PERFORMANCE OF LIGHT WEIGHT AGGREGATE CONCRETE- A REVIEW
Abstract - The main constituents of concrete are cement, aggregates, and water. The need for concrete increases as infrastructure expands. A rise in demand for concrete's constituents has resulted from the continued expansion of its use. One of the most mined materials in the world is coarse aggregate. Total demand has reached an all-time high due to rising building and urbanisation. This necessitates a global increase in the number of quarries. This illness is highly detrimental to the environment. Moreover, it has expedited the depletion of our natural resources. In an effort to decrease environmental damage and the depletion of natural resources, researchers are investigating viable substitutes for regularly used combinations. Environmental conservation, including waste reduction and the judicious use of natural resources, was a top focus for construction and building materials. By blending different types of waste, new materials, such as eco-concrete, specialty concrete, etc., have beenproduced. In nontraditional concretes, fly ash, crushed granulated blast furnaceslag,silicafume,building demolition debris,plastics, and glass were utilised in place of cement or aggregates. Furthermore, wastes can be utilised to generate lightweight concretes. In this article, a variety of studies conducted by researchers to develop lightweight concrete by employing a varietyof feasiblelightweightaggregatesareaddressed.
Key Words: light weight concrete, fly ash, eco concrete, industrialwastematerials
1.INTRODUCTION
Concreteisamongthemostextensivelyemployedbuilding materials in the world. The qualities of concrete are altering as a result of technical advancements, material substitution,andthedevelopmentofthebuildingindustry. The world of concrete technology has progressed greatly toaccommodatespecialcriteria.Thetraditionalmethodof manufacturing standard concrete consisted of only four components:cement, water, coarseandfine aggregates.A significant and adaptable material, structural lightweight aggregate concrete is expected to take centre stage in the new millennium owing to its numerous technological, financial, and environmental advantages. It is used in a broad variety of structures, including as multi-story building frames and floors, curtain walls, shell roofs, folding plates, bridges, and various prestressed and precastparts.Becauseearthquakeforceswillbeproportional
to the mass of civil engineering structures and buildings, structural lightweight aggregate concrete is frequently utilised to minimise a structure's dead weight as well as the danger of earthquake damage to a structure. In order todiminishthelikelihoodofanearthquake'sacceleration, astructureorbuildingmust minimizeitsmass.Moreover, lowering the dead weight of a building may cause the cross-sectionofitsfoundation,beams,plates,andcolumns to be smaller. A greater strength/weight ratio, stronger tensile strain capacity, a lower coefficient of thermal expansion,andgoodheatandsoundisolationqualitiesare all benefits of structural lightweight aggregate concrete becauseoftheairgapsinthelightweightaggregates.
1.1 Light weight concrete (LWC)
Aformofconcreteknownas"lightweightconcrete"isone that contains an expanding agent, which increases the mixture's volume while enhancing its strength and reducing its dead weight. The development of Light Weight Concrete (LWC) in concrete technology is quite recent. It is not a novel building material, but it was created in Sweden in the 1920s as a result of the expandingneedfortimbersupply.Formorethan70years in Europe, 40 years in the Middle East, and around 20 years in South America and Australia, the LWC has been employed in a range of commercial, industrial, and residential applications. Manufacturing claims that LWC currently makes up more than 40% of all building in the UK and more than 60% in Germany. It is lighter than standardconcreteandhasadrydensityrangingfrom300 kg/m3to1850kg/m3
LWC is often created either by adding chemicals that create air voids in the cured concrete or by utilising natural or synthetic lightweight aggregates [Cheng et al., 2012]. However, in the past, natural or man-made aggregates were used to make lightweight concrete for structuralapplications [Felicetti et al., 2013; Yang et al., 2012]
The construction industry tends to favor lightweight concrete (LWC) over normal weight concrete (NWC) because of LWC'smany benefits, suchasNWC'srelatively higher thermal conductivity and LWC's lower costs in these areas: transportation costs, lifting equipment costs,
and self-weight [Abdelrahman et al. 1993, Ahmad and Hadhrami 2009].
