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CONSTRUCTION

TECHNOLOGY &

maintenance

CEM 417

SOURCES FROM slide:

MOHD AMIZAN MOHAMD

MOHD FADZIL ARSHAD

SITI RASHIDAH MOHD NASIR

FKA, UiTM Shah Alam.

PILES

WEEK 10

At the end of week 10 lectures, student will be able to :

Explain various types, functions and factors of

selections for piling. (CO1; CO3)

LEARNING OUTCOME

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INTRODUCTION

Function:-

To transmit foundation loads through soil strata

of low bearing capacity to deeper soil or rock

strata having a high bearing capacity, or used in

normal ground condition to resist heavy uplift

forces or in poor soil conditions to resist

horizontal loads.

PILES CAN GENERALLY BE CLASSIFY WITH RESPECT

TO THEIR FUNCTION :- FRICTION PILES OR END

BEARING PILES.

FRICTION PILES

In cohesionless soils – the applied load is

transferred to the surrounding soil mainly

through skin friction along the surface of the

piles. A large part of load is also carried by the

pile toe. The skin friction resistance varies

mainly with relative density of the soil and with

the shape of the pile.

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FRICTION PILES IN COHESIVE SOIL – ALMOST

THE WHOLE LOAD ON THE PILE IS

TRANSFERRED TO THE SURROUNDING SOIL

ALONG THE PILE SURFACE THROUGH SKIN

FRICTION AND ONLY A VERY SMALL PART

THROUGH THE PILE TOE.

END BEARING PILES – pilesdriven down to a layer with high

bearing capacity, the applied load is transferred from the pile to

the surrounding soil mainly through the pile toe

CLASSIFICATION OF PILES

Displacement Piles

Piles are driven or

pushed, vibrated or

screwed into the

ground, displacing the

soil outwards and

downwards but no

materials are

removed.

Replacement Piles

A hole is form in the

ground by removal of

material from the

ground and thus

material is displaced

by a concrete material

formed in the ground.

DISPLACEMENT PILES DRIVEN PILES – Preformed unit driven into the soil

by blows of hammer.

Materials of performed pile are :-

Timber ;

Concrete; or

Steel

Advantage of performed unit – can be inspected and

checked as a sound structural member before it is driven into

the ground

•

•Length of pile to be driven depends on the local variation of

soil strata. Disadvantages when cutting off unwanted pile or

the addition of extra lengths can become an expensive

additional cost.

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DRIVEN -TIMBER PILES

Usually square sawn timber of sizes 225 x 225 to 600 x 600mm.

Easy to handle and driven by percussion or drop hammer.

Most timber piles are fitted with an iron or steel driving shoe to prevent splitting due to driving, and have iron ring around the head to restrict ‘brooming’ of the pile head due to overdriving.

Timber pile is not suitable of driving through dense strata or strata with obstruction.

CONT..

DRIVEN -TIMBER PILES

Characteristic of Timber Piles :-

1. Must be free from short or reverse bends, large or

loose knots, slake, splits and decay.

2. Must be free from short or reverse bends and from

crooks > 11/2 diameter of the pile at the middle of

the bend.

3. Straightness of grain line between centres of butt

and tip must be within the body of the pile.

4. Uniform taper from the butt to tip.

DRIVEN – PRECAST CONCRETE PILES

Used where soft soils overlaying a firm strata are encountered. Lengths up to 18m with section sizes ranging from 250 x 250mm to 450 x 450mm carrying loadings up to 1000kN.

The precast concrete driven pile has little frictional bearing strength since the driving operation moulds the cohesive soils around the shaft which reduces the positive frictional resistance.

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CONT..

DRIVEN – PRECAST CONCRETE PILES

Available Precast Concrete Piles are :-

Precast Reinforced Concrete Piles – made of concrete statically cast in uniform section before driving into ground and reinforced with steel bars.

Precast Pretensioned Concrete Piles - made of concrete statically cast in uniform section & suitably reinforced with pretensioned prestressingsteel.

Precast Pretensioned Spun Concrete Piles –hollow pile made of concrete cast by centrifugal spinning. Suitably reinforced with pretensionedprestressing steel.

CONT..

DRIVEN – PRECAST CONCRETE PILES

Problem encounter when using this pile in urban area :-

Transporting the complete length of pile through narrow or congested streets;

The driving process which is generally percussion can set up unacceptable noise or vibration;

Many urban sites are themselves restricted or congested thus making it difficult to manoeuvre the long piles length around the site.

DRIVEN – STEEL PILES

Two main types of steel pile in general use:-

H-section pile – usually in the form of wide

flange sections. It do not cause large displacement

of the soil, thus useful where upheaval of the

surrounding ground would damage adjoining

property or where deep penetration is required

through loose or medium dense sands.

Disadvantage is the tendency to bend on the

weak axis during driving. Results in considerable

curvature if driven in deep penetration. Also has

low resistance to penetration in loose sandy soil.

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CONT..

DRIVEN – STEEL PILES

Box Piles – steel box piles are fabricated by

welding together steel plates or trough section to form

hollow piles capable of carrying very high compressive

uplift or lateral loads.

DRIVEN AND CAST –IN- PLACE PILES

Displacement pile formed by driving a tube with a closed end either with a plug or loose shoe into the soil to the required depth or set. A reinforcement and concrete is filled in the tube. This tube may or may not be withdrawn.

Suitable where the length of pile required varies.

Economically formed in diameter of 300 to 600 mm and can carry loads of up to 1300kN.

Required heavy piling rig, open level site and site where noise is restricted.

CONT..

DRIVEN AND CAST –IN- PLACE PILES

Franki driven in-situ piles

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BORED AND CAST –IN- PLACE PILES Is a replacement pile . Pile formed by boring a hole

in the soil, thus removing a column of soil and replace it with in-situ concrete.

Suitable to use in sites where piling work to be carried out close proximity to existing building or where vibration or noise restricted.

It is carried out by dropping a heavy cutter to dig into the ground and then raising and remove the spoil material which it brings with it.

Formation of holes can be by :-

percussion bored, or

rotary bored.

