cement production read that

7/25/2019 Cement Production Read That

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PORTLAND CEMENTPORTLAND CEMENT


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Portland CementPortland Cement Gypsum+Portland Cement Gypsum+Portland CementClinker (pulverizing)Clinker (pulverizing)

Portland Cement Clinker Calcareous &Portland Cement Clinker Calcareous &

Clayey Materials (burning)Clayey Materials (burning)

Paste P.C. + WaterPaste P.C. + Water

Mortar P.C. + Water + SandMortar P.C. + Water + Sand

Concrete P.C. + Water + Sand + GravelConcrete P.C. + Water + Sand + Gravel


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RAW MATERIALS OF P.C.RAW MATERIALS OF P.C.

1)1) Calcareous Rocks (CaCOCalcareous Rocks (CaCO33 >> 75%)75%) LimestoneLimestone MarlMarl ChalkChalk

2)2) Argillocalcareous Rocks (40%Argillocalcareous Rocks (40%


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3)3) Argillaceous Rocks (CaCOArgillaceous Rocks (CaCO33


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CLINKER GYPSUM


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PRODUCTION STEPSPRODUCTION STEPS

1)1) Raw materials are crushed, screemed &Raw materials are crushed, screemed &stockpiled.stockpiled.

2)2) Raw materials are mixed with definiteRaw materials are mixed with definiteproportions to obtain raw mix. They areproportions to obtain raw mix. They are

mixed either dry (dry mixing) or by water (wetmixed either dry (dry mixing) or by water (wetmixing).mixing).3)3) Prepared raw mix is fed into the rotary kiln.Prepared raw mix is fed into the rotary kiln.4)4)

As the materials pass through the kiln theirAs the materials pass through the kiln theirtemperature is rised upto 1300temperature is rised upto 1300--16001600 C. TheC. Theprocess of heating is named as burning. Theprocess of heating is named as burning. Theoutput is known as clinker which is 0.15output is known as clinker which is 0.15--55

cm in diameter.cm in diameter.


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5)5) Clinker is cooled & stored.Clinker is cooled & stored.

6)6) Clinker is ground with gypsum (3Clinker is ground with gypsum (3--6%) to6%) toadjust setting time.adjust setting time.

7)7) ac ng mar e ng.ac ng mar e ng.


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REACTIONS IN THE KILNREACTIONS IN THE KILN ~~100100CC free water evaporates. free water evaporates.

~~150150--350C350C loosely bound water is lost fromloosely bound water is lost fromclay.clay.

~~ -- claySiOclaySiO22&Al&Al22OO33

~~600600CCdecomposition of MgCOdecomposition of MgCO33MgO&COMgO&CO22

(evaporates)(evaporates)

~~900900CCdecomposition of CaCOdecomposition of CaCO33CaO&COCaO&CO22(evaporates)(evaporates)


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~~12501250--12801280CCliquid formation & start ofliquid formation & start ofcompound formation.compound formation.

~~12801280CCclinkering begins.clinkering begins.

~~14001400--15001500CCclinkeringclinkering

~~100100CCclinker leaves the kiln & falls into aclinker leaves the kiln & falls into acooler.cooler.

Sometimes the burning process of raw materialsSometimes the burning process of raw materialsis performed in two stages: preheating uptois performed in two stages: preheating upto900900C & rotary kilnC & rotary kiln

CHEMICAL COMPOSITIONCHEMICAL COMPOSITION


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CHEMICAL COMPOSITIONCHEMICAL COMPOSITIONOF P.C.OF P.C.

Portland cement is composed of fourPortland cement is composed of fourmajor oxides (CaO, SiOmajor oxides (CaO, SiO22, Al, Al22OO33, Fe, Fe22OO3390%) & some minor oxides. Minor refers90%) & some minor oxides. Minor refers

. .


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Oxide Common Name Abbreviation Approx. Amount (%)

CaO Lime C 60-67

SiO2 Silica S 17-25

Al2O3 Alumina A 3-8

Fe2O3 Iron-oxide F 0.5-6

MgO Magnesia M 0.1-4

Na O Soda N0.2-1.3

K2O Potassa K

SO3 Sulfuric Anhydride

1-3

CaOCaOlimestonelimestone SiOSiO22--AlAl22OO33ClayClay

FeFe22OO33Impurity in ClaysImpurity in Clays

SOSO33from gypsumnot from the clinkerfrom gypsumnot from the clinker

S


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The amount of oxides in a P.C. Depend on theThe amount of oxides in a P.C. Depend on theproportioning of the raw materials and how well theproportioning of the raw materials and how well theburning is done in the kiln. The chemical composition isburning is done in the kiln. The chemical composition isfound by chemical analysis.found by chemical analysis.

A typical analysis of O.P.C.A typical analysis of O.P.C.

Insoluble residue=0.2Insoluble residue=0.2 Loss on ignition=1.4Loss on ignition=1.4

C 63.6

S 20.7

F 2.4

2.1

M 2.6

N 0.1

K 0.9

Free C 1.4

Total 99.8


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CaO (C), SiOCaO (C), SiO22 (S), Al(S), Al22OO33 (A) & Fe(A) & Fe22OO33 are theare themajor oxides that interact in the kiln & form themajor oxides that interact in the kiln & form themajor compounds.major compounds.

The proportions of these oxides determine theThe proportions of these oxides determine theproportions of the compounds which affect theproportions of the compounds which affect the

SOSO33comes largely from gypsumcomes largely from gypsum

P.C. alone sets quickly so some gypsum isP.C. alone sets quickly so some gypsum is

ground with clinker to retard the setting time.ground with clinker to retard the setting time.


