CEMENT

What is Cement ?

Cement is a binder.

A substance that sets and hardens independently, and can bind other materials together

A finely ground, grayish color powder.

Commonly known as: Portland cement

Binding materials

o Limeo Lime

o Cement

o Mud

Evolution of Cement

STAGE 1 : materials used before invention of cement

Clay (calcium silicate)

Calcined Gypsum mortar (calcium sulphate dihidrate)

Mixture of lime (CaCo3)

sand and water

STAGE 2 : Invention of Pozzolanic cement

Romans were the 1ST ones who developed a cement bymixing of slaked lime with pozzolana, a volcanic ash frommixing of slaked lime with pozzolana, a volcanic ash fromMountVesuvius.

This cement was called as ‘ Pozzolanic cement ‘ and wascapable of hardening under water.

STAGE 3 : Invention of Portland cement

Joseph Aspdin, a mason produced a material by firing finelyJoseph Aspdin, a mason produced a material by firing finelyground clay and limestone until the clay was calcined.

He named it as ‘ Portland cement’ in 1824

STAGE 4 : Development of Portland cement

In 1845, Isaac Johnson made the first modern PortlandCement by firing a mixture of chalk and clay at much higherCement by firing a mixture of chalk and clay at much highertemperatures

STAGE 5 : Invention of different types of Cement

As cement industry went on developing, many different types of cement with different chemical properties were started of cement with different chemical properties were started to be manufactured for variety of uses.

Cement production

o Calcium ( Lime )

Ingredients of cement

o Silicon ( Sand)

oAluminum (clay)

o Iron

o Sulphate (optional)

Raw Constituents of CementRaw Constituents of Cement

� Mixture of Alumina (Al2O3) & Silica (SiO2) = Clay

Clay is present in the proportion of 20 to 25% of total composition.

� Limestone ( CaCO3 ) = Lime

It is present in amount of 70 to 75% of total composition.

Excess of limestone slowdowns the setting process of cement

� Iron Oxide, Magnesia, Alkalies, etc.

These ingredients are present in very small quantities and are used to control special

chemical properties of cement.

Clay is present in the proportion of 20 to 25% of total composition.

Excess clay can cause cement to set down quickly..

Composition of CementComposition of Cement

The constituents of cement are present in form of compounds.

Portland cement is made of following main 4 compounds

� Tri-Calcium Silicate ( C3S )

� Di-Calcium Silicate ( C2S )

� Tri-Calcium Aluminate ( C3A )

� Tetra-Calcium Alumino ferrite ( C4AF )

Small amounts of un-combined lime and magnesia also are present, along

with alkalis and minor amounts of other elements.

Blasting and extraction of raw material.

Manufcturing of Cement

1. Blasting and extraction of raw material.

2. Crushing in small pieces

3. Raw Grinding

4. Burning (formation of clinker)

5. Final grinding with addetives

6. Packaging

Manufacturing process

Step 1 :

All the raw materials are extracted from thequarry and broken down into smaller pieces.

Step 2 :

those broken pieces of raw material along withsome additional ingredients are put in theblender and blended together

Step 3 :

The blended raw material (called the 'raw feed' or

'kiln feed' )is then crushed and fed into a rotarykiln where it reaches a temperature of about1400 C to 1500 C.

Step 4 :

The material formed in the kiln,described as 'clinker‘ (typically composedof rounded nodules between 1mm and 25mm

across.) is then passed directly to thecement mill where it is ground to a finepowder.

A small amount of Gypsum is also added during grinding to controlthe setting properties of cement.

THE CEMENT MANUFACTURING PROCESS

Quarry face

1. BLASTING 2. TRANSPORT

quarry

dumper

loader

1. BLASTING : The raw materials that are used to manufacture cement (mainly limestone and clay) are blasted

from the quarry.

3. CRUSHING AND TRANSPORTATION : The raw materials, after crushing, are

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

homogenized.

