UNIT-1 Reinforced Brickwork

8/10/2019 UNIT-1 Reinforced Brickwork

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SCAFFOLDING

When the height above floor level becomes more than 1.50 m, temporary erection is needed to

support a number of platforms at different levels for the convenience of workers. Scaffold enables

the mason to work at various stages of a building and to lift the materials for their immediate use at

different heights.

Terms used in Scaffolding

1. Standard. Vertical member is known as standard.

. !edgers. "he hori#ontal member parallel to the wall is called

$. %utlog. &t is the transverse piece which is placed on the ledgers and which supported on the wall

at one end. &t is at right angles to the wall.

'. "hansom. &t is putlog supported on ledgers at their both ends.

5. (race. &t is diagonal or cross piece fi)ed on the standards.

*. +uard ail. &t is a rail fi)ed like a ledger at the working level.

-. (ridle. &t is a piece which is used to cover an opening in a wall and it provides support to one

end of the putlog at the opening.

. "oe (oard. &t is a board fi)ed parallel to ledgers and supported between the putlog &t is given asa protective measure on the working platform.

/. aker. n obli ue support is known as raker.

"ypes of Scaffolds. "he following are various types of scaffolds commonly used2

1. Single scaffold or bricklayers scaffold. '. Suspended scaffold.

. 3ouble scaffold or mason4s scaffold. 5. "restle scaffold.

$. antilever scaffold.*. Steel scaffold.

Single Scaffold.

&t is very common type of scaffolding used widely in the construction of brick work. &t consists of

vertical members firmly in grounds at .5 to $.0 m apart. "hese standards are connected to each

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other by ledgers at every rise at 1.$ to 1.* m. "hey are provided on the building side of the

standards and are fi)ed in position by rope lashings. %utlogs are lashed on the ledgers at one end

and into the holes into the wall at the other end. %utlogs are 1 m in length and are placed 1. m

apart. "hey are provided to support the working platform. &n very high scaffolding cross braces are

employed to stiffen the structure

Double Scaffold.

"his type of scaffold is more stronger than the single scaffold. Since it is difficult to leave holes in

the stone masonry to provide bearing for the putlogs, in double scaffold two frames of standards,

ledgers and braces are used. 6ne is placed close to the wall and the other at a distance of about 1.5

m from the first. 7ence the double scaffold is completely independent of the wall.

Reinforced Brick ork (rick masonry is weak in tension and cannot carry appreciable amount of tensile stresses. "hough

reinforced cement concrete is a versatile material for use in all types of constructions, but it is very

costly material, hence it cannot be recommended for smaller works such as lintels, slabs, beams,

etc. Steel reinforcement is provided in between the mortar 8oints of the brick masonry. einforced

brick work can take up tensile and shear stresses upto reasonable amount. 9ollowing are the

advantages of reinforced brickwork construction2

:a; &t is cheap, strong and durable.

:b; &t is fire


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T!"ical cons#ruc#ions in reinforced brick ork

:1; Walls. einforcement in wall may be provided either in the form of e)panded metal mesh or

s&eei bars. =any types of patented e)panded metal meshes are available in different widths and

different gauges in the market. =ortar is evenly placed on the re uired course of the brickwork and

the steel fabric is stretched flat on it and pressed uniformly. "he ne)t course of bricks is further

built over it.

"he flat steel bars of section 5mm. ) mm. known as hoop iron are also used to reinforce the

walls. "hey are hooked at corners and 8unctions as shown in 9ig. 1.-/. "he hoop iron is dipped in

hot tar and immediately sanded to increase the resistance against rusting. Special bricks are used to

provide vertical reinforcement in walls :as illustrated

: ; olumns. Special t of bricks is used for the construction of reinforced columns. Vertical

reinforcing bars are placed between these bricks. "he steel plates of about * mm. thickness are

provided at every fourth course and the steel bars are fi)ed in the foundation concrete block.

:$; !intels. Steel bars of * to 1 mm. diameters are provided longitudinally in between thevertical, 8oints of brick lintels. lb take up the vertical shear, * mm. diameter steel stirrups are used

at suitable intervals.

:'; Slabs. 9or laying reinforced brickwork slabs, the centering is erected at the re uired level.

+enerally, a platform of wooden planks supported on beams and posts is used for this purpose. &t is

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covered with well beaten earth and fine sand is sprinkled over it. Slabs of definite depths such as

10, 0, $0, '0 cm. etc. can only be constructed. "he reinforcements are placed as per specifications

and bricks are laid to fill up the spaces. >oints are filled up with mortar in such a way that

reinforcement is fully embedded in mortar. "he slab is properly cured for to ' weeks. "he

centering is removed only after days and the surfaces of the slabs are smoothened.

