STUDY ON PROPERTIES OF MULTILAYERED GEOPOLYMER CONCRETE ELEMENTS by IRJET Journal

STUDY ON PROPERTIES OF MULTILAYERED GEOPOLYMER CONCRETE ELEMENTS

Manjunath N K1, N. Jayaramappa2, Abbu Hashim Ali3

1 Research Scholar, Department of Civil Engineering, University of Visvesvaraya College of Engineering (UVCE), Bengaluru, Karnataka, India

2 Professor, Department of Civil Engineering, University of Visvesvaraya College of Engineering (UVCE), Bengaluru, Karnataka, India.

3 PG Student, Department of Civil Engineering, University of Visvesvaraya College of Engineering (UVCE), Bengaluru, Karnataka, India.

Abstract - Recentadvancementsinsustainableconstruction havespurredconsiderableinterestingeopolymerconcreteas an eco‐friendly and robust alternative to traditional cement‐based materials. In this study, the performance of geopolymer concrete is examined by using three distinct strength grades low, normal, and high that maintain properties similar to conventional grades while being optimizedforenvironmentalperformance.Tofurtheroptimize performance, structural elements are divided into zones corresponding to the distribution of mechanical stresses. Specifically, tensile stresses at the bottom of a structural element are mitigated by employing appropriate reinforcement along with moderate‐strength concrete, whereascompressiveforcesatthetopareeffectivelymanaged by high‐strength concrete. The research involves three concrete grades: low strength conventional concrete (LSC) designated as M10, normal strength geopolymer concrete (NSGC) designated as 6 M, and high strength geopolymer concrete(HSGC)designatedas14M.Boththecompressiveand flexural strengths of NSGC, LSC, and HSGC have been investigated individually and in various composite configurations. These configurations include a scenario with one-thirdNSGCpositionedatthebottomandtwo-thirdsHSGC placed at the top, the reverse layout, as well as a layered arrangementconsistingofone-thirdHSGCfromthetop,onethird NSGC from the bottom of the soffit, and the remaining one-third LSC at the center. The experimental outcomes support a phased casting approach, demonstrating that integrating multiple geopolymer grades within a single structuralelementsignificantlyenhances materialefficiency and overall performance while offering a promising path towardmoresustainableconstructionsolutions.

Key Words: Geopolymer concrete, Sustainable materials, Layeredconcrete

1.INTRODUCTION

The shift toward environmentally responsible and performance-drivenconstructionhasbroughtgeopolymer concrete to the forefront as a viable and innovative alternativetotraditionalcement-basedsystems.Oneofthe

intriguing and challenging developments in green construction over recent decades is the advent of geopolymer concrete, which initially transitioned from laboratory research to practical application. In today's constructioneradrivenbyeconomicdemandsandtheneed for superior performance, the adoption of layered geopolymertechniqueshasevolved.Consequently,instead ofusingauniformgeopolymermixforanentirestructural element, employing a layered approach offers strategic advantagesbyoptimizingmaterialuse,enhancingstructural performance, and reducing both costs and environmental impact.Dattatreyaetal.,[1]analyzedtheflexuralbehaviorof reinforced geopolymer concrete beams under two-point loading. The study found that beams achieved ultimate momentsupto28.6 kNm,withfailuregovernedbyyielding of tensile reinforcement followed by crushing of the compressive zone, showing comparable ductility to OPCbasedbeams.AleemandArumairaj.,[2]presentedareview detailingthefundamentalproperties,chemicalmechanisms, andenvironmentaladvantagesofgeopolymerconcrete.The studysummarizedtheinfluenceofprecursortypes,curing temperatures, and alkaline activator combinations, concludingthatflyash-basedgeopolymerscouldreduceCO₂ emissions by up to 80% compared to Portland cement. Kumar et al.,[3] investigated fly ash-based geopolymer concretebyvaryingNaOHmolarity(6 Mto14 M)andfound optimum compressive strength at 12 M. Cylindrical specimens tested after oven curing at 100°C for 24 hours showed maximum strength of 33.6 MPa, with strength increasing as curing temperature and activator concentration increased. Using load-deflection testing, Abraham et al.,[4] evaluated geopolymer concrete beams reinforcedwithsteelbarsunderflexuralloading.Thestudy demonstrated that beams with fly ash and GGBS blends exhibitedenhancedstrengthandductility,reachingultimate loads up to 70 kN with narrower cracks and reduced deflections compared to control specimens. Sanni and Khadiranaikar[5]investigatedtheeffectofNaOHmolarity (8 M to 16 M) and alkaline liquid to binder ratio on compressivestrengthacrossdifferentgradesofgeopolymer concrete. At 12 M and a 0.35 ratio, compressive strength peakedat65.4 MPa,confirmingthesensitivityofgeopolymer

