Cements

1

CVLE 321

Structural EngineeringDepartment

Faculty of EngineeringBeirut Arab University

ByProf. Adel El Kordi

&Dr. Meheddene Machaka

THE CEMENT MANUFACTURING PROCESS

• BLASTING : The raw materials that are used to manufacture cement (mainly limestoneand clay) are blasted from the quarry.

• TRANSPORT : The raw materials are loaded into a dumper.• CRUSHING AND TRANSPORTATION : The raw materials, after crushing, are transported

to the plant by conveyor. The plant stores the materials before they are homogenized.

Quarry face

. BLASTING . TRANSPORT1- quarry

. CRUSHING & TRANSPORTATION

crushing

conveyor

dumper

storage atthe plant

loader

2

THE CEMENT MANUFACTURING PROCESS

2- Raw grinding and burning

. BURNING

• RAW GRINDING : The raw materials are very finely ground to produce the raw mix.• BURNING : The raw mix is preheated before it goes into the kiln, which is heated by a

flame that can be as hot as 2000 °C. The raw mix burns at 1500 °C producing clinkerwhich, when it leaves the kiln, is rapidly cooled with air fans. So, the raw mix is burntto produce clinker : the basic material needed to make cement.

kiln

cooling

preheating

clinker

3

. RAW GRINDING

THE CEMENT MANUFACTURING PROCESS

.GRINDING : The clinker and the gypsum are very finely ground giving a “pure cement”.Other secondary additives and cementitious materials can also be added to make ablended cement..STORAGE, PACKING, DISPATCH :The cement is stored in silos before being dispatchedeither in bulk or in bags to its final destination.

. GRINDING3- Grinding, storage, packing, dispatch

. STORAGE, PACKING, DISPATCH

clinkerstorage

Gypsum and the secondary additives are addedto the clinker.

silos

dispatch

bags

Finish grinding

4

Clinker Gypsum

5

Fe2O3

AL2O3

SiO2

CaO

OxidesC4AFC4AF

C3AC3A

C2SC2S

C3SC3S

Compounds

Background: Portland Cement ClinkerComponents,Oxides & Compounds.

6

Preparing row materialsPreparing row materials

Lime stoneCa CO3.2H2O

Lime stoneCa CO3.2H2O

Calcium OxideCa O

Calcium OxideCa O

Silicon OxideSiO2

Silicon OxideSiO2

Aluminum & Ferric OxidesFe2O3+ Al2O3+SiO3

Aluminum & Ferric OxidesFe2O3+ Al2O3+SiO3

Ferric oxideFe2O3

Ferric oxideFe2O3

Tri-calcium AluminatesC3A

Tri-calcium AluminatesC3A

Tetra calcium Aluminates FerriteC4AF

Tetra calcium Aluminates FerriteC4AF

Tri-calcium SilicateC3S

Tri-calcium SilicateC3S

Di-calciumSilicateC2S

Di-calciumSilicateC2S

Type I

OPC

Type I

OPC

Type II

Modified PC

Type II

Modified PC

Type III

High early PC

Type III

High early PC

Type IV

Low heat PC

Type IV

Low heat PC

Type V

SRC

Type V

SRC

SandSiO2SandSiO2

siltFe2O3+ Al2O3+Sio3+SiO2

siltFe2O3+ Al2O3+Sio3+SiO2

Iron OreFe2O3

Iron OreFe2O3

Crushing & Pre-HeatingCrushing & Pre-Heating

Weighing , kiln feeding & burningWeighing , kiln feeding & burning

Phases of clinker for different types of Portland cementsPhases of clinker for different types of Portland cements

Adding proper ratio of gypsum & grindingAdding proper ratio of gypsum & grinding

Chemical Composition & Industrial Process

7

Formation of Chemical Reactions.

Fe2O3Fe2O3 AL2O3AL2O3 CaOCaO

C4AFC4AF

SiO2SiO2 CaOCaO

C3SC3S

C2SC2S CaOCaO

AL2O3AL2O3 CaOCaO

C3AC3A

8

Effect of changes in Fe2O3on the C4AF and C3A

Fe2O3Fe2O3

C4AFC4AF

C3AC3A

9

Effect of changes in SiO2on the C2S and C3S

SiO2SiO2

C2SC2S

C3SC3S

10

Cement Compounds & Hydration

Hydration

process.

Portland Cem

ent.Portland C

ement.