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If too much gypsum is included it leads toIf too much gypsum is included it leads todistruptive expansions of the hardeneddistruptive expansions of the hardened

paste or concrete.paste or concrete.

ASTM C 150ASTM C 150 SO SO33 3% in O.P.C. 3% in O.P.C.

MgO+HMgO+H2OMHOMH

C+HCH volume expansion & causeC+HCH volume expansion & cause

cracking.cracking. ASTM C 150 MASTM C 150 M


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Alkalies (NaAlkalies (Na22O & KO & K22O) may cause someO) may cause somedificulties if the cement is used withdificulties if the cement is used with

certain types of reactive aggregates incertain types of reactive aggregates inmaking concrete. The alkalies in the formmaking concrete. The alkalies in the formof alkaline hydroxides can react with theof alkaline hydroxides can react with the

reactive silica of the aggregate & resultingreactive silica of the aggregate & resultingn vo ume expans on a er ar en ng. sn vo ume expans on a er ar en ng. sprocess may take years.process may take years.

NaNa22O & KO & K22O 0.6%O 0.6%


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Insoluble Residue:Insoluble Residue: is that fraction of cementis that fraction of cementwhich is insoluble in HCl. It comes mainly fromwhich is insoluble in HCl. It comes mainly from

the silica which has not reacted to formthe silica which has not reacted to formcompounds during the burning process in thecompounds during the burning process in thekiln. All compounds of P.C. is soluble in HClkiln. All compounds of P.C. is soluble in HClexcept the silica.except the silica.

The amount of I.R., determined by chemicalThe amount of I.R., determined by chemicalanalysis, serves to indicate the completeness ofanalysis, serves to indicate the completeness ofthe reactions in the kiln.the reactions in the kiln.

ASTM C 150ASTM C 150 I.R. 0.75% I.R. 0.75%


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Loss on Ignition (L.O.I.):Loss on Ignition (L.O.I.): is the loss inis the loss inweight of cement after being heated toweight of cement after being heated to

10001000C. It indicates the prehydration orC. It indicates the prehydration orcarbonation due to prolonged or impropercarbonation due to prolonged or improperstorage of cement & clinker.storage of cement & clinker.

If cement is exposed to air, water & COIf cement is exposed to air, water & CO22are absorbed & by heating the cementare absorbed & by heating the cementupto 1000upto 1000C loose these two substances.C loose these two substances.

ASTM C 150ASTM C 150 L.O.I. 3% for O.P.C. L.O.I. 3% for O.P.C.


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COMPOUND COMPOSITIONCOMPOUND COMPOSITIONOF P.C. (OR CLINKER)OF P.C. (OR CLINKER)

Oxides interact with eachother in the kilnOxides interact with eachother in the kilnto form more complex productsto form more complex products

(compounds). Basically, the major(compounds). Basically, the majorcompoun s o . . can e s e as:compoun s o . . can e s e as:Name Chemical Formula Abbreviations

Tri Calcium Silicate 3CaO.SiO2 C3S

Di Calcium Silicate 2CaO.SiO2 C2S

Tri Calcium Aluminate 3CaO.Al2O3 C3A

Tetra Calcium Alumino

Ferrite

4CaO.Al2O3.Fe2O3 C4AF


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The degree to which the potentialThe degree to which the potentialreactions can proceed to equilibriumreactions can proceed to equilibrium

depends on:depends on:

1)1) Fineness of raw materials & theirFineness of raw materials & their

intermixing.intermixing.2)2) The temperature & time that mix is heldThe temperature & time that mix is held

in the critical zone of the kiln.in the critical zone of the kiln.

3)3) The grade of cooling of clinker may alsoThe grade of cooling of clinker may alsobe effective on the internal structure ofbe effective on the internal structure ofmajor compounds.major compounds.


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There are also some minor compoundsThere are also some minor compoundswhich constitute few %, so they arewhich constitute few %, so they are

usually negligible. Moreover, portlandusually negligible. Moreover, portlandcement compounds are rarely pure.cement compounds are rarely pure. For example in CFor example in C33S, MgO & AlS, MgO & Al22OO33 replacesreplaces

CaO randomly.CaO randomly. CC33SSALITE & CALITE & C22SBELITESBELITE Ferrite Phase:Ferrite Phase: CC44AF is not a trueAF is not a true

compound. The ferrite phase ranges fromcompound. The ferrite phase ranges fromCC22AF to CAF to C66AF. *CAF. *C44AF represents anAF represents an

average.average.

Methods of DeterminingMethods of Determining


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Methods of DeterminingMethods of DeterminingCompound CompositionCompound Composition

Each grain of cement consists of an intimateEach grain of cement consists of an intimatemixture of these compounds.mixture of these compounds. They can be determined by:They can be determined by:

1)1) MicroscopyMicroscopy2)2) XX--Ray DiffractionRay Diffraction

But due to the variabilities involved theBut due to the variabilities involved the

compound composition is usually calculatedcompound composition is usually calculatedusing the oxide proportions.using the oxide proportions.

3)3) Calculations (Bouges Equations)Calculations (Bouges Equations)

AssumptionsAssumptions


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AssumptionsAssumptions

1)1) The chemical reactions in the kilnThe chemical reactions in the kilnproceeded to equilibrium.proceeded to equilibrium.

2)2) Compounds are in pure form such as CCompounds are in pure form such as C33SS& C& C22SS

3)3) ignored.ignored.

4)4) Ferrite phase can be calculated as CFerrite phase can be calculated as C44AFAF5)5) All oxides in the kiln have taken part inAll oxides in the kiln have taken part in

forming the compounds.forming the compounds.


