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Basic Construction Training Manual for Trainers Heini Müller Basic Construction Tra Basic Construction Training Manual ...

Basic Construction Training Manual

for Trainers

Heini Müller

Basic Construction Tra

Basic Construction Training Manual

ining Manual

for Trainers

MODULE 5 MODULE 4 MODULE 3 MODULE 2 MODULE 1

MODULE 1:

Basic Building Parts ............................................... .........................

MODULE 2:

Building Material and Quality Standards .......................... 19

MODULE 3:

Principles of Construction ......................................... ..... 33

MODULE 4:

Safety ............................................. ......................... 83

MODULE 5:

Earthquake resistant construction practices .................. 89

Various parts of a building (Floor, wall, openings, roof, stair)

Basic Building Parts

MODULE 1

MODULE 1

Basic Building Parts

Content

1. Building ................................. .................................................. ..... 10

1.1. Foundation ................................................. .......................... 10

1.2 Plinth ................................................ .................................................. ........ 11

1.3 Damp proof course (DPC) ........................................... .......................... 12

1.4 Plinth beam ......................................... ......................... 12

1.5 Floor ................................................ .................................................. ......... 13

1.6 Walls ................................ .................................................. ......... 13

1.7 Openings ................................................ .................................................. .4

1.8 Stairs ................................................ .................................................. ........ 15

1.9 Roof ................................................ .................................................. .......... 16

1.10 Surfaces / Finishes .............................................. ... 16

2. Service facilities .............................................. .......................... 17

2.1 water supply ............................................... .......................... 17

2.2 Drainage and sewerage .............................................. .......................... 17

2.3 disposal disposal ............................................... ............................. 17

2.4 Electricity ................................................ .................................................. .7

Basic Construction Training Manual for Trainers

1. Building

A building provides shelter against natural elements such as rain, sunshine and wind. It too

Provides security and privacy. A building consists of the following basic parts:

1.1. Foundation

A foundation is required to even distribute the entire building load on the soil in such a way

That way no damaging settlements will take place. So, the foundations need to be

Built on good / solid ground

The Roof

The Lintel

The Window

The Door

The Cill

The Wall

The Floor

The DPC is at the

Floor Level right below

the Walls (not under any

openings like doors)

The Plinth is between

the Floor and the

Ground

The Foundation is

invisible and lies below

the Ground, just beneath

the Walls

Water Supply

Drainage

Steel reinforcement placing

in foundation excavation

1.2 Plinth

A plinth is normally constructed just above the ground level and immediately after the

foundation. It raises the floor above the ground level and herewith prevents surface water

from entering the building.

Plinth construction height up to ground floor level

MODULE 1

Basic Building Parts

Basic Construction Training Manual for Trainers

1.3 Damp proof course (DPC)

Damp proof course is a layer of water proofing material such as asphalt or waterproof cement.

Walls are constructed above the damp proof course.

Damp proof course prevents surface water from rising into the walls.

Dampness reduces the strength of the walls and creates unhealthy living conditions. Also it

affects the paint and plaster and increasing the cost of maintenance

Damp proofing layer is not required where a plinth beam is constructed, because the plinth

beam already performs like a DPC.

Typical DPC type where no concrete plinth has been constructed

1.4 Plinth beam

A plinth beam is constructed depending upon the type of the structure of the building and

nature of the soil. It provides additional stability in regard to settlements of the building and

earthquake damages.

Completed plinth beam of a building

1.5 Floor

This is the surface on which we do most of our activities. Floorings is laid over the filling of the

plinth and on subsequent floors.

Flooring can be done with different materials, but care must be given that the ground below

the floor is well compacted. Flooring is done to prevent dampness from rising to the top and

to have a firm platform that can be kept hygienic and clean.

Floor construction section, leveling sand, brick layer, cement cover and finishing work

1.6 Walls

Walls are the vertical elements on which the roof finally rests. They can be made of different

materials like bricks, stones, mud, concrete blocks, literate blocks etc.

If the walls are very long, columns can be provided to carry the roof.

Walls provide privacy and enclosure. Walls also provide security and protection against natural

elements such as wind, rain and sunshine.

Openings are to be provided in wall for access and ventilation.

MODULE 1

Basic Building Parts

Basic Construction Training Manual for Trainers

Ongoing brick wall (Rat Trap Bond) construction

1.7 Openings

Openings are normally provided in the walls as door, windows and ventilators.

Doors provide access; windows and ventilators provide light and ventilation.

Building with many windows providing desired ventilation and light

Lintels are constructed just above the openings. It is normally a stone slab or a concrete slab.

Sill is the part of the wall that is just below the window.

Lintels are constructed to hold up the walls above the openings.

In earthquake prone areas a continuous lintel beam is provided all over the walls.

Continuous sill (direct bellow window)

and lintel (direct above window)

1.8 Stairs

A stair is a sequence of steps and it is provided to afford the means of ascent and descent

between the floors and landings.

The apartment or room of a building in which stair is located is called staircase.

The space or opening occupied by the stair is called a stairway.

There are different kind of stairs are used in buildings, like RCC stair, wooden stair, metal stair,

brick stair etc.

External stair construction, provides safe access to roof area

MODULE 1

Basic Building Parts

Basic Construction Training Manual for Trainers

1.9 Roof

The roof provides protection for the building and the people living in it. The roof rests on the

walls and requires proper anchoring so that wind and other mechanical impact cannot destroy

it. A roof can have different shapes but it is always either flat or sloping.

Roof is typically made of RCC, stone slab, tiles etc.

Clay tile covered roofs for rural housing scheme

1.10 Surfaces / Finishes

External finishes are the outer most layer of protection, which protect the structure from

weathering.

Internal finishes are the layers given on internal faces. They give durability and pleasing

appearance to the inside.

Wall plastering and decorative design design

2. Service facilities

2.1 water supply

Water supply facility is provided to provide and distribute clean water inside the building.

This can be done through a network of pipes. Usually pipes used are PVC or GI pipes.

