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Current Developments in Current Developments in Concrete ConstructionConcrete Construction
S A ReddiS A ReddiDyDy. MD (. MD (RetdRetd.) Gammon India Ltd..) Gammon India Ltd.
Mass Concrete PoursMass Concrete Pours
Typical Structures With Mass Typical Structures With Mass Concrete PoursConcrete Pours
General Overview
Definitions & Standards, Thermal CrackingTemperature RiseTemperature & Stress PredictionFactors Affecting Temperature RiseCement, Aggregate, Ambient Temp, SCMs, Placement TechniquesPost-Placement TechniquesEmbedded Pipe CoolingFormwork InsulationThermal Expansion Reinforcement
Mass Concrete Defined“Any volume of concrete with dimensions large enough to require that measures be taken to cope with the generation of heat from hydration of the cement and attendant volume change to minimizecracking.”(ACI Manual of Concrete Practice)
Mass Concrete PrinciplesWhen dimensions are > 1m
Cement Hydration is an exothermic process, leads to a rise in temp at the core of large pours; If the surface temperature deviates greatly from that of the core, thermal cracking will developCodes require a temp differential of less than 20 deg C - surface to the core temperature rise should be considered
�Apply to large dams, Mass foundations, bridge piers, thick slabs, nuclear plants, structural columns, etc…
Thermal Cracking
Cement hydration produces a rise in internaltemperature. The outer surface cools faster than the core of the section.By thermal expansion/contraction, the temp differential induces tensile stresses at the surfaceStresses > Tensile Strength => Thermal Cracking
Temperature Rise
� Temperature rise varies by many parameters:� Cement composition, fineness, and content� Aggregate content and CTE (Coeff. of Thermal
Expansion)� Section geometry� Placement & ambient temperatures (Mass)� Most temp rise occurs in first 1-3 days after
placement. For thick sections, cooling to ambient temps may take years.
For thick sections, cooling to ambienttemps may take years.
Factors Affecting Temp. Rise�Cement with a lower fineness will slow
hydration, and reduce temperature rise� Mass Concrete mixes should contain as
low cement content as possible to achieve the desired strength This lowers the heat of hydration and temp rise
� Coarse Aggregate should be have an MSA of 150mm if possible.
� A higher coarse aggregate content (70-85%) can be used to lower the cement content, reducing temp rise
Factors Affecting Temp. Rise� Fly Ash, and Slag can greatly reduce
heat of hydration � Pozzolans such as FA (class F is best >
slower hydration) and Slag will produce between 15-50% of the heat of Ordinary Portland Cement.
� Highly reactive SCMs such as Silica Fume and Metakaolin do not substantially lower the heat of hydrationLower cement content + pozzolans greatly reduces temperature rise!
Factors Affecting Temp. Rise� Placement Temperature
� Pouring at lower temperatures will reduce the thermalstresses in the section.
� Slows hydration > lowers heat of hydration, lowers temperature differential between the core and theouter surface. Lower ambient temps produce less temperature rise!Lower volume:surface ratio produce less temprise!
� W/C has a large effect on temperature rise.� Most Mass Concrete mixes have a 0-50mm slump.
Placement TechniquesCool aggregate by flushing with cold water to reduce placement temperatures.
� Replacing mix water with flaked/crushed ice can greatly reduce the temperature of the mix.
� Cooling the aggregate and use ice in mix water can reduce placement temperatures up to 12 C
� For heat transfer calculations, all components are changed to water equivalents.Core sample from a large column with thermal cracks.
Placement Techniques
� Flushing the mix is Liquid Nitrogen can reduce temps.
Post-Placement Techniques
� Two schools of thought exist on post-placement techniques to reduce thermal cracking:1) Cool the core of the concrete to reduce the temperature differential.2) Insulate the outer surface to reduce the temperature differential.
Post-Cooling
� Post-Cooling utilizes cold water flowing through pipes embedded into the concreteThis helps to transfer heat from the
core, and reduce the temperature differential.