ADVANTAGES

Length can be readily varied to suit varying ground condition.

Soil remover in boring can be inspection and if necessary sampled or in situ test made.

Can be installed in vary large diameter. End enlargement up to two or three diameters

are possible in clay. Material of piles is not dependent on handing

or driving conditions. Can be installed in vary long length. Can be installed without appreciable noise or

vibration. Can be installed in condition of very low head

room. No risk of ground heave.

DISADVANTAGES

Susceptible to waisting or necking in squeezing ground.

Concrete is not places under ideal condition and cannot be subsequently inspection.

water under artesian pressure may pipe up pile shaft washing out cement.

Enlarge and cannot be formed in cohesionless material.

cannot be readily extended above ground level especially in river and marine structures.

Boring method may loosen sandy and gravelly soils.

Sinking piles may cause loose of ground in cohesionless soil, leading to settlement of adjacent structures.

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CONT..

DRIVEN AND CAST –IN- PLACE PILESProblems normally encountered :-

1. Necking – due to ground water movements washing away some of the concrete thus reducing the effective diameter of the pile shaft and consequently the cover of concrete over the reinforcement.

2. Ground heave – caused by displacement of the soil by the drive tube. Can cause tension failure in the shafts of adjacent piles already driven and in worst case lifting of the completed piles. However, this can be minimized by the enlarged base of the piles in conjunction with reinforcement in the shaft thus anchoring the piles against uplift.

CONT..

PERCUSSION BORED PILES Suitable for clay and / or gravel subsoil.

Diameter from 300 to 950 mm and designed to carry load up

to 1500 kN.

CONT..

PERCUSSION BORED PILES

Steel tube of length 1 to 1.4m screwed together is sunk by extracting the soil from within the tube liner using percussion cutters.The tube liner normally sink under its own weight but can also be driven in with slight pressure using hydraulic jack.

When correct depth achieved, a cage of reinforcement is placed within the liner and then filled it with concrete. Tamping is carried out as the liner is extracted by using a winch or hydraulic jack operating against a clamping collar fixed to the top of the steel tube lining.

An internal drop hammer can also be used to tamp and consolidate concrete but usually compressed air is used.

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CONT..

ROTARY BORED PILES Suitable for most cohesive soil e.g. clay.

Formed using an auger which may be operated in conjunction with the steel tube liner.

This auger is normally mounted on a lorry or tractor, raised to the surface and spun off the helix to the side of the bore hole where the spoil is removed. If flight auger is used,the spiral motion will brings the spoil to the surface.

GRAB CONSTRUCTION - CASED

Using crawler crane and casing oscillator

Main soil – sand and gravels with high demands on casing technology

Used chisels to break up bedrock and boulders

Pile diameter ranging from 620-2000mm

Depths generally up to 50m

ROTARY DRILLING WITH KELLY -CASEDStandard cast-in-place pile :-

Use in all types of soil

Use where site conditions are restricted

Vibration free drilling. Casing installed by rotary drive

Casing oscillator can be used for larger pile diameters and greater depths.

Pile diameter generally 600 –1800 mm

Depth generally up to 40 m but greater depth possible.

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ROTARY DRILLING WITH KELLY – BOREHOLE

SUPPORTED BY HYDROSTATIC PRESSURE

1. Rotate or vibrate

starter casing to

required depth.

2. Remove driilling spoil

with bucket attached

to kelly bar with

borehole supported

by slurry.

3. Recycle slurry to

remove soil and

insert reinforcing

cage.

4. Place concrete

simultaneously

displacing slurry.

5. Complete pile

1 2 3 4 5

ROTARY DRILLING USING TWIN ROTARY

HEAD – FRONT OF WALLSuitable for all types of soil and on restricted sites.

Vibration free, and can be installed against existing wall. Continuous

flight auger and casing installed simultaneously by counter rotating twin

rotary drives. Pile diameter from 305 to 550mm and depth generally up to

15m

1 2 3 4

1. Install casing and

continuous flight auger

to require depth using

counter rotating drives.

2. Inject concrete through

hollow stem auger,

simultaneously

withdrawing auger and

casing.

3. Insert reinforcement

cage into concreted

borehole.

4. Completed pile

ROTARY DRILLING USING FLIGHT AUGER –

CONTINUOUS FLIGHT AUGER SYSTEMAll types of soil and at restricted sites.

Vibration free. Reinforcement can be pushed or vibrated into fresh the fresh

concrete. Diameter from 400 – 1000mm . Depth generally up to 18 m.

1 2 3 4

1. Rotate continuous

flight auger to required

depth.

2. Inject concrete

through hollow stem,

simultaneously

withdrawing auger

without rotation.

3. Vibrate or push

reinforcement cage

fitted with spacers into

fresh concrete.

4. Completed pile.

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COMPOSITE PILES

Combination or two or more types as mentioned or

combination of different materials in the same types of

pile.

Used in ground conditions where conventional piles are

unsuitable or uneconomical.

Examples of composite piles :-

‘Prestcore’ pile

Shell pile

Cased pile

COMPOSITE PILES :-Prestcore pile – formed inside a line bored hole. It is a

replacement pile and can be of precast or insitu concrete.

Advantage – Problem of necking is eliminated which made it suitable to use in waterlogged soils.

Construction stage :-

1. Lined bored hole formed by percussion bored method.

2. Precast units which form the core of the pile are assembled on a special mandrel and reinforcement is inserted before the core unit is lowered into position.

3. By means of pneumatic winch, the raising and lowering the pile core which is attached to the head of lining tube to consolidate the bearing stratum.

4. Withdraw the lining tube and grouting with the aid of compressed air to expel any ground water.

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COMPOSITE PILES :-

Shell – Is a driven or displacement pile consisting of a series of precast shells threaded on to a mandrel and top driven to the required set. After driving and removing the mandrel the hollow core can be inspected, cage of reinforced can be inserted and void filled with in-situ concrete.

Suitable in waterlogged and soft substrata with readily adaptable

length.