2.2 Drainage and sewerage

This is provided to collect and carry the wastewater away from the building.

2.3 disposal disposal

Garbage should be collected and disposed for creating hygienic living conditions.

2.4 Electricity

Electrical connections are provided to supply power for various needs within the building.

MODULE 1

Basic Building Parts

Building material compilation at site (sand, grave, cement, concrete blocks)

MODULE 2

Building Material and

Quality Standards

Building Material and Quality Standards

MODULE 2

Content

Raw materials for masonry works ... .................. 22

1. Bricks ................................. .................................................. ......... 22

1.1 Classification of bricks .............................................. .............................. 22

1.1.1 Facing bricks ............................................. 23

1.1.2 Solid bricks ............................................. ......................... 23

1.1.3 cavity bricks ............................................. 23

1.1.4 Special shaped bricks ............................................ ........................ 23

1.2 Quality of bricks .............................................. ......................... 23

1.2.1 AA class ............................................. .............................. 24

1.2.2 Soaked bricks ............................................. ......................................... 24

1.2.3 structure .............................................. .......................... 24

1.2.4 Shape and size ............................................ .......................... 24

1.2.5 Soundness .............................................. ......................... 24

1.2.6 Fall test ... .......................... 24

1.2.7 Scratch test ............................................. ... 24

2. Stones ............................................... .................................................. ...... 25

2.1 Classification of stones .............................................................................25

2.2 Quality of building stone ..........................................................................26

2.2.1 Signs of good quality stones.........................................................26

2.2.2 Quality tests ..................................................................................26

3. Concrete blocks.........................................................................................27

3.1 Classification of concrete blocks ..............................................................27

3.2 Quality of concrete blocks ........................................................................27

4. Sand and aggregates................................................................................28

4.1 Classification of sand and aggregates.....................................................28

4.1.1 Course aggregate ..........................................................................28

4.1.2 Sand ..............................................................................................28

4.2 Quality of sand and aggregates ...............................................................28

4.2.1 Sand storage .................................................................................29

4.2.2 Testing the sand quality ................................................................29

4.2.3 Sea sand........................................................................................29

5. Cement ......................................................................................................30

5.1 Setting/Hardening......................................................................................30

5.2 Hydration of cement .................................................................................30

5.3 Different types of cement .........................................................................30

5.4 Type and quality ........................................................................................30

5.4.1 Cement storage.............................................................................30

5.4.2 Use of fresh cement .....................................................................31

5.5 Testing the cement quality .......................................................................31

6. Water..........................................................................................................32

6.1 Type and quality ........................................................................................32

6.1.1 Seawater .......................................................................................32

6.1.2 Collected rainwater from roofs......................................................32

6.1.3 Oils ................................................................................................32

6.2 Water storage ............................................................................................32

6.3 Testing the water quality ..........................................................................32

Basic Construction Training Manual for Trainers

Raw materials for masonry works

The raw materials required for masonry work, together with the skill of the mason are decisive

factors for the final quality of the masonry work. Therefore, it is important that the correct raw

materials are used. Basic know-how about the different required raw materials is essential for

masons as well as supervisors.

The following main raw materials for brick masonry are needed:

n Bricks

n Stones

n Concrete blocks

n Sand

n Cement mortar

n Water

1. Bricks

Bricks must be of good quality and without visible cracks for a load-bearing wall. A hard ringing

sound emitted when two bricks are struck together indicates that they have been burnt satisfactorily.

Generally, the bricks should be true to size and shape, with straight edges and even

surface, so as to facilitate laying them into position without using too much mortar. Inferior

bricks are generally under-burnt and as a consequence are easily broken and are very porous.

These are neither hard nor durable and are incapable of withstanding heavy loads.

Now all over the world, nearly all bricks are roughly the same shape and size – that is approx:

9 x 4 - 1/2 x 3 inches.

1.1 Classification of bricks

These are defined as suitable for general building work having no special claim to give an

attractive appearance. The type in use for most areas in India is classified as Common Bricks.

Pilling up of common bricks at production site, ready for selling

}

1.1.1 Facing bricks

These bricks are thoroughly burned and uniform in color, and having plane rectangular faces

and sharp straight right angled edges. They are used in the exposed face of the brickwork

without any plaster or surface treatment. The bricks must have sufficient resistance to

penetration by rain and weathering agencies. In general they are selected from a number of

bricks. Facing bricks are also used for “Rat Trap Bond” masonry walls.

Facing bricks (second quality) stored at construction site

1.1.2 Solid bricks

A solid brick is a brick with less holes or perforations of 25% of its volume, in which frogs do

not exceed 20% of its volume.

1.1.3 Cavity bricks

A burnt clay hollow block or brick with holes larger than 20mm wide, which exceed 20% of its

volume.

1.1.4 Special shaped bricks

These are usually solid bricks of various shapes suited to a particular construction.

1.2 Quality of bricks

Generally common bricks are grouped into 3 classes:

Description Class 1 Class 2 Class 3

Water absorption Max. 20% Max 20% Max 20%

Crushing strength Min. 105 kg / cm 2 Min. 70 kg / cm 2 Min. 35 kg / cm 2

Building Material and Quality Standards

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Basic Construction Training Manual for Trainers

1.2.1 AA class

Bricks with crushing strength not less than 140 kg / cm 2 are graded as AA class.

1.2.2 Soaked bricks

The strength of a brick decreases by about 25% when soaked in water.

1.2.3 Structure

Brick when broken should be homogeneous in structure, compact and free from holes, cracks,

cracks, air bubbles, lumps, pebbles and stones and particles of lime etc.

1.2.4 Shape and size

The brick should be rectangular with straight and sharp edges. All bricks should be the same

dimensions and no broken corners or edges.

The size of the bricks varies slightly from region to region in India. Standard size is normally

230 x 115 x 70 mm (9 x 4-1 / 2 x 2-3 / 4 inch).