Post-Cooling
Example of embedded pipe gridArea cooled by one pipe-Pipe spacing is judged by heat transfer principles. Must be spaced in a manner which achieved the desired temperaturedifferential
Post-Cooling
� Instrumentation is used to monitor temperature, to determine flow-rates through cooling pipesSteel pipes are the most effective at extracting heat from the core
Insulation After Placement�Method to reduce the temp gradient� By limiting the heat loss from surface,
the difference in temperature between the surface and the core is minimized
� Removing formwork too soon can cause “thermal shock” to the surface, and extensive cracking will occur
� Metal formwork is very conductive to heat, so additional insulation needed to limit heat loss
� 25mm wood ~500mm of addl concrete
Expansion Reinforcement
� Expansion Reinforcement can be used to lessen thermal cracking.
� Must be designed in addition to loads placed onto the structure.� Expansion reinforcement distributes thermal stresses to minimize crack widths.� Expansion reinforcement is impractical for very large pours.
Expansion Reinforcement �General procedure for design.
� Determine maximum temperature gradient� Determine section restraint characteristics r)� Determine physical properties of the concrete:� CTE, E, Tensile Strength� Determine the allowable crack width:� Must consider durability and permeability� Determine area of steel required to limit
cracking
Large Volume PoursLarge Volume PoursNotable Indian CasesNotable Indian Cases
Foundation raft for 500 MW Fast Breeder Foundation raft for 500 MW Fast Breeder Nuclear Reactor at Nuclear Reactor at KalpakkamKalpakkam near near Chennai : Maximum single pour was Chennai : Maximum single pour was 5500 m5500 m33
Many rafts for chimneys, storage silos Many rafts for chimneys, storage silos with single pour of more than 2000 mwith single pour of more than 2000 m33
Large Volume PoursLarge Volume PoursSpecial Attention RequiredSpecial Attention Required
Concrete Mix proportionConcrete Mix proportionMineral AdmixturesMineral AdmixturesConcrete supply Concrete supply Casting sequenceCasting sequenceCold jointsCold jointsPlastic settlementPlastic settlementHeat of hydration Heat of hydration Early age thermal cracking Early age thermal cracking
Large Volume Pours :BenefitsLarge Volume Pours :Benefits
Savings in cost and time resulting from Savings in cost and time resulting from the reduction in the number of jointsthe reduction in the number of jointsJoints expensive to form, requiring stop Joints expensive to form, requiring stop ends, careful preparation of the concrete ends, careful preparation of the concrete surface when new concrete is castsurface when new concrete is castConstruction joints Delays construction Construction joints Delays construction Labor, material cost in making the joints Labor, material cost in making the joints Practical difficulties in forming joints Practical difficulties in forming joints Difficulties in preparing concrete surface Difficulties in preparing concrete surface
Large Volume PoursLarge Volume PoursFormation of Sound Construction Joints ImpossibleFormation of Sound Construction Joints Impossible
Typically in heavily reinforced foundations Typically in heavily reinforced foundations to core to core –– shaft tower blocks, formation of shaft tower blocks, formation of sound construction joints is virtually sound construction joints is virtually impossible because of very congested impossible because of very congested reinforcementsreinforcementsSimilar conditions are often found in large Similar conditions are often found in large sections such as bridge decks, where the sections such as bridge decks, where the position of void formers, stressing cables, position of void formers, stressing cables, ducts etc render the installation of ducts etc render the installation of construction joints extremely difficult construction joints extremely difficult
Large Volume PoursLarge Volume PoursConcrete Mix ProportioningConcrete Mix Proportioning
Requirements for strength and Requirements for strength and workability workability Thermal characteristics minimize risk of Thermal characteristics minimize risk of thermal crackingthermal crackingDelayed stiffening time to avoid cold Delayed stiffening time to avoid cold jointsjointsHeat evolution Heat evolution Thermal expansion coefficientThermal expansion coefficientTensile strain capacity Tensile strain capacity
Large Volume PoursLarge Volume PoursComposite CementsComposite Cements
Combinations of OPC with either PFA or Combinations of OPC with either PFA or GGBS hydrate at slower rate than OPC GGBS hydrate at slower rate than OPC and produce a lower temperature rise. and produce a lower temperature rise. This applies to both PPC, PSC and blends This applies to both PPC, PSC and blends of OPC and PFA,GGBS produced in a of OPC and PFA,GGBS produced in a batching plantbatching plantThe level of PFA in such blends is up to The level of PFA in such blends is up to 40%; up to 75% if GGBS is used. 40%; up to 75% if GGBS is used.