Advantages :-

1. The shaft can be inspected internally before in-situ concrete is introduced,

2. the flow of water or soil into the pile is eliminated,

3. The presence of corrosive conditions in thes soil can be overcome using special cements in the shell construction.

COMPOSITE PILES :-

Cased Pile

Using steel strip or plate which is formed into a continuous

helix with

adjoining edge butts welded

as driving tube and filled

with in-situ concrete.

Driven into position by

internal drop hammer

operating within the casing.

FACTOR GOVERNING THE SELECTION OF PILES :-1. Location and type of structure – driven or driven and cast in-

place pile where shell remains in position are most favour for works over water. Structures on land provide wide choice of types –usually chosen the cheapest for moderate loading and unhampered site condition. If proximity of existing structure should choose the types without giving ground heave, vibration or noise.

2. Ground condition – influence the pile types and techniques.E.g. driven piles not economical to use in ground condition containing boulders and where ground heave would be detrimental. Driven piles preferred for loose water bearing sands or gravels where compaction due to driving can develop the full potential bearing capacity of these soils. Steel H-pile gives low ground displacement suitable where deep penetration require in sand and gravel. Stiff clay favour for bored and under-reamed types.

3. Durability – in marine condition suitable to use precast concrete pile, while timber is rejected in such condition.

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TYPE OF PILE SHOE FOR VARIOUS GROUND CONDITION

PILE TESTING

Objective is to confirm that

the design and information of

the chosen pile type is

adequate.

Test piles are usually

overloaded by at least 50% of

the design working load to

near failure or to actual

failure.

Record of driving

resistance of test pile

LOAD TEST

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BRICKS

WEEK 10

At the end of week 10 lectures, student will be able to :

Explain the definition, classifications, types and process of bricks. (CO1; CO3)

Identify the various types of brickworks bonding, dampness protections and anchorage. (CO1; CO3)

LEARNING OUTCOME

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HISTORY

The art of brick making can be traced back to before 6000

B.C. Peoples of Mesopotamia built palaces and temples of

stones and sun-dried brick by 4000 B.C. Roman then used

bricks for arches and roof vaults in their basilicas, baths,

palaces and aqueducts.

In mid century, the development brought by the Islamic world

by building magnificent palaces, markets and mosques of

brick, while the Europeans built fortresses and cathedrals

In the 19th century, the effects of the industrial

revolution transformed brickmaking from a hand

craft to a mechanized factory. Machines were

invented and developed to mould, press and

exclude clay bricks and improved kiln were designed

to fire greater quantities of bricks, quicker and with

more consistency.

In 20th century, development in the masonry construction -

new techniques for steel reinforced masonry, high strength

mortars, high structural strength masonry units and

masonry units of many types that reduce the number of

labour required.

HISTORY Fortress

In Malaysia, brick is widely used for buildings, civil engineering

works and landscapes features. our rich heritage masonry

buildings built during the pre-war era. One of the best examples

is the Sultan Abdul Samad Building.

Areas where bricks are commonly applied are as partition walls,

cladding and facings, perimeter and garden wall, hard

landscaping and paving and flooring. Bricks can also serve as

external and internal load bearing wall or load bearing piers and

column.

APPLICATIONS

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Figure 3: Low Rise – Loadbearing and Cladding

Figure 4: High Rise – Loadbearing and Cladding

Figure 5: Reinforced Structures and Low-Energy Building

Figure 6: Exterior wall and interior wall and flooring

Figure 7: Bricks in Hard Landscaping

Retaining wall Freestanding wall Pathways

Patio Barbecue Steps and walkways

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Figure 8: Load bearing arch bridge

Figure 9: Column and Pier spine wall

Figure 10: Window sill and Arch

door

Bricks, stones, concrete blocks are collectively known as

masonry units.

Masonry is the building technique.

Mason is a person who stacks pieces of masonry unit a top one

another to make walls and also known as bricklayer.

Brickwork is the exterior of most houses and is not only a

structural component but also protects against weather and

decorates.

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coordinating

size

work size

65mm

215mm

102.5mm

Figure 11: Brick dimension

Brick as defined by MS 76: 1972: Part 2 and BS 3921: 1985:

Clay Bricks as a walling unit not exceeding 337.5 mm in length,

225 mm in width or 112.5 mm in height.

Bricks are known by their coordinating size; that is the actual size

plus a 10 mm joint allowance to three faces and tolerances. The

standard brick of nominal dimension of 225 x 112.5 x 75 mm has

actual work size of 215 x 102.5 x 65 mm. (see Figure 11)

Malaysian Standard, MS 76: 1972 classifies bricks under three

headings:-

1. VARIETIES

The standard divides varieties into three forms and they are

common, Facing and Engineering:-

Figure 12: Common, Facing

and Engineering bricks

COMMON : bricks made without any particular attention to give

an attractive appearance and for general construction work such as

for backing walls, internal walls, walls with applied finishes and

foundation work. Figure 13 shows example of common brick use

as backing wall.

Figure 13: Common brick use as perimeter wall

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Figure 14: Facing brick used as an external

wall

FACING :

bricks of consistent colour and texture,

reasonably free from surface defect or

blemishes, customize or selected to

have an attractive appearance intended

for the construction of fair-faced

walling without plastering or other

surface treatment. Figure 14 shows

facing brick used as an external wall.

ENGINEERING :

having a dense and strong semi-

vitreous body, conforming to define

limits for water absorption and

compressive strength,

i.e. strong dense bricks.(Figure 15)

Figure 15 : Engineering bricks

The standard recognizes three qualities of bricks, and they are:-

INTERNAL QUALITY : suitable for internal use only.

ORDINARY QUALITY : less durable than the special quality,

but normally durable in the external face of the building.

SPECIAL QUALITY : durable even when used in situations of

extreme exposure where the structure may become saturated, e.g.

retaining walls, sewerage plants or paving. Such bricks have

clearly defined limits for soluble salts content.

QUALITIES

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The standard distinguishes types of brick according to their physical

form, and they are:-

SOLID :

have cores or cells passing through or nearly through the brick and

constitutes no more than 25 percent of their gross cross-sectional area,

or frogs that is a depressions in the bed face of brick that do not exceed

20 percent of its gross cross-sectional area. A core or cell is defined as

a hole less than 20mm wide or less than 500mm2 in area with a

maximum three larger holes not exceeding 3250 mm2.

