Construction Materials, Prakash

8/6/2019 Construction Materials, Prakash

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Chapter- 11.0 General

1.1 Introduction to the subject

As far as construction material is concern, it seems worthful to know abouMaterial Science because it deals with the study of properties, characteristics anapplication of Engineering materials. Thus Material Science is the branch of appliescience dealing aforesaid properties of solid Engineering Materials. Solid EngineeriMaterials are classified as: Metals/Alloys Ceramic Materials Organic Materials Compisite Materials

So, Construction Material mainly deals with properties and application of thoswhich are used for the construction purpose. Construction Materials also be called Engineering Material as they satisfies various Engineering Requirements.

Thus Engineering Materials or Construction materials deals with the study omaterials in respect of followings: Sources, composition and properties. Manufacturing methods and testing. Utility in the various field of engineering and technology. Modern techniques being developed for handling and using materials to materializ

economical and safer.

1.2 Types of Construction MaterialsEngineering Materials can be classified as following:1. Civil Engineering Materials2. Electrical Engineering Materials:

Example: Copper, aluminium, iron and steel etc. --------Conductors :Asbestos(A fibrous amphibole; used for making fireproof articles), bakelite(type plastic), mica, varnishes, air etc. -------------- Insulator :Iron, Nickel, cobalt, etc. ---------Magnetic materials .

3. Mechanical Engineering Materials: Example: Cast iron, steel, lubricating materials etc.

As far asConstruction Materialis concern, it fully deals about Civil EngineeringMaterials, the types of which are: Building Stones Bricks and clay product Cementing materials: Lime and Cement Concrete, Mortar Timber

Prepared By : Er. Prakash Bdr. Adhikari 1


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Other types of Construction Materials are :1.0 Metals: It may be further divided as:

(i) Ferrous Metals : Metals containing iron are called Ferrous Metals,example: cast iron, wrought iron and steel.

(ii) Non-ferrous Metals : Metals not containing iron are called as Non-ferrous

metals, example: Copper, aluminium, zinc etc.(iii) Ferrous Alloys : Product of metal and any other element is calledferrous alloy, example: silicon steel, high speed steel, spring steel etc.

(iv) Non-ferrous Alloy : Product of non-ferrous metal and other element iscalled non-ferrous alloy, example: brass, bronze, duralumin etc.

2.0 Non-metals:Building stones, cement, concrete, rubber,plastic, Asbestos etc.3.0 Alloys:Product of more than one elements are known as Alloys. Steel is an alloy of

iron and carbon.4.0 Ceramics Materials:Ceramics are phases, in general ceramics are inorganic non-

metallic materials. Example: silica, sodalime glass, concrete cement, ferrites(i.e. solidsolution), garnets(i.e. mineral), MgO, CdS, ZnO, SiC, etc.

5.0 Organic Materials:These materials are derived directly from carbon. They usuallyconsist of carbon chemically combined with hydrogen, oxygen or other non-metallsubstances. Example: Plastics, PVC, polythene, fibre: terylene, nylon, cotton, naturand synthetic rubbers, leather etc.

1.3 Properties of Materials

Following properties of material will be discussed here:

1.0 Physical Properties2.0 Thermal Properties3.0 Mechanical Properties.4.0 Chemical Properties and5.0 Electrical Properties.

1.0 Physical Properties:It consist followings:(a) The melting or freezing point: The melting or freezing point of a pure metal is

defined as temperature at which the solid and liquid phases can exist in stablequilibrium. When a metal is heated to melting point, the liquid phase appears, anif more heat is supplied, the solid melts completely at constant temperature. Thfreezing of a pure liquid exhibit the phenomenon of super-cooling. Use of mercuin thermometer, manometers arises from its low melting point, while use otungsten filaments in incandescent light bulbs in possible because of its extre-mhigh melting point.

(b) Boiling Point: The boiling point of a liquid is the temperature at which its vapour pressure equals to one atmosphere. The boiling points of the metals except mercuare high. The boiling point of zinc is 907oC & cadmium is 865oC .

(c) Density: Mass per unit volume is termed as the density. In MKS, its unit is kg/m3Mass per unit volume of a material in its natural state is called Bulk Density. Som building materials are having following values of bulk densities:



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Material Bulk Density(a) Granite 25 to 27 kN/m3(b) Clay Brick 16 to 18 kN/m3(c) Sand 14.5 to 16.5 kN/m3(d) Gravel 14 to 17 kN/m3

(e) Limestone(dense) 18 to 24 kN/m3

(f) Concrete (light) 5 to 18 kN/m3(g) Concrete (heavy) 18 to 25 kN/m3(h) Steel 78.5 kN/m3(i) Plastic material(porous) 0.2 to 1.0 kN/m3(j) Pinewood(conifer tree) 5 to 6 kN/m3

Note: The ration of bulk density of a material to its density is called density IndexThe density index of most of building material is less than unity.

(d) Porosity: The degree by which the volume of material is occupied by pores isindicated by the term porosity. The strength, bulk density, durability, thermal con-ductivity etc. of a material depends on its porosity.

(e) Water absorption: It is the ability of material to absorb and retain the water. Itmainly depends on the volume, size and shape of pores present in the material.(f) Water Permeability: It is the capacity of material to permit water to pass through it

under pressure.(g) Fire resistance: It is the ability to resist the action of high temperature without

losing its load bearing capacity.(h) Durability: It is the property of material to resist the combined action of

atmospheric and other factors.(i) Refractorness: It is the ability of a material to withstand prolonged action of high

temperature without melting or loosing shape.(j) Chemical Resistance: It is the ability to withstand the action of acids, alkalies, gases

and salt solutions.

2.0 Thermal Properties:It consist followings:(a) Linear coefficient of expansion: The linear coefficient of expansion of a solid is

defined as the increase in length per unit length, for each degree rise intemperature.

(b) Thermal conductivity: The thermal conductivity of a metal is defined as the number of kilojoules of heat that would flow per second through a specimen 1sq. in crosssection and 1m in length when the temperature gradient is 1oC. Silver & copper show the highest thermal conductivities of all metals. But some metals like GermaSilver exhibit very low conductivities and hence find the applicable where healosses by metallic conduction should be kept to a minimum.Silver is the bestconductor and copper is next.

(c) Thermal resistivity: It is the reciprocal of thermal conductivity.

3.0 Mechanical Properties: Mechanical properties of engineering materials are such properties, which defines the behaviour of materials under the action of load oforce.



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The study of mechanical properties is very important in order to select thematerial for various engineering requirements. It consist followings:

(a) Elasticity: It is the temporary deformation of materials under the action of load.This phenomena takes places within elastic limit of materials. Steel is said to bmore elastic than Rubber, because elastic limit of steel is higher than rubber

Elasticity is always desirable in metals used in machine tools and other structuramembers.(b) Plasticity: It is permanent deformation of a material under the action of load. The

plasticity of a metal depends up on its nature and environmental conditionLead(Pb) has good plasticity even at room temperature.

(c) Malleability: It is defined as the property of the metal by which if we can able to geta thin sheet without fracture that property of metal is called its malleability. Goldhas good property of malleability. The following metals have malleability indecreasing order-- Gold, Silver, Aluminium, copper, tin, platinum, lead, zinc, ironnickel.

(d) Ductility:

It is defined as an ability of metal to draw into a thin wire without fracture. Under the application of load, before fracture, ductile material gives sufficienwarning.

Materials whose % of elongation is more than 15 are always referred as ductilmaterial.

During machining(cutting), formation of continuous chips indicates that thmaterial is ductile.

Materials which withstand high tensile stress are called ductile materials. Silver (Ag), copper (Cu), Aluminium (Al), Mild steel etc. are the example o

ductile materials.(e) Brittleness:

Under the action of load, if all metal undergoes for instant fracture withougiving any information to the operator then that property of metal is called a brittleness.

Materials whose % of elongation is less than 5 are always referred as brittlmaterials.

During machining, formation of discontinuous chips indicates that metal i brittle.

Materials which withstand high compressive strength are called brittle. Concrete, Asbestos, glass, cast iron are the example of brittle materials.

(f) Hardness: It is defined as an ability of metal by virtue of which if the metal givesresistance to cutting, bending, drilling, abration etc. by harder bodies then thiability is known as its hardness.

If the metal is very hard its corresponding melting point and bond strengthis also higher.

(g) Stiffness: It is defined as the property of metal by virtue of which, if a metal givesresistance to deformation (deflection) then we can say the metal is stiff.

Under the application of load, if a metal deflects with a low angle ofdeflection, then its corresponding stiffness is higher and vice versa.



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(h) Creep: Continuous deformation of a metal under the application of steady(constant) load with high temperature defines creep in metal.

ORAbove 0.4 Tm(melting temperature) plastic deformation in metal takes pla

ce. This deformation is a function of time with the application of steady load. This

phenomenon is called creep.In short, it can be remembered as LTTEWhere, L = Load

T = temperatureThese two are constant parameters.

