Admixtures
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This document discusses various types of admixtures used in concrete, including their functions, compositions, and advantages. It defines admixtures as materials other than water, aggregates, cement, and fiber that are added to concrete mixtures to modify properties. The main types of admixtures discussed are air-entraining, water-reducing, superplasticizers, and set-retarding admixtures. Air-entrainers introduce tiny air bubbles that increase durability. Water-reducers and superplasticizers increase workability without increasing water content. Set-retarders delay the initial setting of concrete. The document provides details on the chemical compositions and functioning of different admixture types.
![Mineral AdmixturesMineral Admixtures
• Mineral admixtures (fly ash, silica fume [SF], andMineral admixtures (fly ash, silica fume [SF], and
slags) are usually added to concrete in larger amountsslags) are usually added to concrete in larger amounts
to enhance the workability of fresh concreteto enhance the workability of fresh concrete; to improve; to improve
resistance of concrete to thermal cracking, alkali-aggregateresistance of concrete to thermal cracking, alkali-aggregate
expansion, and sulfate attack; and to enable a reduction inexpansion, and sulfate attack; and to enable a reduction in
cement content.cement content.
• Fly AshFly Ash
• Silica FumeSilica Fume
• Ground Granulated Blast Furnace SlagGround Granulated Blast Furnace Slag](https://image.slidesharecdn.com/admixtures-170303204533/85/Admixtures-9-320.jpg)
Admixtures
- 2. AdmixturesAdmixtures • The term admixture as “a material other thanThe term admixture as “a material other than water, aggregates, hydraulic cement, and fiberwater, aggregates, hydraulic cement, and fiber reinforcement, used as an ingredient of a cementitiousreinforcement, used as an ingredient of a cementitious mixturemixture to modify its freshly mixed, setting, or hardenedto modify its freshly mixed, setting, or hardened properties and that is added to the batch before or during itsproperties and that is added to the batch before or during its mixing.mixing. • Producers use admixtures primarily to reduce the costProducers use admixtures primarily to reduce the cost of concrete construction; to modify the properties ofof concrete construction; to modify the properties of hardened concrete; to ensure the quality of concretehardened concrete; to ensure the quality of concrete during mixingduring mixing, transporting, placing, and curing; and to, transporting, placing, and curing; and to overcome certain emergencies during concrete operations.overcome certain emergencies during concrete operations.
- 4. HistoryHistory • TheThe use of natural admixtures in concreteuse of natural admixtures in concrete was a logicalwas a logical progression.progression. • Materials used as admixtures included milk and lard byMaterials used as admixtures included milk and lard by the Romans; eggsthe Romans; eggs during the middle ages in Europe;during the middle ages in Europe; polishedpolished glutinous rice paste, lacquer, tung oil, blackstrapglutinous rice paste, lacquer, tung oil, blackstrap molasses,molasses, • Extracts from elm soaked in water and boiled bananas byExtracts from elm soaked in water and boiled bananas by the Chinese;the Chinese; and in Mesoamerica and Peru, cactus juice andand in Mesoamerica and Peru, cactus juice and latex from rubber plants.latex from rubber plants. • The Mayans also used bark extracts and other substancesThe Mayans also used bark extracts and other substances as set retardersas set retarders to keep stucco workable for a long period ofto keep stucco workable for a long period of time.time.
- 6. FunctionFunction • IncreaseIncrease workabilityworkability withoutwithout increasingincreasing waterwater contentcontent oror decrease the water content at the same workability;decrease the water content at the same workability; • Retard or accelerateRetard or accelerate time of initial setting;time of initial setting; • Reduce or prevent shrinkageReduce or prevent shrinkage or create slight expansion;or create slight expansion; • Modify the rate or capacityModify the rate or capacity for bleeding;for bleeding; • Reduce segregationReduce segregation;; • Improve pumpabilityImprove pumpability;; • Retard or reduce heat evolutionRetard or reduce heat evolution during early hardening;during early hardening;
- 7. FunctionFunction • Accelerate the rate of strengthAccelerate the rate of strength development at early ages;development at early ages; • Increase strengthIncrease strength (compressive, tensile, or flexural);(compressive, tensile, or flexural); • IncreaseIncrease durabilitydurability oror resistanceresistance toto severesevere conditionsconditions ofofexposure,exposure, includingincluding applicationapplication ofof deicingdeicing saltssalts andand chemicals;chemicals; otherother • Decrease permeabilityDecrease permeability of concrete;of concrete; • Control expansion caused by the reactionControl expansion caused by the reaction of alkalies withof alkalies with potentially reactive aggregate constituents;potentially reactive aggregate constituents; • Increase bond of concrete to steelIncrease bond of concrete to steel reinforcement;reinforcement; • Improve impact and abrasionImprove impact and abrasion resistance;resistance;
- 8. Chemical AdmixturesChemical Admixtures • Chemical admixtures are added to concrete in veryChemical admixtures are added to concrete in very small amounts mainly for the entrainment of airsmall amounts mainly for the entrainment of air, reduction, reduction of water or cement content,of water or cement content, plasticization of fresh concreteplasticization of fresh concrete mixtures, or control of setting time.mixtures, or control of setting time. • Air-EntrainmentAir-Entrainment • Water-ReducingWater-Reducing • Set-RetardingSet-Retarding • AcceleratingAccelerating • Super-plasticizersSuper-plasticizers
- 9. Mineral AdmixturesMineral Admixtures • Mineral admixtures (fly ash, silica fume [SF], andMineral admixtures (fly ash, silica fume [SF], and slags) are usually added to concrete in larger amountsslags) are usually added to concrete in larger amounts to enhance the workability of fresh concreteto enhance the workability of fresh concrete; to improve; to improve resistance of concrete to thermal cracking, alkali-aggregateresistance of concrete to thermal cracking, alkali-aggregate expansion, and sulfate attack; and to enable a reduction inexpansion, and sulfate attack; and to enable a reduction in cement content.cement content. • Fly AshFly Ash • Silica FumeSilica Fume • Ground Granulated Blast Furnace SlagGround Granulated Blast Furnace Slag
- 10. Air-EntrainmentAir-Entrainment • AnAn air-entraining agent introduces air in the form of minute bubblesair-entraining agent introduces air in the form of minute bubbles distributed uniformly throughout the cement paste.distributed uniformly throughout the cement paste. • TheThe main types include salts of wood resinsmain types include salts of wood resins, animal or vegetable fats and oils, animal or vegetable fats and oils andand sulphonated hydrocarbons.sulphonated hydrocarbons. • Entrained air is intentionally incorporated,Entrained air is intentionally incorporated, minute spherical bubbles ofminute spherical bubbles of size ranging fromsize ranging from 5 microns to 80 microns distributed evenly in the entire5 microns to 80 microns distributed evenly in the entire mass of concrete.mass of concrete.
