1. The document is notes on concrete written by Saqib Imran, a civil engineering student, to share knowledge with other students and engineers. 2. It defines concrete and reinforced concrete, listing their advantages. Factors affecting the properties of concrete are also discussed. 3. Precautions for tunnel construction and placing concrete at construction sites are provided, such as using proper equipment, compaction, and avoiding rain.

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SAQIB IMRAN 0341-7549889 1
Assala mu alykum My Name is saqib imran and I am the
student of b.tech (civil) in sarhad univeristy of
science and technology peshawer.
I have written this notes by different websites and
some by self and prepare it for the student and also
for engineer who work on field to get some knowledge
from it.
I hope you all students may like it.
Remember me in your pray, allah bless me and all of
you friends.
If u have any confusion in this notes contact me on my
gmail id: Saqibimran43@gmail.com
or text me on 0341-7549889.
Saqib imran.

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CONCRETE
WHAT IS CONCRETE?
WHAT IS CONCRETE?
Concrete is a composite material, which is made from a mixture of cement, aggregate
(sand or gravel), water and sometimes admixtures in required proportions. It is one of
the most important and useful materials for construction work.
When all the ingredients (cement, aggregate, water) are mixed in the required
proportions, the cement and water start a reaction with each other to bind themselves
into a hardens mass. This hardens rock-like mass is known as concrete.
ADVANTAGES OF CONCRETE:
1. Concrete is economical than other building materials.
2. The compressive strength of concrete is very high.
3. Concrete is very strong in compression.
4. Concrete can be cast easily into any desired shape.
5. It possesses a minimum corrosive and weathering effects.
6. Concrete made with steel reinforcement provides equal coefficients of thermal
expansion.
7. Concrete can be pumped and sprayed in difficult positions.
8. It is fire resistant.
9. Concrete is durable, and have a little maintenance cost which can be ignored.
WHAT IS REINFORCED CEMENT CONCRETE?
REINFORCED CEMENT CONCRETE:
Reinforced cement concrete is a combination of concrete and steel bars(reinforcement
bars) where they carry the compressive force and tension of a structure simultaneously.
As we know that concrete is very strong in compression but weak in tension and its
resistance to tension is also low. That’s why plain concrete can be used only where the
member is in pure compression, but on the other hand, steel is equally strong in
compression and tension. So the combination of steel and concrete works very well and
they are used to take up all the stresses. Such a combination of steel and concrete is
called reinforcement cement concrete.

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ADVANTAGES OF REINFORCED CEMENT CONCRETE:
1. Reinforced concrete has a high compressive strength.
2. It is economical in ultimate cost.
3. It can be produced easily at the construction site.
4. Reinforced concrete has monolithic characters which gives much rigidity to the
structure.
5. It is durable, fire resistant and almost impermeable to moisture.
6. The materials used in reinforced concrete are easily obtainable.
7. Maintenance cost of reinforced concrete structure is almost ignorable.
8. Due to the flexibility and fluidity nature, reinforced concrete can be moulded into any
desired shape.
9. It is most useful and economical material in constructions such as footings, piers,
damp etc.
FACTORS AFFECTING PROPERTIES OF CONCRETE
FACTORS AFFECTING PROPERTIES OF CONCRETE:
The factors which affect the properties of concrete (workability, bond strength, tensile
strength, creep, shrinkage, bleeding, segregation, etc) are described below.
1. WATER-CEMENT RATIO:
Strength elasticity, durability, and impermeability of concrete are increased with the
decrease in water-cement ratio, provided the concrete is workable. Shrinkage is
increased with greater w/c ratio.
2. CEMENT CONTENT:
With increases in cement content, w/c ratio decreased and consequently, strength,
elasticity, durability, and permeability is increased. More cement improves workability
but it also increases shrinkage which is undesirable.
3. TEMPERATURE:
The rate of setting and hardening of concrete is high at higher temperature. If the
temperature of concrete falls below 0°C, free water in concrete turns into ice crystals
and since ice has greater volume than the same quantity of water, the concrete is
completely disrupted.

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Such concrete on thawing will have no strength. If the temperature is more than the
freezing temperature, cool concreting gives better ultimate strength, durability and less
shrinkage.
4. AGE OF CONCRETE:
The strength of concrete goes on increasing with age, though the rate of increase
becomes very slow with the passage of time. The following table gives some ides of
strength development with age:
Age Strength in percentage
Ordinary cement Rapid hardening cement
7 days 35% 65%
28 days 60% 90%
3 months 85% 95%
1 year 100% 100%
5. AGGREGATE:
Size, shape, and grading of aggregates, control concrete properties to a large extent.
Rounded aggregates give better workability than flaky and angular aggregates. Larger
the size of the aggregate, greater will be the strength, provided concrete mix is
workable. Property graded aggregates give better workability and strength.
6. CURING:
Curing is the process of keeping the setting concrete damp so that complete hydration
of cement is brought about. Besides strength the curing affects following qualities:
a) It improves wear-resisting and weather resisting qualities.
b) It increases impermeability and durability.
c) It reduces shrinkage.
7. FROST:
The frost causes disintegration of concrete and as such strength, durability and
impermeability are reduced. Resistance to frost action depends upon the structure of
the pores in the concrete.

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8. ENTRAINED AIR:
The entrained air in concrete is due to incomplete compaction. It has the effect of
reducing the strength of concrete. With 1% of entrained air, the strength of concrete is
reduced by 5%. It also increases permeability of concrete.
WHAT IS 1.54 IN CONCRETE CALCULATION
What Is 1.54 In Concrete Calculation?
In concrete calculation, we always multiply Wet volume with 1.54 to get dry volume. But
do you know what is 1.54 or where this 1.54 came from? If You don’t know, no
problem. In this article, I will explain what is 1.54 while calculating quantity of cement,
sand, aggregates for concrete.
let us take a concrete cube.
The length of the concrete cube = 1 m
The width of the concrete cube = 1 m
The height of the concrete cube = 1 m
Volume of concrete cube = length x Width x Height = 1 x 1 x 1 = 1 m³ (Wet volume)
When we convert this we volume into dry volume, the volume is increased by 54% of
wet volume.

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∴ Dry volume = Wet volume + 54% of Wet volume
= 1 + (54/100) x 1 =1 + 0.54 = 1.54
To convert wet volume of 1 m³ concrete into dry volume = 1.54
To convert wet volume of “n” m³ concrete into dry volume = 1.54 x n
Where n = Wet volume of concrete.
Example:
The length of the concrete cube = 4 m
The width of the concrete cube = 3 m
The height of the concrete cube = 2 m
Wet volume = 4 x 3 x 2 = 24 m³
∴ Dry volume = ( Wet volume + 54% of wet volume)
= 24 + {(54/100) x 24}
= 36.96 m³
Note:
Always remember in concrete calculation, we get wet volume first, to convert wet
volume into dry volume, multiply wet volume with 1.54.

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PRECAUTIONS IN CONSTRUCTION OF TUNNELS
PRECAUTIONS IN CONSTRUCTION OF TUNNELS:
For economic safe and quick construction of tunnels, the following precautions should
be taken:
1. The shape of the tunnel should be decided according to its purpose.
2. Cross-sectional dimensions of the tunnel should be decided to achieve economy in
its construction.
3. Economic calculations for extent of equipment and labour should be made before
starting the tunnel construction.
4. The pattern of blasting the material in different locations should be decided for
maintaining speed of driving and safety.
5. The sequence of operations must be decided so that proper use of labor and
equipment is made.
6. Labour should be well organized to maintain continuous progress of the tunneling
operations.
7. Outdated or unsuitable tools should not be used.
8. Care should be taken to see that every operation is completed at scheduled time.
9. The Excavated material should be piled up in a manner suitable to the method of
loading being employed.
10. loading and hauling of muck should be carried out efficiently.
11. The sequence and type of lining should be determined in advance to
achieve economy.
12. Selection of multipurpose and uniform type of equipment should be made, according
to the size and shape of the tunnel.
PLACING OF CONCRETE AT SITE

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PLACING OF CONCRETE AT SITE:
The concrete should be placed and compacted before its setting starts.The method of
placing concrete should be such as to prevent segregation. It should not be dropped
from a height more than one meter. In case, placing of concrete is likely to take some
time it should be kept in an agitated condition.
Before concrete is placed in position, formwork should thoroughly be checked for its
stiffness and trueness. The surface of placing concrete should be truly prepared
according to requirements and thoroughly soaked with water.
The surface should be cleaned thoroughly to remove any loose matter spread over it.
After having checked the formwork and necessary preparation of the surface, concrete
placing is started. Following precautions should be taken while placing concrete.
1. Concrete should be laid continuously to avoid irregular and unsightly lines.
2. To avoid sticking of concrete, formwork should be oiled before concreting.
3. While placing concrete, the position of formwork and reinforcement should not get
disturbed.
4. To avoid segregation, concrete should not be dropped from a height more than 1
meter.
5. Concrete should not be placed during rain.
6. The thickness of the concrete layer should not be more than 15 – 30 cm in case of
RCC and 30 – 40 cm in case of mass concrete.
7. Walking on freshly laid concrete should be avoided.
8. It should be placed as near to its final position as practicable.

