sab 2112 masonry_12

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MASONRY (BRICK/BLOCK/STONE)

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MASONRY

http://www.masoncontractors.org/aboutmasonry/imagegallery/index.php?directory=.&currentPic=28

http://www.masoncontractors.org/aboutmasonry/imagegallery/index.php?directory=.&currentPic=28

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Contents of lecture

• Masonry materials• Types of masonry units•

Manufacture of bricks andblocks• Characteristics and testing of

bricks• Mortar for brickwork/masonry

work

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Masonry

Masonry is a type of constructionwhereby units are laid together

to form a structure

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DESIRABLE

CHARACTERISTICS• Strength

• Durability

• Resistance to water, noise and fire

• Aesthetic

• Other special requirements e.g. blastresistance















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MASONRY UNIT

BLOCK

BRICK STONE






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Block



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Block



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Stone



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Bricks

•

Bricks are produced inmany formats: solid,perforated and hollow

• Typically 215 x 102 x 65mm (length x width xheight)

• Made of clay, sand-cement, concrete andcalcium silicate







http://www.clay-bricks.co.nz/render.htm

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Face shell Central web

End web

End web

Cell

Solid

Perforated

Frogged

Hollow

holes 25 % of gross

volume of the brick

cavities exceeding 25 %of total volume of brick.

volume of indentationsmust not exceed 20 % of

gross volume.

Types of bricks (shape)

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Types of Clay Bricks

Three types of clay bricks:Common – general use; not design to provide

good finish or high strength; usually

plastered, non-load bearingFacing – for attractive appearance; no

cracks; may or may not be load bearing;

durableEngineering – good strength and durability;

high density; well fired (load bearing walls,

retaining walls, sewers, embankments etc.)

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Common Brick

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Facing Brick

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Facing Brick

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ENGINEERING BRICK

Column

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CLAY BRICKS

Clay bricks continue to be the

most important building units

Raw materials are clay or shale

Efficient material to use in terms

of their energy consumption

Strong and durable

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Clay for Brick-making

A variety clay composition and minerologydeposited at different geological period; fromsoft sticky mud to shale

Hence bricks are differ in their properties-

colour, texture, strength, density and durabilityOnly 30-40% of brick making clay are clay

minerals

Clay minerals-size less than 2 microns; theamount and particle size present in the clayaffect the cohesiveness, forming characteristics,drying and firing properties of the clay

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Cont.Too much clay can result in high drying

shrinkage; adding sand can reduce dryingshrinkage

Clays are hydrated aluminosilicates(predominance is silica and alumina); the mainminerals are: kaolinite, Illite, montmorillonite

Other mineral present in clays are: potash (K2O),Lime (CaO), Soda (Na2O), Magnesium (MgO)

and iron (FeO, Fe2O3)Chemical analysis may be undertaken, together

with minerological examination can assist inidentifying the presence of chemicals and clayminerals in the raw materials

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Manufacturing of clay bricks

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Stiff mud process

PUG MILL

MIXER

EXTRUDER

WIRE CUTTER

TUNNEL DRYER

KILN

Grind clay

Mix clay

Form clay strip

Cut bricks

@ 40oC – 150 oCDry bricks 24 – 48 hrs

Burn bricks @ 930 oC – 1320oC.60-80 hrs.

Preparation

Formation

Drying

Firing

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Manufacturing Clay Bricks

1) Clay Preparation

Objectives:

improve homogeneity and plasticity of clay

control of physical and chemical propertiessuch as shrinkage, colour and vitrificationtemperature

well prepared clay eliminate problems duringthe production process thereby reduces therejection rates

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Clay Preparation (cont.)