T = TimeE = Elongation

These two are variables.(i) Fatigue (Indurance): It is defined as an ability of metal by virtue of which how

much of cyclic load (alternate load), a metal can withstand before its fractureFatigue is only considered when the metals are subjected to cyclic stress o

alternating loads. If a metal withstand more cyclic load before fracture then itcorresponding fatigue strength is higher.(j) Toughness: It is defined as an ability of metal by virtue of which how much energy

it can sustain (observe) before its fracture under the action of loading.If a metal has high toughness then its corresponding impact strength is

also higher, vice versa.It has already been understood that steel is more tough than cast iron. In

other word, ductile metals are having more toughness as compare with brittlematerials.

(k) Resilience: The amount of energy that a metal can stored within it before fractureunder the action of loading is called resilience.Proof Resilience:The maximum amount of energy that can be stored within elastic limit of the metis called its proof resilience.Modulus of resilience:Proof resilience per unit volume of material defines modulus of resilience.

(l) Strength: If a metal can withstand higher stresses before its fracture under theaction of loading, it gives its strength.

4.0 Chemical Properties:Its study is essential as most of the construction material when comes in contact wiother substances with which they can react, tend to suffer from chemical deterioratioIt comprises:(a) Chemical composition: It provides the constituents of any material. For example,

the chemical composition of cement are CaO, SiO2, Fe2O3, etc.(b) Acidity or alkalinity: It gives the chemical character (i.e. either acidic or alkaline)

of the material, so that use of materials may be defined.(c) Corrosion Resistance: Corrosion is a gradual chemical or electrochemical attack



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on a metal by its surroundings so that metal is converted in to an oxide, salt osome other compound. The reasons for corrosion may me air, moisture, industriatmosphere soils, acids, bases and salt solutions etc.

5.0 Electrical Properties:It comprises:

(a) Electrical Resistivity: It is the property of a material due to which, it impedes or Resists the flow of electricity through it.Resistivity, = R*A / l

Where, R = Resistance of a conductor (ohms)A = Area of the conductor sectionl = Length of the conductor.

(b) Electrical Conductivity: The conductivity ( ) is the reciprocal of electrical resisti-vity.

Conductivity, = l / = l / R*AThe dimension of are ohm-1 cm-1. Electrical conductivity is that electrical prop-erty of material due to which the electric current flows easily through the material.

(c) Temperature coefficient of resistance: It is usually employed to specify the vari--ation of resistivity ( ) with temperature.Temperature coefficient of resistance is

T = (( - o) / o)* 1 / (T-To)Where,

= resistivity at temperature T o = resistivity at temperature To, andT and To are temperature in degree Kelvin.

(d) Dielectric strength: It is the insulating capacity of a material against high voltage.It is an insulation. A material having high dielectric strength can withstand suffic-iently high voltage before its break.

(e) Thermoelectricity: If two dissimilar metals are joined and this junction is thenheated, a small voltage in the milivolt range is produced, and this is known athermoelectric effect.

END OF CHAPTER 1 (ONE)



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CHAPTER 22.0 Characteristics of construction materials

2.1 Stress and Strain:

These two are the resistance of the body to deformation due to theapplication of external forces.

Stress: Stress is the force per unit area of a body. If P is the total load acting on thoriginal cross-section area Ao, then stress is given by relation:

Stress, = P/Ao

Strain: Strain is the deformation produced per unit length of a body. It is the ratio ofchange in length of the specimen to its original length. If l is the change in length andlo is the original length of the sample, then strain is given by relation:

Strain, = l / lo = longitudinal strainStrain can be lateral strain or shear strain depending up on the type of loading. It has nunit.

Hookes Law: This states that, within elastic limits, the relationship between stress andstrain is constant and is represented by E (Youngs modulus of elasticity).Thus, Stress Strain

i.e. = E

E = / = Proportionality Constant Since,E is the characteristics of the material and is different for different

materials and for different nature of stresses, it is calledModulus of the Materials. When tensile and compressive stresses are used, it is calledYoungsModulus of Elasticity(E).

When shear stresses and strains are used, the costant is calledModulus of rigidity (G).

When volumetric stresses and strains are used, the constant is called Bulk Modulus (K).

Poissons Ratio: When a test sample is stressed by a uniaxial force, it is strained in thedirection of force and also in a direction perpendicular to the direction of the force. Tstrain in the direction of force is called Longitudinal strain and that perpendicular to

as lateral strain.The ratio of lateral strain to the longitudinal strain of the test sample isknown as Poissons Ratio. Mathematically,

Poissons ratio = Lateral Strain / Longitudinal Strain= l/m = Constant



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It is an important elastic constant and its value for most common engineering materiais lies between0.3 to 0.6

Stress-Strain Relationship:It is the graphical representation of the data obtained from

tensile/compression test of any material where stress and strain are kept along Y-ax

and X-axis respectively. During tensile test, the specimen is subjected to increasinstresses and corresponding change in length (i.e. strain) is measured by strainmeasuring devices.

2.2 Comparative stress-strain curves for various engineering materials

There are mainly two types of stress-strain curves:(a) For brittle materials.(b) For ductile materials.

To derive the stress-strain diagram for the material, a test for compression o

tension should be carried out. Stress applied and the corresponding strain caused are be noted to plot the stress-strain relationship. Followings are the stress-strain diagrafor various brittle engineering materials:



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2.3 Stress-Strain diagram for ductile material (Ductile Metal)

This diagram is mainly derived from the tensile test of metal (i.e. ductile

materials). From the test, stresses applied and the corresponding strain caused are notand are plotted to be obtain stress-strain curve.Y

Stress ( )

O Strain ( )Stress-Strain curve for metal (ductile materials)

A : Proportionality Limit (Proportionality Point)B : Elastic Limit (Elastic Point)C : Upper Yield Point, E : Lower Yield PointD : Ultimate Tensile Stress (or Maximum tensile stress or Tenacity)F : Fracture Point (or Breaking Point)ER : Elastic RegionPR : Plastic RegionFR : Fracture Region.

From the curve it has been observed that, the stress corresponding to poinF is known as Breaking (Fracture) stress. The stress at F is less than at point C because the formation of neck at D reduces x-sectional area of the specimen whiresults to the specimen to fail suddenly at point F even with small load (stress). Thcurve CF is called Nominal or Engineering Curve because it only used for aengineering applications in real practice.



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The greater value of will represent the material to be more elastic. Thehigher position of Upper Yield Point C will represent the material to be more harThe higher position of point D will represent the material to be more strong anductile. Simillarly, position of breaking stress will represent brittleness or toughness the materials.

Detail information about stress-strain curve. (For Understanding) From above figure, the following information can be obtained:(a) The graph OA indicates that the ratio of stress to strain is constant and hooks la

holds good from O to A. From A curve is slightly deviates from straight line (imeans stress strain up to A only). After this point proportionality is not constant,thus point A is known as Proportionality Limit.

(b) The graph AB is very small curve which indicate that the ratio of stress to the strais not constant but slightly changes. In this portion metal continue to behav perfectly elastic. Thus, point B is known as Elastic Limit.

(c) The graph BC indicates that the strain increases more quickly than the stress compare to OA and AB. It may be noted that if the load on the specimen isremoved, the elongation from B to C will not disappear, but it will remain as a permanent set. Thus, point C is called Yield Point. (upper one).

(d) In graph CD, very small length of curve from C (i.e. CE) is almost horizontal. indicates that strain increases without any appreciable increase in stress. Thihappens as there is a sudden elongation of specimen due to creep.

(e) The remaining portion of the curve between CD is upward which indicates that tspecimen regains some strength and thus higher value of stresses are required fohigher strain. The curve rises up to maximum limit indicated by the point D. Thstress corresponding to point D is called Ultimate Tensile Strength or Tenacity.

is the measure of tensile strength of the materials.(f) The graph DF is a downward curve which indicates that, a neck is formed reducinthe x-sectional area of the specimen. Now it needs low stress to continue extensiotill fracture takes place at F.

FRACTURE

Fracture refers to the breaking of the components into two or more pieceeither during service or during fabrication due to the application of external loadFactors which are responsible for fracture are:

Rate of impact

Temperature Geometry of the materialsThere are following types of fracture:

Brittle Fracture Ductile Fracture and Creep Fracture.

2.4 Griffiths theory for brittle fracture (or Mechanism of brittle fracture)



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It has been understood that the stress required for the material at which ifractured is only a small fraction of its cohesive strength. Therefore Griffith suggethat the low observed strength were due to the presence of micro-cracks, which actsthe point of concentration.

In order to explain this mechanism of brittle fracture, Consider a crack oelliptical cross-section in rectangular specimen of glass which is subjected to an axitensile stress() as shown in above figure.Let,

= Applied tensile stressc = Half crack length

When tensile stress is applied to the specimen, then the stress is distributedthroughout the specimen in such a way that the maximum stress occurs at its tips.Thexpression for maximum stress at the tip of the crack is given by the relation:

max= 2 (c/r)Where,

r is radius of the curvature at its tip.