3. CRUSHING & TRANSPORTATION

2. TRANSPORT : The raw materials are loaded into a dumper.

crushing

conveyor

Next

storage at

the plant

THE CEMENT MANUFACTURING PROCESS

1. RAW GRINDING

Raw grinding and burning

conveyorRaw mix

preheating

storage at

the plant

Raw mill

1. RAW GRINDING : The raw materials are very finely ground in order to produce the raw mix.

2. BURNING

2. 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 clinker which, when it leaves the kiln, is

rapidly cooled with air fans. So, the raw mix is burnt to produce clinker : the basic material needed to

make cement. Next

kiln

cooling

Back

clinker

THE CEMENT MANUFACTURING PROCESS

1. GRINDING

Grinding, storage, packing, dispatch

clinker

storage

Gypsum and the secondary additives are added

to the clinker.

silos

Finish grinding

1.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 a blended cement.

2. STORAGE, PACKING, DISPATCH

2. STORAGE, PACKING, DISPATCH :The cement is stored in silos before being dispatched either in

bulk or in bags to its final destination.

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dispatch

bags

o Lafarge

o Binani

o J K Laxhmi

o ESSROC

Some leading cement manufacturers

Binani

o ACC

o Birla

o Ambuja

o Prism

o Ultratech

o Jaypee

Use of cement

Buildings Roads

Bridges

Dam Reservoir

Sculpture

� High compressive Strength

� Flexible & mouldable

� Easily available

Why Cement ?

� Easily available

� Easy to handle and use

� Good Binder

� Almost any kind of structure or finishing can be obtained

Ronchamp chapel -- Le Corbusier

Various forms of cement useVarious forms of cement useVarious forms of cement useVarious forms of cement useVarious forms of cement useVarious forms of cement useVarious forms of cement useVarious forms of cement use

� 1. 1. 1. 1. ConcreteConcreteConcreteConcrete

A proportioned mixture of cement, sand, aggregate and water.

Sub types

Most commonly used form of cement.

o PCC ( plain cement concrete)

o RCC ( reinforced cement concrete)

2. Plain Cement Concrete

Concrete used without any reinforcement is called PCC.

Generally used in

PlinthPlinth

Foundation bed

Bed block etc.

Thickness of PCC layer may vary

depending on the use and

proportion

Plain Cement Concrete

3. Reinforced Cement Concrete (RCC)

Concrete when reinforced with steel, is called as Reinforced Cement

Concrete. (RCC)

� Imparts Tensile and compressive

strength to structure.

� Good for going high rise.

� Reduces ground solid space, � Gives freedom of form

� Reduces ground solid space,

( compared to load bearing structures)

giving more usable area.

� Non reactive. So can be used

any where in any conditions

Formwork is the term given to either temporary or permanent molds into which concrete or similar materials are poured.

Formwork & scafoldings

poured.

In the context of concrete construction, the false work supports the shuttering moulds.

Lotus Temple -- Delhi

� 4. 4. 4. 4. MortarMortarMortarMortar

A proportioned mixture of cement, sand and water.

Used as a binder for construction materials.

� 5. Cement5. Cement5. Cement5. Cement BricksBricksBricksBricks

Bricks made from cement and fly ash

� 6. Stucco6. Stucco6. Stucco6. Stucco

It is used as decorative coating for walls and ceilings and as a sculptural and

artistic material in architecture.

� 7. Grout7. Grout7. Grout7. Grout

Mixture of water, cement, sand often color tint, andsometimes fine gravel generally used toembed rebars in masonary walls, connect sections ofPre-cast concrete fill voids, and seal joints.

Cement products

8. Pre-Cast Concrete

It is a construction product produced by casting concrete in a reusable mold or form which is then cured in a controlled environment,

transported to the construction site transported to the construction site and lifted into place

Precast pipes columns Balustradescolumns Balustrades

Precast Jalis Precast paver blocks

� Pre cast products are available in large variety. Small paver blocks

to even whole room blocks.

� Pre casting can be customized or done according to the

requirement.

Structural members like slab, column, beams etc can also be

pre-casted in factory and assembled on site

Joinery of precast slabs with column

precast slabs

Precast section

Precast wall panels

Precast wall panels

Precast section

Advantages of Pre-casting Vs in situ casting

� large number of uniform items can be manufactured together.

� Time and cost effective� Time and cost effective

� Reduces on site labor and mess

� Quality control maintained

Methods of pre-cast concrete

Pre-Tensioning: The stresses are first induced in the steel bars and

then concrete is poured

Post-Tensioning: Concrete is poured first, and then after its setting,

stresses are induced in steel bars.