Tr-calciumAluminates

C3A

Tri-calciumSilicate

C3S

Tetra calciumAluminates

Ferrite

C4AF

Di-calciumSilicate

C2S

++ Reduce

Durability

Reduce

Durability

VoidsVoids

CracksCracks

Heat ofHydrationHeat of

Hydration

Gainingcompressive

strengthForm the

pastestructure

Gel CSH

+Fill theporespaste

structure

Provide alkalineprotective

medium forsteel bars

Ca (OH)2

11

Cement Phases & rate of releasingheat of hydration.

HydrationprocessPortland C

ement.

Portland Cem

ent.

Tr-calciumAluminate

s

C3A

Tri-calciumSilicate

C3S

Di-calciumSilicate

C2S

Tetra calciumAluminates

Ferrite

C4AF

800

750710

420380

330

170130

80 13080

40

da y 3 da y 7 da y 2 812

Effect of Heat of hydration on durabilityCalories Per Gram

FatFat

StarchStarch

SugarsSugars

ProteinsProteins

Type IIType II

Type IType I 80 (7d.)

63 (7d.)

4

4

9

4

Cement heat of hydration is one of the most important factors

affecting durability as it increases generation of cracks in concrete and

causes concrete deterioration specially in the aggressive media.13

Hydration of cement phases.

3days 7days 28days

Hydration process.

Portland Cem

ent.Portland C

ement.

Di-calciumSilicate C2S

CSHCSH

+CHCH

Tetra calciumAluminatesFerriteC4AF

ultimatecompressivestrengthstarting from28days

Earlycompressivestrength3days &7days

Tri-calcium Silicate C3S

EttringiteEttringite

Mono( sulfate)

phases

Mono( sulfate)

phases

EttringiteEttringite

Mono( sulfate)

phases

Mono( sulfate)

phases

Setting ofcement paste

Setting ofcement paste

Setting ofcement paste

Setting ofcement paste

Tr-calciumAluminatesC3A

14

Heat of Hydration of Pure Compounds

Heat ofHydration

(cal/gr)

C3S 120

C2S 62

C3A 207

C4AF 100

• The amount of heatliberated is affected bythe fractions of thecompounds of thecement.

• Heat of Hydration(cal/gr)=• 120*(%C3S)+62*(%C2S)+

207*(%C3A)+100*(C4AF)

The requirement of ASTM C 150 varies in thethree types of cement as follows :

1. The content Of C3A .

2. The Content of SO3.

For type II chemical analysis is more restrict consenting defining the content of eachof:

• Silicone oxide 20% minimum,• Aluminum oxide & ferric Oxide that are 6% maximum• Summation of contents of the component C3S & Component C3A is 58 %

maximum

Type II production needs more accuracy in Quality control

as it is more restricted in its components

Type I OPCType IIType V SRC

5% 8%

Type I OPCType IIType V SRC

2.5% 3% 3.5 %

C3A

SO3

16

Effects of cement chemical components & physicalproperties on concrete properties

Cement EffectsPlace ability Cement amount, fineness, setting characteristics

Strength Cement composition (C3S, C2S and C3A), loss on ignition,fineness

Drying Shrinkage SO3 content, cement compositionPermeability Cement composition, finenessResistance to sulfate C3A contentResistance toChlorides C3A content

Alkali SilicaReactivity

Alkali content

Cracking Cement content, Heat of hydration, C3A, C3S, air entrainedCorrosion ofembedded

Cement Composition (esp. C3A content) steel

C3A content is the most important component affecting properties of concrete .17

Cement Hydration

18

Cementtype Use

I1 General purpose cement, when there are no extenuating conditions

II2 Aids in providing moderate resistance to sulfate attack

III When high-early strength is required

IV3 when low heat of hydration is required`V4 When high sulfate resistance is requiredIA4 A type I cement containing an integral air-entraining agent

IIA4 A type II cement containing an integral air-entraining agent

IIIA4 A type III cement containing an integral air-entraining agent

Portland cement types and their uses:)150Types of PC (ASTM C

1 Cements that simultaneously meet requirements of Type I and Type II are also widely available.2 Type II low alkali (total alkali as Na2O < 0.6%) is often specified in regions where aggregates susceptible to alkali-silica reactivity are employed.3 Type IV cements are only available on special request.4 These cements are in limited production and not widely available.19

Standard Cements (ASTM)• Type I: Ordinary Portland Cement• Suitable to be used in general concrete

construction when special properties are notrequired.