PERFORATED :

if the holes passing through the brick exceed 25 percent of its gross

cross-sectional area and with a maximum three larger holes not

exceeding 3250 mm2. Small holes lesser than 25 percent.

TYPESPerforated brickSolid Brick

HOLLOW : means holes passing through the brick exceed 25

percent of its gross cross-sectional area and the holes are larger

than those defined as small holes. Large holes greater than 25

percent.

CELLULAR : means a brick which holes are closed at one end

and exceed 20 percent of its gross cross-sectional area.

TYPES

Hollow brick Celular brick

Squint

Circular

Bullnose

Figure 20: Special shapes brick Figure 21: Arch over an opening.

SPECIAL SHAPES : bricks of special shape and size, other than the

normal rectangular prism. These are accessory bricks used to form

curves or non right-angled corners, curved walls, arches or to form

features or construction details that cannot be built using standard

units unless they are cut and pieced together.

E.g. squints, circular and bullnose bricks. (Figure 20)

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CLAY BRICKS

The materials used for making clay brick range from soft and

plastic surface deposits to hard mudstone and shale.

Clay bricks are produced by mixing the finely ground clay with

water, moulding, extrusion or pressure into the desired shape,

drying it, and burning it.

The shape obtained should retain its original shape without

undue shrinkage, warping or cracking when the bricks are dried

and fired.

Manufacture of Clay Bricks

The various methods of production of clay bricks are governed

by the nature of the clay or shale, and may be divided into:-

Semi-dry Process or

Semi-plastic Process

The clay or shale is comparatively dry. The raw

material is ground to a fine powder by heavy rollers,

passed through the screen, mixed to a uniform

consistency, pressed and re-pressed in moulds and

burnt.

Stiff-plastic Process Similar to the semi-dry or semi-plastic process, except

that the water content of the material is increased and

less powerful machinery is needed to mould the brick.

Plastic Process The clay or shale suitable for this process contains a

large proportion of moisture. This type of process is

used for making wire-cut and hand-made bricks. The

bricks must be carefully dried before being burnt in

the kiln.

The stages involved in manufacturing clay bricks :- preparation of

the raw materials, moulding, drying and burning.

PREPARATIONClay or shale dug either by hand or mechanical excavators from the

quarry or pit need to be cleaned to remove any undesirable material

such as stone or coarse vegetable matter, etc. For making common

bricks, the raw material obtained will be quarried direct to the

crushing machinery. However, for producing of more expensive

bricks, requires the selection of material from different strata and this

is normally made at the quarry-face.

These materials are blended together by mechanical mixer in

conjunction with the grinding or crushing machine. After being

ground the material is passed through a screening machine to ensure

that only fine, well graded material passed forward for moulding.

Those coarse material retained on the screen is returned for further

grinding.

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MOULDING – The prepared clay or shale is machine mould

by either the wire-cut process or pressed process, or it may be

hand moulding

Machine mould :- Wire Cut Process

Figure 22: Wire cut machine

The clay usually fairly soft and of fine

texture is extruded as a continuous plastic

band or column and propelled over oiled

rollers to the cutting table. This cutting

table consists of a frame containing

several wires at a distance apart equal to

the thickness of the bricks plus the

shrinkage allowance. Bricks made by wire cut process

contain about 15% to 25% moisture and therefore must be

partly pre-dried in chamber or tunnel dryers before placed

it in the kiln for firing. Wire cut bricks do not have frogs.

(Figure 22)

Pressure Process

The prepared clay is automatically fed into the moulds which are

the size of a brick plus shrinkage allowance.

Moulding bricks by pressure can be done either by hand or by

steam or electric power.

In the steam or electric power, the rotary press or belt driven press

machine with a number of moulds are brought in turn under the

plunger where the prepared clay will be discharged and

consolidated it under great pressure. After consolidation, the bricks

are removed either by an upward movement of the base or by the

dropping of the sides.

Hand Mould

Good quality clays are normally a prerequisite for hand

moulding.

They are made up of softer consistency having a rich texture,

beautiful colouring and durability. The prepared plastic clay is

left to stand or sometimes resorted as ageing for a period varying

from one day to several weeks in cool chamber to ensure a

uniform distribution of the water throughout the mass and the

decomposition of any organic matter.

This process is to increase the plasticity and workability of the

paste and preventing the development of cracks, blisters and

other defects.

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Figure 23: Artificial drying –

brick stackedDRYING

Normally bricks made of stiff-plastic

process or having water content exceeding

25% have to be dried before being placed

in the kiln.

Drying can be done either by artificial

drying or by natural drying. In artificial

drying, the heating mediums can be of

steam, direct heat from fires or waste heat

from kilns and boilers. The dryers include

the hot floor, shed, chamber and tunnel

types.

In natural drying, normally a well ventilated shed is used where the

bricks are stacked on racks and dried by the circulation of un-

heated air.

BURNING

In this process, bricks are fired in the kiln. Firing of bricks

produces a number of complicated chemical and physical

changes in clay, therefore the degree of control of the inside

temperature of the kiln is very important.

Typically the temperature of firing is about 900oC to 1200 oC.

The colours of the clay bricks are generated by the reaction of

the raw materials to the firing.

Differences in temperature and atmospheric conditions during

firing give rise to variations of colour. Kilns may be classified

into intermittent, continuous and tunnel.

Table 3: Types of kiln

Intermittent Kiln For firing special bricks or other requirements. It is a

permanent structure with either down drought, horizontal

draught or up-draught kiln according to the direction of the

fire. The most commonly used is of down drought. Consists of

rectangular chamber lined with fire brick having four walls and

an arched top which incorporates a heat-insulating ring

composed of porous bricks to reduce the amount of heat

transmitted through the structure and therefore effects a saving

in fuel. The heat from the fuel will passes upwards to the arch

and deflected it down through the openly stacked green brick.