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performancetoactivatorchemistry.Unetal.,[6]developeda numericaldeflectionmodelforgeopolymerconcretebeams, validated by long-term deflection data collected over 180 days. Using sustained load testing and finite element simulations,theyfoundthat deflections reached5 mm for simplysupportedbeams,closelymatchingpredictedvalues basedonelasticmodulusandshrinkageparameters.Ranjbar et al.,[7] assessed fracture behavior of layered precast geopolymer beams using acoustic emission monitoring during three-point bending. The analysis showed that the multilayer configuration delayed crack propagation, with energyabsorptionincreasingby25–30%inlayeredbeams compared to monolithic specimens, suggesting improved damagetolerance.Singh[8]investigatedthemicrostructural andbindingbehaviorofflyash-basedgeopolymerbinders. UsingSEMandXRDtechniques,thestudyidentifieddense aluminosilicategel networksandreducedcalciumphases, contributing to compressive strengths exceeding 40 MPa. The paper emphasized its potential for replacing conventionalcementinstructuralapplications.Saranyaet al.,[9]testedreinforcedgeopolymerconcretebeamsunder monotonicloadingtofailure.Thespecimensreached peak loads of 62.5 kN, with mid-span deflections of 20.3 mm. Crackpatternswerepredominantlyflexural,andthebeams exhibited stable load-carrying capacity and high postcracking ductility under single-cycle loading. Akduman et al.,[10] used recycled brick and concrete aggregates to produce geopolymer concrete beams and evaluated structural behavior under two-point bending. The beams showeda15–20%reductioninloadcapacitycomparedto conventionalaggregatemixes,butwithacceptablestiffness andtoughness,indicatingsuitabilityforsecondarystructural members. Amran et al.,[11] reviewed over 100 studies focusingonthelong-termdurabilityofgeopolymerconcrete in aggressive environments. Their synthesis reported reducedchloridepermeability(aslowas300 Coulombsin RCPT),excellentsulfateresistance,andminimalcarbonation depth, highlighting geopolymer’s resilience compared to OPC-basedsystems.AhmadJanetal.,[12]compiledareview examininghowsilica-to-aluminaratio,alkalinesolution-tobinder ratio, calcium oxide and ferric oxide presence, and molar concentrations of sodium hydroxide and sodium silicate affect compressive strength. Reported results indicatedthataSi/Alratioof2.5andNa₂SiO₃/NaOHratioof 2.0yieldedcompressivestrengthsexceeding40MPa. This documentistemplate.

2. MATERIALS

2.1 Cement

The study utilized ordinary Portland cement, specifically grade 43 Zuari cement which is widely available in the local market. To maintain experimental consistency, the samebatchofcementwasusedforeverytest.Thecement’s properties were carefully evaluated against various parameters outlined in IS 4031-1988, confirming that it

complieswiththeIS12269-1987standard.Table1outlines thedetailedphysicalcharacteristicsofthecement.

Table -1: PhysicalQualitiesofCement

ofCement 3.5%

2.2 Fine Aggregate

Locally sourced M-sand, which adheres to the Zone II requirements as per IS 383-1970, was utilized. Detailed informationonthephysicalpropertiesofthisfineaggregate isprovidedinTable2.Notably,theM-sandusedhasparticle sizessmallerthan4.75mm.

Table -2: CharacteristicsofFineAggregate

2.3 Coarse Aggregate

Coarseaggregate,withmaximumsizesof20mmand12.5 mm,wasemployed.InlinewiththestandardsIS383-1970 andIS2386-1983,anexperimentalinvestigationwascarried out to assess the properties of the coarse aggregates. The findingsaredetailedinTable3.

Table -3: CharacteristicsofCoarseAggregate(20mm)

2.4 GGBS

Ground Granulated Blast Furnace Slag (GGBFS) is incorporated into geopolymer concrete to supply a rich sourceofcalciumandsilicatecompounds,whicharecritical forthegeopolymerreaction.Itsinclusionleadstoadenser microstructurethatsignificantlyimprovesthemechanical properties,especiallycompressivestrengthandlong-term durability.TheGGBSusedinthisstudywassourcedlocally

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inBangaloreandexhibitsspecificgravityofapproximately 2.89.

2.5 Fly Ash

Flyash,generatedasabyproductfromcoalcombustionin thermal power plants, serves as a highly reactive aluminosilicatesourceessentialforgeopolymerization.Its fine, spherical particles refine the mix by enhancing workability,reducingpermeability,andultimatelyboosting thedurabilityandstrengthofthegeopolymerconcrete.The FlyashusedinthisstudywassourcedlocallyinBangalore.

2.6 Sodium Hydroxide (NaOH)

Sodium hydroxide functions as the primary alkaline activator,dissolvingthealuminosilicatesourcematerialsto release reactive species. This dissolution initiates the geopolymerization process, ultimately contributing to the concrete's structural integrity and mechanical strength. Naohwassourcedlocallyintheformofpellets.

2.7 Sodium Silicate (Na2SiO3)

Sodiumsilicateprovidesanadditionalsourceofsilicathat supports the formation of a robust gel network. This enhanced silica content improves the matrix density and overalldurabilityofthegeopolymerconcrete.Na2SiO3inthe formofgelwasutilizedinthisstudy.