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COMPACTION OF CONCRETE – HAND COMPACTION & MACHINE
COMPACTION
COMPACTION OF CONCRETE:
Consolidation of plastic concrete is known as compaction. In the process of compaction,
efforts are only directed to reduce the voids in the compacted concrete. Compaction of
concrete can be done either by manually or mechanically. When it is done manually it is
called hand compaction or tamping and in second case it is termed as machine
compaction.
1. HAND COMPACTION:
Hand compaction is done with the help of steel tamping rods, or timber screeds. Narrow
and deep members are compacted with tamping rods. Thin slabs and floors are tamped
with the help of screeds. Compaction should be done in layers of 30 cm for mass
concrete and 15 cm for reinforced concrete.
Compaction should be carried out for such a time that a layer of mortar starts
appearing at the compacted surface. Excessive compaction and under compaction both
are harmful to concrete. Due to excessive compaction, CA particles sink to the bottom
cement and F.A mortars appear at the top. This makes concrete structure
heterogeneous and hence affects strength.
2. MACHINE COMPACTION:

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Machine or mechanical compaction is done by using vibrators. Vibrators produce
vibrations which when transmitted to plastic concrete make it flow and affect
compaction. The air bubbles are forced out of concrete due to vibrations. Over vibration
should not be allowed otherwise C.A particles will concentrate at the lower layers and
mortar will come to the surface. There are three types of vibrators in most common use:
a. Internal vibrator
b. External vibrator
c. Surface vibrator or screed vibrator.
INTERNAL VIBRATOR:
This vibrator is also known as needle vibrator, immersion, or poker. It consists of a
power unit and a long flexible tube at the end which a vibrating head is attached. This
vibrator develops about 7000 vibrations per minute. Whenever compaction is to be
done, the vibrating head is inserted in the concrete. This vibrator is very useful for
compaction of mass concrete.
EXTERNAL VIBRATOR:
This vibrator is also known as form vibrator and clamped to the formwork and imparts
vibrations to the concrete through formwork. This vibrator is used only if the use of
internal vibrator is not practicable as in the case of thin and congested situations. It is
also called external vibrator.
SURFACE OR SCREED VIBRATOR:
This vibrator is clamped to the screed. It imparts vibration to the concrete from the
surface when screeding operation of the concrete is carried out. It is effective only for
depths of about 20 cm and hence useful for thin horizontal surfaces such as pavements.
MIXING OF CONCRETE – HAND MIXING AND MACHINE MIXING
MIXING OF CONCRETE:
After proportioning all concrete ingredients their mixing is done. The mixing process
should ensure homogeneous mass uniform color. Segregation should not take place
during the mixing operation.
Mixing is done by two following methods:
1. Hand Mixing
2. Machine Mixing

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1. HAND MIXING:
This method is adopted where the quantity of concrete is very small or where mixing
machine is not available.
Cement and sand are first of all mixed dry on a clean hard impermeable platform. Dry
mixing is continued until the mixture attains uniform color. Now, this mix is spread on
the measured stock of coarse aggregate in required amount and these are mixed again
to have uniform color. Shovels are used for this mixing purpose.
Make hollow in the middle of the mixed pile and add 75% of the required amount of
water. Mixing is done and the remaining quantity of water is added to acquire the
uniform workability. In this method of mixing, about 10% more cement is used to make
good the cement lost due to possible water flowing out of the mix and also to make
good strength characteristic to inferior result of hand mixing.
2. MACHINE MIXING:
On large works where concreting work is quite large, machine mixing of concrete proves
economical. Concrete produced by machine mixing is more homogeneous and can be
prepared with comparatively less w/c ratio.
The concrete mixers may either be batch type or continuous type. Batch mixers mix and
discharge each load of materials separately, whereas continuous mixers produce
steady stream of concrete so long as it is in operation. Latter type mixers are not in
common use. Batch type mixers are mostly adopted. These may be rotary o non-tiling
type or tilting type.
A) ROTARY OR NON-TILTING TYPE MIXER:
This mixer has a cylindrical drum fitted with a number of inclined blades in it. It revolves
about horizontal axis and has two openings. Charge is admitted in the drum through
one opening and mixed charge is discharged through the second one. This mixer is
available in following capacities. (Concrete produced in a batch in liters)
140 NT, 200 NT, 280 NT, 400 NT and 800NT. (NT indicates Non-tilting).
B) TILTING TYPE MIXER:
This mixer has conical-shaped drum which revolves about inclined axis. The drum is
tiltable in different positions of charging, mixing, and discharging. Blades are fitted
inside the drum to affect through mixing of materials. The materials are charged into the
drum by loading skip. These are available in the following capacities:
100 T, 140 T, and 200 T.
In capacity figures 100, 140 200 etc. indicate capacity in liters of one batch. The most
common size of mixer is 200 T. It is a convenient size and permits a full bag batch of
concrete of 1:2:4 ratio. Speed of revolution/minute of mixers is 15 to 20.

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COMPRESSIVE STRENGTH TEST OF CONCRETE CUBES
COMPRESSIVE STRENGTH TEST OF CONCRETE CUBES:
AIM:
To determine the compressive strength of concrete.
APPARATUS & EQUIPMENT:
1. Compression test machine,
2. Cube mould of 15 cm size,
3. Curing Tank,
4. Tamping bar,
5. Weighing balance.
SPECIMEN FOR TEST:
The cube samples shall be of 15 x 15 x 15 cm. If the largest nominal size of the
aggregate does not exceed 2 cm, then cube samples of 10 cm may be used as an
alternative.
CASTING OF CONCRETE CUBES:
PROPORTIONING:
The ingredients should be proportioned as per design standard.

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MIXING OF CONCRETE:
The concrete should be mixed either by hand or in a laboratory machine mixer in such a
manner as to reduce wastage of water and other materials.
MACHINE MIXING:
The machine mixing should be done as follows:
1. Add one half of the coarse aggregate into the mixing drum.
2. Then add cement and fine aggregates and finally add the remaining coarse
aggregates.
3. Add required amount of water.
4. Start the mixing machine until the resulting concrete gives uniform texture.
HAND MIXING:
The mixing should be done on a watertight, non-absorbent platform with a trowel or
shovel using the following procedure:
1. Mix the cement and fine aggregates thoroughly in dry condition.
2. Add Coarse aggregates and thoroughly mix with cement and fine aggregates.
3. Add required amount of water and mix it properly until the concrete becomes
homogeneous of desired consistency.
SAMPLING OF CONCRETE CUBES:
1. Fill the mould with freshly mixed concrete in layers approximately 5 cm deep.
2. Compact the concrete either by vibrator or by using the tamping bar. ( Minimum 35
strokes per layer for 15 cm cubes and 25 strokes for 10 cm cubes).
3. Finish the top level of the mould using a trowel.
4. Cover the mould with a glass plate or gunny bag to protect evaporation.
CURING OF CONCRETE CUBES:
1. Keep the specimens in a place, free from vibration, in moist air and at a temperature
of 27°C ±2° C for 24 hours.
2. After 24 hours, mark and remove the samples from mould.
3. Submerge the cubes immediately in fresh and clean water until taken out prior to test.
The water should be renewed every 7 days.

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PROCEDURE OF COMPRESSIVE TEST:
1. Remove the specimens from water before 30 minutes of testing.
2. Remove any loose sand or other material from the surface of the specimens and let
them dry.
3. Clean the bearing surface of the compression testing machine.
4. Now place the cube in the testing machine in such a manner that the load is applied o
the opposite sides of the cubes.
5. Align the axis of the specimen with the centre of thrust of spherically seated platen.
6. Apply the load increasingly at a rate of 140 kg/cm² per minute until the cube collapse.
7. Note down the maximum load applied to the specimen and any other unusual
activities at the time of failure.
POINTS TO BE REMEMBERED :
1. AGE OF TEST:
The test should be done at 7 days and 28 days.
2. NUMBER OF SPECIMEN:
At least three specimens, preferably from different batches for testing at each selected
age.
CALCULATION:
Let assume the maximum applied load is 400 KN = 400000 N
Cross-sectional area of cube =15 x 15 = 225 cm²
Compressive strength = 400000/225 = 1778 N/cm² = 1778/9.81 = 181 Kg/cm² [ 1kg
=9.81 N]
REPORTS:
Details Samples

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Specimen 1 Specimen 2 Specimen 3
Compressive Load
(KN)
380 KN 400 KN 425 KN
Compressive
Strength
(Kg/Cm²)
(380000/225) /
9.81
= 172 kg/cm²
(400000/225) /
9.81
= 181 kg/cm²
(425000/225) /
9.81
= 192 kg/cm²
Average
Compressive
Strength
= (172+181+192)/3
= 181.66 Kg/cm²
PRECAUTION:
This test should be done at a temperature of 27°C ± 2°C.
COMPRESSIVE STRENGTH OF CONCRETE OVER TIME:

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COMPRESSIVE STRENGTH OF CONCRETE AT 7 & 28 DAYS:
NO FINES CONCRETE – ADVANTAGES & DISADVANTAGES
NO FINES CONCRETE:
As the name suggests by itself, no-fines concrete does not contain any fine aggregates.
This concrete is produced by eliminating fine aggregates from plain concrete. Only
cement, coarse aggregate, and water are used. The coarse aggregate particles are
surrounded by a thin cement paste coating.
Naturally, the concrete contains a large number of voids which make the concrete
lightweight and reduces its overall strength. The compressive strength of no fines
concrete is very low and depends on the water-cement ratio, cement content, and
aggregate grades.
No fines concrete is gaining its popularity day by day due to its various advantages over
conventional concrete, which are as follows:
ADVANTAGES OF NO-FINES CONCRETE:
1. The density of no fines concrete is very low.
2. No fines concrete does not segregate and the capillary movement of water is almost
nil.
3. It has better thermal insulating characters due to the presence of large voids.

