surveying and civil engineering materials unit i basic...

Surveying and Civil Engineering Materials UNIT I Basic Civil And Mechanical Engineering

1

SURVEYING Definition:

Surveying is the art of determining the relative position of points on, above or below the earth

surface by direct or indirect measurements of distance, direction and elevation.

Objectives:

The object of survey is to prepare the map or plan, so that it may represent the area on a

horizontal plane. A plane or map is the horizontal projection of an area and shows only horizontal

distances of the points. Vertical distances between the points are however shown by contour lines or

some other methods.

Purposes of surveying:

1. To produce up to date engineering plans of the areas in which work is going to be carried out

which would be helpful for the design purpose.

2. To determine the required areas and volumes 0f land materials needed during construction.

3. To ensure the construction takes place in the correct relative and absolute position on the

ground.

4. To record the final position of the construction including any design changes.

5. To provide permanent control points from which particularly important projects can be

surveyed.

Primary division of surveying:

Plane surveying:

In this type of surveying the mean surface of the earth is considered as a plane. All

triangles formed by survey lines are considered as plane triangles in which small portions of earth

surface are taken into account and spherical shape is neglected.

Geodetic surveying:

Survey is which the shape (curvature) of the earth surface is taken in the account a higher

degree of precision is exercised in linear and angular measurement is tanned as Geodetic Survey.

A line connecting two points is regarded as an arc. Such surveys extend over large areas.


2

Principles of surveying:

Surveying is Location of a point by measurement from other points of reference and Working

from whole to part.

Classification of surveying:

1. Classification based on the field Survey

i. Land surveying:

a. Topographical survey:

The purpose is to gather survey data about the natural and man – made features of

the land.

b. Cadastral Survey:

This is carried out to mark the boundaries of a land located within the city

municipality, etc.

c. City survey:

This is made in connection with the construction of streets, water supply systems,

sewers and other works.

ii. Marine survey: It deals with bodies of water for purpose of navigation, harbor works.

iii. Astronomical Survey: This carried out to understand the nature and the behavior of the

heavily objects such as sun or any fixed star.

2. Classification based on object of survey

i. Engineering survey: to determination of quantities or to affords sufficient data for designing

of engineering works such as roads and reservoirs.

ii. Military survey: this is used for determining points of strategic importance.

iii. Mine survey: this is exploding the mineral wealth.

iv. Geological survey: This is used for determining the strata for earth’s crust.

v. Archeological survey: This is used for unearthing relics of antiquity.

3. Classification based on Instruments used


3

i. Chain surveying

ii. Theodolite surveying

iii. Plane table surveying

iv. Tachometric surveying

v. Arial surveying

vi. Photographic surveying.

4. Classification based on methods employed:

i. Traverse surveying

ii. Triangulation surveying.

MEASUREMENT OF DISTANCES:

The distance between two points on the surface of earth can be determined by two methods : i.

Direct method, ii. Computative method

i. Direct method: distances measured using tapes, chains etc.

ii. Computative method: Distance measured by using Tacheometry, Triangulation.

Chain surveying:

Linear measurements.

Principle:

To provide a skeleton of frame work consisting of a number of connected triangles. The

triangles are plotted from the length of its sides, measured in the field. The frame work

consists of equilateral triangles.

Terms used in Chain surveying:

Survey station:

It is the main point on the chain line. Which can be at the beginning or at the end? These

are called Main stations.

Subsidiary station:


4

These are the station points which can be selected anywhere on the chain line for running

the auxiliary line. It is also called as Tie station.

Survey lines:

The lines joining the main survey stations are called the survey lines. There are three types

of survey lines, Base line, Check line and Tie line.

LEVELLING

Levelling is a branch of surveying the object of which is :

(1) To find the elevations of given points with respect to a given or assumed datum,

(2) To establish points at a given elevation or at different elevations with respect to a given

or assumed datum.

PRINCIPLES OF LEVELLING

The principle of levell lies in furnishing a horizontal line of sight and finds the vertical distance of

the points above or below the line of site. A line of sight is provided with a level, and a graduated

leveling staff provides the vertical height of a station with reference to the level line.

INSTRUMENTS USED FOR LEVELLING

The instruments commonly used in direct levelling are:

(1) A level

(2) A leveling staff.

1. LEVEL

A Level consists of the following four parts:

1. A telescope to provide line of sight

2. A level tube to make the line of sight horizontal

3. A leveling head (tribrach and trivet stage) to bring the

4. Bubble in its centre of run

5. A tripod to support the instrument.

Types of levels


5

1. Dumpy level

2. Wye level

3. Reversible level

4. Tilting level

Dumpy level

1. The dumpy level consists of a telescope tube firmly secured in two collars fixed by screws to the

stage carried by the vertical spindle.

2. The modern form of dumpy level has the telescope tube and the vertical spindle cast in one piece

and a long bubble tube is attached to the top of the telescope. This form is known as solid dumpy.

Following are the parts of the dumpy level:

1. TELESCOPE, 2. EYE-PIECE, 3. RAY SHADE, 4. OBJECTIVE END,

5. LONGITUDINAL BUBBLE, 6. FOOT SCREWS, 7. UPPER PARALLEL PLATE,

8. DIAPHRAGM ADJUSTING SCREWS, 9. BUBBLE TUBE ADJUSTING SCREWS,

10. TRANSVERSE BUBBLE TUBE.

• In some of the instruments, a clamp Screw is provided to control the movement of the spindle

about the vertical axis.

• For small or precise movement, a slow motion screw (or tangent screw) is also provided.

• The leveling head generally con of two parallel plates with either three-foot screws.

• The upper plate is known as tri branch and the lower plate is known as trivet which can be

screwed on to a tripod.

The advantages of the dumpy level over the Wye level are:

(i) Simpler construction with fewer movable parts.


6

(ii) Fewer adjustments to be made.

(iii) Longer Life of the adjustments

LEVELLING STAFF

• A levelling staff is a straight rectangular rod having graduations, the foot of the staff representing

zero reading.

• The purpose of a level is to establish a horizontal line of sight.

• The purpose of the levelling staff is to determine the amount by which the station is above or

below the line of sight.

• Levelling staves may be divided into two classes

(1) Self-reading staff, (2) Target staff.

SELF-READING STAFF

There are usually three forms of self-reading staff:

(a) Solid staff

(b) Folding staff

(c) Telescopic staff (Sop with pattern).

� Fig (a) and (b) show the patterns of a solid staff in English units while (c)

and (d ) show that in metric unit.

� In must common forms, the smallest division is of 0.01 ft. or


7

� The above fig. shows a sop with pattern staff arranged in three telescopic lengths.

� When fully extended, it is usually of 1.4 ft (or 5 m) length. The 14 ft. staff has solid top length of

4’ 6” sliding into the central box of 4’ 6” length.

� The central box, in turn, slides into lower box of 5’ length. In the 5 m staff, the three

corresponding lengths are usually 1.5m, 1.5 m and 2 m.

� The above fig shows a folding staff usually 10 ft long having a hinge at the middle of its length. When

not in use, the rod can be folded about the hinge so that it becomes convenient to carry it from one

place to the other.