:5; (eams. einforced beams are constructed inlhe same way as (. slabs. &n case of (. beams

steel bars upto 5 mm. diameter are used as reinforcement.

$ain#enance of Brick ork

:1; leaning. (rick masonry may be cleaned with steam or hot water 8ets. "his is useful for fihe

te)tured and hard burnt bricks. Sand blasting is also used for cleaning brickwork but it spoils the

te)ture of the bricks as well as damages the pointing done in the brickwork.

: ; emoval of ?fflorescence. =agnesium, sulphate, calcium sulphate, sodium and potassium

sulphate etc., being soluble in water are deposited on the brickwork surface as efflorescence as a

result of alternate drying and wetting of the brickwork by rain and sun by rise and fall of ground

water table. &n fact, salts come in the brickwork along with water from below and are deposited on

the brickwork in layer after evaporation. Since moisture movement is one of the causes for efflo

rescence, it can be reduced to a great e)tent by suitable damp preven tion of the building.

?fflorescence is removed by scrubbing the wall with water and hard steel brush. 10@ solution of

muriatic acid is also used sometimes instead of ordinary water. "he wall is washed with pure water

im mediately after this treatment.

:$; epointing old brickwork. 6ld pointings get damaged due to wind, rain, heat, free#ing and

other weathering agencies. epointing is done to improve the appearance of an old brickwork. &t is

done as follows2

:a; "he old mortar is removed from 8oints to a depth of at least $ mm. "he old mortar is loosened

with small hammer and removed out with steel brush to make the surface clean.

:b; Water is sprinkled over the 8oints and the new mortar is put with the trowel. &t is finally finished

with the pointing tool to give the desired shape.

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:c; %roper curing is done for to $ weeks.

:'; epainting. epainting is re uired for the surfaces which were earlier painted and have been

damaged by weathering agencies. "he old paint is removed by hard steel brush and water or steam.

"hen the new paint is applied in the desired colour and tint.

Defec#s in Brick ork

Follo ing are #%e common defec#s #%a# occur in brick ork&

:a; Ase of weaker materials. Ase of weaker materials forn small depressions with nodules of

friable materials at the 8oints. creates e)pansion and cracking in brickwork.

:b; Sulphate in mortars. Sulphate attacks the mortar causii e)pansion of mortar 8oints and finallyresulting in cracking of bric work, spalling of brick edges, and damage of mortar. "he failure is di

to chemical reaction between sulphates present in bricks and ti aluminium ingredients of portland

cement and it is accelerated in ti presence of moisture. (ricks free from suiphates should be used ai

proper damp


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t; 9rost action. "he volume of water is increased when it is fro#en. 3ue to this phenomena, the

cracks are caused in the brickwork. "his defect is considerably reduced if the water accumulation

is prevented.

'LAST(RING

"he plastering is a method of covering uneven surfaces with a plastic material to get an even,

regular, smooth, clean and durable surface. Sometimes it is used to develop decorative finish. "he

main ob8ect of e)ternal plastering is to cover the surface to protect it from rain and other

weathering agencies besides concealing defective work manship and inferior materials.

"erms related to plastering

:1; (ackground. "he prepared surface to which first coat of plaster is applied.

: ; racking. &t is development of one or more fissures in the plaster.

:$; ra#ing. "his is the appearance of a series of hapha#ard hair cracks on the finished plastered

surface.

:'; (listering. &t is appearance of one or more small local swell ings on the finished plastered

surface.

:5; 3ado. "he bottom most part of the plastered wall where special treatment is given to plaster to

give a smooth and resistant finish.

:*; 3ots. "hey are small patches of plaster laid on the background for fi)ing screeds, etc.

:-; 3ubbing out. &t is a method of filling in hollow spaces in a solid background before applying

plaster.

: ; 9laking. &n absence of proper adhesion with the previous coat, some patches of plaster fall

down and this is known as flaking.:/; +auging. "he process of mi)ing the various ingredients of plaster is known as gauging.

:10; 7acking. "he process of making the background rough to have suitable key for plastering is

known as hacking.

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:11; Beys. "hese are indentations on the surface of under coat or background to form a mechanical

bond between the plaster applied and the prepared surface.

%eeling. &t is removal of plaster from the background.