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%C%C33S=4.071(%C)S=4.071(%C)--7.6(%S)7.6(%S)--6.718(%A)6.718(%A)--1.43(%F)1.43(%F)--2.852(%2.852(%))

%C%C22S=2.867(%S)S=2.867(%S)--0.7544(%C0.7544(%C33S)S)

33 = .= . -- ..

%C%C44AF=3.043(%F)AF=3.043(%F)

EE Gi th f ll i id iti fGi th f ll i id iti f


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Ex:Ex:Given the following oxide composition ofGiven the following oxide composition ofa portland cement clinker.a portland cement clinker.

CaO=64.9% SiOCaO=64.9% SiO22=22.2%=22.2%AlAl22OO33=5.8% Fe=5.8% Fe22OO33=3.1% MgO=4%=3.1% MgO=4%Using Bogues eqns calculate theUsing Bogues eqns calculate the

com ound com osition of the P.C. clinker?com ound com osition of the P.C. clinker?

CC33S=4.071*64.9S=4.071*64.9--7.6*22.27.6*22.2--6.718*5.86.718*5.8--

1.43*3.1=52.1%1.43*3.1=52.1%CC22S=2.876*22.2S=2.876*22.2--0.7544*52.1=24.5%0.7544*52.1=24.5%CC33A=2.65*5.8A=2.65*5.8--1.692*3.1=10.1%1.692*3.1=10.1%

CC AF=3 043*3 1=9 4%AF=3 043*3 1=9 4%


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CC44AF=3.043 3.1=9.4%AF=3.043 3.1=9.4%

To see the effect of change in oxide compositionTo see the effect of change in oxide composition

on the change in compound composition,on the change in compound composition,assume that CaO is 63.9% & SiOassume that CaO is 63.9% & SiO22 is 23.2% andis 23.2% andothers are the same.others are the same.

33 . ,. , 22 . ,. , 33 ,,CC44AF=9.4%AF=9.4%

CC33S changed from 52.1%S changed from 52.1%40.4%40.4%

CC22S changed from 24.5%36.2%S changed from 24.5%36.2%

1% change in CaO & SiO1% change in CaO & SiO22 resulted in more thanresulted in more than10% change in C10% change in C33S & CS & C22S content.S content.

Influence of CompoundInfluence of Compound


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Influence of CompoundInfluence of CompoundComposition on CharacteristicsComposition on Characteristics

of P.C.of P.C. P.C.+waterP.C.+waterthe compounds in the cementthe compounds in the cementundergo chemical reactions with the waterundergo chemical reactions with the waterindependently, and different products result fromindependently, and different products result fromthese reactions.these reactions.

C3S C2S C3A C4AF

Rate of Reaction Moderate Slow Fast Moderate

Heat Liberation High Low Very High Moderate

Early Cementitious Value Good Poor Good Poor

Ultimate Cementitious Value Good Good Poor Poor


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ASTM Type & Name

of P.C.

Average Compound

CompositionC3S C2S C3A C4AF

Type I - O.P.C. 49 25 12 8 General Purpose

Type II - Modified 46 29 6 12

For Moderate Heat of

Hydration

Type III - High Early

Strength 56 15 12 8

C3S&C3A increased, C2S

decreased

Type IV - Low Heat

P.C. 30 46 5 13 C2S increased

Type V - Sulfate

Resistant P.C. 43 36 4 12

Limit on C3A5%,

2C3A+C4AF25%

Hydration of P CHydration of P C


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Hydration of P.C.Hydration of P.C.

Hydration:Hydration: Chemical reactions with water.Chemical reactions with water.

As water comes into contact with cementAs water comes into contact with cementparticles, hydration reactions immediatelyparticles, hydration reactions immediatelystarts at t e sur ace o t e part c es.starts at t e sur ace o t e part c es.

Although simple hydrates such as CAlthough simple hydrates such as C--H areH areformed, process of hydration is a complexformed, process of hydration is a complex

one and results in reorganization of theone and results in reorganization of theconstituents of original compounds toconstituents of original compounds toform new hydrated compounds.form new hydrated compounds.


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At t f h d ti th h d dAt t f h d ti th h d d


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At any stage of hydration the hardenedAt any stage of hydration the hardenedcement paste (hcp) consists of:cement paste (hcp) consists of:

Hydrates of various compounds referred toHydrates of various compounds referred tocollectively as GEL.collectively as GEL.

. . Some minor compound hydrates.Some minor compound hydrates. Unhydrated cementUnhydrated cement The residual of water filled spacesThe residual of water filled spaces pores.pores.

As the hydration proceeds the deposits ofAs the hydration proceeds the deposits of


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As the hydration proceeds the deposits ofAs the hydration proceeds the deposits ofhydrated products on the original cementhydrated products on the original cementgrains makes the diffusion of water tograins makes the diffusion of water tounhydrated nucleus more & more difficult.unhydrated nucleus more & more difficult.Thus, the rate of hydration decreases withThus, the rate of hydration decreases withtime & as a result hydration may taketime & as a result hydration may take

several ears.several ears.

Major compounds start to produce:Major compounds start to produce:

CalciumCalcium--silicatesilicate--hydrate gelshydrate gels Calcium hydroxide cementCalcium hydroxide cement CalciumCalcium--aluminoalumino--sulfohydrates gelsulfohydrates gel

At th b i i f i i th t hAt th b i i f i i th t h


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At the beginning of mixing, the paste has aAt the beginning of mixing, the paste has astructure which consists of cement particlesstructure which consists of cement particles

with waterwith water--filled space between them. Asfilled space between them. Ashydration proceeds, the gels are formed &hydration proceeds, the gels are formed &they occupy some of this space.they occupy some of this space.

