PORTLAND CEMENTPORTLAND CEMENT

Portland Cement Portland Cement → Gypsum+Portland → Gypsum+Portland Cement Clinker (pulverizing)Cement 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

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

1)1) Calcareous Rocks (CaCOCalcareous Rocks (CaCO33 >> 75%) 75%) LimestoneLimestone MarlMarl ChalkChalk Marine shell depositsMarine shell deposits

2)2) Argillocalcareous Rocks Argillocalcareous Rocks (40%(40%<<CaCOCaCO33<<75%)75%)

Cement rockCement rock Clayey limestoneClayey limestone Clayey marlClayey marl Clayey chalkClayey chalk

3)3) Argillaceous Rocks (CaCOArgillaceous Rocks (CaCO33 << 40%) 40%) ClaysClays ShalesShales SlatesSlates

Portland cement is made by mixing Portland cement is made by mixing substances containing CaCOsubstances containing CaCO33 with with substances containing SiOsubstances containing SiO22, Al, Al22OO33, , FeFe22OO33 and heating them to a clinker and heating them to a clinker which is subsequently ground to which is subsequently ground to powder and mixed with 2-6 % powder and mixed with 2-6 % gypsum. gypsum.

CLINKER

GYPSUM

PRODUCTION STEPSPRODUCTION STEPS

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

2)2) Raw materials are mixed with definite Raw materials are mixed with definite proportions to obtain “raw mix”. They are proportions to obtain “raw mix”. They are mixed either dry (dry mixing) or by water mixed either dry (dry mixing) or by water (wet mixing). (wet mixing).

3)3) Prepared raw mix is fed into the rotary Prepared raw mix is fed into the rotary kiln.kiln.

4)4) As the materials pass through the kiln As the materials pass through the kiln their temperature is rised upto 1300-1600 their temperature is rised upto 1300-1600 °°C. The process of heating is named as C. The process of heating is named as “burning”. The output is known as “burning”. The output is known as “clinker” which is 0.15-5 cm in diameter.“clinker” which is 0.15-5 cm in diameter.

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

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

7)7) Packing & marketting.Packing & marketting.

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

~~150-350C150-350C°→°→ loosely bound water is lost from loosely bound water is lost from clay.clay.

~~350-650350-650°°CC→→decomposition of decomposition of clay→SiOclay→SiO22&Al&Al22OO33

~~600600°°CC→→decomposition of MgCOdecomposition of MgCO33→→MgO&COMgO&CO22 (evaporates)(evaporates)

~~900900°°CC→→decomposition of CaCOdecomposition of CaCO33→→CaO&COCaO&CO22 (evaporates)(evaporates)

~~1250-12801250-1280°°CC→→liquid formation & start of liquid formation & start of compound formation.compound formation.

~~12801280°°CC→→clinkering begins.clinkering begins.

~~1400-15001400-1500°°CC→→clinkeringclinkering

~~100100°°CC→→clinker leaves the kiln & falls into a clinker leaves the kiln & falls into a cooler.cooler.

Sometimes the burning process of raw materials Sometimes the burning process of raw materials is performed in two stages: preheating upto is performed in two stages: preheating upto 900900°°C & rotary kilnC & rotary kiln

CHEMICAL COMPOSITION CHEMICAL COMPOSITION OF P.C.OF P.C.

Portland cement is composed of four Portland cement is composed of four major oxides (CaO, SiOmajor oxides (CaO, SiO22, Al, Al22OO33, Fe, Fe22OO33 ≥90%) & some minor oxides. Minor ≥90%) & some minor oxides. Minor refers to the quantity not refers to the quantity not importance.importance.

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

Na2O Soda N0.2-1.3

K2O Potassa K

SO3 Sulfuric Anhydride ŚŚ 1-3

CaOCaO→limestone→limestone SiOSiO22-Al-Al22OO33→Clay→Clay

FeFe22OO33→Impurity in Clays→Impurity in Clays

SOSO33→from gypsum→not from the clinker→from gypsum→not from the clinker

S

The amount of oxides in a P.C. Depend on the The amount of oxides in a P.C. Depend on the proportioning of the raw materials and how well proportioning of the raw materials and how well the burning is done in the kiln. The chemical the burning is done in the kiln. The chemical composition is found by chemical analysis.composition is 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

A 6

F 2.4

ŚŚ 2.1

M 2.6

N 0.1

K 0.9

Free C 1.4

Total 99.8

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

The proportions of these oxides determine The proportions of these oxides determine the proportions of the compounds which the proportions of the compounds which affect the performance of the cement.affect the performance of the cement.

SOSO33→comes largely from gypsum→comes largely from gypsum

P.C. alone sets quickly so some gypsum is P.C. alone sets quickly so some gypsum is ground with clinker to retard the setting time. ground with clinker to retard the setting time.

If too much gypsum is included it If too much gypsum is included it leads to distruptive expansions of the leads to distruptive expansions of the hardened paste or concrete.hardened paste or concrete.

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

MgO+HMgO+H2O→MHO→MH

C+H→CH volume expansion & cause C+H→CH volume expansion & cause cracking.cracking.