Process

Digging, crushing, sieving, grinding,

proportioning, mixing, tempering

Add chemicals for special purpose; eg.

barium carbonate react with soluble salts

producing insoluble product (expensive)

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MOULDING

Process of giving shape to the bricks

A variety of shaping methods that

depends on the moisture content and

consistency of the clay

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Semi Dry Process

Moisture content @ 10%

Granular consistency, pressed in 4 stages

After pressing be textured or sand faced

Can be fired without going through

drying stageSmooth finish

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Stiff-Plastic Process

Moisture content @15%

Extruded and then compacted into a mould

under high pressure

Many engineering bricks are made this

way; clay containing large quantity of iron

oxide help the fusion during firing

Smooth finish

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The Wire-Cut Process


Extruding a column of clay through a die

and cut by tensioned wire

Extrusion to a size which allow dry and

firing shrinkage

Perforated bricks are made this way, the

perforation being formed during

extrusion

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Soft Mud Process


Soft clay from shallow deposit

Rolled in sand or sawdust and pressed

manually into a mould

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DRYING OF BRICKS

Green bricks contain a considerable amount of moisture depending on the shaping process

The moisture content has to be further reduced before

firing can be carried out

Objectives:

Enable brick to be stacked higher in the kiln

Avoid too much shrinkage happening in the kiln

which might cause the stack to become unstableEnable firing temperature to be increased more

rapidly

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Drying of Bricks (cont.)Important for green bricks with high moisture

content;Temperature being increased while humidity

progressively decreased

Low rate of drying to avoid stresses that causecracking and distortion

Dried until approximately at critical moisturecontent (leather-hard)

Sufficiently rigid and strong for handling andstacking

Chamber or tunnel dryers takes 1 or 2 days,

natural drying takes 6 weeks

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FIRING OF BRICKS

Changes their physical structure and give themgood mechanical properties and resistance towater

Sintering of clay increases the strength and

decreases the soluble salt without loss of shapeSilica and alumina do not melt, they are fused

together with metallic oxides

THREE stages of firing:100 °C – water evaporation

400 ºC – burning of carbonaceous matter

900 – 1200 °C – sintering of clay

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Firing of Bricks (cont.)

Clay composition and chemicalchanges during firing influence the

final colour of bricksFe2 oxidation produce red colour

bricks

Large amount of lime produceyellowish-brown colour bricks

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(Firing Processes)

• Clamps: Bricks are stacked in large special

formations on a layer of breeze, though the bricks

also contain some fuel. The breeze base is ignitedand the fire spreads slowly through the stack,

which contracts as the bricks shrink on firing. The

process may take up to one month to complete and

fired product is very variable, many underburntand overburnt bricks being obtained. After firing,

bricks are sorted and marketed for various

applications.38

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(Firing Processes)

• Continuous kiln: These are based on the Hoffman

kiln and comprise a closed circuit of about 14 chambers

arranged in two parallel rows with curved ends. Divisions

between the chambers are made from strong paper sealed

with clay and, by means of flues, the fire is directed to

each chamber in turn. Drying is carried out prior to the

main firing process and is achieved by warm air obtained

from fire is not extinguished. Coal was traditionally usedbut firing now may be oil or gas. This process or kilns are

widely used for proper brick production.

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(Firing Processes)

• Tunnel kilns: Recently introduced kilns and they can

reduce firing time to little over one day. Bricks are

specially stacked onto large trolleys incorporating heat-

resistant loading platform. The trolleys are then pushed

end-to-end into a straight tunnel with a waist that fits the

loading platform closely. The bricks pass successively

through drying, firing and cooling zones, firing normally

being by oil or gas. The process provides high degree of control over temperature, so that the process is suited to the

production of high-strength, dimensionally accurate bricks.

Perforated bricks are often fired in this way.

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Clay Bricks

• These are made by pressing a prepared clay

sample into a mold, extracting the formed

unit immediately and then heating it inorder to sinter (partially vitrify) the clay.

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What is Clay?

• Definition: A natural earthy material that is

plastic when wet, consisting essentially of

hydrated silicates of aluminum: used formaking bricks, pottery. The common clay,

containing some iron, and therefore turning

red when burned.