Large Volume PoursLarge Volume PoursMeasuring Temperature Rise in Measuring Temperature Rise in ConcConcCast an insulated One mCast an insulated One m33 block using block using suitable formwork available at site and suitable formwork available at site and measure the temp. rise at the centre measure the temp. rise at the centre using thermo coupleusing thermo coupleA simple plywood form lined with 50mm A simple plywood form lined with 50mm thick expanded polystyrene is adequate thick expanded polystyrene is adequate to provide comparative results to provide comparative results
Cost Reduction By Use Cost Reduction By Use Of Fly AshOf Fly Ash
Improvement In Properties Of Improvement In Properties Of ConcreteConcrete
Fly ash / Fly Ash In ConcreteFly ash / Fly Ash In ConcretePulverized Fuel Ash (Fly Ash) or Fly Ash is Pulverized Fuel Ash (Fly Ash) or Fly Ash is a material produced in thermal power a material produced in thermal power stations as coal is burnt. It is stations as coal is burnt. It is pozzolanicpozzolanic, , combines with free lime in cement to combines with free lime in cement to form calcium silicate, aluminium form calcium silicate, aluminium hydrates; hydrates; categorisedcategorised as Mineral as Mineral Admixture in IS 456 : 2000Admixture in IS 456 : 2000Fly Ash conforming to Grade 1 of IS 3812 Fly Ash conforming to Grade 1 of IS 3812 may be used as part replacement of OPC may be used as part replacement of OPC provided uniform blending is ensured; provided uniform blending is ensured;
Mineral Admixtures Mineral Admixtures Fly ashFly ash
India produces about 100 million India produces about 100 million tonnes, disposal is a problem; can be tonnes, disposal is a problem; can be partly used as mineral admixtures in partly used as mineral admixtures in concrete of all grades concrete of all grades Special applicationsSpecial applications
High Strength ConcreteHigh Strength ConcreteRoller Compacted concreteRoller Compacted concreteEmbankment fillsEmbankment fillsReinforced earth fills Reinforced earth fills FlyashFlyash bricks bricks
Mineral Admixtures Mineral Admixtures Processed Processed Fly AshFly Ash
Power station ash does not always meet Power station ash does not always meet the requirement; only some ESP streams the requirement; only some ESP streams qualify; remaining ash needs processing qualify; remaining ash needs processing before use before use As per EN 450 As per EN 450 ‘‘fly ash may before its use fly ash may before its use be subject to processing by classification be subject to processing by classification or selection to increase its fineness and or selection to increase its fineness and to improve other properties to improve other properties
Processed Fly Ash FactoryProcessed Fly Ash Factory
Dirk India ,a German Company, has Dirk India ,a German Company, has installed an Unit in installed an Unit in NashikNashik, with capacity , with capacity 1000 TPD, (three classification plants)1000 TPD, (three classification plants)There are a few agencies supplying fly There are a few agencies supplying fly ash, but they merely collect fly ash from ash, but they merely collect fly ash from power stations and supply in bags; the power stations and supply in bags; the product may or may not conform to IS product may or may not conform to IS SpecificationSpecification
Use of PFA From Use of PFA From Power StationPower Station
Electrostatic Electrostatic Precipitators in power Precipitators in power station discharge station discharge usable PFA in separate usable PFA in separate streams streams
Collected and fed Collected and fed into processing units into processing units for classification as fly for classification as fly ash suitable for use ash suitable for use with concretewith concrete
Typical Fly Ash Typical Fly Ash Processing UnitProcessing UnitRaw Fly Ash fed intoRaw Fly Ash fed intoa classifiera classifierThe coarser particlesThe coarser particlesmove down in the move down in the classifier, discarded classifier, discarded Fine particles Fine particles collectedcollected
through a cyclone, through a cyclone, shown on rightshown on right
Use of Fly AshUse of Fly AshReady Mix Concrete PlantsReady Mix Concrete Plants
