An-XRD-study-of-the-effect-of-the-SiO2-Na2O-ratio-on-the-alkali-activation-of-fly-ash

AnXRDstudyoftheeffectoftheSiO2/Na2OratioonthealkaliactivationofflyashM.Criadoa,A.Fernández-Jiméneza,⁎,A.G.delaTorreb,M.A.G.Arandab,A.PalomoaaEduardoTorrojaInstitute(CSIC),c/SerranoGalvache,no.4,28033Madrid,SpainbDepartmentofInorganicChemistry,UniversityofMálaga,CampusTeationss/n,29071Málaga,SpainReceived13November2006;accepted26January2007AbstractSolublesilicahasaverysignificanteffectonthemicrostructuralandmechanicaldevelopmentofthecementitiousmaterialsproducedasaresultofthealkaliactivationofflyash.Inthisstudy,fourdifferentalkalinesolutionswithdifferentsolublesilicacontentswereusedtoactivateflyash.Theprimaryreactionproductwasasodiumaluminosilicategel,whiledifferenttypesofzeolitesappearedasminorityphases.Thepercentageandcompositionofthesereactionproductswerefoundtodependonboththesolublesilicacontentpresentintheactivatingsolutionsandthethermalcuringtime.Inaddition,theamountofgelwasobservedtohaveadecisiveeffectonthemechanicalstrengthdevelopinginthematerial.©2007ElsevierLtd.Allrightsreserved.Keywords:Flyash;Rietveldmethod;Silicate–sodiumoxideratio1.IntroductionIn1959,V.D.Glukhovshy[1]suggestedthattheconstruc-tionindustrycouldbenefitfromtheuseofwhathecalled“soilcements”,newcementitiousproductsresultingfromattackingcertain(naturalorindustrialwaste)aluminosiliceousmaterialswithalkalinesaltsolutions.Theflyashproducedinsteampowerplantsisonesuchaluminosilicatesuitableforalkaliactivation[2].Althoughthemechanismsthatregulatethereactionsbetweenalkalineactivatorandflyasharenotfullyunderstood,themodelsthataregraduallybeingdevelopedaffordafairlypreciseviewofwhatactuallytakesplace[3,4].Theactivationrateandchemicalcompositionofthereactionproductsdependonfactorssuchasashparticlesizeandchemicalcomposition,typeandconcentrationoftheactivator,etc.Nonetheless,themechanismsthatcontrolthegeneralactivationprocessareindependentofthevaluesassumedbythesevariablesatanygiventime.Theabovefindingsinformedthedecisiontoconductthepresentstudyontheeffectofthesolublesilicacontentintheactivatingsolutionon