- 11. Air Entraining AdmixtureAir Entraining Admixture
- 12. Air-EntrainmentAir-Entrainment • TheThe major proportion of commercial productsmajor proportion of commercial products isis based on the following chemical materials, set outbased on the following chemical materials, set out in order of probable decreasing use;in order of probable decreasing use; • Abietic and pimeric acid saltsAbietic and pimeric acid salts • Fatty Acid saltsFatty Acid salts • Alkyl - aryl sulphonatesAlkyl - aryl sulphonates • Alkyl sulphonatesAlkyl sulphonates • Phenol ethoxylatesPhenol ethoxylates
- 13. Air-Entrainment: AdvantagesAir-Entrainment: Advantages • DurabilityDurability • Reduced bleeding and segregationReduced bleeding and segregation because of :because of : • Bubble acting as extra fine fillerBubble acting as extra fine filler Attachment of air bubbles withAttachment of air bubbles with cement particlecement particle and linking them.and linking them. • Increase in inter particle attraction caused by adsorptionIncrease in inter particle attraction caused by adsorption of airof air entrainer.entrainer. and increased total surface area of constituents relative to water volume.and increased total surface area of constituents relative to water volume. • Water flow between cementWater flow between cement particles is restricted.particles is restricted. • Workability increased due to action of air bubblesWorkability increased due to action of air bubbles as ball bearing whichas ball bearing which assist movement of particles each other.assist movement of particles each other.
- 15. Water-Reducing (Plasticizers)Water-Reducing (Plasticizers) • A material, which either increases workability of freshlyA material, which either increases workability of freshly mixed concrete without increasing water cement ratiomixed concrete without increasing water cement ratio oror maintains workability with a reduced amount of water, ismaintains workability with a reduced amount of water, is termed as water reducing admixturetermed as water reducing admixture • As their name implies, the function of water reducingAs their name implies, the function of water reducing admixture is to reduce the water content of the mixadmixture is to reduce the water content of the mix,, usually by 5 to 10%, sometimes (in concrete of very highusually by 5 to 10%, sometimes (in concrete of very high workability) up-to 15%.workability) up-to 15%. • Thus, the purpose of using a water reducing admixtureThus, the purpose of using a water reducing admixture in a concrete mix is to allow a reduction in the waterin a concrete mix is to allow a reduction in the water cementcement ratio while retaining the desired workability or,ratio while retaining the desired workability or, alternatively,to improve its workability at a given water cementalternatively,to improve its workability at a given water cement ratio.ratio.
- 17. Water-Reducing (Plasticizers)Water-Reducing (Plasticizers) • The actual reduction in water depends on dose ofThe actual reduction in water depends on dose of admixtures, cement content, type of aggregate used,admixtures, cement content, type of aggregate used, ratioratio of cement, fine and coarse aggregate etc.of cement, fine and coarse aggregate etc. • The chemicals used as plasticizerThe chemicals used as plasticizer (water reducing(water reducing admixtures) are as follows:admixtures) are as follows: • Lignosulfonic acids, derivatives and their salts.Lignosulfonic acids, derivatives and their salts. • Hydroxylated carboxylic acids, their salts and derivatives.Hydroxylated carboxylic acids, their salts and derivatives. • Nepthalene sulphonic acid basedNepthalene sulphonic acid based • Sulfonated melamine polycondensation productsSulfonated melamine polycondensation products
- 19. Water-Reducing (Plasticizers)Water-Reducing (Plasticizers) • Dispersion Effect: Portland cement will have aDispersion Effect: Portland cement will have a tendency to flocculate in wet concretetendency to flocculate in wet concrete. These. These flocculationflocculation entraps certain amount of water usedentraps certain amount of water used in the mix andin the mix and thereby all the water is not freely available to fluidify the mix.thereby all the water is not freely available to fluidify the mix. When cement particles are deflocculated, the waterWhen cement particles are deflocculated, the water trapped inside the flocs gets released and now availabletrapped inside the flocs gets released and now available to fluidify the mixto fluidify the mix.. • Retarding Effect: It is mentioned earlier thatRetarding Effect: It is mentioned earlier that plasticizer gets adsorbed on the surface of cementplasticizer gets adsorbed on the surface of cement particlesparticles and form a thin sheath.and form a thin sheath. This thin sheath inhibitsThis thin sheath inhibits the surface hydration reaction between water and cementthe surface hydration reaction between water and cement as longas long as sufficientas sufficient plasticizer molecules are available atplasticizer molecules are available at the particle/solution interface.the particle/solution interface.