No dimension of a class 1 brick is allowed to vary from 3 mm to the standard size.

1.2.5 Soundness

The quality of a brick is good if there is a clear ringing sound when two bricks are hit

together.

1.2.6 Fall test

Brick should not break when dropped flat on a height of about one meter.

1.2.7 Scratch test

A good burn brick has so hard that the fingernail can not scratch it.

2. Stones

Building stones are derived from various types of rocks that are found in the crust of the earth.

They are natural products and are used directly, except for their rough sizing and dressing,

before being put in a structure.

Stones are or can be used in almost all parts of construction such as foundations, walls, floors,

roofs, as well as for roads, dams etc.

As a rough guide, walls with well fitting stones in cement mortar have strong of about

75% of an equal brick wall, and walls made of rough stones have a power of about 50%

of the same brick wall.

Crushed and broken stones are used in making concrete and artificial stones such as concrete

blocks.

All size bolder stone deposit Sized stone deposit

All size bolder stone try masonry wall Sized stone pillar construction

2.1 Classification of stones

Stones or rocks are divided into three main groups:

n Igneous (Granite)

n Sedimentary (Sand-stone Lime-stone)

n Metamorphic (Slates, Marble, Laterite)

Building Material and Quality Standards

MODULE 2

Basic Construction Training Manual for Trainers

2.2 Quality of building stone

The fundamental requirements of building stones are strength, density and durability combined

with reasonable facility for working. A good building stone must be hard, tough, and compact

grained and uniform in texture and color.

Usually, crystalline and close-grained stones are durable.

2.2.1 Signs of good quality stones

Colour: Stones should have uniform color. Red and brown shades and

mottled color indicates the presence of injurious material.

Weight: Basically, the heavier and compact grained stones are the stronger and

durable they are.

Water absorption: A stone absorbing less water is stronger and more durable as it will

have less action of rainwater.

Appearance: A good building stone should be free from decay, flaws, veins, cracks

and sand-holes

2.2.2 Quality tests

There are several tests possible to define the quality of a stone. However, in the field there are

basically three tests where one can define the suitable quality of a stone.

Hammer test

Take a hammer and check the stone for its sound. A hard ringing sound indicates that the stone

is of good quality and has no major defect such as holes or cracks.

Visible test

Check the stone for any defects such as cracks, patches with soft materials, discoloring etc.

Porosity or absorption test

Weight a stone of reasonable size and place it for 24 hrs. into a water-bucket. A good building

stone should not absorb more than 5% of its weight of water after 24hrs immersion.

3. Concrete blocks

Concrete blocks are nowadays very common and time proofed walling materials. Concrete

blocks can be produced by hand and by machine. Handmade blocks are usually of lower

quality, because machine made blocks are better compacted by a vibrator table. The specific

use of a concrete block defines its size and the quality. Cement and coarse sand with small

size aggregates are used with very low water/cement ratio.

Hollow blocks have better thermal properties than solid blocks of the same material and total

thickness.

Hollow blocks have certain advantages over bricks, they are only about 1 3rd of the weight

of the same number of bricks and they can be laid about four times rapidly and are of ample

strength for all purposes for which ordinary bricks are used except under concentrated loads.

They have the advantages of hollow walls as regards insulation against heat and sound.

Concrete hollow block (CHB) production yard CHB wall construction used in earthquake

resistant house design

3.1 Classification of concrete blocks

Concrete blocks are classified into two main groups;

n Solid blocks

n Hollow blocks

3.2 Quality of concrete blocks

The basic quality requirement of concrete blocks are; strength, uniform in size and to a certain

degree water resistant. A good concrete block is produced and stored under a sunshade,

has an appropriate mix ratio (not more than 1: 6 for hollow blocks and 1: 10 for solid blocks)

contains clean raw materials (sand, aggregates and water) and fresh cement, is properly cured

for 21 days and is handled with care up to the point of use for masonry work.

Description Solid blocks

Hollow blocks

(non load bearing walls)

Hollow blocks

(load bearing walls)

Density >1800 kg/cum >1500 kg / cum >1500 kg/cum

Crushing strength

(after 28 days)

Min. 5 N/mm2 Min.2.8 N/mms Min. 3.5 N/mm2

Building Material and Quality Standards

MODULE 2

Basic Construction Training Manual for Trainers

4. Sand and aggregates

Sand and aggregates are very essential building construction raw materials and deserve special

attention.

4.1 Classification of sand and aggregates

Material retained on a 4.75 mm IS (Indian Standard) sieve is classified as coarse aggregate,

and below that size as fine aggregate or sand. The material passing a 75-micron IS sieve is

generally considered to be clay, fine silt or fine dust in an aggregate.

Sand, which contains 90% of particles of size greater than 0.06 mm and less than 0.2 mm, is

fine sand.

Sand, which contains 90% of particles of size greater than 0.6 mm and less than 2 mm, is

coarse sand.

4.1.1 Coarse aggregate

There are mainly three sources from where coarse aggregates originate namely:

n Natural deposits

n Crushed stones

n Brick aggregates

4.1.2 Sand

There are mainly four types of sand namely:

n Pit sand

n Sea sand

n River sand

n Crushed sand

Pit sand deposit

4.2 Quality of sand and aggregates

The quality of the mortar is directly linked to the characteristics and condition of the sand. Sand

and aggregates must be free from clay, loam, vegetables and any other organic material.

Clay or dirt coating on aggregates prevents adhesion of cement to aggregate, slows down the

setting and hardening process and reduces the strength of the mortar.

Therefore, clay and silt content should not exceed 10%, otherwise the sand needs to be

washed.

4.2.1 Sand storage

The sand should be stored preferably under a shade. The sand should be sufficiently protected,

such that no impurity from animals, agricultural waste, children, trees, etc. is possible.

4.2.2 Testing the sand quality

There are two main sand quality-testing methods, namely:

Visible test

Check the sand for impurities such as organic materials (mud, leaves, roots etc.) Remove them

before using the sand.