ASTM C 150 → MASTM C 150 → M<<6%6% free C free C << 3% 3%

Alkalies (NaAlkalies (Na22O & KO & K22O) may cause O) may cause some dificulties if the cement is used some dificulties if the cement is used with certain types of reactive with certain types of reactive aggregates in making concrete. The aggregates in making concrete. The alkalies in the form of alkaline alkalies in the form of alkaline hydroxides can react with the hydroxides can react with the reactive silica of the aggregate & reactive silica of the aggregate & resulting in volume expansion after resulting in volume expansion after hardening. This process may take hardening. This process may take years.years.

NaNa22O & KO & K22O ≤ 0.6%O ≤ 0.6%

Insoluble Residue: Insoluble Residue: is that fraction of is that fraction of cement which is insoluble in HCl. It comes cement which is insoluble in HCl. It comes mainly from the silica which has not mainly from the silica which has not reacted to form compounds during the reacted to form compounds during the burning process in the kiln. All compounds burning process in the kiln. All compounds of P.C. is soluble in HCl except the silica.of P.C. is soluble in HCl except the silica.

The amount of I.R., determined by The amount of I.R., determined by chemical analysis, serves to indicate the chemical analysis, serves to indicate the completeness of the reactions in the kiln.completeness of the reactions in the kiln.

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

Loss on Ignition (L.O.I.):Loss on Ignition (L.O.I.): is the loss in is the loss in weight of cement after being heated to weight of cement after being heated to 10001000°°C. It indicates the prehydration C. It indicates the prehydration or carbonation due to prolonged or or carbonation due to prolonged or improper storage of cement & clinker.improper storage of cement & clinker.

If cement is exposed to air, water & If cement is exposed to air, water & COCO22 are absorbed & by heating the are absorbed & by heating the cement upto 1000cement upto 1000°°C loose these two C loose these two substances.substances.

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

COMPOUND COMPOUND COMPOSITION OF P.C. COMPOSITION OF P.C.

(OR CLINKER)(OR CLINKER) Oxides interact with eachother in the Oxides interact with eachother in the

kiln to form more complex products kiln to form more complex products (compounds). Basically, the major (compounds). Basically, the major compounds of P.C. can be listed as:compounds of P.C. can be listed 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

The degree to which the potential The degree to which the potential reactions can proceed to reactions can proceed to “equilibrium” depends on:“equilibrium” depends on:

1)1) Fineness of raw materials & their Fineness of raw materials & their intermixing.intermixing.

2)2) The temperature & time that mix is The temperature & time that mix is held in the critical zone of the kiln.held in the critical zone of the kiln.

3)3) The grade of cooling of clinker may The grade of cooling of clinker may also be effective on the internal also be effective on the internal structure of major compounds.structure of major compounds.

There are also some minor There are also some minor compounds which constitute few %, compounds which constitute few %, so they are usually negligible. so they are usually negligible. Moreover, portland cement Moreover, portland cement compounds are rarely pure. compounds are rarely pure.

For example in CFor example in C33S, MgO & AlS, MgO & Al22OO33 replaces CaO randomly.replaces CaO randomly.

CC33SS→ALITE & C→ALITE & C22S→BELITES→BELITE

Ferrite Phase: Ferrite Phase: CC44AF is not a true AF is not a true

compound. The ferrite phase ranges from compound. The ferrite phase ranges from CC22AF to CAF to C66AF. *CAF. *C44AF represents an AF represents an

average.average.

Methods of Determining Methods of Determining Compound CompositionCompound Composition

Each grain of cement consists of an Each grain of cement consists of an intimate mixture of these compounds.intimate mixture of these compounds.

They can be determined by:They can be determined by:

1)1) MicroscopyMicroscopy2)2) X-Ray DiffractionX-Ray Diffraction

But due to the variabilities involved the But due to the variabilities involved the compound composition is usually compound composition is usually calculated using the oxide proportions.calculated using the oxide proportions.

3)3) Calculations (Bouge’s Equations) Calculations (Bouge’s Equations)

AssumptionsAssumptions

1)1) The chemical reactions in the kiln The chemical reactions in the kiln proceeded to equilibrium.proceeded to equilibrium.

2)2) Compounds are in pure form such Compounds are in pure form such as Cas C33S & CS & C22SS

3)3) Presence of minor compounds are Presence of minor compounds are ignored.ignored.

4)4) Ferrite phase can be calculated as Ferrite phase can be calculated as CC44AFAF

5)5) All oxides in the kiln have taken All oxides in the kiln have taken part in forming the compounds.part in forming the compounds.

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

%C%C22S=2.867(%S)-0.7544(%CS=2.867(%S)-0.7544(%C33S)S)

%C%C33A=2.650(%A)-1.692(%F)A=2.650(%A)-1.692(%F)

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

Ex:Ex:Given the following oxide composition Given the following oxide composition of a portland cement clinker.of 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 Bogue’s eqn’s calculate the Using Bogue’s eqn’s calculate the compound composition of the P.C. compound composition of the P.C. clinker?clinker?