2.8 Water

FreshtapwaterconformingtoIS:456-2000standardswas usedforthecastingofgeopolymerconcreteelementsinthe laboratory.Beforethemixingprocess,thenecessaryvolume ofwaterwascarefullymeasuredwithagraduatedjarand wasthencombinedwiththedryingredients.

3. MIX DESIGN

IS10262-2019,IS456-2000andliteraturewereconsulted inordertocreatedifferentgradesofgeopolymerconcrete. Tables4,5&6illustratestheDesignmixratioforM10,6 M&14Mrespectively.

Table -4: M10GradeDesignMixRatio

Sl No Material Quantity(kg/m3)

1 Cement 241

2 FineAggregate 467

3 Coarseaggregate 1511

Table -5: NormalStrengthGPCDesignMixRatio

Design Mix Ratio:1:195:630&W/cis063 SlNo

Design Mix Ratio:1:1.17:2.83.NaOH:6M,Alkaline/Binder ratio:0.4

Table -6: HighStrengthGPCDesignMixRatio

3 CoarseAggregate 1291

Design Mix Ratio: 1:1.04:2.52. NaOH: 14M, Alkaline/Binderratio:0.3 Sl No Mixes

Notations given for different combinations of Layered geopolymer concrete elements which were casted are as follows,inTable7.

Table -7: MixDetails

6Molar geopolymerconcrete

2 14Molargeopolymerconcrete HSGC 3 14M2/3rdfromtopand6M 1/3rdfromsoffit. HSGC-NSGC

6 M 2/3rd from top and 14 M 1/3rdfromsoffit. NSGC-HSGC 5 6M1/3rdfromtop,Middle1/3rd M10andlast1/3rd14M NSGC-LSC-HSGC 6 14M1/3rdfromtop,Middle1/3rd M10&last1/3rdportion6M

4. DISCUSSIONS OF TEST RESULTS

4.1 Compressive Strength

HSGC-LSC-NSGC

Cubespecimensmeasuring0.15×0.15×0.15meterswere castandtestedusingacompressiontestingmachine(CTM) aftercuringperiodsof7,14,28,and56days,corresponding tovariousconcretemixratios.Foreachcuringageandmix,

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theaveragestrengthwascalculatedfromthreesamples.The summarizedresultsforeachsetarepresentedinTable8.

Table -8: ResultsofCompresssiveStrengthTest

Compressivestrength(MPa)

ConcreteMix

7Days 14 Days 28 Days 56 Days

The above results highlight the variation in compressive strengths across different concrete grades used in all mix proportions. In multi-layered concrete combinations incorporatinggradessuchasM10,6MGPC,and14M GPC, this variance becomes particularly evident. M10 typically achieves strengths in the range of 10–15 MPa, normal strength falls between 20–40 MPa, while high strength consistentlyexhibitscompressivestrengthsof60–75MPaor higher.ThesedistinctionsmakeM10moreappropriatefor non-structuralelements,whereasthelatterarebettersuited forprogressivelymoredemandingstructuralapplications.

4.2 Flexural Strength

Flexural strength was assessed at 28 and 56 days using concrete prisms measuring 10 × 10 × 50 cm. The testing followedatwo-pointloadingmethod,wherethefailureload was recorded to calculate the flexural strength. The outcomesofthesetestsareillustratedinFigure2.

flexuralstrength,reflectingenhancedstructuralbehavior.In contrast, low-strength conventional concrete (LSC) layers exhibit comparatively lower values due to their inherent materiallimitations.Normal-strengthgeopolymerconcrete (NSGC), meanwhile, offers a middle ground balancing mechanicalstrengthwithfavorableworkability makingit suitable for transitional zones in composite concrete elements.

5. CONCLUSIONS

Thisstudyhighlightsastrategicandwell-integrateduseof geopolymerconcretebycombiningvariousstrengthgrades (M10 low strength conventional concrete, 6 M medium strength geopolymer concrete, and 14 M, high-strength geopolymerconcrete)withinasinglestructuralframework. This layered design not only ensures optimized strength distribution but also promotes cost efficiency, structural adaptability, and adherence to safety and sustainability standards.ByassigningM10tonon-critical zones,normal strengthGPCtointermediateareas,and14MGPCtohighstressregions,theapproachefficientlytailorsmaterialusage to actual performance demands. Crucially, leveraging geopolymer concrete in place of traditional cement-based mixes significantly reduces environmental impact by utilizingindustrialbyproductslikeflyashandGGBFS.The inclusion of geopolymer-based 6 M and 14 M enhances durability, thermal stability, andlong-term strength while supportingcarbonfootprintreduction.Additionally,phased casting techniques using multiple geopolymer grades streamline construction, reduce labor and material waste, andincreaseoverallexecutionefficiency.

ACKNOWLEDGEMENT

ThepresentstudywasconductedatBangaloreUniversity, UVCE,Bangalore,Karnataka-560056.

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Fig -1: FlexuralstrengthComparison

The flexural strength test results for different mix combinationsat28and56daysrevealdistinctperformance trends across the layered concretes. High-strength geopolymerconcrete(HSGC)layersdemonstratethehighest

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