《Influence of ion erosion on RHPB strength in brine environment.docx》由会员分享，可在线阅读，更多相关《Influence of ion erosion on RHPB strength in brine environment.docx（8页珍藏版）》请在课桌文档上搜索。
1、InfluenceofionerosiononRHPBstrengthinbrineenvironmentZhaoXuan12*;LiuLianxin21 China19thMetallurgicalCorporation,ChengdU,610031,China；2 SchoolofCivilEngineering,QinghaiUniversity,Xining,810016,China*Correspondingauthor,se-mail:1103250228.Abstract:Inordertostudythechangeofdynamicelasticmodulus,compres
2、sivestrengthandflexuralstrengthofrecycledcoarseaggregatehighperformanceconcrete(RHPB)specimensduringone-yearcorrosionperiodinSaltLakebrine,andtoexplorethefailuremechanismofitsphysicalandmechanicalbehaviocthedynamicelasticmodulusandstrengthofconcretespecimensandbeammembersunderthecorrosionageofRHPBwe
3、restudied.Researchontheinfluenceofdegreeandsoon.TheexperimentalresultsshowthatthelongerthecorrosiontimeofRHPBspecimensis,thehigherthechlorideioncontentis,thestrongerthecorrosionstrengthwillbecome;thecoexistenceofionscanalsoaffectthecorrosionrate;thelossofdynamicelasticmoduluswillincreasewiththeexten
4、sionofthecorrosiontimeunder0a-1.0aerosion;andunderthesamereplacementrateofrecycledcoarseaggregate(RG),R.WhenthecorrosiontimeofHPBis0-1.0a,theflexuralstrengthincreasescontinuouslywiththeextensionofservicetime.ThecompressivestrengthofspecimenswithdifferentRGreplacementratesdecreasesasawholeundercorros
5、ion.At1.0a,thecompressivestrengthdecreasesmostobviouslywiththeincreaseofRGreplacementrate,andthestrengthdecreasesthemost,RGsubstitutionrateof40%isthebest.Keywords:Recycledcoarseaggregatehighperformanceconcrete;Dynamicmodulusofelasticity;Compressiveandflexuralstrength;Chlorideion;Erosiontime;Substitu
6、tionrate1.IntroductionUsingrecycledaggregatesfromwasteconcretetopreparerecycledconcreteusedinbuildingsisnecessaryforreducingconstructionwaste.Althoughtherearemanyproblemsinitsapplicationinrealengineeringsituations,thismethodhasattractedwideattentionduetoitscharacteristicsofenvironmentalprotectionand
7、resourcerecycling.Therefore,itisnecessarytostudythematerialandstructuralmechanicalperformanceandfailuremechanismofrecycledconcreteinthecorrosivebitternsurroundings.ThereisabundantresearchonsingleerosioninChina,butlittleonthefailurelawofmulti-factorinfluence.Therearealsostudiesontheinfluenceofsulphat
8、eandchlorinesaltsontherecycledconcreteanditsstructuralperformancedegradationinChina.YuHongfaetal.1studiedthestressandnon-stresscorrosionstrengthofOPC,HSCandFRHSCconcretespecimensinthesaltlakebrineenvironmentinXinjiang,QinghaizInnerMongoliaandTibet.YanHongshengetal.2analyzedtheimpactofconcrete,workin
9、gconditionsandtheenvironmentonsulfateerosionbasedonexperiments,andproposedaseriesofanti-corrosionmeasures.ShiFeng3andZhangFeng4revealedthedeteriorationlawofconcretestrengthundersulfateattack.JiangLei5analyzedtheconcretedamageunderdifferenttypesofsulfateattack,pointingoutatlongererosionleadstothinker
