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1、Effectofalkali-activatedsolutionconcentrationontheperformanceofalkali-activatedslagtunnelfireproofcoatingsDeng-dengZheng1,TaoJi1*,Wen-chengWang2,Hwai-chungWu1,21. CollegeofCivilEngineeringatFuzhouUniversity,350116,China2. DepartmentofCivilandEnvironmentalEngineeringatWayneStateUniversity,408202,USAA
2、bstractTheeffectofsodiumhydroxidesolutionconcentrationontheperformanceofalkali-activatedslagtunnelfireproofcoatings(AAS-TFC),suchasbondingstrength,fireresistance,drydensityanddryingtime,etc.wasstudied.Thetestresultsrevealthat,whenthebyweightconcentrationofsodiumhydroxidesolutionislessthan10%,thebond
3、ingstrengthbeforeandafterfreezing-thawingcyclesandthedryingtimeincreasewiththeincreaseofthesolutionconcentration,andthedryingtimedecreaseswiththeincreaseofsolutionconcentration.Whentheconcentrationofsodiumhydroxidesolutionismorethan10%,theinfluenceofthesolutionconcentrationonthebondingstrength,firer
4、esistance,drydensityanddryingtimeofAAS-TFCisnotobvious.ThechangeoftheconcentrationofsodiumhydroxidesolutiononthefireresistanceofAAS-TFCisnotobvious.Whensodiumhydroxidesolutionconcentrationwas3%,thepeiformance-to-priceratioofAAS-TFCisthehighest.OriginalityAlkali-activatedslagtunnelfireproofcoatingsar
5、eseldomstudied,andtheeffectofalkali-activatedsolutionconcentrationontheperformanceofalkali-activatedslagtunnelfireproofcoatings,especiallyfarthebondingstrengthbeforeandafterfreezing-thawingcycles,isstillnotexploredbyanyauthorwold-wide.Thereforetheoriginalityofthispaperisobvious.Keywords:Tunnelfirepr
6、oofcoating;Alkali-activatedslag;Alkali-activatedsolutionconcentration;Bondingstrength;FireresistanceCorrespondingauthor:jt72,Te!+86-13609597752,Fax+0591-878932741.1 ntroductionWiththerapiddevelopmentoftunnelfireproofcoatings(TFC),thehighwaytunnelofChinahasbecomethelongestallovertheworld.Asofearly201
7、1,thetotalnumberofthehighwaytunnelreached7384,andthecumulativelengthofthehighwaytunnelhadbecomemorethan5(X)0km.Asthetunnelisoftenusedastransportationchannelsofpowercables,fiberopticcables,aqueducts,pipelines,andsoon,whenatunnelfireaccidentshappens,theharmitcausesisveryserious,whichcanleadtothelongti
8、meoftrafficjam,extremelydifficultrescue,largeeconomiclossesandotherseriousconsequences,andevenmayleadtoaseriesofsocialproblems(Chinahighwaysociety.,2012;BerhahlP.,1995;WuY.,2008).Theapplicationofalkali-activatedslagcementinTFChasobviousadvantages:(1)Simplifyingformulaandreducingthecost.Becausethealk
9、ali-activatedcementhasgoodhightemperatureperformance,itsapplicationinTFCcanreduceorgetridofsomecomponentsoftraditionalTFCwithrelativelyhighprices.Forexample,duetoprotectthehealthofconstructionworkers,wegotridoftheammoniumpolyphosphateofTFCthatcanproduceodorgas.(2)Improvingthefreezing-thawingresistin
10、gcycleperformanceofTFC.Thefreezing-thawingresistingcyclicperformanceofTFChasgottenmoreandmoreattentionnowadays.ThestandardofttFireretardantcoatingofconcreteStrUCtUreS(GA28375-2012)(ThenationalstandardofthePeoplesRepublicofChina,2012),whichwaspublishedin2012,hasspeciallyjoinedthebondingstrengthindexa
11、fterfreezingandthawingcycle.(3)Greenenvironmentalprotection.ReplacingordinaryPortlandcementwithalkali-activatedslagcementinTFC,thecarbondioxide,sulphurdioxideanddust,whichisproducedintheproductionprocessofPortlandcement,canbereduced.Itisbeneficialforenvironmentalprotection.Studieshaveshownthatthecha
