University of Gondar

Institute of Technology
Department of Civil Engineering

Construction Materials (CEng 2091)

Chapter two – Cementing materials

Rekik D.

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 binders
 Binders are substances that are used to bind
inorganic and organic particles and fibers to
form strong, hard and flexible components.
 The binding action is generally due to
chemical reactions which take place when the
binder is heated, mixed with water and/or
other materials, or just exposed to air.
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There are three main groups of binders:

Mineral binders
 Non hydraulic
 hydraulic
Bituminous (Asphalt) binders
Synthetic binders

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 Non hydraulic
 Non-hydraulic binders only harden in the presence
of air
 The most common non-hydraulic binder is lime.
 Gypsum is a non-hydraulic binder which occurs
naturally as a soft crystalline rock. The chemical
name is calcium sulfate anhydrate (CaS04.2H20).

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 Hydraulic binders

• Hydraulic binders require water to harden and

develop strength.

• The most common hydraulic binder is Portland

cement.

• Hydraulic binders are usually available in the form

of a fine powder

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Bituminous Materials
(Asphalt Cement)

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 Definition
Bituminous material is a class of black or
dark colored solid or viscous cementitious
substances composed chiefly of
hydrocarbons.

When mixed with aggregates in their fluid

state they solidify and bind the aggregates
together, forming a pavement surface.

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 Uses of Bituminous Materials
Bituminous materials are used:
Extensively for road construction, because of
their excellent binding or cementing power and
their water proofing properties

Used in roofing materials and as protective /

water proof coating.

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9
Asphalt Concrete

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 Asphalt Concrete
The main asphalt paving material in use today is asphalt
concrete.

 A high quality pavement surface is composed of asphalt cement,

aggregate and air, hot mixed in an asphalt plant and then hot-
laid.

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 lime
 Lime is one of the oldest known cementing
material

 Lime is found in many parts of the world in its

natural form as a rock of varying degree of
hardness.

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 Lime is mainly composed of calcium oxide
(CaO).
 Lime in its pure form associates with CO2 to
give white CaCo3.
 Lime deposits are generally found mixed with
impurities such as CO2, Fe2 O3, and MgCO3.
 Depending on the impurities, lime deposits
acquire different colors.

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 production of lime
Lime is produced by burning the raw material
limestone CaCO3.
 Chalk , shell and coal can have CaCO3 content exceeding
98 %
The limestone is burnt at approximately 1000-1300°C.
• The burning process takes place in either:
»Vertical shaft kiln
»Rotary kiln

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• Vertical shaft lime kiln

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Rotary kiln

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 clasification of lime
Commercial lime is classified into three groups:
1. Quick lime (Caustic lime)
2. Hydrated lime (Slaked lime)
3. Hydraulic lime

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 Quick lime
• The manufacturing of Non-hydraulic lime
(Commercial or building lime) consists in
burning the limestone at a temperature of
1000°c. The CO2 is driven off, leaving the CaO
which is known as quick lime or caustic lime.
CaCO3  CaO+CO2

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• Is obtained by calcining (burning) the purest available calcium carbonate
• Gives out considerable heat
• Swells two to three times of its original volume upon addition of water
• Takes much time in hardening
• Is used for plastering and white washing
• Is not suitable for being used as mortar because of its poor strength and
slow hardening
• White in color and have S.G. of about 3.4.
• Highly caustic and posses a great affinity for water.
• It must be kept in dry storage and carefully protected from dampness

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 Hydrated Lime (Slaked Lime)
Quick lime can never be used as such for construction purposes but must be
mixed with water.
The mixing of water with quick lime is called slaking or hydration of lime.

CaO+H2O Ca (OH)2 + heat

This process is called slaking and the product (calcium hydroxide) is called
slaked lime or hydrated lime.

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 types of slaking
There are two types of slaking based on the amount of water
add.
•I. Wet-slaking: An excess of water is added and the resulting
slaked lime is passed through a fine sieve to remove slow
slaking particles and then left to mature for several days.

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• Dry-slaking: It is obtained by adding almost exactly the
theoretical quantity of water required to change the burnt
lime into hydrated lime.