� The hundredths of feet are indicated by alternate white and black spaces, the top of a black space

indicating odd hundredths and top of a white space indicating even hundredths.

Target Staff


8

� Fig. shows a target staff having a sliding target equipped with vernier. The rod consists of two

sliding lengths, the lower one of approx. 7 ft and the upper one of 6 ft.

� The rod is graduated in feet, tenths and hundredths, and the vernier of the target enables the

readings to be taken up to a thousandth part of a foot.

� For readings below 7 ft the target is slided to the lower part while for readings above that, the

target is fixed to the 7 ft mark of the upper length.

� For taking the reading, the level man directs the staff man to raise or lower the target till it is

bisected by the line of sight.

� The staff holder then clamps the target and takes the reading & the Upper part of the staff is

graduated from the top downwards.

�

PROCESS OF LEVELLING

(i) INSTRUMENT STATION:

A point where instrument is set up for observations is called instrument station.

(ii) HEIGHT OF INSTRUMENT (Hi)

The elevation of line of site with respect to assumed datum is known as height of instrument.

It does not mean the height of telescope above the ground level were the level is setup.

BACK SITE: (BS)

A first site taken on a level staff held at position of known elevation is called back site. It

ascertains the amount by which the line of sight is above or below the elevation of the point. Back site

enable the surveyor to obtain the height of instrument.

FORE SITE: (FS)

The site on a level staff held at a point of unknown elevation to ascertain by what extent the

point is above or below the line of site is called fore site. Fore site enables surveyor to obtain the

elevation of the point.

CHANGE POINT: (CP)


9

The point at which both a fore sight and back sight are taken during the operation of levelling is

called a change point. Sights are taken from two different instrument station a fore sight ascertains the

elevation of point to establish the height of instrument at the new instrument station. The change point

is always selected on a relatively permanent point.

INTERMEDIATE SIGHT: (IS)

The F.S taken on a level staff held at points between two turning points to determine the

elevation of points is known as intermediate sight. It may be noted that for one setting of the level there

will be only a back sight and fore sight but there can be a number of intermediate sights.

ERRORS IN LEVELLING:

Errors in leveling may be categorized into

1. Personal error

2. Errors due to natural factors

3. Instrumental error

PERSONAL ERROR:-

Personal error include the following

(i) Error in sighting:

This is caused when it is difficult to see the exact coincide of the crosshairs and the staff graduation. This

may be either due to long sights or due to poor focusing of the crosshair. Some times atmospheric air,

atmospheric condition also cause on error in sighting. This error is accidental and may be classified as

compensative.

(ii) Error in manipulation:-

This is due to careless setting up of the level neither the telescope nor the tripod should be

disturbed while taking readings. The instrument should be set up on a firm ground and carefully

leveled.

Take care that the bubble is centre when the readings are observed. If the bubble is not

centered a Horizontal axis telescope gets inclined affecting the staff readings. The error is more for

long sights & less for short sights. To avoid the error the observer should develop the habit of checking

the bubble before and after taking reading.

(iii) Non Vertically of staff :


10

If the staff is not held vertical during observation of the staff reading the observed value will

be higher than the actual value. The staff should be held vertical using a plumb bob.

Error is reading the staff:

These error generally committed are

(i) Reading the staff up side down.

(ii) Reading top or bottom hair instead of center hair.

(iii) Concentrating the attention on decimal part of reading and entering the whole value

wrongly.

(iv) Reading the inverted staff as a vertically held staff.

Error is recording & computation:

Common errors is recording are

(i) Entering the reading in the wrong column that is B.S reading in the I.S or F.S column.

(ii) Recording the reading with digits inters change.

(iii) Omitting on entry.

(iv) Adding the F.S reading instead of subtracting with and subtracting a B.S reading instead

of adding.

Errors due to natural causes:

(i) Errors due to curvature :-

The curvature of the earth surface lowers the elevation of the station and it is directly

proportional to the square of the horizontal distance between the staff position and the point of

observation. The correction of the curvature has to be subtracted from the observe staff reading to get

correct reading. In case of ordinary leveling error due to curvature in negligible that is only 0.003m for a

sight of 300 m length.

(ii) Error due to refraction :-

The effect of refraction on the observe readings is opposite to that of the curvature.

Refraction rise the elevation of the station on the error is also professional to the square of the

horizontal distance of the station from the level. This is negligible for short sites and it’s generally

ignored in ordinary leveling.


11

(iii) Error due to wind & sun :-

Due to strong winds it is always difficult to hold the staffs vertical due to non verticality of

the staff the observed reading are higher. The wind is also responsible for small disturbance in the

instrument level. In strong winds it’s always advisable to suspend the work.

The sun causes a considerable trouble. It’s recommended to protect the objective by an

umbrella. The effect of sun in also cause’s elongation of the staff due to increased temperature but in

ordinary leveling the changing in length is negligible.

Instrumental error:

(i) Imperfect adjustment of level:- In a perfected adjusted level a line of collimation remains

horizontal when the bubble of the level tube occupies the central position. When adjustment is not

perfect the line of collimation is either inclined upwards or downwards or observed reading are either

more a less. Such error gets compensative. If the B.S & F.S distance are kept equal as in the case of the

leveling. But in the case of inter mediate site the distance reading are thrown into error by a different

amount. Incase of leveling a steep slopes.

(ii) Defecting level tube: If the bubble of level tube is sluggish. It will remain centre even if the

bubble axis is not horizontal or on the other hand if it’s two sensitive a reasonable time is spent to bring

a bubble centre. Irregularly of curvature of the tube is also a series defect.

The effect of deflective level tube also gets neutralized if the sights are of equal length.

CONSTRUCTION MATERIALS

STONES Definition: Stone is the naturally available material and is obtained from rocks. Classifications of Rock:

� Geological

� Physical

� Chemical

Geological: Igneous rock:


12

The rocks which are formed by cooling of magma are known as igneous rocks which are inside earth’s surface.

Sedimentary rocks: They are formed by deposition of products of weathering on the pre existing rocks. These products due to wind, rain, frost etc... E.g.: limestone, gypsum.

Metamorphic: When the preexisting rocks are subjected to great heat and pressure they are changed in

character and forms metamorphic rocks. E.g.: marble Physical:

� Stratified rocks

� Unstratified rocks

� Foliated

Stratified:

These rocks possess planes of stratification or cleavage and such rocks can be easily being split up along these planes. Unstratified:

These rocks do not have any definite planes.

Foliated: These rocks have a tendency to be split up into definite direction only. Chemical classifications:

� Siliceous � Argillaceous � Calcareous

Siliceous: In these silica predominates. It is hard and durable.

Argillaceous: In these clay predominates. These are hard and durable.

Calcareous: In these calcium predominates. The durability depends upon the constitutes present. Qualities:

� It should be homogeneous in structure. � It should be free from cracks. � It should be easily workable. � It must be fire resistant. � It should be easily obtainable.