- 21. Water-Reducing (Plasticizers)Water-Reducing (Plasticizers) • Dispersion Effect: Portland cement will have a tendencyDispersion Effect: Portland cement will have a tendency to flocculate in wet concreteto flocculate in wet concrete. These flocculation entraps. These flocculation entraps certain amount of water used in the mix and thereby all the watercertain amount of water used in the mix and thereby all the water is not freely available to fluidify the mix.is not freely available to fluidify the mix. When cementWhen cement particles are deflocculated, the water trapped inside theparticles are deflocculated, the water trapped inside the flocs gets released and now available to fluidify the mixflocs gets released and now available to fluidify the mix.. • Retarding Effect: It is mentioned earlier that plasticizerRetarding Effect: It is mentioned earlier that plasticizer gets adsorbed on the surface of cement particles andgets adsorbed on the surface of cement particles and form a thin sheath.form a thin sheath. This thin sheath inhibits the surfaceThis thin sheath inhibits the surface hydration reaction betweenhydration reaction between water and cement as long aswater and cement as long as sufficient plasticizer molecules are available at thesufficient plasticizer molecules are available at the particle/solution interface.particle/solution interface.
- 23. Water-Reducing: AdvantagesWater-Reducing: Advantages • TheyThey increaseincrease thethe workabilityworkability ofof thethe concreteconcrete withoutwithout reducingreducing thethe compressivecompressive strengthstrength oror withoutwithout changingchanging water-water- cementcement ratio.ratio. ThisThis isis particularlyparticularly usefuluseful whenwhen concreteconcrete porespores areare restrictedrestricted eithereither duedue toto congestedcongested reinforcementreinforcement oror duedue toto thinthin sectionssections • HighHigh strengthstrength cancan bebe obtainedobtained withwith thethe samesame cementcement contentcontent byby reducingreducing waterwater cementcement ratioratio.. • AA savingsaving inin thethe quantityquantity ofof cementcement (approx.(approx. uptoupto 10%)10%) cancan bebe achievedachieved keepingkeeping thethe samesame water/water/ cementcement ratioratio andand workability.workability.
- 25. SuperplasticizersSuperplasticizers • The admixtures capable of reducingThe admixtures capable of reducing water content by aboutwater content by about 30% are30% are known as super plasticizersknown as super plasticizers.. • At a given water /cement ratio and water content in theAt a given water /cement ratio and water content in the mix, the dispersing action of super plasticize increasesmix, the dispersing action of super plasticize increases thethe workability of concrete, typically by raising the slumpworkability of concrete, typically by raising the slump from 75mm to 200 mm, the mix remaining cohesive.from 75mm to 200 mm, the mix remaining cohesive. • The resulting concrete can be placed with little or noThe resulting concrete can be placed with little or no compaction andcompaction and is not subject to excessive bleeding oris not subject to excessive bleeding or segregation.segregation.
- 27. SuperplasticizersSuperplasticizers • ThereThere existexist fourfour mainmain categoriescategories ofof super-plasticizerssuper-plasticizers basedbased onon theirtheir chemicalchemical composition:composition: • melaminemelamine formaldehydeformaldehyde condensatescondensates • SulfonatedSulfonated naphthalenenaphthalene formaldehydeformaldehyde condensatescondensates • ModifiedModified lingo-sulfonateslingo-sulfonates • OthersOthers suchsuch asas sulfonicsulfonic acidacid estersesters andand carbohydratecarbohydrate estersesters
- 29. Superplasticizers: AdvantagesSuperplasticizers: Advantages • Cement content can be reduced to a greater extent keepingCement content can be reduced to a greater extent keeping the same water/cement ratio.the same water/cement ratio. This will lead to economy.This will lead to economy. • Water-cement ratio can be reduced significantly keepingWater-cement ratio can be reduced significantly keeping same cement content and workability.same cement content and workability. This will lead toThis will lead to increase in strength.increase in strength. • Higher workability at very low water cement ratioHigher workability at very low water cement ratio likelike casting concrete with heavy reinforcement..casting concrete with heavy reinforcement.. • Reduction in permeabilityReduction in permeability • Where early strength development is required inWhere early strength development is required in prestressed concrete or casting of floorprestressed concrete or casting of floor, where early, where early access for finishing equipment is requiredaccess for finishing equipment is required
- 32. Set-RetardingSet-Retarding • This type of chemical admixtures decreases the initialThis type of chemical admixtures decreases the initial rate of reactionrate of reaction betweenbetween cement and water and therebycement and water and thereby retards the setting of concrete.retards the setting of concrete. • It functions by coating the surface of CIt functions by coating the surface of C33SS (Tri calcium(Tri calcium silicate) components, thus, delaying this reaction with thesilicate) components, thus, delaying this reaction with the water.water. • Reaction products are slow to form as such the settingReaction products are slow to form as such the setting and hardening of concreteand hardening of concrete are delayed reducing earlyare delayed reducing early compressive strengths.compressive strengths. • Retardation in setting time up to 8-10 hoursRetardation in setting time up to 8-10 hours is possibleis possible by suitable use of retarders.by suitable use of retarders.
- 34. Set-RetardingSet-Retarding The main ingredients of retarders are as follows:The main ingredients of retarders are as follows: •Ligno-sulphonic acids and their salts. e.g. Na, Ca or NH4,Ligno-sulphonic acids and their salts. e.g. Na, Ca or NH4, •Hydro-carboxylic acids and their salts.Hydro-carboxylic acids and their salts. •Carbohydrates including sugar.Carbohydrates including sugar. •Inorganic salts based on flourates, phosphates, oxides, borax andInorganic salts based on flourates, phosphates, oxides, borax and magnesium salts.magnesium salts.