Clay and silt content test

The clay and silt content test can be in two ways:

Hand test

The sand sample is rubbed between damp hands. Clean sand will leave the hands only slightly

stained. If the hands stay dirty, it indicates the presence of too much silt or clay.

Bottle test

Take a bottle and fill in the sand until it's half full. Fill in clean water until the bottle is three quarters

full. Shake up vigorously and leave it to settle for about one hour. Clean sand will

settle immediately, silt and clay will settle slowly on top of the sand. The thickness of the clay

and silt layer should not exceed one-tenth or 10% of the sand below.

This test is also called decantation test. This test is not applicable to crushed stone sands !!

Dirty sand should never be used in masonry because it will reduce the adhesive value of the

considerable mortar.

4.2.3 Sea sand

Sea sand is unsuitable for mortar as it contains salts, which attracts and retains moisture. In

addition the salt content in the mortar will produce whitish powder of efflorescence, which

discolors the brickwork or masonry.

Building Material and Quality Standards

MODULE 2

Basic Construction Training Manual for Trainers

5. Cement

Cement is a mixture of 60 to 67% lime, 17 to 25% silica and 3 to 8% alumina, which are

intimately mixed with water to form into a slurry, which is subsequently heated, dry,

claimed and ground to a very fine powder. A small proportion of gypsum is added before

grinding in order to control the rate of setting.

5.1 Setting / Hardening

The terms setting and hardening have different meanings. Setting is the process that changes

has a fluid concrete to a solid but weak state. Hardening is the process by which the weak set

concrete has strength.

5.2 Hydration of cement

When water is added to cement, the cement hydrates and during the chemical reactions, which

take place while the cement is setting, an increase in temperature occurs and a considerable amount

quantity of heat is generated

5.3 Different types of cement

There are total five different types of cements. Cements are classified by their properties and

chemical composition. The names of these five types of cements are:

n Ordinary Portland Cement

n Rapid hardening Cement

n Quick setting Cement

n Blast - Slag Cement furnace

n High Alumina Cement

5.4 Type and quality

For ordinary brick masonry work it is recommended to use ordinary Portland cement. In order

to achieve good mortar in strength and durability, it is important that the following rules and

rules are followed:

5.4.1 Cement storage

Cement can be safely stored in bags for a few months if kept in a dry room. Paper bags are

better for storing than jute bags because paper bags perform better in regard to quality deterioration

due to moisture. During the monsoon time, the cement storage plays an even more

important role, since the relatively higher humidity accelerates the deterioration process of the

cement.

Cement bags should be stored on a raised wooden platform (e.g. timber pallets) about 15 to

20 cm above the floor level and about 30 to 50 cm away from walls.

The cement stack should not be more than 10 bags high. The bags should be placed close

together to reduce circulation of air.

A cement bag should never be opened until its immediate use for mixing.

5.4.2 Use of fresh cement

Ordinary Portland cement, which has been stored for over six months, should not be used for

masonry work.

The average reduction of strength in a 1:2:4 mixes as a result of storage is:

Fresh cement strength 100%

Cement after 3 months, strength reduced by 20%

Cement after 6 months, strength reduced by 30%

Cement after 12 months, strength reduced by 40%

Cement after 24 months; strength reduced by 50%

5.5 Testing the cement quality

The indication of damaged cement is given by the presence of large lumps of set cement.

These lumps of set cement should not be used, not even if screened again.

The freshness of cement can be tested as per following description:

Lump test:

Check the cement for any small or large lumps. Remove them.

Rubbing test:

When cement is rubbed between fingers and thumb it should feel like a smooth powder such

as flour.

Setting test:

If you are uncertain about your cement quality you can make a simple setting test.

Make a stiff paste of neat cement and water and form it into a cake about 75 mm diameter

and 12 to 15 mm thick. The cake should commence to set in about 30 to 60 minutes. In 18 to

24 hours the cake should have hardened sufficiently so that it does not effortlessly scratch the

surface with a thumbnail.

Building Material and Quality Standards

MODULE 2

Basic Construction Training Manual for Trainers

6. Water

The workability of a mortar increases as the water content of the mix is increased. Water

lubricates the mixture. However, increased water content will cause a decrease in strength,

produce cracks (shrinkage) and decrease density.

Therefore, not only the quality, but equally important the quantity of the water is important for

producing a good mortar and brick masonry work.

6.1 Type and quality

Almost any natural water that is drinkable and has no pronounced taste or odor can be used as

mixing water for making mortar cement. Water suitable for making mortar cement, however,

may not be fit for drinking.

6.1.1 Seawater

Seawater should not be used as mixing water for cement mortar.

6.1.2 Collected rainwater from roofs

Rainwater collected from roofs can be used for mixing mortar or concrete.

6.1.3 oils

Various kinds of oil are occasionally present in mixing water. Water mixed with any kind of oil

shall not be used for mixing mortar or concrete.

6.2 Water storage

Water should be stored where no contamination is possible. Water stored in clean drums

or covered tanks are preferred. The time of the water does not affect the

cement mortar quality in any way.

6.3 Testing the water quality

Water of questionable suitability can be used for making cement mortar cubes. The water in

Question should achieve the strength in 7 and 28 days equal to at least 90% of comparable

specimens made with drinkable water.