We also know that before fracture some amount of energy is always storedin the material, which is called Elastic Strain Energy and is given by the followinrelation:

Ue = - ( c2 2) / EWhere,

Ue = Elastic Strain EnergyE = Youngs Modulus of Elasticity

A negative sign(-) indicates that the elastic strain energy stored in the material ireleased as the crack formation takes place. According to Griffiths theory such a crawill propagate when the released elastic strain energy is sufficient to provide thsurface energy for the creation of new surfaces.


TipTip

Elliptical Crack

2c

c


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If be the specific surface energy per unit area in J/m2, then the surfaceenergy due to the presence of crack of length 2c is given by the relation:

Us = 2*(2c*1)* = 4c

Thus, Total Energy, U = Ue + UsAccording to Griffith, such crack will propagate and produce brittle fractur

when an incremental surface energy is compensated by a decrease in elastic straienergy. Mathematically,

d(U)/dc = 0d{(- c2 2) / E + 4c}/dc = 0-2c2 / E + 4 = 02c2 / E = 4 = (2E / c)

where, is stress required to cause fracture.

For the material having and E are constant, then

= (2E / ) * 1/c = k * 1/c , where k is Griffiths constant

Thus, 1/c

Therefore fracture stress() is inversely proportional to the square root ohalf crack length.



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From the above figure we can concluded that the surface energy is linear in nature anstrain energy is quadratic in nature. In total energy curve when dU/dC=0.

2.5 Principles of hardness and impact tests of engineering materials.

Hardness Test

Aim To know the hardness of the metals. In other word, to know the resistanceagainst penetration, abration, cutting etc. of a metal.

Hardness test can be conducted by the following methods:1. Vickers Hardness Test (VHN Test)2. Rockweels Hardness Test (R B or Rc)3. Brineils Hardness Test (BHN Test)4. Knoops Hardness Test (KHN Test)

Note:(A) For test no. (1), (3) and (4), hardness is determined by the corresponding numbe

like VHN(Vickers Hardness Number), BHN(Brineils Hardness Number) anKHN(Knoops Hardness Number).

(B)For test no. (1), (3) and (4), penetrators are used along with loads for the evaluatioof hardness.

V.H.N. = 1.854P/L2Where,

P = Load in NA = Surface area of indentation in mm2L = Length in diagonal in mm = Angle between opposite face of the pyramid.

B.H.N. = P/A = Load on the ball / Area of indentation

B.H.N. = P/ (D/2*(D-(D2-d2))Where,

P = Load in kND = Diameter of steel ball in mmd = Diameter of the indentation in mm

K.H.N. = P / (unrecovered projected area of the impression in mm2)Where,

P = Load in N

(C) For Rockweels hardness test, hardness number is automatically reads from the diindicator either by RB or by Rc. B represents B-scale and C represents Cscale, which are available in the indicator. Penetrators are used for this test.



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Rockweels B number isR.H.B = 130- depth of indentation in mm / 0.002

Rockweels C number is

R.H.C = 100- depth of indentation in mm / 0.002Impact Test

Aim To know the toughness of the metal under the application of impact load. To determine the notch sensitivity of a metal under the application of impact load

In practice Impact test is conducted by several means but all the machinesworks on the same principle. The very effective impact testing machine by which bettimpact test results can be found out are given below:

1. Charpy Testing machine (Charpy Test)2. Izod Testing Machine (Izod test)

1.0 Charpy Test

Specimen for charpy test is shown in fig. below and in this test the specimeis fixed inside the machine like simply supported beam having a notch at its centre.

Size of specimen = (55*10*10)mm

Machine set up


55 mm

10 mm

10 mm Notch

2 mm45ospecimen

specimennotch

Anvil (support)

Striking Edge(S.E.) or Pendulum


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Figure

ProcedureSpecimen is placed over the anvil as shown in above figure. When the

pendulum arm is released from known value of angle, then the striking edge (S.E.) pendulum strikes the specimen with high velocity at the opposite side of the notcTherefore striking edge may cause fracture for the specimen. After breaking, th pendulum rises on opposite side through the same angle. Neglecting all the mechaniclosses during the test, the energy required to fracture this specimen can be found ofrom the difference of Initial Energy and the Residual (final) energy of Striking Edge.Thus,

Energy required for Fracture = I.E. R.E.Where, I.E. = Initial Energy

R.E.= Residual Energy

Calculations



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Where,R : Length of pendulum armW : Weight of striking Edge (S.E.)

: Angle of fallH : Height of fall : Angle of riseh : Height of rise

Now,Initial Energy (I.E.) = WH

= W(R-OA)I.E. = WR WR Cos ------------------- (1)

AndResidual Energy (R.E.) = Wh

= W(R- OB)

R.E. = WR WR Cos ---------------(2)We know thet, at fracture,Fracture Energy = I.E. R.E.

= WR WR Cos - WR + WR Cos [from 1 & 2]Thus, F.E. = WR(Cos - Cos )2.0 Izod Test

This test is conducted by the same machine which is already used for charptest, the test calculations for fracture energy is exactly like that of charpy test.

But, in this case the dimensions of specimens is different while the strikingedge will strike the specimen at the same side of notch. The view of machine set up aspecimen size is shown in figure below. In this case the specimen is placed inside thmachine like cantilever beam.


75mmm

28mmm 22mm6mm

Striking Edge

AnvilSpecimen

2 mm45o

10mm

10mm


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Size of specimen : (75*10*10)mm Notch angle : 45o Notch depth : 2 mm

Factor affecting Impact ResistanceDimensions of the specimen Notch detailsGrain size of the specimenTemperature of the specimenImpact velocity of load (i.e. hammer)

END OF CHAPTER TWO



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CHAPTER 3 Basic Construction Materials

3.1 Sieve Analysis

Introduction

Sieve Analysis (or Dry Mechanical Analysis) is the method of grading ofthe construction material (basically Aggregate). It is also called particle size distributionaggregate.

Basically there are three types of gradation of the aggregates:Well gradedUniformly (or poorly) graded andGap Graded

For the construction purpose well graded material either for fine aggregateor for coarse aggregate is preferred as it consist almost all size of grains and gives compaor dense concrete. But, poorly graded aggregate consist same size of grains, so it is nconsidered as a good materials. Whereas gap graded consist the presence of some size particles.

Procedure

Sieve Analysis is useful for coarse grained material which are more than 7micron in size.

The sample of aggregate is sieved through a stack of sieves. The sieve witlargest opening is placed on the top of the stack. Downward, the size of the sieve openireduces progressively. For the analysis of fine aggregate, the arrangement of sieve sifrom top to bottom should be in following order:: 3.35mm, 2.36mm, 1.18mm, 600 micron, 300 micron, 150 micron and 75 micron.

But, for the analysis of coarse aggregate, the arrangement should be likethis: 80mm, 63mm, 50mm, 40mm, 31.6mm, 25mm, 20mm, 16mm, 12.5mm, 10mm6.3mm and 4.75mm.

Below the stack of sieve a pan is to be placed to collect the particles passingthrough smallest sieve opening. The sample is placed on the topmost sieve and whole seto be shaken till each sieve contains constant amount of sample. The retained amount sample in each sieve is weighed. The cumulative weight and % finer passing each sieve calculated and plotted against the sieve opening (in log scale) to produce theGrain Size

Distribution Curve.The particle size corresponding to the % finer than can be obtained from

the gradation curve & denoted as D p. It is defined as the particle size such that p% of soilare smaller than D p. For example:D10 = 0.22 mm means that 10% of the total weight of the sample consist of particles smallthan 0.22mm.



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The general slope of the grain size distribution curve can be described by thterm Coefficient of Uniformity (Cu)

Cu = D60 / D10

A smaller Cu means a steeper curve which is the result of concentration o

the particlensize in smaller range (particles are more uniform)The aggregate is said to be well graded if 1 < Cc < 3, where Cc is Coefficient of curvatureCu > 4 for gravel/aggregateCu > 6 for sand

If aggregate fails one or both of these criteria, it is considered as PoorlyGraded (or, Uniformly Graded).

The coefficient of curvature(Cc) indicates general shape of the gradationcurve and is defined by:

Cc = (D30)2 / (D10*D60)

Observation Table

S.N. SieveSize

Wt. of emptysieve

Wt. of sieve +sampleretained

Wt. of sampleretained

% of sampleretained

Cummulative %of sampleretained

% finer =100% -col.(7)

Remarks

The gradation curve for different gradation will be:


Grain size(opening of sieve)

% finer For gap graded

For well gradedFor poorly graded


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3.2 Stone, its type and properties

Stones are naturally occurring compact, solid and massive materials that

make the crust of the earth. Technically, stones are called asrocks. These rocks occur in agreat variety and possess suitable properties often find use in building construction.Stone have been used in all types of construction since time immemorial

The pyramids of Egypt, The Eiffel Tower, The Temple of Jagannathpuri, the Tej Mahathe Red Fort, thousands of grand palaces in different part of world, the Great China Waand hundreds of historical buildings in each big country are made of stones.