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 Forms of hydrated lime
Depending upon the amount of water added
during the slaking process, three forms of
hydrated lime are commonly produced:
a) Dry hydrate, a dry, fine powder, formed by
adding just enough water (Dry-Slaking) to slake
the lime, which is dried by the heat evolved;

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b) Milk of lime, made by slaking quicklime with
a large excess of water (Wet-Slaking) and
agitating well, forming a milky suspension;

c) Lime putty, a viscous mass, formed by the

settling of the solids in the milk of lime.

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 3. Hydraulic Lime
 Is prepared by burning impure limestone that
contains clay, producing compounds similar to
those present in Portland cement. It is stronger but
less fat or plastic than non-hydraulic lime.
 Hydraulic lime is manufactured in the same way
as quick lime, although a somewhat higher
temperature is required in burning

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 SETTING AND HARDENING OF LIME

• Slaked lime hardens or sets by gradually losing

its water through evaporation and absorbing
CO2 from the air, thus changing back from
Ca(OH)2 to CaCO3.
• The cycle is completed in the chemical
changes from the original limestone, through
burning, slaking, and setting as shown below.

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SETTING AND HARDENING OF LIME

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 USES OF LIME
1. Lime as a construction material
 As mortar (lime mortar) mixed with sand
 Lime is used in cement mortar to make it more workable
 As plaster (lime plaster)
 As a whitewash, when it gives a sparkling white finished
at a very low cost
 As lime concrete
 As an important constituent of sand – lime bricks
 As a stabilizer in soil constructions with clayey soils

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 2. Lime as an industrial material

In industry, lime finds many applications:

 As a flux in the metallurgical industry
 As a refractory material for lining metallurgical furnaces;
 As a raw material for the manufacture of glasses.
3. Lime as an agricultural input
Lime is used for improving the productive qualities of soils. It
is added to the poor soils to enrich their lime content.

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GYPSUM PLASTERS

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 Gypsum is
a combination of sulphate of lime with water of
crystallization. It occurs naturally as either
Hydrous sulphate of lime (CaSO4.2H2O)
which is generally 76% CaSO4 and 24%
H2O, or
Anhydrate ( CaSO4)

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• The gypsum rock usually contains silica, alumina,
lime carbonate, carbonate of magnesia, iron oxide
and other impurities.
• To be classed as gypsum rock at least 65% by
weight must be CaSO4.2H2O.
• Pure gypsum is known as alabaster and it is a
white translucent crystalline mineral, so soft that it
can be scratched with the finger nails.

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 manufacture of plasters
Gypsum plasters are manufactured by heating
 the raw material gypsum at either moderate or
high temperatures
 the results being plaster of Paris or hard finish
plaster.

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 plaster of Paris.

• Some of the water is driven off by incompletely

dehydrating pure, finely ground gypsum at a
temperature just above the boiling point of water.
• As a result a semi-hydrated plaster is obtained which is
known as plaster of Paris.
• The plaster is also known as low-temperature gypsum
derivative or semi-hydrated plaster (hemihydrates).

(CaSO4.2H2O)+Moderate Heat (CaSO4 .1/2H2O)+1/2 H2O

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• When mixed with sufficient water to form a plastic paste
it sets very rapidly, the whole process taking only 5-10
minutes. The setting time of plaster of Paris is delayed
by adding a fraction of 1% of a retardant like glue,
sawdust.

 Plaster of Paris while setting under water, does not

gain strength and ultimately, on continued water
exposure, will disintegrate.

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• Due to the rapidity of set and difficulty in
working its use in structure is limited to
ornamental work.
• It produces hard surface, sharp contours,
and is sufficiently strong.

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 Hard-finish plaster
• By burning gypsum to a considerably higher
temperature there may be produced anhydrous
sulphate which is known as anhydrous plaster or
high temperature gypsum derivative.
(CaSO4. 2H2O)+High Heat CaSO4+2H2O
• This plaster is less soluble with consequent
reluctance to absorb water in the process of
recrystallization.
• The result is a plaster too slow in setting action for
practical purposes.

