Unit Ii Bmpt g6v5q

UNIT-II MASONRY Definition: Masonry may defined as the construction of a building units bonded together with mortar. Classification of masonry: There are three types of masonry they are as follows, 1. Brick masonry 2. Stone masonry 3. Composite masonry

Definition of used In masonry Following are some of the technical used in masonry work Arrises: The edge formed by the intersection of plane surfaces of brick are called the arrises. Bed : The lower surface of a brick or stone in each course. Course: A Course is a horizontal layer of masonry Bed t: The horizontal layer of mortar upon which the bricks or stones are laid is known as a bed t.

Elevation of a brick wall

Stretcher: A stretcher is the longer face of the brick (23cmX11.4cm) as seen in the elevation of the wall. A course of bricks in which all the bricks are laid as stretcher on facing is known as a stretcher course.

Header: it is the shorter face of the brick (11.4cm X 7.6cm) as seen in the elevation of the wall. A course of bricks in which all the bricks are laid as headers on facing is known as header course.

Elevation of a brick wall

Elevation of a brick wall Quions: the exterior angle or corner of a wall is known as quoin. The stones or bricks forming the quoins are known as stone quoins or quoin bricks.

Lap: the horizontal distance between the vertical ts in successive courses is termed lap.

Perpend: It is a imaginary vertical line which includes the vertical t separating two ading bricks. Racking back: it is a termination of a wall in a stepped fashion.

Toothing: it is the termination of the wall in such a fashion that each alternate course at the end projects in order to provide adequate bond if the wall is continued horizontally at a later stage.

Closer: A piece of brick which is used to close up the bond at the end of brick courses is known as a closer. Bat: It is the portion of the brick cut across the width. Thus, a bat is smaller in length than the full brick. Face: The surface of wall exposed to the weather is known as the facing.

Back: The inner surface of wall which is not exposed to the weather Backing: The material used in the formation of the back of the wall. Facing: The material used in the face of the wall. Hearting: The inner portion of the wall between the facing and backing

(i) Unburnt or Sun dried bricks- UN burn or sun dried with the help of heat received from sun after the process of moulding. These bricks can only be used in the constructions of temporary and cheap structures. Such bricks should not be used at places exposed to heavy rains.

(ii) Burnt Bricks- The bricks used in construction works bricks.

are burnt

First Class bricks: These bricks are table moulded and of standard shape. The surface and edges of the bricks are sharp, square, smooth and straight. All the qualities of good bricks and used for superior work of permanent nature. Second class bricks: These bricks are ground moulded and they are burnt in kilns. The surface of bricks is some what rough and shape is also slightly irregular. These bricks are commonly used at places where brick work is to be provided with a coat of plaster. Third class bricks: These bricks are ground moulded and they burnt in clamps. These bricks are not hard and they have rough surfaces with irregular and distorted edges. These bricks give dull sound when struck together. They are used for unimportant and temporary structures and at places where rainfall is not heavy. Fourth class bricks: These are over burnt bricks with irregular shape and dark colour. These bricks are used as aggregate for concrete in foundation, floors, roads,etc because of the fact that the over burnt bricks have compacted structure and hence, they are some times found stronger than even first class bricks

Qualities of Good Brick: (i) Bricks should be table moulded, well burnt in kilns, copper coloured, free from cracks and with sharp and square edges. (ii) Bricks should be uniform shape and should be of standard size. (iii) Bricks should give clear ringing sound when struck each other. (iv) Bricks when broken should show a bright homogeneous and compact structure free from voids. (v) Bricks should not absorb water more than 20 percent by weight for first class bricks and 22 percent by weight for second class bricks, when soaked in cold water for a period of 24 hours.