• Type II: Modified Portland Cement• Suitable to be used in general concrete

construction. Main difference between TypeI&II is the moderate sulfate resistance ofType II cement due to relatively low C3Acontent (≤%8). Since C3A is limited rate ofreactions is slower and as a result heat ofhydration at early ages is less. *It is suitableto be used in small scale mass concrete likeretaining walls.

Type III: High Early Strength P.C.Strength development is rapid.3 days f’c=7 days f’c of Type IIt is useful for repair works, cold weather

& for early demolding.Its early strength is due to higher C3S &

C3A content.

Type IV: Low Heat P.C.Generates less heat during hydration &

therefore gain of strengthis slower.In standards a maximum value of

C3S&C3A& a minimum value for C2S are placed.It is used in mass-concrete and hot-

weather concreting.

Type IIIHigh EarlyStrengthCements

22

Moderate and LowHeat Cements

23

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

be subjected to external sulfate attack –chemical plants, marine & harbor structures.

• During hydration C3A reacts with gypsum &water to form ettringite. In hardened cementpaste calcium-alumino-hydrate can reactwith calcium&alumino sulfates, from externalsources, to form ettringite which causesexpansion & cracking.

• C-H and sulfates can react & form gypsumwhich again causes expansion & cracking.

• * In Type V C3A is limited to 5%.

Type II & Type VSulfate Resistant

Cements

25

Outdoor Sulfate TestType V CementW/C-ratio = 0.65

Type V CementW/C-ratio = 0.39

26

Type IA, IIA, IIIA: Air Entrained PortlandCement

Only difference is adding an air-entraining agent to the cement duringmanufacturing to increase freeze-thawresistance by providing small sized airbubbles in concrete.

28

ASTM Type & Nameof P.C.

Average CompoundComposition

C3S C2S C3A C4AF

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

Type II - Modified 46 29 6 12For Moderate Heat ofHydration

Type III - High EarlyStrength 56 15 12 8

C3S&C3A increased, C2Sdecreased

Type IV - Low HeatP.C. 30 46 5 13 C2S increased

Type V - SulfateResistant P.C. 43 36 4 12

Limit on C3A≤5%,2C3A+C4AF≤25%

SEMs of HardenedCement Paste

30

Scanning Electron Micrograph ofPowdered Cement

31

Fineness of cement

ofsurfaceAs hydration takes place at thesurface areathe cement particles, it is the

of cement particles which provide thematerial available for hydration. The rate of

by fineness ofcontrolledhydration iscement. For a rapid rate of hydration ahigher fineness is necessary.

However,• Finer cements requires higher grinding

(cost )• Finer cements deteriorate faster upon

exposure to atmosphere.• Finer cements are very sensitive to

alkali-aggregate reaction.• Finer cements require more gypsum for

proper hydration.• Finer cements require more water.

• Fineness of cement is determined byair permeability methods. For example,in the Blaine air permeability method aknown volume of air is passed throughcement. The time is recorded and thespecific surface is calculated by aformula.

• Fineness is expressed in terms ofspecific surface of the cement (cm2/gr).For OPC specific surface is 2600-3000cm2/gr.

Blaine Apparatus

Sieving

setting• Setting refers to a change from liquid state to

solid state. Although, during setting cementpaste acquires some strength, setting isdifferent from hardening.

• The water content has a marked effect on thetime of setting. In acceptance tests forcement, the water content is regulated bybringing the paste to a standard condition ofwetness. This is called “normal consistency”.

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

• Vicat apparatus is used to determine normalconsistency. Normal consistency is thatcondition for which the penetration of astandard weighed plunger into the paste is10mm in 30sec. By trial & error determine thew/c ratio.

• In practice, the terms initial set&final set areused to describe arbitrary chosen time ofsetting. Initial set indicates the beginning of anoticeable stiffening & final set may beregarded as the start of hardening (orcomplete loss of plasticity).

Consistency of Cement Paste

ASTM C 187Vicat plunger

38

Setting Time

ASTM C 191Vicat apparatus

39

Vicat Needle

Gillmore Needle

• Setting can be obtained by using the vicatapparatus.

• Initial setting time>45min• ASTM C150• Final setting time<375min

• Initial > 1hr (60min)• TS 19• Final < 8hr (480min)

Factors Affecting Setting Time

• Temperature & Humidity• Amount of Water• Chemical Composition of Cement• Fineness of Cement (finer cement,

faster setting)

Flash-set• Abnormal Settings

False-set

• Flash-Set: is the immediate stiffening ofcement paste in a few minutes after mixingwith water. It is accompanied by largeamount of heat generation upon reaction ofC3A with water.

