impacts of calcium sulfate on the hydration of calcium aluminate cement - portland cement blends

1、ImpactsofCalciumSulfateontheHydrationofCalciumAluminateCementPtlCementBlendsatDifferentTemperaturesLinglinXuPeimingWangGuofangZhangXiaojieYangSchoolofMaterialsScienceEngineeringTongjiUniversityCao’an4800JiadingDistrictSh

2、anghai201804ChinaAbstractThepresentstudyfocusontheeffectofcuringtemperatureonthehydrationofcalciumaluminatecement(CAC)dominatedternarybindersat0102040℃.Twovarietiesofcalciumsulfateareemployedincludingαhemihydratenaturala

3、nhydrite.Theeffectsoftemperatureonthephasedevelopmenttogetherwithmicrostructurechangeofpasteswithin3daysweresystematicallydeterminedbyXraydiffraction(XRD)backscatteredelectronimaging(BEI)mercuryintrusionposimeter(MIP).Re

4、sultsshowthathighertemperatureacceleratesthe1daystrengthprominentlywhileithasnoobviouscontributiontothelateragestrength.Furthermethoughthemainhydrationproductsarerelatingtocalcium(sulpho)aluminaterelatedphasesraisingtemp

5、eratureleadstoarapiderconversionfromettringitetoplatelikemonosulfatehigheramountofcoarserpesfpasteswithanhydriteafter3daysbutfinerpesfthosepasteswithαhemihydrate.Additionallystratlingite(C2ASH8)aluminiumhydroxidealsofmat

6、40℃inthosepasteswcomparedwithbinderscontainingαhemihydrate.iginalityRapidsettinghardeningblendswhichbasedoncalciumaluminatecement(CAC)Ptlcementcalciumsulfateismemewidelyappliedinthefunctionalmtarsatdifferentconditionscer

7、tainlycuredatdifferentcuringtemperatures.Howeverallthepreviousinvestigationsonlyfocusonthehydrationat20℃.Inthispresentpacuredatdifferenttemperature(0102040℃)weresystematicallyraydiffraction(XRD)backscatteredelectronimagi

8、ng(BEI)mercuryintrusionposimeter(MIP).Sothisisthefirstiginality.ItwasrevealedthatbothcalciumsulfatesourcesCACcalciumsulfateratiohadprominentimpactsonthewholehydrationfternarybindersat20℃additionallythedissolutionactersof

9、calciumsulfatehadfirmconnectionswithcuringtemperatureconsequentlytheeffectofcalciumsulfatevarietywasalsotakenintoconsiderationinthispaper.Bothanhydriteαhemihydratewereappliedcomparedfamegeneralconclusion.Sotheapplication

10、ofbothanhydriteαhemihydrateinsuchternarybinderscuredatdifferenttemperaturesisthesecondiginality.Keywds:CalciumaluminatecementcalciumsulfatetemperaturehydrationettringitemicrostructureCrespondingauth:tjwpm@Tel:86216958214

11、0Fax:862169582012(differentdissolutionacteristics).ItwksaspartofacomprehensivestudyontheinfluenceofcuringtemperatureonthemicrostructuredevelopmentofCACbasedternarysystemswhichishelpfultoenhanceunderstingofthehydrationoff

12、unctionalmtarappliedinspecialconditionsatdifferenttemperatures.2Experimental2.1RawmaterialsTheCalciumalumintecement(CAC)Ptlcement(CEMI42.5)usedinthisstudywereobtainedfromKerneosAluminateTechnologyCoXinfacementCo.respecti

13、vely.Hemihydrate(H)naturalanhydrite(A)wereprovidedasthemainsourcesofcalciumsulfate.ThechemicalcompositionsoftherawmaterialsusedweredeterminedbyXrayfluescence(XRF)aslistedinTable1.Sincebothcalciumsulfatesources(Xu.etal.20

14、12Xu.etal.2014)CACcalciumsulfateratio(Lamberet.2004)haveprominentimpactsonthewholehydrationprocessfternarybindersthePC:CAC:anhydritemassratiowasfixedat22.5:51.7:25.8whilewatertobinderratiowas0.5bymass.Accdingtothevariety

15、ofcalciumsulfateusedaswellasthecuringtemperature(0102040℃)thesamplesweA20A40H0H10H20H40.Tab.1Chemicalcompositionofrawmaterials(wt.%)SiO2CaOAl2O3Fe2O3MgOSO3K2ONa2OTiO2CAC0.3431.2067.100.100.060.34PC21.5064.204.142.402.572

16、.890.840.670.32A1.7239.440.350.161.8051.960.02H1.0338.500.170.040.1053.400.140.012.2CuringTestingWatercementssswerestedattherespectivetemperaturesf2daysbefemixing.Allthespecimenswerecuredat0102040℃withavariationof1℃respe

17、ctivelytherelativehuitywas6010%.Mtarsamples(40mm40mm160mm)fcompressivestrengthstestswerepreparedmeasuredaccdingtoISO679:1989.Thesesamplesweredemouldedafter24hoursofcuringromlyedfmechanicaltestingafterperiodsof1328days.Xr

18、aydiffraction(XRD)wasemployedfthephasedeterminationincementpastes.Thescanningwasperfmedbetween575witha2θincrement2perminaCuKαradiation(λ=1.541).XRDdatawererecdedwithRigakuDmax2550VB3.Inadditionanacceleratingvoltageof40kV

19、acurrentof100mAwereed.Befethetestingallthesamplesweregroundtoafinenessofabout400m2kgBlainesurfaceareasattheendofeachagingperiodtreatedwithacetonediethylethertostophydrationstedindesiccatstoensureprotectionagainstwatercar

20、bondioxide.Additionallythepolishedsamplesfbackscatteredelectronimagingtestwerepreparedbyimpregnatingepoxyresinpolishingcoatingcarbon.Allgrindingpolishingstepswereoperatedonavariablespeedgrinderpolisher.Themicrostructureo

21、fpolishedsurfacewasanalysisonthebaseofdifferentgreylevelsunderhighvacuummode(at1E5TrH2O)withSEM(HITACHIS2700)withavoltageof15kV.Furthermeanautomaticmercuryinstructionposimeter(ThermalScientificPAL140440series)wasusedthem