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1、anti-corrosion measures.Sh Feng3J and Zhang Feng4J established a model of concrete mechanical property degradation for sulfate corrosion to reveal the deterioration law of concrete strength under sulfate altack.Jiang Lei5 and other studies on concrete damage under different types of sulfate solution
2、 erosion showed that the thickness of the damaged layer increased with the increase of erosion time, and the compressive strength of the damaged layer concrete decreased Significantly.Zhu Hongbing el al. obtained the three-stage law of fatigue damage in the fatigue lest of T-beam and fitted the S-N
3、cu,e6 of T-beam.Sun Xiaodong et al. analyzed the relationship between the main rust corrosion and the fatigue performance of concrete beams through fatigue test7.The experiment was conducted to investigate the changes of compressive and exural strength of HPC materials under the attack of S42 and Cl
4、 . The mechanical behavior and failure mechanism of HPC materials and components under brine corrosion were analyzed.StudyontheInfluenceofSaltLakeBrineonHPCMaterialsandStructuralMechanicalPropertiesZHAOXuan(China19thMetallurgicalCorporation)Abstract:Thispaperstudiesthechangesofcompressiveandflexural
5、strengthofhighperformanceconcrete(HPC)andordinaryconcrete(OPC)specimensduringthe2-yearcorrosionperiodofsaltlakebrineandthestructuralfatigueofHPCandOPCbeamsaftersaltlakebrinecorrosion.Thefailuremechanismoflifeandmechanicalbehavior,andtheS-Ncurvesofdifferentmodelsweredrawn,andtheS-Ncurveequationwasfit
6、ted.Theeffectsofionconcentrationonconcretespecimensandbeammemberswereanalyzedbysampling.Thetestresultsshowthattheflexuralstrengthisenhancedduringtheageingperiod,andthecompressivestrengthisreduced.Themineraladmixtureismixed.Addingenergycaneffectivelyimprovethecorrosionresistanceofconcrete;thedamageca
7、usedbysulfateioncorrosionisoneofthereasonsforthedecreaseofcompressivestrength,andchlorideioncanslowthespeedofsulfateattack.Fatiguefailureincludesthreestagesofinitialcracking,crackdevelopment,anddamageaccumulation,andthestirruphascertaincrackresistance;thefatiguelifeofconcretebeamswithlowcorrosionrat
8、eislargelyduetoitsownstrengthandTheenvironmentisdetermined.Keywords：Highperformanceconcrete;Thebitterncorrosion;Thestructuralfatigue;Damageaccumulation1 .IntroductionThecharacteristicsofhighaltitude,highcoldandaridatmosphericenvironmentandthecharacteristicsofundergroundbrineenvironmentinXiningareaha
9、veseriouseffectsonthecrackingofconcretematerialsandthecorrosionofcomponents,whichcausesthestrengthofconcretematerialstochange.Therefore,thematerialsofconcretematerialsintheenvironmentofbrinecorrosionaredeveloped.Researchonstructuralmechanicalbehaviorandfailuremechanismisnecessary.Inordertostudythela
10、wofdegradationofmaterialsandstructuralpropertiesofconcretemembersunderthecorrosionofsulfateandchloridesalts,Chinesescholarshavecarriedoutaseriesofstudies.YuHongfa1,etc.Thestressandnon-stresscorrosionstrengthofOPC,HSCandFRHSCconcretespecimensinsaltlakebrineenvironmentinXinjiang,Qinghai,InnerMongoliaa
11、ndTibetwerestudied.YanHongsheng2andotherexperimentsanalyzedtheeffectsofconcreteitself,workingconditionsandsurroundingenvironmentonsulfateattack,andproposedaseriesof2 lestdesign2.1 TestpiecerawmaterialsCement(C):producedbyQilianshanCementCo.,Ltd.,OPC(C30concrete)adoptsP.O42.5cement,HPC(C5()concrete)a
12、doptsRII52.5cement;flyash(F):producedbyQinghaiQiaotouAluminumElectricCo.,Ltd.GradeIflyash,fineness9.0%;Silicafume(Si):QinghaiBlueSkyEnvironmentalProtectionTechnologyCo.,Ltd.,SiO2content90.51%,specificsurfacearea26200m2/kg;slag(K):XiningspecialsteelS95slagproducedbythecompany,withaspecificsurfacearea