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4. This concrete can be used by dropping from a permissible height.
5. Shrinkage is also lower than normal concrete.
6. It is lightweight.
7. The formwork can be removed earlier.
8. No mechanical vibrator is required for compacting no fines concrete, simple rodding
method is sufficient for full compaction.
9. It gives better and attractive appearances.
10. Production cost is comparatively lower than other conventional concrete because
lower cement content is used.
DISADVANTAGES OF NO-FINES CONCRETE:
1. The strength of no-fines concrete is lower than ordinary concrete.
2. No-fines concrete cannot be used in reinforced concrete structure.
3. The consistency of no-fines concrete cannot be measured by any available standard
methods such as slump test, compacting factor test etc.
USES OF NO-FINES CONCRETE:
As we said earlier this concrete is not suitable for use in reinforced concrete structure.
However, the walls made of no-fines concrete can be used in cold countries because of
its good thermal insulating characteristics.
MASS CONCRETE – WHAT IS MASS CONCRETE & WHERE IT IS USED
MASS CONCRETE:
The concrete placed in different massive structures such as dams, bridge piers, canal
locks etc is known as mass concrete.
In mass concrete, larger size aggregates (up to 150 mm maximum) and low slump (very
stiff consistency) are used to reduce the amount of cement in the concrete mix
(normally 5 bags per m3 of mass concrete).
As the concrete is relatively dry and harsh, it needs immersion type of powder vibrators
for full compaction. The concrete is normally placed in open forms. Due to the greater
mass of the concrete, the heat of hydration (reaction between cement and water) may
increase the temperature considerably.
These can be avoided by placing the concrete in shorter lifts and taking gaps of several
days before the next lift. During concreting, cold water should be circulated through the
pipes buried in the concrete mass may also be useful. If possible, concreting can be

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done in the winter season to lower the peak temperature in concrete. Alternatively, the
aggregates may be cooled before using in the mix.
The high temperature due to the heat of hydration may result in an extensive and
serious shrinkage in the mass concrete. The shrinkage cracks can be prevented by
using low heat cement and by rapid curing of the concrete.
The early age strength is very high compared to later strength concrete cured at normal
temperatures. During setting and hardening the volume change of mass concrete is
very small but it can produce larger creep at a later stage.
HONEYCOMB IN CONCRETE – CAUSES, PREVENTION & REMEDIES
HONEYCOMB IN CONCRETE:
Honeycomb is the rough pitted surface or voids in concrete formed due to improper
compaction or incomplete filling of the concrete.
In this formation, concrete not filled properly and create gaps/voids in between concrete
and aggregates ( As shown in the above image). Honeycomb is mostly seen in columns
and beams and can easily be detected just after removing the formwork. Actually, it
looks like a honey bee nest.

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Honeycomb is a serious problem of concrete which should be treated carefully.
Otherwise, the structure or member may lose its strength.
The various reasons for honeycomb in concrete are as following:
1. Inappropriate workability of concrete.
2. Use of stiff concrete mix or the concrete is already set before placing.
3. Improper vibration of concrete in formwork.
4. Over reinforcement.
5. Use of larger size aggregates in excessive amount.
6. Formwork is not rigid and watertight.
7. Concrete is poured from more than allowable height.
8. Congestion of steel is preventing the concrete to flow over all corners.
PREVENTION:
So if we overcome the above reasons, we can easily prevent honeycomb in concrete.
Here I will discuss further how to repair honeycomb if it is already formed in the
concrete.
REPAIRING OF HONEYCOMBS IN CONCRETE:
1. First, remove the loosened aggregates and concrete particles from the affected
surface by using a wire brush and a chipping hammer.
2. Clean the surface thoroughly with a brush to remove finer particles and then wash the
surface with water.
3. Let the surface to dry well and apply Chemi-fix glue on the area.
4. Now mix the concrete grout with white cement and add required amount of water ( as
per the specification recommended by the manufacturer).
5. Then pour/paste the mixture in the affected area to fill it completely. In case of large
honeycomb, the concrete mixture should be poured after creating a pocket.
6. Remove the formwork after 12 hours and then cure it well.
HOW TO CONTROL CONCRETE WASTE AT SITE

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HOW TO CONTROL CONCRETE WASTE AT SITE:
Some amount of concrete is always wasted during construction. Normally we consider
3- 5 % as wastage while estimating the materials quantity for particular construction
work. But more than 3-5% wastage may increase the overall cost of the project and
affect the work progress. Hence it is very important to control the concrete wastage at
the site during concreting.
The wastage of concrete can be reduced by proper planning of pour. Concrete pour
card should be prepared before concreting. So we can know the quantity of concrete to
be poured before starting concrete mixing.
Production of concrete should match with the pouring speed to reduce waiting time and
to avoid the setting of concrete before placing in the form.
The approximate concrete quantity should be estimated and when the pouring work is
near to be completed, do inform the batch plant operator to stop extra concrete supply.
During concrete placement, there may be some issues at site which can stop concrete
pouring for some times. In such situations, the supervisor should inform the batching
plant operator to pause the concrete production and supply.
If concrete is produced in excess amount, it can be used elsewhere to avoid extra
wastage.
So, wastage of concrete can be prevented by proper planning not only before
placement but also during placement and site supervisor should be trained well to take
care of the site.
WHAT IS THE BEST CONCRETE MIX DESIGN

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WHAT IS THE BEST CONCRETE MIX DESIGN?
The cost of concrete determines the characteristic strength, quality control, workability
of mix (cost of labor) which includes the high degree of compactions. The best concrete
mix design is the one which satisfies all the aspects for which it was designed.
STRENGTH:
The strength of 95% cube cast after 28 days of curing should be greater than the
characteristic strength for which concrete has been designed.
WORKABILITY & PLACING:
As working condition changes so the properties desired from concrete also changes,
the concrete which can be easily placed without segregation and with least compaction
required.
WATER CEMENT RATIO:
Water should be maximum (0.45 – 0.65).
DURABILITY:
The concrete must be durable enough to face harsh conditions of atmosphere for which
it has been designed.
These are the main properties considered while designing concrete and the designed
concrete satisfying such conditions can be called as best concrete mix design.
There are three type of mixes,
1. Nominal mixes
2. Standard mixes
3. Designed mixes
1. NOMINAL MIXES:
The mixes which have fixed cement aggregate ratio but the nominal mix concrete for a
given workability varies widely In strength.
2. STANDARD MIXES:
1. It is designated by code book of IS456:2000
2. The minimum compressive strength have included
3. May result in under and over rich mixes.

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3. DESIGNED MIXES:
1. The mix proportion is designed by producer of concrete
2. The concrete is specified by the designers
3. It does not guarantee the concrete mix proportion for the prescribed performance.
As we normally use the standard mixes which are safe and economic, as per
standard code book.
ULTRA HIGH STRENGTH CONCRETE
ULTRA HIGH STRENGTH CONCRETE:
We are conversant with the use of concrete having compressive strength varying from
100 to 300 kg/cm2. With the introduction of prestressed concrete in the construction
industry, constant research is going on to develop concrete having very high strength.
As a result thereof it has been established that by suitable selection of material and by
adopting special method of production it is possible to make concrete having
compressive strength exceeding 1000 kg/cm2.

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Ultra high strength concrete can be produced by improved compaction (By pressure
and vibration etc) and adhesion of cement matrix to aggregates or by the adoption of
cementitious aggregates. Ultra high strength concrete can be easily produced by using
high quality coarse aggregates, synthetic aluminous fine aggregates, and cement.
Use of high temperature to increase the lime silica bond and use of spiral wrapping of
concrete to induce triaxial stress are the techniques being tried to develop ultra high
strength concrete. Polymer concrete can be superplasticised concrete also get covered
in the category of ultra high strength concrete to some extent.
By using high strength concrete, load bearing capacity of columns can be increased
considerably. Hence by its use, it is possible to adopt slender columns in multi storied
buildings which besides looking aesthetically good also permits greater utilization of
useful floor space. On account of its high compressive as well as tensile strength, this
type of concrete finds wide application in prestressed concrete.
TYPES OF JOINTS IN CONCRETE
CONCRETE JOINTS:
Except in small jobs, it is not possible to place concrete in one continuous operation.
Joints are also required for functional consideration of the structure. Concrete joints can
be classified under following categories:
1. Construction Joints.
2. Expansion Joints.
3. Contraction Joints.
4. Warping Joints.
1. CONSTRUCTION JOINTS:
These joints are provided where there is a break in construction programme. Concreting
operation should be so planned that the work is completed in one operation. If,
however, it has to be stopped before completion of entire work, construction joints are
provided. Location of construction joints should be such that it interferes minimum with
the functional characteristics of the structure. Best locations for construction joints are
as following:
i) Beam: Joint may be located at mid-span or over the center of the column in direction
at right angles to the length of the beam.
ii) Columns: Joints should be located a few cm below its junction with the beam.
iii) Slab: Joints may be placed at mid span or directly over the center of the beams, at
right angles to the slab.
Formwork for construction joint should be placed at the end of each day’s work.

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Before new concreting is started, the concrete surface of hardened concrete should be
cleaned, roughened, saturated with water, and applied cement grout. This will ensure
proper bond between old and new concrete works. New concreting is started before the
applied grout on old surface attains initial set.
2. EXPANSION JOINTS:
These joints are provided to allow for expansion of the concrete, due to rise in
temperature above the temperature during construction. Expansion joints also permit
the contraction of the element. Expansion joints in India are provided at an interval of 18
to 21 m. A typical expansion joint is shown in Fig 1. The open gap of this joint varies
between 2 cm and 2.5 cm. Sometimes, to transfer load from one slab to the adjacent
slab, dowel bars are also used at suitable intervals at these joints.
3. CONTRACTION JOINTS:
These joints are provided to permit contraction of the concrete. These joints are spaced
closer than expansion joints. These joints do not require any load transfer device as it
can be achieved by the interlocking of aggregates. However, some agencies
recommend use to dowel bars fully bonded in concrete.
4. WARPING:
Warping joints are provided to relieve stresses induced due to warping effect. These
joints are also known as hinged joints.
FLOW TABLE TEST TO MEASURE THE FLOW VALUE OF CONCRETE

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FLOW TABLE TEST TO MEASURE THE FLOW VALUE OF
CONCRETE:
Flow Table Test Equipment
OBJECTIVE:
To measure flow value of concrete using flow table test.
EQUIPMENT:
1. Flow table
2. Mould shaped as slump cone.
3. Wooden tamping bar.
PROCEDURE OF TEST:
1. Prepare a leveled surface and place the flow table on the surface.
2. Use a damp cloth to clean the top of the table and the inner surface of the mould.
3. Place the slump cone shaped mould on the table.
4. Fill the cone with fresh concrete in two equal layers and start tamping each layer 10
times using the wooden tamping bar.
5. After tamping the concrete is then struck off flush with the upper edge of the cone
and the free area of the top of the table is cleaned off.
6. After half a minute of striking off, lift the cone vertically.
7. Then raise the table top by the handle and allow it to fall 15 times in 15 seconds. The
concrete spreads itself out.
8. Measure the diameter of spread concrete in two dimensions parallel to the table
edges.

