unit-ii basic civil engg

UNIT-IIMATERIALS AND CONSTRUCTION

[A] BASIC CONSTRUCTION MATERIALS

Materials

CementBrick, StoneNatural & Artificial sandReinforcing steel – mild, tor & high tensile steelConcrete types– PCC, RCC, Prestressed & precastIntroduction to smart materialRecycling of materials

Basic materials and their uses

Basic materials used in construction are cement, sand, bricks, stone and steel

Cement –As a binding materialSand- used in mortar or concreteBricks and stones – for masonry work.Steel- for reinforcement concrete and

fabrication of steel doors, windows, fixtures and fastners

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Cement binder a very fine in size Compose of various ratio of chemical When water is added to the cement, a hydration reaction occurs,

producing a solid gel that bond the aggregate particle

•3CaO+Al2O+SiO2+3CaO+SiO2+4CaO

• +Al2O3+Fe2O3+other minerals

Cements

1-CEMENT

lime stone + clay physical properties of cement 1- fineness-OPC-Surface area not less than 2250cm2/gm 2-setting time-a) Initial setting time-30minb) Final setting time-3 to 6 hrs 3-compressive strength -3days-16N/mm2 7days-22 N/mm2 4-soundness-not more than 10 mm

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Cements

The composition on the cement helps determine the rate of curing and the final properties of the concrete

e.g. 3CaO . Al2O3 and 3CaO . SiO2 Rapid setting but low strengths

2CaO . Al2O3 Slowly during hydration but higher strengths

Str

eng

th

Time

•2CaO . Al2O3

•3CaO . Al2O3

•3CaO . SiO2

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Cements

The concrete is expected 28 days for nearly complete curing Some additional curing may continue for years

Types of cement Type 1: General purpose Type 2: Low rate of heat generation, moderate resistance to

sulphate Type 3: Rapid setting Type 4: Very low rate

of heat generation Type 5: Good sulphate

resistance + =

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Cements Reaction

Cement

Water

Sand

Aggregate

•Hydration reaction occur

3CaO . Al2O3+6H2O -> Ca3Al2(OH)12 + heat

2CaO . SiO2+xH2O -> Ca2SiO4 . xH2O + heat

3CaO . SiO2+ (x+1)H2O -> Ca2SiO4 . xH2O +Ca(OH)12 + heat

types of cement

A) Portland cements- 1-ordinary Portland cement-all types of constn,less resistance

to chemical attack 2-rapid hardening Portland cement-after 3 days it is same as 7

days strength of OPC 3- low heat cement –slower rate of reaction 4-sulphate resisting cement- 5-portland blast furnace slag cement-used for dams,bridges &

foundation & more resistant to sulphate attack-decoration & architectural finish,it is costly

6-white and colored cement

B) Super Sulphate cement-resistant to sea water

C) Natural cement- not used D) High alumina cement-it is not attacked by

carbon dioxide therefore for manufacture of RCC pipes

Field testing of Cement

Uses of Cement

1) OPC is used for preparation of cement mortar & constn of bldgs

2) Manufacturing of tiles3) Used as a base in paints4) White & coloured cement uesd in plastering &

decorative finish5) Sulphate resisting cement is used in constn of

surfaces exposed to sulphate action6) construction of highway slabs

2-BRICK

properties of brick 1-size and shape 2-water absorption 3-strength-35 kg/cm2 4-colour

Manufacture of bricks

Selection of site Preparation of clay Moulding of bricks Drying of bricks Burning of bricks

TYPES OF BRICKS

first class second class third class uses of bricks-1) In masonry work2) Flooring material3) Constn of roads4) First class bricks used in face work of the bldg5) Broken bricks used as a aggregate in lime concrete

Stone

Stone is always obtained from rocks, which a solid portion of earth crust.

The rocks quarried from quarries is called as stone.

Quarried stone may be in the from of stone slab, stone blocks, stone aggregates, stone lintels, stone flags.

Stone has to be properly dressed & shaped before it is used at the place of work.

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Aggregate

Gravel & Rock Aggregate must be clean, strong, and durable Angular aggregate particles provide strength due to mechanical

interlocking between particles More surface on angular particles may form voids or cracks The large size of aggregate is preferred Aggregate particles should not be larger than about 20% of the

thickness of the structure or it will cause the holding defect

Classification of rocks

Geological classification:- Igneous rocks, Sedimentary rocks, metamorphic rocks.

