Unit 2 Materials of civil engg

7/28/2019 Unit 2 Materials of civil engg.

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Materials & construction

Basic materials: cement, sand, bricks & stones.

Cement is used as a binding material.

Sand is used for mortar & concrete.

Bricks & stones are used for construction of walls.


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Cement

Cement means binding material.

Has property of setting & hardening when mixed

with water to attain strength.

Cement

natural or artificial

Natural cement is manufactured by burning crushing

natural cement stones.

Artificial cement is manufactured by burning ofmixture of argillaceous & calcareous materials &

then grinding is done.


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Clinker Gypsum


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Cement mortar & cement concrete.

Commonly used cement is ordinary portland

cement.

Other types are rapid hardening, low heat,

sulphate resisting, white cement etc.

Uses :

Construction of buildings- opc is used to make

mortar & concrete.

Construction of highway slabs rapid

hardening cement.

Mass concreting work low heat cement.


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Bricks

Made up of clay, used inbuilding construction &architecturalcompositions.

Main contents are silica& alumina.

Moulded bricks are first

allowed to dry & thenburnt in kilns to achievestrength.


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Usually, rectangular in

shape.

Easy availability,

lightweight, cheapness,ease in handling are the

main characteristics of

bricks.


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1st class bricks are well

burnt & having proper

rectangular shape &

size with sharp edges. 2nd class bricks are

irregular in shape & size

with edges not sharp as

1st class brick.


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3rd class bricks are

under burnt bricks.

Fire resistant bricks are

made up of pure fireclay.

These are capable of

resisting high heat

without melting or

softening.


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According to I.S. the size

of brick is 19cm x 9cm x

9cm.

Bricks are laid in variouscourses with frog

upward to form a wall.


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Cement mortar is

placed below, sides of

the brick & inside the

frog.

Soaked in water for 24

hrs.before using in

construction.


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Uses of bricks:

1st & 2nd class bricks areused for all sorts ofwork e.g. constructionof building, bridge piers,tunnel lining, waterstructures.

Used in architecturalcompositions & facework.


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3rd class bricks are usedfor compound wall.

4th or zhama bricks areused for road metal, inwater proofing koba.

Fire bricks are used inacid plants, steel

furnaces & cement kilnetc.


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Stones

Obtained from rock.

Rock quarried from quarries is called stone.

In the form of blocks, aggregates, slabs etc.

It has to be properly dressed & shaped before used. Are classified as per the classification of their parent

rocks.

The rocks may be classified as

Geological : igneous, sedimentary & metamorphicrocks.

Physical : stratified, unstratified & laminated.


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Chemical: siliceous, argillaceous & calcareous

rocks.

Hardness: very hard, hard, medium & soft rock.

Rocks formed by cooling of magma is called igneous

rock. e.g. basalt, granite etc.

Sedimentary rocks are formed by deposition of

broken materials like sand, clay, disintegrated rocks.e.g. sandstone, limestone, slate,etc.

Realignment of minerals due to either temperature

change or pressure change, change the texture of the

rock. This known as metamorphic rock. e.g. marble,

schist.


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Uses :

Broken stones & stone chips are used in foundation,

roofs, floors of the building As road metal & railway ballast.

Mainly used in construction of walls & foundation.

Lime stone slabs are used for flooring, paving & roofing.

Granite used for kitchen ota.

Marble used for decorative & superior type work. e.g.

Taj mahal.


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Sand Form of silica. Formed by decomposition of

sandstones due to various weathering effects.

Natural & artificial sand.

Sand obtained from pits, shores, river beds & sea beds

are known as natural sand.

Sand obtained from crushing of stones is known as

artificial sand.

Divided into two categories depending upon itsfineness.

Sand passing through I.S. sieve of 4.75 mm as fine

sand & retaining on it is known as coarse sand.


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It increases the volume of mortar by making the mortar

economical & prevents shrinkage of cement paste.

Also prevents shrinkage of mortar thereby avoidingcracks during setting.

Fine sand occupies the voids in coarse aggregates.

Uses :

Used in cement mortar for stone, brick masonry &

plastering work.

Used in pcc, rcc & prestressed concrete.

Coarser sand may be applied in form of sand face plasteron external walls of the building.


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Steel Form of cast & wrought iron.

Alloy containing iron & carbon.

Are highly elastic, ductile & weldable.

Mild, tor & high tensile steel are used in various

constructions. Mild steel can be used in various sections i.e. I,

channel, angle & also in the form of round bars as

reinforcement in concrete.

Tor steel is used as reinforcement in rcc works.

Tor steel two grades Fe 415 & Fe 500 & diameters

ranging from 8mm-40mm.


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Concrete

Cement concrete used as a building material.

Fresh concrete is workable & mouldable mixture.

Product of cement, water & air, fine agg. & coarse

agg. Broadly classified into

Plain cement concrete. (pcc)

Reinforced cement concrete (rcc)

Precast concrete

Prestressed concrete.


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Plain cement concrete

Mixture of cement, fine & coarse agg. & water.

Proportion of these ingredients depends upon the

grade of mix.

Grades are M15, M20, M25 etc. M mix & the no.

stands for the characteristic compressive strength ofmix after 28 days. Unit is N/ sq.mm.

e.g. mix 1:2:4 means 1part of cement, 2 parts of fine

agg. & 4 parts of coarse agg. Along with water inproportion to water cement ratio.

Is manufactured by hand mixing or machine mixing.


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It has very less tensile strength & hence not use for

flexural members.

Commonly use in surface levelling course over plinth,below footing etc.


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Reinforced cement concrete

Concrete is weak in tension, so we have to reinforced

it with the tensile material as a steel.

Reinforcement is in the form of mild steel & tor steel

bars. Uses :

Rcc work in buildings i.e. for beams, slabs, footing,

columns etc. In water retaining structures.


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Precast concrete

Individual concrete members of various types, cast inseparate forms before they are placed in thestructure.

Cast on building sites or in casting yards or in precastconcrete factories.

Then transported to the site & placed in position bycranes.

Hollow & solid concrete blocks are the simplest form

used for construction of walls. Controlling measures are there in the factory, precast

members offer the required stregth, durability,attractive appearance.


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At the time of manufacturing reinforcement is placed

in the moulds & then concrete is placed inside the

mould.

Compacting is done by vibrators & then the

members are cured in water tanks.

By using these members we can achieve greater

speed of construction. Uses :

For casting beams, slabs, columns, water tanks

Compound poles, electricity poles, ornamentalstructures.

Bridge girders, bridge piers, concrete piles.


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Prestressed concrete

Concrete with high tensile strength steel wires are

used as a reinforcement.

Prestressed members are generally precast. The

prestressing is done either by pre-tensioning or posttensioning.

Advantages are excellent fire resistance, high

corrosion resistance.

It permits the use of large spans.


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Uses:

Girders for bridges

Beams for large spans

Railway sleepers

Documents

Unit 2 Materials of civil engg