Strength of Material 

Civil Engineering

Hooke’s Law

• It states that the strain in a solid body is directly proportional to the applied stress and this condition is valid upto the limit of proportionality 

Limit of proportionality 

• it is the stress at which the stress-strain curve ceases to be a straight line. It is the stress at which extension ceases to be proportional to strain. The proportional limit is important because all subsequent theory involving the behavior of elastic bodies is based on the stress-strain proportionality.

Elastic limit 

• it is that point in the stress-strain curve up to which the material remains elastic, i.e. the material regains its shape after the removal of the load.
• However, for many materials, elastic limit and proportional limit are almost numerically the same and the terms are sometimes used synonymously. In case where the elastic limit and proportional limit are different, the elastic limit is always greater than the proportional limit.

For a biaxial state of stress, normal strain along the horizontal X-axis is given by,

εxx=σxE−μσyE

Where, εxx${\epsilon }_{\mathrm{x}\mathrm{x}}$ is the normal strain along the horizontal X-axis; σxandσy${\sigma }_{\mathrm{x}}\mathrm{a}\mathrm{n}\mathrm{d}{\sigma }_{\mathrm{y}}$ are the normal stress in the direction of the horizontal X-axis and vertical Y-axis respectively; E is the modulus of elasticity of the material and μ is Poisson’s ratio.

stress strain diagram for various types of material

Young's modulus (E)

• Young's modulus is a measure of the ability of a material to withstand changes in length when under lengthwise tension or compression.
• Young's modulus is equal to the longitudinal stress divided by the strain within the elastic limit.

Poisson’s ratio (μμ)

• Poisson's ratio is the ratio of lateral strain to longitudinal strain in the direction of stretching force within the elastic limit. 

Bulk modulus (K)

• It is defined as the ratio of the developed stress in the body to the resulting relative decrease of the volume.

Rigidity modulus (G)

• Shear modulus or modulus of rigidity or rigidity modulus is defined as the ratio of shear stress to the shear strain.

When the temperature of a material changes there will be a corresponding change in dimension.

• When a member is free to expand or contract at one of the ends, due to the rise or fall of the temperature, no stress will be induced in the member.
• But, if the material is constrained (i.e. body is not allowed to expand or contract freely), change in length due to rise or fall of temperature is prevented, and stresses are developed in the body which is known as thermal stress.

Stresses in Constrained material:

• When the temperature of the bar is raised, and the bar is not free to expand, the bar tries to expand and exerts axial pressure on the wall. At the same time wall puts equal and opposite pressure on the bar which will develop compressive stress in the bar.
• If there is a drop in the temperature of the bar, the bar will try to contract, exerting a pull on the wall. At the same time, the wall offers equal and opposite reactions exerting a pull on the bar which will develop tensile stress in the bar.
• Increase in temperature → Compressive stress
• Decrease in temperature → Tensile stress

Modulus of resilience

It is defined as proof resilience per unit volume. It is the area under stress-strain curve up to the elastic limit.

Proof resilience

 It is defined as the maximum energy that can be absorbed within the elastic limit, without creating a permanent distortion.

Modulus of toughness 

It is ability of unit volume of material to absorb energy up to fracture. From the stress – strain diagram, the area under the complete curve gives the measure of modules of toughness.

Assumptions in the theory of bending:

• 1. The radius of curvature is very large compared with the dimensions of the cross-section.
• 2. The beam is made of homogeneous and isometric material and the beam has a longitudinal plane of symmetry.
• 3. The resultant of the applied loads lies in the plane of symmetry.
• 4. The geometry of the overall member is such that bending not buckling is the primary cause of failure.
• 5. Elastic limit is nowhere exceeded and ‘E' is the same in tension and compression.
• 6. The transverse sections which were plane before bending, remain plane after bending. 
• 7. The beam is initially straight and has a constant cross-section.

Slenderness ratio

•  (λ) = Leff/r
• Where,
• Leff = Effective length for the column, and r = minimum radius of gyration.
• Various column conditions and effective length are tabulated below.

.

Condition (distance between supports is ℓ)	Effective length
Both ends Hinged (pinned)	L
One end hinged, another fixed	L/√2
Both ends fixed	L/2
One end fixed and other end is free	2L

Struts:

• These are long and slender structural members in an assembly that are subjected only to an axial compressive force.
• They predominantly fail by buckling but sometimes the yielding failure occurs in compression before buckling.
• These members are structurally analogous to columns. So, the buckling strength of struts is similar to that of the colum

Shear Stresses:

Due to the shear forces the beam will be subjected to shear stresses. These shear stresses will be acting across transverse sections of the beam. These transverse shear stresses will produce complimentary horizontal shear stresses, which will be acting on longitudinal layers of the beam.