The produced gases will escaped through perforations in the

floor to a horizontal flue connected to a tall chimney.

Continuous Kiln Suitable for large and regular outputs. It consists of a number of

chambers connected in such a way that the operations are

uninterrupted and the waste heat is utilized to dry and pre-heat

the green bricks. Each chambers in turn being loaded with

green brick, fired, burnt, cooled and emptied. The structure

consists of walls of ordinary brickwork, lined with firebricks

jointed with refractory cement. The top is generally arched and

the floor is usually constructed of hard bricks bedded on sand

or concrete. The kiln is divided into compartments or chambers

and the number of compartment varies.

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Tunnel Kiln In tunnel kiln, the stacked bricks will be ferried by cars or

trucks on a track by a powerful hydraulic ram, while the

fires stay still. The brick will be traversed on kiln car,

passes along a tunnel through preheating, firing and

cooling zone. The firing zone and part of the cooling zone

are lined with firebrick. The temperature and track speed

of the kiln car are controlled to provide the optimum

conditions in each zone, and may be varied to produce a

specific functional and / or appearance characteristics.

KILN

Figure 24: Intermittent kiln and Continuous kiln

Properties of Clay BricksThere are many kinds of clay bricks available and they vary

considerably in appearance and function properties depending on

the purposes for which they are intended. The British Standard, BS

3921: 1985 has specifies certain requirements for clay brick for

use in walling, and they are dimensions, compressive strength,

water absorption, soluble salt content, efflorescence and sampling.

Dimensional

Deviation

The individual size should not exceed the coordinating

size 225 x 112.5 x 75 mm, and the overall measurement

taken from 24 samples of bricks should not fall outside

the limit as given in the BS 3921: 1985, i.e. maximum of

5235 x 2505 x 1605mm and minimum of 5085 x 2415 x

1515mm.

Compressive

Strength

Compressive strengths ranging from about 7 to more than

100 N/mm2. The strength varies depending on the clay

composition and the firing. It is subjected to creep at normal

temperature and the Young’s modulus lies between 5 and 30

N/mm2. The strength of a brick is taken from mean of 10 nos.

of bricks of random sampling. (See Table 1)

Water Absorption The water absorption of the bricks used in a wall affects the

mode of rain penetration. It is the percentage increase in

weight when it is saturated. The rate of absorption plays an

important role in the bonding of the brick to the mortar in

the joint. If the brick absorbs water from the mortar too

quickly a poor bond will result, causing leaks and other

damage.

The amount of water absorption depends on the clay

composition, duration and temperature of firing. The

percentage of water absorption is taken from the mean of 10

nos. of bricks of random sampling. (See Table1)

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Soluble salt

content and

Efflorescence

Soluble salts particularly calcium sulfate in brick are liable

to become discoloured by the formation of a whitish deposit

known as efflorescence or salting. These salts were brought

to the surface and deposited there by water that had seeped

into the brickwork, dissolved the salts, then migrated to the

surface and evaporated.

Commonly found in new brickwork and on faces of old

external walls which are subjected to excessive dampness.

Therefore in order to minimize the risk of efflorescence and

soluble salt attack is to design the brickwork so that it

remains dry, i.e. not saturated. (See Figure 25)

Most types of newly form efflorescence can be easily

removed with water and brush.

Sampling The required number of brick for testing can either be

from random or representative sampling, which ever is

possible. Standard required 10 nos. of bricks for each

testing to be taken from each consignment.

Table 1: Classification of bricks by compressive strength and water

absorption

Class Compressive Strength

(N/mm2)

Water Absorption

(% by mass)

Engineering A

Engineering A

≥ 70

≥ 50

≤ 4.5

≤ 7.0

Damp-proof course 1

Damp-proof course 2

≥ 5

≥ 5

≤ 4.5

≤ 7.0

All others ≥ 5 No limits

Source: BS 3921 : 1985

Table 2: Categories for soluble salt content and efflorescence of clay brick

Soluble salt content:-

Percentage by mass

(%)

Designation Remarks

Calcium ≤ 0.300 Low (L) Normal (N) – No limit on

soluble salt contentMagnesium ≤ 0.030 Low (L)

Potassium ≤ 0.030 Low (L)

Sodium ≤ 0.030 Low (L)

Sulphate ≤ 0.500 Low (L)

Efflorescence:-

Nil No perceptible deposit of salts

Slight Up to 10% of the area of the face covered with a deposit of salts, 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 deposit of salts, but unaccompanied by powdering or flaking of the

surface.

Heavy More than 50% of the area of the face covered with a deposit of salts

and/or powdering or flaking of the surface.

Source : BS 3921 : 1985

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Figure 25: Efflorescence in brickwork

CALCIUM SILICATE BRICKS - in BS 187: 1978(Also known as sandlime, or sometime as flintlime bricks)

The raw materials are siliceous aggregates, high calcium lime

and water.

A very fine aggregate with the majority passing a 1.15mm BS

410 test sieve is generally used. The ratio of aggregate to lime

by weight is in the range 10 to 20. Their natural colour is off-

white and they are smooth and regular in shape. Coloured

pigments are sometimes added if various colours and textures

are required by mechanical texturing before autoclaving.

Calcium silicate bricks are made to the same standard size as

clay bricks and they are either solid or may have frogs, but not

perforated.

Manufacture of Calcium Silicate Bricks (CSB)

CSB also commonly known as autoclaved calcium silicate-

bonded bricks.

The moulded CSB are hardened in sealed and steam

pressurized autoclaves process. This highly mechanized or

automated process normally takes from seven to ten hours to

allow reaction between the sand and the lime, resulting in a

strong homogenous brick. The performance characteristic of

CSB can be adjusted to suit the requirements by varying the

autoclaving time and the steam pressure.

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Figure 26: Autoclaving kiln

Properties of Calcium Silicate Bricks

BS 187: 1978 specifies certain requirements and they are dimensions,

compressive strength, drying shrinkage and sampling.

The standard gives 6 classes and the higher the numbered class the

stronger is the brick, i.e. loadbearing bricks, facing bricks and

common bricks. The appearance of the loadbearing bricks and facing

bricks must be free from visible cracks and noticeable balls of clay,

loam and lime. For facing brick, it should be of the colour and texture

agreed upon and reasonably free from damage.