Bad brick wall construction resulting in coin collapse / damage

Principles of Construction

MODULE 3

Principles of Construction

MODULE 3

Content

1. Principles of mortar ............................................. ........................ 38

1.1 What is mortar? .................................................. ......................... 38

1.2 Type of mortars .............................................. ............................. 38

1.3 cement mortar ............................................... .......................... 38

1.4 Lime mortar ............................................... .............................. 38

1.5 Cement – lime mortar ...............................................................................38

1.6 Mortar sand granulation...........................................................................38

1.7 Mixing mortars ..........................................................................................39

1.7.1 Weight method..............................................................................39

1.7.2 Volumetric method ........................................................................39

1.8 Categorization of mortars and its mix ratio............................................39

1.9 Dos and don’ts ..........................................................................................40

2. Principles of concreting............................................................................42

2.1 What is concrete? 42

2.1.1 Other ingredients ..........................................................................42

2.1.2 Hydration begins ...........................................................................42

2.1.3 The forms of concrete...................................................................43

2.2 Functions and requirements of concrete ingredients.............................43

2.2.1 Functions of cement......................................................................43

2.2.2 Functions of sand ..........................................................................43

2.2.3 Course aggregate ..........................................................................44

2.2.4 Water.............................................................................................44

2.3 Reinforced concrete .................................................................................44

2.4 Reinforcement ..........................................................................................44

2.4.1 Type and characteristics of steel bars ..........................................44

2.4.2 Categories & purpose of reinforcement ........................................45

2.4.3 Basic rules for steel reinforcement ...............................................45

2.5 Type of concrete .......................................................................................46

2.5.1 High strength concrete..................................................................46

2.5.2 Medium strength concrete............................................................46

2.5.3 Low strength concrete ..................................................................46

2.5.4 Mixing proportion of concrete.......................................................46

2.6 Cover in concrete ......................................................................................47

2.7 Requirements of concrete.........................................................................47

2.7.1 Strength.........................................................................................47

2.7.2 Workability.....................................................................................47

2.8 Factors influencing concrete quality........................................................47

2.8.1 Cement..........................................................................................47

2.8.2 Water – Cement ratio....................................................................47

2.8.3 Raw materials................................................................................47

2.8.4 Fineness of fine aggregate............................................................48

2.8.5 Placing the concrete......................................................................48

2.8.6 Compaction ...................................................................................49

2.8.7 Curing ............................................................................................49

2.8.8 Effect of aging ...............................................................................49

2.9 Mixing of concrete ....................................................................................49

2.9.1 Hand mixing ..................................................................................49

2.9.2 Machine mixing ............................................................................50

2.10 Dos and don’ts ..........................................................................................50

2.11 Form work..................................................................................................53

2.12 Removal of the forms ...............................................................................54

Basic Construction Training Manual for Trainers

3. Principles of brick masonry......................................................................55

3.1 Brick overlap between layers ...................................................................55

3.2 Size of bricks..............................................................................................55

3.2.1 Names of parts of a brick..............................................................56

3.3 Rules for joints ..........................................................................................57

3.3.1 Horizontal joints.............................................................................57

3.3.2 Vertical joints .................................................................................57

3.4 Selection of bricks .....................................................................................58

3.5 Brick cuttings .............................................................................................58

3.6 Brick soaking..............................................................................................58

3.7 Maximum brick wall height per day ........................................................59

3.8 Curing.........................................................................................................59

3.9 Pointing ......................................................................................................59

3.10 Most common bonds ................................................................................60

3.10.1 Flemish bond (One brick thick) ......................................................60

3.10.2 Flemish bond (One and half brick thick) ........................................60

3.10.3 English bond (One brick thick) .......................................................61

3.10.4 English bond (One and half brick thick ....................................... ... 61

3.10.5 Rat trap bond ............................................ 62

3.10.6 Stretching bond ............................................. .......................... 63

3.10.7 Header bond ............................................. 64

4. Principles of stone masonry ............................................ ........................ 65

4.1 Stone surfaces ......................................... .............................. 65

4.2 Rules for stone shaping ............................................. ...................... 65

4.2.1 Line stone ............................................. ......................... 66

4.2.2 Cornerstones .............................................. ......................................................... 66

4.2.3 Arch stones .............................. ... 67

4.3 Unequaled masonry rubber .............................................. ...................... 67

4.3.1 Uncaused rubble ............................................. ...................... 67

4.3.2 randomly rubbed ............................................ .................... 68

4.3.3 Coursed rubble ............................................. .................. 68

4.4 How to build with shaped stones ........................................... .................. 68

4.5 Bonding ................................................ .................................................. .... 70

4.6 curing ................................................ .................................................. .......... 70

4.7 Pointing ................................................ .................................................. .... 70

4.8 Dos and don't ............................................ .............................. 71

5. Principles of curing ............................................. ...................... 72

5.1 What is curing? 72

5.2 Type of curing .............................................. .......................... 72

5.2.1 water curing ... 72

5.2.2 Vapor curing ............................................. 73

5.2.3 steam curing ... .......................... 73

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6. Principles of plastering ... .............................. 74

6.1 What is plastering? .................................................. .................. 74

6.2 Requirements of good plaster ............................................. ................... 74

6.3 Types of mortars for plastering ............................................ .................... 74

6.3.1 Cement mortar ............................................. .................. 74

6.4 Number of coats of plaster ............................................ .............................. 74

6.4.1 Background....................................................................................75

6.4.2 Two coat plaster ............................................................................75

6.4.3 Three coat plaster .........................................................................75

6.4.4 Single coat plaster ........................................................................75

6.5 Preparation of background ......................................................................75

6.6 Recommended mortar mixes ................................................................... 76

6.7 Defects in plastering .................................................................................77

6.7.1 Blistering of plastered surface.......................................................77

6.7.2 Cracking.........................................................................................77

6.7.3 Crazing...........................................................................................77

6.7.4 Efflorescence ...............................................................................77

6.7.5 Flaking ...........................................................................................77

6.7.6 Peeling...........................................................................................77

6.7.7 Popping..........................................................................................77

6.7.8 Rust stains ....................................................................................78

6.7.9 Uneven surface .............................................................................78

7. Flooring......................................................................................................79

7.1 What is flooring? .......................................................................................79

7.2 Components of flooring ..........................................................................79

7.2.1 Sub floor........................................................................................79

7.2.2 Floor finish.....................................................................................79

7.3 Types of floors...........................................................................................79

7.3.1 Brick bat floor ...............................................................................79

7.3.2 Concrete floor................................................................................80

7.3.3 Other common types of floors......................................................81

Basic Construction Training Manual for Trainers

1. Principles of mortar

1.1 What is mortar?

Mortar may be defined as a material composed of fine aggregate and cement, which forms a

hardened mass after mixing with water. It is used in the beds and side joints of masonry work,

in order to bind the stones, bricks or blocks together and distribute the pressure throughout

the block-work.