τx=VAY¯Ibx

Where,

V = Shear force (Due to change in bending moment)

A = Area above or below the section in the cross-section

Y̅ = Distance from centroid of area from neutral axis

I = Moment of inertia of total cross-section about neutral axis

bx = Width at the section

Nominal or average shear stress (τavg):

τavg=ShearforceCross−sectionarea

The relation between maximum shear stress (τmax) and average shear stress (τavg) for different shapes is given in the below table

Section	τmax/τavg	ΤN.A/τavg
Rectangular or square	3/2	3/2
Circular	4/3	4/3
Triangle	3/2	4/3
Diamond	9/8	1

---

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Paint - Building Material Civil Engineering - Quick Revision

Paint 

Building Material Civil Engineering

Quick Revision of Paints Civil Engineering

Paints:

• It is the mechanical dispersion of one or more fine pigments in a medium (thinner + vehicle). When the paint is applied to a metal surface, the thinner evaporates, while the vehicle undergoes slow oxidation leading to the formation of a pigmented film.

Quick Revision of Paints Civil Engineering

Constituents of paint:

1. Pigment: 

• It is an essential constituent of paint. It provides color and opacity, in addition to that imparting strength and aesthetic appeal to the paint.
• Pigments provide colour to the paint

E.g- 

• White lead, Red lead, Zinc oxide, Iron oxide, etc
• Black – Lampblack, charcoal black
• Brown – Burnt umber, burnt sienna
• Blue – Persian blue, ultramarine
• Green – Chrome green, copper sulphate
• Red – Red lead, venetian red
• Yellow – Zinc chrome, raw sienna chrome yellow.

2. Vehicle or drying oils: 

• It is a liquid that binds the pigment to the surface and protects pigment from decay e.g. linseed oil, dehydrated castor oil, etc.

E.g-

•  Linseed oil, Tung oil, Poppy oil, Nut oil,etc

3. Extenders or fillers: 

• The function of addition of filler in paint is that it improves the properties of the paint and mainly to reduce the cost. The main purpose is to increase pigment volume concentration.
• Magnesia, alumina, gypsum, silicate, barite are the commonly used fillers

E.g- 

• Gypsum, Calcium carbonate, Aluminium silicate, Magnesium silicate, Talc, Diatomite, etc

4. Thinners or solvents: 

• It is a volatile solvent, which is often added to paint which helps to adjust the consistency of the paint.
• Solvents of oil paints are used to thin the paints and increase the spread.

E.g- 

• Turpentine, White spirit, Naptha, Benzine, Petroleum, etc

5. Drier: 

• The main function of a drier is to increase the drying power of the vehicle. They act as oxygen-carrying catalysts.

E.g-

•  Litharge, Red lead, Sulphate of manganese, etc

6. Plasticizer: 

• They remain permanently in paints and varnishes. They improve the elasticity of the paint film which prevents cracking of the film.

7. Anti-skinning agents: 

• These are chemicals added to paints to prevent gelling and skinning of the film is called plasticizers.

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Types of paints are

• 1. Oil paint: These paints contain white lead as base.

• 2. Enamel paint: This paint is prepared by adding white lead or zinc to varnish. It is desirable to provide titanium under coat. It may be used for exterior walls also.

• 3. Emulsion paint: It contains binding material like polyvinyl acetate and polystyrene. Cobalt and manganese are the pigments and driers. The paint becomes surface dry within 15 minutes and hardens in 2 hours. The surface is washable.

• 4. Cement paint: It consists of white or coloured cement as base. It is available in the form of powder, which is mixed with water and used.

• 5. Aluminium paint: It consists of finely ground aluminium particles in suspension, in spirit or oil varnish. It is visible in darkness.

• 6. Bituminous paint: It is manufactured by dissolving asphalt of vegetable bitumen in oil orpetroleum. It is black in colour. It is used for painting portions of wooden posts buried underground.

• 7. Synthetic rubber paint: It is prepared by dissolving chlorinated rubber in a solvent. It may be applied to concrete surfaces also.

• 8. Celluloid paint: It is prepared by dissolving celluloid sheets or nitro cotton in petroleum. Castor oil is added to improve adhesive property. It is used for painting vehicles.