13

Quarrying: � By hand tool � By blasting �

By hand tools: They are executed by pick-axes hammer, chisels, etc... By blasting: In this process explosives are used.. Uses:

o Stones are used for pavements o Used for foundations o Ballast in railways o Used for bridges, dams, etc…

Characteristics of good building stone

The characteristics of good building stone are:

a) Uniform color and Appearance

b) Uniform grain Structure

c) High Strength

d) Moderate Weight

e) Hardness

f) Toughness

g) Low Porosity and absorption

h) Well Seasoned

i) Good Workability

A GOOD BUILDING STONE SHOULD HAVE THE FOLLOWING QUALITIES:

Appearance:

For face work it should have fine, compact texture. Light colored stone is preferred as it is more

durable.

Structure:


14

A broken stone should not be dull in appearance and should have uniform texture free from

cavities, cracks and patches of loose or soft material. Stratifications should not be visible to naked eye.

Strength:

A stone should be strong and durable to withstand the disintegrating action of weather.

Compressive strength of building stones in practice range between 60 to 200 N/mm2.

Weight:

It is an indication of the porosity and density. For stability of structures such as dams, retaining

walls etc. heavier stones are required, whereas for arches, vaults, domes etc. light stones are used.

Hardness:

This property is important for floors, pavements, aprons of bridges; etc. The hardness is

determined by the mohs scale.

Toughness:

The measure of impact that a stone can withstand is defined as toughness. The stone used should

be tough when vibratory or moving loads are anticipated.

Porosity and absorption:

Porosity depends on the mineral constituents, cooling time and structural formation. A porous stone

disintegrates as the absorbed rain water frezes, expands and causes cracking. Permissible water

absorption for some of the stoners is given in table.

Seasoning:

The stone should be will seasoned.

Weathering:

The resistance of stone against the wear and tear due to natural agencies should be high.

Workability:

Stone should be workable so that cutting, dressing and bringing it out in the required shape and

size may not be uneconomical.

Fire resistance:


15

Stones should be free from calcium carbonated, oxides of iron, and minerals having different

coefficients of thermal expansion. Limestone, however can withstand a little higher temperature ie Up

to 8000C after which they disintegrate.

Specific Gravity:

The specific Gravity of most of the stones lies between 2.3 to 2.5

Thermal Movement:

Thermal movements alone are usually not trouble some. However joints in coping and parapets

open out inletting the rain water causing trouble. An exposure of one side of marble slab to heat may

cause that side to expand and the slab warps. On cooling the slab does not go back to its original shape.

Crushing strength:

Minimum average value should be 3.5N/mm2. Strength of individual block should not fall below

the average value by more than 20 percent.

Water absorption:

It should not be more than 20 percent.

SANDS

Sand is formed by the decomposition of sand stones due to various effects of weather. Functions of sand: The sand is used in the concrete for the following purpose: Bulk: It does not increase the strength of the mortar but if bulk is increased the cost is reduced. Shrinkage: It prevents excessive shrinkage during drying Strength: It helps in the adjustment of strength by variation of its ratio with cement. Surface area: It sub divides the paste of binding material and increase the surface area. Classifications:

� Pit sand


16

� River sand � Sea sand

Pit sand: It is excavated from the depth of about 1m to 2m. It consists of sharp angular grains which are free from salts. River sand: It is obtained from bank of bed of river. It consist of fine rounded grain and available in clean condition. Sea sand: It is obtained from sea shores. It consists of fire randed grains and contains salt. These salts attract moisture from the Atmosphere and not used for engineering purpose. Classification:

� Fine sand � Coarse sand � Gravelly

Fine sand: The sand passing through a screen with clear opening 1.5875mm and used for plastering. Coarse sand: This sand passing through a screen with clear with clear openings 3.175mm and used for masonry. Gravelly sand: This sand passing through a screen with clear openings as 7.62mm and used for concrete work. BULKING OF SAND: The presence of moisture in sand increases the volume of sand and it is known as bulking of sand. PROPERTIES:

1. It should be chemically inert 2. It should be clean. 3. It should not contain salts. 4. It should be well graded.

TESTS:

CLAY: 1. A glass of water is taken out and sand is placed. It is vigorously shaken and allowed to

settle. If clay is present its layer is formed on top of sand.


17

2. The color of sand will indicate the purity. 3. Add sodium hydroxide to sand and stride. If the color of solution changes to brown and it indicates the presence of organic matter.

BRICKS

It is the oldest material and it is extensively used as leading building material because of its (a) durability

(b) strength

(c) low cost

(d) Availability.

COMPOSITION: (a) alumina (b) oxide of iron (c) silica (d) magnesia (e) lime Alumina:

A good brick contains about 20% to 30% alumina. Silica:

A good brick contains about 50% to 60% of silica. It prevents cracking. Lime:

A small quantity of lime not exceeding 5% is desirable. It prevents shrinkage. Oxide of iron:

A small quantity of oxide 5% to 6% is desirable. It also imports red color. Harmful ingredients: Lime & alkalis: The excess of lime and alkalis causes the brick to melt and lost its shape. Iron pyrites: If iron pyrites are present in brick they are disintegrated during burning. Organic matter: This organic matter in brick earth assists in burning. But if such matter is not completely burnt the bricks become porous. QUALITIES OF GOOD BRICK:

� It should be table moulded. � It should have uniform color � It should be free from cracks � It should have low thermal conductivity


18

� It should not break on hard ground when dropped from a height of 1m. � It should have min strength of 3.5N/mm2.

CLASSIFICATION:

(a) unburnt or sun dried bricks (b) burnt bricks

Unburnt bricks: They are dried with the help of heat received from the sun after the process of moulding.

Burnt bricks: They are classified into four categories:

1. first class 2. second class 3. third class 4. Fourth class.

First class: Used for superior works.

Second class: Used at places where brick work is to be provided with coat of plaster. Third class:

Used for temporary works and at places where rainfall is not heavy Fourth class:

They used as aggregates for concrete in foundations, floors.

Uses: I. It is used for construction of walls. II. It is used as refractory material III. It is used in construction of chimney IV. Bricks with cavities are known as hollow bricks used for front wall structures V. Sand-line bricks used for ornamental works

MOULDING OF BRICKS:

Hand moulding: It is done by rectangular box with open at top and bottom. it may be wood or steel.

Types: Ground moulding: Table moulding

GROUND MOULDING: First small portion of ground is cleared and leveled. Fine sand is sprinkled over it. Moulding is dipped in water and kept on ground and clay is pressed by hand so that all


19

corners are filled with clay sand excess is scraped by strikes. Process is repeated fill the ground is covered with bricks. After that bricks become dry, it is sent for next of drying.

TABLE MOULDING:

Instead of ground in table the table used is the size of 2mx1m.

TABLE MOULDING: When bricks are manufactured in huge quantity these are done by machines. The machine

containing the rectangular opening under pressure, it is cut into strips by wire fixed in frames.

DRYING OF BRICKS: This is done in drying yards. Bricks are stacked in 8 to 10 bricks in each row and they are dried for

5 to 12 days

BURNING: It imports hardness and strength of bricks. It must be done carefully because unburnt bricks remains soft and over burnt bricks become brittle and hence break easily. It is done in kilns.