Typically the range of mean comp. strengths in general use is 14 to

27.5 N/mm2, depending on the quality of bricks being produced.

Drying shrinkage for common bricks of strength class 2 should not

be more than 0.040 percent. In term of water absorption for calcium

silicate bricks, it varies between about 6 and 16 percent by weight.

Table 3: Compressive strength classes, requirements and colours of calcium silicate

bricks

Designation Class Mean compressive

strength not less than

(N/mm2)

Predicted lower limit of

compressive strength

not less than (N/mm2)

Colour

Loadbearing brick

or

Facing brick

7

6

5

4

3

48.5

41.5

34.5

27.5

20.5

40.5

34.5

28.0

21.5

15.5

Green

Blue

Yellow

Red

Black

Facing brick or

common brick 2 14.0 10.0 -

Source : BS 187 : 1978

Calcium silicate bricks of the appropriate class can be used in all types of brickwork

including underbuilding (i.e. foundation walls and basement walls), external and

internal facework, loadbearing walls, piers and column, and non-loadbearing panel

walls and partitions.

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Table 4: Minimum quality of calcium silicate bricks

Element of construction Minimum quality of bricks

class

Inner-leaf of cavity walls and

internal walls

Unplastered 2

Plastered 2

Backing to external solid

walls

2

External walls including the

outer-leaf of cavity walls and

facing to solid construction

above damp proof course

near to ground level

2

below damp proof course but

more than 150mm above

finished ground level

2

Within 150mm of ground or

below ground

3

External free-standing wall 3

Parapets Unrendered 3

Rendered 3

Sills and copings of bricks 4

Earth retaining walls 4

Source : BS 187 : 1978

SAND CEMENT BRICKS (SCB) - BS 1180 : 1972Material for SCB is Portland cement and sand. Common ratio between

sand and cement is of 6 parts of sand to 1 part of cement by volume,

with max. size of sand passing through a 4.8mm mesh of BS 410 test

sieve. deals with the minimum requirement for these brick.

Manufacture of Sand Cement BricksMoulding of SCB can be done either by hand or by machine. The

machine is operated either electric power or mechanical motor and

incorporated with the pressing machine.

After removal from the machine, the surface of the bricks are normally

scratched and left to be matured on the pallets under shade (stacked in

a separate rows one brick high with a space between each brick).

Normally for the first 24 hours after removal from the machine, the

bricks will be kept wet by watering through a fine spray. Removed

from the pallets after 2 days removal from the machine & allow to

mature for a period of 26 days.

Properties of Sand Cement BricksBS 1180: 1978 has specifies certain requirements for sand cement

bricks for used in walling, and they are dimensions, compressive

strength and drying shrinkage and sampling.

Table 5: Physical requirements

Physical property Compressive strength category

7.0 10.0 15.0 20.0 30.0 40.0

Compressive strength (wet):

average of 10 bricks to be not

less than (N/mm2)

7.0 10.0 15.0 20.0 30.0 40.0

Coefficient of variation of

compressive strength not to

exceed (%)

30 30 30 20 20 16

Drying shrinkage not to exceed

(%)

0.06 0.04 0.04 0.04 0.04 0.04

Source:

BS 1180 : 1978

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CONCRETE BRICKS

Concrete bricks are made from a mixture of inert aggregate and

cement same as calcium silicate brick and are cured in either by

weathering or in an autoclave.

These concrete bricks are harder, more difficult to cut and less

pleasant to handle than clay or calcium silicate bricks and are

less commonly used.

The drying shrinkage varies from 0.019 to 0.080 % of the

length and is greater than that of calcium silicate bricks. BS

6073: Part 1: 1981 deals with the min. requirements for these

bricks and the classification of the types and their properties.

Mortar work is serves to cushion the brick units, giving full

bearing against one another despite their surface irregularities.

The purpose of mortar is:-

- 1. it bonds the bricks together;

- 2. to seal between the bricks against penetration by

air and moisture;

- 3. it adheres the brick units to one another to bond

them into monolithic structural unit;

- 4. accommodates small movements within the wall.

- 5. the appearance of the finished brick wall.

MORTAR MIXES BS 5628: Part 1: 1978.

Figure 26: Mortar

mixture

Mortar is composed of an inert aggregate

(sand) and a binding material of lime or

cement or both.

The proportion of cement and lime in the

binder affects the properties of mortar, and it

can be carried out by volume or by weight.

Most mortar mixes are based on a ratio of 1

binder to 3 aggregate (Figure 26). The

reason is because the air spaces between

particles of sand account for about one

quarter of the total volume.

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Lime Mortar- slake lime mix with sand and water.

Cement–lime is a mixture of cement, lime and sand.

Masonry cement- mixture of OPC and inert pulverized

limestone or hydrated lime.

Mortar is a mixture of sand, cementitious materials and

water used to bond bricks.

Slaking is the chemical reaction that produces hydrated

lime when limestone and water are mixed

CEMENT - Portland cement is the bonding agent in the mortar,

besides providing strength and durability. The type of cement

used will governs the setting characteristics, workability and

the strength development of mortar. More cement produces a

strong mortar and reduces the risk of sulphation as it absorbs

less water.

LIME – Imparts workability, water retention, elasticity and

bond strength. However, if the amount of lime is too much, it

delays the setting of the mortar and walls may be unstable and

liable to wind and other damages. The period of slaking,

composition and strength of mortar depend upon the class of

lime used.

SAND - Sand used must be cleaned and screened to eliminate

particles that are too coarse or too fine. Changes in sand type and

gradation affect the workability of the mortar. Sands deficient in

fines generally produce harsh mortars, while sands with excessive

fines result in weak mortars.

The purpose of sand in mortar is to :-

act as a filler which enhances the strength of mortar;

reduce shrinkage therefore prevent the development of

cracks;

assist in the hardening of pure limes by allowing the

penetration of air which provides CO2 for the development of

carbonization;

control dimensional stability by retaining its shape and

thickness;

reduce cost as sand is cheaper than lime or cement.