Types (Classification) of Stones

(A) Geological Classification

This classification based on the mode of formation of rock. These are:(a) Igneous Rock: The molten magma when gets exposed to the outside cooling effect,solidifies in the form of rock, which is known as Igneous Rock. Eg. Granite, Basalt. It m be of following types:

(i) The Plutonic Rocks: These are formed at great depth below the earth surface due tosolidification of molten magma. Granite, Syenites and gabbros are the example of plutonrock.

(ii) The Volcanic Rock: These are formed on the surface of earth fromlava coming outfrom numerous volcanoes that erupt from time to time. Example: Basalt and Trap.

(iii) The Hypabyssal Rock: These are formed at shallower depth, about 2 to 3 km below thesurface from magma that could not come out as lava. They show crystals that are partcoarse and partly fine in size. Eg. Porphyries.

(b) Sedimentary Rock: These rocks are formed by transportation, deposition andcementation of disintegrated rocks, vegetable matter and clay due to the atmospheric actisuch as rain, wind and temperature. These are usually formed at the bottom of rivers, lakand sea. Limestone, Sandstone are belongs to this category. Depending up on the way of formation, sedimentary rock may be of followings:

(i) Clastic Rocks: These are formed by deposition and consolidation of disintegratedsediments and fragments from the previous rock in suitable river basins, lake basins and basins etc. Example:Sandstone.

(ii) Chemically formed rocks: These are formed by precipitation from river, lake andseawater by evaporation. Some components of previous rocks are taken in solution durithe process of weathering and erosion. Water may get saturated with these compounds w



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passes of time and precipitates them, which forms rock. Limestone, gypsum, anhydrite androck salt are example of this category.

(iii) Organically formed sedimentary rocks: As we know, great variety of life exists ingreat water bodies (like sea, river lakes etc.) which have their hard parts made up of bon

(which are a mixtures of Ca and Mg carbonets). These parts get accumulated at prop places on the seafloors after death of these animals. Gradual deposition of such parts wthe passes of time form sedimentary rock like Limestone .

(c) Metamorphic Rock: When igneous and sedimentary rocks are subjected to a very largeheat and pressure, a new type of rock will form due to effect of such high temperature a pressure. The newly formed rock is known as Metamorphic rock. The process of formimetamorphic rock is known as metamorphism.Marble, slate are the example of this rock.

(B) Chemical classification:

On the basis of dominant chemical composition, following three groups of rocks acommonly recognized:

(i) Siliceous Rocks: Rocks having Silica (SiO2) as a predominant mineral component (i.e.> 50% of rock composition). Granite, Sandstone and Gneisses belongs to this category.

(ii) Calcareous Rocks: Rocks having calcium carbonate as a predominant minerals.Limestone, dolomite and marble belongs to this group.

(iii) Argillaceous Rocks: Rocks having clay as a predominant minerals. Shales, Slates andSchiests are example of Argillaceous rock.

(C) Structural (Physical) Classification:

(i) The massive or Unstratified rocks: These occurs in huge mass without showing anylayered structure. All Igneous rocks are belongs to this group.

(ii) The stratified rock: These occurs in distinct layers of same or different colour andcomposition. All sedimentary rocks are belongs to this category.

(iii) Foliated rocks: Rocks with the development of well defined bands of differentcomposition due to high temperature and pressure. All metamorphic rocks are the beexample of this category.

Properties of stones:



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For ensuring durable, cost-effective and aesthetically appealing construction, the followi properties of stone are desirable to consider:(1) Compressive Strength: It is the load bearing capacity of stone expressed as themaximum load per unit area at which the stone starts cracking. i.e c = P/A. For comm building compressive strength should be within the range of 280 to 2800 kg/cm2.

(2) Transverse Strength: It is the resistance a stone offers to bending loads. This propertyis commonly determined by Modulus of Rupture R. For different stones R-values varfrom 20 to 300 kg/cm2.(3) Shear strength: Stones used in pier, column have to withstand shearing load. Hence itmust posses sufficient shearing strength. Shearing strength of common building stone lin between Kg/cm2.(4) Hardness: It is the capacity of stone to resist scratching or abration. Limestone wearout easily compared to quartzite. The hardness of stone depends up on their minercomposition. Generally igneous rock have high hardness than other rock.(5) Toughness: It is defined as the capacity of stone to withstand impact loads. Stoneshaving good toughness are used in foundations under heavy machines where vibratio

may be a common phenomenon. They should be hard and strong also.(6) Water absorption: It may be defined as the quantity of water absorbed (in % by weight) by a stone till its saturation. Thus absorption value of % means that a stone on saturatican hold % water by weight. But water absorption value of good stone should not be mothan % by weight. In cold climate, water inside the pores may freeze (expand up to % volume) and exert disintegration stresses.

Absorption value of some common stone after immersion in water for houare:Granite : 0.3 to 1.5% Sandstone : 5 to 8%Limestone : 4 to 10% Marble : 0 to 0.5%(7) Appearance: Aesthetically, light colour are preferred in the exterior of buildings.Appearance has no significance when stones are used in fopundation.(8) Workability: Stones in their natural form may have low workability due to presence ofoutcrops in quarry. Thus, after dressing workability can be achieved. The process of givi proper shape, dimension and surface finish to a raw stone before it is fit for use construction is called Dressing.(9) Durability: It denotes the period in years for which a stone may stand practicallyunaltered after being used in construction. A durable stone must

Withstand loads imposed on it for the entire period. Must keep up original appearance even in exteriors Must resist effect of heat and cold. Must not suffer deterioration & decomposition by gases.

A stone will be durable when, It has quite high strength value for the designed loads It has uniform, close packed, dense structure, with very low water absorptio

values I t is made up of very hard and resistant mineral constituents.



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3.3 Aggregates

Aggregates are those chemically inert materials which when bonded by

cement paste, forms concrete. Aggregate influence the strength of concrete to a great exte because they constitute bulk of the total volume of concrete. Aggregates are derived froigneous, sedimentary and metamorphic rocks.

Functions (Advantages) of the Aggregates

There are following functions of the concrete: It provides concrete to behave like artificial stone. It is cheaper materials than cement. It gives the body to the concrete, reduces shrinkage and effect economy. It provides durability to the concrete. It increases the density of the concrete. It prevents segration of concrete. It provides 70 to 80% of volume of concrete (i.e. provides bulk of concrete). It increases workability of the concrete.

Qualities (or Requirements) of Ideal (good) Aggregates

Followings are the most important qualities of the aggregates: It must be of proper shape and of well graded . It should be free from dust and should resist heat and freezing. It must be hard and strong enough to bear compressive and normal tensile load

on ordinary concrete. It must be chemically inert , i.e. should not react with cement or any other

aggregate or admixture used for concrete making. It should possess sufficient hardness to resist scratching and abrasion in the set

hardened concrete. It should possess sufficient toughness to withstand impact and vibratory loads. It should be free from impurities, inorganic or organic in nature, which can effe

adversely on the quality of concrete. It should be capable of producing an easily workable plastic mixture on

combining with cement, water and other aggregate.

Classification of Aggregates

There are mainly four basis of classification of aggregates:1. Classification based on Geological origin.2. Classification based on Size3. Classification based on specific gravity or unit weight.4. Classification based on shape.



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1.0 Classification based on Geological origin.

Under this classification the aggregate may be divided in to followings:(a) Natural Aggregate

(b) Artificial (processed) Aggregate(c) By product Aggregate

(a) Natural Aggregate: These includes all those types of fine and coarse aggregates thatare available in almost ready to use form from natural resources. Example are sands froriverbeds, pits and beaches and gravel from river banks. Natural aggregates are generaderived from their formation like: Igneous rock, sedimentary rock and metamorphic rock

(b) Artificial Aggregate (processed aggregate): These are specially manufactured for usein making quality concrete and includes broken pieces of burnt clay, shale etc. The brok bricks of good quality provide a satisfactory aggregate for the mass concrete, but n

suitable for RCC work. If the crushing strength is less than 30 35 MPa, the bricaggregate is not suitable for water proof construction and for road work as well.

(c) By-product aggregate: These includes the material obtained as waste from someindustrial products which are suitable for being used as aggregates. CINDER obtained fro burning of coal in locomotives and KILN & SLAG obtained from blast furnaces as scuare best example of this category. Concrete made with blast furnace aggregate will havgood fire resisting qualities. 2.0 Classification based on Size

The size of aggregates used in concrete varies from few centimeter or morto few microns. According to this basis, aggregates are classified as:

(a) Fine aggregate(b) Coarse aggregate(c) All-in-aggregate

(a) Fine aggregate: It is a aggregate most of which passes through 4.75mm I.S. sieve.Sand is generally considered to have a lower size limit of about 0.07mm and is thuniversally available & commonly used natural fine aggregate. Material between 0.06 mto 0.002 mm is classified as silt and still smaller particles as clay. The fine aggregate m be of following type-(i) Natural sand: i.e. fine aggregate resulting from natural disintegration of rock or thatwhich has been deposited by stream or glacial agencies.(ii) Crushed sandstone: i.e. fine aggregate produced by crushing hard stone.(iii) Crushed gravel sand: which is produced by crushing natural gravel.