're"ara#ion of surface for "las#ering

(esides the uality of the mortar, its adhesion with the back ground also affects the durability of

plaster. "his makes the preparation of surface of prime importance. ll the pro8ections more than

1$ mm. from the general face of the wall are removed to get a uniform surface and to reduce the

amount of plaster. "o get good key of the plaster with the wall surface, the mortar 8oints in the

brick masonry are raked out to a depth of 1$ mm.

"he 8oints and surfaces are cleaned with hard wire brush to remove loose mortar and dust.

?fflorescence, greasy spots and other patches are also scrapped and cleaned. &f the old wall is

smooth, the surface is roughened by hacking it with some tool. "he surface is washed with water

and it is kept wet till applying plaster.

"o maintain uniform thickness of the plaster and a true surface, patches of plaster :known as

screeds; 15 cm ) 15 cm are applied hori#ontally and vertically at about 1. m. apart over the whole

surface. =ortar is applied on the surface of the wall between screeds with trowel. "ypes of %laster

Follo ing are #%e )arious #!"es of "las#er commonl! used&

:a; !ime plaster :b; ement plaster :e; %laster on lath.

:c; Stucco plaster :d; Water


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chopped hemp are added at the rates of 15 kg. and / kg. to every 10 cubic metre of mortar

respectively. "he prepared mortar is kept for days before use and it is turned once in day to make

it more uniform and homogeneous.

*b+ Cemen# 'las#er. ement mortar comprises of one part of cement to $


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thick and contains a mi)ture of finest lime and well ground marble of uart# stone. "his coat is

carefully polished with lime, moist chalk and oil. "he surface obtained is very smooth and bright.

*d+ ,a#er-"roof "las#er. T%e mor#ar of #%is #!"e of "las#er

consists one part of cement, two parts of sand and pulveri#ed alum at the rate of 1 r cubic metri of sand. &ii one lifi water

a ou gin of soft soap is dissolved and this soap water is used to

prepare the mortar for plaster.

*e+ 'las#er on la#%. !ath is used as base to the plaster work. &t is mainly used for the construction

of ceiling or partition work, by fi)ing it to timber supports or steel works. !aths may be broadly

classified into two classes, i.e. :i; metal laths and :ii; wooden laths.

:i; =etal laths. Various types of metal laths are available in the market such as :&; %lain e)panded,

: ; ibbed e)panded.:$; %erfora ted,:'; 3ove


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*4+ Acous#ical 'las#er. &t is used to prepare the surface of the auditorium or hail to provide

acoustical treatment. "his plaster is a gypsum mi)ture and used as a final coat of plaster. &t is

applied in two coats of * mm. thickness each.

*5+ Asbes#os-marble "las#er. &t is a mi)ture of asbestos, cement and finely crushed marble. "histype of plaster provides elegant mar ble


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blistering in the plastered surface, "hus, properly slaked lime should be employed in the plaster

work to avoid blistering.

:'; 9alling out of plaster. "he following reasons n be listed for falling Fut of plaster2

:i; 3ue to e)cessive thermal variations in the backing or plaster.

:ii; 3ue to inade uate bond between the successive coat of the plaster.

:iii; 3ue to imperfect adhesion of the plaster to the background.

:iv; &f the backing material absorbs too much of water, the strength of the plaster and bond

between plaster and backing gets reduced.

'OINTING

%ointing is the process of finishing the mortar 8oints with a separate material in brick masonry or

stone masonry. "he mortar8oints of the masonry are raked out to a depth of 1$ to 0 mm. and the

fresh mortar is inserted in the raked spaces to form the desired shape.

%ointing is generally recommended for the finishing of e)posed e)ternal walls. &ts initial cost is

less but it re uires replacement after few years. "he use of pointing is avoided as far as possible.

Follo ing are #%e ad)an#ages of "oin#ing&

:a; "he pointing protects the 8oints from the adverse effect of atmospheric actions.

:b; &t hides defective workmanship.

:c; &t imparts better appearance to the e)posed surface of the structure.

$or#ar for "oin#ing

%ointing can be done in cement or lime mortar. "he lime mortar is prepared with e ual parts of fat

lime and fine sand which is clean and free from any organic impurities. "he mi)ture is ground

thoroughly in a mortar mill. "he cement mortar is prepared by mi)ing cement and sand in

proportion 12 1 or2 12 . "he cement should be standard portland cement and sand should be clean,

fine and free from any organic impurities. "he materials are first mi)ed in dry state on a water

Documents

UNIT-1 Reinforced Brickwork