Durability and leach-ability evaluation of K-based geopolymer concrete in real environmental conditions

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Citation for this paper:

Azarsa, P., & Gupta, R. (2020). Durability and leach-ability evaluation of K-based

geopolymer concrete in real environmental conditions. Case Studies in Construction

Materials, Vol. 13, 1-22. https://doi.org/10.1016/j.cscm.2020.e00366.

UVicSPACE: Research & Learning Repository

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Durability and leach-ability evaluation of K-based geopolymer concrete in real

environmental conditions

Peiman Azarsa, & Rishi Gupta

April 2020

© 2020 Peiman Azarsa et al. This is an open access article distributed under the terms of the Creative

Commons Attribution License.

https://creativecommons.org/licenses/by-nc-nd/4.0/

This article was originally published at:

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Case

study

Durability

and

leach-ability

evaluation

of

K-based

geopolymer

concrete

in

real

environmental

conditions

Peiman

Azarsa

a

,

Rishi

Gupta

b,

*

,1

a_Department_of_Civil_Engineering,_University_of_Victoria,_Victoria,_Canada b_Department_of_Civil_Engineering,_University_of_Victoria,_Victoria,_Canada

ARTICLE INFO

Articlehistory: Received19August2019

Receivedinrevisedform20April2020 Accepted21April2020

Keywords:

Realenvironmentalexposure Geopolymerconcrete Fly-ash Bottom-ash Potassium-based Non-destructivetests Durability Leaching ABSTRACT

GeopolymerConcrete(GPC)asanalternativetoPortlandCementConcrete(PCC)isa cement-lessand greenconstructionmaterialwhich isproducedbymixingindustrial by-productswith analkalinesolution.Inthisstudy,PCCandPotassium-based(K-based)GPCsynthesizedwith 50%ﬂy-ashand50%bottom-ashwereexposedtotherealenvironmentalconditionsto evaluatetheirchemicalmetalsleach-abilityanddurabilityover150and240daysofexposure respectively.Themix containedpotassiumhydroxideconcentrationof12molarity,potassium silicate/potassiumhydroxideratioof1.47,alkalinesolution/ashes(ﬂy-ashandbottom-ash) ratioof0.54and total aggregatecontent of1800kg/m3_._To_develop_GPC,_two_{methods of}_curing

(steamcuringanddrycuring) wereusedtoincreasethecompressivestrengthofGPC. Accordingtotheresultofcompressiontest,thecompressivestrengthofsteam-curedGPC increased3.5timeswhentemperatureelevatedfromambienttemperature(~10C)to80C. While,anincreaseincompressivestrengthofdry-curedGPCsampleswas2.3times. Non-DestructiveTests(NDT)sincludingSchmidthammer,ultrasonicpulsevelocityandresonant frequencytestwereemployedtomeasuretherelativedynamicmodulusofelasticity.Inthis study,paverblockhas beenselectedasanapplicationsincetothebest ofour knowledge,there is no work reported the effect of real environmental conditions on leach-ability and mechanicalpropertiesofK-basedGPCpaverblocks.Twoareaswerepavedwithatotalof150 GPCand210PCCpaverblocks.TheresultsoftheNDTsinarea1showthattheaveragevelocity andcompressivestrengthofGPCdecreasedapproximately11.6%and23.4%respectively. While,theaveragevelocityandcompressivestrengthofPCCdecreasedabout8.3%and8.2% respectively.Inarea2,theaveragerateofvelocityandcompressivestrengthlossofGPCwas about12.03%and19.51%respectively.Whereas,maximumdecreaseinaveragevelocityand compressivestrengthofPCCover240daysofexposurewas5.28%and9.65%respectively. Leach-abilityofGPCasanotherinnovativeaspectofcurrentstudywasalsomeasuredusing HACHstripssince the releaseofheavymetalscanbeaconcerninGPC.Theresults indicatethat duetotheheat-treatmentofGPCpaverblocks,alltheparametersincludingtotalalkalinity, totalhardness,pH,totalchlorine,phosphate,copper,ammonia,iron,nitrateandnitritewere withinthestandarddomainandwereconstantover150daysofexposure.Therelative dynamicmodulusofelasticitypowerfunctionmodelandexponentialfunctionmodelwere establishedtoﬁndasuitabledamagepredictivemodelforbothtypesofconcrete.Itwas concludedthatduetothehighervaluesofAdj.R2_for_both_GPC_(0.96)_and_PCC_(0.92),_the_power

functionrelationshipcomparedwellwiththeexponentialfunction.

*Correspondingauthorat:DepartmentofCivilEngineering,UniversityofVictoria,Victoria,Canada. E-mailaddresses:azarsap@uvic.ca(P.Azarsa),guptar@uvic.ca(R.Gupta).

1_Postal_address:_ECS_building,_Civil_engineering_department,_University_of_Victoria,₃₈₀₀_Finnerty_Rd,_Victoria,_BC_V8P_5C2.

https://doi.org/10.1016/j.cscm.2020.e00366

ContentslistsavailableatScienceDirect

Case

Studies

in

Construction

Materials

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1.Introduction

Inthepastfewdecades,emissionofCarbonDioxide(CO2)throughhumanandnaturalprocessessuchashumanactivities,

disposalofwastematerialsandconsumingnaturalresourcesisconsideredasthemostimportantcauseofclimatechange.In

theconstructionindustry,cementproductionisoneofthemaincontributorstoincreasingCO2emissionintheworld.Thatis

whytheutilizationofwastematerialintheproductionofconcretecanbeapossiblealternativetocement[1].Accordingto

Mohammadhosseini et al. [2] and Dimitriou et al. [3], greater utilization of waste materials mitigate the negative

environmentalimpacts.Sincewastematerialsareusedinnumerousapplications,itisessentialtoinvestigatetheireffecton

themechanicalpropertiesofmaterialsproduced.ThestudybyMohammadhosseinietal.[4]showsthatthemechanical

propertiesofSelf-CompactingConcrete(SCC)includingcompressivestrength,splittingtensileandﬂexuralstrengthcanbe

improvedbywater/binderratioof0.4and30%replacementofpalmoilfuelashwithcement.

Towardachievingasustainablematerialandgreenenvironment,GeopolymerConcrete(GPC)hasbeenmaterializedas

oneofthealternativestoPortlandCementConcrete(PCC)intheconstructionindustryduetoitsabilitytominimizethe

requirementfornaturalresources.GPCusesnaturalaluminosilicatematerialsactivatedbyanalkaliactivator,whicharethen

combinedwithﬁneandcoarseaggregates.Moreover,previousstudies[5,6]onGPCindicatethatitcanbeusedforthe

constructionapplicationsduetosuf_ﬁcientdurability,workableslump,andcomparablegradeofstrengthtoitscounterpart

PCC.ThestudiesbyHardjasaputraetal.[7]andZerzourietal.[8]indicatethatGPCoffersconsiderabledurabilityand

mechanical properties compared to conventional concrete including compressive strength, ﬂexural strength, elastic

modulus,sulfuricacidattackresistanceetc.Pereiraetal.[9]pointedoutthatbothGPCandPCCachievedsimilarcompressive

strength(̴60MPa)upto2yearsofageing.Inaddition,Nabeeletal.[10]reportedthatGPCsynthesizedbyﬂy-ashandslaghad

lowerUltrasonicPulseVelocity(UPV)thanOrdinaryPortlandCement(OPC).However,Nabeeletal.[10]alsomentionedthat

bothGPCandOPCwithUPVrangeof3.5–4.5Km/sarecategorizedas“good”qualityconcreteatageof7daysand28days.

Fly-ashisoneofthemainconstituentsofGPCthatispulverizedandblownwithairintothefurnacewhereitignites,

generatesheatandformsash.Fly-ashisapozzolanmaterial,containingaluminousandsiliceouswhichformsacompound

similartocement.AccordingtoAbualrousetal.[11],themosteffectivelineofattacktoincreasethewastematerialsamount

inlimitedlandsandreduceCO2emissionisusingﬂy-ashasasupplementarycementitiousmaterialorpartialsubstitution

forclinkerproduction.Itisreportedthatabout80%oftheunburnedmaterialorﬂy-ashisentrainedintheﬂuegaswhen

pulverizedcoalisburnedinadrycondition.Theremaining20%oftheashisdrybottom-ashthathassimilarchemical

properties toﬂy-ash, consisting of silica and alumina [12]. However, often ignored, bottom-ash as partof the

non-combustibleresidueofcombustioninafurnacecanalsobeusedtoproduceagreenconstructionmaterial.Thatiswhy,inthe

currentstudy,attempts havebeenmadetoproduceGPC madebycombination ﬂy-ashandbottom-ash. Thaarriniand

Ramasamy[13]reportedthatbottom-ashbasedGPCwithSodiumHydroxide(NaOH)andSodiumSilicate(Na2SiO3)ratioof2

yieldedacompressivestrengthof41.53MPaand48.55MPaunderambientandsteamcuring(60C)conditionsrespectively.

Theutilization of ﬂy-ashor bottom-ashtoproduce GPC requiresan alkalinesolution. Themost commonalkaline

solutionsusedinGPCstudiesareNaOHandNa2SiO3[14–18].However,afewstudiessuchasSakkasetal.[19]aswellas

Hosanetal.[20]reportedthatthecombinationofalkalinesolutionsuchasPotassiumHydroxide(KOH)andsolublesilicate

suchasPotassiumSilicate(K2SiO3)canalsobeusedintheproductionofGPC.Sabithaetal.[21]andBakharevetal.[22]

reportedthatalthoughsodium-basedactivatorsarebroadlyusedfortheproductionofGPC,potassium-basedactivatorsare

also claimed to decrease the initial setting, improve the geopolymerization process and consequently, increase the

compressivestrengthofGPCaswellasitsworkability.Therefore,inthis studyattemptshavebeenmadetodevelop a

Potassium-Based(K-based)GPCusingauniquecombinationofﬂy-ashandbottom-ash.Table1showstheﬂowofknowledge

onthedevelopmentofGPC.