CC33S=4.071*64.9-7.6*22.2-6.718*5.8-S=4.071*64.9-7.6*22.2-6.718*5.8-1.43*3.1=52.1%1.43*3.1=52.1%

CC22S=2.876*22.2-0.7544*52.1=24.5%S=2.876*22.2-0.7544*52.1=24.5%

CC33A=2.65*5.8-1.692*3.1=10.1%A=2.65*5.8-1.692*3.1=10.1%

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

To see the effect of change in oxide To 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% & composition, assume that CaO is 63.9% & SiOSiO22 is 23.2% and others are the same. is 23.2% and others are the same.

CC33S=40.4% , CS=40.4% , C22S=36.2% , CS=36.2% , C33A=10% , A=10% , 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 than resulted in more than 10% change in C10% change in C33S & CS & C22S content.S content.

Influence of Compound Influence of Compound Composition on Composition on

Characteristics of P.C.Characteristics of P.C. P.C.+waterP.C.+water→the compounds in the cement →the compounds in the cement

undergo chemical reactions with the water undergo chemical reactions with the water independently, and different products result from independently, and different products result from these 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

ASTM Type & Name of P.C.

Average Compound Composition

 C3S C2S C3A C4AF

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

Type II - Modified 46 29 6 12For 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 C3A≤5%, 2C3A+C4AF≤25%

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

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

As water comes into contact with As water comes into contact with cement particles, hydration reactions cement particles, hydration reactions immediately starts at the surface of the immediately starts at the surface of the particles. Although simple hydrates such particles. Although simple hydrates such as C-H are formed, process of hydration as C-H are formed, process of hydration is a complex one and results in is a complex one and results in reorganization of the constituents of reorganization of the constituents of original compounds to form new original compounds to form new hydrated compounds.hydrated compounds.

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

Hydrates of various compounds Hydrates of various compounds referred to collectively as GEL.referred to collectively as GEL.

Crystals of calcium hydroxide (CH).Crystals of calcium hydroxide (CH). Some minor compound hydrates.Some minor compound hydrates. Unhydrated cementUnhydrated cement The residual of water filled spaces – The residual of water filled spaces –

pores.pores.

As the hydration proceeds the deposits As the hydration proceeds the deposits of hydrated products on the original of hydrated products on the original cement grains makes the diffusion of cement grains makes the diffusion of water to unhydrated nucleus more & water to unhydrated nucleus more & more difficult. Thus, the rate of more difficult. Thus, the rate of hydration decreases with time & as a hydration decreases with time & as a result hydration may take several years.result hydration may take several years.

Major compounds start to produce:Major compounds start to produce: Calcium-silicate-hydrate gelsCalcium-silicate-hydrate gels Calcium hydroxide Calcium hydroxide

cementcement Calcium-alumino-sulfohydrates Calcium-alumino-sulfohydrates

gelgel

At the beginning of mixing, the paste At the beginning of mixing, the paste has a structure which consists of has a structure which consists of cement particles with water-filled cement particles with water-filled space between them. As hydration space between them. As hydration proceeds, the gels are formed & they proceeds, the gels are formed & they occupy some of this space.occupy some of this space.

1cc of cement 1cc of cement → 2.1cc of gel→ 2.1cc of gel

Gel Pores: Gel Pores: 28% of the total gel volume have 28% of the total gel volume have diameter of 0.015-0.020 diameter of 0.015-0.020 μμm. (very small-loss m. (very small-loss or gain of water is difficult)or gain of water is difficult)

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

Volume of capillary pores decreases as Volume of capillary pores decreases as hydration takes place. Water in capillary pores hydration takes place. Water in capillary pores is mobile, can not be lost by evaporation or is mobile, can not be lost by evaporation or water can get into the pores. They are mainly water can get into the pores. They are mainly responsible for permeability.responsible for permeability.

- w/c ratio- w/c ratio

capillary porositycapillary porosity

- degree of hydration - degree of hydration

CC22S & CS & C33S: S: 70-80% of cement is composed 70-80% of cement is composed of these two compounds & most of the of these two compounds & most of the strength giving properties of cement is strength giving properties of cement is controlled by these compounds.controlled by these compounds.

Upon hydration both calcium-silicates result Upon hydration both calcium-silicates result in the same products.in the same products.

2C2C33S+6H S+6H → C→ C33SS22HH33 + 3CH + 3CH

2C2C22S+4H → CS+4H → C33SS22HH33 + CH + CH

Calcium-Silicate-Hydrate (C-S-H gel) is similar to Calcium-Silicate-Hydrate (C-S-H gel) is similar to a mineral called “TOBERMORITE”. As a result it a mineral called “TOBERMORITE”. As a result it is named as “TOBERMORITE GEL”is named as “TOBERMORITE GEL”

Upon hydration CUpon hydration C33S & CS & C22S, CH also forms S, CH also forms which becomes an integral part of which becomes an integral part of hydration products. CH does not hydration products. CH does not contribute very much to the strength of contribute very much to the strength of portland cement.portland cement.

