Cementing Materials

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 Lecture Outline

 Lime
 Gypsum
 Cement
 Mortar

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 In construction, the term cementing material
generally refers to bonding agents that are mixed with
water or other liquid, or both, to produce a cementing
paste.
 Calcareous cements (containing calcium carbonate) can
be classified as;Non-hydraulic and Hydraulic.
i. Non-hydraulic cements: which are not able to set
and harden in water (e.g. non-hydraulic lime) or
which are not stable in water (e.g. gypsum plasters).
ii. Hydraulic cements: that are able to set and
harden in water, and give a solid mass that does not
disintegrate, i.e., remain stable in water (e.g. Portland
cement)
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 Lime
It is found in its natural form as a rock (Sedimentary
rock) of varying degree of hardness.
It is mainly composed of calcium oxide (CaO). However,
lime deposits are generally found mixed with impurities
such as CO2, Fe2O3, and MgCO3. Depending on the
impurities lime deposits acquire different colors.

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 Production of Lime
It involves burning of the raw material and then slaking.
The raw material is burnt in a vertical kiln like the one shown
in the figure below.

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 Complete Cycle in Lime………

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A) Quick lime/ Commercial lime
It is by burning the limestone in some form of vertical kilns
to a temperature of 1000oC. The CO2 is driven off, leaving
the CaO that is known as quick lime or caustic lime.

B) Hydrated/Slaked lime
Quick lime can never be used as such for construction
purposes but must be mixed with water. This process is
called slaking or hydration of lime.
The resulting product is calcium hydroxide [Ca(OH)2] and
is called slacked or hydrated lime.

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 The Use of Lime………..
As a mortar (A mixture of Lime + sand +water)
As a plastering and white washing of buildings
For Manufacturing of glass
Lime concrete (Substitute Cement:- Lime +Aggregate +
Sand + Water
As a stabilizer in roads, earthen dams, airfields, building
foundations(to neutralize acidic soils)
Crushed for use of aggregate for roads

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 Gypsum
Gypsum is a combination of Sulphate of lime with
water of crystallization.
It occurs naturally as either hydrous Surphate of lime
(CaSO4.2H2O) that is generally 75% CaSO4 and 24% H2O,
or as Unhydrate (CaSO4)

The gypsum rock To be classed as gypsum rock at least 65%

by weight must be CaSO4.2H2O.
Pure gypsum is known as Alabstor and it is a white
translucent crystalline mineral, so soft that it can be
scratched with the fingernail. 9
 Manufacture of Gypsum
Gypsum plasters are manufactured by heating the
raw material gypsum at either moderate or high
temperatures, the results being plaster of Paris
and hard-finish plaster respectively.

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 The Use of Gypsum ………..

It is used in arts and in building construction.

For partition
For ceiling
For plastering

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 Arts & decoration

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 For Partition walls

For ceiling

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 CEMENT

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 History of cement
Non-hydraulic cement concretes are the oldest
used in human history.

As early as around 6500 B.C, non hydraulic cement

concretes were used by the Syrians and spread
through Egypt, the Middle East, Crete, Cyprus, and
ancient Greece.

The non-hydraulic cements used at that time were

gypsum and lime.
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 History …
Historically Romans used Pozzalana, animal fat,
milk, and blood as admixtures for building
concrete.
To trim down shrinkage, they were known to have
used horsehair.
Historical evidence shows that the Assyrians and
Babylonians used clay as the bonding material.
Lime was obtained by calcining (exposing to strong
heat) limestone.

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 History …
The Egyptians used gypsum mortar in
construction, and the gypsum was obtained by
calcining impure gypsum.
E.g. The Pyramid of Cheops.

The Chinese also used lime mortar to build the

Great Wall in the Qin dynasty (220 B.C)

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 Hydraulic lime
 A hydraulic lime was developed by the Greeks
and Romans using limestone containing
argillaceous (clayey) impurities.
Thus, hydraulic lime mortars were used
extensively for hydraulic structures from second
half of the first century B.C to the second century
AD.
Smeaton conducted extensive experiments with
different limes and Pozzolans, and found that
limestone with a high proportion of clayey
materials produced the best hydraulic lime for
mortar to be used in water.
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James Parker of England filed a patent in 1796 for
a natural hydraulic cement made by calcining nodules of
impure limestone containing clay.