1.1.Researchsigniﬁcance

Sincetheconsumptionofbottom-ashiscomparativelylimited,utilizingthisby-productmaterialisoneofthecritical

challengesinrecentdecades[23,24].Hence,oneofthemainobjectivesofthecurrentstudyistodevelopaK-basedGPC

madebyacombinationof50%ﬂy-ashand50%bottom-ash.Further,theknowledgegaponmechanicalpropertiesand

leach-abilityunderrealenvironmentalexposureisﬁlled.Inthisstudy,GPCpaverblockhasbeenselectedasanapplicationsince

thereis nowork authorscouldﬁnd thatreports theeffect oflow temperatureand wetting-dryingonK-basedGPC’s

performanceunderrealenvironmentalconditions.Asalaboratoryinvestigation,Khandoletal.[25]pointedoutthatﬂy-ash

basedalkaliactivatedpaverblockhassuperiorcompressive strength,abrasionresistance, andlowerwaterabsorption

comparedtoitscounterpartOPC.

LeachingassessmentofGPCisanotherimportantconcernandmatterofinterestinengineeringconcepts,whichmustbe

knownwhenusingthismaterialinexposedapplications.Numerousstudies[26–28]haveassessedtheleach-abilityofPCC,

however,thereisnoinformationavailableforK-basedGPCmadebyacombinationofﬂy-ashandbottom-ash.Moreover,

testsinrealenvironmentalconditionsincludingcoldclimatestoestimatetheinteractionofK-basedGPCleachingwith

ground-waterarenotreported.Hence,anothermainobjectiveofthepresentstudyistoinvestigatetheleach-abilityof

chemicalmetalsofbothPCCandGPCovereverythirtydaysofexposure.Izquierdoetal.[29]reportedthatﬂy-ashbased

geopolymermatrixisappropriatefortheimmobilizationofmanychemicalelementsincludingBe,Bi,Cd,Co,Cr,Cu,Nb,Ni,

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ascomparedwithﬂyash(rawmaterial).Severalknowledgegapsthatwereindicatedinthissectionarestudiedinthis

currentwork.

2.PrecursorsofGPC

2.1.Fly-ashandbottom-ash

Inthisstudy,classFﬂy-ashandbottom-ashwereselectedasﬁneparticulateconstituentsofGPCtodevelopasustainable

concretemixforconstructingpaverblocks.BasedonASTMC618[30],threeclassesofﬂy-ashwithvariouspozzolanicand

cementitiouspropertiesareavailable.Generally,classFgeneratedfromburninganthraciteorbituminouscoalisusedinthe

productionofGPC.Inthisstudy,bothﬂy-ashandbottom-ashwereobtainedfromLafargeCanadaInc.

AccordingtoareportmadebyLafargeInc.,X-RayDiffraction(XRD)wasusedtomeasurechemicalelementsofﬂy-ashand

bottom-ash.Table2showsthecomparisonbetweenchemicalcompositionsofLafargeﬂy-ashandothertypesofﬂy-ashfrom

othersources.AscanbeseeninTable2,alltheavailablechemicalelementsofthreetypesofﬂy-ashareintherangeofASTM

C618[30].Comparingthechemicalcontentsofthreetypesofﬂy-ash,CaOwasfoundinagreaterpercentageinLafarge

ﬂy-ashwhichduetothepolymerizationreactionwithhydratedmaterialsresultsinagreatercompressivestrength[31].

Bottom-ashwithcoarserparticlesizecomparetoﬂy-ashwassieved(#1.18mm)toremovelargeparticlestoincreasethe

surfaceareaofparticleusedtoultimatelyhelptoachievereasonablestrength.Table4showsthevalueofvariouschemical

elementsofthreetypesofbottom-ash.

AccordingtoTable2and Table4,thechemicalcompositionsofbothﬂy-ashandbottom-ashobtainedfromvarious

sourcesarevaried.Itcanbeattributedtothechemicalcontentofthecoalburnedandthetypeofoperationprocess[34].It

Table1

FlowofknowledgeonthedevelopmentofGPC.

References Gaps/Findings [1–3] Findings:

TheuseofwastematerialsinproductionofconcretereducedisposalofwastematerialsassociatedwithCO2emission.

Gaps:

Smallportionofwastematerialswasusedinproductionofconcrete.However,inthecurrentstudy,attemptshavebeen madetoremovecementfromthemixtureandusewastematerialsinproductionofGPC.

[4] Gaps:

Inthisstudy[4],PalmOilFuelAsh(POFA)wasusedtoenhanceperformanceofthemixture.However,theeffectofboth ﬂy-ashandbottom-ashondurabilityofGPCisstillquestioned.Thatiswhyinthecurrentstudy,NDTswereemployedto investigatedurabilityofGPCmadebybothﬂy-ashandbottom-ash.

[5,6] Findings:

BothstudiesshowedthatGPCisapropersubstitutetocement-basedconcretewhichisenvironmentallyfriendly constructionmaterial.GPCuseslowamountofnaturalresources,emitslessCO2andhassuperiormechanicalproperties.

[7,8] Findings:

TheinvestigationofvariouspropertiesofGPCincludingelasticmodulus,ﬂexuralstrengthandcompressivestrengthetc.in bothnormalandaggressiveconditionsshowedthatGPCsamplesareslightlyalteredcomparedtoitscounterpartPCC. [9,10] Gaps:

ThesetwostudiesinvestigatedmechanicalpropertiesofGPCmadebyfly-ash,slagandmetakaolin.However,inthe currentstudy,attemptshavebeenmadetocreateadurableGPCmadebyfly-ashandbottom-ash.Moreover,authorscould notfindanyresearchonmechanicalpropertiesofGPCmadebyfly-ashandbottom-ashinpaverblockapplication. [11,12] Findings:

Basedontheresults,fly-ashcanbeusedasaPozzolanandfineaggregateinconcrete.Moreover,thisisthemost sustainableapproachtoreducingtheamountoffly-ashdisposal.

Gaps:

Thesestudiesonlycompareddifferenttypesofﬂy-ashinconcrete.However,hugeamountofbottom-ashisstilldisposed allovertheworld.Thatiswhy,theauthorsofthecurrentstudyusedbottom-ashasoneofthemainprecursorsofGPC. [13] Findings:

Thisstudyshowedthatbottom-ashalsocanbeusedtoproduceadurableGPCwithcompressivestrengthrangefrom about11–49MPa.

Gaps:

Inthecurrentstudy,themechanicalpropertiesanddurabilityofGPCpaverblockshavebeeninvestigatedinreal environmentalconditionsandcomparedwithitscounterpartPCCpaverblocks.

[14–22] Gaps:

Itiswell-knownthatNa-basedsolutionisbasicallyusedinproductionofGPC.However,notmuchworkreportedonthe mechanicalpropertiesofK-basedGPCpaverblocksinrealenvironmentalconditions.Inthecurrentstudy,NDTssuchas UPVwereusedtoinvestigatedurabilityofK-basedGPCpaverblocks.

Contributionofthis currentstudy

Asaforementioned,themechanicalpropertiesanddurabilityoffly-ashandbottom-ashinGPChavebeenexploredby manyresearchers[1-22].However,notmuchinformationisavailableonthedurabilityandleachingofchemicalmetalsof K-basedGPCmadebycombinationof50%fly-ashand50%bottom-ashinrealenvironmentalconditionsassociationwith realtrafficload.Thatiswhy,thisstudycreatesaparadigmforfuturepracticalexecutionofthisnewgenerationofconcrete calledGPC.

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shouldbenotedthatthereisnostandardreportedthespeciﬁcation/limitationforutilizationofbottom-ashinaconcrete mixture.

Table5showstherangeofotherpropertiesofbothﬂy-ashandbottom-ashobtainedfromtheMaterialSafetyDataSheets

(MSDS)ofLafargeCanadaInc.Thephysicalpropertiesofbottom-ashsuchassoundnessarenotpreciselymeasuredby

LafargeCanadaInc.becausebottom-ashisnottypicallyusedintheconstructionindustry.

ThemixdesignshowninTable6wasderivedafterinitialtrialexperimentsonmortarsperformedintheFacilitiesfor

InnovativeMaterialsandInfrastructureMonitoring(FIMIM)bytheauthors[36–38].Trafﬁcisoneofthemostfactorsinpaver

blockdesign.Thedeteriorationcausedtopaverblocksbytrafﬁcdependsonweightofthevehiclesandnumberofload

repetitionsoverthetrafﬁcanalysisperiod.Inordertoquantifythisdeterioration,thenumberofEquivalentSingleAxleLoads

(ESAL)shouldbecalculated.IS15658standard[39]recommendeddifferentgradeofpaverblocksforvariousconstruction

areasandtrafﬁccategories.InaccordancetoIS15658standard[39],thegradeofM35(f’C=35MPa)wasconsideredforthis

studybecauselessthan150commercialvehiclesdailyusedtheparkingarea.Theconcentrationof12Molarity(M)and50:50

%massratioofbottom-ashtoﬂy-ashwereselectedtoachievetargetstrengthof35MPa.Thistargetstrengthwaschosento

Table3

Physicalpropertiesofﬂy-ash.

Fly-ash ASTMC618[30] Finenessretainedon45mm(No.325sieve) 17.3% <34%

(complies) StrengthactivityindexwithPortlandcement%ofcontrolat28days 99% >75%

(complies) Waterrequirement,percentofcontrol 100% <105%

(complies) Autoclaveexpansion 0.04% <0.8% (complies) Density 2.65Mg/m3 _<_5% (complies) Table2

ComparisonbetweenchemicalcompositionsofLafargeﬂy-ashandothertypesofﬂy-ash.

Properties Fly-ash(%)Currentstudy(Lafarge) Fly-ash(%)[32] Fly-ash(%)[33] ASTMC618(%)[30]

SiO2 47.1 62.04 59.7 70(min) Al2O3 17.4 25.5 27.51 Fe2O3 5.7 4.28 4.91 CaO 14 3.96 1.45 N/A MgO 5.4 1.27 1.18 N/A SO3 0.8 0.73 0.16 5.0(max)

LOI 0.19 N/A 2.66 6.0(max)

Na2O N/A 0.46 0.82 N/A

K2O N/A N/A 2.39 N/A

TiO2 N/A 1.33 N/A N/A

P2O5 N/A 0.31 N/A N/A

Mn2O3 N/A N/A N/A N/A

Thephysicalpropertiesofﬂy-ashshowninTable3wereanalyzedattheLafargeSeattleConcreteLab.ItcanbeseeninTable3thatallthephysicalproperties ofusedﬂy-ashinthisstudycomplieswiththerequirementofASTMC618[30].