13、of430m2kg;sand(三):riversand,finenessmodulus2.65;stone(三):granitegravel,maximumparticlesize20mm,apparentdensity2780kgm3,bulkdensity1530kgmcontinuousgrading;rustinhibitor(Z):calciumnitritetype,indicatedbyZ,solidcontent30%,usedforreinforcingsteelmembers;waterreducingagent(WR):polycarboxylicacidsystem.W
14、ater(W):Usetapwater.ThedesignprincipleisdesignedaccordingtothettGeneralConcreteMixingRatioDesignRegulations,JGJ55-20118,seeTable1.7ab.lMixtureratioofconcreteMaterialconsumptionpercubiccubeofconcrete/TypesB/Mkg-nr，MCFKSiSGZWRWOPC0.523403407341207177HPC0.30(F.K、Si)5003256010015741115933111502.2 Testpl
15、an(1) Strengthandsamplinganalysismethods10setsof100mm100mm400mmanti-foldingtestpieces,eachsetof3testpieces,atotalof3()testpieces.14setsofcompressivetestpiecesofI(X)mm100mm100mm,3ineachgroup,totaling42pieces.Set28dstandardmaintenance(referencetestpiece),0.5a,1.0a,1.5a,2.0aforatotalof5trackingages.The
16、compositionofthebrineisshowninTable2.Theconcentrationofbrineinthecuringtankisregularlymeasuredto1250gLlbytheBaumesseveritymetertoensurethebrineconcentration.Tab.2ThebasicchemicalcompositionofeachliterofbrinenameNaClNa2SO1MgSO1CaSO1NaHCO3K2SO,Quality/g208.9843.15.481.210.250.09Theflexuralstrengthtest
17、shallbe100mminaccordancewiththeStandardTestMethodforMechanicalPropertiesofOrdinaryConcrete9).Concretespecimensof1()()mm4(X)mmweretestedforflexuralstrengthofconcretespecimensafterstandardcuring(temperature20+2,relativehumidityabove95%)for28days,andusedasthebenchmarkflexuralstrengthofthisstudy.Value,t
18、heintensityconversionfactoristakenas().85.Theflexuralstrengthvaluesofconcretespecimensafterimmersionin0.5a,1.0a,1.5a,and2.()ainbrinewereanalyzed.Forthecompressivestrengthtest,atestpieceof100mmI(X)mmI(X)mmwasusedforthecompressiontestunderthecorrespondingconditions,andtheintensityconversionfactorwas0.
19、95.Thevaluesofthebaselinecompressivestrengthandthecompressivestrengthvaluesoftheconcretespecimensaftertheimmersionof().5a,1.0a,1.5a,and2.0ainthebrinewereobtainedinturn,andanalyzed.Afterusingthebenchcoredrillsamplertocompletetheflexuraltestofthe100mm100mm400mmspecimensthatwereimmersedinthesameconditi
20、on,thetwohalftestspecimensweresampled,andenoughconcretewastakenatthesamedepthofthesametestblock.powder.Thesamplingholesarelocatedatthecomersoftheconcretetestblock,andthedistancefromtheedgeis20mm.Thesamplingdepthrangesfrom0to35mmandisdividedinto7samplingdepthsamples.Thechlorideioncontentwasmeasuredus
21、ingachlorideioncontentrapidanalyzer,andthecontentofSO42inthesamplewasdeterminedusingabariumsulfateweightmethod.(2) FatiguetestbeamdesignThedimensionsoftherectangularsectionreinforcedconcretebeamare:500mm100mm85mm.Thelongitudinallystressedsteelbars,stirrupsandstudsofthebeamareHPB235(primarj,)lightrou
22、ndbars,allofwhichare6.5steelbars.Theconcretecoveris12mmthick.Thetestistoloadtheconcentratedforceinthemiddleofthespan.Thenetspanofthebeamis350mm.ThedimensionsofthetestpieceandthereinforcementareshowninFigure1.Thistestusesacouplingmethodinwhichthecorrosiontestisperformedfirstandthenthefatiguetestisper
23、formed.Twotypesofcouplingactionaremadeforeachbeamofthecompositeratio,whicharerepresentedbyAand,Crespectively.Thereferencebeamsaredifferentfbreachmixratio,andatotalof22beams.Thethreeformsofcouplingare:OPC,HPCfbrbendingfatigue(reference),bendingfatigue+waterenvironment（八）,bendingfatigue+brinecorrosion
24、(C).Thefatigueconditionofthefatiguetestspecimenswas7daysinboththebrineenvironmentandthewaterenvironment.Inthecorrosiontest,thebeamsofthesamemixingratiowererespectivelyimmersedinthebrineandwaterenvironment,thebrineconcentrationwasperiodicallytestedandthetestbeamwascompletelyimmersedinthesolutionatthe