Vicat of France produced artificial hydraulic lime by

calcining synthetic mixtures of limestone and clay.

Portland cement was invented by Joseph Aspdin

of England in 1824.

Isaac Johnson who first burned the raw materials to

the clinkering temperature in 1845 to produce
modern Portland cement.
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 Portland cement…………
It is the name given to a cement obtained by
thoroughly mixing together calcareous and
argillaceous, or other silica, alumina and iron
oxide-bearing material, burning them at a
clinkering temperature, and grinding the resulting
material.

No material, other than gypsum, water and grinding

aids may be added after burning.

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Manufacture of Portland Cement
Cement is obtained by burning at very high
temperature a mixture of calcareous and argillaceous
(Containing clay) materials in correct proportion.
Calcined product is known as Clinker.
The raw materials are carefully proportioned to
provide the desired amounts of lime, silica, aluminum
oxide, and iron oxide.
After grinding to facilitate burning, the raw materials
are fed into a long rotary kiln, which is maintained at
a temperature around 2700°F.
A small quantity of gypsum (3–5%) is added to clinker
and it is then pulverized (reduce to fine particle) into
very fine powder is known as cement.
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 Clinker production ……

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 Contd…….

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 Dry and wet process
The mixing and grinding of the raw materials can be
done either in water or in a dry condition; hence, the
names wet and dry process.

In the dry process the raw materials are crushed,

dried in rotary driers, proportioned, and then
ground in ball mills consisting of rotating steel.

The resulting powder is then burnt in its dry

condition in the rotary kiln.

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 Wet process
In the wet process the materials are mixed with
enough water to form slurry, which is 30 to 35
percent water.

In this form the materials are further proportioned,

mixed, ground and pulverized and then pumped
to a furnace called a kiln.

Quality control of materials is critical and throughout

the manufacturing process samples are continually
taken for laboratory analysis.
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 Physical properties of Cement
Portland cements are fine grey powders.
The particles have a relative density of about 3.14,
and most have a size of between 2 and 80 mm.

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 Physical Properties of Portland
Cement
Fineness
Soundness
Consistency
Setting time
False set and flash set
Compressive strength
Heat of hydration
Loss on ignition
Density
Bulk density
Sulfate expansion
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 MORTAR
Definition
A mortar is a mixture of sand with a binding agent
(generally cement and/or lime), to which water is
added in previously determined proportions.

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 MORTAR
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 (i.e. the weight of
the elements themselves, or applied forces).
As a wall plaster and constituent of concrete.

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 MORTAR
Types of Mortar
There is a large number of mortar types used in the
construction industry.
1. Mud mortar
2. Lime-sand mortar
3. Pozzo-lime mortar
4. Cement-sand mortar
5. Cement-lime-sand mortar
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 MORTAR
1. Mud mortar
The most elementary mortar
Is made from soil mixed with water
It may be suitable for laying soil blocks
Is not recommended for fired bricks
If exposed to the weather will quickly be
eroded by rain

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 MORTAR
2. Lime-sand mortar
Lime and sand mortar is traditional material
use of lime results in a relatively workable
mixture
 slow hardening makes it less attractive than
cement mortars
3. Pozzo-lime mortar
Naturally occurring volcanic ashes may
contain siliceous material which can have a
pozzolanic reaction with lime.

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 MORTAR
Materials for mortar
1. 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
The jar test is a ‘quick’ method to determine if the
sand contains too many fines.
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 MORTAR
Materials for mortar
1. Sand
Jar test procedure:
 Place approximately 2 inches of sand in a glass quart jar.
 Fill the jar with water.
 Shake the jar vigorously to mix the sand and water.
 Set the jar on a level platform and allow to settle for several
hours (4 - 8 hours).
 Upon settling, after several hours (4 - 8 hours), the layer of fines
that settle on top of the sand layer should not be thicker than
3.2 mm (1/8 inch).

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 MORTAR
Materials for mortar
2. Water
Clean water is important for the same reasons, as is
clean sand; any impurities present will affect bond
strength between the paste and sand.