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RESULT:
The arithmetic mean of the two diameters shall be the measured flow in millimeters.
MINIMUM COVER FOR REINFORCEMENT IN CAST-IN-PLACE CONCRETE
MINIMUM COVER FOR REINFORCEMENT IN CAST-IN-PLACE
CONCRETE:
The clear cover is the distance between the outer surface of concrete to the outer
surface of the nearest bar.

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Clear cover varies in different conditions. The clear cover for cast-in-place concrete is
given in the below table.
Sl.
No.
Conditions Minimum
cover
(inches)
1 Concrete cast against and permanently exposed to earth 3
2 Concrete exposed
to weather or earth
No. 6 to no. 18 bar 2
No. 5 bar, W31 or D31 wire
and smaller
1 ½
3 Concrete
unexposed to
weather or in
contact with the
ground.
Slabs, Walls, and
Joist
No. 14 and no. 18
bar
1 ½
No. 11 bar and
smaller
¾
Beams and
columns
Primary
reinforcement,
ties, stirrups, and
spirals
1 ½

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Shells and
folded plate
members.
No. 6 bar and large
bars.
¾
No. 5 bar, W31 or
D31 wire and
smaller.
½
4 Concrete tilt-up
panels cast against
a rigid horizontal
surface, like
concrete slab.
No. 8 bar and smaller. 1
No. 9 to no. 18 bar. 2
DISTRIBUTION OF STRESS BETWEEN STEEL & CONCRETE
STRESS DISTRIBUTION BETWEEN STEEL & CONCRETE:
As per the basic assumption, plain RCC section before bending remains plain after
bending. It is clear that in the flexural member at a specific point the compressive stress
and the tensile stress are proportional to their distance from N.A ( Neutral axis). As the
bond between concrete and steel becomes excellent, strains induced in concrete as
well as in the steel will be equal.
Let strain in concrete and strain in steel be designated by ec and et
According to Hooke’s law
Stress/Strain = Moduli of elasticity
Therefore
Where t = Permissible tensile stress in steel.
Es = Moduli of steel.
and
c’ = Stress in concrete in level with tensile steel.

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Ec = Modulus of concrete.
But
Or
From the above expression, it is evident that the stress in the steel is m times the stress
in concrete surrounding it.
10 + THUMB RULES FOR CONCRETE MIX DESIGN

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FOR ADDING 4 LITERS OF WATER IN 1 CU.M
FRESHLY MIXED CONCRETE
1. The slump value will be increased by 25 mm.
2. The compressive strength of concrete will be decreased by 1.5 to 2.0 N/mm2
3. The shrinkage potential will be increased by 10%.
4. 1/4 bag of cement will be wasted.
IF THE TEMPERATURE OF FRESHLY MIXED
CONCRETE IS INCREASED BY 1%, THEN
1. 4 liters of water per cu.m will give equal slump.
2. The air content will be decreased by 1%.
3. The compressive strength of concrete will be decreased by 1.0 to 1.5 N/mm2.

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IF THE AIR CONTENT OF FRESHLY MIXED
CONCRETE IS
1. Increased by 1% then the compressive strength will be decreased by 5 %.
2. Decreased by 1%, yield will be decreased by 0.03 cu.m per 1 cu.m.
3. Decreased by 1%, then the slump value will be decreased about 12.5 mm.
4. Decreased by 1%, then the durability of the concrete will be reduced by 10%.
POLYMER CONCRETE
POLYMER CONCRETE:
Polymer concrete is an ordinary concrete produced with OPC ( Ordinary portland
cement) wet cured and inseminated with liquid or vaporous chemical compound (Methyl
methacrylate monomer) and polymerized by gamma radiation or with chemical initiated
implies, i.e by utilizing thermal catalytic method (Adding 3% Benzoyl peroxide) to the
monomer as a catalyst. The impregnation is helped by drying the concrete at an
extreme temperature by evacuations and absorbing the monomer under limited
pressure.
TYPES OF POLYMER CONCRETE:
Polymer concrete can be classified in following three categories:
1. Polymer impregnated concrete (PIC).

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2. Polymer cement concrete (PCC).
3. Polymer concrete (PC).
ADVANTAGES OF POLYMER CONCRETE:
1. It has high impact resistance and high compressive strength.
2. Polymer concrete is highly resistant to freezing and thawing.
3. Highly resistant to chemical attack and abrasion.
4. Permeability is lower than other conventional concrete.
APPLICATION OF POLYMER CONCRETE:
Polymer concrete is broadly utilizing in several circumstances as following
1. Nuclear power plants.
2. Kerbstones.
3. Prefabricated structural element.
4. Precast slabs for bridge decks.
5. Roads.
6. Marine Works.
7. Prestressed concrete.
8. Irrigation works.
9. Sewage works.
10. Waterproofing of buildings.
11. Food processing buildings etc.
GRADES OF CONCRETE

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GRADES OF CONCRETE:
In IS: 456-1978, the different grades of concrete are given as M10, M25, M20, M25,
M30, M35, and M40. In the classification of concrete mix, the letter M denotes the Mix
and the numbers 10, 15, 20, 25, 30, 35, 40 represent the predetermined works cube
strength of 15 cm cubes after curing of 28 days in N/mm2.
The works cube strength refers to the strength achieved by the concrete after 28 days
curing. It can also be defined as the crushing strength of concrete cubes at 28 days.
The compressive strength of the concrete should not be greater than 5% of the test
results are expected to fall. The list of specified concrete grades are given below:
Grade Of Concrete Specified Compressive Strength At 28
Days (N/mm2)
M10 10
M15 15
M20 20
M25 25
M30 30
M35 35
M40 40

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Note 1: M5 and M7.5 concrete also exist which can be used in lean concrete
bases/mud and for ordinary masonry wall foundation.
Note 2: Concrete grade less than M15 should not use in reinforced concrete.
Note 3: M10, M15, M20…. concrete approximately equal to 1:3:6, 1:2:4, 1:1.5:3…
nominal mix.
CUBE STRENGTH OF CONCRETE
CUBE STRENGTH OF CONCRETE:
The strength achieved by the concrete on 15 cm concrete cubes after curing of a
temperature of 27± 2° C is known as cube strength of concrete. Curing water should be
replaced at an interval of 7 days. The sample is not permitted to dry before testing.
Cubes are submerged in water after preparation of 24 hours, they should be kept in
such a place where the minimum relative humidity is 90%.
At the point when cubes are produced at the field site, they are known as works cube
and the strength of these cubes are known as works cube strength.
These days concrete mixes are not categorized by the proportion of concrete
ingredients but rather by the cube strength after testing for 28 days concrete curing. For
example, M100, M150, M200 have cube strength of 100, 150, 200 kg/cm2 after curing
of 28 days.
As per most recent ISI unit of force has been changed from kg to Newton. N(0)
subsequently plain concretes are classified M10, M15, M20, M25 where M refers to the
mix and 10, 15, 20, 25 represents the cube strength of concrete in N/mm2 after curing
of 28 days in field condition.
FIBER REINFORCED CONCRETE
FIBER REINFORCED CONCRETE:

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Steel Fiber Reinforced Concrete.
Due to the presence of microcracks at the interface of mortar-aggregate, plain concrete
is considered as a brittle material. It has been found that these low tensile strength and
impact resistance can be significantly improved by adding a certain amount of fiber in
the concrete mix. The fiber may be of steel or glass of asbestos. Such a concrete
containing fiber is called fiber reinforced concrete.
The improvement of weakness depends on several factors such as materials of fiber,
shape, and size of fiber, volume, and pattern of distribution in the concrete mix. Fiber
reinforced concrete can be categorized into following two types.
1. Steel Fiber Reinforced Concrete.
2. Glass Fiber Reinforced Concrete.
1. STEEL FIBER REINFORCED CONCRETE:
Steel Fiber Reinforced Concrete or SFRC is produced by mixing little amount of steel
fibers in the elements of concrete. Steel fibers are regularly prepared by cutting 10-60
mm length of low carbon steel wires diameter of 0.25-0.75 mm. Other than round fibers,
flat steel fibers are moreover normal in use. Flat sheet steel fibers are delivered by
cutting 0.15-0.40 mm thick plates in widths extending from 0.25-0.90 mm, furthermore
length 10-60 mm.
Steel fibers tend to group together which makes troubles in guaranteeing their uniform
dissemination in the concrete. This trouble can be overcome by utilizing fiber bundles.
The steel fiber in the fiber bundle separates out at the time of concrete mixing and get
aggravated in an irregular design in the concrete mix.
By adding of 2-3% of fibers (by volume) it is conceivable to accomplish a few
circumstances increment in the flexural strength of the concrete and further increase in
crack resistance, explosion resistance, and different properties of the concrete. SFRC is
suitably used in the construction of pavements, bridge decks, pressure vessels, tunnel
lining etc.
2. GLASS FIBER REINFORCED CONCRETE:
Glass fibers are normally produced from 200 – 400 different filaments that are lightly
bonded to create a strand. These strands are sheared into different lengths for making
cloth, mat, and tape. By using conventional mixing method only 2% fibers can be mixed
in 25 mm length. It is found that when the diameter is decreased, the strength of glass
fiber is significantly increased. That’s why they can not be used in longer spans.
Suitable treatment is also required to utilize the glass fibers as micro reinforcement
because it gets corroded due to the effect of alkali present in the portland cement. The
tensile strength and impact resistance of concrete can be increased by adding 10% of
fiberglass in the concrete. Fiber reinforced concrete is mostly used for manufacturing
precast products such as spun pipes, wall cladding etc.