1cc of cement1cc of cement 2.1cc of gel 2.1cc of gel

Gel Pores:Gel Pores: 28% of the total gel volume have28% of the total gel volume havediameter of 0.015diameter of 0.015--0.0200.020 m. (very smallm. (very small--lossloss

or gain of water is difficult)or gain of water is difficult)

Capillary PoresCapillary Pores: 12 5: 12 5 m diameter with varyingm diameter with varying


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Capillary PoresCapillary Pores: 12.5: 12.5 m diameter, with varyingm diameter, with varyingsizes, shapes & randomly distributed in the paste.sizes, shapes & randomly distributed in the paste.

Volume of capillary pores decreases as hydrationVolume of capillary pores decreases as hydrationtakes place. Water in capillary pores is mobile,takes place. Water in capillary pores is mobile,can not be lost by evaporation or water can getcan not be lost by evaporation or water can get

permeability.permeability.

-- w/c ratiow/c ratio capillary porositycapillary porosity-- degree of hydrationdegree of hydration

CC22S & CS & C33S:S: 7070--80% of cement is composed of80% of cement is composed of


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CC22S & CS & C33S:S: 7070 80% of cement is composed of80% of cement is composed ofthese two compounds & most of the strengththese two compounds & most of the strengthgiving properties of cement is controlled by thesegiving properties of cement is controlled by these

compounds.compounds.

Upon hydration both calciumUpon hydration both calcium--silicates result in thesilicates result in thesame products.same products.

33 33 22 33 2C2C22S+4H CS+4H C33SS22HH33 + CH+ CH

CalciumCalcium--SilicateSilicate--Hydrate (CHydrate (C--SS--H gel) is similar toH gel) is similar toa mineral called TOBERMORITE. As a result ita mineral called TOBERMORITE. As a result itis named as TOBERMORITE GELis named as TOBERMORITE GEL

Upon hydration CUpon hydration C S & CS & C S CH also formsS CH also forms


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Upon hydration CUpon hydration C33S & CS & C22S, CH also formsS, CH also formswhich becomes an integral part ofwhich becomes an integral part of

hydration products. CH does not contributehydration products. CH does not contributevery much to the strength of portlandvery much to the strength of portlandcement.cement.

CC33S having a faster rate of reactionS having a faster rate of reactionaccompanied by greater heat generationaccompanied by greater heat generationdevelopes early strength of the paste. Ondevelopes early strength of the paste. Onthe other hand, Cthe other hand, C22S hydrates & hardensS hydrates & hardensslowly so results in less heat generation &slowly so results in less heat generation &developes most of the ultimate strength.developes most of the ultimate strength.

Higher CHigher C33SShigher early strengthhigher early strength--higherhigher


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Higher CHigher C33SS higher early strengthhigher early strength higherhigherheat generation (roads, cold environments)heat generation (roads, cold environments)

Higher CHigher C22

Slower early strengthSlower early strength--lowerlowerheat generation (dams)heat generation (dams)

CC33AA: is characteristically fast reacting with: is characteristically fast reacting with

paste with a large amount of the heatpaste with a large amount of the heatgeneration (Flashgeneration (Flash--Set)Set)--(Quick(Quick--Set). In orderSet). In order

to prevent this rapid reaction gypsum isto prevent this rapid reaction gypsum isadded to the clinker. Gypsum, Cadded to the clinker. Gypsum, C33A&waterA&waterreact to form relatively insoluble Calciumreact to form relatively insoluble Calcium--SulfoSulfo--Aluminates.Aluminates.

CC33A+CA+CHH22+10H+10HCC44AAHH1212 (calcium(calcium-- aluminoalumino--


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33 22 44 1212 ((monosulfohydrate)monosulfohydrate)CC33A+3CA+3CHH22+26H+26HCC66AA33HH3232 (calcium(calcium--aluminoalumino--

trisulfohydrate ettringite)trisulfohydrate ettringite)

When there is enough gypsum ettringite formsWhen there is enough gypsum ettringite formswith great expansionwith great expansion

If there is no gypsumIf there is no gypsumflashflash--setsetmore gypsumettringitemore gypsumettringite

formation increasesformation increases

which will cause crackingwhich will cause cracking

Also CalciumAlso Calcium--Sulfo Aluminates are prone (lessSulfo Aluminates are prone (less) lf k & d b) lf k & d b


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resistant) to sulfate attack & does not contributeresistant) to sulfate attack & does not contributemuch for strength. The cement to be used inmuch for strength. The cement to be used in

making concretes that are going to be exposedmaking concretes that are going to be exposedto soils or waters that contain sulfates shouldto soils or waters that contain sulfates shouldnot contain more than 5% Cnot contain more than 5% C33A.A.

CC44AFAF: The hydration of ferrite phase is not well: The hydration of ferrite phase is not wellun erstan . err te p ase as esser ro e nun erstan . err te p ase as esser ro e ndevelopment of strength. The hydrationdevelopment of strength. The hydrationproducts are similar to Cproducts are similar to C33A. Alumina & ironA. Alumina & ironoxide occur interchangebly in the hydrationoxide occur interchangebly in the hydrationproducts.products.

CC44AAHH1212 or Cor C44FFHH1212

CC66AA33HH3232 or Cor C66FF33HH3232

HEAT OF HYDRATIONHEAT OF HYDRATION


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Hydration process of cement is accompanied byHydration process of cement is accompanied by

heat generation (exothermic).heat generation (exothermic).As concrete is a fair insulator, the generatedAs concrete is a fair insulator, the generatedheat in mass concrete may result in expansion &heat in mass concrete may result in expansion &cracking. This could be overcome by usingcracking. This could be overcome by usingsuitable cement type.suitable cement type.

concreting.concreting. The heat of hydration of OPC is on the order ofThe heat of hydration of OPC is on the order of

8585--100 cal/gr.100 cal/gr.About 50% of this heat is liberatedwithin 1About 50% of this heat is liberatedwithin 1--33days & 75% within 7 days.days & 75% within 7 days. By limiting CBy limiting C33S&CS&C33A content heat of hydrationA content heat of hydration

can be reduced.can be reduced.