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 MORTAR
Materials for mortar
Proportioning of the component materials
 In proportioning the component materials the following
points must also be considered:
 The mixture must be workable so that it can be placed
and finished without undue labor. (Workable)
 Portland cement is the most costly ingredient in the
mixture the proportion used should be as small as its
consistent with the attainment of desired properties.
(Economical)

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 MORTAR
Properties of mortar
 Some of the properties of mortar are:
 Workability
 Strength
 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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 MORTAR
Properties of mortar
Workability
For the same proportions, lime-sand mortar invariably
gives better workability than Portland cement-sand
mortar
 At times plasticizers and air-entraining agents are
used in order to improve the workability of cement-
sand mortars, especially when they are lean (i.e.
containing less amount of cement) mixes.

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 MORTAR
Properties of mortar
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.
 The compressive, tensile, shear and bending strengths of
cement mortar increases with an increase in the cement
content, and this is true irrespective of the grain size
distribution of the sand.
 The strength of mortar increases with age

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 MORTAR
Properties of mortar
Water Tightness
At times mortar is used in parts of buildings exposed
to dampness or moisture and might be required to be
watertight.
With the cement content, materials, and workability all
constant, strength and degree of water-tightness
increase with the density of the mix.

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 MORTAR
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.
50 Kg cement=35 liters
Box size: 40cm X 35cmX 25cm

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 MORTAR
Batching and mixing
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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 MORTAR
Materials for mortar

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 Concrete

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 Lecture Outline
 Materials for concrete
 Mix design
 Fresh concrete
 Hardened concrete
 Quality control

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 Materials for concrete
General
 Concrete is most suitable where high comprehensive
strength is required.
 In combination with steel a high tensile strength can
be achieved.
 Concrete work requires a special and different work
procedure.
 Each necessary step to produce concrete is
important for the quality of the end product.

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 Materials for concrete
General
 Concrete is a conglomerate, stone like material
composed essentially of three materials:
1. Cement,
2. Water,
3. Aggregate and
4. Admixture.

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 Materials for concrete
General
 The strength and quality of concrete
depend not only on the quality and quantity
of the materials; but on
 the procedures used in combining
these materials and
 the skill involved in the placing and
curing of concrete.

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 Materials for concrete
Concrete Making Materials
 Concrete is a composite material made of Portland
cement, water and aggregates.
 Admixtures may be added to give the concrete
special properties either when fresh or hardened or
both.
 Deal with the properties of the component materials
and the requirements they have to fulfill in order to
produce good and sound concrete.

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 Materials for concrete

1. Portland Cement
 Refer the notes on cementing materials.

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 Materials for concrete
2. Water
 Water fit for drinking is generally suitable for making
concrete.
 Substances in water that present in large
amounts may be harmful are:
 salt,  sulphates,
 oil,  organic matter,
 industrial wastes,  silt,
 alkalies,  sewage etc.

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 Materials for concrete
2. Water
 Tests by the sense of smell, sight or test should
reveal such impurities, however water of doubtful
quality should be submitted for laboratory analysis and
test.
 Water-used in concrete mixes has two functions:-
 to react chemically with the cement which will finally set
and harden, and
 to lubricate all other materials and make the concrete
workable.

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 Materials for concrete
2. Water
 The quality of cement paste is determined by the
proportion of water to cement (Water-cement
ratio).
 Too much water prevents proper setting:
 Too little water prevents complete chemical
reaction called hydration.

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 Materials for concrete
2. Water
 A 50 kg bag of cement requires approximately 12.5
liters of water for complete chemical combination of
materials.
 However, the use of exactly the amount of water
needed for chemical combination is not practical
under field condition.
 Usually 20 liters to 40 liters must be used for each
sack of cement.

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 Materials for concrete
2. Water
 The extra water serves as a lubricant to carry the
cement paste into small pores of the aggregate.
 Excess water is also needed to wet the aggregate so
that it will not absorb water needed by the cement.

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 Materials for concrete
2. Water
 The more water
 added to the mix, the more fluid and plastic it will
be (the better the workability will be), and the weaker
the concrete will be.
 Too much water will cause the aggregate to segregate,
resulting in concrete that is uneven in strength.
 The excess water will float the fine, light particles of
cement to the top of freshly placed concrete.
 This process is called bleeding.

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 Materials for concrete
2. Water
 The amount of water to be mixed with a given
quantity of cement is expressed as the number of
liters of water to each 50 kg bag of cement.
 The proportion of water to cement is referred to as
the water-cement ratio.
 Water may be measured either by volume or by
weight.