(b) Coarse aggregate: The aggregate must of which retained on 4.75 mm I.S. sieve. Gravelfrom river beds form the best coarse aggregates in making common concrete. The coaraggregate may be one of the following types:



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(i) Crushed Gravel or stone obtained by crushing of gravel or hard rock.(ii) Uncrushed gravel or stone resulting from natural disintegration of rock, or (iii) Partially crushed gravel or stone obtained as a product of the blending of above twtypes.

The coarse aggregate is described by its nominal size, i.e. 40mm, 20mm

16mm and 12.5mm etc. For example, a graded of nominal size 12.5mm means aaggregate most of which passes the 12.5mm I.S.sieve.

(c) All-in-aggregate: Sometimes combined aggregates are available in nature consistingdifferent fraction of fine and coarse aggregates, which are known as All-in-aggregate. such cases there is no need to mix sand and stone chips separately. The all-in-aggregatare not generally used for making high quality concrete.

3.0 Classification based on Shape

The particle shapes of aggregates influence the properties of fresh concret

more than those of hardened concrete.Depending up on the particle shape the aggregate may be classified as:1.0 Rounded2.0 Irregular (or, partially rounded)3.0 Angular 4.0 Flaky (Elongated)

1.0 Rounded AggregateThe aggregate with rounded edge (not spherical) particle (e.g. gravel, sand

has minimum voids ranging from 32 to 33%. It gives minimum ratio of surface area to tvolume and hence requires less cement paste to make concrete.

The only disadvantage is that the interlocking between its particle is lessand hence the development of bond is poor making it unsuitable for high strength concrand pavements.

2.0 Irregular AggregateThe aggregate having partly rounded particles and partly other has higher %

of voids ranging from 35 to 38%. It requires more cement paste for a given workabilitThe interlocking between particles, though better than that of obtained with the roundaggregate, is inadequate for high strength concrete.

3.0 Angular AggregateThe aggregate with sharp, angular and rough particles (crushed rock) has

maximum % of voids ranging from 38 to 40%. The interlocking between the particles good, thereby providing a good bond. The aggregate requires more cement paste to maworkable concrete of high strength than that required by rounded aggregates. Thaggregates are suitable for high strength concrete and pavement subjected to tension.



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4.0 Flaky Aggregates (Elongated)

An aggregate is termed as flaky when its least dimension (thickness) is les

than 3/5th

of its mean dimension. The mean dimension of the aggregate is the average othe sieve size through which the particle passes and retained. The particle size is said to elongated when its greatest dimension (length) is greater than 9/5th of its dimension.

4.0 Classification based on specific gravity or unit weight.

According to this aggregates are classified as followings:(a) Normal (standard) weight aggregate(b) Heavy weight aggregate(c) Light weight aggregate

(a) Normal (standard) weight aggregateThe aggregates which have the specific gravity 2.5 to 2.7 are known as Normal weight aggregate. The commonly used aggregate like gravel, crushed rock such basalt, quartz, sandstone, limestone, brick ballast produces the concrete with unit weigranging from 23 to 26 kN/m3 and crushing strength at 28 days lies between 15 to 40 MPIt is used for general RCC and PCC work.

(b) Heavy weight aggregateThe aggregate having sp.gr. ranging from 2.8 to 2.9 are known as Heavy

weight aggregates. This types of aggregate is generally achieved from magnetite (Fe3Oand Barytes (BaSO4,rock name). Concret having unit weight of about 30 to 37 kN/m3 c be produced by using magnetite, barites and scrap iron. This type of aggregate is used construct radiation shield (Nuclear power plant) and Operation Theater, and also used produce dense and crack free concrete.

The main drawback with this aggregate is that it is difficult to have adequatworkability without segration.

The compressive strength of these concrete is of the order of 20 to 21 MPaThe cement aggregate ratio varies from 1:5 to 1:9 with water cement ratio in between 05 0.65.

(c) Light weight aggregateThe aggregate having unit weight in a range of 1.2gm/cc (12 kN/m3) are

known as light weight aggregates. These aggregates can be either natural such as diatomi pumice, volcanic, cinder etc or manufactured such as bloated (Abnormally distendespecially by fluids or gas) clay, sintered (forged) fly ash or foamed blast furnace slaThey generally used for the manufacture of structural concrete and masonry blocks freduction of the self weight of concrete. They can also be used to provide better therminsulation and to improve fire resistance.



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Bulking of sand (fine aggregate)

The increase in the volume of a given mass of sand (fine aggregate) cause by the presence of water is known as Bulking of sand.

The bulking of sand is caused by the films of water which pushes the particle apart. The extent of bulking depends up on the% of moisture present in the sandand its fineness .

It has been observed that bulking of sand increases gradually with moisturcontent up to certain point and then begins to decrease with further addition of water duemerging of films until when the sand is inundated (covered with water). At this stage t bulking is practically nill. Thus, bulking effect will be maximum when water content sand lies in between 4 to 6% .

Above figure shows variation of % bulking with moisture content. Therealation shows, fine sand bulks considerably more and the maximum bulking is obtainat higher water content than that of coarse sand. In general, bulking may be to an extent30% of original dry volume of sand in the fine sands ( particle size 0.25 mm to 0.15 mmand 15% in the case of coarse sand (particle size around 2mm).

If the sand is measured by volume and no allowance is made for bulking, thmix will be richer than that specified because for given mass moist sand occupieconsiderably larger volume than that of dry sand of same mass. This results in a mdeficient of sand increases the chances of the segration of concrete, then yield of concralso will be reduced. Hence, an increase in bulking from 15 to 30% will result in aincrease of concrete strength by as much as 14%. If no allowance is made for bulking sand, the concrete strength may vary (reduce) by as much as 25%.

Determination of bulking of SandProcedure


Moisture content (%)

Fine snad

Medium sand

Coarse sand

Bulking% ofdryvolume

orchangeinvolume(%)

A B C

sand water Sand+water

V2


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1. Take a clean glass cylinder and fill it about with the sand sample. Note down it

volume, say V1 = 30 cm.2. Now carefully take the sand out and place it on a glass plate. Fill the glass cylindwith water to of its volume.

3. Put the sand sample back in to the glass cylinder very slowly, stirring the watewhile adding sand into it. This is essential to make all the sand grains settle fully ithe cylinder.

4. Note new volume of sand sampl; let it be V2. If V1 = V2 , it will mean sansample has retained its original volume, i.e. it has shown, No bulking. But, V2 changed, let s say V2 =34 cm, then bulking of sand is

= (V2 V1)/V1 * 100= (34 30)/30 * 100

= 13.33%

END OF CHAPTER - 3


V1


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CHAPTER 4 Metals

Ferrous and Non-ferrous Metals

Ferrous metals are such which contains iron whereas non-ferrous metals are such whicontains no iron. Ferrous and non-ferrous metals are mostly used in engineering fie because they confirms to the engineering requirements.

Classification of Ferrous Metals

IRON(A) Pig Iron

When iron ore (i.e. mineral from which metal is extracted) is smelted byusing Blast-furnace, the initial formation which comes from furnace is called Pig Iron. It


Ferrous Metal

Iron Steel

PigIron

CastIron

WroughtIron Plain CarbonSteel

AlloySteel

Low carbonsteel

Mediumcarbon steel

High carbonsteel

Tool Steel

Stainless Steel

Die Steel

Heat Resistive Steel


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an impure form of iron. Pig iron can not be used directly in practice but pig iron is used araw materials for further production of wrought iron and steel.Composition: It contains iron and varying quantities of other elements amongst whichcarbon, silicon, manganese, sulphur and phosphorus are the most important. These mamount to as mush as 10% of the weight and 25% of the volume of pig iron.

Manufacture (Formation) of pig iron

It is manufactured in following stages:(a) Selection of Ore: The natural In nature, iron occurs in combined form as oxide,sulphate, carbonate and silicate etc. from such raw resources iron can be extracteeconomically and are called iron ore. Following are common ores:

Hematite (Fe2O3) or Red Iron Ore Magnetite (Fe3O4) or Black Iron Ore Siderite (FeCO3) or Spastic Iron Ore

(b) Dressing of Ore: The process of reduction in size and removing of impurities to get

within required limit is called dressing of ore. This is achieved by passing the ore throughseries of crushers and washing mills.(c) Calcination, roasting and smelting: It is done through Blast Furnace.

Iron making Blast Furnace

(B) Wrought Iron

Wrought Iron is the oldest form of iron made by man. It was originally produced by slow reduction of the metal from the ore in the forge fire. This reductio process results very impure iron which requires further refining by mechanical working i



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by hammering or shaping to the form in which it is used. Thus, It is the purest form of irwith iron silicate in physical association and it contains very small amount of impurities.