HOLLOW BLOCKS:

Hollow blocks are manufactured from a thoroughly ground; lump free, well mixed clay mass of

medium plasticity to allow moulding. The process of manufacture is similar to that of stiff mud bricks.

These are used to reduce he dead weight of the masonry and for exterior as well as partition walls.

Types:

Type A – Blocks with both faces keyed for plastering or rendering.

Type B – Blocks with both faces smooth for use without plastering or rendering on either side.

Type C- Blocks with one face keyed and one face smooth.

Length Breadth Height (Cm) (Cm) (Cm) 19 19 9 29 9 9 29 14 9

REFRACTORY BRICKS:

Refractory bricks are made from fire clay. The process of manufacturing is similar to ordinary

brick, but burnt at very high temperatures in special kilns. Fire clay mortar is used to lay refractory

bricks.


20

Properties:

1. The color is whitish yellow or light brown

2. The water absorption of fire clay bricks varies from 4-10%

3. The compressive strength ranges between 150 to 200 N/mm2.

Acid Refractory Bricks:

It consists of silica bricks and ganister bricks (Ganister- a hard colored sand stone containing 10

per cent clay and 2 percent of lime), used in lining furnaces having acidic slag, steel industry and coke

oven.

Basic refractory bricks:

It consists of magnesia bricks (magnesia minimum 85 percent calcium oxide maximum 25 percent

and silica maximum 5.5 percent) and bauxite bricks(minimum 85 percent aluminum oxide and maximum

20 percent clay).these are highly resistant to corrosion and are used for lining furnaces having basic

slag.

Natural refractory Bricks:

It consists of chromoite bricks (50 percent chrome and iron ore containing 30 percent iron oxide

and bauxite containing 15 percent aluminum and 5 percent silica) chrome magnesite bricks(Cr2o3 18

percent MgO 30 percent ) spinel and forsterite bricks. The neutral Refractory bricks are suitable at

places where acidic and basic linings are to be separated, e.g. for lining copper reverberatory furnace.

Bricks are classified on the basis of strength and durability as

First class Bricks

1. There are thoroughly burnt with deep red, cherzy or copper colours.

2. The surface should be smooth and rectangular, with parallel, sharp and straight edges and

square corners.

3. They should be free form flaws, cracks and stones.

4. They should have uniform lexhure.


21

5. No impression should be left on brick when a scratch is made by a figer nail.

6. Later absorption should be 12.15% of its dry weight when immersed in cold water for 24 hours.

7. The fractured surface of the brick should not shour lumps of line.

8. The crushing strength of the brick should not be less then 10.5 N / mm2

Second class Bricks

i. Small cracks and distortions are permitted.

ii. A little higher woler absorption of about 16- 20% of its dry weight is allowed

iii. The crushing strength not is less than 7.0 N/mm2.

Third Class Bricks

1. These are under burnt bricks.

2. They are soft and light colored producing a dull sound when struck against each other. Water

absorption is about 25% of dry weight.

Fourth class Bricks

1. These are over burnt and badly distorted in shape and size and are brittle in nature.

2. It uses the bellas 1. of such bricks is used for foundation and floors in lime concrete and road

metal

II. On the Basis of Usage.

Common Brick

In a general multi-purpose unit manufactured economically without special reference to

appearance. These may vary greatly in strength and durability and are used for filling, backing

and in walls where appearance in of no consequence.

Facing Brick

Facing Brick are made primarily with a new to have good appearance, either of color or lexture or

both. These are durable under severe exposure and are used in founts of building walls for which

a pleasing appearance is desired.

III. On the Basis of finish.

Sand faced Brick

It has textured surface manufactured by sprinkling and or the inner surface of the mould.


22

Rustic Brick

It has mechanically lextured finish, varying in pattern .On the basis of manufacture.

Hand made:

These bricks are hand moulded

Machine made

Depending upon mechanical arrangement, bricks are known as wire cut bricks – bricks cut from

clay extruded in a column and into brick sizes by wires.

IV. On the Basis of burning

Pale bricks: Pale bricks are under burnt

Body bricks: Body bricks are well burnt bricks occupying central portion of the kiln.

Arch Bricks: Arch Bricks are over burnt also known as clinker bricks.

Preparation of Brick Earth

1. Unsoiling

i. The soil used for making building bricks should be processed so that, it is free of gravel, coarse

sand, line and base bar particles, organic matter.

ii. About 20 cm of the top layer of the earth, normally containing stones, pebbles, gravel, tools

etc is removed after clearing the trees and vegetation.

ii. Digging:

After removing the top layer of the earth, proportions of additives such as fly ash, sandy

loom, rice husk ash, stone dust, etc. should be stored over the plane surface on volume basis. The

digging operation should be done before rains.

iii. Weathering:

Stones, gravel, pebble, roots etc are removed form the dug earth and the soil is heaped on

level ground in layer of 60 - 120 cm thickness. The soil is left in heaps and exposed to weather for

at least one month in cases where such weathering is considered necessary for the soil. This is

done to develop homogeneity in the mass of soil, particularly if they are from different sources

and also to eliminate the impurities. Soluble salts in the clay would also be eroded by rain to some


23

extent, which otherwise could have caused scumming at the time of burning of the bricks in the

kiln.

iv. Blending

The earth is then mixed with sandy earth and calcurious earth in suitable proportions to

modify the compositions of soil. Moderate amount of water is mixed so as to obtain the right

consistency for moulding. The mass is then mixed uniformly. Addition of water to the soil at the

damps is necessary with spacles. Addition of water to the soil at the dumps is necessary for easy

mixing and workability, but addition of water should be controlled in such a way that it may not

create a problem in moulding and drying.

V. Tempering

Tempering consists of kneeling the earth so as to make the mass shift and plasticise. It

should preferably be carried out by storing the soil in a cool place in layers of about 30 cm

thickness for not less than 36 hours. This will ensure homogeneity in the mass of clay for

subsequent process. For manufacturing good bricks, tempering is done in pug mills. And

operation is called pugging. Pug mill consists of a conical iron tube shown in figure. The mill is

sunk 60 cm it to earth. A vertical shaft with a number of horizontal arms filled with knives, is

provided at the center of tube. This central shaft is rotated. The knives cut and rough the clay and

break all the clogs or lumps when the shaft rotates.

Moulding

1. Hand moulding

a. Ground Moulding

In this process, the ground is leveled and sand in sprinkled on it. The clay is molded to the

shape with wooden moulds on the leveled surface. The molded bricks are left on the ground for

drying, such bricks don’t have frog and the lower brick surface becomes too rough. To overcome

these defects, moulding blocks or boards are used at the base of the mould. The process consists

of shaping in hands a lump of well-pugged earth, slightly more than that of the brick volume. The

molder then gives blows with his lists and process the earth properly in the corners of the mould

with his thumb. The surplus clay on the top surface is removed with a sharp edge metal plate


24

called strike.

b. Table Moulding

The bricks are molded on stock boards nailed on the moulding table. Stock boards have

the projection for forming the frog. The process of filling clay in the mould is the same as

explained above. After this thin band called pollet in placed over the mould. The mould

containing the brick is then smartly lifted along with the stock board and inverted so that the

molded clay along with the mould rests on the pallet.