Table4

ComparisonbetweenchemicalcompositionsofLafargebottom-ashandothertypesofbottom-ash.

Properties Bottom-ash(%)Currentstudy(Lafarge) Bottom-ash(%)[34] Bottom-ash(%)[35]

SiO2 60.11 22.90 19.12 Al2O3 14.35 0.18 12.03 Fe2O3 5.92 11.39 9.31 CaO 10.40 17.93 43.11 MgO 4.49 1.0.4 2.11 SO3 0.10 0.73 2.39

LOI 0.00 N/A N/A

Na2O 2.232 3.68 2.35

K2O 1.766 N/A 0.84

TiO2 0.892 N/A 2.48

P2O5 0.200 N/A 2.62

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produceGPCpaverblocks withpropertiescomparabletothatofcommerciallyavailablePCCpaverblocksand tolater

comparethedurabilityofthesetwotypesofpaverblocksinrealenvironmentalconditions.However,theproprietarymix

designofPCCpaverblockswasnotrevealedbythemanufacturer.CommerciallyproducedPCCpaverblockswerepurchased

fromAbbotsfordConcreteProductsManufacturerofAbbotsford,B.C.,Canada.

2.1.1.Morphologyofﬂy-ashandbottom-ash

AscanningElectronMicroscope(SEM)wasperformedusingHitachiS-4800tocaptureimagesofﬂy-ashandbottom-ash

attheAdvancedMicroscopyFacility(AMF)oftheUniversityofVictoria.Athinlayerofcarbonwassputteredonthesurfaceof

ashestoincreasetheconductivityofparticles.TheSEMacceleratingvoltageof15.0KVwasused.

Basically,ﬂy-ashparticlesaredividedintothreeclasses:solidsphere,cenospheresandplerospheres.Cenospheresﬂy-ash

haslowerbulkdensity,greaterthermalresistance,higherworkabilityandsuperiorstrength[40].While,plerospheresare

createdbyimpregnatedcenosphereswithmicro-spheres,whichiswhyplerospheresareheavierthancenospheresdueto

extraweightofbaggedmicrospheres[41].

AscanbeseeninFig.1,ﬂy-ashparticlesareglassy,sphericalinshapeandthereisnoevidenceofcenospheres(totally

hollow)andplerospheres(ﬁlledwithseveraltinyspheres)shapes.Generally,lowerﬁnenessandlowcarboncontentin

ﬂy-ashdecreasethewaterdemandofconcrete[42]duetoitsspeciﬁcsurfacerole[43].Table2showsthatLossofIgnition(LOI)

ofusedﬂy-ashinthecurrentstudyis0.19%.Fly-ashwithlessthan4%LOIisconsideredaslowcarboncontentﬂy-ash.

Fig.1(a)&(b)presentthatallﬂy-ashparticlesaresphericalglassy.Thesphericalglassyshapeofﬂy-ashparticlesisalso

reportedbyDavidovits[44].

Table5

Therangeofotherpropertiesofbothﬂy-ashandbottom-ash.

Material Appearance Odor pH Boilingpoint Speciﬁcgravity Solubility

Fly-ash Gray/BlackorBrown/Tan(Powder) odorless 412 >1000_C _2.02.9_(water₌₁₎ _Water:_<5%_(slightly)

Bottom-ash Gray/BlackorBrown/Tan(Powder) odorless 412 >1000_C _2.02.9_(water₌₁₎ _Water:_<5%_(slightly)

Table6

MixproportionsofK-basedGPC.

Material Content(Kg/m3₎ Flyash 194 Bottomash 194 Coarseaggregates 1170 Sand 630 KOH(12M) 85.16 K2SiO3 125.74 ExtraWater 38.71

AirEntrainedAdmixture 1.5

Fig.1.SEMmicrographofﬂy-ashparticles.

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Amagniﬁcationof1200xisusedbothinFigs.1and2foreasycomparison.Basedontheseobservations,itisexpectedthat

replacementofﬂy-ashwithanyamountofbottom-ashwouldnegativelyimpactonworkability,sincenotallbottom-ash

particleswerefoundtobespherical.

Fig.2(a)and(b)wererandomlyselectedtocharacterizetheshapeofbottom-ashparticles.Itcanbeseenthatatthe

acceleratingvoltageof15.0KV,non-uniformshapeswithasmallamountofsphericalshapeweredetectedinbottom-ash

samples.

Inaccordancetoapreviousstudyonmicrostructureofﬂy-ashandbottom-ashperformedbythecurrentauthors[45],the

particlesizeofﬂy-ashwasabout1–20

m

mwithaveragesizeof10

m

m.While,themeansizeoftheroundedshape

bottom-ashparticleswas58.53

m

m.Theaverageheightandwidthoftheirregularshapedbottom-ashparticleswas22.59

m

mand

12.78

m

mrespectively.

2.2.Alkalinesolution

Asaforementioned,acombinationofalkalinesolutionandsolublesilicateisneededtobeginthegeopolymerization

process.Inthisstudy,attemptshavebeenmadetoimprovethedurabilityofGPCmadebyacombinationofKOHandK2SiO3,

aslimitedinformationisavailableonsuchtypeofGPC.TheindustrialgradeKOH_ﬂakesobtainedfromSigma-AldrichPrivate

Ltd,Canadawasusedinthiswork.

Potassium silicate powder (AgSil 16) obtained from PQ Corporation (USA) was used in this study. The chemical

compositionofK2SiO3obtainedfromtheMSDSoftheproductisshowninTable7.

2.3.Aggregates

FineaggregatesandcoarseaggregateswereobtainedfromaquarryinBritishColumbia,Canadawitharelativedry

densityof2.67and2.71respectively.Thewaterabsorptionratioofﬁneaggregatesandcoarseaggregateswere0.79%and

0.69%respectively.Finenessmoduliofthecoarseandﬁneaggregatesweremeasured6.85and3.54respectively.Theparticle

sizedistributionofcoarseandﬁneaggregatesweremeasured(showninFig.3)inaccordancewithASTMC33[46].

3.Methodofcastingandcuring

3.1.Specimenpreparation

Inthisstudy,300GPCpaverblockswerecastattheCivilEngineeringMaterialsFacilityattheUniversityofVictoriain

accordancewithASTMC192[47].

Fig.2.SEMmicrographofbottom-ashparticles.

(a)&(b)Tworandomareasselectedtocharacterizetheshapeofbottom-ashparticles.

Table7

ChemicalcompositionofK2SiO3.

Compound K2O SiO2 H2O

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Firstofall,theKOHsolutionwaspreparedbymixingKOHﬂakesintowater24hpriortothebatchingday.Secondly,

sandandcoarseaggregatesweremixedfor30sindrycondition.Asheswereaddedtoaggregatesandmixedforanother

30s.Solutionswerethenaddedtothedrymaterialsandmixeduntiluniformity(̴3min),followedbya3minrestperiod,

followedby2minofﬁnalmixing.Thepreparedmaterialwasplacedintomoldsandvibratedusingatablefor30sto

dischargeairbubblestothesurface.Aftervibration,themoldswerecoveredwithaplasticsheetinthelabenvironment

(approximate relative humidity range of 45 %–70 % and approximate temperature range of 5C–15_C); _and _were

demoldedafter24h.

3.2.Curingmethods

Various trialmix designs werecreated to achieve a strength target of 35MPa. Different curingtemperatures and

durationstestedoncylindricalsampleswereselectedtodevelopGPCsincethecuringtemperatureanddurationisacritical

parameterinthegeopolymerizationprocesstoobtainhigherstrength.Twotypesofacceleratedcuringmethodswereused

inthisstudy:

3.2.1.Drycuring

Sampleswerekeptinanovenattemperaturesof30,45,60,80Cforaperiodof24hfollowedby24hofambientcuring.

3.2.2.Steamcuring

Halfofthebucketswereﬁlledwithwaterandthenthesampleswereplacedintothebuckets.Thebucketsweresealedup

topreventexcessiveevaporationof waterduringthecuringprocessandthesampleswerethenkeptintotheovenat

temperaturesof30,45,60,80C.Authorsrefertothiscuringregimeas“steamcuring”inthispaper.Lastly,thepaverblocks

wereremovedafter24handwereleftatambienttemperature.Basedontheresultsofthecompressivestrengthtest,steam

curingatatemperatureof80Cwaschoseninthepresentresearchasthecuringmethod.

Fig.4(a)showsalltherawmaterialsusedintheproductionofGPC.Fig.4(b)alsoshowstheimmersedpaverblockinto

waterandcuredat80Ctoachievehighercompressivestrength.Fig.4(c)showsthecuredpaverblockandFig.4(d)shows

thesize,colorandshapeofGPCafter28daysofcuring.

4.Effectofgeometry

Sincethegeometryofspecimensaffectstheultimatecompressivestrengthofconcrete[48,49],thecompressivestrength

ofcylindrical-shapedsampleswascomparedtothecompressivestrengthofrectangular-shapedsamples(paverblocks)in

accordancewithBritishStandardEN-206[50].

Accordingtothisstandard,compressivestrengthtestisperformedoneither150300mmcylindricalor150mmcubical

samples.Asanexample,whentheminimumspeciﬁedcompressivestrengthofacylindrical-shapedsampleforlightweight

concreteis35MPa,thecubicsampleisexpectedtobe38MPa[50].However,itismentionedinBritishStandardEN-206[50]

thatcompressivestrengthforothersizesofsamplesshouldbeestimatedfornon-representativevalues.Basedonthe

above-mentioneddiscussion,inthisproject,the100200mmcylinderstrengthwascorrelatedtothepaverblockstrengthby

performinglaboratorytests.Theseresultsarepresentedlaterinthispaper.