• Gypsum is placed in cement to preventflash-set. The rigidity can not be overcome &plasticity may not be regained withoutaddition of water.

• Amount of gypsum must be such that it willbe used upto almost hardening. Becauseexpansion caused by ettringite can bedistributed to the paste before hardening.More gypsum will cause undesirableexpansion after hardening.

• False-Set: is a rapid development of rigidity ofcement paste without generation of much heat.This rigidity can be overcome & plasticity canbe regained by further mixing without additionof water. In this way cement paste restores itsplasticity & sets in a normal manner without anyloss of strength.

• Probable Causes of False-Set:

• When gypsum is ground by too hot of a clinker,gypsum may be dehydrated into hemihydrate(CaSO4.1/2H2O) or anhydrate (CaSO4). Thesematerials when react with water, gypsum isformed, which results in stiffening of the paste.

Setting Times for Portland Cements

45

Soundness of Cement• Soundness is defined as the volume stability of

cement paste.• The cement paste should not undergo large changes

in volume after it has set. Free CaO&MgO may resultin unsound cement. Upon hydration C&M will formCH&MH with volume increase thus cracking.

• Since unsoundness is not apparent until severalmonths or years, it is necessary to provide anaccelerated method for its determination.

• Lechatelier Method: Only free CaO can be determined.• Autoclave Method: Both free CaO&MgO can be

determined.

Soundness Test

ASTM C 151 (AASHTO T 107)47

Consistency of Mortar

ASTM C 230 and ASTM C 1437Flow table

48

Strength of Cement• Strength tests are not carried out on

neat cement pastes, because it is verydifficult to form these pastes due tocohesive property of cement.

• Strength tests are carried out oncement mortar prepared by standardgradation (1 part cement+3 partssand+1/2 part water)

Mortar Cubes ASTM C 109

50

Direct Tension (Tensile Strength):

• σt=P/1in2

• Difficult test procedure

PP

1”

1”

Flexural Strength (tensile strength in bending):

• σf=(M*C)/I• M:maximum moment• I:moment of inertia• C:distance to bottom fiber from C.G.

P

L

4cm

4cm

C

Compression Test:

i) Cubic Sample ii)Flexural Sample after itis broken

P

P

σc=P/A

4cm

4cm4cm

σc=P/A

A=4x4

Strength Development of Mortar Cubes

56

Density of Cement

Le Chatelier flask ( ASTM C 188)57

58

European Standard EN 197

Cement

CEM I CEM II CEM III CEM IV CEM V

A B AC AB B

Sslag

DSilicafume

Ppozzolana

QCalcined -pozzolana

VSiliceous

Fly ash

WCalcareous

Fly ash

TBurntshale

LLime

stone

LLPureLimestone

MAll

types

A B59

60

European Standard EN 197

European Standard EN 197

Cement Component1. Main component2. Minor additional constituents3. Calcium sulphate4. Additives

61

TS EN 197-1Main ComponentK : ClinkerD : Silica FumeP : Natural PozzolanQ : Calcined Natural PozzolanT : Calcined ShaleW : Class – C Fly AshV : Class – F Fly AshL : Limestone (Organic compound < 0.5%)LL : Limestone (Organic compound < 0.2%)S : Granulated Blast Furnace Slag

Minor additional constituents

EN 197 allows for the inclusion of up to 5% by mass of a minoradditional constituent (or ‘mac’) in all types of cementMaterials typically used as a ‘mac’ include:

1. Finely ground limestone2. Fly Ash3. Cement kiln dust (CKD)

Example: A fly ash ‘mac’ should not beused in a Portland- fly ash cement

(CEM II/B-V)

Example: A fly ash ‘mac’ should not beused in a Portland- fly ash cement

(CEM II/B-V)

63

European Standard EN 197

Designation Description

CEM I Portland cementCEM II Portland-composite cements including:

-Portland-fly ash cement (CEM II/A-V, CEM II/B-V)-Portland-slag cement (CEM II/A-S, CEM II/B-S)-Portland-limestone cement (CEM II/A-L (LL),

CEM II/B-L (LL)CEM III Blast furnace cements (CEM III/A, CEM III/B)

CEM IV Pozzolanic cements (CEM IV/A, CEM IV/B)

CEM V Composite cements

64

CEM I Cement

Designation Name % Clinker % Minor additionalconstituents

CEM I Portlandcement

95-100 0-5

(CEM I) is not (OPC)

