UNIT 3

TESTING PROCEDURES FOR BRICKS

Various types of tests on bricks are conducted to check the qualities of
bricks for construction purposes. Tests on bricks are conducted at
construction sites as well as in laboratories. Bricks are oldest and
important construction materials because of their durability, reliability,
strength and low cost. To produce good quality of structure, good
quality materials are required. To decide the quality of the
materials some tests are to be conducted on bricks. The tests which are
required to find the suitability of bricks for construction purposes are
discussed below.
Types of Tests on Bricks
The following tests are conducted on bricks to determine their suitability
for construction work.
1. Absorption test
2. Crushing strength test
3. Hardness test
4. Shape and size
5. Color test
6. Soundness test
7. Structure of brick
8. Presence of soluble salts (Efflorescence Test)
1. Absorption Test on Bricks
Absorption test is conducted on brick to find out the amount of moisture
content absorbed by brick under extreme conditions. In this test, sample
dry bricks are taken and weighed. After weighing these bricks are placed
in water with full immersing for a period of 24 hours. Then weigh the
wet brick and note down its value. The difference between dry and wet
brick weights will give the amount of water absorption. For a good
quality brick, the amount of water absorption should not exceed 20% of
weight of dry brick.
2. Crushing Strength or Compressive Strength Test on Bricks
Crushing strength of bricks is determined by placing brick in
compression testing machine. After placing the brick in compression
testing machine, apply load on it until brick breaks. Note down the value
of failure load and find out the crushing strength value of brick. The
minimum crushing strength of brick is 3.50N/mm2.if it is less than 3.50
N/mm2, then it is not useful for construction purposes.
3. Hardness Test on Bricks
A good brick should resist scratches against sharp things. So, for this test
a sharp tool or fingernail is used to make scratch on brick. If there is no
scratch impression on brick then it is said to be hard brick.
4. Shape and Size Test on Bricks
The shape and size of bricks are very important considerations. All bricks
used for construction should be of the same size. The shape of bricks
should be purely rectangular with sharp edges. Standard brick size
consists of length x breadth x height as 19cm x 9cm x 9cm. To perform
this test, select 20 bricks randomly from brick group and stack them
along their length, breadth and height and compare. So, if all bricks are
similar size, then they are qualified for construction work.
5. Color Test of Bricks
A good brick should possess a bright and uniform color throughout its
body.
6. Soundness Test of Bricks
The soundness test of bricks shows the nature of bricks against sudden
impact. In this test, 2 bricks are chosen randomly and struck with one
another. Then the sound produced should be a clear bell ringing sound
and brick should not break. Then it is said to be a good brick.
7. Structure of Bricks
To know the structure of brick, pick one brick randomly from the group
and break it. Observe the inner portion of brick clearly. It should be free
from lumps and homogeneous.
8. Efflorescence Test on Bricks
A good quality brick should not contain any soluble salts in it. If soluble
salts are there, then it will cause efflorescence on brick surfaces. To
know the presence of soluble salts in a brick, place it in a water bath for
24 hours and dry it in shade. After drying, observe the brick surface
thoroughly. If there are any white or grey color deposits, then it contains
soluble salts and is not useful for construction.
STEEL REINFORCEMENT
Steel reinforcement are steel bars that are provided in combination with
plain cement concrete to make it reinforced concrete. Hence these
structures form steel reinforced cement concrete structure (R.C.C). Steel
reinforcement is commonly called as ‘rebars’.
Need for Steel Reinforcement
Plain concrete is weak in tension and strong in compression. Tensile
property for concrete structures is obtained by incorporating steel
reinforcement. The steel reinforcement is strong in both tension and
compression. The tensile property provided by the steel reinforcement
will prevent and minimize concrete cracks under tension loads. The
coefficient of thermal expansion of steel reinforcement and concrete
are similar in that they undergo similar expansions during temperature
changes. This property will ensure that the concrete is subjected to
minimal stress during temperature variations. The surface of the steel
reinforcement bars is patterned to have a proper bond with the
surrounding concrete material. The two main factors that provide
strength to the concrete structures are steel and concrete. The design
engineer will combine both the elements and design the structural
element in such a way that the steel resists the induced tensile and shear
force, while the concrete takes up the compressive forces.