CC33S having a faster rate of reaction S having a faster rate of reaction accompanied by greater heat generation accompanied by greater heat generation developes early strength of the paste. developes early strength of the paste. On the other hand, COn the other hand, C22S hydrates & S hydrates & hardens slowly so results in less heat hardens slowly so results in less heat generation & developes most of the generation & developes most of the ultimate strength.ultimate strength.

Higher CHigher C33SS→higher early strength-higher →higher early strength-higher heat generation (roads, cold environments)heat generation (roads, cold environments)

Higher CHigher C22S→lower early strength-lower S→lower early strength-lower heat generation (dams)heat generation (dams)

CC33AA: is characteristically fast reacting with : is characteristically fast reacting with water & may lead to a rapid stiffening of the water & may lead to a rapid stiffening of the paste with a large amount of the heat paste with a large amount of the heat generation (Flash-Set)-(Quick-Set). In order generation (Flash-Set)-(Quick-Set). In order to prevent this rapid reaction gypsum is to prevent this rapid reaction gypsum is added to the clinker. Gypsum, Cadded to the clinker. Gypsum, C33A&water A&water react to form relatively insoluble Calcium-react to form relatively insoluble Calcium-Sulfo-Aluminates. Sulfo-Aluminates.

CC33A+CA+CŚŚHH22+10H+10H→C→C44AAŚŚHH1212 (calcium- (calcium- alumino-monosulfohydrate)alumino-monosulfohydrate)

CC33A+3CA+3CŚŚHH22+26H+26H→C→C66AAŚŚ33HH3232 (calcium- (calcium-alumino-trisulfohydrate “ettringite”)alumino-trisulfohydrate “ettringite”)

When there is enough gypsum “ettringite” When there is enough gypsum “ettringite” forms with great expansionforms with great expansion

If there is no gypsumIf there is no gypsum→flash-set→flash-set more gypsum→ettringitemore gypsum→ettringite formation increasesformation increases which will cause crackingwhich will cause cracking

Also Calcium-Sulfo Aluminates are prone (less Also Calcium-Sulfo Aluminates are prone (less resistant) to sulfate attack & does not resistant) to sulfate attack & does not contribute much for strength. The cement to contribute much for strength. The cement to be used in making concretes that are going to be used in making concretes that are going to be exposed to soils or waters that contain be exposed to soils or waters that contain sulfates should not contain more than 5% Csulfates should not contain more than 5% C33A.A.

CC44AFAF: The hydration of ferrite phase is not well : The hydration of ferrite phase is not well understand. Ferrite phase has lesser role in understand. Ferrite phase has lesser role in development of strength. The hydration development of strength. The hydration products are similar to Cproducts are similar to C33A. Alumina & iron A. Alumina & iron oxide occur interchangebly in the hydration oxide occur interchangebly in the hydration products.products.

CC44AAŚŚHH1212 or C or C44FFŚŚHH1212

CC66AAŚŚ33HH3232 or C or C66FFŚŚ33HH3232

HEAT OF HYDRATIONHEAT OF HYDRATION Hydration process of cement is accompanied Hydration process of cement is accompanied

by heat generation (exothermic).by heat generation (exothermic). As concrete is a fair insulator, the generated As concrete is a fair insulator, the generated

heat in mass concrete may result in heat in mass concrete may result in expansion & cracking. This could be expansion & cracking. This could be overcome by using suitable cement type.overcome by using suitable cement type.

It could also be advantages for cold It could also be advantages for cold wheather concreting.wheather concreting.

The heat of hydration of OPC is on the order The heat of hydration of OPC is on the order of 85-100 cal/gr.of 85-100 cal/gr.

About 50% of this heat is liberatedwithin 1-3 About 50% of this heat is liberatedwithin 1-3 days & 75% within 7 days.days & 75% within 7 days.

By limiting CBy limiting C33S&CS&C33A content heat of A content heat of hydration can be reduced.hydration can be reduced.

Heat of Hydration of Pure Heat of Hydration of Pure CompoundsCompounds

 

Heat of Hydration

(cal/gr)

C3S 120

C2S 62

C3A 207

C4AF 100

The amount of heat The amount of heat liberated is affected liberated is affected by the fractions of the by the fractions of the compounds of the compounds of the cement.cement.

Heat of Heat of Hydration(cal/gr)=120Hydration(cal/gr)=120*(%C*(%C33S)+62*(%CS)+62*(%C22S)S)+207*(%C+207*(%C33A)A)+100*(C+100*(C44AF)AF)

FINENESS OF CEMENTFINENESS OF CEMENT

As hydration takes place at the surface As hydration takes place at the surface of the cement particles, it is the of the cement particles, it is the surface area of cement particles which surface area of cement particles which provide the material available for provide the material available for hydration. The rate of hydration is hydration. The rate of hydration is controlled by fineness of cement. For a controlled by fineness of cement. For a rapid rate of hydration a higher rapid rate of hydration a higher fineness is necessary.fineness is necessary.

However,However,

Higher fineness requires higher Higher fineness requires higher grinding (cost )grinding (cost )

Finer cements deteriorate faster Finer cements deteriorate faster upon exposure to atmosphere.upon exposure to atmosphere.