• 9. Asbestos paint: It consists of fibrous asbestos. It is used for stopping leakages in metal roof,basements. It is used for painting gutters.

• 10. Plastic paint: It consists of plastic as a base and water as a thinner. It gives attractive colours. This is widely used for painting walls in auditoriums and show rooms.

• 11. Anticorrosive paint: It consists of linseed oil as vehicle and lead or zinc chrome as base. Finely ground sand is added as filler. It is black in colour and gives protection from corrosion.

Quick Revision of Paints Civil Engineering

Distemper

• A distemper is composed of base, carrier, colouring pigments and size.
• Water is used as a carrier.
• Whiting or chalk is used as a base.

Note:

• White lead is a base for paint
• Linseed oil is a carrier for paint
• Poppy oil is also a carrier for paint

Quick Revision of Paints Civil Engineering

Varnish: 

• Varnish is nearly homogenous solution of resins in oil, alcohol or turpentine. Type of solvent used depends upon the type of resin used.

Quick Revision of Paints Civil Engineering

French Polish: 

• It is a type of spirit varnish prepared by dissolving resin in Methylate spirit at room temperature for use on hardwood substance to hide the grain defects. The surface is made smooth by rubbing.

Wax Polish: 

• It consists of bees wax dissolved in turpentine and is used for highlighting the grain over wooden surfaces. The polish is rubbed over the surface with rag until a bright appearance is obtained.

Quick Revision of Paints Civil Engineering

Varnishes are classified as follows-

1.Oil Varnish – 

• uses linseed oil and takes 24 hours to dry. It is suitable both for interior and external works.

2. Spar Varnish –

•  Derives its name from its use on spars and other parts of ships. It gives sticky effect in warm weather and is not used indoors.

3. Flat Varnish – 

• Materials such as wax, metallic soap or finally divided silica when added to varnish produce a dull appearance on drying known as flat varnish.

4. Spirit varnish – 

• it is resin dissolved in spirit. The examples are French polish, lacquer and shellac varnish. It dries very quickly.

5. Asphalt varnish–

• it is made by dissolving melted had asphalt in linseed oil with a thinner such as turpentine or petroleum spirit. It is used over shop fabricated steel works.

Bonus note

• Ultimate Bearing Capacity is given by
• qu = CNc + q’ Nq + 0.5 Bγ’Nγ
• C = 0 (As cohesionless soil)
• ∴ q’ = γ’D

Quick Revision of Paints Civil Engineering

Enamel Paint

• In Enamel paints varnish is used as vehicle where as in the common oil paints Linseed oil is used as vehicle.

• Enamel paint means any solvent-based paint that dries to a hard, vitreous (glass-like) shell. Solvent-based paints are also called oil-based paints, in contrast with water-based paints.

Quick Revision of Paints Civil Engineering

Carrier:

• It is an oily liquid in which the base and pigment are soluble. It facilitates the paint to be conveniently spread evenly over the surface by means of a brush. It acts as a binder for the base and cause it to stick to the surface.

• Oils most commonly used as vehicles are: Linseed oil, Poppy oil. Nut oil and Tung oil.

Quick Revision of Paints Civil Engineering

Driers:

• These are metallic compounds which when added to the paint in small quantities accelerate the process of drying of the paint. Driers have a tendency to affect the colour of the paint and also to destroy the elasticity of the paint.

• Litharge, manganese dioxide, lead acetate and cobalt are the usual driers, out of which litharge is most commonly used.

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Plastics, Glasses and miscellaneous Building Materials - Civil Engineering

Plastics and Glass

Building Material Civil Engineering

Properties of Plastics:

Sound Absorption: 

By infusing fiberglass with phenolic resins, acoustic board are prepared, as they have a high absorption coefficient.

Chemical Resistance:

Plastic offer great resistance to chemical and corrosion.

Fire Resistance:

 Phenol formaldehyde and urea formaldehyde resists fire and hence are used as fire-fighting materials.

Electrical Insulation: 

Plastic are good insulator of electricity.

1. Glass

• It is manufactured by fusion of silica with varying proportions of oxides of sodium, calcium, potassium and magnesia. 
• They are fabricated by blowing, drawing, pressing, rolling or casting.
•  After annealing they are given treatment by tempering, opaque making, silvering,bonding or cutting. 
• It can be made stronger than steel and lighter than cork.