All ready mix concrete plants have All ready mix concrete plants have started using varying percentages of started using varying percentages of cement replacement by fly ash, with or cement replacement by fly ash, with or without the knowledge of the Purchasers without the knowledge of the Purchasers Indiscriminate, uncontrolled use of non Indiscriminate, uncontrolled use of non processed fly ash by some RMC plants processed fly ash by some RMC plants have resulted in quality deficiencies have resulted in quality deficiencies RMC plants should declare percentage RMC plants should declare percentage replacement while supplying concrete replacement while supplying concrete
Mineral Admixtures Mineral Admixtures Blended cements Vs site mixingBlended cements Vs site mixing
As per IS 456 there is no distinction on As per IS 456 there is no distinction on technical grounds between blended technical grounds between blended cement and site blending. Either method cement and site blending. Either method may be selected.may be selected.Advantages of site blending in concreteAdvantages of site blending in concreteoo Increased flexibility in proportioningIncreased flexibility in proportioningoo CostCost--effective; savings up to 20 % compared effective; savings up to 20 % compared
to blended cement to blended cement oo Effective monitoring of quality and Effective monitoring of quality and
percentage of Mineral Admixtures percentage of Mineral Admixtures
Mineral Admixtures Mineral Admixtures Blended cements Vs site mixingBlended cements Vs site mixing
No manufactured blended cement will No manufactured blended cement will be able to satisfy all specifications or be able to satisfy all specifications or uses. Proportions are set by the uses. Proportions are set by the manufacturers and data on percentage manufacturers and data on percentage blended not available to the users blended not available to the users Because of limited choice of Because of limited choice of proportions in standard blended proportions in standard blended cements, their properties may not lead cements, their properties may not lead to optimum concrete properties for to optimum concrete properties for different purposes.different purposes.
Mineral Admixtures Mineral Admixtures Advantages of Site Mixing Advantages of Site Mixing
Vary proportions to achieve optimum Vary proportions to achieve optimum concrete properties & economicalconcrete properties & economicalSavings in transport Savings in transport vsvs moving Fly Ash moving Fly Ash to factory for blending & delivering PPC to factory for blending & delivering PPC Suitable where different percentages of Suitable where different percentages of Fly ash are specified; consistent strength Fly ash are specified; consistent strength achieved with low standard deviation 2 achieved with low standard deviation 2 MPaMPa with site blendingwith site blendingSuppliers charge same price for OPC , Suppliers charge same price for OPC , PPC; much cheaper if OPC + Fly Ash is PPC; much cheaper if OPC + Fly Ash is used used
Benefits of Fly Ash in ConcreteBenefits of Fly Ash in Concrete
Improved WorkabilityImproved WorkabilityLow bleedingLow bleedingLow heat of hydrationLow heat of hydrationImproved durabilityImproved durabilitySulphateSulphate resistance resistance Reduced risk of Alkali Silica ReactionReduced risk of Alkali Silica ReactionReduced Construction CostsReduced Construction Costs
Fly Ash Status in IndiaFly Ash Status in India
Uncertain quality, needs processingUncertain quality, needs processingSeparate processing facility requiredSeparate processing facility requiredElectricity BoardElectricity Board’’s attitude towards s attitude towards disposaldisposalCodes, Specifications Codes, Specifications vsvs RealityRealityGovt. policies, attitudes, excise duty Govt. policies, attitudes, excise duty R&D : Processing RequirementsR&D : Processing RequirementsRole of Cement ProducersRole of Cement ProducersRole of End Users Role of End Users
Perception About Fly AshPerception About Fly Ash
Fly ash should not be treated as waste Fly ash should not be treated as waste product, but as useful byproduct, but as useful by--product from product from Thermal Power StationThermal Power StationFly Ash is often an essential ingredient Fly Ash is often an essential ingredient for durability of concretefor durability of concreteAs part replacement of cement, Fly Ash As part replacement of cement, Fly Ash assists in conserving nonassists in conserving non--renewable renewable energy sources energy sources
Fly Ash Fly Ash –– What is the Problem ?What is the Problem ?