Finer cements are very sensitive to Finer cements are very sensitive to alkali-aggregate reaction.alkali-aggregate reaction.

Finer cements require more gypsum Finer cements require more gypsum for proper hydration.for proper hydration.

Finer cements require more water.Finer cements require more water.

Fineness of cement is determined by Fineness of cement is determined by air permeability methods. For air permeability methods. For example, in the Blaine air example, in the Blaine air permeability method a known volume permeability method a known volume of air is passed through cement. The of air is passed through cement. The time is recorded and the specific time is recorded and the specific surface is calculated by a formula.surface is calculated by a formula.

Fineness is expressed in terms of Fineness is expressed in terms of specific surface of the cement specific surface of the cement (cm(cm22/gr). For OPC specific surface is /gr). For OPC specific surface is 2600-3000 cm2600-3000 cm22/gr./gr.

Blaine Apparatus

Sieving

SETTINGSETTING

Setting refers to a change from liquid state Setting refers to a change from liquid state to solid state. Although, during setting to solid state. Although, during setting cement paste acquires some strength, cement paste acquires some strength, setting is different from hardening.setting is different from hardening.

The water content has a marked effect on The water content has a marked effect on the time of setting. In acceptance tests for the time of setting. In acceptance tests for cement, the water content is regulated by cement, the water content is regulated by bringing the paste to a standard condition bringing the paste to a standard condition of wetness. This is called “normal of wetness. This is called “normal consistency”.consistency”.

Normal consistency of O.P.C. Ranges from Normal consistency of O.P.C. Ranges from 20-30% by weight of cement.20-30% by weight of cement.

Vicat apparatus is used to determine normal Vicat apparatus is used to determine normal consistency. Normal consistency is that consistency. Normal consistency is that condition for which the penetration of a condition for which the penetration of a standard weighed plunger into the paste is standard weighed plunger into the paste is 10mm in 30sec. By trial & error determine 10mm in 30sec. By trial & error determine the w/c ratio.the w/c ratio.

In practice, the terms initial set&final set are In practice, the terms initial set&final set are used to describe arbitrary chosen time of used to describe arbitrary chosen time of setting. Initial set indicates the beginning of setting. Initial set indicates the beginning of a noticeable stiffening & final set may be a noticeable stiffening & final set may be regarded as the start of hardening (or regarded as the start of hardening (or complete loss of plasticity). complete loss of plasticity).

Vicat Needle

Gillmore Needle

Setting can be obtained by using the Setting can be obtained by using the vicat apparatus.vicat apparatus.

Initial setting Initial setting timetime>>45min45min

ASTM C150ASTM C150

Final setting Final setting timetime<<375min375min

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

Final Final << 8hr (480min) 8hr (480min)

Factors Affecting Setting Factors Affecting Setting TimeTime

Temperature & HumidityTemperature & Humidity Amount of WaterAmount of Water Chemical Composition of CementChemical Composition of Cement Fineness of Cement (finer cement, Fineness of Cement (finer cement,

faster setting)faster setting)

Flash-setFlash-set Abnormal SettingsAbnormal Settings

False-setFalse-set

Flash-SetFlash-Set: is the immediate stiffening of cement : is the immediate stiffening of cement paste in a few minutes after mixing with paste in a few minutes after mixing with water. It is accompanied by large amount of water. It is accompanied by large amount of heat generation upon reaction of C3A with heat generation upon reaction of C3A with water.water.

Gypsum is placed in cement to prevent flash-Gypsum is placed in cement to prevent flash-set. The rigidity can not be overcome & set. The rigidity can not be overcome & plasticity may not be regained without plasticity may not be regained without addition of water.addition of water.

Amount of gypsum must be such that it will Amount of gypsum must be such that it will be used upto almost hardening. Because be used upto almost hardening. Because expansion caused by ettringite can be expansion caused by ettringite can be distributed to the paste before hardening. distributed to the paste before hardening. More gypsum will cause undesirable More gypsum will cause undesirable expansion after hardening. expansion after hardening.

False-SetFalse-Set: is a rapid development of rigidity of : is a rapid development of rigidity of cement paste cement paste without generation of much without generation of much heat.heat. This rigidity can be overcome & This rigidity can be overcome & plasticity can be regained by further mixing plasticity can be regained by further mixing without addition of water. In this way cement without addition of water. In this way cement paste restores its plasticity & sets in a normal paste restores its plasticity & sets in a normal manner without any loss of strength.manner without any loss of strength.

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

1)1) When gypsum is ground by too hot of a When gypsum is ground by too hot of a clinker, gypsum may be dehydrated into clinker, gypsum may be dehydrated into hemihydrate (CaSOhemihydrate (CaSO44.1/2H.1/2H22O) or anhydrate O) or anhydrate (CaSO(CaSO44). These materials when react with ). These materials when react with water gypsum is formed, which results in water gypsum is formed, which results in stiffening of the paste.stiffening of the paste.