Types of glass are many:

• (1) Common glass;

•  (2) Soda lime glass;

•  (3) Potash lime glass;

•  (4) Potash lead glass;

•  (5) Coloured glass;

•  (6) Special glasses.

Special glasses are fibre glass, wired glass, safety glass, bullet proof glass, shielding glass,ultraviolet ray glass, structured glass, glass blocks, ribbed glass, perforated glass and glass wool, etc.

2. Plastics 

Plastic is a natural synthetic material, which has a property of being plastic at some stage of its manufacture. Synthetic material nay be phenol, formaldehyde, cellulose vinyl, etc. At presentthere are more than 1000 varieties of plastic.

• Synthetic of plastics are polymers. Polymerization is the process in which relatively small molecules, called monomers combine chemically to produce a very large network molecules,called polymers.

• Classification of the plastics may be on various basis.

1. On the basis of structure: Homogeneous plastics and heterogeneous plastics.

2. On the basis of physical and mechanical properties. Rigid plastics, semi-rigid plastics, soft plastics and elastomers.

3. On the basis of thermal properties: Thermoplastics and thermosetting plastic. Thermoplastics soften on heating and harden on cooling. The process of softening and hardening can be repeated several times. Thermosetting plastic undergo chemical changes at 127 – 177° C and set into permanent shape under pressure. Reheating will not soften them.

Advantages of plastic are — they can be moulded easily, do not rust, resist chemical action, light in weight and possess high strength to weight ratio. Disadvantage is that they have low modulus of elasticity.

3. Glass fibre reinforced plastics (GFRP) v

In these glass fibres provide stiffness and strength while resin provides a matrix to transfer load to fibres. GFRP is used for door and window frames, partition walls, roofing sheets, skylights, water tanks, for making chairs and tables.

4. Asbestos v

Asbestos is a naturally available mineral substance. It is fire-proof, acid-proof. It is good insulator of heat and electricity. It is used with cement to produce asbestos cement sheets for roofing, wall panelling, to cover fuse and electric boxes, for making downtake pipes, etc.

5. Bitumen, asphalt and tar v

These are called bituminous materials and their main constituent is hydrocarbon.

• (a) Bitumen: It is obtained by fractional distillation of crude petroleum. It is specified by term penetration, say 80/100 means penetration of standard needle is 80 to 100 mm at a temperature of 25°C. It is used for damp proof course, roofing felt.

• (b) Asphalt: It is bitumen mixed with inert material like sand, gravel and crushed stone. It is found in natural form. It is artificially manufactured also. It is used for waterproofing floors and roofs, lining reservoirs and swimming pools, for grouting expansion joints.
• (c) Tar: It is obtained by destructive distillation of coal, wood or mineral tar. It is used for road work, anti-termite treatment and waterproofing.

6. Fly Ash v

It is a by-product in coal based thermal plants. Its particles can fly in ordinary air. At one time it was considered a nuisance but now it is used as a useful material in manufacturing bricks, for stabilizing soil and to improve workability of concrete.

7. Steel Putty v

It is a plaster filler which can be applied with knife to fill dents in steel plates. It hasgood adhesive property and dries hard.

8. Adhesive, sealants and joint fillersv

• An adhesive is a material used to join two or more surfaces. Asphalt, shellac and cresin are natural adhesives which are used to glue papers. Rubber is another natural adhesive used to join plastic,glass and rubber. There are many synthetic varieties of adhesives like melamine resin, phenoil resin, urea resin and polyvinyl resin. They are used for joining plywood and laminated products.Starch glue, animal glue, casein glue (glue from skimmed milk), sodium silicate glue are also available for joining various materials.

• Sealants: Sealants are the substances used to seal cracks or joints between wall and window frames, glazing and window frame or between roofing sheets. Elastomeric sealants are most efficient. They are based on silicon, acrylic or polysulphide.

• Joints fillers: To prevent seepage of water through construction joints, these materials are used.They should be compressible and resilient. The common joint fillers used are built in strips of metals, bitumen treated felt and cork bound rubber.

9. Heat, electrical and sound insulating materialsv

•  Thermal comfort may be achieved by providing air spaces by using aerated concrete, hollow blocks, using blast furnace slag in mortar and concrete and providing insulators and reflectingpaints.
• Electric insulators are used to separate the conductors carrying electric current. Mica, asbestos, porcelain, rubber, leakalite are electrical insulators. 
• Paraffin and chlorinated diphenyl are liqui dinsulators which are used in transformers. In refrigerators thermocol is used.In auditoriums and cinema halls, sound insulators are required. 
• The commonly used sound insulators are cellular concrete, asbestos, gypsum plaster, pulp boards, perforated plywood, glass mineral wool, etc.

