MATERIAL

FROM QUARRY

MATERIAL

FROM QUARRY

Faculty of Postgraduates Studies for Advanced Sciences

CEMENT COURSE

Mohamed AbuelseoudAssociate Lecturer in environment and industry development department

Prepared by:

CEMENT COURSE

MATERIAL

FROM QUARRY

MATERIAL

FROM QUARRY

Faculty of Postgraduates Studies for Advanced Sciences

CEMENT COURSE

CEMENT MATERIALS CHARACTRIZATION (10 Points)

CEMENT COURSE

3CEMENT COURSE

I will be discussing….

1. Types of cement .

2. Overview.

3. Raw materials of P.C.

4. Production steps of P.C.

5. Ractions in the pre-heater& kiln.

6. Chemical composition of P.C.

7. Clinker Phases

8. Hydration of P.C.

9. Heat of Hydration.

10.Fineness of cement.

11.Soundness of cement

12.Cement and Environment

4CEMENT COURSE

1. Types of cement

Cements of different chemical composition

& physical characteristics may exhibit

different properties when hydrated. It should

thus be possible to select mixtures of raw

materials for the production of cements with

various properties.

A balance of requirements may be

necessary and economic aspects should be

considered.

5

1. CEM I Portland cement.

2. CEM II Portland-composite cement.

3. CEM III Blast furnace cement.

4. CEM IV Pozzolanic cement.

5. CEM V Composite cement.

CEMENT COURSE

1. Types of cement

MATERIAL

FROM QUARRY

MATERIAL

FROM QUARRY

2. Overview

CEMENT COURSE

Portland Cement → Gypsum+Clinker.

Portland Cement Clinker → Limestone & Clay Materials

(burning)

Paste → P.C. + Water

Mortar → P.C. + Water + Sand

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

7

3. Raw materials of P.C.

1) Calcareous Rocks (CaCO3 > 75%)o Limestoneo Marlo Marine shell deposits

2) Argillocalcareous Rocks (40%<CaCO3<75%)o Clay limestoneo Clay marlo Clay chalk

CEMENT COURSE

8

3. Raw materials of P.C.

CEMENT COURSE

3) Clays (CaCO3, SiO2 Al2O3.2H2O)

4) Iron Ore (Fe2O3)

5) Gypsum (CaSO3.2H2O)

Portland cement is made by mixing substances

containing CaCO3 with substances containing

SiO2, Al2O3, Fe2O3 and heating them to 1450 °

C where clinker formed which then ground to

powder and mixed with 2-5 % gypsum.

9CEMENT COURSE

4. Production steps of P.C.

1) Raw materials are crushed, screemed &

stockpiled.

2) Raw materials are mixed with definite

proportions to obtain “raw mix”. They are

mixed either dry (dry mixing process) or by

water (wet mixing process).

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

4) As the materials pass through the kiln their

temperature is increased from 1000-1450 °C.

The process of heating is named as “burning”.

The output is known as “clinker” which is 0.15-

5 cm in diameter.

10CEMENT COURSE

4. Production steps of P.C.

5) Clinker is cooled & stored.

6) Clinker is ground with gypsum (2-5%) to adjust

setting time.

7) Packing & marketting.

11CEMENT COURSE

Simple process diagram

12CEMENT COURSE

5. Ractions in the pre-heater& kiln.

• the burning process of raw materials isperformed in two stages: preheating upto 900°C& rotary kiln up to 1450 °C

Reactions:

~100°C→ free water evaporates.

~150-350C°→ loosely bound water is lost from clay (chemically combined).

~350-650°C→decomposition of clay→SiO2&Al2O3

13CEMENT COURSE

~600°C→decomposition of MgCO3→MgO&CO2(evaporates)

~900°C - 1100°C→decomposition ofCaCO3→CaO&CO2 (evaporates)

~1150-1280°C→liquid formation & start of compound formation.

~1280°C→clinkering begins.

~1300-1450°C→clinkering

~100°C→clinker leaves the kiln & falls into a cooler.

14CEMENT COURSE

6. Chemical composition of P.C.

Portland cement is composed of four major

oxides (CaO, SiO2, Al2O3, Fe2O3 ≥95%) &

some minor oxides. Minor refers to the quantity

not importance.