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5.Fieldplacementdetails

Twoareasattheentranceofparkinglot#3attheUniversityofVictoriawereselectedtoplaceatotalof150GPCand210

PCCpaverblocks.Area1 showninFig.5(a)was designatedtoinvestigatethecombinedeffectof trafﬁcloadand low

temperatureonpropertiesofGPCandPCC.Fig.5(b)(Area2)indicatesthedesignatedareaforstudyingtheeffectoflow

temperatureonlyontherelativedynamicmodulusofelasticityandleach-abilityofGPCandPCC.Paverblocksinthissection

werenotexpectedtobeexposedtoanytrafﬁcload.

Fig.5(a)showstheplacementareaof2.221m2_and₃₁_m2_for_GPC_and_PCC_paver_blocks_{respectively.}_Fig.₅_(b)_also

indicatesthattheGPCandPCCplacementsizeis10.72m2_and₁_1m2_{respectively.}_Traf_ﬁc_shown_in_Fig.₅_(c)_was_expected

tocrossstraightoverthepaverblocksandtoturnoveranexistingconcreteslab.Sobothpavertypeswereexposedtomoreor

lessthesameconditions.

6.Testmethods

InitialtestingonGPCcylindricalsampleswasperformedduringthemixoptimizationphase.Asmentionedearlier,the

highestcompressivestrengthwasachievedatatemperatureof80Cofsteamcuring.So,samplesforallsubsequenttests

werecuredatatemperatureof80C.Inthisresearch,Non-DestructiveTesting(NDT)devicessuchasreboundhammerand

ultrasonicpulsevelocitywerealsoemployedtoevaluatethepropertiesofGPCandPCCexposedtorealenvironmental

conditions.

6.1.Compressivestrengthofcylinders

Atotalof54GPCcylindricalsamples(100mmdiameterand200mmheight)weretestedinaccordancewithASTMC39

[51]usingtheForneycompressiontestingmachine#AD650.AccordingtoASTMC39[51],thecompressiveloadonthe

specimenwasappliedatarateof0.250.05MPa/s.

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6.2.Compressivestrengthofpaverblocks

According toASTM C805[52],Schmidthammer orrebound hammerprocessesthe reboundof a spring-loaded

mass impacting against the surface of a concrete sample. The Schmidt hammer knocks the concrete surface at

certain energy. Its rebound is dependent on the rigidityof the concretesurface/sample. Therebound rate can be

used to measure the concrete's compressive strength by using a conversion chart. In this study, Original Proceq

Schmidt hammer Type N/NR, as a surface hardness method, was used to measure the change in compressive

strengthof paverblocksevery monthafterinitialplacementinaccordancewithASTMC805[52].Thetestscan be

carried outin three positions including horizontal, vertically (upward or downward) and angledposition. In this

study,Schmidthammerwashitonthetopsurfaceofthepaverblocksverticallydownwardtomeasuretheirin-place

compressivestrength.According toASTMC805[52],anaverageoftenSchmidthammerreadingswascalculatedto

obtain accurate results. Moreover, Schmidt hammer was calibrated to be functioning properly after each thirty

reading using an idealtest anvil.

6.3.Ultrasonicpulsevelocity

UPVisoneoftheeffectivemethodstodetermineuniformityandqualityofconcrete.TheUPVmethodevaluates

thetraveltimeoflongitudinalultrasonicwavespassingthroughtheconcrete.Thepathlengthbetweentransducers

divided by the travel time givesthe average velocity of wave propagation. UPVis usedto checkthe existence of

internal ﬂaws and voids in accordance with ASTM C597 [53]. Velocity reduction of UPV test results shows the

internaldeteriorationofthespecimens[54].Inthisstudy,thePunditLabProceqUPVtestinstrumentwasusedwith

bandwidth, measuring resolution, pulse voltage UPV and nominal transducer frequency of 20500kHz, 0.1 us,

125500Vand24500kHzrespectively.Indirecttransmissionmethod(transducerswereheldonthesamesurface)

wasusedtoevaluatethevelocityofpaverblocksin-situ.Sincethe paverblockswereplacedonbeddingsandand

since UPV of sand is different from that of UPV of paver blocks, the optimum pulse width, length and height

parametersinthedeviceweresettothedimensionsofpaverblockssoastoonlymeasuretheUPVofpaverblocks

andeliminate anyeffectof itssurroundings.Every month,three readingswere recorded fromeach paverblockto

have accuratedata of their UPV.

Fig.5.Sitedetails.

(a)Areaforeffectoflowtemperature&trafﬁcloadinvestigation.

(b)Areaforlowtemperature,relativedynamicelasticmodulus&leach-ability. (c)Trafﬁcway.

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ThefollowingequationwasusedtopredictthedynamicmodulusofelasticityformmeasuredUPVinaccordancewith

ASTMC597[53]:

E¼

r

 ð1þ

m

Þ 1ð 2

m

ÞV

2

1

m

ð1Þ

E=dynamicelasticmodulus,GPa

r

= density in kg/m3 _(Average _measured _density _of _GPC:

_r

GPC=2439kg/m3 and average assumed density of PCC:

r

PCC=2400kg/m3)

V=measuredpulsevelocityinm/second

m

=assumeddynamicPoisson’sratio(

m

=0.24forbothtypesofconcrete)

6.3.1.Seasonalhumidityeffects

Thehumidityofmaterialschangestheirresponsetoultrasonicwavespassingthroughthem.Hence,itisimportantto

investigatetheeffectofseasonalhumidityonthevelocityofpaverblockssincethepaverblocksareexposedto

wetting-dryingcyclesanddifferenthumidityconditions.Generally,intheﬁeld,allthepaverblocksexperiencedthreehumidity

conditions:fullywet,SaturatedSurfaceDry(SSD)anddry.So,thesamelaboratoryconditionsweresimulatedtomeasurethe

effectofhumidityonvelocityandcompressivestrengthofpaverblocks.Theseresultsarereportedlater.Fig.6showsthe

averageofhighandlowtemperaturesandaveragehumidityrecordedinthecityofVictoriafromNovember2017toAugust

2018[55].TheSchmidthammerandUPVtestwereperformedover240dayswiththelowestandhighesttemperaturesof

1C–20_C_{respectively.}_These_results_are_also_reported_later.

6.4.Resonantfrequencytest

ResonantFrequencyTest(RFT)orResonantFrequencyGauge(RTG)asanewNDTmethodhasbroughtalotofattentionto

determinematerialdeterioration.However,this methodistypicallyonlyperformedina labenvironment.While, UPV

methodcanbeusedeitheron-siteorinthelaboratory.So,acomparisonbetweenrelativedynamicmodulusofelasticity

basedonRFTand UPVwas madetodevelop abetterunderstandingofanycorrelationthatexistsbetweenthesetwo

methods.RFT/RTGmethodisbasedonthedeterminationoffundamentaltransverse,longitudinalandtorsionalresonant

frequenciesofvibrationofaconcretesamplethatiscreatedbyanimpactandsensedbyanaccelerometer.

Fig.7showsdifferentpartsoftheRTG/RFTdevicewhichisdesignedforlaboratoryusage.TransverseimpactRFTandUPV

testwereperformedonthirtypaverblocks(inthelab)tomeasurethedynamicmodulusofelasticity.Inthisstudy,Olson

RFT/RTGinstrumentconsistsof aUSB poweredRTG device,BNC connection, 2oz. ball-peenhammer(sphericalhead

hammer),anaccelerometer(10mV/g)andWindows7–10devicerunningOlsoninstruments’RFT/RTGsoftwarewereused.

ThefollowingequationwasusedtopredictthedynamicmodulusofelasticityinaccordancewithASTMC215[56]:

Gd=CMn2 ₍₂₎

(12)

Where

Gd=dynamicelasticmodulus,GPa,

C=0.9464(L3_T/bt3_),_m1_,

L=lengthofGPCprism,m,

M=massofGPCcylinder(kg),

N=fundamentaltransversefrequency,Hz,

t,b=dimensionsofcross-sectionofaprism,m,

T=correctionfactor

6.5.Waterqualityassessment

Chemicalactivatorsandwastematerialscontainheavymetalsthatcanbemobilizedandcanleachintotheenvironment

[57].Hence,theleach-abilityofGPCandPCCpaverblocksweremeasuredtotracemetalsinaccordancewiththeUnited

States EnvironmentalProtectionAgencyStandard 1311 [58]. Theleaching testswereperformed usingHACH stripsto

determinethequalityofcollectedsamplewaterfromthesite.

7.Resultsanddiscussions

7.1.LaboratoryinvestigationofGPCandPCCsamples

7.1.1.CompressivestrengthofcylindricalGPCsamples

Dissolutionandgeopolymerizationofalumina-silicategelofGPCsigniﬁcantlydependonthecuringcondition.Both

highercuringtemperatureanddurationcanbeusedtoacceleratethepolycondensationprocess[59,60].Steamcuringand

drycuringmethodswereusedtoacceleratecuringofGPCatﬁvedifferenttemperaturesincludingambient,30C,45C,

60C,80C.AscanbeseenintheFig.8,highestcompressivestrengthwasachievedatatemperatureof80Cofsteamcuring.

Itwasalsoobservedthatthecompressivestrengthofsteam-curedsamplesanddry-curedsamplesincreasedbyabout3.5

and2.3timesrespectivelywhenthecuringtemperaturewaschangedfromambienttemperature(̴10_C)_to₈₀_C._Fig.₈_also

showsthatforthetypeofGPCdevelopedinthisstudy,aminimumincreaseinstrengthisrealizedwhencuringtemperature

isincreasedfromambientto30C.CompressivestrengthalmostdoubleswhenGPCissteam-curedat45Casopposedto

10C.Atalltemperatures,steamcuringoutperformsdrycuring.Theauthorsattributethistofullanduniforminternalcuring

ofsteam-curedsamples.Thisstudyalsoindicatesthatreasonablestrengthcanbeachievedat60Cofcuringandforsome

applicationsitmaynotbenecessarytocureathightemperaturessuchas80C.However,thetargetcompressivestrengthof

35MPaforthecurrentapplication/constructionarea(parkinglotwithlighttrafﬁc)wasachievedat80Cafterinitialtrial

experimentsonGPCsamples.Theabovementionedﬁndingisingood-agreementwithaperformedstudybyNoushinietal.