- 35. Set-Retarding: AdvantagesSet-Retarding: Advantages • Improves workability, cohesion and extends setting time,Improves workability, cohesion and extends setting time, provides protection against delaysprovides protection against delays and stoppages andand stoppages and facilitates keeping workable concrete for extended period .facilitates keeping workable concrete for extended period . • In the large construction, good workability of theIn the large construction, good workability of the concrete throughout the placing period and prevention ofconcrete throughout the placing period and prevention of cold jointscold joints is ensured by adding retarders in the concrete.is ensured by adding retarders in the concrete. • Extended setting time minimise risks of long distanceExtended setting time minimise risks of long distance delivery in hot weather, improves pumpability of concretedelivery in hot weather, improves pumpability of concrete by extended setting period and improved workability ofby extended setting period and improved workability of concrete.concrete.
- 36. Set-Retarding: AdvantagesSet-Retarding: Advantages • Reduces bleeding and segregationReduces bleeding and segregation where poorwhere poor sand grading are unavoidable.sand grading are unavoidable. • Reduces adverse environmental effects ofReduces adverse environmental effects of various nature on concretevarious nature on concrete and embedded steeland embedded steel by considerable reduction in permeability.by considerable reduction in permeability.
- 37. Effect of use of RetarderEffect of use of Retarder • Retarding admixture forms a film around the cementRetarding admixture forms a film around the cement grain that prevent or delays the reaction with watergrain that prevent or delays the reaction with water.. After some times, this film breaks and normal hydrationAfter some times, this film breaks and normal hydration takes place.takes place.
- 38. Accelerating AdmixturesAccelerating Admixtures • These admixtures when added to concrete,These admixtures when added to concrete, mortar or grout increases the rate of hydrationmortar or grout increases the rate of hydration of hydraulic cementof hydraulic cement, shortens the time of set,, shortens the time of set, accelerates the hardening or development ofaccelerates the hardening or development of strength of concrete/ mortar.strength of concrete/ mortar. • These admixtures function by interaction withThese admixtures function by interaction with CC33S (Tri- calcium silicate)S (Tri- calcium silicate) component of the cementcomponent of the cement thus increasing the reaction between cement and waterthus increasing the reaction between cement and water
- 40. Accelerating AdmixturesAccelerating Admixtures • ManyMany substancessubstances areare concrete. They includeconcrete. They include Known toKnown to AlkaliAlkali AActct asas acceleratorsaccelerators forfor Hydroxides,Hydroxides, Silicates,Silicates, Fluoro-Fluoro- Silicates,Silicates, OrganicOrganic Compounds,Compounds, CalciumCalcium Formates,Formates, CalciumCalcium Nitrates, Calcium ThioNitrates, Calcium Thio Potassium Carbonates,Potassium Carbonates, Chlorides.Chlorides. Sulphate,Sulphate, AluminiumAluminium Chlorides,Chlorides, SodiumSodiumChloridesChlorides && CalciumCalcium
- 41. Accelerating Admixtures: AdvantagesAccelerating Admixtures: Advantages • Shortens the setting time of cement and therefore increasesShortens the setting time of cement and therefore increases the rate of gain of strength.the rate of gain of strength. • Enables earlier release from precast mouldsEnables earlier release from precast moulds thus speedingthus speeding production.production. • Reduces segregation and increase densityReduces segregation and increase density and compressiveand compressive strength.strength. • Cures concrete faster and therefore uniformCures concrete faster and therefore uniform curing incuring in winter and summer can be achieved.winter and summer can be achieved. • Reduces water requirements, bleeding, shrinkageReduces water requirements, bleeding, shrinkage and timeand time required for initial set.required for initial set.
- 42. Effect of use of Accelerating AdmixturesEffect of use of Accelerating Admixtures
- 43. Mineral AdmixturesMineral Admixtures • Mineral admixtures are finely divided siliceousMineral admixtures are finely divided siliceous materials which are added to concrete in relativelymaterials which are added to concrete in relatively large amountslarge amounts, generally in the range, generally in the range 20 to 7020 to 70 percent by mass of the total cementitious materialpercent by mass of the total cementitious material..
- 44. Ecological AdvantageEcological Advantage • Power plants using coal as fuel and metallurgicalPower plants using coal as fuel and metallurgical furnaces producing cast iron, silicon metal,furnaces producing cast iron, silicon metal, andand ferrosilicon alloys are the major sources of byproducts thatferrosilicon alloys are the major sources of byproducts that areare being produced at the rate of millions of tonnes everybeing produced at the rate of millions of tonnes every year in many countries.year in many countries. • Dumping of these by-products into landfills and streamsDumping of these by-products into landfills and streams amounts to a wasteamounts to a waste of the material and causes seriousof the material and causes serious environmental pollution.environmental pollution. • Disposal as concrete aggregate or for road baseDisposal as concrete aggregate or for road base construction is a low-value use which does not utilizeconstruction is a low-value use which does not utilize thethe pozzolanic and cementitious potential of those materials.pozzolanic and cementitious potential of those materials.
- 45. Ecological AdvantageEcological Advantage • WithWith properproper qualityquality control,control, largelarge amountsamounts ofof manymany industrialindustrial by-productsby-products cancan bebe incorporatedincorporated intointo concrete,concrete, eithereither inin thethe formform ofof blendedblended portlandportland cementcement oror asas mineralmineral admixtures.admixtures. • WheneverWhenever aa pozzolanicpozzolanic and/orand/or cementitiouscementitious byproductbyproduct cancan bebe usedused asas aa partialpartial replacementreplacement forfor portlandportland cementcement inin concrete,concrete, itit representsrepresents significantsignificant energyenergy andand costcost savings.savings.