It is very low in carbon and the iron silicate or slag is distributed through the base metal in fibres which gives it a woody or fibrous appearance when fractured. WrougIron is used for some selected engineering applications.

Manufacture of Wrought Iron

It is manufactured from Pig Iron with following two processes:

(i) Puddling Process: It comprises following procedure:A small reverberatory furnace called puddling furnace is to be used which halining of iron oxide bricks.Pig iron is heated with the help of charge to a 1200oC. At this temperature, melted pig iron is oxidized on coming in contact with iron oxide lining.The molten charge is regularly stirred or puddle through puddling hole to ensur

oxidation with iron oxide lining.Carbon is driven off as carbon dioxide and remaining molten charge ,containinsome slag forms the Wrought Iron. It is squeezed to remove any extra slag.

(ii) Aston Process:

Pig iron is refined by heating in a Bessember Converter. All impurities is to bremoved by directing current of air and molten pig iron is cast into mould.A mixture of iron oxide and silica in predetermined proportion is heated separatein a furnace to fusing temperature which forms slag(iron silicate).The refined pig iron is put into the mixing machine and hot slag is poured on to with the help of slag ladle (A spoon-shaped vessel with a long handle; used ttransfer liquids). Slag is at lower temperature than pig iron.The process mixing slag with iron is called shooting and it results formation oiron-slag balls.The iron-slag balls so formed are subjected to pressing machines where extrquantity of slag is squeezed out. The resulting material from pressing machine iWrought Iron.

(C) Cast Iron

Cast Iron is produced from pig iron by a process of melting and casting intshape.

Composition: It contains iron, silicon and carbon. Cast iron contains more than 2% ofcarbon to a maximum of 6.67%. Along with carbon and iron, cast iron also containsulphour (S), silica (Si), Phosphorous (P) and manganese (Mn). In general cast iron is haand brittle. It has high compressive strength.



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Manufacture of Cast Iron

It is manufactured from remelting pig iron in a special furnace called Cupola.A cupola is an essence a small sized blast furnace of height 5m, diameter 1 m ancylindrical in shape. The cylinder has an inner lining of refractory bricks and i

provided with tuyer near bottom for injecting the supply of air blast.The raw materials like pig-iron, steel scrap, fuel and fluxes are added from thcharge door at the top to a previously heated cupola.The air blast is continuously fed through tuyers.All impurities of pig iron get oxidized and form a slag that starts floating at thupper layer.The molten cast iron is removed from the lower draw hole and charged directly intmould of desired shapes. These are calledCast Iron.

Properties of cast iron

No generalization of properties of cast iron is possible because properties of cast irdepends on the followings:1. The composition of cast iron,2. The rate of cooling and3. The nature of heat treatment.

Following are are the properties which depends on composition:

(1) Carbon: When most of carbon is present as graphite(free carbon), cast iron becomesoft & weak (e.g.grey cast iron). But when carbon presents as cementite, the metal is haand strong.

(2) Allowing elements:

(a) Nickle:(i) Nickel cast iron: It contains Nickle in between 0.5 to 3%. Machinability is uniform.(ii) Chilled cast iron: Nickle lies in between 3 to 5%. This has high resistance to abrasion.(iii) High nickel cast iron: Nickle lies up to 20%. It has resistance to corrosion.

(b) Chromium: Addition of chromium increases hardness and tensile strength of cast iron.

(c) Molybdenum: Addition of this increase the hardness of cast iron.

(3) Heat Treatment: This treatment changes the properties of cast iron to a great extent.White cast iron when subjected to Annealing becomes soft, very ductile and easilmachinable.

(4) Impurities: The influence of certain common impurities like phosphorous, sulphur,silicon and manganese is quite pronounced.



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Classification of cast iron:

Cast iron is further classified into followings:1. Grey Cast Iron (GCI.)2. White Cast Iron (WCI.)

3. Malleable Cast Iron (MCI.)4. Sphenoidal Graphite Cast Iron (SGCI.)5. Alloy Cast Iron (ACI.)

(1) Gray Cast Iron: It is basically an alloy of carbon and silicon with iron. It contains:

Carbon (C) : 2.7% Silicon (Si) : 1.1% to 2.8% Sulphour (S) : 0.10% Manganism (Mn) : 0.4% to 1.0% Phosphorus (P) : 0.15% Iron (Fe) : Rest

Properties:It is hard and brittle in nature.It has better compressive strength.It has better machinability and castability and weldability.

Uses:Grey cast iron are generally used for manufacturing of machine tool beds, piston rings etc(2) Alloy Cast Iron: When some amount of Nickel(Ni), Chromium(Cr), Molybdenum(Md)etc. are added to the composition of cast iron, the resulting iron which produce is callAlloy Cast Iron. Comparatively it has better properties and strength than other cast ironshas following properties.

It has high strength and hardness.It has better castability.It can be machined and forged easily.It possesses resistance to wear and heat.It has better corrosion resistance.

Uses:Alloy cast irons are generally used for making cylinder, I.C. Engine, Piston rings, pipes e

STEEL

Steel is an alloy of iron (Fe) and Carbon (C). It is produced from pig iron with the help Bessemer converter. The best thing about steel is that it has very high compressive strengof cast iron and very high tensile strength of wrought iron. As such it is suited for all typof situation as a structural materials.Composition: Steel contains maximum up to 2% of carbon (about 1.7%) theoretically. It itough, strong and ductile.

Manufacture of Steel



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The Bessember Process

Bessemer Converter (Isometric Figure)

Bessemer Converter The Bessemer Converter is an egg or pear shaped vessel supported on trunions in suchway that it can be tilted and even rotated about its horizontal axis. The inner walls of thconverter are lined with a refractory material.

Stages

(1) The Bessemer converter is first tilted to a horizontal position. Molten pig iron (ramaterial) is then fed directly from the furnace . Air is also simultaneously blown into tconverter through the tuyers and the converter is straightened up.(2) Air is kept blowing continuously through the charge. During this process, most of thimpurities of the pig iron like Si, C, Mn, S & P gets oxidized on reacting with iron oxidformed as a result of reaction of iron and air. Chemical representation of this change is follow:


Flame

Iron


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2FeO + Si = 2Fe + SiO2FeO + Mn = Fe + MnO

(3) When oxidation process has progressed sufficiently, predetermined quantities oferromanganese are added for two purposes:

It supplies carbon for the steel and

It deoxidizes any iron oxide left during oxidation of other impurities.(4)Converter is then tilted into the discharge position and molten metal poured into moulof special rectangular shapes. The solidified steel is known as INGOT, which is the initmaterial for preparing other steel shapes.

Some other processes are also available for the manufacture of steel which aras follows:

1. Open Hearth Process2. The Electric Process3. Linz-Donawitz Process Have a self study for Knowledge (Refer Book).4. Duplex Process etc.

Properties and Uses of Steel

(1) Plain Carbon Steel It contains Carbon and iron only in its structure. It contains no alloying

elements (such as Si, P, S Mn, etc.). It has three types:

(a) Low Carbon Steel or Mild Steel):It contains :

Carbon (C) : Up to 0.35% Iron (Fe) : Rest

Properties: It is tough and ductile in nature. It has better machinability and weldability. It can be forged easily into required form. It has better tensile strength.

Uses:It is generally used in R.C.C., Locomotives(A wheeled vehicle consisting of

self-propelled engine that is used to draw trains along railway tracks), Sheet metalFabricated items, Machine components etc.

(b) Medium Carbon Steel:

It contains: Carbon (C) : 0.35% to 0.5% Iron (Fe) : Rest

Properties: It is stronger than mild steel (M.S.) It has better hardness as compared to mild steel. It is tough and less ductile.



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It can be machined and firged into required shapes.Uses:It is generally used for making Rails, Automobile components etc.

(c) High Carbon Steel:

It contains: Carbon (C) : 0.5% to 1.65% Iron (Fe) : Rest

Properties: It is hard and strong. It is less tough as compared to mild steel. It has better forgeability and castability. It has better resistance to wear and heat.

Uses:It is generally used for making structural members, Automobile components

Spring, hacksaw blade, carpentors hand tool, light duty dies etc.

(2) Alloy Steel When alloying elements like Silicon (Si), Chromium (Cr), Molybdenum (Mo

Vanedium (V), Cadmium (Cd), Covalt (Co) etc. are added in small quantities into thcomposition of plain carbon steel, the resulting steel is called Alloy Steels. Alloy ste possesses superior properties & strength as compared to plain carbon steel.

Alloy steel containing less than 10% of alloying elements are called low alloysteel, where as high alloy steel contains more than 10% of alloying elements. Alloy steare of following types:

(a) Tool Steel

Steels which are used for tool making are called Tool Steel. Modern technologaccepts High Speed Steel (HSS) as a better tool steel, thus HSS can be better used for mecutting. A typical composition of HSS is as given below:

Carbon (C) : 0.65% to 0.75% Tungsten (W) : 18% Chromium (Cr) : 4% 18/4/1 HSS Vanadium (V) : 1% Iron (Fe) : Rest

Properties: It is sufficiently strong, hard and tough. It has better corrosion resistance. It has better red hardness. It can be forged and machined into the required tool form easily. Its cost should be reasonable. It has better wear resistance.



