A REVIEW BASED ON DEVELOPMENT OF FLY ASH BASED GEOPOLYMER BINDER ACTIVATED IN PRESENCE OF SEWAGE SLU

International Research Journal of Engineering and Technology (IRJET) e-ISSN:2395-0056

Volume: 09 Issue: 08 | Aug 2022 www.irjet.net p-ISSN:2395-0072

A REVIEW BASED ON DEVELOPMENT OF FLY ASH BASED GEOPOLYMER BINDER ACTIVATED IN

PRESENCE OF SEWAGE SLUDGE.

2

1M. Tech student, Department of civil Engineering, Techno India University, Kolkata, India

2Assistant professor, Department of civil Engineering, Techno India University, Kolkata, India ****

Abstract- The outcome of wastes has been increased many folds now a days and its dispositionis a great challenge. Again, one tone cement produces one tone carbon-dioxide. There is scarcity of lime stone also. Perfect utilization of the waste materials in a way to develop alternative of cement binder is very much needed. Though, minimum use of waste materials i.e., slag, fly ash etc. is made in cement manufacturing unit as blender and road construction as filler materials. Again, this waste material may enhance the possibility of ground water contamination problem due to the leaching of toxic and heavy metals, ultimately reaching to underground water reservoir. Recently it is observed that geopolymer can be developed from the waste materials (like fly ash, slag) comprising silica and alumina, in an alkaline environment (usually commercial hydroxide and silicate). This research aims to investigate the effect of incorporation of sewage sludge as an activator in the formation of fly ash based geopolymer. The objective of the present research is to develop fly ash based geopolymer by using sewage sludge (pH>8.0) as primary activator. The use of commercial sodium silicate may be replaced by highly reactive alkaline sludge which is readily available as municipal waste.

Key Words- Geopolymer, fly ash, sewage sludge, sodium silicate

1. INTRODUCTION

Theresultsofwasteshavebeenincreasedmanyfoldsnowadaysanditsdispositionisagreatchallenge.Again,onetone cement produces one tone carbon-dioxide. Perfect use of the waste materials in a way to develop alternative of cement binder is very much needed. Joseph Davidovits introduced geopolymer as an alternative of cement binder which can be made from the alkali activation of source materials comprising silicon and aluminum. Recently it is observed that geopolymer can be developed from the waste materials (like fly ash, slag) comprising silica and alumina, in an alkaline environment(usuallycommercialhydroxideandsilicate).

1.1Background of geopolymer?

Geopolymers have caught the attention of many environmentalists and material scientist replacement for ordinary Portland cement (OPC) to reduce the emissions of greenhouse gases which is the main contributor to global warming (HuntzingerandEatmon,2009)andcanbeusedasanalternativeto cementconcretewhichwill eventuallycauseless health hazard and pollution (Feely et al.,2004) studies of Geo polymer concrete has proven and that it has remarkable advantage over conventional cement concrete in terms of durability and also sustainability (Mehta and Burrows, 2001; CastelandFoster,2015;Ganesanetal.,2014).

1.2Chemistry of geopolymerisation

Geopolymers are related to aluminium silicate structures in which the role of charge balancers is played by alkaline cations.Geopolymershaveamorphousstructure,differentfromzeoliteswhicharecrystalline.Thepozzolanicreactionsof geopolymerisation involving silica and alumina in alkaline solution can be described as following: 1. dissolution at the surface of Al and Si in highly alkaline solution;2. diffusion of the species through the solution; 3. polycondensation of Al and Si complexes with the added silicate solution;4. and formation and hardening of a gel to form the final geopolymer. Geopolymers can be formed by the polymerization of individual silicate and aluminate species that are dissolvedfromtheirsourcesatlowpHinthepresenceofexternalcalciumsources,andthenitisundergoneheatcuring.

1.3Fly Ash

Flyashisthefinelydividedleftoverthatistheoutcomeofthecombustionofpulverizedcoalandistransportedfromthe combustionchamberbyexhaustgases.