(vi) Bricks should be sufficiently hard no impression, should be left on brick surface, when it is scratched with finger nail. (vii) Bricks should be low thermal conductivity and they should be sound proof. (viii) Bricks should not break when dropped flat on hard ground from a height of about one meter. (ix) Bricks, when soaked in water for 24hours, should not show deposits of white salts when allowed to dry in shade. (x) No brick should have crushing strength below 55kg/cm2

Brick Load Bearing Construction

constituents of bricks 1. Silica-(50-60%) 2. Alumina (clay) – (20-30%) 3. Lime – (10%) 4. Iron oxide – (5-6%) 5. Magnesia- (<1%)

Types of Bricks Bricks used in masonry are of two types: 1. Traditional Bricks 2. Modular Bricks

Traditional Bricks • These are those which are not standardized in size. •The dimensions of traditional bricks vary from 20 to 25cm in length, 10

to 13cm in width and 5-7.6cm in thickness (height).

• The commonly adopted size of traditional brick is 23cm X 11.4cm X

7.6cm.

• The average weight of a brick will be about 3 to 3.5kg

Modular bricks •If bricks are large, it is difficult to burn them properly and they become too heavy to be placed with a single hand. • On the other hand if bricks are small, more quantity of mortar is

required. • Hence BIS has recommended the bricks of uniform size. Such bricks

are known as modular bricks. •Nominal size of these bricks are 20cm x 10cm x 10cm.

Special types of Bricks a) Squint Bricks These bricks are made in a variety of shapes and are used to the construction b) Bull Nosed Bricks: These bricks are used to form rounded quoins. c) Perforated Bricks These bricks may be standard size bricks produced with perforations running through their thickness.

d) Hallow Bricks: These bricks are made of clay and are provided with one or more cavities. e) Circular Bricks: These bricks have internal and external faces curved to meet the requirement of the particular curve and radius of the wall. d) Plinth cornice and String Course Brick: These bricks are moulded in several patterns with the object of adding architectural beauty to the structure.

Bonds in Brick work • A bond is an arrangement of layers of stones or bricks by which no

continuous vertical ts are formed.

• Bond is the interlacement of bricks, formed when they lay those

immediately below or above them.

• Bonds of various types are distinguished by their elevation or face

appearance

• It is essential to eliminate continuous vertical ts in the face of the

wall.

• The bond distribute the load coming on the structure evenly and

prevents the formation of a vertical crack

• A

wall having continuous vertical t does not act as a homogeneous mass to distribute the super imposed loads .

Types of Bonds Following are the types of bonds provided in brick work. 1. Stretcher bond 2. Header bond 3. English bond 4. Flemish bond 5. Facing bond 6. Dutch bond 7. Raking bond 8. Zigzag bond 9. English cross bond 10. Garden wall bond 11. Brick on edge bond

English bond 1. It consists of alternate courses of headers and stretchers 2. In this bond, vertical ts of the header courses come over each other, similarly the vertical ts of the stretcher courses also come over each other. 3. There is no continuous vertical t

4. Every alternate header comes centrally over the t between two stretchers in course below. 5. Queen closer is put next to the quoin header to develop the face lap. 6. In the stretcher course, the stretchers have a minimum lap of 1/4th their length over headers. 7. The hearting (middle portion) of each of the thicker walls consists entirely of headers.

8. Walls of even multiple of half bricks represent the same appearance on both faces. Thus a course showing stretchers on the front face will also show stretchers on the back face. 9. Wall of odd multiple of half bricks will show stretchers on one face and headers on the other face. 10. The queen closers are not required in stretcher courses.

Flemish bond 1. In this type of bond, each course is comprised of alternate headers and stretchers. 2. Every alternate course starts with a header at the corner (quoin header). 3. Quoin closers are placed next to the quoin header in alternate courses to develop the face lap. 4. Every header is centrally ed over the stretcher below it.

Flemish bonds are two types: 1. Single Flemish bond 2. Double Flemish bond Single Flemish bond Special features of single Flemish bond are 1. This bond is a combination of English and Flemish bond. 2. This bond uses the strength of the English bond and appearance of Flemish bond 3. In this work the facing of the wall consists of Flemish bond and the backing consists of English bond in each course. 4. It is used for those walls having thickness at least equal to one & half brick.

