BOARD EXAMINATION, OCTOBER-2019

CONSTRUCTION MATERIALS AND

CONSTRUCTION PRACTICE

II YEAR – III SEMESTER

ANSWER KEY

QUESTION PAPER CODE- 231

Prepared by Mr.S.Rajkumar, lecturer /civil

228, Arasan Ganesan polytechnic college, Sivakasi

231

October 2019 – Board Examination Answer Key

Construction Materials and Construction Practice

PART – A (5 x 2 = 10)

1.

Name any two natural stones. (any 2 x 1 = 2)

i) Cuddappa slab ii) Kota stone iii) Sandstones

2.

iv) Shahabad stone v) Granite vi) Marble

Mention any two metals used in building construction. (any 2 x 1 = 2)

i) Cast iron ii) Steel iii) Aluminium

3.

iv) Galvanized iron v) Stainless steel

Write two materials used for da mp proofing. (any 2 x 1 = 2)

i) Bitumen ii) Mastic asphalt iii) Bituminous felt

iv) Mortar v) Cement concrete vi) Stones

vii) Bricks viii) Metal sheets

4. Define substructure and superstructure.

Substructure: (1 mark)

The substructure is that part of the structure which is in direct contact with the ground

and transfers the load of the structure to the soil is called Substructure.

Super structure: (1 mark)

The part of a building or structure which is above the ground level or above the

foundation is called super structure.

5. Define partition wall.

A partition may be defined as a wall or division or screen provided for the purpose of dividing

one room into a number of small apartments. Usually they are designed as non load bearing

walls.

6. What is under pinning?

The placing of new foundation below an existing foundation or the process of

strengthening the existing foundation is known as underpinning of foundation.

7. Name any two types of pointing. (any 2 x 1 = 2)

i) Flush pointing ii) Recessed pointing iii) Weathered pointing

iv) Keyed pointing v) Rubbed pointing vi) Vee pointing vii)

Struck pointing viii) Beaded pointing

8. What is meant by stair?

It is a structure having series of steps and affords the means of ascent and descent

between the floors or landings.

PART – B (5 x 3 = 15)

9. Name any two types of cement and explain any one of them.

Types of cement: (any 2 x 1 = 2)

1) Acid resisting cement 2) Blast furnace cement 3) Coloured cement

4) Expanding cement 5) High alumina cement 6) Hydrophobic cement 7)

Low heat cement 8) Pozzolana cement 9) Quick setting cement

10) Rapid hardening cement 11) Sulphate resisting cement 12) White cement.

Acid resisting cement: (any 1 x 1 = 1)

In this acid resisting cement, aggregate such as quartz, quartzites etc. are used. It is

used for acid-resistant and heat resistant coatings of installation of chemical industry.

Blast furnace cement:

For this cement, slag as obtained from blast furnace is used. Its strength in early days

is less, hence it requires longer curing period. It proves to be economical as slag which is a

waste product is used in its manufacture.

Pozzolana cement:

Pozzolana is a volcanic powder. It is cheap, attains compressive strength with age,

offers great resistance to expansion and possesses lighter tensile strength. It is used to

prepare mass concrete of lean mix works and for laying concrete under water.

White cement:

This is just a variety of ordinary cement and it is prepared from such raw materials

which are practically free from colouring oxides of iron manganese or chromium. It is white

in colour and it is used for floor finish, plaster work, ornamental work etc. It should be

stored in closed container. It is more costly than ordinary cement.

10. What are the functions of paint? (any 3 x 1 = 3)

It should have good body, i.e. high connecting power.

It should have good fluidity to spread evenly in a thin coat with the brush.

It should dry fairly quickly and appear uniform.

It should not show brush marks when dry.

It should not crack in drying.

The colour should not fade or change under atmospheric actions.

It should be rough and durable.

11. Distinguish thermoplastics and thermosetting plastics. ( 3 x 1 = 3)

Thermoplastics Thermosetting plastics

Shape can be altered by heating that object Shape cannot be altered by heating that object

Can be bent easily Cannot be bent easily

That are soft and weak That are hard and strong

12. What are the requirements of good foundation? (any 3 x 1 = 3)

i) The foundation should be stable or safe against any possible failure.

ii) The bearing pressure of the foundation should be within in the allowable soil pressure.

iii) The settlement of the foundation should be within reasonable limits. iv) The

differential settlement is so limited as not to cause any damage to the structure.