Physical classification:- Stratified rocks, unstratified rocks, laminated rocks

Chemical classification:- Siliceous rocks, argillaceous rocks, calcareous rocks

Classification based on hardness of the stones:-Very hard rock, hard rock, medium rock and soft rock.

Uses of stones

Broken stones & stone chips are used in foundation, for floor of buildg. Railway ballast & road metal

Stone blocks are mainly used In walls & for ornamental facing work.

Quartzite is used for rubble masonry, road metalling & also used as a aggregates

Lime stone slabs used for flooring, paving,roofing

Granite:-for bridge abutments, piers & kitchen ota

Marble :- for extreme superior work eg. TajMahal

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Sand

Sand

Sand

It is a form of silica (siliceous+ argillaceous), formed due to decomposition of sandstones due to various weathering actions.Natural (obtained from pits, river beds, shores)& artificial sand (by crushing of stones)Fine sand (sand which pass through IS. 4.75mm size sieve) & coarse sand( that retain on IS.4.75mm size sieve)Increases volume of mortar & makes the mortar economical.

Requisites for Good Sand

1) The gains should be sharp,angular & coarse

2) Sand should be free from clayey materials

3) It should free from salts

4) The grains should be of durable minerlas

Uses of sand

In cement mortar for stone, brick masonry & plastering work.

Used in PCC, RCC. & in Prestressed conc.

Coarser sand used for face plastering for external walls.

STEEL

It is an alloy of iron & carbon, containing carbon- 0.25 to 1.25%

Steel is highly elastic, ductile, malleable, forgeable & weldable.

Generally mild steel: (designated as Fe250, ie. Yield strength in N/mm2), Tor steel: used in RCC. structures (Fe415 & Fe500)) & High tensile steel: (used in prestress conc. costruction.) used in construction.

Steel is of diff. sections like I, T, O, & channel sections

Uses of steel

Structural material in trusses, beams in the form of various sections.Non structural components like stairs, grills, windows & doors.In fabrication of steel pipes, tubes, tanks, ducts etc.Mild steel- used as distribution steel in RCC.Tor steel- used as main steel in RCC.High tensile steel cables used in prestressed conc. Girders.

6-CONCRETE

CEMENT+SAND+COARSE AGGREGATES+WATER

It is workable mixture which can be easily transported, placed & compacted to attend maximum strength.

Properties of concrete depends upon properties of ingredients.

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Concretes

Common construction material Strong hard but brittle Heavy and can not be recycle All ingredients compose of diminishing raw

material

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Concretes Concretes = a particular composite in which both the

particular and the matrix are ceramic material Concretes = Portland Cement + Sand +Aggregate (A cementation reaction between water and the mineral in cement provide a

strong matrix and good compressive strength)

CementsCements SandSand AggregateAggregate

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Properties of Concrete

The water cement ratio

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Properties of Concrete

The amount of air entrainment

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Properties of Concrete

The amount of air entrainment A small amount of air is entrained into concrete during pouring 1-2.5% (sometimes up to 8%) by volume of the concrete may

be trapped by air The entrained air - improves workability of concrete - minimise problems with shrinkage and freeze thaw

conditions, but – cause lower strength

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Concrete Construction

Grades of concrete

M10 1:3:6(culvert, retaining walls, conc. floors)

M15 1:2:4(for general RCC. work) M20 1:1.5:3(water tank & bridge

construction) M25 1:1:2(heavily loaded RCC. structures) M30 and above (heavy structures)

Classification of concrete

1-Plain cement concrete (PCC)2-Reinforced cement concrete (RCC)3-Precast concrete4-Prestress concrete-Pre-tensioning-Post-tensioning

1-Plain cement concrete (PCC)

It is a mixture of cement, fine+coarse aggregates & water

The proportion of these ingredients depends upon grade of mix required & for requirenent of particular job

The PCC is strong in compression & weak in tension. It has good weathering resistance property.

It has good resistance to abrasion.

Uses of PCC.

Used in foundation masonry, Base for foundation, flooring base

In gravity dam & retaining walls

Reinforced cement concrete (RCC)

Mixture of concrete with steel.

Equally strong in tension & in compression

Due to bonding between steel & concrete, stresses are transferred from one material to another material.

Minimum M20 grade of concrete is required for the construction

Uses of RCC.