1.2 Advantages of light weight concrete
Ascomparisontosteel,thelowstrength-to-weightratioof normal-weight concrete is one of the material's most significant drawbacks. This problem of concrete can be alleviated proportionally by the production of lightweight concrete, especially lightweight concrete with a high strength. Structural lightweight concrete is classified as a uniqueformofconcrete [Kostmatka et al., 2002]
PROPERTIES OF LIGHT WEIGHT CONCRETE
Zhao et al [2012] haveinvestigatedtheinfluenceofinitial water curing on the compressive strength of light weight aggregate (self-compacting) concrete. They showed that specimens subjected to air drying exhibited greater compressive strength at 28 days than those subjected to wet curing. In addition, they determined that 7-day initial water curing and subsequent room exposure are more advantageous for the development of compressive strength in self-compacting concrete than 3, 14, and 28dayinitialwatercuring.
Twenty-one distinct forms of artificial aggregates were produced from industrial by-products by [Shaiksha vali et al. 2020], with the inclusion of glass fibres and a pelletization period of 17 minutes, coupled with a water contentof28%.Afterbeingmade,thefreshpelletswerelet to air dry for 24 hours before the aggregates were hardened using a cold-bonding procedure (Water Curing) at room temperature for 28 days. According to the research,12mmF21aggregatehasthegreatestindividual aggregate compressive strength at 48.1MPa. The F16 aggregate has the worst impact strength, at only 13%. Similarly, F14 aggregate had the lowest water absorption at 16.3%. It has been recognised that the interaction of binderswithfibresduring aggregate productioniscrucial to the production of artificial aggregates with high strength.Coarseaggregatesforstructuralconcretemaybe producedusingthepelletizationproceduresdevelopedby Rajamane et al. (2004) using fly ash. Also, the group of specialistscalculatedtheaggregate'sbulkdensity,relative density, water permeability, and crushing value. When madeusingbondedflyashcoarseaggregate,thisconcrete has a considerable slump, is relatively light, and satisfies the requirements of IS 456-2000 for structural grade minimum concrete. A battery of tests, including permeability to water and chloride, as well as a high rate of water absorption, demonstrate the material's remarkableresilience.
The effects of utilizing varied coarse aggregates were studied by Kayali O. (2008). Granite, dacite,
commercially available pelletized fly ash aggregates (SP), and synthetic fly ash aggregates fabricated from fly ash were all used as coarse aggregates in the study (FAA). Using the aforementioned coarse particles, four unique concrete mixtures were produced. Concrete made using industrial flyashpellets(SP concrete)and concrete made with synthetic fly ash aggregates (FAA concrete) were givendifferentnames.
Usingaslumpcone,thequalityofallfourconcreterecipes was evaluated. Slump in concrete made with SP and FAA was much higher than in concrete made with granite aggregates. There was a noticeable drop in concrete density to the use of fly ash aggregates. The consequence was that both SP and FAA concrete were less dense than regularconcrete.
Priyadharshini et al. (2011) developed artificial coarse aggregates by partially replacing fly ash and cement for naturalcoarseaggregates.Thepelltizationprocessisused to recover the natural resources of artificial aggregates from room-temperature-dried, fresh aggregates. The curing was completed utilising a cold-bonded technique that will be used as an aggregate additive in concrete. Nonetheless, it meets the minimal requirements for structural lightweight concrete while having 48% less compressive strength than ordinary concrete. Crushed fly ash aggregates with a rounded shape were easier to manipulate than crushed aggregates with sharp angles. It was determined that fly ash concrete is 15% less dense thanconventionalconcrete.