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 Materials for concrete
2. Water
 The tanks on modern concrete mixers are
equipped with water gauges or meters that
assure the proper amount of water for each batch.
 The amount of water in the aggregate must be
determined so that the total amount of water in the
design mix will be correct.

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 Materials for concrete
2. Water
 Total amount of water required per unit
volume of fresh concrete depends on a
number of factors that are:
 The desired consistency of the concrete,
which may be expressed as will be seen,
by the slump test.
 The maximum size, particle shape and
grading of the aggregate
 Water reducing admixtures.

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 Materials for concrete
3. Aggregate
 Aggregates generally occupy 65 to 75%
of the volume of concrete.
 consideration should be given in their
selection and proportioning.
 Aggregates range from fine sands to rocks
38 mm in diameter or larger.
 The quality of the concrete is affected in
several ways by the aggregate.
 The strength of the aggregate limits the
strength of the concrete.
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 Materials for concrete
3. Aggregate
 The surface of the grains affects the
plasticity of a concrete mix.
 Rounded grains will move more easily as
the concrete is placed.
 Long and thin aggregate will weaken
concrete.
 The aggregates used in concrete may be
natural aggregates or they may be by-
products of an industrial process (e.g.
blast-furnace slag).
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 Materials for concrete
3. Aggregate
 In Ethiopia the great majority of aggregates
used for concrete are obtained from
natural sources:
 form of rock, which is crushed to obtain
the desired maximum size or gravel,
which is processed by crushing or
screening oversized materials.
 In choosing aggregate for use in a
particular concrete attention should be
given to three important requirements:
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 Materials for concrete
3. Aggregate
 three important requirements:
1. Workability when fresh for which the size
and gradation of the aggregate should be
such that undue labor in mixing and
placing will not be required.

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 Materials for concrete
3. Aggregate
2. Strength and durability when hardened - for
which the aggregate should:
 be stronger than the required concrete
strength
 contain no impurities which affect strength
and durability
 contain no silt which affect the
adhesive strength between aggregate and
cement paste (fine aggregate)
 be resistant to weathering action

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 Materials for concrete
3. Aggregate
3) Economy of the mixture- meaning to say
that the aggregate should be:
 available from local and easily
accessible deposit or quarry
 well graded in order to minimize
cement paste, hence cement,
requirement

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 Materials for concrete
3. Aggregate
Classification of Aggregates
 Aggregates are generally classified
based on their:
a) source,
b) chemical composition,
c) weight,
d) size or
e) the mode of preparation.

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 Materials for concrete
3. Aggregate
Classification of Aggregates
a) The source
 aggregates may be natural or artificial.
 Natural aggregates are obtained
from riverbeds (sand, gravel) or from
quarries (crushed rock),
 Artificial aggregates are generally
obtained from industrial wastes such
as the blast furnace slag.

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 Materials for concrete
3. Aggregate
Classification of Aggregates
b) chemical composition
 There are three main classes of aggregates
differing in their chemical composition:
i. argillaceous (composed primarily of
Al2O3),
ii. siliceous (composed primarily of Si2O3), &
iii. calcareous rock (composed primarily of
CaCO3).

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 Materials for concrete
3. Aggregate
Classification of Aggregates
c) Weight
 Aggregates are divided into three groups:
1. Heavy aggregates with densities more than
4000kg/m3 (these include steel balls, bronze and
other metals used in concrete for radiation
shielding)
2. Normal weight aggregates with densities
between 2400 and 2800kg/m3
3. Light weight aggregates such as pumice and
scoria which used to make light weight concrete,
having solid densities in the region of 700kg/m3
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 Materials for concrete
3. Aggregate
Classification of Aggregates
d. the mode of preparation
 The classification of rocks according to
their mode of formation is:
 igneous,
 sedimentary and
 metamorphic rock.