65

Common CEM II Cements

DesignationName Second Main

Constituent

% of Sec.Main

Constituent

%Clinker

CEM II/A-L(LL) Portland-limestone

cementLimestone

6-20 80-94CEM II/B-L(LL) 21-35 65-79

CEM II/A-D Portland-silica fume

cement

Silica fume 6-10 90-94

CEM II/A-V Portland-flyash cement Fly ash

6-20 80-94CEM II/B-V 21-35 65-79CEM II/A-P Portland-

pozolanacement

pozolana6-20 80-94

CEM II/B-P 21-35 65-79

CEM II/A-S Portland-Slag cement

Slag 6-20 80-94CEM II/B-S 21-35 65-7966

Common CEM II Cements

DesignationName Second Main

Constituent

% of Sec.Main

Constituent

%Clinker

CEM II/A-T Portland-burnt shale

cementburnt shale

6-20 80-94

CEM II/B-T 21-35 65-79

CEM II/A-M Portland-composite

cementcomposite

6-20 80-94

CEM II/B-M 21-35 65-79

67

CEM III Cements

Designation Name Second MainConstituent

% of Sec.Main

Constituent

%Clinker

CEM III/A Blastfurnacecement

Blast furnaceslag

36-65 (A) 35-64CEM III/B 66-80 (B) 20-34CEM III/C 81-95 (C ) 5-19

68

CEM IV Cements

Designation Name Second MainConstituent

% of Sec.Main

Constituent

%Clinker

CEM IV/APozzolanic

cement

Fly ash,natural

Pozzolana orsilica fume

11-35 65-89CEM IV/B 36-55 45-64

69

CEM V Cements

Designation Name AdditionalMain

Constituents

% ofAdditional

Constituents.

%Clinker

CEM V/A Compositecement Two

(18 – 30) x 2 40-64CEM V/B (31 – 50) x 2 20-38

ExampleComposite cement with:18-30% ggbs (S) and 18-30%siliceous fly ash (V) plus clinker; would bedesignated as:

CEM V/A (S-V) 32,5N

70

CEMENTS DESIGNATED

Example: CEM II/A-LL 42.5 NExample: CEM II/A-LL 42.5 NCEM II: Portland composite cement

‘A’ signifies low proportion of secondconstituent (6-20% in this case)

‘L’ or ‘LL’ signifies limestone as thesecond main constituent (‘LL’ signifieshigh purity limestone)

42.5 N: Cement strength class 42.5Normal strength development

Portland-limestone cementPortland-limestone cement71

Strength ClassesThere are three cement strength classes, based onthe minimum 28 day strength

32.5 42.5 52.5

• On basis of strength development, each class canbe divided in to:

– L: Low early strength– N: Normal strength development– R: High early strength

Example: class 32.5R 52.5N

72

Strength ClassesStrength

ClassMin.

2 DayMin.

7 DayMin.

28 DayMax.

28 Day

32.5 N - 16 32.5 52.5

32.5 R 10 - 32.5 52.5

42.5 N 10 - 42.5 62.5

42.5 R 20 - 42.5 62.5

52.5 N 20 - 52.5 -

52.5 R 30 - 52.5 -

73

Blast furnace cements(CEM III/A, CEM III/B)

StrengthClass

Min.2 Day

Min.7 Day

Min.28 Day

Max.28 Day

32.5 L - 12 32.5 52.542.5 L - 16 42.5 62.552.5 L 10 - 52.5 -

These low early strength classes applyonly to ES 4756-1/2005 CEM III cementsThese low early strength classes applyonly to ES 4756-1/2005 CEM III cements

74

Low Heat Cements

• ES 4756-1/2005 now covers some low heatcements

• ‘Low Heat’ is defined as a characteristicheat of hydration not exceeding 270 J/g(measured at 7 days (EN 196-8) or 41 hrs(EN 196-9))

• Low heat cements carry an ‘–LH’ suffix i.e.:

Example: CEM III/B 42.5R - LHExample: CEM III/B 42.5R - LH

75

Cement Properties (Class 42.5N)

Property Cement to be tested Limiting ValueInitial set All Min 60 minsSoundness All Max 10 mmLoss on ignition CEM I, CEM III Max 5.0 %Insoluble residue CEM I, CEM III Max 5.0 %

SulphateCEM I, CEM II, CEM IV,CEM V Max 3.5 %

CEM III Max 4 %Chloride All Max 0.10 %Pozzolanicity CEM IV Meets requirementsComposition All Meets requirementsHeat of hydration Low heat common

cementsMax 270 J/g

76