Geetha, et al (2011) studiedthecharacteristicsoffly-ash sintered aggregates. To enhance the properties of these aggregates,avarietyofclaybinderswereused.Inorderto enhance the characteristics of the aggregates, the dose of the binder and the sintering temperature were increased. Kaolinite & metakaolin binders resulted in a greater than 10%fineaggregate.Itwasfoundthatthecharacteristicsof aggregatedependgreatlyonthebindertype.
YaĆar et al. (2003) studied lightweight structural ideas. Concrete benefiting from the use of basaltic pumice the second objective is to build a structure that is more costeffective. After the addition of fly ash, the SLWC mixture become greener. The density of the projected quantity of Portland cement was 500 kg/m3. The fly ash SLWC mixture was made by substituting 20% of the Portland cement with fly ash. 1860 kg/m3 was the weight of the atmospheric dry unit. In addition, it contains 28 MPa and 29 MPa, respectively. 3.4 mpa. They indicated that SLWC witha cylindermust use a lightweight aggregateto attain 25MPacompressivestrength.Usingflyashenablesforthe creationofcost-effectiveSLWCovertime.
Ramadan et al. (2007) created a lightweight tetrapod aggregate from calcium-rich fly ash, which exhibited low weight, strength, high penetration, and interlocking properties.Inaddition,thephysico-mechanicalproperties of the created normal fly ash aggregate were determined. Itwasalsodeterminedthatincreasingtheamountoflime improvedthemixture'sperformance.
The features of fly ash aggregates suitable for use as coarse aggregates were examined by Nadesan and Dinakar (2017).The followingconclusionswerereached as a result of their review: Noting that the fineness of the fly ash has a considerable effect on the aggregate's physicalpropertiesisimportant.Theaggregatesofflyash exhibited a spherical shape and a specific gravity ranging from 1.33 to 2.35. The permeability and chloride penetration of fly ash aggregates are lower than those of conventional aggregates. In terms of corrosion resistance, concrete with fly ash aggregate beat conventional concrete.
Vasugi and Ramamurthy (2014) producedcoalpondash aggregates using two different types of binder. As binder and Ca(OH)2 doses were raised, the efficiency of palletisation improved. By increasing binder kaolinite/local clay and 5â12 bentonite and a sintering temperature of 900â1100 Celsius , bulk density and 10% fines value rose. The TPFV of clay aggregate was much more than that of bentonite, which was 4.5 tonnes. It was ideal for large-pond ash ingestion, with an up to 88 percent consumption rate. Sintering improves pore structureandbinderbindingcapabilities,henceenhancing theaggregatestrengthofsinteredpondash.Byincreasing thequantityofbinderandborax,openporosityandwater absorption were decreased. The bituminous pond ash aggregatewasdenserandmoredurable.
The two classes of F fly ash aggregate was explored by Acar et al (2013). Both the sintering temperature and time were played about with. Bulk, water permeability, shrinkage, and elasticmodulus were used asindicators of sinteringeffectiveness.Microstructuralandphasechanges caused by sintering were also analysed by scanning electron microscopy (SEM) and x-ray diffraction (XRD). Flyashisfavouredbecauseofitssuperiormicrocrystalline structure,higherdensityandstrength,andlowerporosity, waterpermeability,anddryingshrinkagevalues
Anja Terzic, et al (2015) developed four different variants of LWA. Mechanical activated or non-activated reducedflyashandwaterglasspelletsjoinedandsintered in cold. Strength of concrete, flexural strength, permeability, shrinkage, and young's modulus tests were used to compare the lightweight concrete's performance to that of conventional concrete. This LWC had behaviour similartoordinaryconcrete.