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WORKABILITY OF CONCRETE
WORKABILITY OF CONCRETE:
Workability can be defined as the property of fresh concrete which describes the ease
and homogeneity of the concrete to be mixed, fully compacted and finished. A workable
concrete should possess following two requirements.
1. The concrete should be compacted with minimum efforts.
2. The concrete should not form bleeding and segregation.
Workability of concrete mainly depends on the mix proportion and the properties of
concreting materials (water, cement, aggregates). The shape, size, and grades of
aggregates also play a great role in the variation of workability. For better workability
fine and coarse aggregates should be well graded. It has been found that concrete
made of round grain sand is more workable than the concrete of crushed sand. If air
entraining admixture is used in the mix, it will also increase the workability and decrease
segregation and bleeding.
FACTORS AFFECTING WORKABILITY OF CONCRETE:
The factors affecting workability are as following:
1. Amount Of Water In The Mix:
2. Proportion Of Coarse And Fine Aggregates: Workability can be increased by
decreasing the amount of coarse aggregates in the mix. Fine aggregates produce more
wore workable concrete.
3. Shape Of aggregates: Round shaped aggregates give better workability than angular
shaped aggregates.
4. By expanding the cement content in the mix.
5. By including admixtures in the mix.
Apparently, the necessity of workability differs as per the nature of the job and blockage
in the full stream of concrete due to the spacing and nature of the reinforcement. The
workability of concrete is generally measured by one of the following three tests.
1. Slump Test.
2. Compaction Factor Test.
3. Vee-Bee Test.
COMMON CONCRETING PROBLEMS AND THEIR PREVENTION

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COMMON CONCRETE PROBLEMS AND THEIR PREVENTION:
There are many problems we might be facing during and after concreting. To produce
high quality concrete we must take some precautions to avoid those common problems
during concreting. In this article, we will discuss common concrete problems and how to
prevent them.
1. BLEEDING:
Bleeding refers to as a tendency of water to appear on the top surface of concrete after
finishing. Due to bleeding some measure of water (with sand particles and other
cementing materials) appears at the surface of the concrete.
Following precautions should be taken to reduce bleeding in concrete.
1. Design the mix appropriately.
2. Include least water content in the mix.
3. Use greater amount of cement content.
4. Use greater amount of fine particles.
5. Utilize a little measure of air entraining admixture.
2. SEGREGATION:
Segregation means separation of coarse aggregates from the concrete surface due to
poor compaction. It is generally seen in the plastic stage of concrete. As a result
honeycomb, laitance, scaling, porous layer, bond failure etc. can be formed in concrete.
Following precautions should be adopted to prevent segregation in concrete.
1. Design the mix appropriately.
2. Never use excessive water content.
3. Take care of handling, placing, and proper compaction of concrete.
4. Do not allow the concrete to be dropped from more heights.
5. Use air entraining admixture.
6. Keep the formwork to be watertight.
3. LAITANCE:
The appearance of cement-sand particles on the surface of freshly placed concrete is
known as laitance. It is mainly occurred due to the bad effect of bleeding and
segregation of concrete. The bond between subsequent layers of concrete becomes
weaker and as a result, laitance is developed.

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Following precautions can be taken to stop the occurrence of laitance in concrete.
1. Clay, dust, silt content etc should be removed before mixing the concrete.
2. Water-cement ratio should be maintained properly.
3. Water should not be sprayed on the concrete surface during finishing work.
4. Use well graded fine aggregates in the mix.
5. Add little amount of water reducing admixture in the concrete mix.
4. SCALING:
Scaling is the physical deterioration of concrete in which the surface layer of concrete
broke down, pitted or flaked away. Due to this effect concrete surface becomes worse.
Scaling can be prevented by taking same precautions adopted for laitance.
5. PLASTIC SHRINKAGE CRACKS:
When the evaporation rate of water mixed in the concrete is greater than the bleed
water of concrete, plastic shrinkage cracks are developed on the surface of the
concrete. Basically, this type of cracks occurs in very hot climate.
6. DUSTING:
Dusting can be prevented by taking following precautions.
1. Maintain a suitable water/cement ratio in the concrete.
2. Utilize dust free aggregates in the mix.
3. Guarantee appropriate hydration of concrete.
4. Avoid early surface finishing of concrete.
ADVANTAGES OF QUALITY CONTROL OF CONCRETE
QUALITY CONTROL OF CONCRETE:
Concrete is mainly prepared at the construction site using locally accessible materials of
variable properties. Hence the concrete strength differs from one batch to another batch
over a time period. The variation in concrete strength depends on several factors such
as variation in the materials quality, mix proportion, batching, mixing techniques,
handling, and workmanship. These variations are unavoidable during concrete
production.
Therefore it is essential to control these variations to reduce the contrast between the
minimum strength and characteristic mean strength of the concrete mix and
consequently diminishing the quantity of cement substance. The method which controls
this distinction is known as quality control of concrete.

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The main goal of quality control is to lowering the above variations and manufacture a
uniform material using the appropriate characteristics regarding the job.
ADVANTAGES OF QUALITY CONTROL OF CONCRETE:
The various advantages of quality control are as following.
1. Quality control ensures the logical use of the available materials after testing their
properties and reducing the cost.
2. Without quality control, there is no guarantee that the weakness of one area will be
compensated in another by over spending in that area. In that case, quality control
offers the best solution.
3. Quality control helps to minimize the risks of overdesign that reduces the overall cost.
4. Quality control promotes the completion of a project by checking the concrete
production and rectifying the faults at every stage.
5. It reduces the repair and maintenance cost.
COMPACTION FACTOR TEST
WORKABILITY OF FRESH CONCRETE BY COMPACTION
FACTOR TEST:
Compaction Factor Test Machine
THEORY:
The compaction factor test is carried out to measure the degree of workability of fresh
concrete with regard to the internal energy required for compacting the concrete
thoroughly.
APPARATUS:
1. Compaction Factor Machine,

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2. Weighing Machine,
3. Steel Trowel Or Mechanical Vibrator.
PROCEDURE:
1. Fill the upper hopper by pouring the concrete sample in it.
2. Open the hinged door at the lower end of the upper hopper allowing the concrete to
fall into the lower hopper.
2. Immediately open the gate of at the bottom of the lower hopper to allow the concrete
to fall into the cylindrical mould.
3. Remove the excess concrete above the top level of the mould by using a trowel.
4. Take the weight of the cylindrical mould with concrete (partially compacted concrete)
and find out the weight of the concrete ( W1).
5. Now remove the concrete from the mould and refill it with the same concrete sample
in 5 cm layers.
6. Compact the each layer of the concrete fully by using a steel rod or mechanical
vibrator. ( There should be no air voids present in the concrete)
7. Now take the weight of the cylinder with concrete (Fully compacted concrete) and find
out the weight of the concrete (W2).
8. Calculate the compaction factor by below given formula.
CALCULATION:
The compaction factor is calculated by dividing the value of partially compacted
concrete by the value of fully compacted concrete.
i.e Compaction Factor = W1/W2
CONCLUSION:
Value Of Compacting Factor Standard Of Workability
0.95 Good
0.92 Medium
0.85 Low
WATERPROOFING OF CONCRETE

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WATERPROOFING OF CONCRETE:
A concrete is said to be well designed when it is properly mixed, compacted, cured and
set for making impermeable itself. The uses of waterproofing agents should be kept
away as much as possible for working in ordinary situations. A thick concrete with least
conceivable air voids should accordingly be the essential thought in making of
dampproof concrete. The accompanying conditions should be fulfilled to accomplish the
waterproofing of concrete.
1. Utilize the best accessible material.
2. Proportionate the aggregates by using fineness modulus strategy.
3. Utilize just as much amount of water is required to get the desired workability.
4. Mix the concrete completely.
5. Proper supervision amid laying and compaction.
6. Finish the curing of concrete.
However, in specific cases such as water retaining structures, structures that are to be
constructed in water-logged soil, or in soggy climate, it might be important to adopt
additional precautions to assure water-tightness. This incorporates the expansion of
certain waterproofing materials such as permo, sika, pudlo etc in the concrete mix at the
time of mixing. This is named as integral waterproofing.
8 CAUSES OF CRACKS IN CONCRETE YOU SHOULD KNOW
DIFFERENT SOURCES OF CRACKS IN CONCRETE:
Cracking is one of the most common problems in concrete and it should be avoided
seriously. Different causes of cracks in concrete are described below.
1. SHRINKAGE:
Shrinkage is one of the major causes of cracking in hardened concrete. In drying
shrinkage, the volume of concrete is gradually decreased and if the component is
restrained against free movement, tensile stresses are developed which causes cracks.
2. TEMPERATURE CHANGES:
The temperature variation in concrete results in the differential volume change. When
the tensile strain capacity of concrete exceeds due to the differential volume change, it
will crack.

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3. CHEMICAL REACTION:
Due to the alkaline nature of cement, it reacts with the carbon dioxide (CO2) present in
the atmosphere resulting in an appreciable increase in the volume of the materials
which finally leads to cracking.
4. POOR CONSTRUCTION PRACTICES:
Poor construction practices such as adding excessive water to the mix, lack of curing,
poor compaction, using low-grade materials, unreasonable placements of construction
joints etc. are also responsible for cracking in concrete.
5. ERRORS IN DESIGN & DETAILING:
Errors in design and detailing such as an inadequate amount of reinforcement, improper
design of foundation, precast members and slabs, improper selection of materials, lack
of sufficient contraction joints etc may result in excessive cracking.
6. CONSTRUCTION OVERLOADS & EARLY FORMWORK
REMOVAL:
The load induced in the structure during construction can also lead to cracking
especially at the younger stage when the formwork is removed earlier.
7. ELASTIC DEFORMATION AND CREEP:
The different components of the building such as wall, column, beam. slab etc undergo
elastic deformation when loaded. The deformation of concrete depends on the type of
building materials used in the construction such as bricks, cement concrete blocks etc.
This unusual deformation of concrete results in cracking.
8. CORROSION OF CONCRETE:
The corrosion of steel develops a huge amount of iron oxides and hydroxide that have a
much greater volume than the volume of metallic iron. Hence the volume is increased
and cracks.
METHODS OF CONCRETE CURING

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CONCRETE CURING:
The process of protecting the moisture of concrete surface and enhancing the hydration
of cement is known as curing. The physical properties of concrete totally depend on the
hydration of cement. If curing is not done properly concrete will be failed to acquire its
full strength. Improper concrete curing may also lead the concrete to crack.
METHODS OF CONCRETE CURING:
1. SHADING:
By this method, the evaporation of water is locked in the concrete surface. It also
protects the surface from heat, wind etc. In cold climates, it prevents the concrete from
freezing by preserving heat of hydration of cement.
2. COVERING THE SURFACE WITH WATERPROOF PAPER:
In this method, the concrete surface is covered with wet gunny bags or waterproof
papers to avoid water loss and to protect the concrete from further damage. This
method gives satisfactory results for curing of concrete slabs and pavements.
3. SPRINKLING WATER:
In this method, water is sprayed on the concrete with the help of nozzles at proper
intervals. This method is not so effective due to the difficulty of keeping the concrete
surface be moist all the time.