10、damagedlayerandsignificantlylowercompressivestrength.ThisexperimentexploresthechangeofcompressiveandflexuralstrengthofRHPBunderSO42andCerosionandanalyzesthemechanicalbehaviorandfailuremechanismofRHPBmaterialsandcomponentsunderbrinecorrosionthoughbrinearrangement.2.Experimentdesign2.1. RawmaterialsCe
11、ment(C):Rll52.5ordinaryPortlandcementproducedbyQilianshanCementCo.Ltd.;PerformanceIndicatorsofCementisshowninTable1.Table 1 PerformanceIndicatorsofCementApparentdensity(kgm3)Specificsurfacearea(m2kg)Lossofignition(%)InitialZfinalsettingtime(min)Flexuralstrength(MPa)Compressivestrength(MPa)3d28d3d28d
12、31203751.06225/3206.58.431.258.7Flyash(F):GradeIflyashwithfinenessof9.0%;Silicafume(Si):withS1O2contentof90.51%andaspecificsurfaceareaof26200m2kg;Slag(K):S95slagwithaspecificsurfaceareaof430m2kg;Sand(三):Riversandwithfinenessmodulusof2.65;Stone(三):Granitegravelwiththemaximumparticlesizeof20mmztheappa
13、rentdensityof2780kgm3,andthebulkdensityof1530kgm3;continuousgradation;Recycledcoarseaggregate(RCA):Aggregateparticlesizeof5mm-45mm;itsbasicpropertiesaretestedusingthemethodprovidedinCobbleandGravelforConstruction(GBT14685-2011);ThecompositionofthebrineisshowninTable2.Table 2 Propertiesofrecycledaggr
14、egatematerialsMoisturecontentWaterabsorptionrateSedimentpercentageCrushingindexApparentdensityOldmortarcontent3%4.4%0.6%11.8%2711kgm333.1%Waterreducingagent(WR):polycarboxylate-typeWR;Water(W):tapwatermeetingnationalStandardsJheconcretemixratioisdesignedaccordingtothewater-binderratioandwaterconsump
15、tion.ThedesignprincipleisdesignedaccordingtothezzGeneraIConcreteMixingRatioDesignRegulationswJGJ55-20116,isshowninTable3.Table 3 ConcreteMixRatioNO.RGSubstitutionrate/%B/MMaterialQuantityofUnitCubicConcrete(kgm3)Compressivestrength(MPa)MCFKSiSGRCAWRWRHPB-O00.305003256010015741115901115051.6RHPB-2020
16、0.3050()3256010015741927.2231.81115050.0RHPB-40400.305003256010015741695.4463.61115048.2RHPB-60600.3050()3256010015741463.6695.41115047.3RHPB-8()800.305003256010015741231.8927.21115045.8RHPB-10010()0.305003256010()15741011591115044.62.2.Experimentplan2.2.1.EvaluationmethodInordertokeeptheconcentrati
17、onofthesolutionconstant,itisnecessarytosealthesolutionwithaplasticfilmtopreventvolatilization,regularlyreplacethesolution,andkeepthetemperatureandhumidityrelativelystable.Achlorideioncontentmeasuringinstrumentisusedintheexperiment.Thesulfatecontentof7samplesismeasuredbythebariumsulfateweightmethod(c
18、hemicaltitrationmethod).Aftercompletingtheflexuraltestofthe100mm100mm400mmspecimensthatareimmersedinthesameconditionforthesameperiodoftime,takethesampleofthetwohalfblockszandtakeenoughconcreteatthesamedepthofthesametestblock.Thesamplingholesarelocatedatthecornersoftheconcretetestblockandare20mmfromt