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Types of Bricks

• Common Bricks: These are ordinary bricks which are not

designed to provide good appearance or high strength.

They are therefore in general the cheapest bricks available.

• Facing Bricks: These are designed to give attractive

appearance, free from imprefections such as cracks. They

are derived from common bricks to which a sand facing

and/ or pigment has been applied prior to firing.

• Engineering Bricks: These are designed primarily forstrength and durability. They are usually of high density

and well fired.

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Indentations and Perforations in

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Indentations and Perforations in

Bricks

Indentations (space) and perforations (cylindrical

holes passing through the thickness of the bricks)

may be provided for one or more of the following

reasons:• They assist in forming a strong bond between the

brick and the remainder of the structure;

• They reduce the effective thickness of the brick

and hence reduce firing time;

• They reduce the material cost and hence the

overall cost of the brick without strength loss.

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Manufacturing of Clay Bricks

There are four basic stages in brick manufacturing

• Clay preparation

• Moulding

• Drying

• Firing

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Properties of clay bricks

Physical properties

• Colour

• Texture• Size

• Density

Engineering properties

• Compressive strength

• Water Absorption• Initial rate of suction

• Efflorescence and

soluble salt content

l d

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Colour and texture

• Variety of colours:red, yellow, brownetc

• Depending onmineral content andfiring temperature

• Variety of textures:smooth, rough,bark face etc.

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Density

• Varies from 1300 – 2200 kg/m3

• Important for thermal and

acoustic property of wall – Heavier wall better sound and

thermal insulation

– Solid units have higher thermalconductivity

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Size

Bed joint Head joint

Stretcherface

Header faceBed face

Actual size 215 X102.5 X 65mm often called work size (BS)

102.5

mm

215mm

65mm

Coordinating size(brick size +mortarthickness)225 X112.5 X 75 mm

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Dimensional tolerance (MS 76/BS 3921):

• Sizes of bricks must not be outside the ranges shown in Table 1

• Must not exceed the coordinating size

• Test method – overall measurement of 24 bricks

Size

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Coordinatingsize (mm)

Work size(mm)

Overall measurement of 24bricks

Maximum(mm)

Minimum(mm)

225112.5

75

215102.5

65

52352505

1605

50852415

1515

Table 1: Limits of sizes (MS/BS)

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Compressive strength

• Most important mechanicalproperties

• Measure of quality

• Use for classifying bricks• Varies in accordance to materials and

manufacturing methods

• Available in strengths of 5 – 100N/mm2

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Water Absorption

•

Water absorption is the quantity of water that could be absorbed by theunit

• Indicate porosity • Varies widely, clay units from 4.5 to

21%, calcium silicate units from 7 to21% and concrete units from 7 to10%

• Clay bricks which absorb between 4.5and 7.0% of their weight can be usedas damp-proof course material

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• Highly absorptive clay bricksremove water from mortar

preventing complete hydration of cement

• Relation of water absorption to

flexural strength of masonry

Water Absorption

Cl ifi ti f l b i k di t

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Classification of clay bricks according tocompressive strengths and absorption

(BS)

Designations Averagecompressivestrength not lessthan (N/mm2)

Averageabsorption notgreater than (%by weight)

Engineering A 70 4.5

Engineering B 50 7.0

Damp-proof

course 1

5 4.5

Damp-proof course 2

5 7.0

Others 5 No limits

Characteristic flexural strengths and levels of water

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Mortar designation

Characteristic flexural strength, f kx N/mm2

Plane of failure parallel tobed joints

Plane of failure perpendicular tobed joints

(i) (ii) and(iii)

(iv) (i) (ii) and(iii)

(iv)

Clay brickshaving a waterabsorption lessthan 7%

0.7 0.5 0.40 2.0 1.5 1.2

Between 7 %

and 12 %

0.5 0.4 0.35 1.5 1.1 1.0

Over 12 % 0.4 0.3 0.25 1.1 0.9 0.8

Characteristic flexural strengths and levels of waterabsorption (BS 5628 Pt. 1, 1985)