Power stations priority : High Thermal Power stations priority : High Thermal efficiency, emissions secondaryefficiency, emissions secondaryThey produce They produce Fly ashFly ash, a, a waste materialwaste materialhaving variable carbon content, color, having variable carbon content, color, fineness and density, impurities fineness and density, impurities Potential users require Fly Ash of uniform Potential users require Fly Ash of uniform quality and fineness, free of impuritiesquality and fineness, free of impuritiesFly Ash Processing absent in India, Fly Ash Processing absent in India, except at except at NashikNashik and one or two other and one or two other centrescentres
Fly Ash Property VariationsFly Ash Property Variations
Quality of CoalQuality of CoalCoal milling operationsCoal milling operationsBoiler loadingBoiler loadingSupplementary fuel usedSupplementary fuel usedOperational influences Operational influences
Fly Ash From Power StationsFly Ash From Power Stations
Fit and operate Fit and operate ESPsESPsESPsESPs arranged in seriesarranged in seriesFiner particles progressively removedFiner particles progressively removedUse grading facility of Use grading facility of ESPsESPsSeparately store raw Fly Ash outputSeparately store raw Fly Ash outputClassify raw Fly Ash for complianceClassify raw Fly Ash for complianceOffer classified Fly Ash for sale Offer classified Fly Ash for sale
Process Plant for Fly AshProcess Plant for Fly Ash
Transport fly ash from PSTransport fly ash from PSTransfer to raw material silosTransfer to raw material silosFeed fly ash to production unitsFeed fly ash to production unitsProcess by air classification unitsProcess by air classification unitsTransfer to Fly Ash storage silosTransfer to Fly Ash storage silosDispatch through tankersDispatch through tankers
Concrete Made with Fly AshConcrete Made with Fly AshImpact On StrengthImpact On Strength
Concrete made with fly ash will be Concrete made with fly ash will be slightly lower in strength slightly lower in strength uptoupto 28 days 28 days than OPC concrete than OPC concrete Equal strength at 28 days, substantially Equal strength at 28 days, substantially higher strength within a yearhigher strength within a year’’s times timeIn concrete without In concrete without flyashflyash, free lime , free lime
remains intact and over time would be remains intact and over time would be susceptible to the effects of weathering susceptible to the effects of weathering and loss of strength, durability.and loss of strength, durability.
Strength gain properties of Strength gain properties of pfapfaStrength Development with TimeStrength Development with Time
Concrete With Fly Ash AdditionConcrete With Fly Ash AdditionImproved WorkabilityImproved Workability
Fly Ash Increases Fly Ash Increases ConcConc WorkabilityWorkability
Fly ash produces more cementitious Fly ash produces more cementitious paste; has a lower unit weight; paste; has a lower unit weight; contributes roughly 30% more volume of contributes roughly 30% more volume of cementitious material per kg of cement. cementitious material per kg of cement. The greater percentage of fly ash in the The greater percentage of fly ash in the paste, the aggregates are better paste, the aggregates are better lubricated and the concrete flows betterlubricated and the concrete flows betterHowever, IS 456 limits Fly Ash content to However, IS 456 limits Fly Ash content to not more than 35% for normal Concrete; not more than 35% for normal Concrete; can go can go uptoupto 50% for Self Compacting 50% for Self Compacting ConcreteConcrete
Fly Ash Reduces Water DemandFly Ash Reduces Water Demand
Fly ash reduces water needed to produce Fly ash reduces water needed to produce a given slump. The spherical shape of fly a given slump. The spherical shape of fly ash particles and its dispersive ability ash particles and its dispersive ability provide waterprovide water--reducing characteristics reducing characteristics similar to a water reducing admixturesimilar to a water reducing admixtureWater demand of a concrete mix with fly Water demand of a concrete mix with fly ash is reduced by 2% to 10%, depending ash is reduced by 2% to 10%, depending on a number of factors including the on a number of factors including the amount used and class of fly ash.amount used and class of fly ash.