- 46. AdvantageAdvantage • It has been amply demonstrated that the bestIt has been amply demonstrated that the best pozzolans in optimum proportionspozzolans in optimum proportions mixed with Portlandmixed with Portland cement improves many qualities of concrete, such as:cement improves many qualities of concrete, such as: • Lower the heat of hydrationLower the heat of hydration and thermal shrinkage;and thermal shrinkage; • Increase theIncrease the water tightnesswater tightness;; • (Reduce the alkali-aggregate reaction;(Reduce the alkali-aggregate reaction; • Improve resistance to attack by sulphate soilsImprove resistance to attack by sulphate soils and sea water;and sea water; • Improve workabilityImprove workability;; • Lower costs.Lower costs.
- 47. Pozzolanic ReactionPozzolanic Reaction • Pozzolana + Calcium Hydroxide +Pozzolana + Calcium Hydroxide + WaterWater • TheThe mechanismmechanism byby whichwhich pozzolanicpozzolanic C – S – H (Gel)C – S – H (Gel) RReactioneaction exercisesexercises aa beneficialbeneficial effecteffect onon thethe propertiesproperties ofof concreteconcrete isis thethe samesame irrespectiveirrespective ofof whetherwhether aa pozzolanicpozzolanic materialmaterial isis addedadded toto • Concrete inConcrete inthe form of a mineral admixture or as athe form of a mineral admixture or as a component of blended portland cement.component of blended portland cement. • Pozzolanic (e.g., low-calcium fly ash),Pozzolanic (e.g., low-calcium fly ash), • Cementitious (e.g., granulated iron blast-furnace slag),Cementitious (e.g., granulated iron blast-furnace slag), • Both cementitious and pozzolanic (e.g., highcalcium flyBoth cementitious and pozzolanic (e.g., highcalcium fly ash)ash)
- 48. ClassificationClassification • Natural materials:Natural materials: have been processed for the solehave been processed for the sole purpose of producing a pozzolan.purpose of producing a pozzolan. Processing usuallyProcessing usually involves crushing, grinding, and size separation;involves crushing, grinding, and size separation; in some cases it may also involve thermalin some cases it may also involve thermal activationactivation.. • By-product materialsBy-product materials: are not the primary: are not the primary products of the industry producing them.products of the industry producing them. Industrial byproducts may or may not requireIndustrial byproducts may or may not require any processing.any processing.
- 49. Natural PozzolansNatural Pozzolans • Volcanic glasses: Santorini Earth of Greece, BacoliVolcanic glasses: Santorini Earth of Greece, Bacoli Pozzolan of Italy, and Shirasu Pozzolan of Japan arePozzolan of Italy, and Shirasu Pozzolan of Japan are examples of pozzolanic materialsexamples of pozzolanic materials which derive their lime-which derive their lime- reactivitycharacteristic mainly from the unalteredreactivitycharacteristic mainly from the unaltered aluminosilicate glass.aluminosilicate glass. • Volcanic tuffs: Pozzolans of Segni-Latium (Italy), andVolcanic tuffs: Pozzolans of Segni-Latium (Italy), and trass of Rheinland and Bavariatrass of Rheinland and Bavaria (Germany),represent typical(Germany),represent typical volcanic tuffs.volcanic tuffs. • Calcined clays or shales: clay and shales will notCalcined clays or shales: clay and shales will not show appreciable reactivity with lime unlessshow appreciable reactivity with lime unless the crystalthe crystal structures of the clay minerals present are destroyed by heatstructures of the clay minerals present are destroyed by heat treatmenttreatment
- 51. Natural PozzolansNatural Pozzolans • DiatomaceousDiatomaceous earth:earth: ThisThis groupgroup ofof pozzolanspozzolans isis characterizedcharacterized byby materialsmaterials ofof organicorganic origin.origin. • DiatomiteDiatomite isis aa hydratedhydrated amorphousamorphous silicasilica whichwhich isis composedcomposed ofof skeletalskeletal shellsshells fromfrom thethe cellcell wallswalls ofof manymany varietiesvarieties ofof microscopicmicroscopic aquaticaquatic algae.algae. TheThe largestlargest knownknown depositdeposit isis inin California.California.
- 52. Artificial PozzolansArtificial Pozzolans • Fly ashFly ash • Blast Furnace SlagBlast Furnace Slag • Silica FumeSilica Fume • Rice Husk ashRice Husk ash • MetakaolineMetakaoline • Surkhi.Surkhi.
- 53. FlyFly AshAsh • Fly ash is finely divided residue resulting from theFly ash is finely divided residue resulting from the combustion of powdered coal and transportedcombustion of powdered coal and transported by theby the flue gases and collected by electrostatic precipitator.flue gases and collected by electrostatic precipitator. • Fly ash is the most widely used pozzolanic materialFly ash is the most widely used pozzolanic material all overall over the world.the world. • The importance and use of fly ash in concrete hasThe importance and use of fly ash in concrete has grown so much that it has almost becomegrown so much that it has almost become a commona common ingredient in concrete, particularly for making highingredient in concrete, particularly for making high strength and high performance concrete.strength and high performance concrete. • The utilisation of fly ash as a supplementaryThe utilisation of fly ash as a supplementary cementitious material.cementitious material. High volume fly ash concrete is aHigh volume fly ash concrete is a subject of current interest all over the world.subject of current interest all over the world.