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Initial rate of suction (IRS)

• The rate at which bricks absorb water frommortar during laying

• Measured in kg/m2/min. For clay bricksgenerally range from 0.25 – 2.05 kg/min/m2

Low values < 0.25 kg/min/m2

High values > 1.5 kg/min/m2

• Necessary for bond between bricks and mortar

• Water tightness

• Critical for highly stressed masonry structures

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Efflorescence and soluble salt

content• Efflorescence is the white

deposits (salts) on brick surfaces

•

Salts from bricks, groundand environment

• Usually occurs on newbrickwork

• Affect appearance but oftenharmless

• Bricks exceeding the “heavy” category should berejected

ffl d l bl l

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Efflorescence and soluble saltcontent

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Efflorescence and soluble salt

content

Source of water

Spalling effects of bricks

Levels of efflorescence (MS/BS)

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Nil No perceptible deposit of salt

Slight Up to 10% of the area of the face coveredwith a deposit of salt, but unaccompanied

by powdering or flaking of the surface.

Moderate More than 10% but not more than 50% of the area of the face covered with a depositof salts but unaccompanied by powderingor flaking of the surface.

Heavy More than 50% of the area of the facecovered with a deposit of salts and/orpowdering or flaking of the surface.

Levels of efflorescence (MS/BS)

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Calcium Silicate Bricks

(sand-lime)

• Consists of 90-95% sand (majority

passing 1.15 mm sieve)• lime (aggregate lime ratio by

weight of 10 – 20 :1)

• water

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Manufacturing

Mixing

Pressing

Autoclave

Mixing of sand, lime,pigments and water

Pressed under very highpressure to give shapeand compaction

High pressure steam curingcombining lime and sandto form calcium silicate.

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Properties of

Calcium Silicate Bricks• Size

• Colour

• Water absorption

• Strength

• Shrinkage

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Size and Colour

• Size – similar to clay bricks

• Colour – Calcium silicate

and are usually light greyand other paler shades

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Water Absorption

• Varies between 6 to 16 %

• Absorption is less relevance

for calcium silicate andconcrete units

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Strength

• Compressive strength is thecriterion

• Typically strength varies from 14 – 27.5 N/mm2

Compressive Strengths Classes and

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Compressive Strengths Classes andRequirements of Calcium Silicate (BS187)

Designations Class Mean compressivestrength of 10 bricksnot less than (N/mm2)

Shrinkage notgreater than(%)

Load-bearingbrick or facingbrick

7

65

4

3

48.5

41.534.5

27.5

20.5

0.040

Facing brick orcommon brick

2 14.0

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CONCRETE BRICK AND

BLOCK

Concrete Bricks and Blocks

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• Bricks are units with size notexceeding 337.5mm inlength, 225mm in width and112.5mm in height. Biggerthan this are called blocks

•

Lengths 400 – 600 mm,heights 150 – 300 mmThickness 60 – 250 mm

• Consists of aggregates,cement and water

•

May contain additives suchas air entraining agents,pozzolanic material,colouring pigments

Concrete Bricks and Blocks

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Concrete bricks and blocks

Standard blocks

Screening blocks

Bl k

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Blocks

• Three main types of blocks

Solid blocks – blocks containing

no formed cavities

Cellular blocks – blockscontaining cavities which do notfully penetrate the block

Hollow blocks – blockscontaining cavities which fullypenetrate the block

Manufacturing of Concrete Blocks

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Separate and

weigh aggregate

Aggregates are storedseparately by density and

gradation, then weighedand transported byconveyor to mixer.

Mixing Molding

EjectionCuring

Cement, aggregate,water, pigments andother admixtures are

combined to formdamp but not wetmix.

Mix is fed

into a mouldandconsolidatedby vibration

Units in sets of three ejected frommoulds.