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4. PONDING:
Ponding is the most common method that is adopted for curing of floors, slabs,
pavements etc. In this method, concrete surface is first covered with moist wrapper for
24 hours. After that, the covers are then removed and small amount of clay puddles are
constructed around all the area. Then water is filled for final curing.
5. MEMBRANE CURING:
In this method concrete surface is covered by waterproof membranes or sealing
compounds such as bitumen emulsion, wax, rubber latex emulsion, water repellant,
plastic films etc. The membrane protects the water loss from concrete. It is seen
membrane curing for 28 days give equivalent strength to two weeks moist curing.
6. STEAM CURING:
Steam curing is done by increasing the temperature of concrete in wet condition. This
method allows the concrete to achieve its full strength within a short time, thus curing is
also finished within short time. Steam curing is mostly adopted for the production of
precast members.
FERROCEMENT – ADVANTAGES AND APPLICATION OF FERROCEMENT
Ferrocement is a type of thin reinforced concrete in which the cement mortar is
reinforced with small diameter steel wire meshes at close intervals. The mortar gives
the mass and the wire mesh contributes tensile strength and ductility of the material. As
a result, the concrete shows a high tensile strength to weight ratio and excellent
cracking performance. It is also known as ferroconcrete.
MATERIALS:
1. Mortar mix.

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2. Cement.
3. Sand (fine aggregates).
4. Water.
5. Admixture.
6. Wire mesh.
7. Skeleton steel.
ADVANTAGES OF FERROCEMENT:
The major advantages of Ferro cement are as following:
1. It can be fabricated into any desired shape.
2. The tensile strength of ferro-cement is very high than conventional concrete.
3. The structures made with ferro-cement are thin and lightweight.
4. Construction procedure is easy, quick and no skilled labours are required.
5. Formwork is also not required in such construction.
6. Precast members can be suitably manufactured by using this type of concrete.
7. Maintenance cost is very low, almost nil.
8. It is fire, corrosion, and earthquake resistance.
9. It is economical.

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APPLICATION OF FERROCEMENT:
Due to its various advantages, the application of ferrocement in construction is
increasing day by day. The application of ferrocement are as follows:
1. Mobile home,
2. Modular housing,
3. Water tank,
4. Swimming pool,
5. Wind tunnel,

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6. Marine work, etc.
WATER CEMENT RATIO
WATER CEMENT RATIO:
Water cement ratio can be defined as the ratio of the volume of water to the volume
of cementused in a concrete mix. Water has a great role on the strength and workability
of concrete. After lots of experiments it has been found that for a specific proportion of
materials in a concrete mix, there is a certain amount of water that gives maximum
strength.
A slight change in the amount of water causes much more differences in the strength of
concrete. If less water is used, the resultant concrete will be nearly dry, hard to place in
the form and may create difficulties in compaction. Besides this, with less water proper
setting will not be guaranteed and thus the strength of concrete get reduced
considerably.
On the other hand, if water is used more, it may develop larger voids and honey-
combing in the set concrete, in this way decreasing its density, durability, and strength.
Hence, water cement ratio attends an important role in producing concrete of required
strength. The lower the ratio, the greater is the strength of concrete.
REQUIRED WATER-CEMENT RATIO ( BRITISH STANDARD
SPECIFICATIONS):
Proportion Water-Cement Ratio
1 : 2 : 4 0.58

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1 : 1.5 : 3 0.51
1 : 1: 2 0.43
MORTAR VS CONCRETE: DIFFERENCE BETWEEN MORTAR AND
CONCRETE
MORTAR VS CONCRETE:
Concrete and mortar are two different building materials used in construction works, but
many of us get confused on the differences between mortar and concrete. In this article,
I will discuss the basic differences between concrete and mortar.
CONCRETE:
Concrete is a composite material produced from a mixture of sand, cement, aggregates
and water in required proportions.
MORTAR:
Mortar is made from a mixture of cement, sand, and water.
DIFFERENCE BETWEEN MORTAR AND CONCRETE:
1. Concrete is a mixture of cement, sand, aggregates and water, on the other hand,
mortar is made from cement, sand, and water.
2. Concrete is much stronger than mortar.
3. Mortar is less durable than concrete.
4. The water-cement ratio is higher in mortar, but the main aim of concrete is to keep
the water-cement ratio as minimum as possible.
5. Mortar is a good binding material and it is mostly used to bind the bricks together.
Due to greater strength and durability concrete is used in all type of construction works
such as buildings, bridges, roads etc.
6. Concrete gives a long outcome but mortar has to be replaced in every 20 – 30 years.
CONCRETE MIX DESIGN : DESIGN MIX CONCRETE & NOMINAL MIX
CONCRETE

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CONCRETE MIX DESIGN:
Mix design is a method which determines the proportions of cement, water, fine
aggregates and coarse aggregates to produce the concrete of required strength,
workability and durability with minimum cost.
Mix design can be divided into following two categories
1. Design mix concrete and 2. Nominal mix concrete.
1. DESIGN MIX CONCRETE:
When the proportions of concrete ingredients are decided by adopting certain
established relationships ( based on assumptions from a lot of experiments) to produce
the concrete it is known as design mix concrete.
In design mix concrete, it is assumed that compressive strength of concrete is totally
dependent on the water-cement ratio.
2. NOMINAL MIX CONCRETE:
When the concrete is produced by taking standard arbitrary proportions of concrete
ingredients, it is known as nominal mix concrete. This method is generally used when
the quality control requirement for design mixes are difficult to execute. As we have
explained for normal work, nominal mix concrete can be designed by taking cement,
fine aggregate and coarse aggregate in the ratio of 1 : n : 2n.
Concrete Mix Proportions For Nominal Mix Concrete:
Grade Of
Concrete
Total quantity of
dry aggregates by
mass per 50 kg of
cement, to be
taken as the sum
of the individual
masses of fine &
coarse aggregates
(maximum) in kg
Quantity of water
per 50 kg of
cement
(Maximum) in
litres
Proportion of fine
aggregate to
coarse aggregate
(By mass)
M 5
M 7.5
800
625
60
45

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M 10
M 15
M 20
480
350
250
34
32
30
HOW TO PRODUCE GOOD QUALITY CONCRETE?
REQUIREMENTS OF GOOD QUALITY CONCRETE:
A good quality concrete needs to be strongest, thickest, workable and most economical
when it is prepared. Following requirements should be considered to produce the best
quality concrete:
1. Use well graded, hard and durable aggregates.
2. Use sufficient quantity of cement to achieve required water tightness and strength.
3. Mix the concrete thoroughly for getting better homogeneity.
4. Keep the water-cement ratio as minimum as possible.
5. Compact the freshly placed concrete to remove air bubbles and voids.
6. Cure the concrete properly at least for 28 days.
7. Maintain the concrete temperature above the freezing point until it becomes hard
enough.
If we fulfill all the above requirements then we can easily produce a good quality
concrete.
CREEP OF CONCRETE
CREEP OF CONCRETE:
Creep can be defined as the elastic and long-term deformation of concrete under a
continuous load. Generally, a long term pressure changes the shape of concrete
structure and the deformation occurs along the direction of the applied load. When the
continuous load is removed, the strain is decreased immediately. The amount of the
decreased strain is equal to the elastic strain at the given age. This quick recovery is
then followed by a continuous decrease in strain, known as creep recovery that is a part
of total creep strain suffered by the concrete.

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Creep Coefficient:
The ratio of the ultimate creep strain to the elastic strain at the age of loading is termed
as creep coefficient. The assumed data of creep coefficient are given below:
Age Of Loading Creep Coefficient
7 days 2.2
28 days 1.6
1 year 1.1
FACTORS AFFECTING CREEP OF CONCRETE:
The factors that affect creep of concrete are similar to the factors affecting shrinkage,
which are as following:
1. WATER-CEMENT RATIO:
The rate of creep is increased with increasing water cement ratio.

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2. HUMIDITY:
It is influenced by humidity and drying condition of the atmosphere.
3. AGE OF CONCRETE:
The rate of creep rapidly decreases with time. The time taken by a concrete structure to
attained creep is 5 years.
4. AGGREGATE:
Aggregates with moisture movement and low elastic modulus cause a large amount of
creep. The rate of creep generally decreases with the increase of the size of
aggregates.
5. ADMIXTURES:
Some admixtures (mainly accelerators) are also responsible for causing creep in
concrete.
OTHER FACTORS:
1. Types of cement.
2. Entrained air.
3. Concrete strength.
4. Improper curing etc.
HOW TO REDUCE SEGREGATION IN CONCRETE
WHAT IS SEGREGATION?
The tendency of separating coarse aggregate particles from the concrete mix is known
as segregation. Generally, it is observed in the plastic stage of concrete. Segregation
mostly occurs in very lean and wet concrete. Honeycomb, sand streaks, porous layers,
rock pockets etc are the results of segregation in hardened concrete.

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CAUSES OF SEGREGATION IN CONCRETE:
Different causes of segregation in concrete are as following:
1. Excessive water content in the mix.
2. Use of poor graded aggregates.
3. Improper design of the mix.
4. Poor compaction of concrete.
5. Over vibration of concrete.
HOW TO REDUCE SEGREGATION IN CONCRETE:
Segregation can be avoided by taking following precautions.
1. The design of the concrete mix should be done properly.
2. Water content should not be added more than the desired amount.
3. Handling, placing, and compaction of freshly mixed concrete should be done
carefully. A proper vibration also reduces the chances of segregation.
4. Concrete should not be dropped from more heights.
5. Air entraining admixtures can be used to enhance the viscosity of concrete.
6. Formwork should be always watertight to prevent leakages.
SETTING PROCESS OF CEMENT
SETTING PROCESS OF CEMENT:
When water is added to cement a reaction takes place to form a paste. In its original
form, the finely ground cement is very sensitive to water. Out of the four main
ingredients C3A, C3S and C2S quickly react with water which finally produces a jelly-
like paste that starts solidifying. The activity of changing from a fluid state to a solid
state is known as setting. Setting is divided into two different categories: Initial setting
time & Final setting time.