- 54. Fly Ash In ConcreteFly Ash In Concrete
- 55. FlyFly AshAsh • The use of fly ash as concrete admixture not onlyThe use of fly ash as concrete admixture not only extends technical advantagesextends technical advantages to the properties of concreteto the properties of concrete but also contributes to the environmental pollution control.but also contributes to the environmental pollution control. • There are two ways that the fly ash can be used: one way isThere are two ways that the fly ash can be used: one way is to inter grind certain percentage of fly ashto inter grind certain percentage of fly ash with cementwith cement clinker at the factory to produce Portland pozzolana cementclinker at the factory to produce Portland pozzolana cement (PPC) and the second way is to use the fly ash as an(PPC) and the second way is to use the fly ash as an admixture at the time of making concrete at the site of work.admixture at the time of making concrete at the site of work. • One of the important characteristics of fly ash is theOne of the important characteristics of fly ash is the spherical form of the particlesspherical form of the particles. This shape of particle. This shape of particle improves the flowability and reduces the water demand.improves the flowability and reduces the water demand. TheThe suitability of fly ash could be decided by finding thesuitability of fly ash could be decided by finding the dry density of fully compacted sample.dry density of fully compacted sample.
- 56. Fly AshFly Ash
- 57. Effect of Fly Ash on Fresh ConcreteEffect of Fly Ash on Fresh Concrete • Use of right quality fly ash, results in reduction of water demand for desired slump. • With the reduction of unit water content, bleeding and drying shrinkage will also be reduced. • Since fly ash is not highly reactive, the heat of hydration can be reduced through replacement of part of the cement with fly ash. The reduction of temperature rise for 30% substitution of fly ash.
- 58. Effects of Fly Ash on Hardened ConcreteEffects of Fly Ash on Hardened Concrete • Fly ash, when used in concrete, contributes to the strengthFly ash, when used in concrete, contributes to the strength of concrete due to its pozzolanic reactivity. However,of concrete due to its pozzolanic reactivity. However, since the pozzolanic reaction proceeds slowlysince the pozzolanic reaction proceeds slowly, the initial, the initial strength of fly ash concrete tends to be lower than that ofstrength of fly ash concrete tends to be lower than that of concrete without fly ash.concrete without fly ash. • Due to continued pozzolanic reactivity concrete developsDue to continued pozzolanic reactivity concrete develops greater strength at later age,greater strength at later age, which may exceed that ofwhich may exceed that of the concrete without fly ash.the concrete without fly ash. • Fly ash concrete should be cured for longer period. InFly ash concrete should be cured for longer period. In this sense, fly ash concrete used in under water structuresthis sense, fly ash concrete used in under water structures such as dams will derivesuch as dams will derive full benefits of attainingfull benefits of attaining improved long term strength and water-tightness.improved long term strength and water-tightness.
- 59. Durability of ConcreteDurability of Concrete • Sufficiently cured concrete containing goodSufficiently cured concrete containing good quality fly ash shows dense structurequality fly ash shows dense structure whichwhich offers high resistivity to the infiltration of deleteriousoffers high resistivity to the infiltration of deleterious substances.substances. • It is also recognised that the addition of fly ashIt is also recognised that the addition of fly ash contributes to the reductioncontributes to the reduction of the expansionof the expansion due to alkali-aggregate reaction.due to alkali-aggregate reaction.
- 60. High Volume Fly Ash Concrete (HVFA)High Volume Fly Ash Concrete (HVFA) • High volume fly ash concrete is a concrete where in 50 to 60%High volume fly ash concrete is a concrete where in 50 to 60% flyfly ashash isis incorporated.incorporated. ItIt waswas firstfirst developeddeveloped forfor massmass lowlow heatheat ofof hydrationhydration waswas ofof concreteconcrete applicationapplication wherewhere primary consideration.primary consideration. •Subsequent work has demonstrated that this type of concreteSubsequent work has demonstrated that this type of concrete showedshowed excellentexcellent requiredrequired forfor mechanicalmechanical andand durabilitydurability propertiesproperties pavementpavementstructuralstructural applicationsapplications andand constructions.constructions. •Due to very low water content of high volume flyDue to very low water content of high volume fly ash concrete, the use of superplasticizer becomes necessaryash concrete, the use of superplasticizer becomes necessary for obtaining workable concrete. Use of air-entraining admixturesfor obtaining workable concrete. Use of air-entraining admixtures is also concurrently used.is also concurrently used.
- 61. Silica FumeSilica Fume • SilicaSilica fume,fume, alsoalso referredreferred toto asas micro silicamicro silica oror condensedcondensed silicasilica fumefume,, isis anotheranother material thatmaterial that isis usedused asas anan artificialartificial pozzolanicpozzolanic admixture.admixture. • ItIt isis aa productproduct resultingresulting fromfrom reductionreduction ofof highhigh puritypurity quartzquartz withwith coalcoal inin anan electricelectric arcarc furnacefurnace inin thethe manufacturemanufacture ofof siliconsilicon oror ferrosiliconferrosilicon alloy.alloy. • SilicaSilica fumefume risesrises asas anan oxidisedoxidised vapourvapour.. ItIt cools,cools, condensescondenses andand isis collectedcollected inin clothcloth bags.bags. • ItIt isis furtherfurther processedprocessed toto removeremove impuritiesimpurities andand toto controlcontrol particleparticle size.size. CondensedCondensed silicasilica fumefume isis essentiallyessentially siliconsilicon dioxidedioxide (more(more thanthan 90%)90%) inin nonnon crystallinecrystalline form.form. SinceSince itit isis anan airborneairborne materialmaterial likelike flyfly ash,ash, itit hashas sphericalspherical shape.shape. InfluenceInfluence onon FreshFresh ConcreteConcrete
- 63. Silica FumeSilica Fume • It is extremely fine with particle size less than 1It is extremely fine with particle size less than 1 micron and with an average diameter of about 0.1 micron,micron and with an average diameter of about 0.1 micron, about 100 times smaller than average cement particlesabout 100 times smaller than average cement particles.. Silica fume has specific surface area of about 20,000 mSilica fume has specific surface area of about 20,000 m22 /kg/kg against 230 to 300 magainst 230 to 300 m22 /kg./kg. • Silica fume has become one of the necessarySilica fume has become one of the necessary ingredients for making high strength and highingredients for making high strength and high performance concrete. In India, silica fume has beenperformance concrete. In India, silica fume has been used very rarelyused very rarely. Nuclear Power Corporation was one of. Nuclear Power Corporation was one of the first to use silica fume concrete in their Kaiga and Kotathe first to use silica fume concrete in their Kaiga and Kota nuclear power projects.nuclear power projects. • Silica fume was also used for one of the flyovers atSilica fume was also used for one of the flyovers at Mumbai where, for the first time in India 75 MPaMumbai where, for the first time in India 75 MPa concrete was used (1999).concrete was used (1999). Silica fume is also now specifiedSilica fume is also now specified for the construction of proposed Bandra-Worli sea link projectfor the construction of proposed Bandra-Worli sea link project at Mumbai.at Mumbai.