The amount of oxides in a P.C. Depend on theproportioning of the raw materials which producea certain type of cement and how well theburning is done in the kiln. The chemicalcomposition is found by chemical analysis.

15CEMENT COURSE

6. Chemical composition of P.C.

OxideCommon

Name

Abbreviati

on

Approx. Amount

(%)

CaO Lime C 60.0-67.0

SiO2 Silica S 14.0-25.0

Al2O3 Alumina A 3.0-8.0

Fe2O3 Iron-oxide F 0.1-5.0

MgO Magnesia M 0.1-4.0

Na2O Soda N0.1-1.3

K2O Potassa K

SO3

Sulfuric

Anhydride

Ś0.5-3.0

16CEMENT COURSE

CaO (C), SiO2 (S), Al2O3 (A) & Fe2O3 are the

major oxides that interact in the kiln & form the

major compounds.

The proportions of these oxides determine the

proportions of the compounds which affect the

performance of the cement.

Calcinations zone Transition zone Burning zoneLiquid zone

17CEMENT COURSE

6.1 Role of SO3 in P.C.

Gypsum added to the clinker during grinding

not only regulates the setting time but also

modifies some properties of the hardened

paste such as the mechanical strength,

shrinkage, resistance to sulfate attack and the

heat of hydration.

All of these properties represent optimum

values in relation to the given dosages of

gypsum (3.0 – 5.0 %)

SO3 → comes largely from gypsum

P.C. alone sets quickly so some gypsum is

ground with clinker to increase the setting time.

If too much gypsum is included it leads to

increase expansions of the hardened paste or

concrete.

The cement mill grinding condition:

Stander:120 °C → SO3 ≤ 3.0-5.0% in O.P.C.

18CEMENT COURSE

6.1 Role of SO3 in P.C.

MgO+H2O→MH

volume expansion cause cracking.

The cement mill grinding condition:Stander:120 °C → MgO ≤ 6.0% in O.P.C.

19CEMENT COURSE

6.2 Role of MgO in P.C.

20CEMENT COURSE

6.3 Role of Alkalies.

Alkalies (Na2O & K2O) may cause some

dificulties if the cement is used with certain

types of reactive aggregates in making

concrete. The alkalies in the form of

alkaline hydroxides can react with the

reactive silica of the aggregate & resulting

in volume expansion after hardening. This

process may take days or years.

Stander: Na2O & K2O ≤ 0.6%

21CEMENT COURSE

6.4 Role of Insoluble Residue.

It is the fraction of cement which isinsoluble in HCl. It comes mainly from thesilica which has not reacted to formcompounds during the burning process inthe kiln. All compounds of P.C. is solublein HCl except the silica.

The amount of I.R. determined bychemical analysis, serves to indicate thecompleteness of the reactions in the kiln.

Stander: I.R. ≤ 0.10% - 5.00%.

22CEMENT COURSE

6.5 Role of Loss on Ignition .

(L.O.I.): is the loss in weight of cement

after being heated to 1000°C. It indicates

the carbonation due to improper storage of

cement & clinker.

If cement is exposed to air, water & CO2

are absorbed and by heating the cement

upto 1000°C loose these two substances.

Stander: L.O.I. ≤ 5.0% for O.P.C.

The principal phases of the clinker are:

23CEMENT COURSE

7. Clinker Phases.

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

24CEMENT COURSE

7.1 Degree of Clinker Phases.

The degree to which the potential reactions

can proceed to “equilibrium” depends on:

1) Fineness of raw materials & their intermixing.

2) The temperature & time that mix is held in

the critical zone of the kiln.

3) The grade of cooling of clinker may also be

effective on the internal structure of major

compounds.

25CEMENT COURSE

7.2 Assumptions of Clinker Phases.

Calculations (Bouge’s Equations)

%C3S=4.071(%C)-7.6(%S)-6.718(%A)-

1.43(%F)-2.852(%Ś)

%C2S=2.867(%S)-0.7544(%C3S)

%C3A=2.650(%A)-1.692(%F)

%C4AF=3.043(%F)

26CEMENT COURSE

7.3 Example

Given the following oxide composition of P.C:

CaO=65.9% SiO2=22.2%

Al2O3=5.8% Fe2O3=3.1% MgO=4%

A. Using Bogue’s eqn’s calculate the

compound composition of the P.C. clinker?