10. Waterproofing and damp-proofing materialsv

• Preventing passage of water from one side of a surface to other side under normal hydrostatic pressure is known as waterproofing while damp-proofing is to prevent transfer of water bycapillary action.

• Bituminous materials, integral compounds, epoxy based materials, slurry coat and elastomeric materials are various waterproofing materials.

11. Thermocol v

• It is a general-purpose crystal polysterene. It can be cut easily with knife or saw. It contains 3–6 million discrete cells/litre. It has insulating efficiency against heat, sound, humidity and shock. It is used as packing material and display board.

12. Epoxy v

• It is a thermosetting polymer. It possesses excellent mechanical and adhesive properties. It is used with paints also.

13. Polyurethene v

• It is a product produced by mixing polymeric diol or triol with a silicon surfactant and a catalyst. This has elasticity of rubber, combined with the toughness of metal. It is used for making gaskets, tiers, bushings, shoe soles, pipes, waterproofing chemicals, etc.

14. Geosyntheticsv

• These are synthetic materials made of nylon, PVC, polypropylene etc. They last long even when buried under soil. Geotextiles, geogrids, geomembranes and geocomposites are commonly used geosynthetics. These materials are used for soil stabilization.

15. Ferrocement v

• Wire meshes embedded with cement and baby jelly is known as ferrocement. Theyare used for making door/window frames and shutters, partition walls, signboards, furnitures and even boats.

16. Cladding materialsv

•  Cladding materials are used to enhance aesthetic appeal of walls, kitchen slab, stairs, roofs, ceiling, etc. Slate, granite, marble, clay tiles, mosaic, glass, wall papers etc. are the commonly used cladding materials in buildings.

17. PVC building products v

• Polyvinyl chloride (PVC) is versatile plastic. Its properties can be easily modified by addition of other compounds. PVC pipes, door and window frames, partition walls, kitchen cabinets, tiles and false ceiling are very popular products.

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 Test on building Materials

Test on aggregates	Aggregate Sample Requirement	Sieve Size recommended to calculate weight loss
Crushing Value Test	Passing through 12.5 mm sieve and retained on 10 mm sieve	2.36 mm
Impact Value Test	Passing through 12.5 mm sieve and retained on 10 mm sieve	2.36 mm
Los Angeles Abrasion Test	Passing through 12.5 mm sieve and retained on 10 mm sieve	1.70 mm
Deval Attrition Test	Passing through 12.5 mm sieve and retained on 10 mm sieve	1.70 mm

 

• For making concrete, aggregate impact value should be less than 45.
• Aggregates used for concrete should have a specific gravity between 2.6 to 2.8.

Angularity

• Angularity is a measure of angularity of aggregate sample. It gives a general idea of shape, void ratio, denseness, packaging and compactness of the aggregate sample.

• Angularity Number = 67−W×100w×G
• where
• W = Aggregate weight filled in the cylinder
• w = Weight of the water filled in the cylinder
• G = specific gravity of aggregate

The angularity number ranges from 0 to 11 for aggregates suitable for making concrete.

• If the angularity number is zero, the solid volume of aggregate is 67% and
•  if angularity number is 11, the solid volume of the aggregate is 56%. 
• Angularity number represents the most practicable rounded aggregates and 
• the angularity number 11 indicates the most angular aggregates that can be tolerated for making concrete which is not so unduly harsh and uneconomical.

Non-destructive testing:

• Non-destructive tests are used to find the strength of existing concrete elements. They are classified as follows.

1. Half-cell electrical potential method:

It is used to detect the corrosion potential of reinforcing bars in concrete.

2. Schmidt or Rebound hammer test:

It is used to evaluate the surface hardness of concrete.

3. Carbonation depth measurement test:

It is used to determine whether moisture has reached the depth of the reinforcing bars.

4. Permeability test:

It is used to measure the flow of water through the concrete.

5. Penetration resistance or Windsor probe test:

It is used to measure the surface hardness and hence te strength of the surface and near-surface layers.

6. Ultrasonic pulse velocity test:

It is mainly used to measure the time of travel of ultrasonic pulse passing through the concrete and hence concrete quality.