19、heedges.ThecompositionofthebrineisshowninTable4.AccordingtoBaumemeter;theconcentrationofbrineis1250gL1.Table4BasicchemicalconstituentsperliterofbrineNameNaClNa2SO4MgSO4CaSO4NaHCO3K2SO4Quality/g208.9843.15.481.210.250.092.2.2.StrengthanalysismethodThisexperimenttakes6setsof100mm100mrn400mmanti-foldin
20、gspecimens,witheachsetcontaining3pieces,thusmakingatotalof18anti-foldingspecimens;6setsofcompressivespecimensof100mm100mmX100mm,witheachsetcontaining3pieces,thusmakingatotalof18compressivespecimens.Thisexperimentselects28dstandardmaintenance(referencespecimen),andatotalof3trackingages(0.5a,1.0a),The
21、flexuralstrengthtestshallbecarriedoutaccordingtotheStandardTestMethodforMechanicalPropertiesofOrdinaryConcrete7.Aftermaintainingthe100mm100mmX400mmconcretespecimensfor28days(temperature202;relativehumidityabove95%),thispaperteststheflexuralstrengthoftheconcretespecimenandusestheresultasthebenchmarkf
22、lexuralstrengthofthisexperimentwiththeintensityconversionfactorbeing0.85.Then,testtheflexuralstrengthvaluesofconcretespecimensafterimmersionfor0.5aand1.0aforlateranalysis.Thecompressivestrengthtestadoptsthespecimenof150mm150mm150mmafterimmersingfor0.5aand1.0a.2.2.3.DynamicelasticmoldtestDynamicelast
23、icmoldtestisconductedonthespecimenof100mm100mm400mmwithdifferentcorrosionages.TheinitialdynamicelasticmodeandthataftererosionaremeasuredaccordingtotheStandardTestMethodforLong-TermPerformanceandDurabilityofConcrete(GBT50082-2009)zusingSRDT-60concretedynamic-elasticinstrument.3. Resultsanddiscussion3
24、.1. ErosionanalysisAnalysisofCl-andSO42ErosionConcentrationsofRHPB-40isshowninTable5.After7dcorrosion,thechlorideioncontentoftheconcretebeambecomeslower;andthehighestchlorideionconcentrationintheconcretesurfaceisonly1.11%.Thecontentdecreaseswiththesamplingdepthincreases,indicatingthatthechlorideionc
25、orrosionintensitydecreaseswiththeincreaseofdepthinashorttime.ThechlorideioncontentofRHPBspecimensdecreaseswiththeincreaseofdepthatanycorrosionage,andpeakedat1.0a(1.0a0.5a),Atthistime,thechlorideioncontentofthesurfacelayerreaches10.13.%,whichmeansthatCgraduallymigratestotheinterioroftheconcreteoverti
26、meandtheerosionintensityweakenswiththeincreaseofdepth.ThecontentofSO42-ofRHPBspecimensatanycorrosiontimedecreaseswiththeincreaseofdepth.Itpeakswhenthecorrosiontimeis1.0aandbottomsoutatOaateachsamplingdepth.Atthesamecorrosionage,thecontentofS42isthehighestwhenthesamplingdepthis0-5mm,andthenthatdecrea
27、seswiththeincreaseofdepth.ThisindicatesthattheerosionofS42isstrongerovertimewithlesserosioncontent.Whenthecorrosiontimeis0.5a-1.0a,thereislittlechangeinthecontentofSO42-ofRHPBspecimensovertime.S42erosionisnotevidentduringthistimeperiod,butitgetsstrongerovertimezindicatingthatacertainsubstanceinhibit
28、sS42.JinYannanetal.8alsosuggestedthatwhenS42andCcoexist,Ccanslowdownthesulfateattack.Thehighertheconcentrationofthechloridesaltsolution,thestrongertheeffectofdelayingconcretedamage.ThatisduetothegenerationofFriedelsaltthatcausespartialporeblockageinconcretereducesthediffusionrateofSO42.Italsoindicat