Concreting for general work like beam, column, slabs, footing etc

Construction of multistoried buildings

Construction of road pavements

Construction of water, oil tanks, bridges,concrete pipes

Machine foundations

Marine structure, hydraulic structure

Precast concrete

Concrete which is cast in separate forms before they are placed in position

It may be casted at building site or some distance from building site

Then with help of equipments & cranes they are transported on site.

Simplest form of precast concrete are hollow & solid concrete blocks for the construction of external & internal walls.

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Reinforced and Pre-post-stressed Concrete

Concrete for construction material Reinforced Concrete Pre-stressed Concrete Post-stressed Concrete

Uses of precast concrete

For casting various building elements such as beam, column, slabs, water tank etc.

For manufacturing of compound poles, electric poles

Fabrication of RCC. Pipes, bridge girder, bridge pier & concrete piles

Prestressed Concrete (P.S.C.)

This is a reinforced concrete in which concrete is subjected to compressive stress before the external load applied to conteract tensile stress caused in concrete due to external loads

Used for M30 & above grades of concrete.

Prestressing is of two types- 1)Pre-tensioning

2) post-tensioning

Prestressing force is applied with the help of hydraulic jacks.

1)Pre-tensioning

In this the tendons are prestressed in place before concrete is poured,

2) Post-tensioning- In this the tendons are given the required tension after the concrete has attained desired strength.

Uses of Prestressed Concrete (P.S.C.)

Girders for bridgesBeams for larger spansRailway slippersElectrical polesUsed in constn of nuclear power stations,steel plants ,piles

ADVANTAGES

1) It permits the use of large spans with shallow member even when heavy loads are encounted

2) High quality materials are used

3) The size of structural member are reduced

Precast blocks

The cement concrete blocks which are cast in rectangular shape mould, which is hollow or solid.

Uses of pre-cast blocks

For light weight structure

In partition walls

As size of precast block is more it required less material & hence economical.

Strong, Durable, & having High strength

Difference between mortar & concrete

Mortar Cement+fine

aggregates+water Mortar used for

masonry work & plastering works, also used for grouting

Concrete Cement+fine

aggregates+coars aggregates+water +water

Used for RCC. & PSC. works

Introduction to smart material

Smart materials are the materials which have the capability to respond to change in their condition or the environment to which they are exposed

Eg. Photocromatic material that change in colour with response to light, alloys & polymers change their shape with response to heat, fluids that changes its viscosity with respect to electric or magnetic stimuli.

Different smart materials

Piezoelectric material

Electrostrictive material

Magnetostrictive material

Shape memory alloy

Optical fibres

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Asphalt Asphalt is bitumen. Bitumen is the organic binder, composed of

HC with low melting point thermoplastic polymers and oils.

Asphalt mix is composite of aggregate and bitumen.

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Asphalt Mix

The aggregate use as in the concrete that should be clean and angular.

Aggregate should have distribution of grain sizes to provide a high packing factor and good mechanical interlock between aggregate grains.

A B

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Operation of Asphalt Mix

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Asphalt construction

Electrostrictive material

This material has same properties to that of piezoelectric material, but only the change is that mechanical change is equal to square of electrical field

Piezoelectric material

When subjected to an electrical field or electrical voltage piezo-electric material will undergo some mechanical change

Wi

Magnetostrictive material

When subjected mechanical field this material under goes mechanical strain

Shape memory alloy

When subjected to thermal field it undergoes some thermal shape change.

Optical fibres

Fibres that use intensity, phase, frequency to measure strain, temperature, electric & magnetic field.

Applications of smart materials

Used in aircrafts & space crafts to measure vibrations & excessive deflections.

Smart concrete used in smart structures to detect smaller cracks.

Catalytic materials that increase or decrease the rate of reaction

All senser materials that can detect signals & adjust sensitivity according to environment

Noise control

Recycling of material

Recycling is the process in which we can utilize the material left on construction site or demolition of structure.

Because of this supply of fresh material required can be reduced

And ultimately reduce environmental pollution

1) Crushed concrete used for road base,general fill or pavement aggregate

2) Asphalt pavement can be crushed & recycled back into asphalt or in hot mix asphalt plant

3) Metal can be melted down & uesd for metal products

4) Bricks can be used in base material in water proofing treatment

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Woods Most familiar materials to mankind. Not a high-technology materials but fantastic. The only material that can be reproduced and give oxygen

to human. Woods is very strong but yet lightweight.