Types of Steel Reinforcement
The steel reinforcement used in concrete construction is mainly of 4
types. They are:
1. Hot Rolled Deformed Steel Bars
2. Cold Worked Steel Bars
3. Mild Steel Plain Bars
4. Prestressing Steel Bars
1. Hot Rolled Deformed Bars
Hot rolled deformed bars are most commonly used steel reinforcement
for R.C.C structures. As the name says, the hot rolling of the
reinforcement is undergone leaving certain deformations on its surface
in the form of ribs. These ribs help to form a bond with the concrete. The
typical yield strength of hot-rolled deformed bars is 60000psi.
2. Cold Worked Steel Bars
A cold worked reinforcement bar is obtained by letting the hot rolled
steel bars to undergo cold working. In the cold working process, the bars
will undergo twisting and drawing. The process is performed at room
temperature. The cold worked steel bars do not undergo a plastic yield
thus have less ductility when compared with hot rolled bars.
3. Mild Steel Plain Bars
The mild steel plain reinforcement bars do not have ribs on their surface.
They have a plain surface. These bars are used for small projects where
the major concern is the economy. The tensile yield strength of these
bars has a value of 40000psi.
4. Prestressing Steel Bars
The prestressing steel reinforcement are steel bars used in the form of
strands or tendons. Multiple strands are employed in concrete in order
to perform the prestressing action. The strands are made of multiple
wires, either 2 or 3 or 7 wire strands. The wires used here are cold
formed and have a high tensile strength ranging from 250000 – 270000
psi. This high strength helps to effectively prestress the concrete.
Advantages of Steel Reinforcement
Steel reinforcement is a reinforcing choice compared to other
reinforcing materials due to its unique advantages. They are:
1. Compatibility with Concrete: The fresh concrete is placed on the
formwork mold already prepared with reinforcement. The steel
reinforcement won’t float in concrete during the concrete placing
procedure. Hence, steel reinforcement does not demand special
tying up with formworks.
2. Robustness of Steel Reinforcement: The steel bars are robust in
nature and have the ability to withstand the rigors, the wear and
tear during the construction activities.
3. Bent Property of Steel Reinforcement: The steel bars once
manufactured to standard size, can be bent to the required
specifications. Hence fabricated steel bars are delivered easily to
the site.
4. Recycling Property: The steel reinforced left over after the service
life of a structure is recycled again and used for new construction.
 5. Easily Available: Every region of a country will have a steel supplier
or manufacturer. Hence steel reinforcement is easily available.
FINE AGGREEGATE
Fine aggregate is the essential ingredient in concrete that consists of
natural sand or crushed stone. The quality and fine aggregate
density strongly influence the hardened properties of the concrete.
The concrete or mortar mixture can be made more durable, stronger
and cheaper if you made the selection of fine aggregate on basis of
grading zone, particle shape and surface texture, abrasion and skid
resistance and absorption and surface moisture.
Role of Fine Aggregate in Concrete Mix
Fine aggregates are the structural filler that occupies most of the volume
of the concrete mix formulas. Depending on composition, shape, size
and other properties of fine aggregate you can have a significant impact
on the output. The role of fine aggregate can be described in few points:
• Fine aggregates provide dimensional stability to the mixture.
• The elastic modulus and abrasion resistance of the concrete can be
influenced with fine aggregate.
• Fine aggregates quality also influences the mixture proportions and
hardening properties.
• The properties of fine aggregates also have a significant impact on
the shrinkage of the concrete.
Properties of Fine Aggregates
While making the selection for appropriate aggregate to be used in
particular concrete mix, few properties needs to be considered, such as:
• Void content: How much amount of cement paste will be required
for the mix eventually depends on the empty spaces between the
aggregate particles. Always keep in mind that angular aggregates
 increase the void content, whereas well-graded aggregate and
improved grading decreases the void content.
• Shape and texture: Size and shape greatly influence the quality of
the concrete mix. For the preparation of economical concrete mix,
you should know that rough-textured, angular, and elongated
particles require more water for the formula. However, you will
need less water to produce workable concrete when the
aggregates are smooth, rounded compact aggregate.
• Absorption and surface moisture: The fine aggregate
density depends on the inside solid material and void content, thus
you need to measure the absorption rate prior to ensure how much
water will be required in the concrete mixture.
• Abrasion and skid resistance: In order to minimize the wear in high
traffic areas, such as heavy-duty floors and pavements you can
consider the relative measure when the fine aggregate is rotated in
a cylinder along with some abrasive charge.

