettherequirementsofstrengthdesignofthewatercementratioandconcretemixratio.ThetestresultsofconcretecompressivestrengthanddifferentwatercementratioareshowninTable1.Thefittingequationofcompressivestrengthandcementratioisshownintable2.TheregressionanalysisshowedthatthecompressivestrengthofPCCPsteamcuringconcretewaslinearwiththewatercementratio,andthecorrelationwasgood・Bycalculation,ThestrengthdesigngradeisC60concrete,differentcementandflyashcombination,whenthewaterglueratioreaches0.32,canmeetthestrengthdesignrequirements.Thecalculatedresultsofalkalicontentshowthatthealkalicontentofconcreteinallmixingratioscannotmeettherequirementof1.5kg/m3.Bymixingacertainamountofflyash,theconcretetemperaturerisecanbereduced,andthecrackresistanceandtheyieldoftheproductcanbeimprovedwhilemeetingthelimitvalueoftheprestressedconcreteandtheinhibitingeffectofthealkaliactivityoftheaggregate・ ProblemsinapplicationAlthoughpolycarboxylatesuperplasticizerhasbeensuccessfullyusedinthePCCPprojectofthesouthtoNorthWaterDiversionProject,itisdecidedbytheimportanceoftheproject,anditisalsotheinevitablechoiceforthehighperformanceconcrete・TheSouth-to-NorthWaterDiversionProjectthehigheststrengthdesignofgradePCCPpipecoreconcreteC60,followedbyC50threetotheCaoheAqueductprestressedconcreteandtheYellowRiverprojectC50precastsegment・Severalprojectsusingpolycarboxylicacidadmixture,inadditiontoconsideringthealkaliaggregatereactionandcontrollingthetotalalkalicontentofconcrete,isanimportantreasonforhighstrengthconcretecrackresistanceofhydraulicattention.Throughtheengineeringapplication,insolvingthedesignandconstructionneedsatthesametime,weshouldalsoseetheexistingproblemsintheapplication,inordertobetterchooseandapplypolycarboxylatesuperplasticizer・1.compatibilitywithcementitiousmaterialsItisgenerallyconsideredthatthecompatibilityofpolycarboxylatesuperplasticizerwithcementandcementitiousmaterialisbetterthannaphthalenesuperplasticizer,whichislikelytoleadtomisunderstanding・Infact,anykindofwaterreducingagentmustconsiderthecompatibilityofcementitiousmaterialintheprocessofusing,andthepolycarboxylatesuperplasticizerisnoexception.SuchastheCaoheAqueductpumpingconcrete,thesameproportioninthetwoconstructionunitshaveadifferentsituation,agood,easypumping,andotherconstructionunitsisunabletopumpthesituation,thedifferenceisthedifferentcementmanufacturers・IntheproductionofPCCP mixedwithflyash,amanufacturerofpipeuniforminappearanee,goodquality,andanotherenterpriseproductsappearsegregation,unevencolor,thedifferenceisreducedbythedifferentvarietiesofwater.2.s1umpcontrolproblemS1umpcontrolconsistsoftwoaspects・Ontheonehandistocontroltheslumploss,whichisinthehighflowofpumpconcreteandselfcompactingconcretehasbeensolved,butinhydrauliclowslumpconcrete（5cm〜7cm）,suchastheoverflowsurfaceabrasionresistanceofconcreteisnotagoodsolution,theconcreteoutletworkwell,withtheextensionoftimesoonhardenandstrongthixotropy.Ontheotherhandisapolycarboxylatesuperplasticizeronconcretesignificantimpact,especiallyinthecaseoflowslump,withsmallchangesinwaterontheslump,directlyaffecttheconstructionqualitycontrolofconcretepouringanddifficult・1.theproblemofgascontentTestsandconstructionhavefoundthatsomemanufacturersofpolycarboxylatesuperplasticizergascontentisgreat,andeachbatchhaschanged,althoughtomeetthespecifications,butdoesnotmeettheneedsoftheproject・SuchasPCCPpipe,afterthereleaseoftherequirementsofconcretesurfacesmooth,uniformcolor,ifthereismorethan5mmoftheporesmustberepaired,sotheadmixturecannotbecitedgas・Asforthelargeaqueductandtheoverflowsurfaceabrasionresistanceofconcretewithantifreezedesigngradehavehigherrequirements,waterreducingagent,aircontenttobesmall,cannotcontainofairentraining agentagainstdefoamingcomposition,andhasgoodcompatibilitywithairentrainingagent・Tosumup,althoughpolycarboxylatesuperplasticizerhasmanyadvantages,itcannotbedeniedthattherearestillmanyproblemsintheapplicationprocess,whichneedsfurtherstudy.ChineseHassan一professionalpolycarboxylatesuperplasticizerproviderwww.zghaisen.com