Fly Ash Reduces Sand ContentFly Ash Reduces Sand ContentFly ash reduces the sand needed in the Fly ash reduces the sand needed in the mix to produce workabilitymix to produce workabilityIt creates more paste, and by dispersive It creates more paste, and by dispersive action makes the paste more action makes the paste more ““slipperyslippery””Sand has a much greater surface area Sand has a much greater surface area than larger aggregates & therefore than larger aggregates & therefore requires more pasterequires more pasteBy reducing sand, the paste available can By reducing sand, the paste available can more efficiently coat the surface area of more efficiently coat the surface area of the aggregatesthe aggregates
Fly Ash Improves Corrosion ProtectionFly Ash Improves Corrosion Protection
By decreasing concrete permeability, fly By decreasing concrete permeability, fly ash can reduce the rate of ingress of ash can reduce the rate of ingress of water, corrosive chemicals and oxygen water, corrosive chemicals and oxygen ——thus protecting steel reinforcement from thus protecting steel reinforcement from corrosion and its subsequent expansive corrosion and its subsequent expansive resultresultFly ash concrete is less permeable Fly ash concrete is less permeable because fly ash reduces the amount of because fly ash reduces the amount of water needed to produce a given slumpwater needed to produce a given slump
Fly Ash Reduces Heat of Hydration Fly Ash Reduces Heat of Hydration in Concretein Concrete
During hydration of cement, heat is During hydration of cement, heat is generated quickly, causing concrete generated quickly, causing concrete temperature to risetemperature to riseThis rapid heat gain increases the This rapid heat gain increases the chances of thermal cracking, leading to chances of thermal cracking, leading to reduced concrete strength and durabilityreduced concrete strength and durabilityFly ash generates only 15 Fly ash generates only 15 -- 35 % as 35 % as much heat compared to cement at early much heat compared to cement at early ages. Replacing part of cement with fly ages. Replacing part of cement with fly ash reduces the damaging effects of ash reduces the damaging effects of thermal crackingthermal cracking
Use Of Fly Ash as per IS 456Use Of Fly Ash as per IS 456
IS provides for use of fly ash (pulverised IS provides for use of fly ash (pulverised fuel ash) conforming to Grade 1 of IS fuel ash) conforming to Grade 1 of IS 3812 as part replacement of Ordinary 3812 as part replacement of Ordinary Portland Cement provided uniform Portland Cement provided uniform blending with cement is ensured blending with cement is ensured Please note that fly ash may be mixed Please note that fly ash may be mixed with OPC only for making concretewith OPC only for making concreteSome unscrupulous RMC plants / Some unscrupulous RMC plants / contractors mix fly ash with PPC contractors mix fly ash with PPC –– not not allowed in the code allowed in the code
Use Of Fly Ash as per IS 456 Use Of Fly Ash as per IS 456 Grades Of ConcreteGrades Of Concrete
IS 456 , Table 2 specifies three groups of IS 456 , Table 2 specifies three groups of concrete: concrete:
Ordinary Concrete Ordinary Concrete –– M10, M15, M20M10, M15, M20Standard Concrete Standard Concrete –– M25 to M55M25 to M55High Strength Concrete High Strength Concrete –– M60 to M60 to
M80M80Fly ash may be used for all groups and Fly ash may be used for all groups and grades of concrete; percentage grades of concrete; percentage replacement may vary replacement may vary
Use Of Fly Ash as per IS 456Use Of Fly Ash as per IS 456Percentage ReplacementPercentage Replacement
For Ordinary and Standard Concrete, fly For Ordinary and Standard Concrete, fly ash may replace concrete by ash may replace concrete by uptoupto 35% 35% based on trial mixes based on trial mixes For High Strength Concrete M60 and For High Strength Concrete M60 and above , percentage replacement may be above , percentage replacement may be increasedincreasedFor Self Compacting Concrete, For Self Compacting Concrete, percentage may go percentage may go uptoupto 5050For concrete roads, desirable to use fly For concrete roads, desirable to use fly ash ash uptoupto 50% replacement 50% replacement