Double Flemish bond Special features of double Flemish bond are 1. Alternate headers and stretcher are laid in each course. 2. The facing and backing of the wall, in each course have the same appearance. 3. In walls having thickness equal to odd multiple of half bricks, half bats 4. For walls having thickness equal to even multiple of half bricks, no bats are required. A header or stretcher will come out as header or stretcher on the same course in front as well as back faces.

Mortar •Mortar acts as a cementing material and unites the individual brick units

together to act as a homogeneous mass. •Mortar is a homogeneous mixture produced by uniform mixing of a

binder with sand and water to make a paste of required consistency. Following are the types of mortar used in masonry 1. Mud mortar 2. Cement mortar 3. Lime mortar 4. Composite mortar

Reinforced Brick Masonry • Reinforced brick work is the one in

which the brick masonry is strengthened by the provision of mild steel flats, hoop iron, expanded mesh or bars. • This type of masonry is capable of

resisting compressive, tensile and shear stress. • The reinforcing material may be 1. Hoop

iron 2. Mild steel bars 3. Mild steel flats 4. Expanded mesh

The reinforcement can be laid either in horizontal or in vertical direction. Horizontal Reinforcement • Generally 2 strips of hoop iron are used per header brick and one hoop iron per stretcher brick. • Mild steel flat bars may have width between 22 to 32mm and thickness equal to 0.25 to1.6mm protection against rust is provided by dipping the bars in hot tar.

Vertical Reinforcement • it is in the form of mild steel bars is provided in brick columns, brick walls and brick retraining walls. Vertical mildsteel bars are then placed in the holes. • Brick

retaining walls are reinforced when the height is up to 3m since work is cheaper.

• The size of the groove is kept

slightly more than the diameter of the bar so that it may be grouted in with cement mortar, to prevent corrosion.

Reinforced brickwork is adopted in the following circumstances: 1. When the brickwork has to bear tensile or shear stresses. 2. When it is required to increase the longitudinal bond. 3. When the brickwork is ed on soil which is susceptible to large settlement. 4. When it is ed to act as a beam or lintel over openings. 5. When it has to resist lateral loads, such as in retaining walls 6. When it has to carry heavy compressive loads.

STONE MASONRY STONE: Stone has been defined as the natural, hard substance formed from earth crust which are part of rocks. ROCK: Rock may be defined as the aggregates of mineral constituents forming the earth’s crust

Uses of stones: The following are the uses of stones as follows. 1. Structure: Stones are used for foundations, walls, columns, lintels, arches, roofs, floors, damp proof course etc. 2.Face works: Stones are adopted to give massive appearance to the structure. Wall are of bricks and facing is done in stones of desired shades. This is known as composite masonry. 3. Paving stones: These are used to cover floor of building of various types such as residential, commercial, industrial etc. They are also adopted to form paving of roads, foot paths etc. 4. Basic material: Stones are disintegrated and converted to form a basic material for cement concrete, morum of roads, calcareous cements, artificial stones, hallow blocks etc. 5.Misalliances: Stones are also used for (i) ballast for railways (ii) flux in blast furnace (iii) Blocks in the construction of bridges, piers, abutments, retaining walls, light houses, dams etc.

Common Building stones Some of the common buildings stones are as follows • Granite (Igneous rock):

It is used for heavy engineering works for bridge piers, columns, retaining wall, foundation and Dam constructions. • Lime stone (Sedimentary):

It is used for the walls as coarse aggregate for concrete and also as a base material for cement.

• Sand stones (Sedimentary):

They are used for ornamental work and paving. • Laterite (Decomposed from

igneous rocks): It can occur in hard and soft varieties. The soft variety is used for paving the pathways. • Marble (Metamorphic rock):

It

is used for ornamental, flooring and stone facing slabs.

• Slate (Metamorphic rock):

It is used for damp proofing and flooring.

• Quartz (Metamorphic rock):

It is also used in the same way as granite but it is not used for ornamental work as it is brittle.

• Gneiss (Metamorphic rock):

It is used in the same way as granite. It can be identified by its elongated plates minerals often mixed with mica.