1. Kelly ball test:

It is a test that is performed to find the workability of concrete

It is a simple field testing machine that determines the depth to which a 15 cm diameter metal hemisphere weighing 13.6 kg, will sink under its own weight into the fresh concrete. Based on the depth of the penetration workability of concrete is determined.

2. Cone Penetrometer Test (CPT):

The cone penetration test (CPT) has been widely used in geotechnical engineering as an in-situ test to map soil profiles and assess soil properties.

The smaller the size of cube it more close to its parent geometry.

For cube test two types of specimens either cubes of 15 cm × 15 cm × 15 cm or 10 cm × 10 cm × 10 cm depending upon the size of aggregate are used. For most of the works cubical moulds of size 15 cm × 15 cm × 15 cm are commonly used.

This concrete is poured in the mould and tempered properly so as not to have any voids. After 24 hours these moulds are removed and test specimens are put in water for curing. The top surface of these specimen should be made even and smooth. This is done by putting cement paste and spreading smoothly on whole area of specimen.

As per the IS 456-2000, the test results of the sample shall be the average of the strength of three specimens. The individual variation should not be more ± 15% of average than of the average. If more, the test results of the sample are invalid.

An aggregate is said to be elongated if its greatest dimension is greater than 1.8 times the mean diameter.

Test on Cement

• The fineness of the cement is checked to test the proper grinding of the cement which significantly influences the rate of hydration. These two methods is used for determination of the fineness of cement:

1) Air permeability method ( Blaine) 

• The fineness of cement is measured as the specific surface. Specific surface is expressed as the total surface area in square meters of all the cement particles in one kilogram of cement. The higher the specific surface is, the finer cement will be. 

• Fineness test is performed on the Blaine apparatus. It is practically a manometer in the U-tube form. One arm of the manometer is provided at the top with a conical socket to form an airtight fit with the conical surface of the cell.

2) Sieving method 

• This method serves only to demonstrate the presence of coarse cement particles. This method is primarily suited to checking and controlling the production process. The fineness of cement is measured by sieving it on standard sieves. The proportion of cement of which the grain sizes are larger than the specified mesh size is thus determined.  

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Steel

Building Material Civil Engineering

Percentage of carbon

• Steel     0.2 – 2.1
• Stainless steel    < 1.2
• Cast iron    1.8 – 4.5
• Pig Iron    3.5 - 4.5
• The impure form of iron, containing carbon in between 2.0 to 4.5% is known as cast iron.

Different forms of iron are as follows:

Wrought iron: 

• It is a very pure iron where the iron content is of the order of 99.5%. It is produced by re-melting pig iron and some small amount of silicon, sulfur, or phosphorus may be present. It is tough, malleable and ductile and can easily be forged or welded. It cannot, however, take sudden shock. Chains, crane hooks, railway couplings, and such other components may be made of this iron.

Pig iron: 

• It is an intermediate product of the iron industry. It has a very high carbon content, typically 3.8–4.7% (3 to 4%), along with silica and other constituents of dross, which makes it very brittle, and not useful directly as a material except for limited applications.

Cast iron: 

• It is an alloy of iron, carbon, and silicon and it is hard and brittle. Carbon content in CI may be within 1.7% to 3% and carbon may be present as free carbon or iron carbide Fe3C. In general, the types of cast iron are (a) grey cast iron and (b) white cast iron (c) malleable cast iron, etc.

Steel :

• It is basically an alloy of iron and carbon in which the carbon content can be less than 1.7% and carbon is present in the form of iron carbide to impart hardness and strength. 

Two main categories of steel are

• (a) Plain carbon steel and 
• (b) alloy steel.

Name of Steel and its Carbon Content and Uses

Mild steel 

Up to 0.10% 

• Motor body, sheet metal,tin plate, etc.

Up to 0.25%

•  Boiler plates, structural steel, etc.

Medium carbon steel

Up to 0.45%

•  Rails, tyres, etc.

Up to 0.60%

•  Hammers, large stamping and pressing dies, etc.

High carbon steel or hard steel

Up to 0.75% 

• Sledge hammers, springs, stamping dies, etc.

Up to 0.90% 

• Miner’s drills, smith’s tools, stone mason’s tools, etc.

Up to 1.00% 

• Chisels, hammers, saws, wood working tools, etc.

Up to 1.10% 

• Axes, cutlery, drills, knives, picks, punches, etc.

Defects in Steel

The following four types of defects are found in steel.