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 Materials for concrete
3. Aggregate
Grading requirements for concrete aggregates
 Both the maximum size and grading are
important factors to be considered when
calculating proportions for concrete mix.
 According to Ethiopian Standard,
 fine aggregate should consist of natural
sand obtained from the natural
disintegration of rock or sand obtained
from crushed stones
 coarse aggregate should be gravel,
crushed gravel, or crushed stone.
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 Materials for concrete
3. Aggregate
Grading requirements for concrete aggregates

 The grading or particle size distribution

of fine aggregate and coarse aggregate
should be within the limits specified in the
following tables:

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 Grading requirements for concrete aggregates

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 Materials for concrete
4. Admixtures
 Admixtures are ingredients other than water,
aggregates, hydraulic cement, and fibers that are
added to the concrete batch immediately before or
during mixing.
 A proper use of admixtures offers certain
beneficial effects to concrete, including:
 improved quality,
 acceleration or retardation of setting time,
 enhanced frost and sulfate resistance,
 control of strength development,
 improved workability, and
 enhanced finish ability.

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 Materials for concrete
4. Admixtures
Water - reducers
 Water-reducing admixtures are groups of products
that are added to concrete to achieve certain
workability (slump) at a lower w/c.
 The basic role of water reducers is
 to deflocculate the cement particles agglomerated
together;
 release the water tied up in these agglomerations and
 producing more fluid paste at lower water contents.
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 Materials for concrete
4. Admixtures
Water - reducers
 Use of water reducers usually reduces
water demand 7-10%.
 A higher dosage of admixtures leads to
more reduction; excess retardation may be
encountered.
 It is well known that using water-reducing
admixtures increases concrete strength.

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 Materials for concrete
4. Admixtures
Water - reducers
 Increases in compressive strength are as
much as 25% greater than would be
anticipated from the decrease in w/c.
 Using admixtures in concrete improves
concrete's properties, misusing any kind of
admixtures will negatively affect these
properties.
 Follow manufacturer's recommendations
whenever admixtures are used.
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 Materials for concrete
4. Admixtures
Set – retarders
 Retarding admixtures are known to delay
hydration of cement without affecting the
long-term mechanical properties.
 used in concrete to offset the effect of high
temperatures, which decrease setting times,
or to avoid complications when unavoidable
delays between mixing and placing occur.

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 Materials for concrete
4. Admixtures
Set – retarders
 Use of set retarders in concrete pavement
construction:
1. enables farther hauling, thus eliminating the cost
of relocating central mixing plants;
2. allows more time for texturing or plastic grooving
of concrete pavements;
3. allows more time for hand finishing around the
headers at the start and end of the production day;
and
4. helps eliminate cold joints in two-course paving.

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 Materials for concrete
4. Admixtures
Set – retarders
 The role of retarding admixtures can be explained
in a simple way:
 the admixtures form a film around the cement
compounds (e.g., by absorption), thereby preventing
or slowing the reaction with water.
 The thickness of this film will dictate how much the
rate of hydration is retarded.
 After a while, this film breaks down, and normal
hydration proceeds.
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 Materials for concrete
4. Admixtures
Accelerators
 Accelerating admixtures are added to
concrete either:
 to increase the rate of early strength
development or
 to shorten the time of setting, or both.

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 Materials for concrete
4. Admixtures
Accelerators
 Chemical compositions of accelerators
include some of inorganic compounds such as;
 soluble chlorides,
 carbonates,
 silicates,
 fluorsilicates, and
 some organic compounds such as triethanolamine.
 Among all these accelerating materials,
calcium chloride is the most common
accelerator used in concrete.
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 Materials for concrete
4. Admixtures
Accelerators
 calcium chloride in reinforced concrete can
promote corrosion activity of steel
reinforcement, especially in moist environments.
 the use of good practices, i.e.
 proper proportioning,
 proper consolidation, and
 adequate cover thickness can significantly
reduce or eliminate problems related to
corrosion.

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 Materials for concrete
4. Admixtures
Superplasticizers
 were originally developed in Japan and
Germany in the early 1960s; they were
introduced in the United States in the mid-
1970s.
 The main purpose of using superplasticizers is
 to produce flowing concrete with very high
slump in the range of 175 - 225mm to be used
in heavily reinforced structures and in
placements where adequate consolidation by
vibration cannot be readily achieved.

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 Materials for concrete
4. Admixtures
Superplasticizers
 The other major application is the production of
high-strength concrete at w/c's ranging from 0.3
to 0.4.
 The capability of superplasticizers to reduce
water requirements 12-25% without affecting
the workability leads to production of high-
strength concrete and lower permeability.

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 Thank you

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