Mortar is further used also for plastering work, pointing work, flooring and topping work.

Good mortar used for masonry consists of cement, sand and water in the correct proportions.

When the materials are freshly mixed, mortars have a plastic consistency, which could be

easily worked with trowels to fill the joints in masonry or to render the surfaces of walls by

plastering etc. By the virtue of the setting properties of the binding material used (cement,

lime) they set and become hard subsequently.

1.2 Type of mortars

Generally there are three common types of mortars in use for masonry and plastering work,

namely:

n Cement mortar

n Lime mortar

n Cement – lime mortar

1.3 Cement mortar

Cement mortar is nowadays the most commonly used mortar for brick as well as stones

or concrete block masonry work. It provides high strength properties. Mix proportion varies

according to requirements of the masonry structure.

1.4 Lime mortar

This is a mixture of quicklime (burnt limestone) and sand in the proportion of 1 part lime and 3

parts sand, in addition to water. Lime mortar was once the principal material used for bedding

and jointing bricks and stones. It is used less frequently now as it develops strength very

slowly and is not easily available in the market.

1.5 Cement – lime mortar

This was the most usual general-purpose mortar comprising 1 part cement 2 parts lime and 9

parts sand. The addition of lime improves the workability and makes it easier to use. Cement

– lime mortar is mainly used for internal work.

1.6 Mortar sand granulation

The sand used for every kind of mortar must be clean and free from clay and other organic

matters.

For getting a proper mortar, the granulation of the sand needs to be correct. Sand without fines

(below 0.5mm) gives a harsh mortar with a low compressive strength and a bad workability.

Cement mortar gives the best result when the sand comprises of the following:

0 - 0.5 mm (60% 0-0.2 mm) 1 part

0.5 - 2 mm 1 part

2 - 4 mm 1 part

1.7 Mixing mortars

The sand is placed on a clean platform; the correct amount of cement is added to it, both, sand

and cement are thoroughly mixed before water is added and the mass gradually worked up into

a plastic condition. The general rule is that sand and cement are mixed dry together at least 3

times before water are added. This is important for achieving the proper plasticity.

Flatten the dry mix with a trowel, if properly

mixed a uniform gray color is visible.

Add water only once a uniform gray color is

visible.

1.7.1 Weight method

Mortar mixtures are also expressed in kg of cement per 1 m3 of cement mortar. For example

PC 250 means that 250 kg of Portland Cement (PC), approx. 1000 liters of sand and 120 liters

of water is used to get about 1 m 3 mortar. This method is mainly used for large constructions

in cities for bridges, hotel and shopping complexes etc.

1.7.2 Volumetric method

Usually on small and rural construction sites the most practical volume batching method is

applied. The volumetric method is a very appropriate way to mix raw materials. Special care

must be given to ensure that the workers measure each time the same volume.

1.8 Categorization of mortars and its mix ratio

Mortars are categorized in mainly three groups, namely:

Group 1

Highly stressed masonry incorporating strong height structural units as used in multistory

load bearing buildings.

Group 1 batching

Cement Sand

1 4

Bucket Buckets

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Group 2

Normal load bearing applications such as external house walls, parapets, and balustrades,

retaining structures, freestanding garden walls and other walls exposed to severe dampness.

Group 2 batching

Cement Sand

1 6

Bucket Buckets

Group 3

Lightly stressed non structural walls

Group 3 batching

Cement Sand

1 8

Bucket Buckets

1.9 Dos and do not

Dos:

Use always-clean sand for mortar.

Why?

Contaminated sand (eg roots, leaves, plastic parts, saw dust, animal and human excreta etc

will not bind with cement, hence it weakens the mortar. Also sand with high percentage of

clay or silt will weaken the mortar, because the clay or silt contains too many fines that need

to be covered by cement for proper binding, hence, the mortar becomes weak.

Sand deposit properly covered and protected from being contaminated

Dos:

Always use fresh and lump free cement for mortar

Why?

Old cement is losing its strength property. E.g. cement that has been stored for about 6

months is gaining 30% less strength than fresh cement. For good masonry work, strength is

important as it influences the overall building quality.

Improperly stored cement results in

loss of quality

Dos:

Always mix the dry ingredients (sand & cement) together before adding water.

Why?

Wet sand particles have the tendency to stick together and are therefore hindering that cement

can cover them. This results in an un-uniform mix that is reducing the mortar quality, because

each sand particle should ideally be fully covered with cement.

Further, adding water together with sand and cement in one go makes mixing the mortar

extremely difficult for the laborers.

Dos:

Always protect the mortar-mixing place from wind, rain and sunshine.

Why?

Wind and sunshine is entraining the water from the mortar and is accelerating the hardening

process before it is being used. This is makes the mortar useless for any purpose. Rain is

adding water and the mortar becomes unusable too.

Don’ts:

Do not use or re-use mortar that has already hardened. As cement mortar sets relatively quickly

(approx. 30 minutes), it should never be mixed in huge quantities.

Why?

In hardened mortar, the hydration process of the cement has started and re-mixing it is

destroying the bond between cement and sand. This bond cannot regain strength again by

simply adding fresh water to the mortar.

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Basic Construction Training Manual for Trainers

2. Principles of concreting

2.1 What is concrete?

In its simplest form, concrete is a mixture of paste and aggregates. The paste, composed of

Portland cement and water, coats the surface of the fine and coarse aggregates. Through a

chemical reaction called hydration; the paste hardens and gains strength to form the rock-like

mass known as concrete. Within this process lies the key to a remarkable trait of concrete: it‘s

plastic and malleable when newly mixed, strong and durable when hardened. These qualities

explain why one material, concrete, can build skyscrapers, bridges, sidewalks and superhighways,

houses and dams. The key to achieving a strong, durable concrete rests in the careful

proportioning and mixing of the ingredients. A concrete mixture that does not have enough

paste to fill all the voids between the aggregates will be difficult to place and will produce

rough, honeycombed surfaces and porous concrete. A mixture with an excess of cement paste

will be easy to place and will produce a smooth surface; however, the resulting concrete is

likely to shrink more and be uneconomical.