2)2) Alkali oxides in cement may Alkali oxides in cement may carbonate during storage. Upon carbonate during storage. Upon mixing such a cement with water, mixing such a cement with water, these alkali carbonates will react with these alkali carbonates will react with Ca(OHCa(OH22) (CH-Calcium Hydroxide) ) (CH-Calcium Hydroxide) liberated by hydrolysis of Cliberated by hydrolysis of C33S S resulting in CaCOresulting in CaCO33. CaCO. CaCO33 precipates precipates in the mix & results in false-set.in the mix & results in false-set.

SOUNDNESS OF CEMENTSOUNDNESS OF CEMENT Soundness is defined as the volume stability of Soundness is defined as the volume stability of

cement paste.cement paste.

The cement paste should not undergo large changes The cement paste should not undergo large changes in volume after it has set. Free CaO&MgO may result in volume after it has set. Free CaO&MgO may result in unsound cement. Upon hydration C&M will form in unsound cement. Upon hydration C&M will form CH&MH with volume increase thus cracking.CH&MH with volume increase thus cracking.

Since unsoundness is not apparent until several Since unsoundness is not apparent until several months or years, it is necessary to provide an months or years, it is necessary to provide an accelerated method for its determination.accelerated method for its determination.

1)1) Lechatelier Method: Only free CaO can be Lechatelier Method: Only free CaO can be determined.determined.

2)2) Autoclave Method: Both free CaO&MgO can be Autoclave Method: Both free CaO&MgO can be determined. determined.

STRENGTH OF CEMENTSTRENGTH OF CEMENT

Strength tests are not carried out on Strength tests are not carried out on neat cement pastes, because it is neat cement pastes, because it is very difficult to form these pastes very difficult to form these pastes due to cohesive property of cement.due to cohesive property of cement.

Strength tests are carried out on Strength tests are carried out on cement mortar prepared by standard cement mortar prepared by standard gradation (1 part cement+3 parts gradation (1 part cement+3 parts sand+1/2 part water)sand+1/2 part water)

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

σσtt=P/1in=P/1in22

Difficult test procedureDifficult test procedure

PP

1”

1”

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

σσf=(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.

P

L

4cm

4cm

C

3)3) Compression Test:Compression Test:

i) Cubic Sample ii)Flexural Sample after it i) Cubic Sample ii)Flexural Sample after it is brokenis broken

P

P

σc=P/A

4cm

4cm4cm

σc=P/A

A=4x4

TYPES OF PORTLAND TYPES OF PORTLAND CEMENTCEMENT

Cements of different chemical Cements of different chemical composition & physical characteristics composition & physical characteristics may exhibit different properties when may exhibit different properties when hydrated. It should thus be possible to hydrated. It should thus be possible to select mixtures of raw materials for select mixtures of raw materials for the production of cements with various the production of cements with various properties.properties.

In fact several cement types are In fact several cement types are available and most of them have been available and most of them have been developed to ensure durability and developed to ensure durability and strength properties to concrete.strength properties to concrete.

It should also be mentioned that obtaining It should also be mentioned that obtaining some special properties of cement may some special properties of cement may lead to undesirable properties in another lead to undesirable properties in another respect. For this reason a balance of respect. For this reason a balance of requirements may be necessary and requirements may be necessary and economic aspects should be considered.economic aspects should be considered.

1)1) Standard TypesStandard Types: these cements comply : these cements comply with the definition of P.C., and are with the definition of P.C., and are produced by adjusting the proportions of produced by adjusting the proportions of four major compounds.four major compounds.

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

Standard Cements (ASTM)Standard Cements (ASTM) Type IType I: Ordinary Portland Cement: Ordinary Portland Cement

Suitable to be used in general concrete Suitable to be used in general concrete construction when special properties are construction when special properties are not required.not required.

Type IIType II: Modified Portland Cement: Modified Portland CementSuitable to be used in general concrete Suitable to be used in general concrete construction. Main difference between construction. Main difference between Type I&II is the moderate sulfate resistance Type I&II is the moderate sulfate resistance of Type II cement due to relatively low C3A of Type II cement due to relatively low C3A content (≤%8). Since Ccontent (≤%8). Since C33A is limited rate of A is limited rate of reactions is slower and as a result heat of reactions is slower and as a result heat of hydration at early ages is less. *It is hydration at early ages is less. *It is suitable to be used in small scale mass suitable to be used in small scale mass concrete like retaining walls. 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.3 days f’3 days f’cc=7 days f’=7 days f’cc of Type I of Type IIt is useful for repair works, cold weather & It is useful for repair works, cold weather & for early demolding.for early demolding.Its early strength is due to higher CIts early strength is due to higher C33S & S & CC33A content. A content.

Type IVType IV: Low Heat P.C.: Low Heat P.C.Generates less heat during hydration & Generates less heat during hydration & therefore gain of strengthis slower.therefore gain of strengthis slower.In standards a maximum value of In standards a maximum value of CC33S&CS&C33A& a minimum value for CA& a minimum value for C22S are S are placed.placed.It is used in mass-concrete and hot-It is used in mass-concrete and hot-weather concreting. weather concreting.

Type V: Type V: Sulfate Resistant P.C.Sulfate Resistant P.C.