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FINENESS OF CEMENTFINENESS OF CEMENT


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As hydration takes place at the surface ofAs hydration takes place at the surface of

the cement particles, it is the surface areathe cement particles, it is the surface areaof cement particles which provide theof cement particles which provide thematerial available for hydration. The rate ofmaterial available for hydration. The rate of

cement. For a rapid rate of hydration acement. For a rapid rate of hydration ahigher fineness is necessary.higher fineness is necessary.

However,However,


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,,

Higher fineness requires higher grindingHigher fineness requires higher grinding(cost )(cost ) Finer cements deteriorate faster uponFiner cements deteriorate faster upon

ex osure to atmos here.ex osure to atmos here. Finer cements are very sensitive to alkaliFiner cements are very sensitive to alkali--

aggregate reaction.aggregate reaction.

Finer cements require more gypsum forFiner cements require more gypsum forproper hydration.proper hydration. Finer cements require more water.Finer cements require more water.

Fineness of cement is determined by airFineness of cement is determined by air


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yypermeability methods. For example, in thepermeability methods. For example, in the

Blaine air permeability method a knownBlaine air permeability method a knownvolume of air is passed through cement.volume of air is passed through cement.The time is recorded and the specificThe time is recorded and the specificsurface is calculated by a formula.surface is calculated by a formula.

Fineness is expressed in terms of specificFineness is expressed in terms of specificsurface of the cement (cmsurface of the cement (cm22/gr). For OPC/gr). For OPCspecific surface is 2600specific surface is 2600--3000 cm3000 cm22/gr./gr.


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SETTINGSETTING


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Setting refers to a change from liquid state toSetting refers to a change from liquid state to

solid state. Although, during setting cementsolid state. Although, during setting cementpaste acquires some strength, setting is differentpaste acquires some strength, setting is differentfrom hardening.from hardening.

The water content has a marked effect on theThe water content has a marked effect on thetime of setting. In acceptance tests for cement,time of setting. In acceptance tests for cement,the water content is regulated by bringing thethe water content is regulated by bringing the

paste to a standard condition of wetness. This ispaste to a standard condition of wetness. This iscalled normal consistency.called normal consistency.

Normal consistency of O.P.C. Ranges from 20Normal consistency of O.P.C. Ranges from 20--30% b i ht f t30% b i ht f t


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30% by weight of cement.30% by weight of cement.

Vicat apparatus is used to determine normalVicat apparatus is used to determine normalconsistency. Normal consistency is that conditionconsistency. Normal consistency is that conditionfor which the penetration of a standard weighedfor which the penetration of a standard weighedplunger into the paste is 10mm in 30sec. By trialplunger into the paste is 10mm in 30sec. By trial

. .

In practice, the terms initial set&final set are usedIn practice, the terms initial set&final set are usedto describe arbitrary chosen time of setting. Initialto describe arbitrary chosen time of setting. Initialset indicates the beginning of a noticeableset indicates the beginning of a noticeablestiffening & final set may be regarded as the startstiffening & final set may be regarded as the startof hardening (or complete loss of plasticity).of hardening (or complete loss of plasticity).


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Setting can be obtained by using the vicatSetting can be obtained by using the vicat


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apparatus.apparatus.

Initial setting timeInitial setting time>>45min45minASTM C150ASTM C150

InitialInitial >> 1hr (60min)1hr (60min) TS 19TS 19

FinalFinal


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g gg g

Temperature & HumidityTemperature & HumidityAmount of WaterAmount of Water Chemical Composition of CementChemical Composition of Cement

setting)setting)

FlashFlash--setsetAbnormal SettingsAbnormal Settings

FalseFalse--setset

FlashFlash--SetSet: is the immediate stiffening of cement: is the immediate stiffening of cementpaste in a few minutes after mixing with waterpaste in a few minutes after mixing with water


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paste in a few minutes after mixing with water.paste in a few minutes after mixing with water.It is accompanied by large amount of heatIt is accompanied by large amount of heat

generation upon reaction of C3A with water.generation upon reaction of C3A with water.

Gypsum is placed in cement to prevent flashGypsum is placed in cement to prevent flash--set. The rigidity can not be overcome & plasticityset. The rigidity can not be overcome & plasticity

. .

Amount of gypsum must be such that it will beAmount of gypsum must be such that it will beused upto almost hardening. Because expansionused upto almost hardening. Because expansioncaused by ettringite can be distributed to thecaused by ettringite can be distributed to thepaste before hardening. More gypsum will causepaste before hardening. More gypsum will causeundesirable expansion after hardening.undesirable expansion after hardening.

FalseFalse--SetSet: is a rapid development of rigidity of cement: is a rapid development of rigidity of cementpastepaste without generation of much heatwithout generation of much heat ThisThis


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pastepaste without generation of much heat.without generation of much heat. ThisThisrigidity can be overcome & plasticity can berigidity can be overcome & plasticity can be

regained by further mixing without addition ofregained by further mixing without addition ofwater. In this way cement paste restores itswater. In this way cement paste restores itsplasticity & sets in a normal manner without anyplasticity & sets in a normal manner without anyloss of strength.loss of strength.