13. State the conditions to be followed in locating doors and windows. (any 3 x 1 = 3)

i) Door should preferable be located near the corner of the room.

ii) Doors and windows should be located in such a way as to cause least disturbance to

privacy and internal decoration. iii) The sill of a window opening should be

preferably be located at a height of 80 cm from the inside floor level.

iv) Doors and windows should be so located that light and ventilation are evenly distributed

and provides necessary privacy.

14. Write about form work for column. (3)

This formwork consists of a box prepared from four separate sides. The sides ae held

in position by wooden blocks, bolts and yokes. The boxes are designed in such a way that

with little alternatives, they can be used for columns with smaller cross sections on upper

floors.

The formwork for circular columns is made of narrow vertical boards. These are

known as staves and are correctly shaped to the required curvature. The staves in turn are

fixed to yokes which are also suitably curved.

15. Write a note on stucco plastering (3)

Stucco plastering is a decorative plaster used on both interior and exterior walls. The

stucco-plastered surface finish resembles a marble finish. This plaster is laid in three coats

with a total thickness of 25mm.

The first coat, known as a ‘Scratch’ or rough cpat, functions to bond with the wall and

provides strength.

The second coat known as ‘finer or brown coat’ provides desired shape to the surface

The third coat called ‘final or finishing coat’ affords the required texture smoothness

and decorative appearance to the plastered surface.

16. What are the requirements of good partition wall? (any 3 x 1 = 3)

i) The partition wall should be strong enough to carry its over load.

ii) The partition wall should have the capacity to support suitable decorative surface. iii)

A partition wall should be stable and strong enough to support some wall fixtures,

wash-basin etc.

iv) A partition wall should be as light as possible.

v) A partition wall should be as thin as possible.

vi) A partition wall should act as a sound barrier, especially when it divides two rooms.

vii) A partition wall should be fire resistant.

PART – C

17. A) What are the requirements of good building stone? (any 10 x 1 = 10)

The desirable quality depends on the use of the stone.

Following are the requirements:

The stones should be strong, hardy and durable to withstand the deteriorating action of rough

weather.

Appearance of stones is very important while used for decorative works and facing works

of buildings. They should be capable of preserving their colour uniformly for a long time.

When used in exposed conditions the stones should remain unaffected due to alternate

conditions overheat and cold, and dryness, chemical agencies and grd~ of trees and creepers

in joints.

The stones should facilitate easy dressing, calving moulding and cutting.

The grains should be well cemented and sharp.

Hardness co-efficient > 17 is considered good and can be used for roadwork and < 17 is of

poor quality.

Specific gravity should be > 2.7 and crushing strength greater than l000 kg/cm2.

The stone should have a pleasing structure and should be free from cracks.

It should be well seasoned for a period of about 6 to 12 months before used in structural

work.

It should be fire resistant in such a way that the shape is preserved when a fire occurs.

The stone should not absorb more than 5% of its weight of water.

17. B) Explain the types of glasses used in buildings. (2)

i) Sheet glass ii) Plate glass iii) Float glass iv) Wired glass

v) Translucent glass vi) Glass blocks vii) laminated safety glass viii)

Colored glass ix) Tinted glass x) Bullet proof glass

i) Sheet glass: (any 4 x 2 = 8)

This is used in small panels of doors and windows for building purposes. They should

be clear, free from blisters, scratches, waves, bubbles etc. It is available in thickness of 2 mm,

2.5mm, 3 mm, 4mm, 5mm, 5.5mm and 6.5mm.

ii) Plate glass:

This type of glass is stronger and more transparent with much less wariness than sheet

glass. It is to be used for large size panels such as shop windows, manufactured in thick of 3 to

32 mm.

iii) Float glass:

This type of glass is prepared by passing the molten glass from the furnace through a

molten tin bath. This glass is of uniform thickness with excellent optical clarity and aesthetic

appearance.

iv) Wired glass:

It is the type of glass in which wire setting is embedded in plate glass during rolling.

This type of glass resists fire much better. Often this type of glass is used for skylights.

v) Translucent glass:

In this glass a pattern or texture is imprinted on one or both faces so that images

cannot be seen through. This glass is used in doors and windows for bedrooms, lavatories,

bathrooms etc.

vi) Glass block:

These are transparent or translucent glass units produced by a pressing process in

which firstly two hollow dishes are formed which are then fused together to form a hollow.

vii) Laminated safety glass:

This type of glass is produced by bonding together two or more pieces of glass with

plastic inter layers. If broken, the glass adheres to the inner layer, thus reducing the risk of

injury to people such type of glass is used in automobiles for windows and windshields.

viii) Colored glass:

These are special glasses made for the facing portion of buildings. They are usually

colored or mirrored in order to shade direct sunlight are the heat- resistant.

ix) Tinted glass:

This is also a glass with color. It comes in three shades bronze, dark grey and auto

green. The thickness ranges from 2 to 12mm.

x) Bullet proof glass:

This is prepared by special techniques and will be up to 200 mm in thickness.