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Woods structure

Wood surface Cross sectional • portion of a round cross

section, clearly reveals a nnual growth rings.

Radial Surface•cutting along a radius

of a round cross section

Tangential Surface•cutting at a tangent to the growth rings, or the surface you would see if you were to view the outside of a log

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Annual Ring trees grow in both diameter and height during growth

periods that are interrupted by periods of rest.

Woods structure

Raining seasonHigh water time

Summer seasonLower water time

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Woods VS water Water caused negative effect to wood

Wood, if not predried, will dry while in use under uncontrolled conditions giving rise to warp, bow, twist, and similar defects.

Wet wood is susceptible to attack by decay and stain fungi. Water must be removed to provide

void space for preservatives if wood is to be treated for prevention

against fungal

attack.

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Wood shrinkage

Wood is an anisotropic material (having different properties in 3 dimensions)

Three Dimensions in which Wood Shrinks

Longitudinal

Shrinkage

= 0.1% to 0.3%

Radial

Shrinkage

= 2.1% to 7.9%

Tangential

Shrinkage

= 4.7% to 12.7%

R RR

T

T

T

L

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Mechanical Properties of woods Wood strength depends on density Given a high efficiency when subject to tensile strength

parallel to the fiber direction

Wood species Tensile // fiber

(MN.m-2)

Tensile radial

(MN.m-2)

Compress // fiber

(MN.m-2)

Compress radial

(MN.m-2)

Maple 108 8 54 10

Oak 78 6 43 6

Pine 73 2 33 3

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Comparison of the specific strength

Specific strength (SF)= strength/density

Material SF strength(kg.m2.s-2)

SF modulus(kg.m2.s-2)

Clear wood 178 2.4E4

Aluminum 127 2.7E4

1020 steel 50 2.7E4

Copper 38 1.4E4

Concrete 15 0.9E4

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Wooden house

Unit-II

Chapter no-4

Sub structure or foundation

Components of Substructure

1) Foundation2) Plinth-3) D.P.C.-Layer between substr &

superstr

foundation

Definition of foundation Bearing capacity ultimate bearing capacity:- It is the capacity of

soil before to failure in shear Safe bearing capacity= ultimate bearing capacity/

factor of safety F.O.S. for temporary structure=1.5 to 2, For

footing= 2 to 3, for piles=2 to 6 & for rocky strata=5 to 10

Sketch of foundation

Functions of foundation

1) To support the str 2) To distribute the load over a wide spread

area to prevent buildg frm any movement 3) To prevent unequal settlement 4) To increse the stability of str. 5) To transfer the load to thw sub soil

Settlement of foundation

Vertical downward movement of structure. Settlement is mainly due to change in volume. Amount of settlement is different for diff. soil &

stata Eg. Clay soil settlement is more, Hard rock less

settlement is there.

Settlement of foundation

Vertical downward movement of structure. Settlement is mainly due to distortion of soil or

change in volume. Amount of settlement is different for diff. soil &

stata Eg. Clay soil settlement is more, Hard rock less

settlement is there.

Types of settlements

1)Uniform settlement _ It will not cause any damage to str,but excessive settlement will damage undergroung utility services like water supply,drainage lines,telephone & electric cables

2) Differential settlement – The diff in magnitudes of settlement at any two points is known as D.S,

Uniform settlement

Differential settlement

Causes of settlement

Loose soil strata below foundation

Excessive expansion & contraction of swelling soil (Black cotton soil)

Excavation & pile driving in neighboring construction

Lowering of water table

due to earthquake

Causes of Failure of foundn

1) Unequal settlement of sub soil2) Withdrawal of Moisture from sub soil3) Horizontal movement of soil mass4) Atmospheric action5)Transpiration of trees & shrubs

Types of foundation Shallow & deep foundation

TYPES OF SHALLOW FOUNDATIONS

1.Spread Footing

2.Wall Footing/Strip footing

3.Isolated Column Footing/Pad footing

4.Combined Footing

5.Cantilever or strap Footing

6.Mat or Raft Foundation

7.Grillage foundation

Deep foundation

1.Spread Footing

Are used to distribute concentrated load from the superstr over a wide area so as to enable

the soil bed to provide safe support

2.Wall Footing/Strip footing

Used for light strs such as garden walls or compound walls

1) Simple footing 2) Stepped footing

3.Isolated Footing/Pad footing

These are used to support individual column. It is most commom used in modern

R.C.C.buildings It may be square,rectangular,circular or

sloped depending upon distribution of load

Isolated Footing

Isolated Footing

4.Strap footing/Cantilever

Sometimes it is not possible to provide footing exactly below the column due to its projection beyond the column in that case seprate footing is provided for interior & exterior column

Strap footing

5.Combined Footing

When loads on adjacent columns are very high or bearing capacity of the soil is less then two columns are grouped together to form combined footing.