Ready-mix Concrete (RMC)

Concrete that ismanufactured in a factoryor batching plant, according to a set recipe, and set recipe, and then delivered to a work site, by truck mounted transit mixers .

RMC plant Transit mixerRMC plant Transit mixer

Transit mixer working

Disadvantages of the use of cement

� Large emission of Carbon Dioxide, increasing Global warming

� Unlike Lime, Cement does not have a very long life and its strength starts decreasing after a certain point

�Non-Reusable.

Additives of cement

Some portion of cement can be replaced with above materials to reduce the quantity and cost of using of cement.

Fly ash Slag Rice husk ash

Composition of Cement

Mixing, placing & curing of cement

Properties of cement

Types of Cement

Properties of Portland CementProperties of Portland Cement

� Soundness : It refers to the ability of hardened cement paste to retain

� Fineness : It refers to the particle size of cement and affects the rate of hydration which is responsible for the rate of strength gain.Approximate size of particles is less than 45 microns up to even 15 microns.

Soundness : It refers to the ability of hardened cement paste to retain

its volume after setting.

� Consistency : It refers to the ability of cement paste to flow.

It is measured using vicar's apparatus.It depends on the water - cement ratio.

� Setting Time : Cement has two setting times.

Initial setting time is the time elapsed from the instance of adding water Initial setting time is the time elapsed from the instance of adding water to the cement until the time the paste stops behaving like a fluid.It is normally 45 minutes for OPC.

Final setting time is the time required by the cement paste to reach certain state of hardness to sustain loadIt is normally 10-12 hours for OPC.

� Compressive strength :

Strength of cement mortar varies according to time. It is generally reported

as 3 days, 7 days and 28 days strength.

� Heat of hydration :� Heat of hydration :

The heat generated during the reaction of cement and water is known as

heat of hydration.

Factors affecting heat of hydration are C3A, C2S, Water cement ratio,

fineness of cement and curing temperature.

Conduction calorimeters is used to test heat of hydration.

� Specific gravity : The relative density of OPC is found to be in the range

of 3.15 mega gram/cu.mt.

It is determined by Le- Chatelier’s apparatus.

� Bulk density : It is the ratio of total mass to the volume of cement.

Bulk density ranges from Bulk density ranges from

830 kg/cu.mt. To 1600 kg/cu.mt.

� Loss on Ignition: The weight of cement lost after it being heated is called

as the loss on ignition. Loss more than 3% indicates

pre hydration .

Steps involved in structureformation

� Mixing : Mixing of concrete and water to form a slurry

� Placing : Pouring the slurry into the formwork� Placing : Pouring the slurry into the formwork

� Hydration / Setting : Hydration means Reaction with water.

The hydration of Portland cement is the chemical reactionbetween grains of cement and water to form the hydration product, cement gelwhich can be laid down only in water-filled space

Curing can be defined as a procedure for insuring the hydration of the Portland cement in newly-placed concrete.

It generally implies control of moisture loss and sometimes of temperature.

� Curing

� Increase concrete strength

�- Increase concrete abrasion resistance

�- Lessen the chance of concrete scaling

�- Lessen the chance of surface dusting

�- Lessen the chance of concrete cracking

Following are the results of concrete

Water Curing

Membrane Curing

TYPES OF CEMENTS

�Ordinary Portland Cement

� Rapid Hardening Cement

� Sulphate Resisting Cement

�Air Entraining cement

� Coloured cement

� Hydrophobic cement

� Quick setting Cement

� Super Sulphated Cement

� Low Heat Cement

� Portland Pozollana Cement

�Masonry cement

� Rediset cement

� High alumina cement

� High early strength cement

TYPES OF PORTLAND CEMENTS

Five types of Portland cement are standardized in the United States by the

American Society for Testing and Materials (ASTM)

� Type 1 : Ordinary

� Type 2 : Modified ( Quick setting cement)Type 2 : Modified ( Quick setting cement)

� Type 3 : High Early strength

� Type 4 : Low heat

� Type 5 : Sulphate Resistant

� Ordinary Cement

• Ordinary Portland cement (OPC) is the most important type of cement.

• The OPC is classified into three grades, namely 33 grade, 43 grade and53 grade depending upon the strength of the cement at 28 days when testedas per IS 4031-1988.