29、esthatthecoexistenceofionscanaffectthecorrosionrate.Table5AnalysisofCandSO42ErosionConcentrationsofRHPB-40corrosiDeptCSO42-corrosiDepClSO42corroDepth(mmcrso42-onhconcentconcentonthoncentroncentsiononcentoncenttime(mrationrationtime(mationrationtimerationration(a)m)(%)(%)(a)m)(%)(%)(a)(%)(%)0-50.0110
30、.0720-50.7980.0760-51.0130.0835-100.0090.0225-100.5620.0645-100.7430.06610-150.0080.02510-150330.0510-150.4550.0590(7d)15-200.0070.0180.515-200.1450.045115-200.2870.05120-250.0070.02220-250.1380.04320-250.1640.04925-300.0050.03525-300.0840.03925-300.1590.03830-350.0040.03530-350.080.03430-350.1350.0
31、323.2.DynamicelasticmodelanalysisDynamicmodulusofRHPBspecimensisshowninTable6andFig.l.Whenwater-to-binderratioremainsunchanged,thedynamicelasticmodulusofthespecimendecreaseswiththeincreaseofRGsubstitutionratefrom0-100%underthesamecorrosionconditions.WiththeincreaseofRGsubstitutionratezthedynamicelas
32、ticmodulusofOadecreasesfrom42.2MPato36.8MPa,adecreaseof12.8%;thatof0.5adecreasesfrom44.5MPato38.6MPazadecreaseof13.3%;thatof1.0adecreasesfrom36.5MPato30.1MPazadecreaseof17.5%.Itshowsthatat0a-1.0azthedynamicmoduluslossincreaseswiththeextensionoferosiontime.UnderthesameRGsubstitutionrate,astimeprolong
33、s,thedynamicelasticmodulusfirstrisesandthenfalls.Itpeaksat0.5a,risesslightlyduring0-0.5a,anddropssharplyduring0.5a-1.0a.Itindicatesthatundershort-timeerosionisfavorableforthedynamicmodulusofthespecimen.Table 6 DynamicmodulusofRHPBspecimensDynamicmodulus(GPa)NO.WaterbinderratioStandardcuring28d(Oa)0.
34、5aLOaBrineenvironmentBrineenvironmentRHPB-O0.3042.244.536.5RHPB-200.3041.343.335.4RHPB-400.3040.541.534.3RHPB-600.3039.140.933.2RHPB-800.3038.739.831.2RHPB-1000.3036.838.630.1O204080100RGsubstitutionrate(%)Fig.1Dynamicmoduluscurve6.3. AnalysisOfstrengthchangeStrengthofRHPBBrineunderCorrosionisshowni
35、nTable7,Fig.2andFig.3.Table 7 StrengthofRHPBBrineunderCorrosionFlexuralstrength(MPa)Compressivestrength(MPa)TypebinderratioStandardcuring28d0.5a1.0aStandardcuring28d0.5a1.0aBrineenvironmentBrineenvironmentBrineenvironmentBrineenvironmentRHPB-O0.306.37.98.551.659.946.6RHPB-200.306.06.87.950.055.645.2
36、RHPB-400.305.77.78.648.259.446.3RHPB-600.305.56.77.347.357.640.6RHPB-800.305.26.26.945.852.338.7RHPB-1000.305.15.97.144.654.135.7ds6uej-53XEOa05aIaFig. 2 FlexuralStrengthCurveAtOa(intensityof28d)ztheflexuralstrengthdecreasesfrom6.3MPato5.1MPawiththeincreaseofsubstitutionratefrom0%to100%,adecreaseof1
37、9%.At0.5aztheflexuralstrengthdecreaseswiththeincreaseofsubstitutionratefrom0%to100%.Attheturningpointwhenthesubstitutionrateis40%,theflexuralstrengthis7.7Pa.Theflexuralstrengthpeaksat7.9MPawhenthesubstitutionrateis0%andbottomsoutat5.9MPawhenthesubstitutionrateis100%zadecreaseof25.3%.At1.0a,theflexur