18. A) Explain the defects in timber with neat sketches.

Defects in timber: (any 6 x 1 = 6)

1. Knots

These are the bases of branches or limbs which are broken or cut off from the tree. The

portion from which the branch is removed receives nourishment from the stem for a pretty long

time and it ultimately results in the formation of dark hard rings which are known as knots. As

continuity of wood fibre is broken by knots, they form a source of weakness.

2. Ring galls

Ring galls are due to wrong cut of a tree. Hence peculiar curved swellings found on the

body of a tree are known as ring galls. They develop at a point from where branches are

improperly cut and removed.

3. Shakes

These are cracks which partly or completely separate lithe fibres of wood. Following

are the different varieties of shakes.

4. Cup shakes

These are caused by the rupture of tissues in circular direction. It is a curved crack and

it separates partly one annual ring from the other. It developes due to non-uniform growth. It

may not prove to be harmful if it covers only a portion of ring.

5. Heart shakes

These cracks occur in the centre of cross - section of tree and they extend from pith to

sap wood in the direction of metallurgy rays. These cracks occur due to shrinkage of interior

part of tree which is approaching maturity. Heart- shakes divide the tree cross - section into two

to four parts.

6. Ring shakes

When cup shakes cover the entire ring they are known as ring shakes.

7. Star shakes

These are cracks which extend from back towards the sap wood. They are usually

confined -upto the plane of sap wood. They are wider-on the outside ends and narrower on the

inside ends. They are usually formed due to extreme heat or frost.

8. Radial shakes

These are similar to star shakes. But they are fine irregular and numerous. They usually

occur when tree i exposed to sun for seasoning after being fell down. The run for a short distance

from bark towards the centre, the follow direction of annual ring and ultimately run toward pith.

9. Twisted fibers

These are also known as wandering hearts and they are cause by twisting of young trees

by fast blowing wind. The fibres are twisted in one direction as shown in fig.2.7. Such timber

is unsuitable for-sawing, but can be used for posts and poles in unsawn condition.

10. Upsets or rupture

This is caused due to an injury during the growth of the tree due to strong winds or bad

felling of trees resulting-in discontinuity of fibres.

11. Wind cracks

If wood is exposed to atmospheric agencies, interior surface shrinks. Such a shrinkage

results in cracks as shown in fig.2.9.

12. Water strain

This is discoloring of wood when coming into contract with water and is usually found

in converted timber.

13. Burls

These are formed as irregular projections on the body of timber due to an injury or

shock receded by the tree at-its young age.

14. Callus

These are soft tissues covering the wound of a tree.

15. Course grain

If a tree grows rapidly, annual rings are widened and such timber possess less strength.

16. Dead wood

These are timbers obtained from dead standing trees. It is indicated by light weight and

reddish colour.

17. Droxiness

This defect is indicated by white decayed spots which are concealed by healthy wood.

These are formed by the access of -fungi.

18. Foxiness

This defect is indicated by white, red, yellow ring in wood, It is caused either due to

poor ventilation during storage, or by commencement of decay to over maturity.

(Drawing - 4)

18.B (i) Explain any two types of concrete.

i) Lime Concrete ii) Cement concrete iii) Light weight concrete (1)

i) Lime Concrete: (Any 2 x 2 =4)

The concrete consisting of lime, a fine aggregate and a coarse aggregate mixed in a suitable

proportion in addition to water is called lime concrete.

In this type of concrete, hydraulic lime is generally used as a binding material, sand, surkhi

and cinder are used as fine aggregate and broken bricks, broken stones etc. as coarse aggregates. This

concrete has less strength but is cheaper than cement concrete.

ii.Cement concrete:

This concrete constitutes of cement, fine aggregate, coarse aggregate and water mixed

together in the right proportion. The usual proportions are one part of Portland cement, 5 to 8 parts clean

sand, 3 to 16 parts coarse aggregate.

iii.Light weight concrete:

This concrete is generally made from light weight aggregate like expanded shale,

foamed slag, brick bat etc. these aggregates can also be prepared artificially from special clays which

when heated to 1000 – 12000 bloats or expands and becomes light in weight. They are used as filling

concrete in bathrooms, terraces etc. and as a thermal insulation.