Probable Causes of FalseProbable Causes of False--Set:Set:

1)1) When gypsum is ground by too hot of a clinker,When gypsum is ground by too hot of a clinker,

gypsum may be dehydrated into hemihydrategypsum may be dehydrated into hemihydrate(CaSO(CaSO44.1/2H.1/2H22O) or anhydrate (CaSOO) or anhydrate (CaSO44). These). Thesematerials when react with water gypsum ismaterials when react with water gypsum isformed, which results in stiffening of the paste.formed, which results in stiffening of the paste.


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2)2) Alkali oxides in cement may carbonateAlkali oxides in cement may carbonate

during storage. Upon mixing such aduring storage. Upon mixing such acement with water, these alkali carbonatescement with water, these alkali carbonateswill react with Ca(OHwill react with Ca(OH22) (CH) (CH--CalciumCalciumHydroxide) liberated by hydrolysis of CHydroxide) liberated by hydrolysis of C

33SS

resulting in CaCOresulting in CaCO33. CaCO. CaCO33 precipates inprecipates inthe mix & results in falsethe mix & results in false--set.set.

SOUNDNESS OF CEMENTSOUNDNESS OF CEMENT


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Soundness is defined as the volume stability of cementSoundness is defined as the volume stability of cementpaste.paste.

The cement paste should not undergo large changes inThe cement paste should not undergo large changes involume after it has set. Free CaO&MgO may result involume after it has set. Free CaO&MgO may result inunsound cement. Upon hydration C&M will form CH&MHunsound cement. Upon hydration C&M will form CH&MH

. .

Since unsoundness is not apparent until several monthsSince unsoundness is not apparent until several monthsor years, it is necessary to provide an acceleratedor years, it is necessary to provide an acceleratedmethod for its determination.method for its determination.

1)1) Lechatelier Method: Only free CaO can be determined.Lechatelier Method: Only free CaO can be determined.2)2) Autoclave Method: Both free CaO&MgO can beAutoclave Method: Both free CaO&MgO can be

determined.determined.

STRENGTH OF CEMENTSTRENGTH OF CEMENT


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Strength tests are not carried out on neatStrength tests are not carried out on neat

cement pastes, because it is very difficultcement pastes, because it is very difficultto form these pastes due to cohesiveto form these pastes due to cohesiveproperty of cement.property of cement.

Strength tests are carried out on cementStrength tests are carried out on cementmortar prepared by standard gradation (1mortar prepared by standard gradation (1

part cement+3 parts sand+1/2 partpart cement+3 parts sand+1/2 partwater)water)

1)1) Direct Tension (Tensile Strength):Direct Tension (Tensile Strength):


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PP

tt=P/1in=P/1in22

Difficult test procedureDifficult test procedure

1


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2)2) Flexural Strength (tensile strength in bending):Flexural Strength (tensile strength in bending):


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P

L

4cm

4cm

C

f=(M*C)/If=(M*C)/I M:maximum momentM:maximum moment

I:moment of inertiaI:moment of inertia C:distance to bottom fiber from C.G.C:distance to bottom fiber from C.G.


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3)3) Compression Test:Compression Test:


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i) Cubic Sample ii)Flexural Sample after iti) Cubic Sample ii)Flexural Sample after itis brokenis broken

P

4cm4cm

P

c=P/A

4cm

c=P/A

A=4x4


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TYPES OF PORTLAND CEMENTTYPES OF PORTLAND CEMENT


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Cements of different chemical compositionCements of different chemical composition

& physical characteristics may exhibit& physical characteristics may exhibitdifferent properties when hydrated. Itdifferent properties when hydrated. Itshould thus be possible to select mixturesshould thus be possible to select mixtures

cements with various properties.cements with various properties.

In fact several cement types are availableIn fact several cement types are availableand most of them have been developed toand most of them have been developed toensure durability and strength propertiesensure durability and strength propertiesto concrete.to concrete.

It should also be mentioned that obtainingIt should also be mentioned that obtainingsome special properties of cement may lead tosome special properties of cement may lead to


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p p p yp p p yundesirable properties in another respect. Forundesirable properties in another respect. For

this reason a balance of requirements may bethis reason a balance of requirements may benecessary and economic aspects should benecessary and economic aspects should beconsidered.considered.

the definition of P.C., and are produced bythe definition of P.C., and are produced byadjusting the proportions of four majoradjusting the proportions of four majorcompounds.compounds.

2)2) Special TypesSpecial Types: these do not necessarily couply: these do not necessarily couplywith the definiton of P.C. & are produced bywith the definiton of P.C. & are produced byusing additional raw materials.using additional raw materials.

Standard Cements (ASTM)Standard Cements (ASTM)T IT I O di P tl d C tO di P tl d C t


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Type IType I: Ordinary Portland Cement: Ordinary Portland CementSuitable to be used in general concreteSuitable to be used in general concreteconstruction when special properties are notconstruction when special properties are notrequired.required.

Type IIType II: Modified Portland Cement: Modified Portland CementSuitable to be used in general concreteSuitable to be used in general concrete

construction. Main difference between Type I&IIconstruction. Main difference between Type I&IIis the moderate sulfate resistance of Type IIis the moderate sulfate resistance of Type IIcement due to relatively low C3A contentcement due to relatively low C3A content

(%8). Since C(%8). Since C33A is limited rate of reactions isA is limited rate of reactions isslower and as a result heat of hydration at earlyslower and as a result heat of hydration at earlyages is less. *It is suitable to be used in smallages is less. *It is suitable to be used in smallscale mass concrete like retaining walls.scale mass concrete like retaining walls.