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WATER – Is a mixing agent which adds to workability and

without water cement hydration and subsequent setting and

hardening of the mortar would not be possible.

Mortar joint

Is a narrow line with a conventional nominal joint thickness of

10 mm.

It account for over 17% of the surface area of the brickwork.

e.g. in English bond, about 20% of the surface area is mortar,

while bond consisting of all headers the proportion is nearly

25%.

Brickwork is jointed by striking, raking or rubbing the mortar

while it is still ‘green’.

Mortar joints should be finished at the surface with a

consistently shape profile as this also affects the appearance of

the work, i.e. each profile casts a characteristic shadow in

sunlight as can be seen in Figure 27.

A recessed joint casts a dense, bold shadow and darkens the

tone of the brickwork by the darkness in the joint.

A flush joint has no shadow and does not modify the tone of the

wall by this effect.

The concave surface of the keyed joint creates a soft shadow to

the bed joints.

Pointing in brickwork is the finish given to the joints by raking

out to a depth of approximately 13mm to 20mm and then

refilling the joint and the face with a hard setting cement

mortar.

Figure 27: The profile of bed joints view at close distance

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Flush Joint Recessed Joint Weathered Joint Keyed Joint

Weathered Pointing

20mm

Raked Out Joint

20mm

Figure 28: Mortar

Joint Profile

Mortar and grout differ conceptually from concrete in this primary

respects: water content, stiffness of the mix, aggregate size and

permitted cementitious materials.

Grout is a mixture of cementitious material, aggregate and enough

water to cause the mixture to flow readily into cores or cavities in the

brickwork.

Concrete, mortar and grout are all permitted to have OPC and blended

cement as their cementitious materials.

However, mortar may also incorporate lime, which is not used in

concrete and may only be used sparingly in grout.

The brick in a length of wall must be properly bonded in order

to distribute vertical and horizontal loads over a larger area and

so minimize the possibility of differential movement between

bricks, i.e. structural integrity to the wall.

Bonding is part of the bricklayer’s skill in producing a pleasing

appearance, besides ensuring stability of the brickwork.

It is a disposition of brick in a wall designed to ensure that the

cross joint in each course are not less than one-quarter of the

length of the brick from those in adjacent courses.

A bond is usually identified by the appearance of the external

face of the wall.

Bricklaying is an art!

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Figure 29: Header Bond

METHOD OF BONDING

Various methods of bonding are used giving rise to different

bond patterns which have special name.

Header Bond - it has only headers in each course of a wall.

Normally used in the construction of footings and walls with

sharply curve. (See Figure 29)

Stretcher Bond

It has only stretchers in each course of the wall, except at

stopped end of a wall at each alternate course, a half bat brick is

placed. (See Figure 30)

Figure 30: Stretcher Bond

English BondIt has courses of headers alternate with courses of stretchers. In this

bonding, every alternate header in a course sits centrally over the

joint between two stretchers in the joint, except at certain stopped

end. In each heading course a queen closer is placed next to the quoin

header, and the rest will be headers as shown in Figure 31.

Comparatively lack of straight joints therefore it gave this bond as

the strongest of all bonds. Use particularly in civil engineering work.

Figure 31: English Bond

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Flemish Bond – it comprises of alternate headers and

stretchers in each course as shown in Figure 32. There are two

kinds of Flemish bond :-

Double Flemish bond - both external and internal faces of the

wall have the characteristic appearance of Flemish;

Single Flemish bond - it has a facing of Flemish bond with a

backing of English bond. It has a large number of short

continuous vertical joints which occur in the longitudinal

joints.

Figure 32: Flemish Bond

Garden wall bond – Suitable for garden and division, and be

of two forms, i.e. English garden wall bond and Flemish garden

wall bond.

English garden wall bond – it has three or five courses of

stretchers to one course of headers. A queen closer is introduced

next to quoin header in the heading course. A header is placed

at the quoin of each middle (or alternate) course of stretchers to

give a necessary lap and face appearance of the stretching bond

can can be seen in Figure 33.

Figure 33: English Garden Wall Bond

Flemish garden wall bond

It has one header to every three or five stretchers in each course. A

three-quarter bat is placed next to quoin in every alternate course,

and a header is laid over the middle of each central stretcher. (See

Figure 34)

Figure 34: Flemish Garden Wall Bond

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Dutch bond

Consists of alternate courses of headers and stretchers, but

each stretching course begins at the quoin with a three-quarter

bat and every alternate stretching course have a header placed

next to the quoin three-quarter bat. Figure 35 shows the Dutch

bond.

Figure 35: Dutch Bond

TERMS USED IN BRICKWORK

Arris an angle or edge of a brick.

Bed the lower 215mm by 102.5mm surface of a brick when placed in

position, or the underside of the brick.

Header the end or 102.5mm by 65mm surface of a brick and lay with its

length perpendicular to the face of the wall.

Stretcher the side or 215mm by 65mm surface of a brick and lay with its

greatest dimension horizontal and its face parallel to the wall

face.Face a surface of a brick such as a header face and stretcher face; is

also applied to an exposed surface of a wall.

Frog a shallow sinking or indent formed on rather one or both of the

215mm by 102.5mm faces of a brick.

Bed Joints is a horizontal mortar joint parallel to the beds of the brick.

Course a complete horizontal layer of bricks plus its mortar bedding

joint.

Continuous

Vertical Joints or

Straight Joints

it comes immediately over each other in two or more consecutive

courses.

Quoin is a connection form by two walls (a corner or external angle)

which meet at 90o.

Stopped or Closed

End

is a square termination to a wall.

Perpends Is an imaginary vertical lines which include vertical joints and

should be perpendicular or plumb.

Junction in brickwork means a connection between two walls, i.e. T-

junctions and cross- junctions or intersections.

Lap the horizontal distance which one brick projects beyond a vertical

joint in the course immediately above or below it.

Racking back The stepped arrangement formed during construction of a wall

when one portion is built to a greater height than that adjoining.