(If the 28 days strength is not less than 33N/mm2,(If the 28 days strength is not less than 33N/mm2,it is called 33 grade cement, if the strength is not less than 43N/mm2, it is called 43 grade cement, and if the strength is not less than 53 N/mm2, it is called 53 grade cement).

• Most commonly used cement.

• Eg:- normal buildings, sidewalks etc.

� Quick setting Cement / Medium sulphate resistant

• This cement as the name indicates sets very early.

• The early setting property is brought out by reducing the gypsum content

at the time of clinker grinding.

• This cement is required to be mixed, placed and compacted very early.

•• It is used mostly in under water construction where pumping is involved.

Use of quick setting cement in such conditions reduces the pumping timeand makes it economical.

• Quick setting cement may also find its use in some typical grouting operations.

• Moderate sulphate resistance.

• Moderate heat of hydration

� High Early Strength. ( Rapid Hardening Cement )

� As the name indicates it develops strength rapidly.

� Rapid hardening cement develops strength at a higher rate whereas Quick setting-cement sets quickly.

� Rapid hardening cement develops at the age of three days the same strength,� Rapid hardening cement develops at the age of three days the same strength,as that is expected of ordinary Portland cement at seven days.

� The rapid rate of development of strength is attributed to the higher fineness of grinding and higher C3S and lower C2S content.

� The higher fineness of cement particles expose greater surface area for action of water and also higher proportion of C3S results in quicker hydration.

.

Uses of Rapid hardening cement:

� In pre-fabricated concrete construction.

� Where formwork is required to be removed early for reuse.

� Road repair works.

� In cold weather concrete where the rapid rate of development of strength reduces the vulnerability of concrete to the frost damage.

� Low heat cement

• It is well known that hydration of cement produces large quantity of heat during hydration.

• Formation of cracks in large body of concrete due to heat of hydration has focused the attention of the concrete technologists to produce a kind of cement which produces less heat or the same amount of heat, at a low rate during the hydration process.

• A low-heat evolution is achieved by reducing the contents of C3S and C3A which are the compounds evolving the maximum heat of hydration and increasing C2S.

• A reduction of temperature retards the chemical action of hardening and so further restrict the rate of evolution of heat.

• It is used in mass concrete construction, such as dams, where temperature rise by the heat of hydration can become excessively large.

� Sulphate Resistant Cement

� Ordinary Portland cement is susceptible to the attack of sulphates, where during setting sulphate reacts with the calcium and aluminiumfrom cement to form other compounds.

� The expansion of these other compounds in hardened cement results in crackformation in concrete structures.

� To avoid this, the use of cement with low C3A content is found to be effective.Such cement with low C3A and comparatively low C4AF content is known as Sulphate Resisting Cement.

Uses of Sulphate resisting cement:

• Concrete to be used in marine condition.

• Concrete to be used in foundation and basement, where soil is infested with sulphates.

• Concrete used for fabrication of pipes which are likely to be buried in marshy region or sulphate bearing soils.

• Concrete to be used in the construction of sewage treatment works.

There are some more types of cements commonly available and used.

� Coloured cement

� Coloured cements are made by grinding 5 to 10 percent of suitable pigments with white or ordinary gray Portland cement

� Used for Aesthetic purpose.

� Air Entraining Cement

� Air-entraining cements are made by the addition on grinding of a small amount, about 0.05 percent, of an organic agent that causes the entrainment of very fine air bubbles in a concrete

� This increases the resistance of the concrete to freeze-thaw damage in cold climates.

There are some more types of cements commonly available and used.

� Low-Alkali cement

� Low-alkali cements are Portland cements with a total content of alkalis not above 0.6 percent.

� Oil Well Cement

� Oil-well cements are used for cementing work in the drilling of oil wells where they are subject to high temperatures and pressures.

� They usually consist of Portland or Pozzolanic cement with special organic retarders to prevent the cement from setting too quickly.

� Portland Blast furnace slag cement

� The granulated slag made by the rapid chilling of suitable molten slagsfrom blast furnaces forms the basis of another group of constructional cements.

� A mixture of Portland cement and granulated slag, containing up to 65 percent slag, is known as blast furnace / slag cement.

� Properties of these slag cements are broadly similar to those of Portland cement, but they have a lower lime content and a higher silica and alumina content.

� Those with the higher slag content have an increased resistance to chemical attack.

The EndHimani S. Tawade