12、ngingoftheactivatorsolutionconcentrationhasinfluenceonthestrengthandsettingtimeofthealkali-activatedslagcement(ZhangY.Q.,2009).However,theresearchabouttheeffectoftheactivatorsolutionconcentrationonalkali-activatedslagtunnelfireproofcoatings(AAS-TFC)performanceswasstillnotavailable.Inthispaper,theact
13、ivatorsolutionconcentrationofTFCwaschanged,andtheeffectoftheactivatorsolutionconcentrationonthebondingstrength,fireresistance,drydensityanddryingtimeetc.ofAAS-TFChasbeenstudied.2 .RawmaterialsandmixproportionTFCisusuallycomposedofbondingmaterials,refractoryandheatinsulationmaterials,foammaterialsand
14、additives(WangX.G.,2(X)6;WangG.J.,2006).Thefoammaterials(suchasammoniumpolyphosphate,melamineandpentaerythritol,etc)ofTFCisexcluded,andalkali-activatedslagcement,asthemainbondingmaterialofTFC,wasusedtoinsteadPortlandcement.2.1 BondingmaterialsBondingmaterialsisconstitutedbythealkali-activatedslagcem
15、ent,redispersiblepowderandPVA.Thealkali-activatedslagcementisconstitutedbysodiumhydroxideandslag.SodiumhydroxideisproducedbyKangpu-huiweicompanyinBeijing.SlagisproducedbyTainingconcreteplantinFuzhou.Polyvinylalcohol(PVA)isproducedbySifang-huagongcompanyinFuzhou.PVAisthetypeof1788-125,whichiswhitepow
16、der,odorless,tasteless,andsmallerthan160mesh.2.2 RefractoryExpandedperliteisproducedbyYouchencompanyinFuzhou.Itsparticlesizeisabout3mm,anditspackingdensityis83kgm3.Expandedperliteisqualitativelight,adiabatic,non-toxic,soundabsorption,tasteless,non-combustible,etc,anditcanresisttothehightemperatureof
17、130()C.ExpandedvermiculiteisalsoproducedbyYouchencompanyinFuzhou.Itsparticlesizeislessthan2mm,anditismaroon,anditspackingdensityof530kgm3.SepioliteisproducedbyLeibaocompanyinNanyang.Itspackingdensityis651.8kgm3,anditcanresistthehightemperatureof1700.HollowdriftbeadsareproducedbyTianticompanyinHenan.
18、Ilsparticlesizeislessthan0.9mm,anditspackingdensityis338.5kgm3.Thenormaltemperaturecoefficientofthermalconductivityofhollowdriftbeadsis0.035W(m,K),anditcanresistthehightemperatureof1360.2.3 HeatinsulationmaterialsAluminiumhydroxideandmagnesiumhydroxidearebothproducedbyFuchencompanyinTianjing.2.4 Mix
19、proportionBasedonself-madeAAS-TFCthatwehaveinvented,theconcentrationofthesodiumhydroxidesolutionwaschangedtostudytheeffectoftheactivatorsolutionconcentrationonthemainpropertiesofAAS-TFC.Whentheconcentrationofsodiumhydroxidesolutionisover10%,itseconomicalefficiencyisnotreasonable.However,inordertostu
20、dytheinfluencelaw,theconcentrationlargerthan10%wasused.MixproportionofAAS-TFCisshowninTable1,andeachcomponentofAAS-TFCisbymasspercentage(%).Sodiumhydroxidesolutionconcentrationisthemasspercentageconcentration,andthedosageofsodiumhydroxideisthemassratio(%)ofsodiumhydroxideandothersolidcomponents(assh
21、owninTable.l)(notincludesodiumhydroxide).Watercontentisthe70%ofthesolidcomponentsthatdoesnotcontainsodiumhydroxide.First,westirredtheothersolidcomponentthatdidnotcontainsodiumhydroxide,andthenwemadethesodiumhydroxidesolutionbydissolvingsodiumhydroxideinwater.Atlast,thesodiumhydroxidesolutionwaspoure
22、dintotheothersolidcomponent.TableMiXPrOPOrtiOnOfSoIidComPOnentSOfAAS-TFCConcentSlagPVARedispersiblepowderExpandedperliteExpandedvermiculiteSepioliteHollowdriftbeadsMagnesiumhydroxideAluminiumhydroxideNo.rationofNaOHsolution(%)DosageofNaOH110.742.81.32.116.113.582.63.310.3221.442.81.32.116.113.582.63
23、.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.