18.B (ii) What are the characteristics of good varnish? (5x 1 =5) i) They should dry rapidly.

ii) Should form a hard, tough and durable film iii)

Should retain color and give good gloss.

iv)should possess resistance to weathering and

v)should be uniform and pleasing when dry and should not shrink or show cracks.

19. A) What are the points to be considered in the construction of brick masonry?

Points to be considered in the construction of brick masonry: (any 10 x 1 = 10)

The bricks to be used should confirm to the requirement of the specification of work.

The brick work should comply with requirements of the specification for the work.

The mortar to be used for the work should be of quality and of proportions as specified.

The bricks should be immersed in water before placed in its position so as to prevent absorption

of Moisture from the mortar.

The bricks should be properly laid with the frog printing upward.

The brick work should be carried out in proper bond.

As far as possible the brick work should be raised uniformly.

In brick work, brick bats should not be used except as closers.

Single scaffolding should be adopted to carry out the brick work at a higher level. Required

headers are taken out to create supports for the scaffolding and they should be inserted when

the scaffolding is removed.

The brick work should be carried out as per line and level. The vertical face should be checked

by means of a plumb lob and the inclined surfaces if any should be checked by means of wooden

templates.

After construction the brick work should be well watered for period of 2 to 3 weeks if L.M. is

used and for about 1 to 2 weeks if cement mortar is used.

19.B) Explain the types of rubble stone masonry with neat sketches.

Rubble masonry: (1)

1. Coursed rubble masonry

2. Uncoursed rubble masonry

3. Random rubble masonry

Rubble Masonry:

The stone as obtained from the quarry is used without dressing for the construction of masonry

is called rubble masonry. The excess projection of stones may be removed with the help of hammers

before using in the masonry.

1. Coursed rubble masonry: (3 x 2 = 6)

In this type of rubble masonry, the height of stones varies from 50 mm to 20 cm. The stones

are sorted out before the work starts.

The masonry work is then carried out in courses such that stones in a particular course are of

equal heights. This type of masonry is used for the construction of public buildings, residential buildings

etc.

2. Uncoursed rubble masonry:

In this type of rubble masonry the stones are not dressed: But they are used as they are available

from the quarry, except breaking some corners. The courses are not maintained regularly. The larger

stones are laid first and the spaces between them are then filled up by means of spells. The wall is

brought to a level every 30 cm to 50 cm. This type of rubble masonry being cheaper is used for the

construction of compound walls, godowns, garages, labour quarters etc.

3. Random rubble masonry:

The stones- of irregular sizes and shapes are used for the construction of masonry. The stones

are arranged so as to have a good appearance. More skill is required to make this masonry structurally

stable. The face stones are chisel dressed and the mortar joints does not exceed 6 mm to 12 mm. This

type of masonry is used for the construction of residential buildings, compound walls etc.

(Drawing – 3)

20. A) Explain the types of stairs with sketches.

TYPES OF STAIRS:

1. Based on the materials used (1)

a) Brick stairs b) R.C.C. stairs c) Stone stairs

d) Timber (or) wooden stairs

2. Based on the Shape of the stair

e) Steel stairs

a) Straight stairs b) Dog legged stairs

c) Open well stairs d) Bifurcated stairs

e) Spiral stairs f) Geometric stairs

g) Circular stairs h) Quarter turn stairs

a) Straight stairs: (any 3 x 2 =6)

A straight stair is one in which all the steps are parallel to one another and lead in the same

direction. So that a person ascending moves forward in a straight line. A straight stair will normally

consist of a single flight only. A plan and section of a straight stair is shown.

b) Dog legged stair:

It consists of two successive straight flights of steps in opposite direction. A level landing is placed

across the two flights at the change of direction. This type of stair is useful where the width of stair case

is first sufficient to accommodate two widths of stair.

c) Open well stair

In this type of stair, there is a well or opening between the flights in plan. This well may be

rectangular or of any geometrical shape. These stairs are useful where available space for stair case has

a width greater that twice the width of fights.

d) Bifurcated stair

This type of stair is very common in public buildings in which it appears as a prominent

feature. In this type of stairs, the bottom flight is divided at a landing into two flight as shown in plan.

The plan and elevation of a bifurcated stairs are shown in figure.

e) Spiral stair

These stairs are generally provided at the rear of a building to give access for servicing at

various floor. All the steps radiate from central newel post in the form of winders. It may be constructed

in stone, cast iron or R.C.C.

20.B) What are the points to be considered while selecting a type of flooring?

