Effect of alkali-activated solution concentration on the performance of alkali-activated slag tunnel fireproof coatings.docx

Effectofalkali-activatedsolutionconcentrationontheperformanceofalkali-activatedslagtunnelfireproofcoatingsDeng-dengZheng1,TaoJi1*,Wen-chengWang2,Hwai-chungWu1,21. CollegeofCivilEngineeringatFuzhouUniversity,350116,China2. DepartmentofCivilandEnvironmentalEngineeringatWayneStateUniversity,408202,USAAbstractTheeffectofsodiumhydroxidesolutionconcentrationontheperformanceofalkali-activatedslagtunnelfireproofcoatings(AAS-TFC),suchasbondingstrength,fireresistance,drydensityanddryingtime,etc.wasstudied.Thetestresultsrevealthat,whenthebyweightconcentrationofsodiumhydroxidesolutionislessthan10%,thebondingstrengthbeforeandafterfreezing-thawingcyclesandthedryingtimeincreasewiththeincreaseofthesolutionconcentration,andthedryingtimedecreaseswiththeincreaseofsolutionconcentration.Whentheconcentrationofsodiumhydroxidesolutionismorethan10%,theinfluenceofthesolutionconcentrationonthebondingstrength,fireresistance,drydensityanddryingtimeofAAS-TFCisnotobvious.ThechangeoftheconcentrationofsodiumhydroxidesolutiononthefireresistanceofAAS-TFCisnotobvious.Whensodiumhydroxidesolutionconcentrationwas3%,thepeiformance-to-priceratioofAAS-TFCisthehighest.OriginalityAlkali-activatedslagtunnelfireproofcoatingsareseldomstudied,andtheeffectofalkali-activatedsolutionconcentrationontheperformanceofalkali-activatedslagtunnelfireproofcoatings,especiallyfarthebondingstrengthbeforeandafterfreezing-thawingcycles,isstillnotexploredbyanyauthorwold-wide.Thereforetheoriginalityofthispaperisobvious.Keywords:Tunnelfireproofcoating;Alkali-activatedslag;Alkali-activatedsolutionconcentration;Bondingstrength;FireresistanceCorrespondingauthor:jt72,Te!+86-13609597752,Fax+0591-878932741.1 ntroductionWiththerapiddevelopmentoftunnelfireproofcoatings(TFC),thehighwaytunnelofChinahasbecomethelongestallovertheworld.Asofearly2011,thetotalnumberofthehighwaytunnelreached7384,andthecumulativelengthofthehighwaytunnelhadbecomemorethan5(X)0km.Asthetunnelisoftenusedastransportationchannelsofpowercables,fiberopticcables,aqueducts,pipelines,andsoon,whenatunnelfireaccidentshappens,theharmitcausesisveryserious,whichcanleadtothelongtimeoftrafficjam,extremelydifficultrescue,largeeconomiclossesandotherseriousconsequences,andevenmayleadtoaseriesofsocialproblems(Chinahighwaysociety.,2012;BerhahlP.,1995;WuY.,2008).Theapplicationofalkali-activatedslagcementinTFChasobviousadvantages:(1)Simplifyingformulaandreducingthecost.Becausethealkali-activatedcementhasgoodhightemperatureperformance,itsapplicationinTFCcanreduceorgetridofsomecomponentsoftraditionalTFCwithrelativelyhighprices.Forexample,duetoprotectthehealthofconstructionworkers,wegotridoftheammoniumpolyphosphateofTFCthatcanproduceodorgas.(2)Improvingthefreezing-thawingresistingcycleperformanceofTFC.Thefreezing-thawingresistingcyclicperformanceofTFChasgottenmoreandmoreattentionnowadays.ThestandardofttFireretardantcoatingofconcreteStrUCtUreS''(GA28375-2012)(ThenationalstandardofthePeople'sRepublicofChina,2012),whichwaspublishedin2012,hasspeciallyjoinedthebondingstrengthindexafterfreezingandthawingcycle.