Used in construction where concrete will Used in construction where concrete will be subjected to external sulfate attack – be subjected to external sulfate attack – chemical plants, marine & harbor chemical plants, marine & harbor structures.structures.

i)i) During hydration CDuring hydration C33A reacts with gypsum & A reacts with gypsum & water to form ettringite. In hardened water to form ettringite. In hardened cement paste calcium-alumino-hydrate can cement paste calcium-alumino-hydrate can react with calcium&alumino sulfates, from react with calcium&alumino sulfates, from external sources, to form ettringite which external sources, to form ettringite which causes expansion & cracking.causes expansion & cracking.

ii)ii) C-H and sulfates can react & form gypsum C-H and sulfates can react & form gypsum which 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 : Air Entrained Portland CementPortland Cement

Only difference is adding an air-Only difference is adding an air-entraining agent to the cement entraining agent to the cement during manufacturing to increase during manufacturing to increase freeze-thaw resistance by providing freeze-thaw resistance by providing small sized air bubbles in concrete.small sized air bubbles in concrete.

SPECIAL CEMENTSSPECIAL CEMENTS Portland Pozzolan Cement (P.P.C.)Portland Pozzolan Cement (P.P.C.) By grinding & blending P.C. By grinding & blending P.C.

Clinker+Pozzolan+GypsumClinker+Pozzolan+Gypsum P.P.C. Produces less heat of P.P.C. Produces less heat of

hydration & offers higher sulfate hydration & offers higher sulfate resistance so it can be used in resistance so it can be used in marine structures & mass concrete.marine structures & mass concrete.

However, most pozzolans do not However, most pozzolans do not contribute to strength at early ages.contribute to strength at early ages.

The early strength of PPC is less.The early strength of PPC is less.

Portland Blast Furnace Slag Cement Portland Blast Furnace Slag Cement (P.B.F.S.C.)(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 This cement is less reactive (rate of gain of

strength & early strength is less but ultimate strength & early strength is less but ultimate strength is same)strength is 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 Both P.P.C.&P.B.F.S.C. Are called blended cements. Their heat of hydration & strength cements. Their heat of hydration & strength development are low in early days. Because development are low in early days. Because upon adding water Cupon adding water C33S compounds start to S compounds start to produce C-S-Hgels & CH. The Ch & the produce C-S-Hgels & CH. The Ch & the pozzolanic material react together to produce pozzolanic material react together to produce new C-S-H gels. That’s why the early strength new C-S-H gels. That’s why the early strength is low but the ultimate strength is the same is low but the ultimate strength is the same when compared to O.P.C.when compared to O.P.C.

White Portland CementWhite Portland Cement W.P.C. İs made from materials W.P.C. İs made from materials

containing a little iron oxide & containing a little iron oxide & manganese oxide.manganese oxide.

FeFe22OO33 + MnO ≤ 0.8% + MnO ≤ 0.8% To avoid contamination by coal ash, To avoid contamination by coal ash,

oil is used as fuel.oil is used as fuel. To avoid contamination by iron To avoid contamination by iron

during grinding, instead of steel balls during grinding, instead of steel balls nickel-molybdenum alloys are used.nickel-molybdenum alloys are used.

High Alumina CementHigh Alumina Cement The raw materials for H.A.C. İs The raw materials for H.A.C. İs

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

introduced in the kiln clinkered at introduced in the kiln clinkered at 16001600°°C. Then the obtained material is C. Then the obtained material is ground to a fineness of 2500-3000 ground to a fineness of 2500-3000 cm2/gr.cm2/gr.

The oxide composition is quite differentThe oxide composition is quite different

AlAl22OO33 → 40-45%→ 40-45%

CaO → 35-42%CaO → 35-42%

FeFe22OO33 → 5-15% → 5-15%

SiOSiO22 → 4-10% → 4-10%

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

concrete made from this cement has very concrete 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 Very high early strength (emergency

repairs)repairs) About 80% of ultimate strength is obtained About 80% of ultimate strength is obtained

within 24 hours. But the strength is within 24 hours. But the strength is adversely affected by temperature. The adversely affected by temperature. The setting time is not as rapid as gain of setting time is not as rapid as gain of strength. strength.

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

STANDARD TURKISH CEMENTS STANDARD TURKISH CEMENTS (TS 19) – Cancelled(TS 19) – Cancelled

TS 19 groups them into 3TS 19 groups them into 3P.Ç. 32.5 P.Ç. 32.5 → min. Compressive strength is 32.5 MPa in → min. Compressive strength is 32.5 MPa in 28 days.28 days.P.Ç. 42.5P.Ç. 42.5P.Ç. 52.5P.Ç. 52.5

Special Cements are:Special Cements are:TS 20 –Blast Furnace Slag CementTS 20 –Blast Furnace Slag Cement