Toothing each alternate course at the end of a wall projects in order to

receive or to provide adequate bond if the wall is continued at a

later date.

Bat a portion of an ordinary brick with the cut made across the width

of the brick, usually greater than one quarter. There are three types

of bat, i.e. half bat, three-quarter bat and bevelled bats.

Closer a portion of an ordinary brick with the cut made longitudinally.

Common types of closer are queen closer, bevelled closer and

mitred closer.

Queen closer obtained by cutting an ordinary brick into two half bats and

usually placed next to the first brick in a header course.

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Quoin

Racking Back

Heading course

Stretching

course

Toothing

Quoin Headers

Queen Closers Bed Joints

Vertical Joints

Mortar Joints

ArrisesFrog

Header Face

Stretcher FaceBed Face

Figure 27: Terms in Brick and Brickwork

Pilaster also known as attached pier is a thickened wall

section or a vertical support built contiguous with and

forming a part of the brick wall. Used for stiffening brick

walls and to provide all or part of their lateral support. It

functions primarily as flexural member.(See figure 36)

Pilaster

Figure 36: Pilaster

Piers also known as pillars or column in brickwork used to support

concentrated loads or to strengthen walls.

There are many ways that dampness can penetrate into a

building through the brick wall, and they are :-

By the rain beating against the external walls and

absorbed the water to show dampness on the internal

walls.

Moisture rising up the walls at or near to the base by

capillary action and moves up the wall and enter the

building above the ground floor level.

Moisture penetrates down into the head of the wall and

moving down into the building below the roof level.

The above can be overcome by placing a suitable damp-proof

course in the thickness of the wall.

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DAMP PROOF COURSE (D.P.C)

It is An impervious material place horizontally or vertically to

provide a barrier to the passage of moisture from the external

source into the wall of the building or from part of the structure to

another. Damp-proof course (dpc) is normally placed at a

distance of 150mm to 300mm above the ground level

The materials to be used as d.p.c should satisfy the criteria as

stipulated in BS 743, and they are :-

1. should be completely impervious,

2. should be durable and long lasting,

3. should be of thin membrane or sheets so as to

prevent disfiguration of the wall,

4. should be strong to support load imposed on it

without exuding out from the wall,

5. should be of flexible material and able to deflect

accordingly with any settlement without fracturing.

Arrow indicate

weep holes

DPC

G.L

Figure 37: Damp-proof course in brick wall and sills

around timber window.

Table 7: Materials used for damp-proof course

Lead It is very costly but effective damp-proof course. It is very

durable and flexible material and available in rolls of thin sheets

with varying widths, therefore large irregular shapes with few

joints can be produced. However, lead liable to exude under

heavy loadings and should be scratched as it does not adhere

readily to mortar.

Copper It is also a very excellent damp-proof course and should have a

minimum thickness of 0.25mm. Available in rolls of thin sheets,

lapped and jointed as described for lead.

Mastic Asphalt An excellent damp-proof course and it is applied in situ in two

layers with a total thickness of 25mm and it is jointless. This

damp-proof course is impervious, indestructible and does not

fracture if on account of unequal settlement or cracks in the

brickwork.

Bitumen It comes in the form of felt or rolls usually to brick widths and

can be laid quickly with min. number of joints. There are many

varieties available such as hessian, fibre, asbestos & lead which

is impregnated with and covered by a layer of hot natural

bitumen, and sanded on the surface to prevent the layers from

adhering to each other. Should be lapped 75mm where joints

occur and lapped full width at all crossings and angles.

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Polythene It is of low density black polythene sheet of single

thickness not less than 0.5mm thick. It is easily laid,

however care should be taken when lay as it is easily torn

and punctured.

Slate It is very efficient damp-proof course. It is laid in two

courses set breaking the joint embedded in cement mortar

with a minimum length of 230mm long and thickness not

less than 4mm thick. It has limited flexibility and liable to

be broken if unequal settlement occurs, but are

impervious and very durable.

Bricks Effective damp-proof course and are built in two courses

in cement mortar. It should comply with the requirement

of BS 3921.

Metal anchors are positioned in the brick walls to provide

structural integrity of the walls.

It will attach a wall to its supports, either to another wall, floor,

beam, column or other structural support.

Ties are one of the examples of a metal anchor which used to

hold a brick walls together, whilst fasteners attach other

building elements to walls.

Ties must be strong for it purpose, be non-corrodible (copper

or galvanized wrought iron) and normally shape so that water

from the outer leaf of the wall will not pass along them to the

inner leaf.

Figure : Ties

Rectangular tie

with crimp or

drip for cavity

wall

Z-tie for use

with solid

bricks onlyRectangular

tiec. Fixed unit

ties

b. Adjustable brick

ties

a. Twisted cavity ties

Double Triangle Polypropylene

Tie

Twiste

d Butterfly

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Brickwork is reinforced by introducing steel or wrought iron in

the form of flat or rod bars, woven wire or expanded metal. This

reinforcement is placed in joints or in grooves or perforations in

bricks and capable of resisting compression, tensile and shear

stresses.

In order to improves the longitudinal bond of the wall, a

reinforcing metal meshed strips, best known as ‘Exmet’ is

placed at the bed of every third course of the wall height. It is

made from thin rolled steel plates which are cut and stretched by

a machined to a diamond meshwork form.

It is normally used in walls and partitions to resist both

horizontal and vertical pressure.

The strips should lap at intersection and at joint with a lapped of

75 mm.

Brickwork can be reinforced using rod wire reinforcement. It

is used vertically to strengthen walls of reduced thickness and

to resist lateral stresses.

‘Brickforce’ is a welded reinforcement used to improve

resistance of the horizontal pressures occurring from either

side.

‘Wallforce’ is use to strengthen cavity wall. (See Figure 39)

‘Bricktor’ which is a stainless steel or galvanized wire mesh is

used in brick walls to bond and strengthen corners and

intersections of the walls. (See Figure 39)

e. Rod reinforcement

Figure 39: Reinforced brick walls

b. ‘Brickforce’

a. ‘Wallforce’

c. ‘Bricktor’

d.‘Exmet’