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1.3.1Where is fly ash used?

20 million metric tons (22 million tons) of fly ash are being used in a variety of engineering applications in a year. Highway engineering applications include (1). portland cement concrete (PCC), (2) soil, (3) asphalt filler, (4) grouts and roadbasestabilization,(5)flowablefills.

1.3.2Environmental benefits.

Useofflyashespeciallyinconcretehasmadeasignificantenvironmentalbenefitwhichincludes(1)increasingthelifeof concrete roads and structure (2) improvement of the concrete durability (3) reduction in energy use (4) reduction in greenhousegasesandotherharmfulairemissions(5)savingofothernaturalresourcesandmaterials.

1.4Classification of Fly Ashes

TheAmericanSocietyforTestingandMaterials(ASTM)C618has definedtwotypesofflyashes:ClassFandClassC.The maindifferencebetweentheseclassesistheamountof calcium,alumina,silicaandironcontentintheash.Thechemical propertiesofflyasharedeterminedbythechemicalcontentofthecoalburned.

Onthebasisofapplication,itisnotnecessaryforalltheFlyAshestomeettheASTMC618requirements.FlyAshwhichare usedascementreplacementmustmeetstrictconstructionstandards.75% offlyashmusthave finenessof 45 µmorless andthecarboncontentasmeasuredbythelossonignition(LOI)shouldbelessthan4%.IntheUS,LOImustbeunder6%.

1.4.1Class F Fly Ash

WhenhardoldanthraciteandbituminouscoalisburneditproducesClassFflyash.Thisashispozzolanicbynatureandit contains7%lime(CaO)itpossessespozzolanicpropertiestheglassysilicaandalumina

Class F fly ash requires a cementing agent like quicklime, Portland cement which is mixed with water to react and form cementitiouscompounds.Onaddingchemicalactivatorsuchassodiumsilicate(Waterglass)toClassFflyashitcanforma geopolymer.

1.4.2Class C Fly Ash

OnburningofyoungerligniteorsubbituminouscoaltheFlyashwhichisproducedisknownasClassCFlyAsh. Ithasselfcementingpropertiesaswellaspozzolanicproperties.InthepresenceofwaterClassCflyashhardensandgetsstronger with time. It does not require any activator because it has self- cementing properties unlike Class F Fly ash and also the contentofsulphateisgenerallyhighinthistypeofflyash.Italsocontainsmorethan20%oflime(CaO).

1.5Sewage Sludge

Sewage sludge is produced as a by-product during sewage treatment of industrial or municipal wastewater. It is the residual, semisolid material. The term "septage" refers to sludge from simple wastewater treatment but is connected to simpleon-sitesanitationsystems,liketheseptictanks.

Approximately50%ofthesuspendedsolidmatterwillsettleoutinanhourandahalfwhen freshsewageorwastewater enters primary settling tank. This process is known as raw sludge or primary solids and is "fresh" before anaerobic processesbecomeactive.

1.6Sodium silicate

Sodiumsilicateisthecommonnameforamixtureofcompounds,mainlythemetasilicate,bettercalled liquid glass, water glass. The product has a huge variety of uses, which includes the formulation of cements, passive fire protection, textile andlumberprocessing,manufactureofrefractoryceramics,asadhesives,andintheproductionofsilicagel.

2.LITERATURE REVIEW

Xu H. et.al. (2000) anticipated that the chemical properties of geopolymer are similar to that of the zeolites. But these particlespossessacompleteamorphouscharacteristic.Asperauthormutualpolymerizationofthespeciesofaluminaand silicate was formed by this process. This product was actually originated by dissolving source material comprising of

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siliconandaluminiumhighvalueofpH.Itonlyoccurredwiththepresenceofalkalisilicatesolvent.Theresearchincludes theinvestigationongeopolymerisationfromfifteennaturalAl-Simineralsinawaytogoverntheconsequenceofmineral characteristicsonthestrengthofdevelopedgeopolymer.Again,theresearchoutputdefinesmaximumdissolutionofalkali solutionforframeworksilicatesincomparetochain,sheetandringstructures.TheauthorsuggestsKOHinsteadofNaOH in maximum cases out of the fifteen minerals. The research appropriately correlates the ion pair mechanism with the mineral dissolution as well as the geopolymerisation. The research on the other hand, exhibited the several source of materialswhichcanbepotentiallyusedinthepurposeofgeo-synthesis.