A properly designed concrete mixture will possess the desired workability for the fresh

concrete and the required durability and strength for the hardened concrete. Typically, a mix

is about 10 to 15 percent cement, 60 to 75 percent aggregate and 15 to 20 percent water?

Entrained air in many concrete mixes may also take up another 5 to 8 percent.

Portland cement’s chemistry comes to life in the presence of water. Cement and water form a

paste that coats each particle of stone and sand. Through a chemical reaction called hydration,

the cement paste hardens and gains strength. The character of the concrete is determined

by quality of the paste. The strength of the paste, in turn, depends on the ratio of water to

cement. The water-cement ratio is the weight of the mixing water divided by the weight of

the cement. High-quality concrete is produced by lowering the water-cement ratio as much

as possible without sacrificing the workability of fresh concrete. Generally, using less water

produces a higher quality concrete provided the concrete is properly placed, consolidated, and

cured.

2.1.1 Other ingredients

Although most drinking water is suitable for use in concrete, aggregates are chosen carefully.

Aggregates comprise 60 to 75 percent of the total volume of concrete. The type and size of

the aggregate mixture depends on the thickness and purpose of the final concrete product.

Almost any natural water that is drinkable and has no pronounced taste or odor may be used

as mixing water for concrete. However, some waters that are not fit for drinking may be

suitable for concrete. Excessive impurities in mixing water not only may affect setting time

and concrete strength, but also may cause efflorescence, staining, corrosion of reinforcement,

volume instability and reduced durability.

Relatively thin building sections call for small coarse aggregate, though aggregates up to six

inches (150 mm) in diameter have been used in large dams. A continuous gradation of particle

sizes are desirable for efficient use of the paste. In addition, aggregates should be clean and free

from any matter that might affect the quality of the concrete.

2.1.2 Hydration begins

Soon after the aggregates, water, and the cement are combined, the mixture starts to harden.

All Portland cements are hydraulic cements that set and harden through a chemical reaction

with water. During this reaction, called hydration, a node forms on the surface of each cement

particle. The node grows and expands until it links up with nodes from other cement particles

or adheres to adjacent aggregates. The building up process results in progressive stiffening,

hardening and strength development. Once the concrete is thoroughly mixed and workable

it should be placed in forms before the mixture becomes too stiff. During placement, the

concrete is consolidated to compact it within the forms and to eliminate potential flaws, such

as honeycombs and air pockets. For slabs, concrete is left to stand until the surface moisture

film disappears. After the film disappears from the surface, a wood or metal hand float is used

to smooth off the concrete. Floating produces a relatively even, but slightly rough, texture

that has good slip resistance and is frequently used as a final finish for exterior slabs. If a

smooth, hard, dense surface is required; floating is followed by steel toweling. Curing begins

after the exposed surfaces of the concrete have hardened sufficiently to resist marring. Curing

ensures the continued hydration of the cement and the strength gain of the concrete. Concrete

surfaces are cured by sprinkling with water fog, or by using moisture-retaining fabrics such

as burlap or cotton mats. Other curing methods prevent evaporation of the water by sealing

the surface with plastic or special sprays (curing compounds). Special techniques are used for

curing concrete during extremely cold or hot weather to protect the concrete. The longer the

concrete is kept moist, the stronger and more durable it will become. The rate of hardening

depends upon the composition and fineness of the cement, the mix proportions, and the

moisture and temperature conditions. Most of the hydration and strength gain take place within

the first month of concrete’s life cycle, but hydration continues at a slower rate for many years.

Concrete continues to get stronger as it gets older.

2.1.3 The forms of concrete

Concrete is produced in four basic forms, each with unique applications and properties. Ready

mixed concrete. It’s batched at local plants for delivery in the familiar trucks with revolving

drums. Precast concrete products are cast in a factory setting. These products benefit from

tight quality control achievable at a production plant. Precast products range from concrete

bricks and paving stones to bridge girders, structural components, and panels for cladding.

Concrete masonry, another type of manufactured concrete, may be best known for its conventional

8 × 8 × 16 - inch block. Today’s masonry units can be molded into a wealth of shapes,

configurations, colors, and textures to serve an infinite spectrum of building applications and architectural

needs. Cement-based materials represent products that defy the label of “concrete,”

yet share many of its qualities. Conventional materials in this category include mortar, grout,

and terrazzo. Soil-cement and roller-compacted concrete-”cousins” of concrete-are used for

pavements and dams. Other products in this category include flow able fill and cement-treated

bases. A new generation of advanced products incorporates fibers and special aggregate to

create roofing tiles; Shake shingles, lap siding, and countertops. And an emerging market is the

use of cement to treat and stabilize waste.

2.2 Functions and requirements of concrete ingredients

2.2.1 Functions of cement

n It fills up the void in the fine and coarse aggregates.

n Make the concrete impermeable.

n It provides strength to concrete on setting and hardening.

n It binds the aggregates into a solid mass by virtue of its setting.

n Hardens when mixed with water.

2.2.2 Functions of sand

n Sand fills the existing void in the coarse aggregates.

n It reduces shrinkage of concrete

n sand helps in hardening of cement by allowing the water through its voids.

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2.2.3 Coarse aggregate

n It makes solid and hard mass of concrete with cement and sand.

n It reduces the cost of concrete, since it has more volume.

2.2.4 Water

n Water wets the surface of aggregates

n It facilities the spreading of cement over the aggregates and makes the mix workable.

n It initiates the hydration process of the cement, and then starts the setting and

hardening process

n It controls the heat generated by the hydration process of the cement

2.3 Reinforced concrete

Concrete can support heavy loads in compression, but its strong strength is relatively low.

