influence of sulfate on the steric hindrance of polycarboxylate superplasticizer

1、1InfluenceofSulfateontheStericHindranceofPolycarboxylateSuperplasticizerZhiWangabZiyiWangaNanJiangaYingWangaJiaoshiQianbaSchoolofChemistryChemicalEngineeringChongqingUniversityChongqing400044PRChinabCollegeofMaterialsSci

2、enceEngineeringChongqingUniversityChongqing400030PRChinaAbstractPolycarboxylatesuperplasticizerdispersecementparticlesmainlybysterichindranceeffect.Toinvestigatewhethersulfateeffectthedispersioncapabilityofcementpastebyw

3、eakenitssterichindranceeffectthepaperdeterminatetheeffectofsulfateontheadsptionlayerthicknessofsuperplasticizersofdifferentmoleculeweightoncementparticlesbyXrayphotoelectronspectroscopy.Byusingfluescencespectrumtheconfma

4、tionchangeofsuperplasticizerinsulfateaqueouswasstudied.TheresultindicatedthatsulfateseffectthedispersionofcementpasteNa2SO4hasmenegativeeffectsoncementpastedispersionthanCaSO42H2O.Superplasticizerswithlargermoleculeweigh

5、taremesensitivetosulfates.Sulfategreatlyreducetheadsptionlayerthicknessofpolycarboxylatesuperplasticizer.Howevereffectofsulfatesontheconfmationofsuperplasticizerinaqueousisnotsignificant.Keywds:Polycarboxylatesuperplasti

6、cizerSulfateAdsptionlayerthicknessConfmationchange1.IntroductionBesidesthemechanismofelectrostaticrepulsionPolycarboxylateSuperplasticizerwithcombshapedmoleculestructuredispersecementparticlesbymeansofthesterichindrancef

7、romlongsidechainwhichisdifferentfromNaphthaleneserieswaterreducingagent’selectrostaticrepulsionmechanism[1].PolycarboxylatesuperplasticizerallowstheproductionofhighlyflowableconcreteCrespondingauth.Addressat:SchoolofChem

8、istryChemicalEngineeringChongqingUniversityChongqing400044PRChina.Tel.:862365126109.Emailaddress:cquwangzhi@(Z.Wang).3Polycarboxylatesuperplasticizerexistsin“cementwatersuperplasticizer”systeminthefmofadsbedstatedisperse

9、dstate.Itisgenerallybelievedthattheabsbedsuperplasticizerdispersecementparticlesbyitsstericeffect.Thedispersedsuperplasticizersnotonlymaintaindynamicbalancebetweensolutionadsptionlayerbutalsosupplysuperplasticizerconsume

10、dbycementhydrationinterlayeredadsptionwhichgivesystemagooddispersionstability.Differentmethodsareusedftheacterizationofadsptionlayerthickness:XrayPhotoelectronSpectroscopy[4]AugerElectronicSpectrum[5]AtomicFceMicroscope[

11、6]ect.Differentinstrumentsareusedtochacterizestericeffectincludingdynamicstaticlightscatteringinstrument[7]fluescencespectrum[8]singlemoleculefcespectroscopy[9]ect.AsacommonsurfaceanalyticalinstrumentXrayPhotoelectronSpe

12、ctroscopy(XPS)iswidelyusedinmaterialsscienceresearch.Intensityofspectrallineintheenergyspectrapictures(thatistheareaofphotoelectronpeak)tellsatomcontentrelativeconcentrationthechemicalshiftofinnerelectronbindingenergysug

13、gestschemicalbondgedistribution.Fluescencespectraprovideexcitationemissionspectratheintensitypositionofpeaksreflectschangesinthemicroenvironmentofthepolycarboxylatesuperplasticizers.Pyrenemarkedonthepolycarboxylatesuperp

14、lasticizerasafluescentprobesincesuperplasticizerspossessactersofsoftmatteritiseasilyaffectedbyionicstrengthpHconcentrationetc.Determinatingexcitationemissionspectragiveaccesstotheaggregationbehavimicroconfmationalchanges

15、ofsuperplasticizers[10].ThepaperstudiedtheeffectofsulfateonthelayerthicknessofabsbedsuperplasticizeroncementparticlesbyXrayPhotoelectronSpectroscopywiththehelpofFluescenceSpectrahowsulfateseffecttheconfmationofsuperplast