25、sametime,andtherustformationonthebeamsurfacewasobsen,ed.Fig.1specimensizeandsectionreinforcementdiagram(unit:mm)(3) FatigueloadtestmethodThistestusedTMF-5TconcretefatiguetestIoaderThefatigueloadfrequencyis0.43Hz.Beforethefatiguetest,themaximumfailureloadisFuafterthestandardmaintenanceofthetestpiece,
26、thefatiguesetloadisFy,andthefatiguestressratioRaremeasured.Thefatigueloadvalueswere:0.35Fu,0.50Fu,0.65Fu,and0.80Fu,andthenumberofinitialfracturefatiguesN1andthenumberoffatiguesNwererecordedafterthefatiguetest.Thecrackwidthof2.0mmisusedasadamagemark.3 Resultsanddiscussion3.1 OPCandHPCionerosiondeptha
27、nalysisTheetchingconcentrationsofCandSO/一areshowninTable3.(1) ClerosionanalysisUnderthe7dcorrosionperiod,thechlorideioncontentoftheconcretebeamislow,andgraduallydecreaseswiththedeepeningofthesamplingdepth,indicatingthatthechlorideionerosionintensityintheconcreteisweakinashorttime.Thechlorideionconte
28、ntofOPCandHPCspecimensdecreasedwiththeincreaseofdepthatanyserviceage.Thechlorideioncontentofthesamesamplingdepthreachedthemaximumat2a,andthesizewas2.0a1.5a1.0a0.5a.ItisindicatedthatCgraduallymigratestotheinterioroftheconcreteovertime,andfromtheoutsidetotheinside,theerosionisweakened.TheCcontentofOPC
29、inthesamplingdepthof30-35mmundervariouscorrosionagesiskepthighandmorethan0.5%.TheCcontentinHPCdecreaseswiththedepthat30-35mmdepth.Thecontentremainedlowandlessthan0.5%,whichindicatesthattheconcretespecimenswithmineraladmixtureshavebettercompaction,reducedthepermeabilityofC,anddidnotparticipateinhydra
30、tioninconcretespecimens.ThemineraladmixturehasacertainadsorptioneffectonClwhichcaneffectivelyhinderthediffusionofCinconcrete.Alargenumberofstudieshaveshownthattheanti-erosionabilityofconcreteisenhancedbytheincorporationofmineraladmixturessuchasflyash,slagandsilicafume,mainlyduetothevolcanicasheffect
31、offlyash,resultinginmorehydratedcalciumsilicateandaluminumhydrate.ThehydrationproductsuchascalciumacidincreasesthephysicaladsorptionamountofC,therebyincreasingtheabilitytobindC.TheslagpowderismoreactivethanflyashandcanreactwithCa(OH)?toformmorehydratedcalciumsilicate.Thehydratedcalciumsilicatenotonl
32、ymakestheconcretemorecompact,butalsoreducesthetotalamountofCenteringtheconcreteandadsorbstheincomingC.(2) SO42erosionanalysisThecontentofSOj-inconcretespecimensdecreasedwiththeincreaseofdepthatanyserviceage.ThecontentofSOa2attheageof2awasthehighestatthesamplingdepthis0-5mm,thecontentofSOa2isthehighe
33、st,andthendecreaseswiththeincreaseofdepthuntilitisstable.ThisindicatesthattheerosiondepthofSOJ-isdeepenedwithtime,buttheerosioncontentisreduced.WhenthecorrosiontimeofOPCandHPCspecimensis0.5-1.5a,thecontentofSOFatthesamesamplingdepthchangeslittlewiththeextensionofcorrosiontime.TheS042-erosionwasnotob
34、viousduringthisperiod,buttheerosiondepthofSoj-deepenedwithtime,indicatingthatacertainsubstanceinhibitedtheerosionofSOu2duringthisperiod.JinYannan10andotherstudieshavealsoshownthatwhenS042andCcoexistintheetchingsolution,Ccanslowdowntherateofsulfateattack.Thehighertheconcentrationofthechloridesaltsolu
35、tion,themoreobvioustheeffectofdelayingconcretedamage.MainlyduetothereactionofCwithhydrationproductsinconcretetoformFriedelsalt,whichcausedpartialporeblockageinconcreteandreducedthediffusionrateofSO/-jnconcrete.Therefore,inadditiontothemineraladmixtureinhibitingSO42erosion,thecoexistenceofionscanalso