Use Of Fly Ash as per IS 456Use Of Fly Ash as per IS 456Interpretation Of Fly Ash QuantitiesInterpretation Of Fly Ash QuantitiesTable 5 specifies minimum cement Table 5 specifies minimum cement content for different exposures ; building content for different exposures ; building foundations fall under Severe Exposure, foundations fall under Severe Exposure, with minimum 320 kg cementitious with minimum 320 kg cementitious material per cubic metre of material per cubic metre of concconcIf for example 25% fly ash replaces If for example 25% fly ash replaces cement, mix will consist of 240kg cement cement, mix will consist of 240kg cement + 80kg fly ash+ 80kg fly ashFly ash % is based on total cementitious Fly ash % is based on total cementitious materials used and not on cement onlymaterials used and not on cement only
Economics of ConcreteEconomics of ConcreteSite Mixed Fly Ash Site Mixed Fly Ash vsvs PPCPPC
Assume 25% replacement by fly ash and Assume 25% replacement by fly ash and 320kg cementitious material. Cost of 320kg cementitious material. Cost of materials: materials:
OPC 240 kg at say OPC 240 kg at say RsRs 300 per bag: 300 per bag: RsRs 14401440
Fly Ash 80 kg at Fly Ash 80 kg at RsRs 1000/t : 1000/t : RsRs 8080
Total cost cementitious material : Total cost cementitious material : RsRs 1520 1520 In case PPC is used instead of site In case PPC is used instead of site
Use Of Fly Ash as per IS 456Use Of Fly Ash as per IS 456Formwork Stripping TimeFormwork Stripping Time
The stripping time specified in clause The stripping time specified in clause 11.3 is applicable where OPC is used 11.3 is applicable where OPC is used For other cements , stripping time may For other cements , stripping time may be suitably modified be suitably modified For PPC or where fly ash is blended at For PPC or where fly ash is blended at site, due to slow setting time in the early site, due to slow setting time in the early ages, stripping time needs to be ages, stripping time needs to be increased by about 50% increased by about 50%
Use Of Fly Ash as per IS 456Use Of Fly Ash as per IS 456CuringCuring
Exposed surfaces of concrete shall be Exposed surfaces of concrete shall be kept continuously in a damp or wet kept continuously in a damp or wet condition by condition by pondingponding or by covering with or by covering with a layer of sacking, canvas, a layer of sacking, canvas, hessianhessian and and constantly kept wet for at least 7 days in constantly kept wet for at least 7 days in case of OPC case of OPC At least 10 days where mineral At least 10 days where mineral admixtures or blended cements are usedadmixtures or blended cements are usedApproved curing compounds may be used Approved curing compounds may be used in both cases; one time application in both cases; one time application
Portland Portland PozzolonaPozzolona Cement Cement (Fly Ash Based) as per IS 1489 Part 1(Fly Ash Based) as per IS 1489 Part 1The strength properties of PPC at 28 days The strength properties of PPC at 28 days are similar to OPC 33 Grade; 28 day are similar to OPC 33 Grade; 28 day strength of cement is specified as 33 strength of cement is specified as 33 mPamPaOPC is available in 3 strength grades OPC is available in 3 strength grades ––33, 43, 53 33, 43, 53 mPamPa at 28 daysat 28 daysThus PPC can be used only for lower Thus PPC can be used only for lower grades of concrete such as M20, M30 etcgrades of concrete such as M20, M30 etcFor higher Grades only OPC + fly ash site For higher Grades only OPC + fly ash site mixed is mixed is suiteablesuiteable
Portland Portland PozzolonaPozzolona Cement Cement Strength Gradation Attempts By BISStrength Gradation Attempts By BIS
For several years, the Bureau of Indian For several years, the Bureau of Indian Standards have proposed 3 Grades of Standards have proposed 3 Grades of PPC , namely 33, 43, 53 similar to OPC PPC , namely 33, 43, 53 similar to OPC Some cement manufacturers have agreed Some cement manufacturers have agreed for the gradation for the gradation Some others who do not have the Some others who do not have the capability to produce higher Grades of capability to produce higher Grades of PPC have been opposing the move; the PPC have been opposing the move; the stalemate continuesstalemate continuesAs on date (2009) PPC available only in As on date (2009) PPC available only in
Portland Portland PozzolonaPozzolona CementCementAs per European (As per European (EN)StandardsEN)StandardsEN 197 EN 197 –– 1: 2000 is the reference 1: 2000 is the reference documentdocumentIn Europe PPC is available in 3 Grades In Europe PPC is available in 3 Grades vizviz32.5, 42.5 and 52.5 ( the numbers 32.5, 42.5 and 52.5 ( the numbers indicate 28 day strength of cement indicate 28 day strength of cement The combination of fly ash may vary : The combination of fly ash may vary :