(3)Greenenvironmentalprotection.ReplacingordinaryPortlandcementwithalkali-activatedslagcementinTFC,thecarbondioxide,sulphurdioxideanddust,whichisproducedintheproductionprocessofPortlandcement,canbereduced.Itisbeneficialforenvironmentalprotection.Studieshaveshownthatthechangingoftheactivatorsolutionconcentrationhasinfluenceonthestrengthandsettingtimeofthealkali-activatedslagcement(ZhangY.Q.,2009).However,theresearchabouttheeffectoftheactivatorsolutionconcentrationonalkali-activatedslagtunnelfireproofcoatings(AAS-TFC)performanceswasstillnotavailable.Inthispaper,theactivatorsolutionconcentrationofTFCwaschanged,andtheeffectoftheactivatorsolutionconcentrationonthebondingstrength,fireresistance,drydensityanddryingtimeetc.ofAAS-TFChasbeenstudied.2 .RawmaterialsandmixproportionTFCisusuallycomposedofbondingmaterials,refractoryandheatinsulationmaterials,foammaterialsandadditives(WangX.G.,2(X)6;WangG.J.,2006).Thefoammaterials(suchasammoniumpolyphosphate,melamineandpentaerythritol,etc)ofTFCisexcluded,andalkali-activatedslagcement,asthemainbondingmaterialofTFC,wasusedtoinsteadPortlandcement.2.1 BondingmaterialsBondingmaterialsisconstitutedbythealkali-activatedslagcement,redispersiblepowderandPVA.Thealkali-activatedslagcementisconstitutedbysodiumhydroxideandslag.SodiumhydroxideisproducedbyKangpu-huiweicompanyinBeijing.SlagisproducedbyTainingconcreteplantinFuzhou.Polyvinylalcohol(PVA)isproducedbySifang-huagongcompanyinFuzhou.PVAisthetypeof1788-125,whichiswhitepowder,odorless,tasteless,andsmallerthan160mesh.2.2 RefractoryExpandedperliteisproducedbyYouchencompanyinFuzhou.Itsparticlesizeisabout3mm,anditspackingdensityis83kgm3.Expandedperliteisqualitativelight,adiabatic,non-toxic,soundabsorption,tasteless,non-combustible,etc,anditcanresisttothehightemperatureof130()C.ExpandedvermiculiteisalsoproducedbyYouchencompanyinFuzhou.Itsparticlesizeislessthan2mm,anditismaroon,anditspackingdensityof530kgm3.SepioliteisproducedbyLeibaocompanyinNanyang.Itspackingdensityis651.8kgm3,anditcanresistthehightemperatureof1700.HollowdriftbeadsareproducedbyTianticompanyinHenan.Ilsparticlesizeislessthan0.9mm,anditspackingdensityis338.5kgm3.Thenormaltemperaturecoefficientofthermalconductivityofhollowdriftbeadsis0.035W(m,K),anditcanresistthehightemperatureof1360.2.3 HeatinsulationmaterialsAluminiumhydroxideandmagnesiumhydroxidearebothproducedbyFuchencompanyinTianjing.2.4 MixproportionBasedonself-madeAAS-TFCthatwehaveinvented,theconcentrationofthesodiumhydroxidesolutionwaschangedtostudytheeffectoftheactivatorsolutionconcentrationonthemainpropertiesofAAS-TFC.Whentheconcentrationofsodiumhydroxidesolutionisover10%,itseconomicalefficiencyisnotreasonable.However,inordertostudytheinfluencelaw,theconcentrationlargerthan10%wasused.MixproportionofAAS-TFCisshowninTable1,andeachcomponentofAAS-TFCisbymasspercentage(%).Sodiumhydroxidesolutionconcentrationisthemasspercentageconcentration,andthedosageofsodiumhydroxideisthemassratio(%)ofsodiumhydroxideandothersolidcomponents(asshowninTable.l)(notincludesodiumhydroxide).Watercontentisthe70%ofthesolidcomponentsthatdoesnotcontainsodiumhydroxide.First,westirredtheothersolidcomponentthatdidnotcontainsodiumhydroxide,andthenwemadethesodiumhydroxidesolutionbydissolvingsodiumhydroxideinwater.Atlast,thesodiumhydroxidesolutionwaspouredintotheothersolidcomponent.TableMiXPrOPOrtiOnOfSoIidComPOnentSOfAAS-TFCConcentSlagPVARedispersiblepowderExpandedperliteExpandedvermiculiteSepioliteHollowdriftbeadsMagnesiumhydroxideAluminiumhydroxideNo.rationofNaOHsolution(%)DosageofNaOH110.742.81.32.116.113.582.63.310.3221.442.81.32.116.113.582.63.310.3332.242.81.32.116.113.582.63.310.3442.942.81.32.116.113.582.63.310.3553.642.81.32.116.113.582.63.310.3664.542.81.32.116.113.582.63.310.3775.342.81.32.116.113.582.63.310.3886.142.81.32.116.113.582.63.310.3996.942.81.32.116.113.582.63.310.310107.842.81.32.116.113.582.63.310.311129.542.81.32.116.113.582.63.310.3121512.442.81.32.116.113.582.63.3103132017.542.81.32.116.113.582.63.310.33 