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cement

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 GENERAL
• What is cement?
A finely ground inorganic material which has cohesive & adhesive
properties
able to bind two or more materials together into a solid mass.
• Cohesion is the tendency of a material to maintain its integrity without
separating or rupturing within itself when subject to external forces.
• Adhesion is the tendency of a material to bond to another material.
• Cement when mixed with water form a paste which sets and harden by
means of hydration reactions, and which after hardening retain its
strength and stability even under water.

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 History of Portland Cement
 In 1824, Joseph Aspdin, a British stonemason, obtained a patent for a
cement he produced .The inventor heated a mixture of finely ground
limestone and clay and ground the mixture into a powder create a
hydraulic cement-one that hardens with the addition of water.
 Aspdin named the product “Portland cement” because it resembled a
stone quarried on the Island of Portland of the British Coast.
• The first cement factory was established in Ethiopia in 1936 by the
Italians at the Eastern part of the country, Dire Dawa.

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Isle of Portland / British Coast

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 what is Portland cement
 Portland cement is a cementing material which is obtained by
thoroughly mixing together
 calcareous or lime bearing material e.g.. Limestone, chalk
with if required
 argillaceous silica, alumina or ironoxide bearing materials
e.g., clay, sandstone , shell . burning them at clinkering
temperature and grinding the resulting clinker.

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 Raw Materials
Portland cement is made from materials which must
contain the proper proportions of:
 lime (CaO),
 silica (SiO2),
 alumina (Al2O3),
 iron (Fe2O3)
with miner amounts of magnesia and sulfur trioxide.

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 The process of manufacture consists
essentially of:
1.crushing, grinding, proportioning and mixing
the raw material
2.Burning in rotary kiln (Clinker is produced)
3.Cooling, grinding of clinker and sieving
4.Storing, packing and distributing

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 types of process
• There are two process known as “wet” and “dry” process
depending upon whether the mixing and grinding of raw
materials is done in wet or dry condition.
• The main difference between two processes is that in dry
process the raw materials are fed into the burning kiln in a
perfectly dry state. In the wet process, however, these
materials are supplied to the kiln in the form of slurry (a liquid
of creamy consistency, with a water content of between 35 &
50%).

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 Dry Process
The four main steps in this process are:
1. Treatment of raw materials
2. Burning of the dry mix
3. Grinding of the clinker
4. Packaging and storage

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 1.Treatment of Raw Materials
• The raw materials are subjected to such processes as:
crushing, drying, grinding, proportioning and blending or
mixing before they are fed into the kiln for burning. The
crushing stage involves breaking the raw materials to small
fragments that vary in size between 6-19 mm. Primary
crusher machines are used for this purpose. The drying stage
is typical of the dry process.
• . The proportioned raw material is known as raw meal.

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 2. Burning or Calcination
• The well-proportioned finely powdered mixture (raw meal) is
charged into long steel cylinder, called rotary kiln.
• Rotary kilns differ in design and dimensions in accordance
with the production requirements. Thus, these may be 100-
180m in length, 3-5m in diameter and have rotation of 60-90
revolutions per hour.
• The raw mixture is burnt in the kiln till the proper burning is
achieved.

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• The temperature in the kiln reaches about 1200-
1500oc. This drives off water and gases and produces
new chemical compositions in particles.
• lime, silica and alumina recombine to form new
chemical compounds which fuses into balls, 10-
25mm in diameter, which is called the clinker.

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 3. Grinding of the Clinker
• The completely burnt or calcined raw materials of cement are
converted to lump-shaped product called clinker, which is drawn out
from the lower end of the rotary kiln. It is extremely hot when
discharged, and is therefore first cooled and both (clinker and gypsum)
are sent for pulverizing. The mixture is reduced to an extremely fine
powder by grinding it.