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In the next stage of hydration, the cement paste starts hardening due to the reaction
between C3S and C2S with water and gains its strength. The setting action stays more
predominant in first few minutes but after sometimes it becomes dominant. Practically
this solidifying action is required to be delayed because enough time is needed
for mixing, transporting and finally placing the concrete into final location before losing
the plasticity of the mixture.
For plastic concrete, it is necessary to be placed and consolidated before the initial
setting and it should remain undisturbed until the paste becomes a hardened mass.
The concrete gains its strength as rapidly as possible after initial stiffening. The
formwork should be removed after a permissible interval of time and
further construction should be then started. Thus the frost action in cold climate is
minimized.
INITIAL SETTING TIME:
Initial setting time can be defined as the time when the cement paste starts losing its
plasticity. As per IS specification, the minimum initial setting time is 30 minutes for
ordinary portland cement and 60 minutes for low heat cement.
FINAL SETTING TIME:
The final setting is defined as the time taken to reach the cement paste to become into
a hardened mass. As per IS specification, The maximum final setting time for all type of
cement is 10 hours.
HOW TO REDUCE BLEEDING IN CONCRETE?
BLEEDING OF CONCRETE:
Bleeding in concrete
Bleeding can be defined as the tendency of water to rise to the surface of freshly placed
concrete. It is another form of segregation where some amount of water comes to the
concrete surface after placing and compacting, before setting. The water content carries

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some particles of sand and cementing materials. Sometimes bleeding helps to reduce
the plastic shrinkage cracks in concrete.
EFFECTS OF BLEEDING IN CONCRETE:
1. Concrete loses its homogeneity which results in weak and porous concrete.
2. It makes the concrete permeable.
3. It delays the surface finishing in pavement construction.
4. Bleeding of concrete causes high water-cement ratio at the top surface.
5. The bond between two concrete layers become weaker.
6. Pumping ability of concrete is significantly reduced.
HOW TO REDUCE BLEEDING IN CONCRETE:
Bleeding in concrete can be reduced by taking following precautions:
1. Design the concrete mix properly.
2. Add minimum water content in the concrete mix.
3. Add more cement in the mix.
4. Increase the amount of fine particles in the sand.
5. Use a little amount of air entraining admixture.
6. Use more finely ground cement.
SLUMP TEST OF CONCRETE

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CONCRETE SLUMP TEST:
The concrete slump test is an empirical test that measures the workability of fresh
concrete. The test is performed to check the consistency of freshly mixed concrete in a
specific batch. Consistency refers to the ease and homogeneity with which the concrete
can be mixed, placed, compacted and finished. This test is most widely used due to the
simplicity of apparatus and simple test procedure.
The slump test gives satisfactory results for the concrete mix of medium to high
workability and unfortunately, it does not give the correct indication of low workability,
which may give zero slumps. This test is also known as slump cone test.
APPARATUS FOR CONCRETE SLUMP TEST:
1. Mould or slump cone with a height of 300 mm, bottom diameter 200 mm, and top
diameter 100 mm.
2. Standard tamping rod.
3. Non-porous base plate.
4. Measuring scale.
PROCEDURE OF TEST:
1. First, clean the inner surface of the empty mould and then apply oil to it.

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2. Set the mould on a horizontal non-porous and non-absorbent base plate.
3. Fill the mould fully by pouring freshly mixed concrete in three equal layers.
4. Stroke each layer 25 times with the standard tamping rod over the cross-section.
5. After stroking 25 times the top layer is struck off level, now lift the mould slowly in the
vertical direction without disturbing the concrete cone.
6. Use the measuring scale to measure the difference level between the height of the
mould and the concrete sample.
7. The subsidence of concrete is known as the slump and the value of slump is
measured in mm.
TYPES OF SLUMP:
True Slump: The concrete mass after the test when slumps evenly all around without
disintegration is called the true slump.
Shear Slump: When one-half of the concrete mass slide down the other is called the
shear slump. This type of slump is obtained in a lean concrete mix.
Collapse Slump: When the sample is collapsed due to adding excessive water, it is
known as collapse slump.
Zero Slump: For very stiff or dry mixes it does not show any changes of the slump
after removing the slump cone.
ADVANTAGES OF CONCRETE SLUMP TEST:
1. The procedure of slump test is simple and easy than any other workability test.
2. Inexpensive and portable apparatus is required for this test.
3. Slump test can be performed at the construction site as well as in the laboratory.
LIMITATIONS OF CONCRETE SLUMP TEST:
1. The slump test is limited to concretes with the maximum size of aggregate less than
38 mm.
2. The test is suitable only for concretes of medium or high workabilities (i.e having
slump values of 25 mm to 125 mm).

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3. For very stiff mixes having zero slumps, the slump test does not show any difference
in concretes of different workabilities.
Recommended Values Of Slumps For Different Concrete Mixes:
Types Of Concrete Slump Range In mm
1. Heavy mass construction 25-50
2. Pavements 20-30
3. Bridge deck 25-75
4. Beams and slabs 50-100
5. Columns, retaining walls and thin
vertical members etc.
75-150
6. Vibrated concrete 12-25
PRESTRESSED CONCRETE
Advantages and disadvantages of prestressed concrete can be listed as follows:
ADVANTAGES OF PRESTRESSED CONCRETE:
1. Prestressed concrete members are free from cracks and the resistance to the effect
of impact, shock, and stresses are higher than rcc structures.
2. Longevity of prestressed structure is greater than rcc structure because the
reinforcement stays unaffected from outer agencies.
3. High compressive strength of concrete and high tensile strength of steel are used for
prestressing that makes it more economical.
4. Smaller sections can be used for longer span by reducing the section of members.
5. Prestressed members are lighter in weight and easily transportable.
6. It requires a smaller amount of construction materials.
7. The shear resistance of members can be increased by using curved tendons.

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8. Prestressing also reduces the diagonal tension in concrete.
DISADVANTAGES OF PRESTRESSED CONCRETE:
1. The main disadvantage of prestressing is that it requires some special equipment like
jacks, anchorage etc, which pretends the use of prestressing.
2. High tensile steel is required for prestressing that is very difficult to procure.
3. It requires highly skilled workers and should be prepared under expert supervision.
4. It is costlier than other rcc structures.
SHRINKAGE OF CONCRETE
CONCRETE SHRINKAGE OR SHRINKAGE OF CONCRETE:
The volumetric changes of concrete structures due to the loss of moisture by
evaporation is known as concrete shrinkage or shrinkage of concrete. It is a time-
dependent deformation which reduces the volume of concrete without the impact of
external forces.
TYPES OF SHRINKAGE:
The types of concrete shrinkage are listed below:
1. PLASTIC SHRINKAGE:
Plastic shrinkage crack
Plastic shrinkage occurs very soon after pouring the concrete in the forms. The
hydration of cement results in a reduction in the volume of concrete due to evaporation
from the surface of concrete, which leads to cracking.

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2. DRYING SHRINKAGE:
The shrinkage that appears after the setting and hardening of the concrete mixture due
to loss of capillary water is known as drying shrinkage. Drying shrinkage generally
occurs in the first few months and decreases with time.
3. CARBONATION SHRINKAGE:
Carbonation shrinkage occurs due to the reaction of carbon dioxide (Co2) with the
hydrated cement minerals, carbonating Ca(Oh)2 to CaCo3. The carbonation slowly
penetrates the outer surface of the concrete. This type of shrinkage mainly occurs at
medium humidities and results increased strength and reduced permeability.
4. AUTOGENOUS SHRINKAGE:
Autogenous shrinkage occurs due to no moisture movement from concrete paste under
constant temperature. It is a minor problem of concrete and can be ignored.
FACTORS AFFECTING SHRINKAGE:
The shrinkage of concrete depends on several factors which are listed below.
1. WATER-CEMENT RATIO:
shrinkage is mostly influenced by the water cement ratio of concrete. It increases with
the increases in the water-cement ratio.
2. ENVIRONMENTAL CONDITION:
It is one of the major factors that affect the total volume of shrinkage. Shrinkage is
mostly occurred due to the drying condition of the atmosphere. It increases with the
decrease in the humidity.
3. TIME:
The rate of shrinkage rapidly decreases with time. It is found that 14-34% of the 20
years shrinkage occurs in two weeks, 40-80% shrinkage occurs in three months and the
rest 66-85% shrinkage occurs in one year.
4. TYPE OF AGGREGATE:
Aggregates with moisture movement and low elastic modulus cause large shrinkage.
The rate of shrinkage generally decreases with the increase of the size of aggregates. It
is found that concrete made from sandstone shrinks twice than the concrete of
limestone.