II. Machine Moulding

a. Plastic Method.

The pugged, stiffer clay is forced through a rectangular opening of brick size by

means of layer clay out of the opening in the form of an bar. The bricks are cut from the

bar by a frame consisting of several wires at a distance of brick size. This is a quick and

economical process.

ii. Dry – press Method

The moist, powdered clay is fed into the mould on a mechanically operated press, where it

in subjected to high pressure, the clay in the mould takes the shape of bricks. Such pressured

bricks are more dense, smooth and uniform than ordinary bricks.

Process of Burning of Bricks

i. Dehydration (400 - 6500C)

This is also known as water smoking stage.

(1) The water which has been retained in the pores of the clay after drying is driven off

and the clay losses its plasticity.

2. Some of the carbon matter in the brick is burnt.

3. A portion of sulphur is distilled from pyrites.

4. Hydrous minerals like ferric hydroxide are dehydrated.

5. The carbonate minerals are also decarbonizes.

6. Two rapid heating causes cracking or bursting of the bricks, on the other hand, if alkali

is contained in the clay or sulphur is present in large amount in the coal quality of brick is

deteoriated.


25

ii. Oxidation period (650-900oC)

During the oxidation period

1. Residues of carbon is eliminated.

2. The ferrous iron is oxidized to the ferric form.

3. The removal of sulphur is completed only after the carbon has been eliminated.

4. Sulphur on account of its affinity for oxygen, also holds back the oxidation of iron.

5. Sand is often added to the raw clay to produce a more open structure and thus provide

escape of gases generated in burning.

iii. Vitrification

To convert the mass in to glass like substance – the temperature ranges from 900 – 1100 oC

for low melting clay and 1000 – 1250o C for high melting clay. Virtrification period may further be

divided into a. In a pient vitrification, at which the clay has softened sufficiently to cause

adherence but not enough to close the pores or causes loss of space on cooling the material

cannot be scratched by the knife.

b. Complete vitrification, more or less will be marked by maximum shrinkage.

c. Viscous vitrification produced by a further increase in temperature which results in a soft

molten mass, a gradual loss in shape, and a glassy structure after cooling. Burning of bricks is

done in a clamp or Kiln. A clamp is a temporary structure whereas kiln is a permanent one

COMMON DEFECTS IN BRICK

a. Over burning of Bricks:

Bricks should be burned at temperatures at which complete and viscous vitrification

occur. However, if the bricks are over burnt a soft molten mass in produced and the brick loose

their shape.

b.Under – burning of Bricks:

When Bricks are to be burnt to cause complete vitrification, some layers are not softened

because of in sufficient heat and the pores are not closed. This results in higher degree of water

absorption and less compressive strength. These bricks are not used for construction works.


26

c. Bloating

This defect is observed as spongy swollen mass over the surface of burnt bricks. It is

caused due to the presence of excess carbonaceous material and sulphur is brick – clay.

d. Black core:

When brick –clay contains bituminous matter or carbon and they are not completely

removed by oxidation the brick results in black core mainly because of improper burning.

e. Efflorscence:

This defect is caused because of alkalis present in bricks. When bricks come in contact

with moisture, water is absorbed and the alkalis crystalize. On drying grey or white powder

patches appear on the brick surface. This can be minimized by selecting proper clay materials for

brick manufacturing, preventing moisture to come in contact with the masonry, by providing

water proof coping and by using water repellent materials in mortar and by providing clamp

proof course.

f. Chuffs

The deformation of the shape of bricks cause by the rainwater falling on hollow

a brick is known as chuffs.

g. Checks or cracks:

This defect may be because of lumps of lime or excess of water. In case of the former,

when bricks come in contact with water, the absorbed water reacts with lime nodules causing

expansion and a consequent disintegration of bricks whereas shrinkage and burning crocks result

when exes of water is added during brick manufacturing.

h. Spots:

Iron sulphide, if present in the brick clay, results in clark surface spots on the brick

surfaces. Such bricks through not harmful are unsuitable for exposed masonry work.

i. Blisters:

Broken filters are generally caused on the surface of sewer pope and drain filters due to air

impressoned during their moulding.


27

j. Laminations:

These are caused by the entrapped air in the voids of clay. Laminations produce thin

lamina on the brick faces which whether out on exposure such bricks are weak in structure.

CEMENT

Cement is a substance act as binding agent. Constituents:

1. Argillaceous 2. Calcareous

In argillaceous clay is the main ingredient and un calcareous calcium carbonate is the main ingredient. Setting Action: When water is added to cement, the ingredients of cement react chemically with water and forms various complicated chemical compounds which import strength to cement. This phenomenon is called as hardening.

Manufacture of cement

Following three district operations are involved in the manufacture of normal setting or ordinary

or Portland cement.

1. Mixing of raw materials

2. Burning

3. Grinding

Mixing of raw materials:

The raw materials such as limestone or chalk and shale or clay may be mixed either in dry

condition or is wet condition. The process is accordingly known as the dry process or the wet

process of mixing.

Dry process:

In this process, the raw materials are first reduced in size at about 25 mm in crushers. A

current of dry air is then passed over these dried materials. These dried materials are then

pulverized into fire powder in ball mills and tube mills. All these operations are done separately

for each raw material and they are stored in hoppers. They are then mixed in correct proportions

and made ready for the feed at rotary Kiln. This finely ground powder at raw materials is known

as the raw mix and it is stored in storage tank. Fig shows the flow diagram of mixing at raw


28

materials by dry process. The dry process has been modernized and it is widely used at present

because of the following reasons.

Competition:

At present, several dry process cement plants are vying or competing with each other.

The cement consumers in general and the practicing civil engineers in particular are greatly

benefited by such competition.

Power:

The blending of dry powders has now perfected and the wet process, which required

much higher consumption of power, can be replaced with confidence.

Quality of cement: It is found that the quality of the production no longer depended on the

skilled operators and workmen because temperature control and proportioning can be done

automatically through a centralized control room.