• 1. Cavities/blow-holes: Cavities or blow-wholes are formed when gas is confined in the molten mass of metal. This confined gas produces bubbles or blow- holes on solidification of metal.

• 2. Cold shortness: Steel with this type of defect cracks when worked in cold state. This defect imparts due to presence of excess amount of phosphorusin the steel.

• 3. Red shortness: Steel having this defect cracks when worked in hot state. This defect happens due to presence of excess amount of sulphur in the steel.

• 4. Segregation: Some constituents of steel solidify at an early stage. Those are separated out from the main mass. This process is known as segregation.

Steel Manufacturing Processes

The following processes are used in manufacturing of steel.

• 1. Bessemer process

• 2. Cementation process

• 3. Crucible steel process

• 4. Duplex process

• 5. Electric process

• 6.LD Process (Linz-Donawitz process)

• 7. Open-hearth process

Market Form of Steel

Various forms of steel available in the market are:

• 1. Angle sections

• 2. Channel sections

• 3. Corrugated sheets

• 4. Expanded metal

• 5. T-sections

• 6. I-sections

• 7. Plates

• 8. Ribbed (HYSD) bars

• 9. Round bars

• 10. Square bars

• 11. Flat bars

• 12. Ribbed mild steel bars

• 13. Thermo-mechanically treated (TMT) bars

• 14. Cold twisted deformed (CTD) bars

• 15. Welded wire fabrics (WWF)

Mechanical Treatment of Steel

• • The purpose of giving mechanical treatment to steel is to give desired shape to the ingots to make steel available in marketable forms.
• • Mechanical treatment of steel requires the following

Types of  operations.

Drawing

• This operation is carried out to reduce the cross-section and to increase the length proportionately.
• This process is used to prepare wires and rods.

Forging

• This operation is carried out by giving repeated blows under a power hammer or press.
• This increases the density and improves grain size of
• metal.
• Forging is used for manufacture of bolts, cramps and in riveting, etc.

Pressing

• It is a slow process, carried out using in equipment known as press.
• The main advantage of this process is it does not involve any shock. Pressing is useful in manufacturing large  number of uniform type engineering products.

Rolling

• It is carried out in specially prepared rolling mills.
• Using rolling process, various shapes, such as angles,channels, flats, joists, rails, etc., are manufactured

Mild Steel

• It has fibrous structure.

• It can be easily hardened and tempered.

• It can be readily forged and welded.

• It can be permanently magnetised.

• Melting point of mild steelis about 1400°C.

• Its specific gravity is 7.80.

• Its ultimate compressive strength is 20 kN/cm 2 .

• Its ultimate tensile and shear strengths are about 60–80 kN/cm 2 .

• It is tougher and more elastic than wrought-iron.

• Used for all types of structural work.

Hard steel

• It cannot be easily hardened and tempered.

• Used for manufacturing cutlery,edge tools, parts exposed to shocks and vibrations.

• It is tougher and more elastic than mild steel.

• Its ultimate tensile strength is about 80–110 kN/cm 2 and ultimate shear strength is about 110 kN/cm 2 .

• Its ultimate compressive strength is 140–200 kN/cm 2 .

•  Its specific gravity is 7.90.

• Melting point hard steel is about 1300°C.

• It can be permanently magnetised.

• It cannot be readily forged and welded.

•  It has granular structure.

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Bitumen

 Building material - Civil Engineering

Tests for bituminous materials

• Ductility test

• Flash and fire point test

• Float test

• Loss on heating test

• Penetration test

• Softening point test

• Solubility test

• Specific gravity test

• Spot test

• Viscocity test

• Water content test

Various tests conducted on bitumen for testing its various properties are as follows:

• Test on Bitumen
• Properties to be tested
• Desirable Value

Ductility Test

• Ductility (Briquettes Apparatus)
• less than 50

Flash and Fire Point Test   

• Flash Point and Fire Point (PenskyMartens Closed Tester)
• greater than 175°

Float Test

• Consistency

Penetration Test

• Hardness or Softness of Bitumen
• 30/40, 60/70 and 80/100

Softening Point Test

• Softening Point (Ring & Ball Test)
• 35° C to 70° C

Specific Gravity Test

• Specific Gravity (Pycnometer)
• 1.01 to 1.03

Water Content Test

• Water Content
• Lesser than 2%

1. Ductility test: 

• The sample is cast in a briquette mould whose cross-section at the minimum width is 10 mm × 10 mm. 
• The test is conducted at a temperature of 27°C ± 0.5°C at a rate of pull of 50 mm ± 2.5mm per minute. 
• Ductility is the value which is expressed as the distance in centimetres to which a standard briquette of bitumen can be stretched before the thread breaks.
• Ductility varies from 0.5–100, where bitumen with ductility > 50 is good bitumen