38、alstrengthdecreaseswiththeincreaseofsubstitutionratefrom0%to100%.Attheturningpointwhenthesubstitutionrateis40%ztheflexuralstrengthis8.6Pa.Theflexuralstrengthpeaksat8.5MPawhenthesubstitutionrateis0%andbottomsoutat6.9MPawhenthesubstitutionrateis80%,adecreaseof18.8%.Theaboveshowsthatthechangeofflexural
39、strengthisrelatedtotheRGsubstitutionrateanderosiontime,buttherelationshipremainstobefurtherexplored.AtthesameRGsubstitutionrate,theflexuralstrengthofRHPBdoesnotdeclinewhenthecorrosiontimeis0-1.0a;instead,itincreaseswiththeextensionoftime.Thisphenomenonindicatesthatacertainsubstanceisproducedduringco
40、rrosion,whichcanhelptopromotetheflexuralstrength.WhentheRGsubstitutionrateis0%,theflexuralstrengthincreasesby34.9%at0a-1.0aandreachesamaximumvalueof8.5MPaat1.0a.WhentheRGsubstitutionrateis20%,theflexuralstrengthincreasesby31.7%at0a-1.0aandreachesthemaximumof7.9MPaat1.0a.WhentheRGsubstitutionrateis40
41、%,theflexuralstrengthincreasessignificantlyat0a-1.0az0-1.Oaincreasesby50.9%,andpeaksat8.6MPaat1.0a.WhentheRGsubstitutionrateis60%,theflexuralstrengthincreasesby31.0%at0a-1.0aandreachesthemaximumof7.3MPaat1.0a.WhentheRGsubstitutionrateis80%,theflexuralstrengthincreasesby32.7%at0a-1.0aandreachesthemax
42、imumof6.9MPaat1.0a.WhentheRGsubstitutionrateis100%,theflexuralstrengthincreasesby39.2%at0a-1.0aandreachesthemaximumof7.1MPaat1.0a.Asindicatedabove,whentheRGsubstitutionrateisthesameztheflexuralstrengthincreaseswiththeincreaseoferosiontimeduring0-1.0azwiththeincreaserategreaterthan30%.whenthesubstitu
43、tionrateis40%,theincreaseratepeaksat50.9%zwhichindicatesthatbrineerosioncanpromotetheflexuralstrengthofthespecimen.O20406080100Substitutionrate(%)Fig. 3 ompressivestrengthcurveThecompressivestrengthofRHPBspecimensshowsadownwardtrendwiththeprolongedservicelifeinthebrinecorrosiveenvironment.AtOaztheco
44、mpressivestrengthofthespecimenateachsubstitutionrateshowsadecreasingtrend.Itreachesthemaximumof51.6MPaat0%andtheminimumof44.6MPaat100%,adecreaseof13.6%.At0.5a,thecompressivestrengthofthespecimenateachsubstitutionratedecreasesfirstandthenincreases,thendecreasesandfinallyincreases,andtheoveralltrendof
45、declining.WhentheRGsubstitutionrateis0%,thecompressivestrengthreachesthemaximumof59.9MPa;whentheRGsubstitutionrateis80%,itreachestheminimumof52.3MPazadeclineof12.7%,At1.0a,thecompressivestrengthofthespecimenundereachsubstitutionratedecreasesfirst,thenincreasesandfinallydecreases,withtheoveralltrendo
46、fdeclining.WhentheRGsubstitutionrateis0%,thecompressivestrengthreachesthemaximumof46.6MPa;whentheRGsubstitutionrateisIOC),itreachestheminimumof35.7MPa,adeclineof23.4%.TheaboveanalysisshowsthatthecompressivestrengthofthespecimensunderanyRGsubstitutionrateshowsadownwardtrendanditdecreasesthesharpestat1.0a.UnderanyRGsubstitutionrate,thecompressivestrengthshowstrendof0.5a0a1.0a.ThecompressivestrengthofRHPBspecimensstillincreasesduring0-0.5a,indicatingthatthehydrationlastsforalongtime.Thatismainlybecause(1)themicro-aggregateeffectofthem