- 65. Silica FumeSilica Fume • SilicaSilica fume,fume, alsoalso referredreferred toto asas micro silicamicro silica oror condensedcondensed silicasilica fumefume,, isis anotheranother material thatmaterial that isis usedused asas anan artificialartificial pozzolanicpozzolanic admixture.admixture. • ItIt isis aa productproduct resultingresulting fromfrom reductionreduction ofof highhigh puritypurity quartzquartz withwith coalcoal inin anan electricelectric arcarc furnacefurnace inin thethe manufacturemanufacture ofof siliconsilicon oror ferrosiliconferrosilicon alloy.alloy. • SilicaSilica fumefume risesrises asas anan oxidisedoxidised vapour.vapour. ItIt cools,cools, condensescondenses andand isis collectedcollected inin clothcloth bags.bags. • ItIt isis furtherfurther processedprocessed toto removeremove impuritiesimpurities andand toto controlcontrol particleparticle size.size. CondensedCondensed silicasilica fumefume isis essentiallyessentially siliconsilicon dioxidedioxide (more(more thanthan 90%)90%) inin noncrystallinenoncrystalline form.form. SinceSince itit isis anan airborneairborne materialmaterial likelike flyfly ash,ash, itit hashas sphericalspherical shape.shape. InfluenceInfluence onon FreshFresh ConcreteConcrete
- 66. Influence on Fresh ConcreteInfluence on Fresh Concrete • Water demand increases in proportion to the amountWater demand increases in proportion to the amount of micro-silica added.of micro-silica added. The increase in waterThe increase in water demand of concrete containing micro-silica will be aboutdemand of concrete containing micro-silica will be about 1% for every 1% of cement substituted.1% for every 1% of cement substituted. • Therefore, 20 mm maximum size aggregateTherefore, 20 mm maximum size aggregate concrete, containing 10% micro-silica, will have anconcrete, containing 10% micro-silica, will have an increased water content of about 20 litres/mincreased water content of about 20 litres/m33 • Measures can be taken to avoid this increase byMeasures can be taken to avoid this increase by adjusting the aggregate gradingadjusting the aggregate grading and using super-and using super- plasticizers.plasticizers.
- 67. Influence on Fresh ConcreteInfluence on Fresh Concrete • The addition of micro-silica will lead to lowerThe addition of micro-silica will lead to lower slump but more cohesive mix.slump but more cohesive mix. The micro-silica makeThe micro-silica make the fresh concrete sticky in nature and hard to handle.the fresh concrete sticky in nature and hard to handle. • It was also found that there was large reduction inIt was also found that there was large reduction in bleeding and concrete with micro-silicableeding and concrete with micro-silica could becould be handled and transported without segregation. .handled and transported without segregation. . • It is reported that concrete containing micro-silica isIt is reported that concrete containing micro-silica is vulnerable to plastic shrinkage crackingvulnerable to plastic shrinkage cracking and,and, therefore, sheet or mat curing should be considered.therefore, sheet or mat curing should be considered.
- 68. Influence on Hardened ConcreteInfluence on Hardened Concrete • Concrete containing micro silica showedConcrete containing micro silica showed outstanding characteristics in the development ofoutstanding characteristics in the development of strength. It has been also found out thatstrength. It has been also found out that modulus of elasticitymodulus of elasticity of micro silica concrete isof micro silica concrete is less than that of concrete without micro silica at theless than that of concrete without micro silica at the same level of compressive strength.same level of compressive strength.
- 69. Rice Husk AshRice Husk Ash • RiceRice huskhusk ashash isis obtainedobtained byby burningburning causingcausing ricerice huskhusk In a controlledcontrolled mannermanner pollution.pollution. withoutwithout environmentalenvironmental • When properly burnt it has high SiOWhen properly burnt it has high SiO22 content andcontent and can be used as a concrete admixture. Rice husk ashcan be used as a concrete admixture. Rice husk ash exhibits high pozzo lanic characteristics and contributesexhibits high pozzo lanic characteristics and contributes to high strength and high impermeability of concrete.to high strength and high impermeability of concrete. • India produces about 122 million ton of paddy every year.India produces about 122 million ton of paddy every year. Each ton of paddy producers about 40 kg of RHA. ThereEach ton of paddy producers about 40 kg of RHA. There is a good potential to make use of RHA as ais a good potential to make use of RHA as a valuable pozzolanic material to give almost the samevaluable pozzolanic material to give almost the same properties as that of microsilica.properties as that of microsilica.