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5. ADMIXTURES:
The shrinkage increases with the addition of accelerating admixtures due to the
presence of calcium chloride (CaCl2) in it And it can be reduced by lime replacement.
Other Factors:
 The type and quantity of cement.
 Granular and microbiological composition of aggregates.
 The strength of concrete.
 The method of curing.
 The dimension of elements etc.
TYPES OF CEMENT AND THEIR USES
TYPES OF CEMENT:
Following are the different types of cement used in construction works.
1. RAPID HARDENING CEMENT:
Rapid hardening cement is very similar to ordinary portland cement (OPC). It contains
higher c3s content and finer grinding. Therefore it gives greater strength development at
an early stage than OPC. The strength of this cement at the age of 3 days is almost
same as the 7 days strength of OPC with the same water-cement ratio.
The main advantage of using rapid hardening cement is that the formwork can be
removed earlier and reused in other areas which save the cost of formwork. This
cement can be used in prefabricated concrete construction, road works, etc.
2. LOW HEAT CEMENT:
Low heat cement is manufactured by increasing the proportion of C2S and by
decreasing the C3S and C3A content. This cement is less reactive and its initial setting
time is greater than OPC. This cement is mostly used in mass concrete construction.
3. SULFATE RESISTING CEMENT:
Sulfate resisting cement is made by reducing C3A and C4AF content. Cement with such
composition has excellent resistance to sulfate attack. This type of cement is used in
the construction of foundation in soil where subsoil contains very high proportions of
sulfate .
4. WHITE CEMENT:
White cement is a type of ordinary Portland Cement which is pure white in color and has
practically the same composition and same strength as OPC. To obtain the white color

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the iron oxide content is considerably reduced. The raw materials used in this cement
are limestone and china clay.
This cement, due to its white color, is mainly used for interior and exterior decorative
work like external renderings of buildings, facing slabs, floorings, ornamental concrete
products, paths of gardens, swimming pools etc.
5. PORTLAND POZZOLANA CEMENT:
Portland pozzolana cement is produced either by grinding together, portland cement
clinkers and pozzolana with the addition of gypsum or calcium sulfate or by intimately
and uniformly blending portland cement and fine pozzolana.
It produces lower heat of hydration and has greater resistance to attack of chemical
agencies than OPC. Concrete made with PPC is thus considered particularly suitable
for construction in sea water, hydraulic works and for mass concrete works.
6. HYDROPHOBIC CEMENT:
Hydrophobic cement is manufactured by adding water repellant chemicals to ordinary
portland cement in the process of grinding. Hence the cement stored does not spoiled
even during monsoon. This cement is claimed to remain unaffected when transported
during rains also. Hydrophobic cement is mainly used for the construction of water
structures such dams, water tanks, spillways, water retaining structures etc.
7. COLORED CEMENT:
This Cement is produced by adding 5- 10% mineral pigments with portland cement
during the time of grinding. Due to the various color combinations, this cement is mainly
used for interior and exterior decorative works.
8. WATERPROOF PORTLAND CEMENT:
Waterproof cement is prepared by mixing with ordinary or rapid hardening cement, a
small percentage of some metal stearates (Ca, Al, etc) at the time of grinding. This
cement is used for the construction of water-retaining structure like tanks, reservoirs,
retaining walls, swimming pools, dams, bridges, piers etc.
9. PORTLAND BLAST FURNACE CEMENT:
In this case, the normal cement clinkers are mixed with up to 65% of the blast furnace
slag for the final grinding. This type of cement can be used with advantage in mass
concrete work such as dams, foundations, and abutments of bridges, retaining walls ,
construction in sea water.

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10. AIR ENTRAINING CEMENT:
It is produced by air entraining agents such as resins, glues, sodium salts of sulfate with
ordinary portland cement.
11. HIGH ALUMINA CEMENT:
High alumina cement (HAC) is a special cement, manufactured by mixing of bauxite (
aluminum ore) and lime at a certain temperature. This cement is also known as calcium
aluminum cement (CAC). The compressive strength of this cement is very high and
more workable than ordinary portland cement.
12. EXPANSIVE CEMENT:
The cement which does not shrink during and after the time of hardening but expands
slightly with time is called expansive cement. This type of cement is mainly used for
grouting anchor bolts and prestressed concrete ducts.
STEPS INVOLVED IN CONCRETING PROCESS
Concrete is a construction material made from a mixture of cement, aggregate (sand or
gravel), water and sometimes admixtures in required proportions. Following are the
major steps which involved in concreting process:
STEPS IN CONCRETING:
BATCHING:
The process of measuring different concrete materials such as cement, coarse
aggregate, sand, water for the making of concrete is known as batching. Batching can
be done in two different ways.
1. Volume Batching
2. Weight Batching.
In volume batching the measurements of concrete materials are taken by volume & On
the other hand the measurements are taken by weight in weight batching.
MIXING:
In this process, all the materials are thoroughly mixed in required proportions until the
paste shows uniform color and consistency. Hand mixing and machine mixing are the
two different methods of mixing.

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Note: To achieve optimum quality the materials should be mixed first in dry condition
and then in wet condition.
TRANSPORTATION:
When the mixing is done properly the freshly made concrete is then transported to the
construction site, this process is known as transportation. After that, the concrete is
correctly placed on the formworks. Concrete can be transported to the site location in
two ways
1. Manual Transportation.
2. Mechanical Transportation.
COMPACTION:
Compaction is the process in which the air bubbles are eliminated from the freshly
placed concrete. It is required to increase the ultimate strength of concrete by
enhancing the bond with reinforcement.
CURING:
Curing is the process in which the concrete keeps its moisture for a certain time period
to complete the hydration process. Curing should be done properly to increase the
strength of concrete.
Required Curing days:
Ordinary Sulphate Resistant Cement – 8 Days.
Low Heat Cement – 14 Days.
SELF COMPACTING CONCRETE (SCC) – ADVANTAGES AND
DISADVANTAGES
SELF COMPACTING CONCRETE:
Self compacting concrete is a high-performance concrete which is highly flowable or
self-leveling cohesive concrete that can be easily placed in the tight reinforcement. It is
also known as super workable concrete.
As the name suggests, this concrete compacts by itself without the use of external
vibrators. Some admixtures are used to reduce the yield stress in SCC such as HRWR
(high range water-reducing admixture), and the viscosity is increased by using VMA
(viscosity modifying admixture).

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ADVANTAGES OF SELF COMPACTING CONCRETE:
1. Faster construction and requires less manpower reduce the overall cost of
production.
2. SCC can be placed easily in complicated formwork and dense reinforcement.
3. It is super workable due to its low water-cement ratio, which gives rapid strength
development, more durability, and best quality.
4. As it is self-compacted there is no need to use any vibrator.
5. Bleeding and segregation problems are almost nil.
6. It produces a smooth and well-finished surface at the end of concreting.
7. Thinner concrete slabs can be cast easily.
8. Working procedure is totally safe.
9. It is environment-friendly.
DISADVANTAGES OF SELF COMPACTING CONCRETE:
1. SCC requires high fluidity in tight joints formwork, which slow downs the casting rate.
2. Due to its low water-cement ratio, plastic shrinkage cracks may occur. But this can be
avoided by curing properly.
3. Highly skilled and experienced workers are required for the production of SCC.
4. It is more costly than any other conventional concrete.
HIGH ALUMINA CEMENT ( HAC)

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HIGH ALUMINA CEMENT:
High alumina cement (HAC) is a special cement, manufactured by mixing of bauxite (
aluminum ore) and lime at a certain temperature. This cement is also known as calcium
aluminum cement (CAC).
CHEMICAL COMPOSITION OF HIGH ALUMINA
CEMENTS [IS:6452-1989]:
Alumina (Al2O3) – 39%
Lime (CaO) – 38%
Ferric Oxide (Fe2O3) – 10%
Silica (SiO2) – 6%
Ferrous Oxide (FeO) – 4%
APPLICATIONS OF HIGH ALUMINA CEMENT:
1. This cement is very suitable for under sea applications and sewer infrastructures.
2. It can be used in cold area where rapid strength development is required.
3. HAC is also used in refractory concretes where it requires more strength at very high
temperature.
ADVANTAGES OF HIGH ALUMINA CEMENT:
1. High alumina cement is very reactive and has very high compressive strength.
2. It is more workable than ordinary portland cement.
3. The initial setting time of HAC is about to 3.5-4 hours, and the final setting time is
about to 5 hours.
4. It is extremely resistant to chemical attack.
5. It induces more heat during the setting time, so it can not be affected by frost.
6. It is fire resistant.
DISADVANTAGES OF HAC:
1. The manufacturing cost of HAC is very high.
2. It loses relative strength in humid condition and high temperature.
WHAT IS SHOTCRETE (SPRAYCRETE)

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SPRAYCRETE:
Shotcrete is a mortar or concrete that is pneumatically projected or sprayed by a nozzle
with high velocity on the prepared surface. The whole system is also known as
spraycrete.
TYPES OF SHOTCRETE:
There are basically two types of shotcreting processes
1. Dry-mix process and
2. Wet-mix process.
ADVANTAGES OF SHOTCRETE:
It is very useful and has great advantages over conventional concrete in a new variety
of construction and repair works.
1. Excellent bonding in nature makes the concrete layers very strong.
2. It is more economical than conventional concrete and requires less formwork.
3. The Concrete can be applied by a nozzle from a safe distance.
DISADVANTAGES OF SHOTCRETE:
1. The production cost is very high.
2. Dusting problems.
3. So many wastages of concrete.
APPLICATIONS:
1. Thin overhead vertical or horizontal surfaces.
2. Curved or folded sections like tunnels, canals, reservoirs, or swimming pools, and
pre-stressed tanks.
3. Stabilized rock slopes.
4. Restoration and repairing of old building and fire-damaged structure.
5. Waterproofing walls etc.
FOAM CONCRETE OR LIGHTWEIGHT CONCRETE

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FOAMED CONCRETE:
Foam concrete is a special type of porous concrete, which is highly workable,
lightweight, and low-density material and it can incorporate up to 50% entrained air. It is
produced by cement, water, and air pores (no need of coarse aggregates).
It is also known as foamed concrete, porous concrete, aerated concrete, lightweight
concrete etc. This type of concrete is self-leveling, self-compacting, and can be easily
pumped. The density of foamed concrete can differ from 400 kg/m3 to 1600 kg/m3.
APPLICATIONS :
The application of this type of concrete is increasing day by day.
Foam concrete can be used in
1. Insulating lightweight concrete production.
2. Lightweight blocks and panels.
3. Partitions wall.
4. Prefabricated buildings.
5. Heat and sound insulating.
6. Pipelines etc.
ADVANTAGES OF FOAM CONCRETE:
1. Foam concrete is very economical, it can be produced at very low cost.
2. It is a durable material like rock and it’s deterioration time is very small.
3. This type of concrete has thermal insulation properties.
4. It is fire resistant.
5. Transportation is very easy and can be pumped.
6. It is environment-friendly.