Testmethods3.1 FireresistanceBasedonthefireresistanceperformancetestmethodofFireretardantcoatingofconcretestructures(GA28375-2012)(ThenationalstandardofthePeople'sRepublicofChina,2012),asmallslabmethodwasusedbasedonourinvestigation.ThestrengthgradeofsmallslabconcretemettherequirementsofC30.Thesizeofsmallslabwas300mm×300mm×100mm.A12reinforcementbarwasplacedat25mmdistancefromthebottomofthesmallslab.The12reinforcementbarwasplacedinthehorizontalplanegeometrycenterofsmallslab.Thermocouplewireswereplacedatthebottomoftheslabandsteelsurface,respectively.ThepositionsofthesteelandthethermocouplewireareshowedinFigure1.(a) Front view(b) B - B sectionFigure1Sketchofsmallslabmethod1- concreteslab,3-coating,4-thermocouple,5-12reinlbrcemen(bar,6-firegun.7-fireregionsprayedbyfiregun.AfiregunwasusedtoheatthecenterofonesideofconcreteslabthatcoatedwithTFC.ThefiregunwasproducedbyYuanhun-Shukongcompany,itsmodelwasTKT-9607.Thefiregungeneratedheatbyburningbutanegas.Thethermocouplemeasuredthetemperaturechangesofthebottomofconcreteslabandthesurfaceofsteelbar(namely4asshowninFigure1),respectively,whichwasconnectedtothestaticstraincollectionbox.ThetypeofthestaticstraincollectionboxisD3618.Themeasuredtimewasatintervaloftwohours.3.2 BondingstrengthThebondingstrengthtestmethodrefersto44Sandtexturedbuildingcoatingswithsyntheticresinemulsion”(JGT24-2000)(TheconstructionindustrystandardofthePeople'sRepublicofChina,2000).Thebondingstrengthiscalculatedaccordingtothefollowingformula:Where,isthebondstrength,Pa;Pistensileload,N;Aisthebondingarea,m2.3.3 Freeze-thawcycleThefreeze-thawcycletestmethodreferstouFireretardantcoatingofconcreteStrUCtUres”(GA28375-2012).3.4 DryingtimeThedryingtimetestmethodisthefingercontactmethodaccordingtoGB/T(1728-1979)(ThenationalstandardofthePeople,sRepublicofChina,2012).Useyourfingerstotouchcoatingsurface.Ifyoufeelalittlesticky,andmeanwhilenocoatingsgluetoyourfingers,whichshowsthatthesurfaceofTFCisdrying.ThedryingtimeofAAS-TFCisrelativelyshort,sowetesteditatintervalof3min.4Testresultsandanalysis4.1 BondingstrengthWiththeincreasingofsodiumhydroxidesolutionconcentration,thechangelawofbondingstrengthbeforeandafterfreezingandthawingcycleofAAS-TFCisshowninFigure2.Figure 2 Relation between sodium hydroxide solution concentration and bond strengthFigure2showsthatthechangelawofbondingstrengthbeforefreezingandthawingcycleofAAS-TFCissimilartothatafterfreezingandthawingcycle,whereBisbeforefreezingandthawingcycle,andAisafterfreezingandthawingcycle.Whenthebyweightconcentrationofsodiumhydroxidesolutionasanactivatorincreasesfrom1%to10%,thebondingstrengthimproves,especiallyattheearlystage.Whenthebyweightconcentrationofsodiumhydroxidesolutionasanactivatorismorethan10%,thechangesofthebondingstrengthisnotobvious.Whensodiumhydroxidesolutionconcentrationislow,withtheincreasingofconcentrationofsodiumhydroxidesolution,theactivationofslagincreases,andthehydrationdegreeofalkali-activatedslagcementincreases,whichleadstohigherbondingstrengthofAAS-TFC.Accordingto',Fireretardantcoatingofconcretestructures'*(GA28375-2012),thebondingstrengthafterfreeze-thawcyclesshouldbelargerthan0.15MPa,sotheconcentrationofthesodiumhydroxidesolutionshouldbenotlessthan3%.4.2 FireresistanceperformanceWiththeincreasingofsodiumhydroxidesolutionconcentration,thechangelawofthefireresistanceperformancebeforeandafterfreezingandthawingcycleofAAS-TFCisshowninFigure3.200(a)Concretesurfacetemperatures(b)SteelsurfacetemperaturesFigure3RelationbetweensodiumhydroxidesolutionconcentrationandfireresistanceperformanceFigure3showsthattheconcentrationofsodiumhydroxidehaslittleinfluenceonthefireresistance,sotheconcentrationofsodiumhydroxideisnotacriticalfactoraffectingthefireresistanceofAAS-TFC.Becauseconcretesurfacetemperaturesarelessthan380andsteelsurfacetemperaturesarelessthan250°C,thefireresistanceperformanceofAAS-TFCmeetstherequirementsofspecification.4.3 