J G S Jaarsveld. et.al. (2003) suggestedinthisresearchworkthatnoteverywastematerialisdissolvedinalkalisolution. Because of that the author mentioned that original structure of some waste particles remains intact and contribute to eitherquickenortoughenthosedevelopedframeworks.

Author recognized the degree of crystallinity of the geopolymer is the prime influencing parameter for strength perspective.Again,thepresenceofcalciuminflyashanditsroletowardsstrength developmenthas beenfoundout.The extent of particle, calcium contamination, metals in alkaline medium and base material category directly influence initial synthesisandthefinalproduct.

Khale D. et.al. (2007) addressedgeopolymerisationasabroadscopeofresearchforutilizingsolidwasteproducts.Khale D. et.al briefly elaborated various factors which influence the mechanism of geopolymerisation and development of geopolymer. The impact of various parameters like starting materials, alkali activators, super-plasticizers, curing temperature, curing time, Silicate-Hydroxide ratio, alkali concentration, Silicate Aluminium ratio, liquid- solid ratio has been briefly described. Again, the author has focused on few important terms in connection with geopolymerisation like calcination, relative humidity. Immobilization of toxic metal by geopolymer along with micro-structural characterization are worked out in this research. The author depicted geopolymerisation as embryonic tool for the operation of several wastedisposals.

J Temuujin. et.al. (2009) introduced the power driven or mechanical activation of ashand its impact on the features of thegeopolymersdevelopedatambientheatexposure.Essentiallythisprocessinfluencedbygrainsizeandmorphological stand point. The author indicates towards the fact that the harden property of polymeric compound were reduced along with the introduction of free water in the reaction mix. For raw and routinely activated samples, strength under room temperature curing was found 16 (2) MPa and 45 (8) MPa, respectively. This procedure was performed in a typical methodologywheremillingagenttopowderratiowascontrolledas10:1.Thisactivationwasprovedefficienttoimprove the size and shape of the grains in connection with better reactive potentiality without allowing major alteration in mineral arrangement. Around 80% increment was observed for the fly ash activated by this technology rather than ordinary one. The key role to increase the strength of polymeric product was endorsed through this methodology by minimizing the grain size and modifying the morphological extent. There by this methodology directly emphasize the higherrateofsuspensionorreactivitybytuningthesizeofgrainsorparticlesthroughmechanicalprocessofactivation.

Zuhua Z. et.al. (2009) executedaprogramontheroleofwaterasakeyparameterinformationofcalcinedkaolinbased geopolymer. It was observed in X-ray diffraction (XRD) and thermo-gravimetry (TG) that the activity growth of calcined kaolin was decreased by the residual water prior to the formation of stable crystalline phases. Reaction heat evolution capacityshowedthathighliquid/solidratiomayincreasetherateofdissolutionofrawmaterialsandthehydrolysisofSi4 + and Al 3 + compounds. The author suggests that the effect of non-evaporable water is a key parameter in connection withthestrengthvariationofgeopolymers.Inthisstudytheresultspointoutthatnon-evaporablewaterisindispensable tomaintainthestrengthstableandtheoptimumcontentwasabout7.4%.Inkaolincalcination,remainingwaterebbedthe activitygrowthofcalcinedproductbeforetheformationofthestabledcrystallinephases.Thehigherliquidistosolidratio could increase the percentage of dissolution and hydrolysis, if OH − concentration was high enough, but it might hinder polycondensation process. Geopolymers exhibited large shrinkage property while cured in air unlike in a little expanded hydrothermal condition. Finally, to conclude that for the upcoming application of this new material, the environmental condition,suchashumidityandtemperatureshouldbetakenintocount.