24、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)(ThenationalstandardofthePeoplesRepublicofChina,2012),asmallslabmethodwasusedba
25、sedonourinvestigation.ThestrengthgradeofsmallslabconcretemettherequirementsofC30.Thesizeofsmallslabwas300mm300mm100mm.A12reinforcementbarwasplacedat25mmdistancefromthebottomofthesmallslab.The12reinforcementbarwasplacedinthehorizontalplanegeometrycenterofsmallslab.Thermocouplewireswereplacedatthebott
26、omoftheslabandsteelsurface,respectively.ThepositionsofthesteelandthethermocouplewireareshowedinFigure1.(a) Front view(b) B - B sectionFigure1Sketchofsmallslabmethod1- concreteslab,3-coating,4-thermocouple,5-12reinlbrcemen(bar,6-firegun.7-fireregionsprayedbyfiregun.Afiregunwasusedtoheatthecenterofone
27、sideofconcreteslabthatcoatedwithTFC.ThefiregunwasproducedbyYuanhun-Shukongcompany,itsmodelwasTKT-9607.Thefiregungeneratedheatbyburningbutanegas.Thethermocouplemeasuredthetemperaturechangesofthebottomofconcreteslabandthesurfaceofsteelbar(namely4asshowninFigure1),respectively,whichwasconnectedtothesta
28、ticstraincollectionbox.ThetypeofthestaticstraincollectionboxisD3618.Themeasuredtimewasatintervaloftwohours.3.2 BondingstrengthThebondingstrengthtestmethodrefersto44Sandtexturedbuildingcoatingswithsyntheticresinemulsion”(JGT24-2000)(TheconstructionindustrystandardofthePeoplesRepublicofChina,2000).The
29、bondingstrengthiscalculatedaccordingtothefollowingformula:Where,isthebondstrength,Pa;Pistensileload,N;Aisthebondingarea,m2.3.3 Freeze-thawcycleThefreeze-thawcycletestmethodreferstouFireretardantcoatingofconcreteStrUCtUres”(GA28375-2012).3.4 DryingtimeThedryingtimetestmethodisthefingercontactmethodac
30、cordingtoGB/T(1728-1979)(ThenationalstandardofthePeople,sRepublicofChina,2012).Useyourfingerstotouchcoatingsurface.Ifyoufeelalittlesticky,andmeanwhilenocoatingsgluetoyourfingers,whichshowsthatthesurfaceofTFCisdrying.ThedryingtimeofAAS-TFCisrelativelyshort,sowetesteditatintervalof3min.4Testresultsand
31、analysis4.1 BondingstrengthWiththeincreasingofsodiumhydroxidesolutionconcentration,thechangelawofbondingstrengthbeforeandafterfreezingandthawingcycleofAAS-TFCisshowninFigure2.Figure 2 Relation between sodium hydroxide solution concentration and bond strengthFigure2showsthatthechangelawofbondingstren
32、gthbeforefreezingandthawingcycleofAAS-TFCissimilartothatafterfreezingandthawingcycle,whereBisbeforefreezingandthawingcycle,andAisafterfreezingandthawingcycle.Whenthebyweightconcentrationofsodiumhydroxidesolutionasanactivatorincreasesfrom1%to10%,thebondingstrengthimproves,especiallyattheearlystage.Wh
33、enthebyweightconcentrationofsodiumhydroxidesolutionasanactivatorismorethan10%,thechangesofthebondingstrengthisnotobvious.Whensodiumhydroxidesolutionconcentrationislow,withtheincreasingofconcentrationofsodiumhydroxidesolution,theactivationofslagincreases,andthehydrationdegreeofalkali-activatedslagcem
34、entincreases,whichleadstohigherbondingstrengthofAAS-TFC.Accordingto,Fireretardantcoatingofconcretestructures*(GA28375-2012),thebondingstrengthafterfreeze-thawcyclesshouldbelargerthan0.15MPa,sotheconcentrationofthesodiumhydroxidesolutionshouldbenotlessthan3%.4.2 FireresistanceperformanceWiththeincrea
35、singofsodiumhydroxidesolutionconcentration,thechangelawofthefireresistanceperformancebeforeandafterfreezingandthawingcycleofAAS-TFCisshowninFigure3.200(a)Concretesurfacetemperatures(b)SteelsurfacetemperaturesFigure3RelationbetweensodiumhydroxidesolutionconcentrationandfireresistanceperformanceFigure
36、3showsthattheconcentrationofsodiumhydroxidehaslittleinfluenceonthefireresistance,sotheconcentrationofsodiumhydroxideisnotacriticalfactoraffectingthefireresistanceofAAS-TFC.Becauseconcretesurfacetemperaturesarelessthan380andsteelsurfacetemperaturesarelessthan250C,thefireresistanceperformanceofAAS-TFC