Curing is done under saturatedconditions. Temperature may beraised to accelerate hydration(steam curing) for 18 hours, orautoclaving (high pressure)steam for 4-12 hours.

Manufacturing of Concrete Blocks

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Handling of aggregates ina plant

Block machine inoperation

Manufacturing

Properties of Concrete Blocks (BS 6073)

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Properties of Concrete Blocks (BS 6073)

Type Face size (440 215 mm)

Thickness (mm) Minimum averagecompressive strengthsof unit (N/mm2)

Solid 75

100

7.0 – 21.0

Solid or cellular orhollow 140150

190

200

215

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Paving Units

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Stones

Most common

• Limestone

• Granite

• Marble

• Slate

Marble quarry

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Gl Bl k

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Glass Blocks

Test Methods for Bricks

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Dimensional deviations• Overall measurements of 24 bricks

Length Width Height


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Test Methods for BricksCompressive strength

• Select 10 bricks from a stack • Bricks are immersed in water for 24 hours before

testing

• Faces are capped between 3 mm ply sheets or

packed before testing to reduce the effects of roughness, lack of plane and platen effects

• Bricks loaded normal to its bed face. Tested untilfailure. Compressive strength is calculated as the

average of 10 bricks as below:

Compressive strength2maximum load

= N/mmbed face area

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Compressive Strength

Compressive Machine (Tonipact)

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Water Absorption

2 types of tests:

• 24 hours cold immersion test

(Partially saturated condition)• 5 hr. boiling test (Fully saturated

condition

24 hours cold immersion test(ASTM C67)

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– Select 5 bricks from a stack – Dry bricks in the oven @110ºC for not less than 24

hrs – Cool the specimen and weigh each brick (Wd) – Immerse the dry bricks in clean water at 15 to

30ºC for 24 hours – Remove the bricks and weigh each brick (Ws) – Calculate the absorption of each brick as follows:

Absorption % =

Report the average absorption for the 10 bricks

s d

d

W - W100

W

(ASTM C67)

5 hours Boiling Test

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5 hours Boiling Test

• Select 10 bricks.

• Heat at 110 C for not less than48 hours – dry bricks.

• When cool, weigh the bricksand record the dry mass (wd)

• Then boil for 5 hours and thenallow to cool naturally in thewater a minimum of 16 hoursand a maximum of 19 hours.

• Weigh each brick and recordthe wet mass (ws)

• Water absorption A %=

s d

d

W - W100

W

Initial Rate of Suction

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Initial Rate of Suction• Select 10 bricks• Dry bricks in the oven

• When cool, weigh the bricksand record the dry mass(m1).

• Then immerse the dry brick in water for 1 min. Depth of immersion is 3± 1mm

• After 1 min remove the wetbricks and weigh (m2)

• Calculate initial rate of suction using formula below:

1000(m - m )2 2 1IRS (kg/m /min) =

A 2 A is the area of the immersed face of the brick in mm

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MORTAR FOR

BRICKWORK

MASONRY MORTAR

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MASONRY MORTAR

MORTAR

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MORTAR

MORTAR

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O

MORTAR

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MORTAR

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MORTAR

A mixture of materials for jointingmasonry units

Made up of sand, a binder such as

cement or lime, and water

The thickness of mortar in brickwork

is normally 10 mm thick and should

not exceed 15 mm because of high

shrinkage

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FUNCTION OF MORTAR

Joint the units together

Seals any gaps to resist wind and

rain penetration

Take up the tolerances between

building units, fill up the holesbetween the units

REQUIREMENTS

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Q

Should be able to support theweight of the brick

Should not segregate, easy tospread and align the units

Adhere to the vertical face of the

units

Should impart sufficient

strength to the whole unit

REQUIREMENTS (cont.)