COARSE AGGREGATE
Coarse aggregates refer to irregular and granular materials such as sand,
gravel, or crushed stone, and are used for making concrete. In most
cases, Coarse is naturally occurring and can be obtained by blasting
quarries or crushing them by hand or crushers. It is imperative to wash
them before using them for producing concrete. Their angularity and
strength affect the concrete in numerous ways. Needless to say, the
selection of these aggregates is a very important process.
Size of Coarse Aggregate
Materials that are large enough to be retained on the 4.7mm sieve size
usually constitute coarse aggregates and can reach a maximum size of
63mm.
The size of coarse aggregates affects several aspects of the concrete,
mainly strength and workability, and the amount of water needed for
the concrete mix. It also helps determine how much fine aggregate is
needed to produce a concrete batch. The bigger the size, the smaller is
its bondable surface area for cement, sand and water; the less water and
fine aggregate is needed with concrete mixes.
The size of the coarse aggregate determines the cement to water ratio.
Less water means a stronger mix, but it also becomes less workable. One
important factor is the space between TMT Bars. The aggregate needs
to be smaller than the space between internal reinforcements. This will
allow the aggregate to pass between the rebar and settle evenly
throughout the structure.
Grading of Coarse Aggregate
The grading of aggregate is its classification according to the average size
of the particles. It is important that the grading is kept constant for
concrete batches. The aggregate particles need to be of a consistent size
for an even grading. Similar shaped coarse aggregates make the
concrete more cohesive and uniform.
Shape of Coarse Aggregate
The characteristic of the parent rock from which coarse aggregates is
produced and also the type of crusher used to influence the shape of the
aggregates. They may be round, angular or completely irregular.
Rounded aggregates, such as gravel, have the lowest water demand due
to their lower surface area. They also have the lowest cement
requirement. This makes rounded aggregates more economical;
however, the bonds they form are not as strong as those of angular
aggregates.
Angular ones require more water and cement because they have a
higher surface area. This can make a concrete batch more expensive, but
it is also stronger and more durable. Irregularly shaped aggregates have
similar properties to angular aggregates, but if the particles are too flaky
or elongated, it can result in segregation in the concrete.
Strength of Coarse Aggregate
The strength of the actual material will determine the final strength of
the concrete mix. Some rocks and stones are stronger than others thus,
giving higher resistance to cracking and crushing. Granite, for example,
is far stronger than limestone. Therefore, it is a common aggregate used
by contractors.
Water absorption of Coarse Aggregate
Aggregate absorption is the water it soaks up in the concrete batch. Dry
aggregates suck up any water in the concrete, which can lead to a dry
and brittle mix. That is why contractors keep their aggregates damp
before mixing a batch of concrete. Coarse aggregates can absorb water
up to five percent of their weight. This means that contractors need to
add extra water to a concrete mix if the aggregate is dry.
These properties determine the final quality and strength of a concrete
batch. The size, grading, shape, strength and water absorption of the
aggregate all influence the final concrete mix in various ways, so
contractors need to keep an eye on these variables.
The properties of coarse aggregate will determine the final quality and
strength of a concrete batch. The size, grading, shape, strength and
water absorption of the aggregate all influence the final concrete mix in
various ways, so contractors need to keep an eye on these variables.
PHYSICAL IDENTIFICATION OF TESTS FOR SOILS
There are several physical tests that can be performed on soils to
identify their properties. Some of the most common tests include:
1. Sieve analysis: This test is used to determine the particle size
distribution of a soil sample. It involves passing the soil through a
 series of sieves of different sizes and measuring the amount of soil
retained on each sieve.
2. Atterberg limits: These tests are used to determine the moisture
content at which a soil changes from a solid to a plastic state (plastic
limit) and from a plastic to a liquid state (liquid limit).
3. Proctor compaction test: This test is used to determine the
maximum dry density and optimum moisture content of a soil
sample by compacting it in a standard mold under controlled
conditions.
4. California Bearing Ratio (CBR) test: This test is used to evaluate the
strength and stiffness of a soil sample under varying moisture
content and compaction conditions. It is commonly used to assess
the suitability of soils for road and pavement construction.
5. Permeability test: This test is used to determine the rate at which
water can flow through a soil sample under a given pressure
gradient.
6. Consolidation test: This test is used to determine the rate and
magnitude of settlement of a soil sample under a static load.
These tests can provide valuable information about the physical
properties of soils, which can be used to determine their suitability for
various engineering applications.