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 4. Packing and storage of cement

• Cement is most commonly stored after its

manufacture in specially designed
concrete storage tanks called silos where
from it is drawn off mechanically for the
market. For convenience, the cement
comes to the customer in bags containing
measured quantity. The standard bag of
cement as distributed in Ethiopia is
commonly 50 kg

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 Wet Process
• It is considered a better and convenient process for the
manufacture of cement, specifically where limestone of soft
variety is available in abundance. We can discuss this process
under four headings:

1. Preparation of slurry
2. Burning or calcinations and
3. Treatment of clinker
4. Packaging and storage

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 1. Preparation of Slurry
• In wet process, raw materials are supplied to the kiln in the form of an
intimate mixture with a lot of water in it. This is called slurry
• To obtain the slurry of standard composition, the raw materials are first
crushed separately using crushers for limestone and grinding mills (wet)
for clays. These crushed materials are stored in separate tanks or silos.
• They are drawn from the silos in prefixed proportions in to the wet
grinding mills where, in the presence of a lot of water, thus ground to a
fine thin paste. The slurry is stored in a silo
• Its composition is tested once again and corrected by adding limestone
slurry in required proportions such corrected slurry is then fed into the
rotary kiln.

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• PROPERTIES OF THE MAIN
COMPOUNDS IN CEMENT
CLINKER

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 The four major compounds of
cement produced are:
• 3 Ca O. SiO2 (Tricalcium silicate), C3S
• 2CaO. SiO2 (Dicalcium silicate), C2S
• 3CaO. Al2 O3 (Tricalcium Aluminate), C3A
• 4CaO. Al2O3. Fe2O3 (Tetra calcium Aluminoferrite) C4 AF
• The relative amounts of these four chemicals in the final
product depend on the desired properties such as rate of
hardening, amount of heat given off, and resistance to
chemical attack.

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 1. C3S (Tri calcium Silicate)
• The most desirable constituent is that of tricalcium
silicate (C3S),
• it hardens rapidly and accounts for the high early strength
of the cement.
• When water is added to tricalcium silicate, a rapid
reaction occurs as follows:
• 2C3S + 6H2O  3 CaO. 2SiO2. 3H2O + 3Ca (OH) 2

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• The main product, 3CaO. 2SiO2. 3H2O is calcium
silicate hydrate or to bermorite, and gives
cement its strength.
• The total amount of water required to complete
the hydration of the cement is about 25% of the
mass of the cement.
• The proportion of C3S ranges from 25-60%

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 2. C2S ( Dicalcium Silicate)
• Dicalcium silicate hardens slowly
• It contributes to strength increase at
ages beyond one week.
• In the presence of water, dicalcium
silicate (2CaO.SiO2) hydrates slowly and
forms a hydrated calcium silicate
(2CaO.SiO2. xH2O).
• The proportion of C2S ranges from 13-
50%.
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 3. C3A (Tricalcium Aluminate)
• Tricalcium aluminate liberates a large amount of
heat, (heat of hydration), during the first few
days of hardening.
• About 50% of the total heat of hydration is
released in the first three days.
• It also contributes to early- strength
development.
• Tricalcium aluminate hydrates with water to form
a hydrated tricalcium aluminate 3CaO.
Al2O3.6H2O.

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 4. C4AF (Tetracalcium Aluminoferrite)

• Tetra calcium aluminoferrite formation

reduces the clinkering temperature;
thereby assisting in the manufacture of
Portland cement.
• Contributes very little to strength.
• The proportion of C4AF ranges from 8-15%

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STANDARD TYPES OF PORTLAND CEMENT

The difference in properties of the various kinds of cement

arises from the relative proportions of the four major
compounds.
• ASTM recognizes eight types of Portland cement under
specification ASTM C150.
• The standard five types of Portland cement (this
excludes the three that are air-entrained) are the types
that are usually produced. We next investigate each type
separately.