• Basalt (Igneous rock):

They have the same use as granite and also commonly used in railway track.

Properties of common building stones A good building stone should have the following qualities. • For face work:

It should have fine, compact texture; light-coloured stone is preferred as dark colors are likely to fade out in due course of time. • Structure:

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. • 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 light stones may be the choice. • Hardness:

This property is important for floors, pavements, aprons of bridges, etc. • 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 freezes, expands, and causes cracking.

• Seasoning:

The stone should be well 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. • Fire resistant:

Stones should be free from calcium carbonate, oxides of iron, and minerals having different coefficients of thermal expansion. • Specific gravity:

The specific gravity of most of the stones lies between 2.3 to 2.5.

Classification of Stone Masonry

Rubble Masonry • In this type of construction, the

stones of irregular size are used. • The stones are obtained from quarry are taken in use in the same form or they are broken and shaped in suitable sizes by means of hammer as the work proceeds. • Since stones of irregular size are used, the masonry will have wide ts.

Coursed rubble masonry • In this heights of stones vary from 50mm to 200mm.

• The masonry work is carried out

in courses such that the stones in a particular course are of equal heights.

• This type of masonry is used for

the construction for public buildings, residential buildings etc.

Uncoursed rubble masonry • This is the poorest form of stone masonry. Since it is cheaper it is used for the construction of compound walls, godowns, garages, labour quarters etc. • The stones to be used for the

work are directly obtained from the quarry. • The larger stones are laid first

and the spaces between them are then filled up by means of spalls or snecks. • The thickness of ts should

not exceed 13mm

Random rubble masonry • This form is slightly superior to uncourse rubble masonry. • In this type of masonry, the stones of irregular sizes and shapes are used. • More skill is required to make this masonry structurally stable. • If the face stones are hammer dressed and the thickness of mortar ts are hammer dresses and the thickness of mortar ts does not exceed 12mm. • This type of masonry used for the construction of residential buildings, compound walls, godowns etc.

Ashlar Masonry • The work built from carefully dressed stones with accurate bedding

and ting is termed as ashlar masonry • In this type of construction, the square or rectangular blocks of stones

are used. • The courses are not necessary of the same height. • The height of stones varies from 250mm to 300mm. • The length of stones should not exceed 3 times the height and the

depth into the wall should be at least equal to half the height.

Ashlar fine masonry • All the stones are fine tooled on all beds and sides ts. • The height of the course is never less than 30cm • All courses are kept of same height. • The height of stones used is never less than their breadth and their length not less than twice their height. • The face stones are generally laid as header and stretcher alternately. • The thickness of the mortar ts should not exceed 3mm. • It gives perfectly smooth appearance but it is costly in construction.

Ashlar Rough Tooled • The exposed faces of stone

generally have a fine dressed chisel drafting all round the edges. But he face is made rough by means of tools.

• The thickness of mortar ts

does not exceed 6mm.

• A strip about 25mm wide and

made by means of a chisel is provided around the perimeter of every stone.

Ashlar rock or quarry faced masonry • It is similar to ashlar rough

tooled except that the exposed faces of face stones between the chisel drafting are left rough.

• Only the projections on the face,

known as the bushings, exceeding 80mm are removed by a hammer. It gives massive appearance.

Ashlar chamfered masonry •

Here the strip is provided as above. But is chamfered at an angle of 45o.

• It is similar to Ashlar or quarry

faced masonry. A neat appearance of the grooved ts is obtained.

Ashlar block in course masonry • It occupies an intermediate position between ruble masonry and the ashlar masonry. • The faces of the stones are

generally hammer dressed and the thickness of mortar ts does not exceed 6mm. • The depth of courses varies

from 200mm to 300mm. • It is used for heavy engineering

works such as retaining walls etc.

Ashlar facing • it

is provided with brick or concrete block masonry to give better appearance.

• The sides and beds of each

block are properly dressed so s to make them true to shape. • The

exposed faces of the stones are rough tooled and chamfered.The backing of wall may be made in brick masonry.