Type IIIType III: High Early Strength P.C.: High Early Strength P.C.Strength development is rapid.Strength development is rapid.

d fd f d fd f ff


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3 days f3 days fcc=7 days f=7 days fcc of Type Iof Type I

It is useful for repair works, cold weather & forIt is useful for repair works, cold weather & forearly demolding.early demolding.Its early strength is due to higher CIts early strength is due to higher C33S & CS & C33AAcontent.content.

Type IVType IV: Low Heat P.C.: Low Heat P.C.Generates less heat during hydration & thereforeGenerates less heat during hydration & thereforegain of strengthis slower.gain of strengthis slower.In standards a maximum value of CIn standards a maximum value of C

33S&CS&C

33A& aA& a

minimum value for Cminimum value for C22S are placed.S are placed.It is used in massIt is used in mass--concrete and hotconcrete and hot--weatherweatherconcreting.concreting.

Type V:Type V: Sulfate Resistant P.C.Sulfate Resistant P.C.Used in construction where concrete will beUsed in construction where concrete will be


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subjected to external sulfate attacksubjected to external sulfate attack chemicalchemical

plants, marine & harbor structures.plants, marine & harbor structures.i)i) During hydration CDuring hydration C33A reacts with gypsum &A reacts with gypsum &

water to form ettringite. In hardened cementwater to form ettringite. In hardened cementaste calciumaste calcium--aluminoalumino--h drate can react withh drate can react with

calcium&alumino sulfates, from externalcalcium&alumino sulfates, from externalsources, to form ettringite which causessources, to form ettringite which causesexpansion & cracking.expansion & cracking.

ii)ii) CC--H and sulfates can react & form gypsumH and sulfates can react & form gypsumwhich again causes expansion & cracking.which again causes expansion & cracking.* In Type V C* In Type V C33A is limited to 5%.A is limited to 5%.

Type IA, IIA, IIIAType IA, IIA, IIIA: Air Entrained Portland: Air Entrained PortlandCementCement


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CementCement

Only difference is adding an airOnly difference is adding an air--entrainingentrainingagent to the cement during manufacturingagent to the cement during manufacturingto increase freezeto increase freeze--thaw resistance bythaw resistance byproviding small sized air bubbles inproviding small sized air bubbles inconcrete.concrete.


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Portland Blast Furnace Slag Cement (P.B.F.S.C.)Portland Blast Furnace Slag Cement (P.B.F.S.C.) By intergrinding B.F.S.+P.C. Clinker+GypsumBy intergrinding B.F.S.+P.C. Clinker+Gypsum This cement is less reactive (rate of gain of strengthThis cement is less reactive (rate of gain of strength


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This cement is less reactive (rate of gain of strengthThis cement is less reactive (rate of gain of strength& early strength is less but ultimate strength is& early strength is less but ultimate strength is

same)same) High sulfate resistanceHigh sulfate resistance Suitable to use in mass concrete constructionSuitable to use in mass concrete construction Unsuitable for cold weather concretingUnsuitable for cold weather concreting

Both P.P.C.&P.B.F.S.C. Are called blended cements.Both P.P.C.&P.B.F.S.C. Are called blended cements.Their heat of hydration & strength development areTheir heat of hydration & strength development arelow in early days. Because upon adding water Clow in early days. Because upon adding water C33SScompounds start to produce Ccompounds start to produce C--SS--Hgels & CH. TheHgels & CH. The

Ch & the pozzolanic material react together toCh & the pozzolanic material react together toproduce new Cproduce new C--SS--H gels. Thats why the earlyH gels. Thats why the earlystrength is low but the ultimate strength is the samestrength is low but the ultimate strength is the samewhen compared to O.P.C.when compared to O.P.C.

White Portland CementWhite Portland Cement W P C s made from materials containingW P C s made from materials containing


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W.P.C. s made from materials containingW.P.C. s made from materials containing

a little iron oxide & manganese oxide.a little iron oxide & manganese oxide. FeFe22OO33 + MnO 0.8%+ MnO 0.8% To avoid contamination by coal ash, oil isTo avoid contamination by coal ash, oil is

. . To avoid contamination by iron duringTo avoid contamination by iron during

grinding, instead of steel balls nickelgrinding, instead of steel balls nickel--

molybdenum alloys are used.molybdenum alloys are used.

High Alumina CementHigh Alumina Cement The raw materials for H.A.C. s limestoneThe raw materials for H.A.C. s limestone


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and Bauxite (Aland Bauxite (Al22OO33 & Fe& Fe22OO33)) These raw materials are interground &These raw materials are interground &

introduced in the kiln clinkered at 1600introduced in the kiln clinkered at 1600C.C.Then the obtained material is ground to aThen the obtained material is ground to a

-- .. The oxide composition is quite differentThe oxide composition is quite differentAlAl22OO33 40 40--45%45%

CaO 35CaO 35--42%42%FeFe22OO33 5 5--15%15%

SiOSiO22 4 4--10%10%

Major compounds are CA & C2SMajor compounds are CA & C2S It is basically different from O.P.C. & theIt is basically different from O.P.C. & the


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yyconcrete made from this cement has veryconcrete made from this cement has very

different properties.different properties. It has high sulfate resistance.It has high sulfate resistance. Very high early strength (emergency repairs)Very high early strength (emergency repairs)

ou o u ma e s reng s o a neou o u ma e s reng s o a newithin 24 hours. But the strength is adverselywithin 24 hours. But the strength is adverselyaffected by temperature. The setting time is notaffected by temperature. The setting time is notas rapid as gain of strength.as rapid as gain of strength.

Initial setting time is 4 hrs & final setting time isInitial setting time is 4 hrs & final setting time is5 hrs.5 hrs.

