Basic Civil and Mechanical Engineering Unit I Construction Materials Presentation

Unit 1

Construction materials

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Bricks

Stones

Cement

Mortar

Cement Concrete

Plastics

Manufacture of bricks

Preparation of brick earth.

Moulding of bricks

Drying of bricks

Burning of bricks

Preparation of brick earth

• Loose soil which contains impurities, isremoved for about 20 cm depth.

• Earth is then dug out from the ground, spreadand weathering is done for a week time.

• The clay is then mixed with suitable ingredientsby tilting the clay and ingredients up and downina kiln.

• Water is added to clay to make the whole massof clay homogeneous and plastic.

Moulding of bricks

• Hand moulding: It is done in arectangular box with open at top andbottom. Box is made up of wood or steel.

Hand moulding further classified into,

(a) Table moulding (b) Ground moulding

(a) Table moulding

• Done by the experienced supervisor

• Bricks are moulded on the table and sentto next stage.

(b) Ground Moulding

• Small portion is cleaned and leveled.

• Find sand is sprinkled over it.

• Mould is dipped in water and kept onthe ground and the clay is pressed byhand

Machine moulding:• Used in mass production

of bricks (huge quantity)• These machines contain a

rectangular opening of sizeequal to length andbreadth of the brick.

• The tempered clay isplaced in the machine.

• The tempered clay comesout as through the openingunder pressure, hence it iscut to the required shape.

Drying of bricks

• Bricks are staked in the yard with 8 to 10 bricksin a row.

• Bricks are dried for a period of 5 to 12 days.

• Some times bricks are dried by hot gases fromkiln.

• But artificial drying produces warps on thebricks

Burning of bricks

• It imparts hardness and strength to bricks andmakes them dense and durable.

• Burning should be uniform, because unburntbricks remain soft and hence cannot carryloads.

• Overburnt bricks become brittle and breakeasily.

• Burning of bricks done in clamp or kilns.

Qualities of good bricks

Well burnt, Sharp edges, copper coloured, freefrom cracks

Should give a good ringing sound

Bricks should not break when dropped from aheight of 1m

Bricks should have a low thermal conductivity

The minimum crushing strength should be

3.5 N/mm2

Average weight of bricks should be 3 – 3.5 kg.

Building stones are obtained fromrocks

Rocks are classified into igneousrocks, sedimentary rocks andmetamorphic rocks.

Igneous rocks are formed bycooling of the molten materialsbeneath the earth’s surface.

Stones from igneous rocks areharder.

Granite which is widely used inconstruction of building is a goodexample.

Sedimentary rocks are formedby deposition of weatheringproducts on existing rocks.

Deposits in layers and whenthe load is applied along thelayers these rocks easily split.

Metamorphic rocks are formedin the change in character of thepre existing rocks.

These rocks will also be hard, ifthe basic rock is igneous rock.

Quarrying of stones

It is the process of extracting stone blocks fromexisting rocks.

In general, it is done some depth below the topsurface of rock, where the effects of weathering arenot found.

Quarrying is done by digging, heating or wedging.

In soft rocks, like lime stone and marble stones areobtained by digging, heating or wedging by handtools.

In hard and dense rocks, stones are obtained byblasting using explosives.

Dressing of stones :

Stones have irregular shape after quarrying

The process of cutting the stones to a regularshape and size and the required surface finish iscalled dressing of stones.

Testing of stones :

Hardness test : Stone is tested by a pen knife which willnot be able to produce a scratch on a hard stone.

Acid test :

• Stone is kept in sulphuric acid and hydrochloric acid fora week time.

• The corners of the stones with high alkaline content turnroundish and loose particles will get deposited on itssurface.

• Such stones are not suitable for smoky atmosphere.

Qualities of good stones

The crushing strength of stone should be greater than 100N/mm2

Stones must be uniform in colour.

Light coloured stones resist weathering action in a betterway.

When the stones are used for roads, it must be hardenough to resist wear and tear.

A good building stone must have specific gravity greaterthan 2.2

Manufacturing of cement

Cement is obtained by burning the mixture ofcalcareous and argillaceous materials at a veryhigh temperature.

The calcined product is known as clinker

A small quantity of gypsum is added to theclinker and is pulverised into very fine powderknown as cement.

On setting, cement resembles a variety of sandstone in found portland in England and istherefore called Portland cement.

Types of cement

Rapid Hardening cement

It is similar to port land cement.

It develops strength rapidly

This cement is used where high strength is required atinitial stages.

Quick setting cement

This cement sets very quickly.

It is due to reduction of gypsum content in normalportland cement.

It is used for underwater construction.

Types of cement

Coloured cement

It contains 5 to 10 percent of pigment with normalportland cement for colouring.

This is used for aesthetic purposes

White cement

The colour of cement is white

It has the same properties of portland cement

It is used for architectural purposes and formanufacturing coloured concrete, flooring tiles etc.,

Types of cement

Masonry cement

It has great plasticity, workability and waterretentivity

It is used for masonry constructions in makingmortars and plasters.

Qualities of a good cement

The colour should be uniform

Cement should be cool when felt with hand.

If a small quantity of cement is thrown in to abucket of water, it should sink.

Cement should be free from lumps.

The initial setting time should not be less than 30minutes and the final setting time should bearound 10 hours.

Mortar is the term used to indicate a paste prepared byadding water to a mixture of binding material (cement orlime) and the fine aggregate.

Classification of mortar :Bricklaying mortar:

It is used for brickwork and walls.

Depending upon the working conditions and the type ofconstruction , the binding materials for the mortar isdecided.

Finishing mortar :

These mortars include common plastering work andornamental effects.

Cement or lime is used as the binding material forordinary plastering mortar.