B. Assume that CaO is 64.9% & SiO2 is 23.2%

and others are the same, What will be the

change in compound composition of clinker?

27CEMENT COURSE

8. Hydration of P.C.

Hydration: Chemical reactions with water.

As water comes into contact with cement

particles, hydration reactions immediately

starts at the surface of the particles.

Although simple hydrates such as C-S-H

are formed, process of hydration is a

complex one and results in reorganization

of the constituents of original compounds

to form new hydrated compounds.

28CEMENT COURSE

8.1 Hydration Process.

29CEMENT COURSE

8.2 Hydration Major products.As the hydration proceeds the deposits of

hydrated products on the original cementgrains makes the diffusion of water tounhydrated nucleus more & more difficult.Thus, the rate of hydration decreases withtime & as a result hydration may takeseveral years.

Major compounds start to produce:A. Calcium-silicate-hydrate gelsB. Calcium hydroxide C. Calcium-alumino-sulfohydrates

30CEMENT COURSE

8.3 Tobermorite Gel.

C2S & C3S: 70-80% of cement is composed ofthese two compounds & most of the strengthgiving properties of cement is controlled by thesecompounds.

Upon hydration both calcium-silicates result in the same products.2C3S+6H → C3S2H3 + 3CH2C2S+4H → C3S2H3 + CH

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

31CEMENT COURSE

8.3 Tobermorite Gel.

C3S having a faster rate of reaction

accompanied by greater heat generation

developes early strength of the paste. On the

other hand, C2S hydrates & hardens slowly

so results in less heat generation &

developes most of the ultimate strength.

32CEMENT COURSE

8.4 Role of C3A.

C3A: is fast reacting with water & may leadto a rapid stiffening of the paste with a largeamount of the heat generation (Flash-Set)-(Quick-Set). In order to prevent this rapidreaction gypsum is added to the clinker.Gypsum, C3A&water react to form relativelyinsoluble Calcium-Sulfo-Aluminates.

C3A+3CŚH2+26H→C6AŚ3H32

(calcium-alumino-trisulfohydrate “ettringite”)

33CEMENT COURSE

9. Heat of Hydration.

Hydration process of cement isaccompanied by heat generation(exothermic).

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

About 50% of this heat is liberatedwithin1-3 days & 75% within 7 days as C3S&C3Acontent decreases heat of hydration canbe reduced.

34CEMENT COURSE

9.1 Heat of Hydration equation.

Heat of Hydration (cal/gr)

=120*(%C3S)+62*(%C2S)+207*(%C3A)+100*(C4AF)

The amount of heat liberated is affected by

the fractions of the compounds of the cement.

35CEMENT COURSE

10. Fineness of cement.

As hydration takes place at the surface of

the cement particles,The rate of hydration is

controlled by fineness of cement. For a rapid

rate of hydration a higher fineness of cement

grains is necessary.

However,

•Higher fineness requires higher grinding cost.

•Finer cements require more gypsum for

hydration process.

•Finer cements require more water.

36CEMENT COURSE

10.1 Determination of cement Fineness.

Fineness of cement is determined by air

permeability methods. For example, in the

Blaine air permeability method a known

volume of air is passed through cement. The

time is recorded and the specific surface is

calculated by a formula.

Fineness is expressed in terms of specific

surface of the cement (cm2/gr). For OPC

specific surface is 2600-5000 cm2/gr.

37CEMENT COURSE

10.1 Determination of cement Fineness.

Blaine Apparatus

EN 196-6, Methods of

testing cement - Part 6:

Determination of

fineness.

38CEMENT COURSE

11. Soundness of cement.

Soundness is defined as the volume stability of cement paste.

The cement paste should not undergo largechanges in volume after it has set. FreeCaO&MgO may result in unsound cement. Uponhydration C&M will form CH&MH with volumeincrease thus cracking.

Method for its determination.

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

39

Cement and Environment

CO2 Emission

Manithabel Wastes

Agriculture Waters

Recycle of HFO.

CEMENT COURSE

12. Cement and Environment

Thank You

40CEMENT COURSE