Technology:

There has been several advances is instrumentation. Computerization and quality control,

the application of the modern technology has made the production of cement by dry process

more economical and of superior quality. Following is the procedure of anufacture of cement by

the dry process using modern technology.

i) Most of the cement factories are located very close to the limestone quarries. The boulders up

to 1.2 m size are transported in huge dumpers up to 300 KN capacities and dumped into the

hopper of the crusher.

ii) The hammer mill crushers of single stage are now used for crushing as against the time

consuming two stage crushers used in earlier plants. The modern stacker – reclaimed system is

now in use in most of the modern plants. The stacker helps in spreading the crushed materials in

horizontal layers and the reclaimed restricts in the variation at calcium carbonate is crushed

limestone to less than 1% thereby minimizing quality variation is the materials.

iii) The argillaceous or clay materials found in the quarry are also dumped into the crusher and

stacked along with the limestone iv) The crushed materials are checked for calcium carbonate,

lime alumina, ferrous oxide and silica contents. In a similar way, if limestone is found to contain


29

less content of lime, the high grade limestone is crushed and stored separately in the raw material

hopper.

v) The additive material and crushed limestone are conveyed to the storage hopers. The raw

materials are fed to the raw mill by means of a conveyer and proportioned by use of weight

feeders which are adjusted as per the chemical analysis done on the raw materials taken from the

hoppers from time to tome.

vi) The materials are ground to the desired fineness in the raw mill. In some of the modern

plants, the high efficiency. Vertical grinding mills are installed The fine powder which energies

as a result of grinding in the raw mill is blown upwards, collected in cyclones and fed to the giant

sized continuous blending and storage silo by use of aeropole . The advantage of these silos is

that one stage of pumping is eliminated which has inevitable in the traditional pattern of different

silos for blending and storage.

vii) The material is dropped merely by gravity from the blending to the storage silo thereby

conserving

viii) The material is than once again, pumped using an aerosol onto he pre heater. The most

modern heater have five stage fro m 60 to 850 c has hard gas at temperature 1000 c is blown

against the falling gradient the material from the bottom of the pre heater is fed to the rotary kiln

due to the use of multi stage pre heater in the modern plant, the length of rotary kiln is

considerably reduced there by resulting in saving maintenance cost and power requirement

Wet process:

In the earlier part of the century from 1913 to 1960 the wee process was used for the

manufacture of cement. From 1913 onwards ‘cement industries under went a no of changes

mainly to suit the requirement of manufactures and government polishes till 1982.

All the cement plants setup of after 1980 use the dry process for the manufacture of cement. In

this process the calcareous materials such as lime stone are crushed and stored in silos for storage

tank now the crushed lime stone from silos and red clay from the basins are allowed fall in the

channel in correct propos ion this channel leads the material to grinding mills where they are

brought in to ultimate contact to form what is known as the slurry.


30

The grinding is carried out either in ball mill or tube mill or both. The slurry is let, to correcting

basin where it is constantly stirred at the stage the chemical composition is adjusted as necessary.

The corrected slurry is stored in storage tanks and kept ready to serve as feed for rotary kiln in

this fig. show the flow diagram of mixing of raw materiel by the wet process. It is thus seen that is

case of mixing of raw materials by dry process the raw mix is formed and in case of mixing of raw

materials by wet process the slurry is formed the remaining two operation namely burning in

grinding are the same for both the process

Burning:

The burning is carried out in a rotary kiln as shown in fig the rotary kiln is formed of steel

tube is diameter varies from 90m to 120m. it is laid at a gradient of about 1in 25 to 1in 30 the kiln

supported at intervals by column of masonry or concrete the refractory lining is provided on the

in side surface of rotary kiln it is so arranged that the kiln rotates at about 1to 3 revolution per mint

about is longitudinal axis . The corrected slurry is injected at the upper end of the kiln in the fig

shows the rotary kiln for the wet process hot gases or planes or forced through the lawyer end of

the kiln. The portion of the kiln near its upper end is known as the dry zone and in this zone, the

slurry of evaporated as the slurry gradually descends there is raise in temperature and in the next

sections of kiln, the carbon dioxide from slurry is evaporated. These small pumps known as the

modulus are formed at the stage. This modulus then gradually roll down passing through zone of

rising temperature and altimetry reach to the burning zone when temperature is about 1400 c to


31

500 c In burning zone, the calcimined product is formed and modulus are converted into small

hard dark greenness blue balls which are known as clinkers. In the modern technology of dry

process, the coal brought from the coal fields is pulverized in vertical coal mill and it is stored in

silo it is pumped with required quantity of air through the burns. The preheated Raw material

rolled down kiln and gets heated to such on extent that the carbon dioxide is driven with

computation gases. The material is heated to temperature of nearly 1400 c to 1500 c when it gets

fused together. The fused product is known as the clinkers or raw cement. The size clinkers vary

from 3mm to 20mm. and they are very hot when n the come out of burning zone of kiln. the

clinker temperature at the outlet of kiln is nearly 1000c .A rotary kiln of small size is provide to

cool down the hot clinkers. It is laid in opposite directions as shown fig. and the cooled clinkers

having temperature of about 95 c are collected in containers of suitable size.

Grinding:

The clinkers as obtained from the rotary kiln are finally ground in ball mils and tube mills.

During grindings a small gentrify. About 3 to 4 percent of gypsum is added. The gypsum control

the initial setting time of cement. If gypsum is not added the cement. If gypsum is not added, the

cement would set as soon as water is added. The gypsum acts as retorted and its delays the

setting action of cement. It thus permits cement to the mixed with the aggregate and to be placed

in position.

The grinding of clingers is modern plants is carried out in the cement mill which contains

chromium steel balls of varies this balls with in the mill and grind the mixer which is collected in a

Hooper and taken in bucket elevator for storage in silos. The cement from silos is feet to the

pacer machines. Most of the modern plans have electric backing plant having provision to

account for the weight of empty bags of different types and to ensure a 50kg net weight of

cement bag with + or – 20g limits each bag of cement contains 50kg or 500N or about 0.035m3 of

cement this bag are automatically discharge from the bakers to the conveyer belts to different

loading are. They are carefully stored in a dry place.


32

The properties of cement

i) It gives strength to the masonry

ii) It gives an excellent binding material

iii) It is easily workable

iv) It is posses a good plasticity

v) It is stiffness or hardness early

The functions of the ingredients of Portland cement

lumina content should not be less than 32% and ratio by weight of alumina to the lime should be

between 0.85 to 1.30. This cement is known by the trade names of cement Fondu in England and

Lumnite in America.

TYPES OF CEMENT:

Hydrophobic Cement:

This type of cement contains admixtures which decrease the wetting ability of cement grains.

The usual hydrophobic admixtures are acidol, napthenesoap, oxidized petroleum etc. When water is

added to hydrophobic cement, the absorption films are turn off the surface and they do not in any way,

prevent the normal hardening of cement. However, in initial stage, the gain in strength is less as

hydrophobic films on cement grains prevent the interaction with water. When hydrophobic cement is

used, the fine pores in concrete are uniformly distributed and thus the frost resistance and the water

resistance of such concrete are considerably increased.

Low heat cement:

The considerable heat is produced during the setting action of cement. In order to reduce the

amount of heat this type of cement is used. It contains lower percentage of dicalcium silicate C2 S of

about 46 % .

Pozzuolana Cement:

The pozzuolana is a volcanic powder. It is found in Italy near Vesuvius. It resembles surkhi which

is prepared by burning bricks made form ordinary soils. It can also be processed from Sholes and contain

types of clays. The percentage of pozzuolana material should be between 10 – 30.


33

Quick setting cement:

This cement is produced by adding a small percentage of aluminium sulphate and by finely

grinding the cement. The percentage of gypsum or retarded setting action is also greatly reduced.

The addition of aluminum sulphate and fineness of grinding are responsible for acceleration the setting

action of cement the setting action of cement starts within five minutes after addition of water and it

becomes hard like stone in less than 30 minutes or so.