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 Type I (Normal Portland cement)
• Normal Portland cement is general-purpose cement.
• It is used when the special properties specified for any
other type are not required.
• It is used where there would be no severe climate
changes or severe exposure to sulfate attack from water
or soil.
• Its uses include reinforced-concrete buildings,
pavements, sidewalks, bridges, railings, tanks,
reservoirs, floors, curbs, culverts, and retaining walls.
• In general, it is used in nearly all situations calling for
Portland cement.
 Type II (Moderate Portland cement)

 Moderate Portland cement is a general-purpose

cement to be used when moderate sulfate
resistance or moderate heat of hydration is
desired.
 It is used in structures of considerable mass,
such as abutments and piers and retaining walls.
 Its use also minimizes temperature rise when
concrete is placed in warm weather.
Type III (High-Early-Strength Portland cement)

• High-early-strength Portland cement is used

when high early strength is desired, usually less
than one week.
• It is usually used when a structure must be put
into service as quickly as possible.
• This cement is made by changing the
proportions of raw materials, by fine grinding,
and by better burning, such that dicalcium
silicate is less and the tricalcium silicate is
greater.
 Type IV (Low - Heat of Hydration
Portland cement)

• Low - Heat of Hydration Portland cement is used

when a low heat of hydration is required.
• This type of cement develops strength at a
slower rate than does than Type I. However, it is
intended for mass structures such as large
gravity dams where the temperature rise on a
continuous pour is great.
• If the temperature were not minimized, large
cracks or flaws would appear and the structure
might prove to be unsound.
 Type V (Sulfate - Resisting Portland cement)

• Sulfate - Resisting Portland cement is

used when high sulfate resistance is
desired. It is used when concrete is to be
exposed to severe sulfate action by soil or
water.
 Types IA, IIA, IIIA
• The three types of air - entraining cements, Types IA,
IIA, IIIA as given by ASTM C150, are used in concrete
for improved resistance to freezing and thawing action
and the action of salt scaling and chemical attack.
• Disintegration due to freezing and thawing is caused by
the expansion of the water, as it freezes. The pressure
caused by this expansion forces the pore open after
thawing; the large pore is re saturated with water and
subsequent freezing increase the pore volume again.
 What is.? air - entraining cements
• One of the greatest advances in concrete technology
was the development of air-entrained concrete in the late
1930s. Today, air entrainment is recommended for
nearly all concretes, principally to improve resistance
to freezing when exposed to water and deicing
chemicals.
• Air-entrained concrete contains billions of
microscopic air cells. These relieve internal pressure
on the concrete by providing tiny chambers for the
expansion of water when it freezes.

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• Air-entrained concrete is produced through the use of air-
entraining Portland cement, or by introducing air-
entraining admixtures under careful engineering
supervision as the concrete is mixed on the job.
• The amount of entrained air is usually between 5 percent
and 8 percent of the volume of the concrete, but may
be varied as required by special conditions.
• The use of air-entraining agents results in concrete that is
highly resistant to severe frost action and cycles of
wetting and drying or freezing and thawing (to go from
a frozen to a liquid state (melt )and has a high degree of
workability and durability.
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Types of Portland Cement Compound Composition