STANDARD TURKISH CEMENTSSTANDARD TURKISH CEMENTS(TS 19)(TS 19) CancelledCancelled TS 19 groups them into 3TS 19 groups them into 3


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TS 19 groups them into 3TS 19 groups them into 3P.. 32.5P.. 32.5 min. Compressive strength is 32.5 MPa in min. Compressive strength is 32.5 MPa in28 days.28 days.P.. 42.5P.. 42.5

P.. 52.5P.. 52.5

Special Cements are:Special Cements are:

TS 20TS 20 Blast Furnace Slag CementBlast Furnace Slag Cement

C 32.5C 32.5 Cruflu imentoCruflu imento

C 42.5C 42.5

TS 21TS 21 White Portland Cement BP 32.5White Portland Cement BP 32.5--42.542.5

TS22TS22 Masonry Cement, H 16 (Har imentosu)Masonry Cement, H 16 (Har imentosu)

TS 26TS 26 Trass Cement, T 32.5 (Trasl imento)Trass Cement, T 32.5 (Trasl imento)

TS 640TS 640 Fly Ash Cement, UK 32.5 (Uucu KllFly Ash Cement, UK 32.5 (Uucu Kllimento)imento)

TS EN 197TS EN 197--11NEWNEW


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NEWNEWCEM cementsCEM cements

CEM I Portland Cement

CEM II Portland Composite

CEM III Portland Blast FurnaceSlag Cement

CEM IV Pozzolanic Cement

CEM V Composite Cement

27 different cements

TS EN 197TS EN 197--11


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CEM cements :CEM cements : Binding property is mainly due to hydration ofBinding property is mainly due to hydration of

calciumcalcium--silicatessilicates Reactive C + Reactive S > 50%Reactive C + Reactive S > 50%

Clinker, major and minor mineral admixturesClinker, major and minor mineral admixtures Clinker + Major + Minor = 100% (mass) + GypsumClinker + Major + Minor = 100% (mass) + Gypsum Major > 5% by massMajor > 5% by mass MinorMinor 5% by mass5% by mass

TS EN 197TS EN 197--11Mineral AdmixturesMineral Admixtures


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Mineral AdmixturesMineral Admixtures K : ClinkerK : Clinker D : Silica FumeD : Silica Fume P : Natural PozzolanP : Natural Pozzolan

T : Calcined ShaleT : Calcined Shale W : ClassW : Class C Fly AshC Fly Ash V : ClassV : Class F Fly AshF Fly Ash

L : Limestone (Organic compound < 0.5%)L : Limestone (Organic compound < 0.5%) LL : Limestone (Organic compound < 0.2%)LL : Limestone (Organic compound < 0.2%) S : Granulated Blast Furnace SlagS : Granulated Blast Furnace Slag

TS EN 197TS EN 197--11CompositionComposition


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CompositionComposition

A : Lowest amount of mineral admixtureA : Lowest amount of mineral admixture B : Mineral admixture amount is > AB : Mineral admixture amount is > A



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CEM I :CEM I : Portland CementPortland Cement9595--100%100% KK+ 0+ 0--5%5% MinorMinor



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CompositionComposition CEM II :CEM II : Portland Composite CementPortland Composite Cement

CEM II/ACEM II/A--S :S : Portland Slag CementPortland Slag Cement

-- -- --CEM II/BCEM II/B--S :S : Portland Slag CementPortland Slag Cement6565--79%79% KK+ 21+ 21--35%35% SS + 0+ 0--5%5% MinorMinor

CEM II/BCEM II/B--P :P : Portland Pozzolanic CementPortland Pozzolanic Cement

6565--79%79% KK+ 21+ 21--35%35% PP + 0+ 0--5%5% MinorMinorCEM II/ACEM II/A--V :V : Portland Fly Ash CementPortland Fly Ash Cement8080--94%94% KK+ 6+ 6--20%20%VV+ 0+ 0--5%5% MinorMinor



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CompositionComposition CEM III :CEM III : Portland Blast Furnace Slag Cement

CEM III A :CEM III A : Portland Blast Furnace Sla CementPortland Blast Furnace Sla Cement3535--64%64% KK+ 36+ 36--65%65% SS + 0+ 0--5%5% MinorMinor

CEM III/B :CEM III/B : Portland Blast Furnace Slag CementPortland Blast Furnace Slag Cement2020--34%34% KK+ 66+ 66--80%80% SS + 0+ 0--5%5% MinorMinor

CEM III/C :CEM III/C : Portland Blast Furnace Slag CementPortland Blast Furnace Slag Cement55--19%19% KK+ 81+ 81--95%95% SS + 0+ 0--5%5% MinorMinor



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CEM IV :CEM IV : Pozzolanic Cement

6565--89%89% KK+ 11+ 11--35%35% (D,P,Q,V,W)(D,P,Q,V,W) + 0+ 0--5%5% MinorMinor

CEM IV/B :CEM IV/B : Pozzolanic CementPozzolanic Cement

4545--64%64% KK+ 36+ 36--55%55% (D,P,Q,V,W)(D,P,Q,V,W) + 0+ 0--5%5% MinorMinor



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CEM V :CEM V : CompositeComposite Cement

4040--64%64% KK+ 18+ 18--30%30% SS + 18+ 18--30%30% (P,Q,V)(P,Q,V) + 0+ 0--5%5%

MinorMinor

CEM V/B :CEM V/B : Composite CementComposite Cement2020--38%38% KK+ 31+ 31--50%50% SS + 31+ 31--50%50% (P,Q,V)(P,Q,V) + 0+ 0--5%5%

MinorMinor

Strength ClassesStrength Classes


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NameName -- ExampleExample


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CEM II / ACEM II / A P 42.5 NP 42.5 N CEM II / ACEM II / A P 42.5 RP 42.5 R

cement production read that

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