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(b) Stainless Steel:It is a rustless or corrosion resistance steel which contains chromium (Cr) an

Nickle (Ni) as a allowing elements. A typical stainless steel which is generally used practice will have following composition:

Carbon (C) : 0.3% to 0.4% Chromium (Cr) : 18% 18/8 Stainless Steel Nickle (Ni) : 8% Iron (Fe) : Rest

Properties: It is strong, hard and tough. It has excellent corrosion resistance. It has better formability and machinability. It has better resistance to heat, ware and abrasion. Cost should be reasonable.

Uses: In Nuclear power plants. In Processive Industries (i.e. Farmatutical production) In food Industries. For making surgical equipments. For making Injection Needle. For making domestic utensils etc.

(c) Spring Steel:Steels are which are useful for spring manufacturing process are called Sprin

Steel. A typical composition of a spring steel contains the following: Carbon (C) : 0.5% Silicon (Si) : 2% Sillco-Manganese Steel Manganese (Mn) : 0.7% Iron (Fe) : Rest

Properties: It is strong and tough. It has high Resilience (An occurrence of rebounding or springing back). It has corrosion resistance. It cab be easily made into spring form. Its cost is higher as compared to other steel which can be used for spring steel.

Uses:For the manufacture of all types of springs.

(d) Heat Resistive Steel (HRS):



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This alloy steels are used in places where steel objects are subjected totemperature. It contains high carbon % along with C, Cr, Ni, W and Co.

It should have following Properties: It should have high creep resistance. It should be hard and strong. It should have low coefficient of expansion. It should have corrosion resistance. It should have better formability and castability. It should be stable at high temperature.

(e) Die Steel Steel which are used for die making purpose are called Die steel. Die stee

should have the following properties: It should be sufficiently hard, strong and tough. It should be of better heat resistance capacity. It should have corrosion resistance. It should have dimensional stability during operation. It should be friendly to some machining process and manufacturing process.

ALUMINIUM

Aluminium is a very common component of the earth crust (about 8%). The most commore of aluminium isBauxite(Al2O3.nH2O).

Manufacture of Aluminium

The ore (Bauxite) is first purified from all of its usual impurities such as silicatitania, iron and pure oxide of Aluminium (Al2O3) by treating with sodiumhydroxide solution. By this way Alumina can be obtained.

From the alumina so obtained above, metallic alumina is prepared by the process electrolysis. To get 100% purity, further electrolysis should be done.

The following figure shows the process of Electrolysis to get pure Aluminium.



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Properties of Aluminium: It is white metal and shows brilliant luster when fresh. It is lightest material and have sp.gr. of 2.7 It has low melting point of about 650oC. It has high electrical and thermal conductivities. It has tensile strength of about 900 kg/cm2 in the annealed condition.

It has high ductility and so can be transformed into any shape by rolling, stampinextruding, forming, drawing and spinning. It has good castability, so it can be cast in any shape by any method. It has highly resistance to corrosion. It forms excellent alloy with a number of metals such as cu, Mg, Si, Zn, Mn, Cr an

Ni.

Uses: For structural purpose i.e. frame, railing & roofing material. For making Door, window frame, gates, water reservoir & ventilations. For making super Duralumin in aircraft industry. For fabrication of railway wagons & other body product. For the fabrication of automobiles bodies. For making economical conducting materials in electrical industries. For making aluminum tanks, condensers, heat exchanger, containers etc. i

chemical and food processing industry. For making cooking utensils.



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It has considerable resistance to nuclear radiation, so it is used in Nuclear EnergProjects.

Alloys of Aluminium

Aluminium Alloys are classified as:

DURALLUMINIUM

It is an aluminium alloy which is commonly used in Aero Parts, Automobiles, In Riveetc.It contains:

Aluminium (AL) : 95%

Copper (Cu) : 4.5% Magnesium (Mg) : 0.5%

Properties: It is tough and ductile and durable. It has excellent corrosion resistance. It has excellent machinability. It has low specific gravity. It is a good conductor of heat and electricity.

END OF CHAPTER 4


Aluminium Alloy

Wrought Alloy Cast Alloy

With Copper (Durallumin)

With Mg With Mg + Si HeatTreatable

Non-heattreatable


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CHAPTER 5Types of steel, and its composition

For article 5.1 to 5.5, Refer note of Chapter 1, 2 and 4.5.6 Deformation of steel/Metal

Deformation is defined as the change in dimensions or forms of the solid matteunder the action of applied force. Deformation is caused either by mechanical action external force or by some physical process. Deformation is longitudinal when it producthe change in length and it is angular when it changes the angle between the various facof the bodies. This deformation of steel/metal is necessary to form various metallic shawithout fracture.

Deformation may be of following two types:

1. Elastic Deformation2. Plastic Deformation

(1) Elastic DeformationIt is defined as the deformation of a body which completely disappear when

external load is removed from the body. Therefore elastic deformation is a temporadeformation. Under the application of tensile load brittle materials shows Elastideformation up to its fracture point, while ductile materials show the elastic deformatiup to a point called as Elastic Limit.

Elastic Deformation is of following two types:(a) An-elastic Deformation

(b) Elastomeric Deformation(a) An-elastic Deformation

It is defined as the deformation which is fully recoverable but time dependenIn this case, stress is proportional to strain which obeys Hookes Law but the strainingtime dependent.

(b) Elastomeric DeformationThis deformation do not obeys Hookes Law. In this case stress is not directly

proportional to strain within elastic limit. This type of deformation is possible only in nocrystalline materials like polymers. For example, Polymers like Synthetic Rubber, which

also called elastomer undergoes to this type of deformation, thus the deformation is namas Elastomeric Deformation.

Elastic After Effect (or Delayed Elasticity) (VVI)

The asymptotic approach of elastic strain to its equilibrium value with the passes of time after the application of load is called Elastic After Effect.



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Consider a metal which is subjected to a constant stress at a level very much below its elastic limit.

Let, at a time 1sec, if constant stress is suddenly increased to that metal then iundergoes same instantaneous elongation (e1) followed by a delayed elastic strain (eduring the time t second.

At the time t sec. when the load is suddenly removed the instantaneousstrain e1 decreased in the same amount as it was increased during loading. The delayestrain (e2) again follows at a decreasing rate until the total strain is zero.

(2) Plastic DeformationIt is defined as the deformation of a body which remains even after the remova

of the applied load from the body. Elastic deformation always followed by a considerabamount of plastic deformation. For materials above 0.4Tm, if loadd then plastideformation takes place.

Plastic Deformation mainly takes place by following two mechanism (mode o plastic deformation)

(A) By SlipIt is defined as shear deformation where atoms move over a number of

interatomic distances relative to their initial positions.

Before shear load After shear load

The above figure represents slip process in a perfect crystal under theapplication of shear load. As a result of shear load application, plastic deformation tak


e2 e1

e1

An-elasticity

1sec. t sec.Time (sec)

strainLoaded

Unloaded

e2

Slip Plane

Slip Block


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place and the crystal is divided into layers or slip blocks. The plane at which slipping atomic layers takes place is called slip plane and the preferable direction is called sldirection.

(B) By Twinning

It is an important mechanism by which metals are deformed. In twinning eacatoms moves by only a fraction of interatomic distances relative to its neighbors. Thorientation of twinned region is different from untwined region. The plane at whictwinning occurs is known as twinned plane and the preferable direction is called twinndirection. It is already understood that a metal usually deforms by twinning only if it unable to slip. Twins produced by mechanical deformation are called mechanical twins athe twins produced by annealing are called anneal twins.

Comparisons

(A) Comparison between Slip and Twinning

Slip SN TwinningOrientation of the crystal above & belowthe slip plane is same.

Slip occurs on relatively wide plane.

Slip takes time to form.

Slip occurs due to the application of

shear stress.It is a phenomenon at high temperaturewith lower strain.

1.0

2.0

3.0

4.0

5.0

It results in an orientation differenceacross the twinned plane.

Every atomic plane is involved in thedeformation by twinning.

It takes very less time to form.

It is not known.

It is a phenomenon at lower temperaturewith high strain.

(B) Comparison between Elastic and Plastic Deformation

Elastic Deformation SN Plastic DeformationIt is temporary deformation whichappears and disappears with applicationand removal of streses.It is the beginning of progress of deformation.

It takes place over the short range of stress-strain curve.

In this deformation, strain reaches itsmaximum value after the stress has

1.0

2.0

3.0

4.0

It is permanent deformation which existeven after the removal of stresses.

It takes place after the elastic deformationhas stopped.

It takes place over a wide range of stress-strain curve.

In this deformation, strain occurssimultaneously with the application of



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reached its maximum value. stress.