CÇ 32.5 – Cüruflu ÇimentoCÇ 32.5 – Cüruflu ÇimentoCÇ 42.5CÇ 42.5

TS 21 – White Portland Cement BPÇ 32.5-42.5TS 21 – White Portland Cement BPÇ 32.5-42.5TS22 – Masonry Cement, HÇ 16 (Harç Çimentosu)TS22 – Masonry Cement, HÇ 16 (Harç Çimentosu)TS 26 – Trass Cement, TÇ 32.5 (Traslı Çimento)TS 26 – Trass Cement, TÇ 32.5 (Traslı Çimento)TS 640 – Fly Ash Cement, UKÇ 32.5 (Uçucu Küllü TS 640 – Fly Ash Cement, UKÇ 32.5 (Uçucu Küllü Çimento)Çimento)

TS EN 197-TS EN 197-11

NEWNEWCEM cementsCEM cements

CEM I – Portland Cement

CEM II – Portland Composite Cement

CEM III – Portland Blast Furnace Slag Cement

CEM IV – Pozzolanic Cement

CEM V – Composite Cement

27 different cements

TS EN 197-1 TS EN 197-1

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

calcium-silicates calcium-silicates – 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) + Clinker + Major + Minor = 100% (mass) +

GypsumGypsum– Major > 5% by massMajor > 5% by mass– Minor Minor 5% by mass 5% by mass

TS EN 197-1TS EN 197-1Mineral AdmixturesMineral Admixtures K : ClinkerK : Clinker D : Silica FumeD : Silica Fume P : Natural PozzolanP : Natural Pozzolan Q : Calcined Natural PozzolanQ : Calcined Natural Pozzolan T : Calcined ShaleT : Calcined Shale W : Class – C Fly AshW : Class – C Fly Ash V : Class – F Fly AshV : Class – F 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 197-1TS EN 197-1CompositionComposition A : Lowest amount of mineral A : Lowest amount of mineral

admixtureadmixture B : Mineral admixture amount is > AB : Mineral admixture amount is > A C : Mineral admixture amount is > BC : Mineral admixture amount is > B

TS EN 197-1TS EN 197-1CompositionComposition

CEM I :CEM I : Portland Cement Portland Cement

95-100% 95-100% KK + 0-5% + 0-5% MinorMinor

TS EN 197-1TS EN 197-1CompositionComposition

CEM II :CEM II : Portland Composite Cement Portland Composite Cement

CEM II/A-S :CEM II/A-S : Portland Slag CementPortland Slag Cement80-94% 80-94% KK + 6-20% + 6-20% SS + 0-5% + 0-5% MinorMinor

CEM II/B-S :CEM II/B-S : Portland Slag CementPortland Slag Cement65-79% 65-79% KK + 21-35% + 21-35% SS + 0-5% + 0-5% MinorMinor

CEM II/B-P :CEM II/B-P : Portland Pozzolanic CementPortland Pozzolanic Cement65-79% 65-79% KK + 21-35% + 21-35% PP + 0-5% + 0-5% MinorMinor

CEM II/A-V :CEM II/A-V : Portland Fly Ash CementPortland Fly Ash Cement80-94% 80-94% KK + 6-20% + 6-20% VV + 0-5% + 0-5% MinorMinor

TS EN 197-1TS EN 197-1CompositionComposition

CEM III : CEM III : Portland Blast Furnace Slag Cement

CEM III/A :CEM III/A : Portland Blast Furnace Slag CementPortland Blast Furnace Slag Cement

35-64% 35-64% KK + 36-65% + 36-65% SS + 0-5% + 0-5% MinorMinor

CEM III/B :CEM III/B : Portland Blast Furnace Slag CementPortland Blast Furnace Slag Cement

20-34% 20-34% KK + 66-80% + 66-80% SS + 0-5% + 0-5% MinorMinor

CEM III/C :CEM III/C : Portland Blast Furnace Slag CementPortland Blast Furnace Slag Cement

5-19% 5-19% KK + 81-95% + 81-95% SS + 0-5% + 0-5% MinorMinor

TS EN 197-1TS EN 197-1CompositionComposition

CEM IV : CEM IV : Pozzolanic Cement

CEM IV/A :CEM IV/A : Pozzolanic CementPozzolanic Cement

65-89% 65-89% KK + 11-35% + 11-35% (D,P,Q,V,W)(D,P,Q,V,W) + 0-5% + 0-5% MinorMinor

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

45-64% 45-64% KK + 36-55% + 36-55% (D,P,Q,V,W)(D,P,Q,V,W) + 0-5% + 0-5% MinorMinor

TS EN 197-1TS EN 197-1CompositionComposition

CEM V : CEM V : CompositeComposite Cement

CEM V/A :CEM V/A : Composite CementComposite Cement

40-64% 40-64% KK + 18-30% + 18-30% SS + 18-30% + 18-30% (P,Q,V)(P,Q,V) + + 0-5% 0-5% MinorMinor

CEM V/B :CEM V/B : Composite CementComposite Cement

20-38% 20-38% KK + 31-50% + 31-50% SS + 31-50% + 31-50% (P,Q,V)(P,Q,V) + + 0-5% 0-5% MinorMinor

Strength ClassesStrength Classes

Name - ExampleName - Example

CEM II / A – P 42.5 NCEM II / A – P 42.5 N CEM II / A – P 42.5 RCEM II / A – P 42.5 R