The following points are to be considered while selecting a type of flooring (2)

a) Appearance b) Cleaning c) Comfort d) Cost

e) Durability f) Noise g) Slipperiness h) Fire resistant

a) Appearance: (any 4 x 2 = 8)

The flooring material should be of desired appearance and it should produce the

colour effect in conformity with the use of building. Materials like terrazzo, marble,

mosaic and tile give good appearance.

b) Cleaning :

The flooring material should be such that it can be easily and effectively cleaned. c)

Comfort:

The flooring material should be such that it gives comfort when used. d)

Cost:

The cost of flooring material should be reasonable as compared to the utility of the

building.

e) Durability:

The flooring material should be durable and it should be strong enough to impart

resistance to wear, tear, chemical action etc.

f) Noise:

Floorings should insulate noise and it should not produce noise when users walk on it.

Floor covering of wood, rubber, cork, P.V.C. tiles are suitable for this type. g)

Slipperiness:

Flooring material should be smooth and should have an even surface. It should not be

slippery.

h) Fire resistant:

This quality is more important for upper floors. The material should offer sufficient fire

resistance so that fire barriers are obtained between different levels of a building.

Concrete, tiles, terrazzo, mosaic and marble have this quality.

21.a) (i) Briefly describe the defects in plastering. (any 5 x 1 =5)

i) Blistering of plastered surface:

Small patches swell out beyond the plane of the plastered surface and this defect is

particularly seen in case of plastered surface inside the building. ii) Cracks:

These are formed on the plastered surface and may be hair cracks which may be easily

seen. The development of fine hair cracks is known as crazing.

iii) Efflorescence:

This is a growth of a whitish crystalline substance which appear due to the presence

of insoluble salts, present in materials like brick, sand, cement, water etc., when the wall dries

out. iv) Flaking:

The formation of a very small loose mass on the plastered surface is known as flaking

and it is mainly due to bond failure between successive coats of plaster.

v) Peeling:

A portion of plaster coming off the surface due to insufficient bonding is peeling. vi)

Popping:

Sometimes the plaster mix contains particles which expand on being set. A conical

hole in plastered surface is formed in front of the particle. This conical hole is known

as blow or pop.

vii) Rust-stains:

These are sometimes seen on the plastered surface, especially when plaster is applied

on metal lath.

viii) Softness:

The excessive dampness at certain points on the plastered surface makes that portion

soft. The chief reasons for such softness are undue thinness of the finishing coat, presence of

salts etc. ix) Uneven surface:

This defect becomes prominent only due to poor workmanship of the work.

21. A.(ii) Explain the preparation of surface for white washing. (5)

Preparation of surface:

The wall surface is thoroughly cleaned, brushed and rendered free of from mortar

droppings and other foreign matter. If the surface is smooth it is rubbed with sand-paper to

ensure proper adhesion of white wash.

In case of rewhite washing all loose materials and scales are scrapped off by steel wire

brushes or steel scrappers. The loose white-wash is removed with sand paper and the holes are

filled with lime putty. The greasy spots should be given a coat of a mixture of rice water and

sand so that the wash may stick to the surface. In places like kitchens where the places have

been discoloured by smoke or other reasons the surfaces should given a coat of a mixture of

wood-ash in water before applying white wash.

21.B) Explain the types of scaffolding.

i) Single scaffolding or brick layer’s scaffolding

(1)

ii) Double scaffolding or mason’s scaffolding iii)Steel

scaffolding

i) Single scaffolding or brick layer’s scaffolding (3)

This being cheap is most commonly used in the construction of brick work.

In this type, most of the members except platforms are usually made of bamboos and poles.

It consists of a single row of standards which are driven in to the ground at a distance of about 1.5 to

2.0 m apart and about 1.2 m away from the wall to be constructed. Where It is difficult to fix the

standards in the ground, they may be filled in tubs or barrels filled with sand or earth so as to be

strong enough against any movement or slipping. The standards are then connected to each by ledgers

placed at right angle and spaced at a vertical distance of about 1.2 to 1.5 m. They are secured in

position by rope lashings. The put lays are placed at a horizontal spacing of about 1.2 to 1.5 m such

that their one end is supported on the ledgers and the other end is held in the holes provided in the

wall.

ii) Double scaffolding or mason’s scaffolding (3)

This type of scaffolding is stronger than the single scaffolding and is used in the

construction of stone work. The frame work is similar to the single scaffolding except two rows of

standards are used, one row close to the wall within 15 cm of the wall face and the other at 1.2 to

1.5m away from the face of the wall. The putlogs are supported on both ends on ledgers. This type

of scaffolding is completely independent of the wall and no holes are made to support the put logs.