- 70. Rice Husk AshRice Husk Ash
- 71. SurkhiSurkhi • Surkhi,Surkhi, waswas thethe commonestcommonest pozzolanicpozzolanic materialsmaterials usedused inin India.India. • SurkhiSurkhi isis anan artificialartificial pozzolanapozzolana mademade byby powderingpowdering bricksbricks oror burntburnt clayclay balls.balls. InIn somesome majormajor works,works, forfor largelarge scalescale productionproduction ofof surkhi,surkhi, clayclay ballsballs areare speciallyspecially burntburnt forfor thisthis purposepurpose andand thenthen powdered.powdered. • ByBy itsits nature,nature, itit isis aa veryvery complexcomplex materialmaterial differingdiffering widelywidely inin itsits qualitiesqualities andand performancesperformances.. BeingBeing derivedderived fromfrom soil,soil, itsits characteristicscharacteristics areare greatlygreatly influencedinfluenced byby thethe constituentconstituent mineralmineral compositioncomposition ofof soil,soil, degreedegree ofof burningburning andand finenessfineness ofof grinding.grinding. • BecauseBecause ofof thethe complexitycomplexity ofof problemproblem therethere hashas beenbeen muchmuch confusionconfusion onon accountaccount ofof contradictorycontradictory resultsresults obtainedobtained byby variousvarious researchresearch workers.workers.
- 72. SurkhiSurkhi
- 73. SurkhiSurkhi • Now the terminologyNow the terminology “Calcined Clay Pozzolana”“Calcined Clay Pozzolana” isis used instead of the word surkhi, giving specificused instead of the word surkhi, giving specific property and composition to this construction material.property and composition to this construction material. IS 1344 of 1981 covers the specification for calcinedIS 1344 of 1981 covers the specification for calcined clayclay pozzolana for use in mortar or concrete. IS 1727pozzolana for use in mortar or concrete. IS 1727 of 1967 covers the methods of test for pozzolanicof 1967 covers the methods of test for pozzolanic materials.materials.
- 74. SurkhiSurkhi
- 75. Ground Granulated Blast Furnace SlagGround Granulated Blast Furnace Slag (GGBS)(GGBS) • Ground granulated blast-furnace slag is aGround granulated blast-furnace slag is a nonmetallic product consisting essentially of silicatesnonmetallic product consisting essentially of silicates and aluminates of calcium and other bases.and aluminates of calcium and other bases. TheThe molten slag is rapidly chilled by quenching in watermolten slag is rapidly chilled by quenching in water to form a glassy sand like granulated material.to form a glassy sand like granulated material. TheThe granulated material when further ground to less thangranulated material when further ground to less than 45 micron will have specific surface of about 400 to45 micron will have specific surface of about 400 to 600 sq m/kg(blaine)600 sq m/kg(blaine) • The performance of slag largely depends on theThe performance of slag largely depends on the chemical composition, glass content and fineness ofchemical composition, glass content and fineness of grinding.grinding.
- 76. Ground Granulated Blast Furnace SlagGround Granulated Blast Furnace Slag (GGBS)(GGBS)
- 77. Ground Granulated Blast Furnace SlagGround Granulated Blast Furnace Slag (GGBS)(GGBS) • There are two methods for making BlastThere are two methods for making Blast Furnace Slag Cement.Furnace Slag Cement. In the first methodIn the first method blast furnace slag is inter-ground with cementblast furnace slag is inter-ground with cement clinker along with gypsum.clinker along with gypsum. • In the second method blast furnace slag isIn the second method blast furnace slag is separately ground and then mixed with theseparately ground and then mixed with the cementcement..
- 78. Performance of GGBS in ConcretePerformance of GGBS in Concrete • The replacement of cement with GGBS will reduce the unitThe replacement of cement with GGBS will reduce the unit water content necessary to obtain the same slumpwater content necessary to obtain the same slump.. • This reduction of unit water content will be more pronouncedThis reduction of unit water content will be more pronounced with increase in slag content and also on the fineness ofwith increase in slag content and also on the fineness of slagslag. This is because of the surface configuration and particle shape. This is because of the surface configuration and particle shape of slag being different than cement particle.of slag being different than cement particle. • In addition, water used for mixing is not immediatelyIn addition, water used for mixing is not immediately lost,lost, asas the surface hydration of slag is slightly slower than that ofthe surface hydration of slag is slightly slower than that of cementcement • Reduced heat of hydrationReduced heat of hydration • Refinement of pore structuresRefinement of pore structures • Reduced permeabilities to the external agenciesReduced permeabilities to the external agencies • Increased resistance to chemical attack.Increased resistance to chemical attack.
- 80. (Flexible Concrete)(Flexible Concrete) Victor LiVictor Li His Flexible Concrete Bends But Doesn’t BreakHis Flexible Concrete Bends But Doesn’t Break An engineering professor at the University of Michigan (UM), Li has developedAn engineering professor at the University of Michigan (UM), Li has developed a new type of flexible concrete known as an engineered cement compositea new type of flexible concrete known as an engineered cement composite (ECC)(ECC) Conventional concrete is made by mixing sand, cement, and aggregates such asConventional concrete is made by mixing sand, cement, and aggregates such as gravel and then activating it by adding water.gravel and then activating it by adding water. ECC resembles regular concrete but can weigh up to 40 percent less, consistingECC resembles regular concrete but can weigh up to 40 percent less, consisting mostly of the same ingredients except for the coarse aggregates.mostly of the same ingredients except for the coarse aggregates. It has small polyvinyl alcohol fibers embedded within it, 8-12 millimeters longIt has small polyvinyl alcohol fibers embedded within it, 8-12 millimeters long and about 40 microns in diameter, about half the thickness of a human hair.and about 40 microns in diameter, about half the thickness of a human hair. They have a nanometer-thick surface coating that allows them to slip ratherThey have a nanometer-thick surface coating that allows them to slip rather than break under heavy loads.than break under heavy loads.
- 81. Victor LiVictor Li His Flexible Concrete Bends But Doesn’t BreakHis Flexible Concrete Bends But Doesn’t Break