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[61]thatNa-basedGPCmadeonlywithﬂy-ashachievedahigherrateofcompressivestrengthrangedfrom27.4to62.3MPa

whensampleswereexposedtoelevatedtemperature(2390_C)._However,_it_should_be_noted_that_Na-based_GPC_made_only

with_ﬂy-ashslightlyreachedtohighercompressivestrengththanK-basedGPCmadeby_ﬂy-ashandbottom-ash(present

study)curedtothesametemperatureandduration.ItcanbeattributedtoloweractivationpotentialofKOHcomparedto

NaOHwhichisbecauseoftheionicdiameterdifferencebetweensodiumandpotassium[62].

7.1.2.CompressivestrengthofbothGPCandPCCpaverblocks

Sixpaverblockswerecastandlatercuredatatemperatureof80Ctoﬁndthecompressivestrengthratiobetween

rectangular-shapedandcylindrical-shapedspecimens.Thesampleswereplacedhorizontallybetweentwoplatesofthe

compressivetestingmachine.AscanbeseeninFig.9,theGPCpaverblocksamplesgiveanaveragecompressivestrength

slightlylowerthanthecylindricalsampleswiththesamecuringmethodpossiblyduetohigherstressconcentrationat

cornersofpaverblocks[63].ThisresultshowsthatBritishStandardEN-206[50]overestimatedthecompressivestrengthof

theGPCpaverblock.Onereasonforthisdiscrepancycanbeattributedtothefactthatthisstandardwasoriginallydesigned

forcalculatingthecompressivestrengthofPCCandnotGPC.

TheaveragecompressivestrengthandgeometryconversionfactorofGPCpaverblockswereabout31.4MPaand0.89

respectively.TheaveragecompressivestrengthofPCCpaverblockswas33.5MPa.NoconversionfactorforPCCpaverblocks

couldbecalculatedascommerciallyavailablePCCpaverblockswereusedandnocylinderscouldbecast.However,itis

reportedbyNgocetal.[64]thatthemeancompressivestrengthconversionfactorofcubicsamples(size150mm)and

cylindricalcompressivestrength(150300mm)is0.84.

7.1.3.EffectofhumidityonmassandvelocityofGPCandPCC

AccordingtoASTMC597[53],thehumiditylevelofconcretesamplesaffectthepulsevelocity.Laboratorysimulationof

seasonalconditionswasperformedtomeasurethemassandvelocityofpaverblocksatdifferenthumiditylevelstohavea

Fig.9.AveragecompressivestrengthofGPCandPCCpaverblocks. Fig.8.Averagecompressivestrengthofsteam-curedanddry-curedGPCsamples.

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better understanding of the effect of humidity and wetting-drying cycles on the velocity of paver blocks in real

environmentalconditions.SixGPCandPCCpaverblockswereimmersedintowatertomeasurethemassandUPVofSSDand

fullywetsamples(soakedfor14days).

Fig.10showstheaveragemassandvelocityofGPCandPCCpaverblocksinthreehumidityconditions.TheGPCsamples

showedthatthemassandvelocityratiobetweendryandfullywetconditionsisabout0.98and0.84respectively.While,it

canbeobservedfromtheresultsofPCCsamplesthatthemassandvelocityratiobetweendryandfullywetconditionsis

about0.97and0.79respectively.So,forbothtypesofconcrete,thevelocityandmassincreasedwithahigherhumiditylevel

aswouldbeexpected.Itisalsonotedthatthesusceptibilityformassandvelocitytoincreasewithanincreaseinmoisture

wassimilarforbothtypesofconcrete.

7.2.On-sitecompressivestrengthandvelocity

Fig.11isaschematicshowingtheplacementofPCCandGPCpaverblockson-site.Inarea1,codes1–8areforGPCand

codes9–22areforPCCpaverblocks.Inarea2,codes1–3areforGPCandcodes4–8areforPCCpaverblocks.Thecodes/

numbersarelaterusedaslabelsinFigs.12and13.ThetotalnumberofpaverblockrowsforGPCandPCCareshownwithred

colorandbluecolorrespectively.Threerowsshownwithgreenhatchwereconsideredjustforinvestigationoftheeffectof

trafﬁcloadbutitisbeyondthescopeofthispaper.

Therelationshipbetweencompressivestrength,averagevelocitiesofeachGPCandPCCpaverblocksareshowninFigs. 12

and13.Thecompressivestrengthandvelocityofpaverblocksweremeasuredeverymonthaftertheinitialplacement.

Fig.10.EffectofhumidityonmassandvelocityofGPCandPCC.

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(16)

7.2.1.CompressivestrengthandvelocityofGPC

Fromvisualinspection,overtheﬁrst60days,smalllocaldeteriorationofsurface(scaling)ofsomeGPCpaverblockswas

observed.ThisactionledtolargecracksextendingdownwardfromthedamagedzonetothebottomofGPCpaverblocks(̴15

blocks).Overthefollowing60days,morevoidswereavailablefororganicandinorganicsolutionstopermeatethroughthe

(17)

GPC paverblocks and produce more spallingin GPC paver blocks. After120 daysof exposure toreal environmental

conditions,thecompressivestrengthandvelocitydecreasedandﬁnally,afterapproximately240days,15%ofGPCpaver

blocksshowedreducedstrengthandvelocityandconsequently,theirtestingwasterminated.Ofthetotalplaced,85%of

paverblocksindicatedacceptableresults.

Inthisstudy,attemptsweremadetotakeallreadingsofUPVandcompressivestrengthonasingledaytominimizethe

effectofchangingenvironmentalfactors.Fig.12showsaveragecompressivestrengthandvelocityof35GPCand59PCC

paverblocksandFig.13showsaveragecompressivestrengthandvelocityof80GPCand140PCCpaverblocks.

BothFigs.12and13showthechangeinaveragecompressivestrengthandvelocityofpaverblocksover240daysof

exposure.AscanbeseeninFigs.12and13,onanaverage,thecompressivestrengthandvelocityofGPCpaverblockswere

higherthanPCCpaverblocksontheﬁrstdayofexperimentscomparedto150daysofexposure;compressivestrengthand

velocityofGPCdecreasedprogressivelyover 150daysof exposure.However,itcanalsobeseenthatthecompressive

strengthandvelocityofbothtypesofpaverblocksdecreasedslightlyfrom150daysto240daysofexposure.

Fig.12showsthatwhentheageofexposureincreasedfrom1to240days,theaveragevelocityofGPCpaverblocks(1–3)

decreased from 3523.2–3099.3GPa whereas the average velocity of PCC (4–8) paver blocks decreased from 3370.8–

3192.8GPa.ItalsocanbeseeninFig. 12thattheaveragecompressivestrengthofGPC(1–3)andPCC(4–8)decreasedby19.51

%and9.65%respectively.

Fig. 13indicatesthattheaveragevelocityofGPC(1–8)andPCC(9–22)decreasedabout11.6%and8.3%respectivelywhen

theageofexposureincreasesfrom1dayto240days.TheaveragecompressivestrengthofGPC(1–8)andPCC(9–22)also

decreasedabout23.4%and8.2%overtotalageofexposure.

AccordingtotheAmericanConcreteInstitute(ACI)Code318[65],thepastecontentisinterrelatedtomaximumaggregate

size.So,GPCpastewithsmallaggregatesizedesiresmoreamountofAEA.Hence,theauthorshypothesizethatthescalingof

damagedGPCpaverblockswasduetoaninadequateamountofAEAinthepaste.

Permeabilityis anothercauseofscalingofconcretesubjectedto frostaction.Although,GPCtendstoshowa greater

permeabilityresistancethanPCC[66],thisdoesnotmeanlowmoistureabsorption[67].Thegeneralabsenceofmicro-cracksin

theInterfacialTransitionZone(ITZ)istheprincipalreasonforlowpermeability[67].AscanbeseeninFig. 14,GPCpaverblocks

absorbedmorewaterthanPCCpaverblocks.So,thiscouldbeanotherpossiblereasonthatGPCblocksexperiencedscaling

phenomena.Thisﬁndingisingood-agreementwithaperformedstudybyAlbitaretal.[68]thatthecement-basedconcretehas

lowerwaterabsorptionandsorptivitythanﬂy-ashbasedandslag-basedGPCduetothecapillarymechanismofthepastes.

AccordingtoaperformedstudybyKhateretal.[60],thecuringregimeiscriticalforthegeopolymerizationprocessof

aluminosilicategelwhichcauseshighearlystrengthgain.However,heat-treatmentmustbeappliedinaproperwaythatit

makesasupremeconditionforthedissolutionandprecipitationofdissolvedsilicaandaluminaspecies.Overall,inthis

study,thevisualinspectionshowedthatanotherpossiblereasonforGPCdeteriorationisshortercuringdurationforthe

paverblocksduringthemanufacturingstage.

Threepitsshownwithredcolor(Fig.14)wereconsideredforcollectingwatersamplespermeatedthroughpaverblocks

andestimatingtheleach-abilityofGPCandPCC.

7.2.2.CompressivestrengthandvelocityofPCC

Inthisstudy,theinitialaveragereadingofcompressivestrengthandvelocityofPCCshowedlowervaluesthanGPCpaver

blocks. Although,contraryto commonbelief, thelow compressive strength of concrete doesnot always leadto low

durability.Basically,each1%ofaddingAEAinmatrixdecreasesthestrengthofconcretebyapproximately5%[67]andasitis

reported[67],non-airentrainedconcretewithhigherstrengthmayshowlowerfrostresistancecomparedtoairentrained

concreteduetoextraairvoidsprovidedtodecreasethehydraulicpressureduringexposuretolowtemperature.Moreover,it

isreportedbyLevyetal.[69]thatuniformlydistributionofairbubbles/AEAthroughcementpasteincreasesthefreeze-thaw

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resistanceofconcrete.So,itcanbeconcludedthatasufﬁcientamountofAEAwasaddedtothePCCmatrix.Hence,thisisone

ofthereasonsthatscalingphenomenawasnotobservedonthesurfaceofPCCpaverblocks.