Option 1 : 6 to 20% fly ashOption 1 : 6 to 20% fly ashOption 2 : 21 to 35% fly ashOption 2 : 21 to 35% fly ash
Current Status Of Use of PPC In Current Status Of Use of PPC In IndiaIndia
Until the relevant BIS Codes are Until the relevant BIS Codes are revised, PPC can be used only for revised, PPC can be used only for lower grades of Concrete lower grades of Concrete For higher Grades only processed fly For higher Grades only processed fly ash may be blended with OPC for ash may be blended with OPC for manufacture of concretemanufacture of concrete
Batching PlantBatching PlantSeparate Silo For Fly AshSeparate Silo For Fly Ash
Use Of Fly Ash as per IS 456Use Of Fly Ash as per IS 456
Clause 5.2.1.1 Clause 5.2.1.1 –– fly ash ( Pulverized fuel fly ash ( Pulverized fuel ash ) ash ) Fly ash conforming to Grade 1 of IS 3812 Fly ash conforming to Grade 1 of IS 3812 may be used as part replacement of may be used as part replacement of Ordinary Portland Cement provided Ordinary Portland Cement provided uniform blending with cement is ensured uniform blending with cement is ensured Uniform blending is achieved when Uniform blending is achieved when concrete is prepared in a batching plant; concrete is prepared in a batching plant; separate cement silos are required for separate cement silos are required for OPC and fly ash OPC and fly ash
Site Mixing Fly AshSite Mixing Fly AshBandraBandra Worli Sea LinkWorli Sea Link
Contract specified minimum 400 kg Contract specified minimum 400 kg cementitious material per cubic metre of cementitious material per cubic metre of concrete concrete Even for M60 Even for M60 GrGr Concrete the contractors Concrete the contractors have designed a mix with site blending of have designed a mix with site blending of fly ash in concrete, using only 320 kg OPC fly ash in concrete, using only 320 kg OPC plus 80 kg fly ash; project completed plus 80 kg fly ash; project completed successfully successfully
Characteristic strength 60 MpaTarget strength 74 Mpa
Cement 320 kg Micro silica 45 kg
Fly ash 80 kgw/c ratio 0.31Admixtures 10 kgSlump 120 mm
28 day strength 75 Mpa
BandraBandra Worli Sea linkWorli Sea link
Self Compacting ConcreteSelf Compacting ConcreteCement ContentCement Content
Cement content should be minimized; Cement content should be minimized; powder content composed of mineral powder content composed of mineral admixtures such as flyadmixtures such as fly--ash, GGBS etc. ash, GGBS etc. SCC in Nuclear Power Projects in India, SCC in Nuclear Power Projects in India, cement limited to 250 Kg/mcement limited to 250 Kg/m3 3 ; and fly; and fly--ash also 250 Kg/, mash also 250 Kg/, m33 for concretes up to for concretes up to 50 50 MPaMPaFor 80 For 80 MPaMPa concrete, mix successfully concrete, mix successfully designed with cement content not designed with cement content not exceeding 350 Kg/mexceeding 350 Kg/m33
Palais Royale Tower, MumbaiPalais Royale Tower, MumbaiBrief Description Brief Description
Height : 320m Height : 320m –– Tallest in India (2008)Tallest in India (2008)Foundations : Raft, Foundations : Raft, uptoupto 3.5m thick, Grade M403.5m thick, Grade M40-- Basements, Superstructure Basements, Superstructure -- Columns : SCC M80, M60 Columns : SCC M80, M60 -- Slabs, Beams : M60 Concrete Slabs, Beams : M60 Concrete -- PrePre--tensioned flat slabs at lower levels tensioned flat slabs at lower levels Basement + 80m height utilized for car parks, Basement + 80m height utilized for car parks, sports facilities, Building Management Systems sports facilities, Building Management Systems (BMS)(BMS)Precautions against Fire & Fire Fighting Precautions against Fire & Fire Fighting measures measures
Palais Royale Tower, MumbaiPalais Royale Tower, MumbaiMaterials for SCCMaterials for SCC
OPC 53 Grade from selected factoryOPC 53 Grade from selected factoryProcessed flyProcessed fly--ash from ash from NashikNashikSilica Fume Silica Fume -- importedimportedPC based super plasticizer PC based super plasticizer –– importedimportedCoarse aggregates from local quarriesCoarse aggregates from local quarriesFine aggregates from GujaratFine aggregates from GujaratWater from local sourcesWater from local sources
Palais Royale Tower Palais Royale Tower 80 80 MPaMPa SCC SCC
Cement : 350 Cement : 350 -- 400 400 kg kg Silica fume : 10 % Silica fume : 10 % Water : 135 Water : 135 litreslitresAggregates : Local Aggregates : Local PC based admix : 0.8 PC based admix : 0.8 –– 1.0 %1.0 %Viscosity Modifier : 0.2 % Viscosity Modifier : 0.2 % Concrete produced at site batch Concrete produced at site batch plant plant