Rapid hardening cement:

The initial and final setting times of this cement are the same as those of ordinary cement. But it

attains high strength in early days. It contains high percentage of tricalcium silicate C3 S to the extent of

about 56%.

Sulphate resisting cement:

In this cement, the percentage of tricalcium aluminate C3 A is kept below 5% and it results in the

increase in resisting power against sulphates. This cement is used for structures which are likely to be

damaged by severe alkaline conditions such as canal linings, Culverts, siphons etc.

Physical tests available for cement

Fineness:

The degree of fineness of cement is the measure of the mean size of the grain it. There are

three methods for testing fineness.

a. Sieve Method

b. Air permeability test

c. Sedimentation Method.

CONCRETE

Concrete may be defined as building material obtained by mixing cement, fine and coarse aggregates, and water in suitable proportions.

Constituents: Cement: Selection of particular type depends on specific conditions. Aggregates: Coarse aggregates: Aggregates pass through 75mm mesh. Eg: Stone, broken brick.


34

Fine aggregates: Aggregates pass through 4.75mm mesh. Eg: Sand. Water: Purpose of water:

1. To form the paste. 2. Enables the concrete mix to flow into moulds. 3.

Workability: Workability is defined as the ease with which it can be mixed, transported and placed. Wet concrete more workable than dry concrete. Batching: The measurement of materials for making concrete is known as Batching. Weight Batch -> cement. Weight Batch -> aggregates. MIXING: Mass becomes homogeneous and uniform. There are two types

1. Hand mixing. 2. Machine mixing. 3.

Transporting: Mortar pan, bucket and rope Belt conveyors are used.

Placing:

It should be placed in systematic manner to yield maximum result.

Compacting: It should be compared to eliminate air bubbles and obtain maximum density.

Curing: It should be wet at least for 7 days to promote continued hydration.

PURPOSE: 1. Increases durability. 2. Reduces shrinkage. 3. Increases wear resistance.

Types:

Plain Cement Concrete: It is mixture of cement, sand, crushed rock and water.

1. Free from corrosion. 2. High compressive strength. 3. It binds rapidly with steel.


35

R.C.C: Plains concrete strong in compression but weak in tension. To increase the tensile strength steel bars are embedded in concrete known as R.C.C.

Pre Stressed Concrete: Here high tensile steel wires are used instead of mild steel bars. There are two types:

1. Pre tensioning 2. Post tensioning.

Pre Tensioning:

� The wires are initially stressed and concrete is cost. Post tensioning:

� The wires are placing inside the concrete and then stressed. It saves the concrete and steel 50 to 80% compared with R.C.C.

Pre-cast concrete:

� It is manufactured in factory and transmitted to site. Advantages:

1. They are finished with accuracy. 2. High quality. 3. It is completed in short time. 4. It can be dismantled when required and they are suitable used else where.

Sl.no. Grade of concrete

Cement, sand, & aggregates

Characteristic Compressive Strength in

N/mm2

Uses

1. M10 1 : 3 : 6 10 Culverts 2. M15 1 : 2 : 4 15 Bridges

3. M20 1 : 1.5 : 3 20 Light loaded

columns

4. M25 1:1:2 25 Heavy loaded

columns

Factors that affect workability of concrete

a) Water content

b) Micro proportions

c) Size of aggregates

d) Shape of aggregates

e) Surface textures of aggregate


36

Preparation of concrete

To prepare concrete, following steps are to be followed

a) Batching

b) Mixing

c) Transporting

d) Placing

e) Compacting

f) Curing

Methods employed to transport concrete

Concrete can be moved from one place to another using

a) Mortar pan

b) Wheel barrow, handcart

c) Crane, bucket and rope way

d) Truck mixer and dumper

e) Belt conveyers

f) Chute

g) Skip and hoist

h) Transit mixer

Methods adopted for curing

Methods employed for curing of mortar or concrete are

(a) Water curing

(b) Membrane curing

(c) Application of heat

(d) Miscellaneous

Short notes on water curing.

This is by far the best method of curing as it satisfies all the requirements of curing mainly,

completion of hydration, elimination of shrinkage and absorption of heat of hydration. It is


37

pointed out that even if the membrane method is adopted, it is desirable that a certain extent of

water curing is done before the concrete is covered with membrane. Water curing can be done

in the following ways:

(a) Immersion

(b) Ponding

(c) Spraying or fogging

(d) Wet covering

Explain the slump test

Slump test is the most commonly used method of measuring consistency of concrete. It

can be employed either in laboratory or at work site. It is not a suitable method for very wet or

very dry concrete. However, it can be used to check quality of concrete and gives an indication of

the uniformity of concrete from batch to batch. Additional information on workability and quality

of concrete can be obtained by observing the manner in which concrete slumps. Quality of

concrete can also be further assessed by giving a few tappings or blows with tamping rod to the

base plate and observing the flow. The apparatus far conducting the slump test, essentially

consists of a metallic in the form of a function of a cone having the internal dimensions as under

Bottom diameter: 20cm

Top diameter: 10cm

Height: 30cm

The thickness of the metallic sheet for the mould should not be thinner than 1.6mm. The internal

surface of the mould is thoroughly cleared and freed from super flow moisture. The mould is then filled

in four layers, each approximately (1/4) of the height of the mould. Each layer in tamped 25 times by the

tamping rod taking care to distribute the strokes evenly over the grease section. After the layer has been

rodded, the concrete is struck off level with a trowel and tampering rod. The mould is re mould from the

concrete immediately by raising it slowly and carefully in a vertical direction. This allows the concrete to

subside. This subsidence is referred as SLUMP of concrete. The difference in level between the height

of the mould and that of the highest paint of the subsided concrete is measured. This difference in

height in mm, is taken as slump of concrete. The pattern of slump is shown in fig. It indicates the

characteristics of concrete in addition to the slump value. If the concrete slumps evenly it is called the


38

normal slump. It one half of the cone slides down, It is called shear slump. In case of a shear slump, the

slump value is measured as the difference in height between the height of the mould and the average

value of the subsidence. Shear slump also indicates that the concrete is non-cohesive and shows the

characteristic of segregation. Despite many limitations, the slump test is very useful on site to check

day-to-day as hour-to-hour variation in the quality of mix. An increase of the aggregates may mean for

instance that the moisture content of the aggregates has suddenly increased as there has been sudden

change in the grading of aggregate. The slump test gives warning to correct the causes for change of

slump value. Due to simplicity of the test it is popularly used to find workability of fresh concrete in spite

if that many workability tests are in vogue.

Bulking of sand

Increase in volume of sand due to moisture content is called bulking. Sand volume increases by

20% at a moisture content of 4% when compared to dry sand. Due to bulking of sand suitable

correction in quantity of sand should be made during volume batching of concrete.