Prud’homme. et.al. (2010) statedthatthesynthesisofgeopolymersonthebasisofalkalinepolysialatewasachievedat low temperature (25–80 0 C), by the alkaline activation of raw minerals and silica fume. Dehydroxylated kaolinite and alkaline hydroxide pellets solution (Dissolved in potassium silicate) was used to prepare the materials. After that, the constituentsweretransmittedtoapolyethylenemouldsealedwithatop.Thenthematerialswereemployedtoovenat70 0 C for 24 hours. FTIR-ATR spectroscopy studied that a polycondensation reaction was used in the formation of the amorphoussolidforallgeopolymermaterialsfollowingdissolutionoftherawmaterials.Itwasoccurredsincethethermal

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measurementhavinga0.22Wm−1K−1value.Again, TGA-MSexperimentsconfirmedthattherewasasynthesisationof in situ inorganic foam based on silica fume from the in situ gaseous production of dihydrogen owing to the oxidation of free silicon (content in the silica fume) by water in alkaline medium. For the applications in building materials, this substancehadpotentialityasaninsulatingmaterial.

Abdul Aleem (2012) Geopolymer has high early strength so it can be used in precast industries so that huge productioncanbemadeinshortdurationoftimeandbreakageduringtransportationcanalsobeminimized.Geopolymer canalsobeusedininfrastructureworks.Moreover,flyashcanbeusedeffectivelysonolandfillsarerequiredtodumpFly Ashes.

Joseph Davidovits (2013) StatedinhisresearchthattheexistingPortlandcementstandardsarenotusedtogeopolymer cements. Presence of standard geopolymer cements is required. Although all experts have produced their own recipe depending upon the local raw materials (wastes, by products or extracted). There is a necessity to select a Standard geopolymercementcategory.

Accordingto2012StateofGeopolymersuggestedtoselecttwocategories

o Type2flyashbasedgeopolymercement:flyashesareavailableinmajoremergingcountries.

o Ferrosialatebasedgeopolymercement:thisisrichinironandispresentallaroundtheglobe

o Theappropriateuser-friendlyGeopolymericreagent.

Kefiyalew Zerfu and Januarti Jaya Ekaputri (2019). stated that fly ash based geopolymer had been used in high strength concrete applications in dame tunnel and high-rise buildings. Fly Ash based concrete can also be used in constructionofairportpavements.Highloadpressureduetohightirepressureduringsummerdeformthesurfaceofthe pavement.Sincegeopolymerhasgothightensileandcompressivestrengthitwillavoidsuchdamagestooccur.Therefore, geopolymer is suggested to use for airport pavement construction because of its high strength to resist static load from aircraft.Geopolymerisalsoagoodchoiceforstorageofradioactiveandtoxicwastes.

3. CONCLUSION

The function of sodium silicate is to initiate the polymerization basically at an early stage of reaction. The degree of aluminosilicate polymerization depends on the presence of silicate solution as the source of reactive silica [E Obonyo et al.,2011]. As metal hydroxide interacts with the reactive solid material in presence of silicate solution, its states the generationofsilicateandaluminatemonomersinthemixture.

The major drawback is that this silicate solution consists more than 65% of water which is responsible for porous character and semi crystalline phases in geopolymer. Earlier research [C. Kuenzel et al.,2012] accused the excessive structural water; asthe primecause of dryingshrinkagein withagingandsuccessivegeneration ofcrack with time. The scopeofusingalkalinesludgeasanalternativeofsodiumsilicatemaybeinvestigated.

The objective of the present research is to develop fly ash based geopolymer by using sewage sludge. The use of commercialsodiumsilicatemaybereplacedbyhighlyreactivealkalinesludgewhichisreadilyavailable.Theexperimental investigation is aimed to develop a new trend of economic fly ash based geopolymer with the betterment in micro and macrolevel.

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