Special mortars

Fire resistant mortar :

It is prepared by adding aluminous cement to the finelycrushed powder of fire bricks.

The usual proportion is one part aluminous cement totwo parts fire brick powders.

Light weight mortar:

It is prepared by adding materials such as saw dust,wood powder, etc.,

Other materials could be asbestos, fibres, coir etc.,

This mortar is sued for sound proof and heat proofconstruction.

Uses of mortar

To bind the building units such as bricks, stones, etc.,into a solid mass.

To carryout plastering work on the exposed surfaces ofmasonry.

To form even and soft bedding layer for building layer.

To fill up the cracks detected in the structure duringmaintenance process etc.,

Classification of sand

(i) Natural sand (ii) Artificial sand

Natural sand

It is the sand carried away by river water and quarriedfrom river bed.

Artificial sand

Produced by crushing and breaking stones into differentsizes of stone in a crushing plant.

Qualities of good sand

Sand should be clean, hard, durable and dry.

Free from mica, chemical salts, organic and inorganicimpurities and other foreign matters.

Uses of sand :

It is used for making mortar and concrete

It is used as filling in the basement of buildings.

Used as the binding material on the top of bituminuousroad.

DEFINITION : It is a mixture ofcement, sand, crushed rock and waterwhich when placed in the skeletonforms and allowed to cure becomeshard like a stone.

Uses of concrete: It is used for the construction of

Reinforced Cement Concrete flat roofslabs.

Coloured concrete is used forornamental finishes in buildings, packlanes, separating lines of road surfaces.

Light weight concrete is used in multistorey constructions.

Reinforced Cement Concrete (RCC):

Plain concrete is very weak intension and cannot be used inconstruction of roof slabs, beamsetc.,

Because the bottom fibres of themare subjected to tensile stresses.

A combination of concrete and steelis known as Reinforced CementConcrete and widely used.

Advantages of Reinforced Cement Concrete :

It is versatile building material can be used forcasting members of any shape.

It has good fire resistance and weatheringactions.

Easy to construct

RCC is tough and durable

Steel contains carbon upto a maximum of 1.5percent. Based on the carbon content, steel areclassified into,

Low carbon steel (Mild steel) with carboncontent 0.25 percent.

Medium carbon or medium hard steel withcarbon content between 0.25 – 0.70 percent

High carbon steel or hard steel having carboncontent 0.70 – 1.5 percent.

Uses of Low carbon steel (Mild steel):

Low carbon or mild steel is used in structural works suchas trusses, angles and plates.

It is also used in RCC works as plain or twisted rods.

Uses of Medium hard steel:

It is used in the manufacture of rails, chisels, hammers,boiler plates etc.

Uses of hard steel :

It is used in earth moving or mining equipments.

Used for manufacturing cutting steel

Torsteel rods :

Torsteel rods are twisted ortorsioned deformed rods.

Ordinary steel rods areround plain bars made ofmild steel.

Both plain bars and tor steelrods are used in RCC roofslabs, beams, columns.

Wood rendered suitable for use as structural materials bysawing and cutting is called as a timber.

Seasoning of timber:

It is the process of reducing the moisture in the timber.

Seasoning of the timber reduces timber gettingdecomposed or decayed.

It is done by air seasoning , boiling water seasoning orkiln seasoning.

Defects in timber :

Timber used in construction should be free from cracks,knots, worm holes, upsets etc.

Advantages of timber inconstruction :

Timber is light, strong anddurable.

It takes shocks and impactswithout rupturing.

It offers a good electricalresistance.

It has good sound absorption andthermal insulation characteristics.

Uses of timber

Timbers are used for manufacturingstructural members such as beams, lintelsand joints.

It is used for manufacturing door andwindow frames and panels.

It is used for flooring also in auditorium

It is used for making partitions, panelingetc.

Used for interior decoration

Plywood is obtained by gluing threemore veneers. Veneers are thinsheets of wood.

The veneers are obtained as slicesfrom different woods.

The are placed in different layers inany odd number, the grainssuccessive veneers being at rightangles

The layers thus arranged are pressedto form a plywood

Advantages of plywood :

Plywood are light and strong

Available in different sizes.

Not affected by moisture and temperature. Hence lessshrinkage or expansion.

Elegant appearance.

Uses of plywood :

Used in manufacturing the partitions.

Sliding doors and cabinet doors.

Ward robes and cup boards

False construction

Substances which becomes plastic on the application of heat andpressure are called plastics.

Thermo plastics :

Thermo plastics become soft on heating and hard on cooling.It can be melted and solidified a number of times withoutmuch change in their properties.

Eg : Polyvinyl chloride, polythene, perpex

Thermosetting plastics :

Thremosetting plastics are moulded under heat and pressureto form objects.

The product obtained possesses totally different appearance,different chemical and physical properties.

Resistant to further application of heat.

Eg : phenol formaldehyde, urea formaldehyde

Uses of plastics as a building material :

Used for manufacturing door and windowframes.

Used for preparing insulating materials.

Used for manufacturing lighting fixtures.

They are used for making wall covering, floorcovering.

Foamed plastics are used as right slabs.

K.V. Natarajan, Dr. M. Kantha basu, N. Venkatesan,N. Vasudevan, Basic Civil and MechanicalEngineering, Dhanalakshmi Publications, 2011.

G. Shanmugam, M.S. Palanichamy, Basic Civil andMechanical Engineering, Tata McGraw Hillpublishers, 2010.

Prepared by

A.R. Pradeep Kumar

Associate Professor / Mechanical

Email : dearpradeepkumar@gmail.com

Website : www.arpradeep.tk

Basic Civil and Mechanical Engineering Unit I Construction Materials Presentation

normal portland

reinforced

low carbon

medium hard

week time

torsteel rods

existing rocks

manufacturing

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