7.2.3.Leach-abilityofGPCandPCCpaverblocks

Ahealthyecosystemandcleanenvironmentsareessentialtothesurvivalofmankindandotherorganisms.Leaching

assessmentofmaterialsmadebywasteby-productsisvitaltocharacterizetheleachingpotentialoftoxicmetals.Inthis

research,water-proofsheetmembraneswereusedinthefoundationofasectionofpaverblockstopreventpenetrationof

watertothesub-gradelevelandallowsamplingofwaterthathaspercolatedthroughthepaverblocksandhasbeenin

contactwiththem.Watersamplespermeatedthroughpaverblockswerecollectedintothreepits(Fig.14)totracethetotal

alkalinity,totalhardness,pH,totalchlorine,phosphate,copper,ammonia,iron,nitrateandnitrite.Everythirtydays,six

watersampleswerecollectedfromeachGPCandPCCpits.Fig. 15showsthatthepHofGPCandPCCis7.9and6.8respectively

andthesevalueswereconstantoverthetotalageofexposure.GPCpaverblocksshowhigherpHvaluesthanPCCwhichis

attributabletotheuseofKOH[29].Thisﬁndingisingood-agreementwithaperformedstudybyPoursaeeetal.[70]that

Na-basedGPCmadebyslaghasahigherpHthanPCCduetothepresenceofalkalinesolutioninGPCmixture.Furthermore,asit

isreportedbyIzquierdoetal.[71]thatheat-treatmentofGPCimprovesthematrixmicrostructure,decreasestheporosityof

concreteanddecreasestheleach-abilityofthebinder.So,itcanbeconcludedthatsteamcuringimprovedthemicrostructure

ofGPCpaverblocksandreducedtheamountofheavymetalsinwatersamples.

Totalhardnessinwaterreferstotheamountofdissolvedcalcium(Ca)andmagnesium(Mg).Generally,waterhardness

concentrationbelow60ppm is consideredas soft;60₁₂₀ppm,moderatelyhard;120₁₈₀ppm,hard,and more than180ppm,

veryhard.Koziseketal.[72]suggestedthehighestandlowestrateofCa(4080mg/l)andMg(2030mg/l)indrinkingwater

anddeﬁnedtotalhardnessasthesumofCaandMgconcentrationof24mmol/L.ThetotalhardnessofGPCandPCCis120ppm

and180ppmrespectivelyover150daysofexposure.IronasoneofthemainchemicalelementsofGPCandPCCis0.15and0.2

respectivelyoverthetotalageofexposure.Forbothtypesofconcrete,otherelementssuchaschlorine,NitrateandNitritewere

constantover150daysandtheirleach-abilitywerebelowthedetectionlimit.Theresultsshowthatallthemetalswere

immobilizedeffectivelyforbothtypesofconcretes.AlltheelementsofK-basedGPCpaverblockswereconstantover150daysas

the steam curingmethod was used to develop the paste structure [71], which is attributed to a fullreactionof

ﬂy-ashandbottom-ashparticles.ThisisalsoconﬁrmedbyZhangetal.[73]thatslag-basedGPCcuredat80Cfor8hcaneffectivelyimmobilize

chemicalmetalswhentheamountofchemicalmetalsisintherangeof0.10.3%.

7.3.Dynamicelasticmodulus

7.3.1.ComparisonbetweendynamicelasticmodulusofRFTandUPV

Inthisstudy,after180daysofexposure,thirtypaverblockswereextractedfromthesitetomakeacomparisonbetween

relativedynamicelasticmodulusderivedfromUPVandRFT.

AveragedynamicmodulusofelasticityderivedfromRFTandUPVwerecalculatedinaccordancewithASTMC215[56]and

ASTM C597[53] respectively.In this study,theUPVand thetransverseresonantfrequencyof GPCpaverblocks were

convertedtorelativedynamicelasticmodulususingEqs.(1)and(2)respectively.Atzerodaysofexposure,theaverage

relativedynamicelasticmodulifromRFTandUPVwas12.20GPaand7.78GParespectively.Acomparisonbetweendynamic

elasticmoduliofGPC[37]andreporteddynamicelasticmoduliforPCC[67]showsthatGPChaslowervaluesthanPCC.

Basically,dynamicelasticmoduliofconcreteisimprovedbythemodulusofelasticityoftherawconstituents,aggregate

porosity,propertiesof pasteandcharacteristicsof transitionzonessuchas capillaryvoids andmicro-cracks [67]. The

abovementionedﬁndingisconﬁrmedbyFangetal.[74]thatduetothevariousfactorsincludingslagreplacementlevel,

amountofmolarityetc.,thedynamicelasticmodulusofGPCmadebyﬂy-ashandslagisvariedfrom12to58GPa.

Initially,averagerelativedynamicelasticmoduliofGPCpaverblocksbeforeexposuretocoldweatherwasconsideredto

be100%tohaveauniquereferenceandthentheaveragerelativedynamicelasticmoduliofGPCafter180daysofexposure

wascalculatedandwasexpressedinpercentagetodeterminematerialdeteriorationusingthetwoNDTs.

AscanbeseeninFig.16,relativedynamicelasticmodulusdecreasedafter180daysofexposure.Itcanalsobeobserved

thattherelativedynamicelasticmoduluscalculatedusingtheRFTmethodishigherthanthatobtainedfromtheUPV

method.ThisdifferencebetweentherelativedynamicelasticmoduliofRFTandUPVcanbeduetosurfaceconditionsamong

otherreasons.About18paversblockshadunevensurfaceafter180daysofexposureandbasically,smoothnessofcontactthe

surfaceaffectsUPV[75].While,RFTcanmeasuresfrequencyevenonabumpysurface.

7.3.2.DynamicmodulusofelasticityofGPCandPCCpaverblocks

Table8showstheaveragerelativedynamicmodulusofelasticityofGPCandPCCpaverblocksplacedinarea2.Thiswas

calculatedusingUPVvalues.Ascanbeseen,therelativedynamicmodulusofelasticityofPCCishigherthanthatofGPCpaver

blocksovertheentiretestperiod.Therelativedynamicmodulusofelasticitydecreasedprogressivelyintheﬁrsttwomonths

ofexposureforbothtypesofconcretes.However,testresultsrevealthataftertwomonths,thedynamicelasticmodulusof

GPCpaverblocksdecreasedmuchfasterthanthatofPCC.

Yaweietal.[76]establishedadamagemechanismmodelbyusingrelativedynamicelasticmodulusandproposedthata

powerfunctionmodelismoreprecisethananexponentialfunctionmodel.Thesamemodelswereusedtocreateadynamic

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Yaweietal.[76]assumedthatE0istheinitialdynamicmodulusofelasticityofsamplesandEnisthedynamicmodulusof

elasticityafterNnumberoffreeze-thawcycles.Inourstudy,Nwasconsideredasexposureperiod(N=1forevery30days)

since the temperaturevariation was not controllable in real environmental conditions. According to theexponential

function,relativedynamicelasticmodulusattenuationcanbecreatedas:

Y=En/E0=aebN (3)

En=E0aebN (4)

(20)

Thepowermodelalsocanbeusedtocreatearelativedynamicelasticitymodulusmodel:

Y=Ei/E0=aNb (5)

Where,

Y=Relativedynamicelasticitymodulusofsamples,percentage

EnandEi=DynamicelasticitymodulusofsamplesafterNtimesfreeze-thawcycles,percentage

E0=Dynamicelasticitymodulusofsamplesbeforeexposingtofreeze-thawcycles,percentage

Fig.16.RelativedynamicmodulusofelasticityofUPVvs.RFT.

Table8

RelativedynamicelasticmodulusofGPCandPCCover240daysofexposure.

Exposed(Days) GPC PCC

Relativedynamicelasticmodulus(%) Relativedynamicelasticmodulus(%)

1 100 100 30 98.04 99.04 60 94.83 97.93 90 94.28 96.5 120 91.20 96.18 150 88.70 95.54 180 88.56 95.38 210 88.14 95.23 240 85.49 95.23

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aandb=Constantvariables

TheEqs.(4)and(5)weremodeledinOriginsoftwaretoestablishadamagemodelforbothtypesofconcreteusedinthis

studyandareplottedinFig.17(a)and(b)respectively.Thevaluesfromthemodelsareplottedalongsidemeasured_ﬁelddata

(showninTable8).

According tothepower function,the coefﬁcients a and b for GPC were122.41 and -0.06respectively. While, the

coef_ﬁcientsaandbforPCCwere106.11and-0.02respectively.Italsocanbeobservedfrom_ﬁguresthatAdj.R2_of_power

functionofbothGPCandPCCissuperiorcomparedtotheexponentialfunction.Hence,thisfunctioncanbeusedtocorrelate

ﬁeldexposuretodamageofGPCandPCCasithasfewererrors.Itshould,however,benotedthatthisproposedmodelisvalid

forthesomewhatmildwinterconditionsrecordedinVictoria,Canada.Hence,cautionshouldbeexercisedbeforeusingthis

modeltopaverblocksinmoresevereweatherconditions.

8.Conclusions

Theobjectivesofthisstudyweretoinvestigatetheeffectofrealenvironmentalexposureonleach-abilityandchangein

mechanicalpropertiesofK-basedGPC.Thiswasfurthercomparedtotraditionalconcrete(PCC).Numerousconclusionscan

bedrawnfromthepresentstudy:

SteamcuringanddrycuringmethodsincreasethecompressivestrengthofGPCbyabout3.5and2.3timesrespectively

whenthetemperatureincreasesfromambienttemperature(_̴10_C)_to₈₀_C._The_compressive_strength_of_steam-cured_GPC

washigherdue tothepreventionofexcessive moistureevaporation,anddue totheidenticalinternalcuringofGPC

samples.

AccordingtotheresultsofcompressiontestonrectangularandcylindricalGPCsamples,rectangularsteam-curedGPC

samplesshowedanaveragecompressivestrengthlower(about10.28%)thanthecylindricalsteam-curedGPCsamples

probablybecauseofthehigherrate ofstressconcentrationatcornersofrectangular steam-curedGPCsamples.The

averagestrengthconversionfactorbetweencylindricalandrectangularGPCsamplesis0.89.