36、affectthecorrosionrate.Between0.5-2.0ainserviceage,theconcentrationofSOj2-inHPCissmallerthanOPCatsamplingdepthofO-1Omm,whichindicatesthattheconcretespecimenwithmineraladmixturehasbettercompactness.SOisnoteasytodiffuseandhasgoodcorrosionresistance,whichdoesnotcauseseriousconcretespallingandcracking.S
37、tudiesbyTaoWei11alsoshowedthattheblendingofadmixturesandhigh-efficiencywaterreducerformulatedintoconcretewithlowwater-to-binderratiocanimprovetheresistanceofconcretetosulfateattack.eachsamplingdepth,andthelowestatOa,andOa.WhenTab.3AnalysisofErosionConcentrationofCandSOJ-BrineOPCHPCOPCHPCcorrosiontim
38、e/aCoresampling1c.k/ECl-concentrationCl-concentrationSulfateSulfatedepth/mm/%/%concentration/%concentration/%O(7d)0-50.0240.0110.0670.0725-100.0210.0090.0350.02210-150.0150.0080.0110.02515-200.0130.0070.0110.01820-250.0130.0070.0120.02225-300.0090.0050.0130.03530-350.0090.0040.0150.0350-51.2670.7980
39、.1320.0765-100.9850.5620.0880.06410-150.8910.330.0750.050.515-200.8850.1450.0680.04520-250.6390.1380.0530.04325-300.6480.0840.0680.03930-350.5860.080.0660.0340-51.6161.0130.1810.0835-101.2130.7430.1680.06610-151.1730.4550.1210.059115-201.1410.2870.0720.05120-251.0170.1640.0650.04925-301.0060.1590.05
40、90.03830-350.9510.1350.0520.0320-51.8421.0930.2170.1215-101.3240.8250.1720.06210-151.1530.6650.1260.0521.515-201.1010.5060.0910.05820-251.0350.3190.0810.05225-301.0070.2250.0710.05130-350.9880.2090.0630.0480-51.8011.3330.2360.1365-101.4050.9450.1950.083210-151.2030.8690.1780.07515-201.1170.7170.1310
41、.06620-251.0560.3540.1190.06125-300.9980.2170.1070.05630-350.9920.2080.0920.0523.2 AnalysisofchangesinOPCandHPCintensifyTab.4FlexuralstrengthofOPCandHPCBrineincorrosion(MPa)TypesW/BFlexuralstrength(MPa)Compressivestrength(MPa)28d0.5aLOa1.5a2.Oa3d7d28d0.5a1.Oa1.5a2.OaOPC0.523.03.16.04.66.65.513.032.4
42、23.124.327.821.2IIPC0.306.37.98.59.313.521.841.150.659.946.646.643.9ThestrengthofOPCandHPC28dcanberegardedasthestrengthunderthecorrosionofbrineatOa.TheamountofflyashinHPCis12%,theamountofslagis20%,andtheamountofsilicapowderis3%.TheflexuralstrengthofOPCandHPCspecimensincreasedwiththeprolongedservicet
43、imeinthebrinecorrosionenvironment.TheflexuralstrengthofOPCincreasedfirstly,thendecreasedandthenincreasedwhenthecorrosiontimewas0-2.0a,andreachedamaximumof6.6MPaat2a.However,whenthecorrosiontimewas0-2.0a,thespecimendidnotshowanybendingresistance.Thelossofstrength,andtheflexuralstrengthcontinuedtoincr
44、easewiththeextensionofservicetime,itsvaluereached13.5MPa,whichproveditscorrosionresistanceisthestrongest.Thisphenomenonindicatesthatasubstancemustbeproducedduringthecorrosionofthebrinetoincreaseitsflexuralstrength.ThecompressivestrengthofOPCandHPCspecimensincreasedgraduallyduringthecuringperiod,andt
45、heratioof7dcompressivestrengthtototalstrengthwas40.1%and81.2%,respectively,indicatingthattheconcretespecimenswithmineraladmixtureswerehydratedearlier.Theintensitygrowsfaster,whilethelaterstrengthincreasesslowly.ThecompressivestrengthofOPCandHPCspecimensdecreasedwiththeprolongedservicetimeinthebrinec
46、orrosionenvironment.ThecompressivestrengthofOPCspecimensat0-2aisfirstlyreduced,thenincreasedandthendecreased,mainlyduetothereactionofconcretechemicalsinCandSO42-solutions,andadsorptionofionstofillpores.Theporesofthesurfaceconcreteareexpandedanddestroyed,andthecompressivestrengthisreduced.Whenthebrin
47、eionsentertheinteriorinlargequantities,theexpansivematerialettringiteisproducedtoincreasethecompressivestrength.Finally,thecompressivestrengthoftheconcretedecreasesduetotheaccumulationofinternalexpansiondamageofthecomponents.ThecompressivestrengthofHPCspecimensisstillincreasingat0-0.5a,indicatingthatthehydrationlastsforalongtime,whichismainlydueto(1)micro-aggregateeffectofmineralmic