C3S C2 S C3A C4AF

I. Normal 50 24 11 8

II. Moderate 42 33 5 13

III. High-early-strength 60 13 9 8

IV. Low-Heat 26 50 5 12

V. Sulfate-Resisting 40 40 4 9
Types of Portland Compressive Strength
Cement (% Of Normal Portland
Cement)

1 3 7 28 3
Day Days Days Days Months

I. Normal 100 100 100 100 100

II. Moderate 75 80 85 90 100

III. High-early- 190 190 120 110 100

strength
IV. Low-Heat 55 55 55 75 100

V. Sulfate-Resisting 65 65 75 85 100
SPECIAL TYPES OF PORTLAND
CEMENT
 Portland-Pozzolana Cement (PPC)

• The term pozzolana is used to describe

naturally occurring and artificial siliceous
materials, which in themselves possess little or
no cementations value, but will, in finely divided
form and in the presence of moisture, chemically
react with calcium hydroxide at ordinary
temperatures to form compounds possessing
cementations properties.
 Portland-Pozzolana Cement (PPC)
• Portland-pozzolana cement (PPC) is manufactured by
blending 10-30% by weight of pozzolanic material with
ordinary Portland cement (OPC); either by simple
mixing or by inter -grinding with cement clinker. The
calcium hydroxide liberated during the process of
hydration of the cement combines slowly with the
pozzolana to give it cementations properties, thereby
contributing to water tightness and long continued gain
in strength of the concrete.
 What are the advantages of using Portland
pozzolana cement over OPC?
• Pozzolana combines with lime and alkali in
cement when water is added and forms
compounds which contribute to strength,
impermeability and sulphate resistance
• Pozzolana also contributes to workability,
reduced bleeding and controls destructive
expansion from alkali-aggregate reaction.
• Pozzolana reduces heat of hydration thereby
controlling temperature differentials, which
causes thermal strain and resultant cracking in
mass concrete structures like dams.
 A variety of special cements exist that are
limited for specific uses and purposes.

The following are few examples:

 White Portland Cement
 Colored Cements
 Oil-Well Cements
 Regulated cements
 Waterproofed Cement
 Hydrophobic cement
 Antibacterial cements
 Barium and Strontium cements etc.
PROPERTIES OF PORTLAND CEMENT
 Requirements for Portland cement
• Most specifications place specific physical
property and chemical composition
requirements for Portland cement.

• Physical and chemical tests are conducted

to judge the quality of cement.
 1. Physical Properties
The physical properties of Portland cement
are:
fineness,
setting time,
soundness,
compressive strength,
heat of hydration and
specific gravity.
 1.1 Fineness
• The fineness of cement has an important effect on the
rate of hydration.
• The finer the cement the quicker the rate of hydration
and the greater is the heat evolution at early ages.
• The fineness of cement can be measured in a number of
ways.
– The sieve test,
– specific surface test by Wagner Turbid meter method
– the Blaine air permeability methods
The sieve test,
 2.2 Setting time
• Setting is the term used to describe the stiffening
of the cement paste, although the definition of
the stiffness of the paste, which is considered,
set is somewhat arbitrary. Broadly speaking,
setting refers to a change from a fluid to a
rigid stage.
• Although, during setting, the paste acquires
some strength, for practical purposes it is
important to distinguish setting from
hardening, which refers to the gain of strength
of a set cement paste.
 Initial & Final Setting Times
• setting is not an abrupt process, which
may complete immediately after its start; it
is rather a progressive phenomenon,
which has beginning, full development and
an end. It is on this latter basis, setting is
distinguished into initial and final setting
qualified by the time required in each
case.
 Initial & Final Setting Times
• Initial set- Occurs when the paste begins
to stiffen considerably.

• Final set- Occurs when the cement has

hardened to the point at which it can
sustain some load.
 1.3 Soundness
• Incomplete combination of the lime with other raw
constituents through under burning of clinker, results in
free or uncombined lime (CaO) in the finished
cement. If this is present in excess amount expansion
and disruption of concrete may eventually occur.
This phenomenon is known as soundness.
• In order to determine the soundness of cement the
Le Chatelier test is used.
 1.4 Compressive strength
• The mechanical strength of hardened cement is
the property of the material that is perhaps most
obviously required for structural use.
• Strength tests are not made on a neat cement
paste because of difficulties of molding and
testing with a consequent large variability of test
results.
• Strength of cement can be determined by two
methods i.e. mortar test and concrete test.
 Heat of hydration is most influenced by:

The proportion of C3S and C3A in the cement,

Water-cement ratio,
Fineness
Curing temperature. 
As each one of these factors is increased, heat
of hydration increases. 
 1.6  Loss on Ignition
• Loss on ignition is calculated by heating up a
cement sample to 900 - 1000°C until a constant
weight is obtained.  The weight loss of the
sample due to heating is then determined.  A
high loss on ignition can indicate  prehydration
and carbonation, which may be caused by
improper and prolonged storage or adulteration
during transport or transfer. Adulterated
particles (coal, ash etc
 How should cement be stored
Precautions that must be taken in the storage of Portland
cement are given below in a series of Don'ts.
 Do not store bags in a building in which the walls, roof
and floor are not completely weatherproof
 Do not store bags in a new warehouse until the interior
has thoroughly dried out
 Do not be content with badly fitting windows and doors,
make sure they fit properly and ensure that they are kept
shut
 Do not stack bags against the wall. Similarly, don’t pile
them on the floor unless it is a dry concrete floor. If not,
bags should be stacked on wooden planks or sleepers
 Cont…