Zhang and Poon (2015) conductedathoroughanalysisof the characteristics of lightweight aggregate concrete. In ordertoachievethedesired 28-daycompressivestrength of30MPa,sixdifferentconcretemixturesweredeveloped: a control mix using only normal-weight aggregates and a w/c of0.6,andfivelight-weightaggregateconcretemixes using either zero, 25%, 50%, 75%, or 100% Furnace BottomAsh(FBA)inplaceofnatural fineaggregate,all at aw/cof0.39. A28-dayoven-drieddensityofabout1500 kg/m3 wasattainedforthelightweightaggregateconcrete employing 100% FBA to substitute crushed fine stone, as shown by the results of the hardened concrete characteristics testing. As can be seen from the results of the tests, the light weight aggregate concrete is weaker and less rigid than the conventional aggregate concrete. Theheatinsulationpropertytestshowedthatthethermal conductivity could be reduced to around 70% of the controlbyemployingtheporouslightweightaggregate.
Muthusamy et al. (2015) lookedintotheeffectofvarying levels of ash replacement on the compressive strength of oil palm shell light weight mixed concrete by adjusting variablessuchasthewater-cementratio,superplasticizer, sandcontent,andcementcontent.Atthisearlystageofthe study,ashwithvaryinglevelsofreplacementwerecreated and evaluated for their compressive strength. After that, experimentswereconductedwith20%POFAsubstitution, since this amount yields the maximum compressive strength result. Experiments were carried out with two distinct mixes to determine the impact of varying the water percentage, super plasticizer percentage, sand percentage, and cement quantity. Cubes of concrete made from plainoilpalmshell lightweightaggregate(0%Palm Oil Fuel Ash; POFA) were made as a control, and cubes of concrete made from oil palm shell light weight aggregate containing 20% POFA; POFA were also made. All samples werecuredinwateruntilthedayoftesting.
Physical and mechanical features of high-strength, lightweight aggregate concrete made using expanded clay aggregate were tested by Serkan Subasi (2009). There was a significant increase in strength when employing a cement concentration of 450 Kg/m3 among concrete mixes, and the mechanical qualities may be improved by adding 10% fly ash. It may be possible to reduce the cementloadandthusthecementexpenditure.
Josef Hadi Pramana et al. (2010) foundthatlightweight concrete can be used as a coarse aggregate instead of regularconcrete.Energymaybeabsorbedbyusingeither aerated concrete or lightweight aggregate concrete. Depending on the materials employed, aerated concrete's homogenised microstructure of its aerated component and air space entrapment in cement contribute to its effective energy absorption. To mitigate localised damage from ballistic loading, lightweight aggregate concrete is
strengthened. Lighter concrete has higher impact resistance than regular concrete because of its lower modulusofelasticityandhighertensilestraincapacity.
Rajamane et al. (2006) havereported thespecificsof an experiment into the usage of fly ash-based lightweight aggregate as coarse aggregate in polymer concrete using sandflyashandpolyesterresinasadditionalcomponents. They found that the ratio of tensile strength to compressive strength for such polymer concrete was significantly higher than that of traditional concrete, and that the density of polymer concrete was reduced when lightweightaggregatewasincorporated.
Kockalan and Ozturan (2010) investigatedtheimpactof two types of lightweight fly ash aggregates on the structural behaviour of concrete mixtures. Using cube compressive strength, Young's modulus, and tensile strength, the mechanical strength parameters of LWC specimens and NWC specimens were examined. Chloride permeability were used to evaluate the durability of concrete. When oven-dried density improved, then the compressive strength increased. The 28-day and 56-day concretesamplesdid notfail sincetheirdurabilityfactors weremorethantheneeded85or90towithstandfreezing andthawing.
3. CONCLUSION
Based on a review of the literature, the following findings maybedrawn:
a. Concrete's density might be decreased. When lightweight aggregates were included in the concreteblend
b. Light weight concrete has higher impact resistance than regular concrete because of its lower modulus of elasticity and higher tensile straincapacity.
c. Light weight aggregates made from fly ash exhibited low weight, strength, high penetration, andinterlockingproperties.
d. The heat insulation property test revealed that the thermal conductivity of the porous lightweight aggregate may be lowered to around 70%ofthecontrollevel.
e. Lightweight concrete exhibited similar characteristics to standard concrete. Hence, lightweight aggregates may be used in place of naturalstoneaggregate
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