Thelaboratorysimulationofseasonalhumiditywasalsocarriedouttomeasuretheeffectofmoisturelevel(dry,SSD,fully

wet)onmassandUPVofbothGPCandPCC.TheresultsoftheexperimentindicatethatthevelocityandmassofGPCand

PCCsamplesincreasedwhenhumiditylevelwaschangedfromdryconditiontofullywetcondition.Themassandvelocity

ratioofGPCwasabout0.98and0.84respectivelywhenthemoisturelevelwereincreasedfromdrytofullywet.Whereas,

themassandvelocityratioofPCCsampleswas0.97and0.79respectively.

AccordingtotheresultsoftheUPVtest,thedecreaseinvelocityofGPCwasabout11.6%(area1)and12.03%(area2).While,

thevelocityofPCCdecreasedabout8.3%(area1)and5.28%(area2).Moreover,theresultoftheSchmidthammershowed

thattheaveragecompressivestrengthofGPCdecreasedabout2.34%(area1)and19.51%(area2).Whereas,thedecreasein

compressivestrengthofPCCwasabout8.2%(area1)and9.65%(area2).

Theleach-abilityofheavymetals,includingtotalalkalinity,totalhardness,pH,totalchlorine,phosphate,copper,ammonia,

iron,nitrateandnitriteofPCCandGPCpaverblocksweremeasuredeverythirtydays(150daysintotal)ofexposuretoreal

environmentalconditionsusingHACHstrips.TheresultsshowthatthepHofGPCpaverblocksis13.92%higherthanpHof

PCCpaverblocksduetotheuseofKOHintheGPCpaverblockmixture.Theresultsalsoindicatedthatthesteamcuring

methodhelpedGPCtodeveloppastestructureandcausedallthechemicalmetalsofGPCpaverblockstoremainconstant

over150daysofexposure.

Therelativedynamicmodulusofelasticitywascorrelatedtotheﬁeldexposureofpaverblocks.Inthisregard,adamage

mechanismmodelwas derivedforbothPCCandGPCpaverblocksafter240daysofexposuretorealenvironmental

conditionsusingthepowerfunctionalmodelandexponentialfunctionmodel.Thecomparisonbetweenexponentialand

powerfunctionshowedthatpowerfunctionissuperiortoexponentialfunctionduetothehigherachievedvaluesofAdj.R2

forbothGPC(0.96)andPCC(0.92).

9.Challenges

IndevelopingGPC,thechemicalcomponentofprecursorsincludingthechemistryphaseandsizeofparticlesiscriticalin

thereactionprocesswithalkalinesolutions.Highquality-checkingandoptimizationofcoalashesandactivatorsarealways

requiredtomakehigh-qualityGPCasthedifferenttypeofby-productmaterialsareavailableinvariouspowerplants.

Basically,GPCcertainlyisasensitivematerialtotemperatureandhumiditycomparedtoPCC.So,morefacilitiessuchas

steamcuringoven,skillsandexpertisearerequiredtocurefreshpasteineitherrealenvironmentalconditionsoratthe

laboratory.

Despitethe growing marketpull for ‘sustainable’construction materials,sucha technology is not available onan

industry-widelevelandhasrestrictedapplicationsinthemarket.Consequently,therearenorelatedstandardsforGPC

reporteduptodateandbasically,standardsmadeforPCCareusedforperformingtestsonGPC.

ThecuringregimeofGPCisanotherconcerninthecoldregionduetoGPC’ssensitivitytomoistureandtemperature.So,

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DeclarationofCompetingInterest None.

Acknowledgements

TheauthorsappreciativelyacknowledgetheﬁnancialsupportfromCanada-IndiaResearchCentreofExcellence

(IC-IMPACTS)andauthorsarealsothankfultoDr.UrmilDave,ProfessoratNirmaUniversity,forhishelpinthisstudy;Matt

Dalkie,technicalservicesengineerofLafargeCanadaInc.andMikeMcDonald,ﬁeldchemistofNationalSilicatesanafﬁliate

ofPQCorporationCompanyforprovidingmaterialsforthisstudy.AuthorsalsoliketothankPriyankaMorlaforherhelpin

productionofGPCpaverblocks.

References

[1]N.H.A.S.Lim,H.Mohammadhosseini,M.M.Tahir,M.Samadi,A.R.M.Sam,Microstructureandstrengthpropertiesofmortarcontainingwasteceramic nanoparticles,Arab.J.Sci.Eng.43(10)(2018)5305–5313.

[2]H.Mohammadhosseini,N.H.A.S.Lim,M.M.T.R.Alyousef,H.Alabduljabbar,M.Samadi,Enhancedperformanceofgreenmortarcomprisinghighvolume ofceramicwasteinaggressiveenvironments,Constr.Build.Mater.212(2019)607–617.

[3]G.Dimitriou,P.Savva,M.Petrou,Enhancingmechanicalanddurabilitypropertiesofrecycledaggregateconcrete,Constr.Build.Mater.158(2018)228– 235.

[4]H.Mohammadhosseini,A.Abdul,H.E.Abdul,Inﬂuenceofpalmoilfuelashonfreshandmechanicalpropertiesofself-compactingconcrete,Indian Acad.Sci.40(2015)1989–1999.

[5]F.Okoye,Geopolymerbinder:averitablealternativetoPortlandcement,Materialstoday:Proceed.4(4)(2017)5599–5604.

[6]B.Singh,I.G.M.Gupta,S.Bhattacharyya,Geopolymerconcrete:areviewofsomerecentdevelopments,Constr.Build.Mater.85(2015)78–90. [7]H.Hardjasaputra,M.Cornelia,Y.Gunawan,I.Surjaputra,H.Lie,Rachmansyah,G.P.Ng,Studyofmechanicalpropertiesofﬂyash-basedgeopolymer,IOP

Conf.Ser.:Mater.Sci.Eng.615(2019)012009.

[8]L.M.Zerzouri,S.Alehyen,M.E.Alouani,M.Taibi,Theeffectofaggressiveenvironmentsonthepropertiesofalowcalciumﬂyashbasedgeopolymerand theordinaryPortlandcementpastes,Mater.Today.Proc.13(2019)1169–1177.

[9]D.Sd.T.Pereira,F.J.daSilva,A.B.R.Porto,V.S.Candido,A.C.R.daSilva,F.D.C.G.Filho,S.N.Monteiro,Comparativeanalysisbetweenpropertiesand microstructuresofgeopolymericconcreteandportlandconcrete,J.Mater.Res.Technol.7(2018)606–611.

[10]F.Nabeel,M.NeazSheik,M.N.S.Hadi,Investigationofengineeringpropertiesofnormalandhighstrengthﬂyashbasedgeopolymerandalkali-activated slagconcretecomparedtoordinaryPortlandcementconcrete,Constr.Build.Mater.196(2019)26–42.

[11]Y.Abualrous,CharacterizationofIndianandCanadianFlyAshforUseinConcrete,DepartmentofCivilEngineering,UniversityofToronto,Toronto, Canada,2017.

[12]J.G.Speight,Chemicalsintheenvironment,ReactionMechanismsinEnvironmentalEngineering,Butterworth-Heinemann,2018,pp.43–79. [13]J. Thaarrini,V.Ramasamy,FeasibilitystudiesoncompressivestrengthofGroundcoalashgeopolymermortar,PeriodicaPolytechnica (Civil

Engineering)59(2015)373–379.

[14]Eu.Haq,S.K.Padmanabhan,A.Licciulli,Synthesisandcharacteristicsofﬂyashandbottomashbasedgeopolymers–acomparativestudy,CeramicInt. 40(2)(2014)2965–2971.

[15]F.Okoye,J.Durgaprasad,N.Singh,Flyash/Kaolinbasedgeopolymergreenconcretesandtheirmechanicalproperties,DataBrief5(2015)739–744. [16]P.Chindaprasirt,C.Jaturapitakkul,W.Chalee,U.Rattanasak,Comparativestudyonthecharacteristicsofﬂyashandbottomashgeopolymers,Waste

Manage.(Oxford)29(2)(2009)539–543.

[17]R.M.Hamidi,Z.Man,K.A.Azizli,ConcentrationofNaOHandtheeffectonthepropertiesofﬂyashbasedgeopolymer,ProcediaEng. 148(2016)189–193. [18]F.Puertas,B.González-Fonteboa,I.González-Taboada,M.M.Alonso,M.Torres-Carrasco,G.Rojo,F.Martínez-Abella,Alkali-activatedslagconcrete:

freshandhardenedbehaviour,Cem.Concr.Compos.85(2018)22–31.

[19]K.Sakkas,D. Panias,P.P.Nomikos,A.I. Soﬁano,Potassiumbased geopolymerforpassiveﬁreprotectionof concretetunnelslinings, Tunnel. UndergroundSpaceTechnol.43(2014)148–156.

[20]A.Hosan,SharanyHaque,F.Shaikh,ComparativeStudyofSodiumandPotassiumBasedFly-AshGeopolymeratElevatedTemperatureAustralia,(2015) .

[21]D.Sabitha,J.K.Dattatreya,N.Sakthivel,M.Bhuvaneshwari,S.A.J.Sathik,Reactivity,workabilityandstrengthofpotassiumversussodium-activated highvolumeﬂyash-basedgeopolymers,Curr.Sci.103(2012)1320–1327.

[22]T.Bakharev,GeopolymericmaterialspreparedusingclassFﬂyashandelevatedtemperaturecuring,CementConcrete35(6)(2005)1224–1232. [23]R.Siddique,UtilizationofindustrialBy-productsinconcrete,ProcediaEng.95(2014)335–347.

[24]T.Xie,T.Ozbakkaloglu,Behavioroflow-calciumﬂyandbottomash-basedgeopolymerconcretecuredatambienttemperature,Ceram.Int.41(2015) 5945–5958.

[25]Y.P.Khandol,D.U.Dave,DevelopmentofFly-AshandBottom-AshBasedAlkaliActivatedPaverBlocks,Departmentofcivilengineering,instituteof technology,NirmaUniversity,Ahmedabad,2016382481.