2. Flash and fire point test:

• (a) The flash point is the lowest temperature at which the vapour of a substance momentarily takes fire in the form of flash under conditions of rest.
• (b) The fire point is the lowest temperature at which the material gets ignited and burns under specified conditions of rest

3. Float test: 

• This test is used to find the consistency of the bituminous material. 
• It is helpful when the material has consistency range which cannot be effectively defined either by orifice viscometer test or penetration test.
•  A float of aluminium is filled with specimen material and is allowed to float. 
• The time required for the water to force its way through the bitumen plug is noted and is indicated as float value.

4. Loss on heating test: 

• The bitumen when heated, the volatiles present in it are evaporated and the bitumen becomes hard. 
• The bitumen to be used in pavement mix should not indicate more than 1% loss in weight on heating.

5. Penetration test: 

• The penetration test is used to find the hardness or softness of bitumen used in road construction by measuring the distance in tenths of millimetre to which a standard needle will penetrate vertically into the sample of bitumen under conditions of temperature.
• The grade of bitumen is specified in terms of penetration value. 80/100 range of penetration value means penetration ranging from 80–100. For hot climates, bitumen grades of low penetration are preferred, and for cold climates higher penetration grades of bitumen are preferred.

6. Softening point test: 

• As the temperature of the material rises, there is a gradual and imperceptible change from a brittle or exceedingly thick and slow-flowing condition to a softer and less viscous state. 
• Softening point of bitumen is usually determined by ring and ball test.

7. Solubility test: 

• Pure bitumen is completely soluble in solvents like carbon disulphide or carbon tetrachloride. 
• A known weight of the sample is taken and dissolved in excess quantity of solvent. 
• Then the solution is filtered for removal of the probable insoluble materials.

8. Specific gravity test: 

• The specific gravity of bitumen is the ratio of mass of given volume of substance to the mass of equal volume of water.

The specific gravity is found by:

• (a) Pycnometer method:
• (b) Balance method:

9. Spot test: 

• It is done for detecting over heated (or) cracked bitumen. 
• A-2 g of bitumen is dissolved in 10 ml of naptha. 
• A drop of solution is taken out after one hour, and it is placed on a filter paper.
• A second drop of solution is taken out after 24 hours, and it is placed on a filter paper. 
• If the spots on the filter paper are of uniform colour, the bitumen is treated as uncracked, otherwise it is called ‘cracked bitumen’.

10. Viscosity test: 

• The resistance to flow by liquid is known as viscosity, and it is thus the inverse of fluidity. 
• At high fluidity, the viscosity is low and at low fluidity, the viscosity is high. 
• Viscosity at any specified temperature is measured by recording the time in seconds for a given quantity of product at the same temperature to flow through an orifice of standard dimensions into a receiver. 
• The higher the viscosity of binder, more time will be recorded and, lower the viscosity of binder, less time will be recorded.

11. Water content test: 

• This test is conducted to know the content of water in a sample of bitumen.

1. Bitumen in

(A) solid state, is called asphalt.

(B) semi fluid state, is called mineral tar.

(C) fluid state, is called petroleum.

(D) All of these

D

2. According to ISI, bitumen is classified into

(A) 2 grades  (B) 4 grades

(C) 6 grades  (D) 10 grades

D

3. Bitumen is generally obtained from

(A) organic material

(B) synthetic material

(C) petroleum product

(D) coal

C

4. Bitumen may be dissolved in

(A) carbon dioxide

(B) water

(C) sodium chloride

(D) carbon disulphide

D

5. Plastic bitumen is generally used for

(A) road pavements.

(B) expansion joints.

(C) crack filling.

(D) None of these

C

6. Bitumen emulsion is

(A) a liquid containing bitumen in suspension.

(B) a paint.

(C) used as anti-corrosive paint.

(D) All of these

D

7. Mastic asphalt is normally used for

(A) sound insulation.

(B) water proofing.

(C) fire proofing.

(D) None of these

B

8. The filler used in plastic bitumen, is

(A) shale powder  (B) talc powder

(C) asbestos powder  (D) plastic powder

C

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