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Q ( )

Should permit movement (unless this is

negligible or joints are provided). Whenmovement occurs, it should take place in theform of microcracks within the mortar rathercracking of the bricks or blocks

“mortar must not be stronger than the units itis bonding”

Should be durable, resisting the penetration of

water through the unitsShould contribute to the aesthetic appearance

of the wall

SAND FOR MORTAR

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99

Well graded – even distribution of particlesizes from fine to coarse. In well gradedsand the void is one-third of the totalvolume

San containing silt and clay should not beused which can lead to unacceptableshrinkage movement

Sand lack in finer particles causes poorwater retention resulting in a harshunmanageable mortar

BINDER MATERIALS

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100

Hydraulic lime

From limestone contaminated with

clay which gave the resulting

hydraulic properties

Relatively weak and slow setting

Only suitable for thick wall and low

stressLime-sand mortars are obsolete

ORDINARY PORTLAND CEMENT

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101

Principal binding ingredients in modernbinders

Cement and sand (1:3) by volume

produces high strength, good durability,density and hardness

For most application such properties are

not required.

Can be replaced with pozzolanicmaterials

MASONRY CEMENT

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102

Premixed binder, 75% OPC,

25% inert fine mineral filler andpowdered air entrainingadmixture

On no account should masonrycement be used in place of OPC

in making up the other type of mortar

SULPHATE RESISTING CEMENT

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103

SULPHATE RESISTING CEMENT

Sulphate Resisting Portland Cement

may be used in place of OPC tocombat sulphate attack whereprolong wet condition are likely

The soluble sulphates are eitherfrom the ground or in clay bricks

The proportion of the mortarconstituents are not altered

Table 15 BS 5628:Part3

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104

Cement:

Lime: sand

Masonry

cement:sand

Cement:San

d with

Superpl.Increasing Increasing 1:0 to ¼:3 - -

Strength and Ability to 1:1/2:4 to

4.5

1:2.5 to3.5 1:3 to 4

Improving accommodate 1:1:5 to 6 1:4 to 5 1:5 to 6

durability movements 1:2:8 to 9 1:5.5 to 6.5 1:7 to 8

(arrow upward) (arrowdownward)

1:3:10 to12

1:6.5 to 7 1:8

NON-HYDRAULIC LIME

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105

Insufficient setting and hardening strength to

make them as a total binder

Added as a binder constituent to produce

cement: lime: sand mortar

Lime has good water retentive properties

which give good workability characteristics

and promote bonding of the Portland cement

Have better resistance to rain penetration

AIR-ENTRAINERS

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106

As an alternative to lime as a binder supplement, thereduced volume can be made with minute bubbles by

adding air-entraining agent

In powder/liquid form but must be intended for

mortar

Air entrainment must not exceed 12% of the volume

because it reduces the bond strength

At 15% or above the bonding performance is seriouslyimpart

Induces good plasticity/workability characteristics

Linear Thermal Movement of Masonry unit and Mortar

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107

Material Coeff. Of Linear ThermalExpansion (x 10-6 /K)

Fired-clay masonry

units

4 - 8

Concrete masonry units 7 - 14

Calcium silicate

masonry units

11 - 15

Mortars 11 - 13

Moisture movement and Thermal properties of CommonBuilding Materials

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108

Material Reversible moisture

movement

Irreversible moisture

movement

Coeff. Of Thermal

Exp. (x10-6/ K)

Timber +- 0.5-2.5 _ 4 - 70Steel - _ 10 - 18

Concrete +-0.02-0.10 -(0.03-0.08) 7 - 14

Dense concrete

agg. products +-0.02-0.04 -(0.02-0.06) 6 – 12

Lightweight agg.

conc.+-0.02-0.06 -(0.02-0.06) 8 - 12

Aerated

(autoclave)products

+-0.02-0.03 -(0.05-0.06) 8

Calcium silicate

brick+-0.01-0.05 -(0.01-0.04) 8 - 14

Clay brick +-0.02 +(0.02-0.07) 5 - 8

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HAVE A NICE DAY

sab 2112 masonry_12

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