Critical Resolved Shear Stress (f cr)

Stress required to initiate slip in a pure and perfect crystal is called criticaResolved Shear Stress (f cr )

Consider a crystal is subjected to an axial load as shown in above figure:Let, P : Load applied in a axial direction.

A : Cross-section area of the crystal. : Angle made between slip direction and tensile axis. ( 90o) : Angle made between the normal to the slip plane and the tensile axis.

As a result of axial load application, slip takes place along the slip planeTherefore,

Area of slip plane = A / Cos

Thus, the component of the applied load acting in the slip direction = P*CosWe know,Stress at slip plane = Critical Resolved shear stress

= f cr Therefore, f cr = P*Cos / (A / Cos)

= (P / A) Cos * Cos

Thus, f cr = (f t) * Cos * Cos --------------------- (1)Where,


Normal to slip plane

Slip plane

P

P

Slip Direction


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Ft = Direct tensile stress.Equation (1) is also known as Schamids Law.

5.7 Heat treatment of steel & its thermal properties

Heat treatment is defined as the process of heating the steel from roomtemperature to operating temperature, held at that temperature for predetermined timfollowed by cooling to reach room temperature.

The main aim of heat treatment is to alter or change the mechanical propertieof metal as desired.

Objectives of Heat Treatment (General Purpose or Importance of H.T.)

To soften the steel, thus to improve its ductility and machinability. To refine the grains. To eliminate the internal stresses from the objects.

To remove the gases from the cast objects. To increase the hardness of steel. To increase ware, heat and abrasion resistance of steel. To improve the toughness of the steel. To increase the surface hardness. To produce a hard case over a ductile interior. To restore electric and magnetic properties.

General Procedure of Heat Treatment

The general procedure of heat treatment is best explain in steps as given belowwith the help of a Heat Treatment cycle.

Y

O.T. HoTemperature (2)

(oC)H (1) (3) C

XR.T. Time (sec)

R.T. : Room TemperatureO.T. : Operating Temperature(1) : Heating H(2) : Holding or Soaking, Ho



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(3) : Cooling C

Step-1, Heating:Steel are heated from Room Temperature to Operating Temperature. O.T.varies for process of heat treatment.Step-2 Holding or Soaking:Hold the steel at that O.T. for predetermined time or proper

time in order to achieve uniform temperature throughout the object.Step-3, Cooling:Now cool the steel from O.T. to R.T. by using suitable cooling rates.Cooling rate varies for process to process of heat treatment.

Note:Cooling rate Cooling MediumSlow Air cooling and Furnace coolingMedium Oil and by lead bathFast (Quenching) By H2O and By Brine (Nacl) Solution

Heat Treatment Processes

The following Heat Treatment processes are generally carried put inindustries to achieve the purposes:

1. Annealing2. Normalising3. Hardening4. Tempering5. Surface Hardening6. Case Hardening

Fe-C Equilibrium Diagram

(For Steel region only)Y

1130

a3 acm 910

Tempr (oC) + + Fe3C

L.C.T. Line723

a1 + P P + Fe3C

R.T. 0.8 2.0 XHypo Hyper

Steel Region



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% of C in Fe

In above figure;, , P are the phases of steel at different temperature.

: Ferrite

: Austenite P : Pearlite Fe3C : Cementite. a1 : Line corresponding to LCT. a3 : Boundry line between iron and ( + ) iron. acm : Cementite Precipatation line

Lower Critical Temperature (L.C.T.):When steels are heated below this temperature, no change takes place in their micrstructure. But when heating takes place above LCT, then critical changes in microstructutakes place for steel. 723oC (i.e. a1 line) correspondence to LCT.Upper Critical Temperature (U.C.T.):The temperature at which rise in temperature of steel during heating from roomtemperature is over, is known as UCT.Critical Range:The region between the UCT and LCT for a given steel is known as Critical Range. Criticrange can be referred when the steels are heated above the a1 line, around a3 and acm line.

(1) Annealing: It is a softening process where steels are heated above the critical rangefollowed by very slow cooling. The main aim of this process is to soften the steel teliminate internal stresses and gases from the objects.

(2)Normalizing: It is a type of Heat Treatment where steels are heated above thetransformation range followed by still air cooling to reach room temperature. The main aof this process is to refine the grains of steel.

(3) Hardening: It is a type of Heat Treatment where steels are heated above thetransformation range followed by fast cooling to reach room temperature. The main aimthis process is to increase the hardness of steel.

(4) Tempering: It is a type of Heat Treatment where hardened steels are reheated belowlower critical temperature followed by medium cooling to reach room temperature. Tmain aim of this process is to increase toughness of steel.

(5) Surface Hardening: It is a type of Heat Treatment process which is very much usefulwhenever a depth surface to be hardened is more than 1mm. The main aim of this proceis to produce a hard and wear resistive surface on ductile interior.

(6) Case Hardening: Whenever it is required to go for hardening the depth of surface lessthan 1mm, then case hardening is to be conducted. The main aim of this process is produce a hard and wear resistive case over a ductile core.



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5.8 Fracture modes of materialsFracture refers to breaking of the components into two or more pieces either durin

service or during fabrication due to the application of external load. Factors which aresponsible for fractures are:

Rate of impact Temperature and Geometry of the materials.

Several terms are used to describe fracture depending up on the behaviour of thmetal under stress. The most important modes of fractures are followings:

1. Ductile Fracture2. Brittle Fracture and3. Creep Fracture.

(1) Ductile Fracture: It may be defined as the fracture which takes place by a slow

propagation of crack with considerable plastic deformation. Energy consume for thfracture is very high. The appearance of fracture surface is rough and dull. In this cafailure is mainly on the account of shear stress. In this fracture the crack continue t propagate so long as the material is in strain. If the straining is stopped then a cracdevelopment is also stopped. In actual practice ductile fracture is not much significant.

(2) Brittle Fracture: It occurs when the material breaks into pieces without anyconsiderable plastic deformation. So, brittle fracture may be defined as a fracture whitakes place by the rapid propagation of crack with a negligible deformation. If the brok pieces of this fracture materials are fitted together then the original shape and dimensioare obtained. If brittle fracture takes place along the grain boundry then it is known

Intergrannular Farcture, if it takes place at high temperature then the fracture is callIntragrannular Fracture.

(3) Creep Fracture: It may be defined as the fracture which takes place due to theexcessive creping of materials under steady loading. In this case tendency of fractuincreases as the temperature increases.

Comparision between Ductile and Brittle Fracture.Ductile Fracture SN Brittle FractureThis fracture takes place after considerable plastic deformation.

Fracture rate is very slow.

Failure is on the account of shear stress.

Energy consumed is very high.Fracture surface looks rough and dull.

1.0

2.0

3.0

4.05.0

In this deformation, no considerable plastic deformation takes place. It

happens just after elastic region.Fracture rate is very quick.

Failure is on the account of direct stress.

Energy consumed is very lowFracture surface looks smooth and



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regular.5.9 Steel corrosion & its treatment

It is understood that in nature, metals are available in the form of their oxidescarbides, sulphides, silicates etc, when those things are processed then the correspondi

pure metal is produced. When the very same pure metal is exposed in atmosphere thengets oxidized or corroded. Therefore, corrosion is sometimes known as Reversible proceon producing metal ore.

Thus, Corrosion is defined as the distortion of metal in nature either having contawith oxygen directly or having the contact with oxygen indirectly. More or less all metagets corroded in nature.

Classification of Corrosion

Corrosion is broadly classified into the following two groups:1. Dry Corrosion (Direct-chemical Corrosion)

2. Wet Corrosion (Electro-chemical Corrosion)(1) Dry Corrosion (Direct-chemical Corrosion):

In this case corrosion is mainly due to direct attack of oxygen in nature. In this cametal will not have a contact with electrolytes but corrosion takes place.

Mechanism of Dry Corrosion

Atmosphere

Oxide film

Metal Piece

Whenever metals are exposed to atmosphere they came to contact with atmospherdry elements. As it is already understood that dry corrosion is mainly due to dry attack oxygen, therefore oxygen directly penetrate into the upper surfaces of the metal and oxidiit. As a result, oxide layer is formed at the upper surface.

As the process is continuous one, similarly the other layers of metal gets oxidizewith some time period and finally destroy the metal.



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Note:*At high temperature dry corrosion phenomenon is higher.** the oxide film thickness on the metal goes on increases then the corrosion rat

gradually decreases.

(2) Wet Corrosion (Electro-chemical Corrosion):

MetalPiece.

Electrolytes

When metal will have a contact with electrolyte, wet corrosion takes place. It imainly due to the indirect attack of oxygen. This corrosion takes place due to the flow electrons or ions. Thus wet corrosion is also known as Electro-chemical corrosion.

Mechanism of Wet Corrosion

Mechanism of Wet Corrosion takes place by following two methods:

(a) Hydrogen Evolution Method: Whenever the metal will have a contact with electrolytesuch as industrial wastage & acid solutions then, wet corrosion takes place. This corrosimechanism takes place by indirect attack of oxygen. In this case

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