 Do not disturb the stored cement until it is to be

taken out for use.
 Do not keep dead storage. The principle of
first-in first-out should be followed in removing
bags
 Do not stack bags on the ground for temporary
storage at work site. Pile them on a raised, dry
platform and cover with polythene sheet.
 Mortar
Definition
• A mortar is a mixture of sand or similar inert
particles with a binding agent (generally
cement and/or lime), to which water is added
in predetermined proportions.
• Mortar=Cement+Sand+H2O

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Cont…

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 Cont…
Uses of Mortar
• It bonds masonry elements together in all
directions (vertical and horizontal joints).
• It allows forces to be transmitted between the
elements and notably vertical forces
• As a wall plaster
• As a constituent of concrete

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 Cont..
Types of Mortar
There is a large number of mortar types used in
the construction industry.
1. Mud mortar
2. Lime mortar
3. Cement mortar
4. Compo mortar

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 Cont…
1. Mud mortar
• The most elementary mortar.
• Is made from soil mixed with water.
• It may be suitable for laying soil blocks
• If exposed to the weather will quickly be eroded by rain

2. Lime mortar
• Lime mortar = lime +sand + water
• use of lime results in a relatively workable mixture
• slow hardening makes it less attractive than cement mortars

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 Cont…
3. Cement mortar
• Cement mortar= Portland cement + sand(inert
particles)+water
• While the use of lime results in a relatively
workable mixture, rapid development of
strength as well as stronger mortar is most
conveniently obtained with Portland cement

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 Cont…
4. Compo mortar
• Compo mortar = cement + lime +sand + water.
• In order to combine the advantages of both
lime and cement, mortars are prepared with
appropriate proportions of Portland cement,
lime and sand, which is known as compo-
mortar.

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 Materials for mortar

A. Sand
• Should be well graded, that is the particles should not all
be fine or all coarse.
• Should be clean ,free from dust, loam, clay and vegetable
matter.
• These foreign materials prevent the adhesion of the
particles, there by reduce the strength.
• Silt test could be made at the construction to check the
percentage of silt in the sand

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 Silt test (Jar test)

• fill the jar to a depth of 5cm with representative sample of

sand.
• Add water until the jar is about three fourth full.
• Shake vigorously
• Allow the jar to stand for an hour or more during which the
silt will be deposited.
• If the layer of silt is more than 3mm or 6%, the sand is not
suitable for mortar work.
B. Water
• Clean water is important for the same reasons, any
impurities present will affect bond strength between the paste and sand

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 Properties of Mortar
Some of the properties of mortar are:
1.Workability
2.Strength
3.Water tightness

Factors affecting the properties of mortar include:

• The amount of mixing water
• Properties of the binder used
• Cement content; fineness and composition
• Characteristics and grading of the sand

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 Cont…
1.Workability
• For the same proportions, lime-sand mortar in
variably gives better work ability than Portland
cement-sand mortar
2. Strength
• Strength of mortar is affected by a number of
factors, which include the quality of the
ingredients, their proportion, the curing
method and age
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 Cont…
3. Water Tightness
• When Mortar is used in parts of buildings
exposed to dampness or moisture and might
be required to be watertight.
• To make such type of mortar, Portland
cement should be used because of its
hydraulic property

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 Batching and Mixing

• Materials used for making mortar should be accurately

measured.
• Cement is usually measured by weight in cement bags
whereas sand is measured by volume.
• 1 bag of cement=50 Kg =35 liters(loose volume)
• Sand is measured by using a measuring box to hold quantities
in multiples of 35lt.
• The convenient size of the box can be
40cm X 35cmX 25cm internally

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 Cont..
• Few examples of mortar proportions by
volume for different purposes:
• For masonry:
• Cement mortar :-1 cement: 4-5 sand
• For bricklaying:
• Lime mortar:-1 lime: 3-4 sand

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•THANK YOU!

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