When load is same then use rect combined footing

Combined Footing

Combined Footing

6.Raft or mat Foundation

Mat or raft is a heavily reinforced inverse slab placed over the entire area using heavily beams from column to column

Is used when bearing capacity is so less Is used when heavy load on the

foundation

Raft or mat Foundation

7.Grillage foundation

Is suitable when load from the steel columns is very heavy & bearing capacity is so less

Grillage foundation

DEEP FOUNDATION

Pile foundation

A pile is defined as a slender column capable of transferring the structural load to the deep underlying layers.

1) End Bearing pile -When piles transfer the load of bldg to a grater depth

2) Friction pile - When piles transfer the load by means of skin frictionwithout any end

Pile foundation

[B] SUPERSTRUCTURE

It is the part which is above ground level

Superstructure

1) Structural component above plinth upto top

2) Transfers load from upper part to sub str

3) e.g.roof,beam floor

Substructure

1) Structural component below plinth uoto footing

2) Transfers load received from superstr to foundn

3) e.g.footing,basement & foundn

TYPES OF CONSTRUCTION

1-Load bearing structures

2-Framed structures

3-Composite structure

1-Load bearing structures

In this the load of the str is transferred through the walls

Economical upto 2-4 storeys Is used when hard strata is available at shallow

depths E.g,Shaniwarwadwa in pune COEP-these are stone walls If no.of storeys increases wall thk also increases &

reduces carpet area

Load bearing structure

2.Framed structure

Load transferred through a frame of slab,beam,column & footing to the underlying soil.

Constructed more than 100 storeys Used when hard strata is not available at

shallow depth. Speed of constn is fast

Framed structure

3.Composite structure

The outer walls of load bearing type where as column & beams provided internally

Is used for industrial sheds or warehouse where span is so large

Composite structure

TYPES OF LOAD

1.Dead load

2.Live load

3.Wind load

4.Earthquake load

TYPES OF LOAD

1.Dead load-load of material in the constn of bldg, self wt of diff comp.Dead load is calculated by multiplying its volm by unit wt.of material

material Unit wt(KN/m3)

P.C.C. 24

R.C.C 25

Bricks 22

Steel 78

Stone masonry

22

Brick Masonry

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2.Live load

It is movable load acting on the str.i.e.furniture,equipment & machinery

Minimum L.L. is considered in design og bldg dpending upon the type of bldg

Sr No Type of bldg Minm L.L. in KN/m3

1 Residential 2.00

2 Office 2.45

3 Bank & reading room 3.00

4 Class room ,Assembly hall 4.00

5 Dining hall,Store room 5.00

6 factories ,Workshop 7.00

3.Wind load

Is considered in tall bldgs P=kv2

P=Wind pressure in KN/m2

K=Coeff of wind velo.

4.Earthquake load

4.Earthquakeforce = w.α/g

Α = accln due to earthquake =1/20g to 1/20g W = wt.of str G= gravitatational acccln

Comparison betn Load bearing & framed strSr No Load bearing framed str

1 Hard strata at shallow depth

Suitable for any strata

2 Allowed Upto 4 storeys

Multistoreyed

3 Slow & time consuming constn

Fast & speedy

4 Economical upto 2 storeys

Economical upto multisoreyedstoreys

5 It can not resist E.Q. foeces

Resist E.Q.forces

Masonry

Types 1) Brick 2) Stone

Sr No

Brick Stone

1 Used brick & mortar for constn

Used stone & mortar for constn

2 Lesser wall thk.(min 100mm)

Higher wall thk.(300mm)

3 Less durable More durable

4 Less costly & easy to construct

Costly & skilled Labor is required

Fundamental requirements of masonry

1) It should be strong enough to carry the load

2) It satisfies the I.S.for durability & strength 3) Proper bonds to be maintained while

laying masonry 4) It should be in level 5) Thk should be such that it will offer

resistance to water current