[26]S.R.Hillier,C.M.Sangha,B.A.Plunkett,P.J.Walden,Long-termleachingoftoxictracemetalsfromPortlandcementconcrete,Cem.Concr.Res.29(1999) 515–521.

[27]H.Lu,F.Wei,J.Tang,J.P.Giesy,Leachingofmetalsfromcementundersimulatedenvironmentalconditions,J.Environ.Manage.169(2016)319–327. [28]A.P.Galvín,F.Agrela,J.Ayuso,M.G. Beltrán,A.Barbudo,Leachingassessmentofconcrete madeofrecycled coarseaggregate:physical and

environmentalcharacterisationofaggregatesandhardenedconcrete,WasteManage.34(2014)1693–1704.

[29]M.Izquierdo,X.Querol,J.Davidovits,D.Antenucci,H.Nugteren,C.Fernández-Pereira,Coalﬂyash-slag-basedgeopolymers:microstructureandmetal leaching,J.Hazard.Mater.166(2009)561–566.

[30]A.S.T.M.C618/C618M,StandardSpeciﬁcationforCoalFlyAshandRaworCalcinedNaturalPozzolanforUseinConcrete,AmericanSocietyforTesting andMaterials,USA,2017.

[31]S.Pilehvar,V.D.Cao,A.M.Szczotok,M.Carmona,L.Valentini,M.Lanzón,R.Pamies,A.-L.Kjøniksen,Physicalandmechanicalpropertiesofﬂyashand slaggeopolymerconcretecontainingdifferenttypesofmicro-encapsulatedphasechangematerials,Constr.Build.Mater.173(2018)28–39. [32]R.Zhao,Y.Yuan,Z.Cheng,T.Wen,J.Li,F.Li,Z.J.Ma,Freeze-thawresistanceofclassFﬂyash-basedgeopolymerconcrete,Constr.Build.Mater.222(2019)

474–483.

[33]Z.Yang,R.Mocadlo,M.Zhao,R.DJr,M.Tao,J.Liang,PreparationofageopolymerfromredmudslurryandclassFﬂyashanditsbehavioratelevated temperatures,Constr.Build.Mater.221(2019)308–317.

[34]F.-Y.Chang,M.-Y.Wey,Comparisonofthecharacteristicsofbottomandﬂyashesgeneratedfromvariousincinerationprocesses,J.Hazard.Mater.138 (2006)594–603.

(23)

[35]X.Goa,B.Yuan,Q.Yu,H.Brouwers,Characterizationandapplicationofmunicipalsolidwasteincineration(MSWI)bottomashandwastegranite powderinalkaliactivatedslag,J.CleanerProd.164(2017)410–419.

[36]R.Gupta,H.M.Rathod,CurrentstateofK-basedgeopolymercementscuredatambienttemperature,Emerg.Mater.Res.4(1)(2015)125–129. [37]C.Yang,R.Gupta,Predictionofthecompressivestrengthfromresonantfrequencyforlow-calciumﬂyash-basedgeopolymerconcrete,J.Mater.Civ.

Eng.(2018)Vols.DOI:10.1061/(ASCE)MT.1943-5533.0002228.

[38]F.Belforti,P.Azarsa,R.Gupta,U.Dave,EffectofFreeze-ThawonK-BasedGeopolymerConcreteandPortlandCementConcreteIndia,(2017). [39]IS15658,PrecastConcreteBlocksforPaving-Speciﬁcation,IndianStandard,India,2006.

[40]N.Ranjbar,C.Künzel,Cenospheres:areview,"areview,FuelJ.207(2017)1–12.

[41]F.Goodarzi,H.Sanei,Plerosphereanditsroleinreductionofemittedfineflyashparticlesfrompulverized,coal-firedpowerplants,FuelJ.88(2009) 382–386.

[42]R.Hooton,Bridgingthegapbetweenresearchandstandards,Cem.Concr.Res.38(2007)247–258.

[43]M.K.Wari,Bajpai,S.Dewangan,U.K,Flyashutilization:abriefreviewinIndiancontext,Int.Res.J.Eng.Technol.(IRJET)03(04)(2016)949–956. [44]J.Davidovits,GeopolymerChemistryandApplication,4ed.,InstitutGeopolymere,France,2015.

[45]P.Azarsa,R.Gupta,Novelapproachtomicroscopiccharacterizationofcryoformationinairvoidsofconcrete,Micron122(2019)21–27,doi:http://dx. doi.org/10.1016/j.micron.2019.04.004.

[46]ASTMC33/C33M,StandardSpeciﬁcationforConcreteAggregates,AmericanSocietyforTestingandMaterials,USA,2015.

[47]ASTMC192/C192M,StandardPracticeforMakingandCuringConcreteTestSpecimensintheLaboratory,AmericanSocietyforTestingandMaterials, USA,2015.

[48]N.Zabihi,Ö.Eren,Compressivestrengthconversionfactorsofconcreteasaffectedbyspecimenshapeandsize,"researchjournalofappliedsciences, Eng.Technol.7(2014)4251–4257.

[49]E.Ferretti,Shape-effectintheeffectivelawsofPlainandrubberizedconcrete,CMC-Tech.Sci.Press30(2012)237–284. [50]EN206,Concrete—Speciﬁcation,Performance,ProductionandConformity,BritishStandard,UK,2014.

[51]ASTMC39/C39M,StandardTestMethodforCompressiveStrengthofCylindricalConcreteSpecimens,AmericanSocietyforTestingandMaterials,USA, 2015.

[52]ASTMC805/805M,StandardTestMethodforReboundNumberofHardenedConcrete,AmericanSocietyforTestingandMaterials,USA,2013. [53]ASTMC597/C597M,StandardTestMethodforPulseVelocitythroughConcrete,AmericanSocietyforTestingandMaterials,USA,2016.

[54]S.A.Omer,R.Demirboga,W.H.Khushefati,RelationshipbetweencompressivestrengthandUPVofGGBFSbasedgeopolymermortarsexposedto elevatedtemperatures,Constr.Build.Mater.94(2015)189–195.

[55]AccuaWeather, AccuaWeather[Online]. Available:,(2017) . https://www.accuweather.com/en/ca/victoria/v8r/augustweather/47163?monyr=8/1/ 2018&view=table.

[56]ASTMC215/C215M,StandardTestMethodforFundamentalTransverse,Longitudinal,andTorsionalResonantFrequenciesofConcrete,American SocietyforTestingandMaterials,USA,2016.

[57]J.Z.Xu,Y.L.Zhou,Q.Chang,H.Q.Qu,Studyonthefactorsofaffectingtheimmobilizationofheavymetalsinﬂyash-basedgeopolymers,Mater.Lett.60 (2006)820–822.

[58]USEPA,UnitedStatesEnvironmentalProtectionAgency(US-EPA)Standard1311,USEPA,USA,2016.

[59]G.S.Ryu,Y.B.Lee,K.T.Koh,Y.S.Chung,Themechanicalpropertiesofﬂyash-basedgeopolymerconcretewithalkalineactivators,Constr.Build.Mater.47 (2013)409–418.

[60]H.Khater,Effectofcalciumongeopolymerizationofaluminosilicatewastes,J.Mater.Civ.Eng.24(2011)pp.902-101.

[61]A.Noushini,A.Castel,Theeffectofheat-curingontransportpropertiesoflow-calciumﬂyash-basedgeopolymerconcrete,Constr.Build.Mater.112 (2016)464–477.

[62]W.K.Part,M.Ramli,C.C.Ban,Anoverviewontheinﬂuenceofvariousfactorsonthepropertiesofgeopolymerconcretederivedfromindustrial by-products,Constr.Build.Mater.77(2015)370–395.

[63]M.Li,H.Hao,Y.Shi,Y.Hao,Specimenshapeandsizeeffectsontheconcretecompressivestrengthunderstaticanddynamictests,Constr.Build.Mater. 161(2018)84–93.

[64]L.T.Ngoc,C.-A.Graubner,UncertaintiesofconcreteparametersinshearcapacitycalculationofRCmemberswithoutshearreinforcement,Beton-und Stahlbetonbau(2018)1–8.

[65]ACI318,BuildingCodeRequirementsforStructuralConcreteandCommentary,AmericanConcreteInstitute,USA,2014. [66]K.Ramujee,M.Potharaju,Permeabilityandabrasionresistanceofgeopolymerconcrete,IndianConcreteJ.88(2014)34–43. [67]P.J.M.Monteiro,P.K.Mehta,ConcreteMicrostructure,4ed.,Properties,andMaterials,USA,2014.

[68]M.Albitar,M.M.Ali,P.Visintin,M.Drechsler,Durabilityevaluationofgeopolymerandconventionalconcretes,Constr.Build.Mater. 136(2017)374–385. [69]S.Levy,Calculationsrelatingtoconcreteandmasonry,ConstructionCalculationsManual,(2012),pp.211–264.

[70]A.Poursaee,Corrosionofsteelinconcretestructures,CorrosionofSteelinConcreteStructures,(2016) pp.139-33.

[71]M.Izquierdo,X.Querol,C.Phillipart,D.Antenucci,M.Towler,TheroleofopenandclosedcuringconditionsonTheleachingpropertiesofﬂy ash-slag-basedgeopolymer,J.Hazard.Mater.176(2010)623–628.

[72]F.Kozisek,HealthRisksfromDrinkingDeminirelizedWater,CentreofEnvironmentalHealth,NationalInstituteofPublicHealth,Prague,Czech Republic,2004.

[73]Y.Zhang,S.Wei,C.Qianli,C.Lin,Synthesisandheavymetalimmobilizationbehaviorsofslagbasedgeopolymer,J.Hazard.Mater.143(2007)206–213. [74]G.Fang,W.K.Ho,W.Tu,M.Zhang,Workabilityandmechanicalpropertiesofalkali-activatedﬂyash-slagconcretecuredatambienttemperature,

Constr.Build.Mater.172(2018)476–487.

[75]IndianStandard1331,Non-DestructiveTestingofConcreteMethodsofTest,IndianStandard,India,2016.

[76]F.Yawei,L.Cai,Y.Wu,Freeze–thawcycletestanddamagemechanicsmodelsofalkali-activatedslagconcrete,Constr.Build.Mater.25(2011)3144– 3148.