37、meetstherequirementsofspecification.4.3 DrydensityWiththeincreasingofsodiumhydroxidesolutionconcentration,thechangelawofthedrydensityperformancebeforeandafterfreezingandthawingcycleofAAS-TFCisshowninFigure4.Figure4RelationbetweensodiumhydroxidesolutionconcentrationanddrydensityBycontrastingFigure4an
38、dFigure2,thechangelawofdrydensityissimilartothatofthebondingstrengthofAAS-TFC.Whentheconcentrationofsodiumhydroxidesolutionislessthan10%,theactivationofslagincreases,andthehydrationdegreeofalkali-activatedslagcementincreases,andmorefreewaterisconvertedintochemicalcombinedwater,whichleadtothedrydensi
39、tyincreasing.Thereforethechangelawofdrydensityisassociatedwiththehydrationdegreeofalkali-activatedslagcement.Duetothelimitationofslagamount,whentheconcentrationofsodiumhydroxidesolutionishigherthan10%,theeffectofsodiumhydroxidesolutionconcentrationonthedrydensityofAAS-TFCisnotobvious.Specification4r
40、equiresthedrydensityshouldbelessthan700kgm3.Therefore,thedrydensityofeachgroupmeetstherequirementsofthespecification.4.4DryingtimeThedryingtimedirectlyaffectstheconstructionperiodofAAS-TFC,soitisaveryimportantindicator.ThechangelawofthedryingtimeofAAS-TFCwiththeincreasinghydroxidesolutionconcentrati
41、onofsodiumisshowninFigure5.454239363330181512、962468101214161820C(%)Figure5Relationbetweensodiumhydroxidesolutionconcentrationanddrj,ingtimeFigure5showsthatwiththeincreasingofthesodiumhydroxidesolutionconcentration,thedryingtimebecomesshort,especiallyattheearlystage.Withtheincreasingofsodiumhydroxid
42、esolutionconcentration,theactivationofslagincreases,andthesettingspeedofalkali-activatedcementbecomesfaster.Duetothelimitationofslagamount,whentheconcentrationofsodiumhydroxidesolutionfurtherincreases,thesettingspeedofalkali-activatedcementbecomesslower.5 OptimalmixproportionAccordingtothetestresult
43、sabove,increasingthesodiumhydroxidedosagewouldincreasethecostofAAS-TFC,themixproportionofAAS-TFCisbestwhentheconcentrationofsodiumhydroxidesolutionis3%,becausetheperfbrmance-to-priceratiooftheAAS-TFCisthehighest.ThereforetheoptimalmixproportionofAAS-TFCisNo.3asshowninTable1.6 ConclusionsWithsodiumhy
44、droxidesolutionconcentrationvariation,thebondingstrengthofalkali-activatedslagtunnelfireproofcoatings(AAS-TFC)beforefreeze-thawcycleissimilartothatafterfreeze-thawcycle.Whenthebyweightconcentrationofsodiumhydroxidesolutionincreasesfrom1%to10%,thebondingstrengthimproves,especiallyattheearlystage.When
45、theconcentrationofsodiumhydroxidesolutionismorethan10%,thechangesofthebondingstrengthisnotobvious.TheconcentrationofsodiumhydroxidesolutionhaslittleinfluenceonthefireresistanceofAAS-TFC.Whenthebyweightconcentrationofsodiumhydroxidesolutionincreasesfrom1%to10%,thedrydensityimproves,especiallyattheear
46、lystage.Whentheconcentrationofsodiumhydroxidesolutionismorethan10%,thechangesofthedrydensityisnotobvious.Thedryingtimebecomesshortwiththeincreasingofthesodiumhydroxidesolutionconcentration,especiallyattheearlystage.Whensodiumhydroxidesolutionconcentrationwas3%,theperformance-to-priceratioofAAS-TFCis
47、thehighest.AcknowledgementsThefinancialhelpofthe“Industry-UniversityAnstitutecooperationmajorprojectsofScienceandTechnologyAgencyofFujianProvince(ProjectNo.,2013H6013)isgratefullyacknowledged.References- Chinahighwaysociety,2012.Highwaydisciplinedevelopmentresearchreport(inChinese).Chinesehighway,(1
48、5),34-42.- BerhahlR1995.Buildingenergyefficiencyandfiresafetyaspectsofreflectivecoating.EnergyandBuilding,22(3),187-191.- WUY,2008.Assessmentoftheimpactofjetflamehazardfromhydrogencarsinroadtunnels.EmergingTechnologies,16(2),246-254.- ThenationalstandardofthePeoplesRepublicofChina,2012.Fireretardantcoating