Mixing process in concrete manufacture

Through mixing of the materials is essential for the production of uniform concrete mixing

should ensure that the mass becomes homogeneous, uniform in color and consistency. There are two

methods adopted for mixing concrete;

(1) Hand mixing

(2) Machine mixing

HAND MIXING:

Hand mixing is practiced for small scale unimportant concrete works. As the mixing can’t be

through and efficient, it is desirable to add 10% more cement to cater for the inferior concrete produced

by this method Hand mixing should be done over impervious concrete are brick floor of sufficiently

large size to take one bag of cement. Spread out the measure quantity of coarse aggregate and fine

aggregate in alternate layers. Pour the cement and the top of it, and mix them dry by shovel, turning the

mixer over and over again until uniformity of color is achieved. The uniform mixer is spread out in

thickness if above 20cm. Water is taken in a water can fitted with a sorehead and sprinkled over the

mixer and simultaneously turned over. This peration is continuing till such time a good uniform,


39

homogeneous concrete is obtained. It is of particular important to see that the water is not poured but it

is only sprinkled.

MACHINE MIXING:

Mixing of concrete is almost in variably carried out by machine, for reinforced concrete work and

for medium are large scale mass concrete works. Machine mixing is not only efficient, but also

economical; when the quantity of concrete to be produced is large many types of mixers are available

for using concrete. They can be classified as batch mixers and continuous mixers. Batch mixers

produced concrete, batch by batch with time interval, where as continuous mixers produce concrete

continuously without stoppage still such time the planet is working. In this material are feed

continuously by screw feeders and the ma trials are continuously mixer and continuously discharge.

This type of mixer is used in large works such as dams. Batch mixers may be of pan type or drum type.

Drum type may be further classified tilting.

STEEL

In case of steel there are only a limited standard structural sections like, I channel angle and the

designer can adopt. The aluminum offers limitless, possibilities of different shapes and profiles. The

designer enjoys full freedom in the matter of designing of a profile in such a way that the metal is

distributed exactly where it is needed for structural requirements whether proofing and mechanical

needs. In case of aluminum the infinite number of shapes and sections can be produced by the extrusion

process in continuous lengths.

Defects in steel

i) Cavities or blow-holes:

These are formed when gas confirmed or imprisoned in the molten mass of metal,

such confined gas presence of excess amount of phosphorous.

ii) Cold shortness:

The steel, having this defect, cracks when being worked in cold state .this effect is due to

the presence of excess amount of phosphorous.

iii) Red shortness:

The steel, having this defect, cracks when being worked in hot state. This defect is due to

the presence of excess amount of sulphur.


40

Give the market forms of steel

i) Angle sections

ii) Channel sections

iii) Corrugated sheets

iv) Expanded metal

v) Float bars.

N-tilting reversing are forced actual type.

Write short notes on annealing.

Te main object of this process is to make the steel soft so that it can be easily worked upon

with a machine .the annealing reduces the tensile strength .but it increases ductility and brings

back the steel to the best physical state to resist fracture under sudden stresses

What are the uses of the steel?

Depending upon the carbon cement concrete, the steel is designed as the mild steel or

medium carbon steel or high carbon steel .the various uses of steel are governened by the

amount of carbon contained in it. The carbon content of medium carbon steel is about .25 to

.60%...The high carbon is also known as the hard steel and its carbon cement varies from 0.60 to

1.10%

Market forms are available in steel:


41

Angle section

The angle sections may be of equal legs or the unequal legs as shown in figure There are two

angle sections

a. Equal angle section:

The equal angle sections available in size varying form 20 mm *20mm*3 mm to

200mm* 200mm*25 mm.the corresponding weights per meter length are respectively 9n

t0 736 N.

b. Unequal sections

The un-equal angle sections are available in sizes varying from 30 mm*20mm*3 mm to

200mm* 1500 mm*18 mm.the corresponding weights per meter length are respectively

11n and 469 n


42

Channel sections

A channel sections is designed by the height of the web and width of flange .these sections are

available in sizes varying from 100 mm* 45mm to 400 mm* 100mm .the corresponding weighs

perimeter length are respectively 58 N and 494 N.

Corrugated sheets

These are formed by passing of steel through grooves .these groove bend and press steel sheets

and corrugations are formed .on the sheets and corrugated sheets are usually galvanized and

they corrugated sheets are usually galvanized and they are referred to as the galvanized iron

sheets.

Expand metal

This form of steel is available in different shapes and size it is preferred from sheets of mild steel

which are making cuts and drawn out or expanded It is used for reinforcing concrete in

foundations roads floors, bridges etc.

Flat bars

These are available in suitable width varying from10mm to 400mm width thickness varying from

3 mm to 4omm.they are widely used in the construction of bars.

I-sections:

These are popularly known as the rolled steel joints beams. If consists of two flanges connected

buy a web as shown in this fig,. It is designated by overall depth, width of flange and weight

perimeter length.

Varying of sizes: 75m x 50mm at 61 N to 600mm x 210 mm at995N. Joist of size 300mm x 150mm

of 377N.The wide flange beams are available in sizes varying from 150mm x 100 mm 170N to 600

mm x 250m at 1451N.The beams suitable for columns are available in H- sections which vary in

size form in 150mm x150mm at 271N to 450mm x 250mm at 925N. The Bureau Indian standards

has classified the I-section into junior beams light beams medium beams, wide flange beams and

heavy beams and they are accordingly designated as

I.S.J.B.,I.S.L.B,I.S.M.B,I.S.W.B.,respectively. The R.S. joists are economical in materials and

they are suitable for floor beams, Intels, columns.etc.


43

Plates

The plate sections of steel are available in different sizes of thickness varying from 5mm to

50mm.The corresponding weights per square meter 392N and 3925N respectively.

i) To connect steel beams for extension of the length.

ii) To serve astensionance members of steel roof truss and

iii) To form built up sections.

Ribbed – Tor-steel bars:

These bars are produced from the ribbed to steel which is a deformed high strength. Steel each

bars is to be twisted individually and it is tested to confirm the standard requirements.

i) It is possible to bend these bars through 1800 without formation of any cracks for fractures on

their outside surface.

ii) It is possible to weld certain type of ribbed tor steel bars by electric flush sutt welding or arc

welding.

iii) They serve as a efficient and economical concrete reinforcement.

Round bar

These are available in circular cross sections with diameters varying from 5mm to 250mm they

are widely used as R.C.C and construction of steel work.

Square bars:

These are available in square cross section with sides varying from 5mm to 250mm they are

widely used in the construction of steel grill work for windows, gates etc.The commonly use

cross sections have sides varying from 5mm to 25mmm with corresponding weights peametre

length as 2N and 49N respectively.

T-sections:

The shape of this section is like that of letter and it is consists of flange and web. it is designed be

overall dimensions an thickness .this sections are available in sizes varying from 20 mm* 20 mm*

3 mm to 150 mm* 150 mm* 10 mm .The corresponding weights per meter length are 9 N and 228

N respectively. This section is widely used as members of the steel roof truss and from built-up

sections. In addition to eleven shapes, the rolled steel sections such as acute and obtuse angle


44

section rail sections, through sections and Z-sections .these sections are used to a limited extent

in the structures steel work.


45

surveying and civil engineering materials unit i basic...

Documents