DrydensityWiththeincreasingofsodiumhydroxidesolutionconcentration,thechangelawofthedrydensityperformancebeforeandafterfreezingandthawingcycleofAAS-TFCisshowninFigure4.Figure4RelationbetweensodiumhydroxidesolutionconcentrationanddrydensityBycontrastingFigure4andFigure2,thechangelawofdrydensityissimilartothatofthebondingstrengthofAAS-TFC.Whentheconcentrationofsodiumhydroxidesolutionislessthan10%,theactivationofslagincreases,andthehydrationdegreeofalkali-activatedslagcementincreases,andmorefreewaterisconvertedintochemicalcombinedwater,whichleadtothedrydensityincreasing.Thereforethechangelawofdrydensityisassociatedwiththehydrationdegreeofalkali-activatedslagcement.Duetothelimitationofslagamount,whentheconcentrationofsodiumhydroxidesolutionishigherthan10%,theeffectofsodiumhydroxidesolutionconcentrationonthedrydensityofAAS-TFCisnotobvious.Specification4requiresthedrydensityshouldbelessthan700kgm3.Therefore,thedrydensityofeachgroupmeetstherequirementsofthespecification.4.4DryingtimeThedryingtimedirectlyaffectstheconstructionperiodofAAS-TFC,soitisaveryimportantindicator.ThechangelawofthedryingtimeofAAS-TFCwiththeincreasinghydroxidesolutionconcentrationofsodiumisshowninFigure5.45423936'3330181512、962468101214161820C(%)Figure5Relationbetweensodiumhydroxidesolutionconcentrationanddrj,ingtimeFigure5showsthatwiththeincreasingofthesodiumhydroxidesolutionconcentration,thedryingtimebecomesshort,especiallyattheearlystage.Withtheincreasingofsodiumhydroxidesolutionconcentration,theactivationofslagincreases,andthesettingspeedofalkali-activatedcementbecomesfaster.Duetothelimitationofslagamount,whentheconcentrationofsodiumhydroxidesolutionfurtherincreases,thesettingspeedofalkali-activatedcementbecomesslower.5 OptimalmixproportionAccordingtothetestresultsabove,increasingthesodiumhydroxidedosagewouldincreasethecostofAAS-TFC,themixproportionofAAS-TFCisbestwhentheconcentrationofsodiumhydroxidesolutionis3%,becausetheperfbrmance-to-priceratiooftheAAS-TFCisthehighest.ThereforetheoptimalmixproportionofAAS-TFCisNo.3asshowninTable1.6 ConclusionsWithsodiumhydroxidesolutionconcentrationvariation,thebondingstrengthofalkali-activatedslagtunnelfireproofcoatings(AAS-TFC)beforefreeze-thawcycleissimilartothatafterfreeze-thawcycle.Whenthebyweightconcentrationofsodiumhydroxidesolutionincreasesfrom1%to10%,thebondingstrengthimproves,especiallyattheearlystage.Whentheconcentrationofsodiumhydroxidesolutionismorethan10%,thechangesofthebondingstrengthisnotobvious.TheconcentrationofsodiumhydroxidesolutionhaslittleinfluenceonthefireresistanceofAAS-TFC.Whenthebyweightconcentrationofsodiumhydroxidesolutionincreasesfrom1%to10%,thedrydensityimproves,especiallyattheearlystage.Whentheconcentrationofsodiumhydroxidesolutionismorethan10%,thechangesofthedrydensityisnotobvious.Thedryingtimebecomesshortwiththeincreasingofthesodiumhydroxidesolutionconcentration,especiallyattheearlystage.Whensodiumhydroxidesolutionconcentrationwas3%,theperformance-to-priceratioofAAS-TFCisthehighest.AcknowledgementsThefinancialhelpofthe“Industry-UniversityAnstitute''cooperationmajorprojectsofScienceandTechnologyAgencyofFujianProvince(ProjectNo.,2013H6013)isgratefullyacknowledged.References- 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