(About one -tenth of the compressive) To compensate for the low tensile power property of

the concrete, steel bars with a very high tensile strength are combined with concrete.

By embedding steel bars in the concrete, advantage is taken of these properties to improve

the load carrying capacity of the structure. The steel is placed in the concrete that is subjected

to tension but also to avoid cracks due to shrinking.

2.4 Reinforcement

2.4.1 Type and characteristics of steel bars

Steel is a high strength material and for reinforced concrete work mild steel, tall medium

steel, high tensile steel and hard drawn steel is commonly used.

Different size of reinforcement & their weights:

Reno. Size of Steel (die in mm) Weight per Rm.

0.22 kg

0.39 kg

0.62 kg

0.89 kg

1.58 kg

2.47 kg

3.85 kg

The various forms in which steel is used as reinforcement in R.C.C. works are round bars,

deformed bars, twisted bars, square bars and flats. Sometimes expanded metal fabrics made

by welding steel wire in the form square mesh, are also used as reinforcement in slabs.

Mild steel and medium tensile steel bars of round sections are most commonly used in R.C.C.

work. The diameters of round bars used in normal building work are 6, 8, 10, 12, 16, 18, 20, 22,

25 and 32 mm.

Deformed bars or high yield strength deformed bars are furnished with lugs, ribs or other form

of surface deformations for the purpose of increasing their bond strength with concrete.

2.4.2 Categories & purpose of reinforcement

There are two main categories and purposes of reinforcement by steel.

The main reinforcement, to take care for the tension forces.

Distribution reinforcement, to spread the load and to keep the main reinforcement in

position during casting.

2.4.3 Basic rules for steel reinforcement

The main reinforcement should always be at the place where tension occurs. It should

adequately covered by concrete to avoid corrosion of the reinforcement. Steel bars of plain

surface (mild steel) need to be hooked at the ends to obtain better adhesion, and therefore

create a greater strength for the structure. Hooking is not necessary for steel bars with ribbed

surface (Tor-steel).

A proper bond between the steel rods and the concrete is the most important for reinforced

concrete. The surface of the rod has to be clean. In order to provide a proper bond the rods

have to be surrounded completely by the concrete. Therefore, the reinforced concrete has to

be properly vibrated. Plain bars must have ends with hooks, which, should be anchored, in

the pressure zone. Deformed bars with ribbed projections can have straight ends but then the

anchorage has to be in the pressure zone of the structure.

If rods have to be overlapped the following rules show the minimum overlap length:

Rod with hook - 45 times diameter of the rod

Straight - 65 times diameter of the rod

Important:

The proper placing of reinforcement for structures of high quality concrete requires a working

drawing or reinforcement plan, containing all the necessary information. A structural engineer

will make this reinforcement plan only.

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Basic Construction Training Manual for Trainers

2.5 Type of concrete

The strength of the concrete depends on mix proportions and should suit the work being done.

Different applications require different strengths of concrete. Three different strength categories

with typical applications are outlined below

2.5.1 High strength concrete (M 300 – M350)

High strength concrete should be used for suspended structural beams and slabs, precast

items (stairs) and heavy-duty floors.

2.5.2 Medium strength concrete (M 200 – M250)

Medium strength concrete is suitable for reinforced foundations and slabs, light duty house

floors, paths, steps, driveways and garage doors.

2.5.3 Low strength concrete (M100 – M150)

Low strength concrete is suitable for unreinforced foundations for houses and freestanding

walls.

2.5.4 Mixing proportion of concrete

Concrete Type Proportion of Cement Proportion of Sand Proportion of Aggregates

M100

M150

M250

M350

2.6. Cover in concrete

An appropriate concrete cover of the steel reinforcement is absolutely essential to protect the

steel members from weathering effects. As soon as air contacts the steel members inside the

concrete, the oxidation process starts, leading to rusting and eventually disintegration of the

affected part. This can lead to serious consequences such as the collapse of a beam or slab.

Minimum requirement of cover in concrete members:

Member’s Minimum reinforcement cover

Slab 150 mm

Beam 25 mm

Column, Foundation 40 mm

2.7 Requirements of concrete

2.7.1 Strength

The concrete must be strong enough to bear the imposed stresses safely in each with the

required factor of safety. It will be uneconomical making the concrete stronger than desired,

but at the same time its minimum strength must be ensured.

2.7.2 Workability

The concrete mix used should be so that it can be easily mixed, placed, compacted and

finished at surface with minimum effort ie the concrete should be workable.

2.8 Factors affecting quality concrete

2.8.1 Cement

The cement quality is a very important factor that influences the basic requirement of the

concrete. Cement must be fresh and free from any lumps. The grading of the cement is

important too. High grade cement, eg Grade 53 is gaining more rapidly than a Grade

33 cement. However, after 90 days, both types of cement will have approx. got the same

final strength.

2.8.2 Water - Cement ratio

The ratio of minimum quantity of water to the weight of cement, required to obtain the desired

consistency and workability of concrete mix is called: water cement ratio. Concrete strength

decreases with the increase in water cement ratio. This is because the added water once

evaporated leaves behind very very small voids. The more voids there are in concrete, the

weak it becomes.

2.8.3 Raw materials

The sand and aggregate must be free of leaves, grass and other foreign issues. Sand should

be fairly coarse with particle sizes ranging from fine dust to about 5mm.

Clean aggregate with sizes of 26.5 mm, 19 mm, 13.2 mm or 9.2 mm can be used for concrete.

Aggregate size of 26.5 mm can be used for thick sections such as foundations, deep suspended

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slabs and industrial thicker thicker than 120 mm. 19 mm aggregates can be used for floors, paths

and driveways. Aggregates 13.2 mm or 9.5 mm can be used for thin concrete section such as

thin suspended slabs, precast items with section thickness ranging from 40 mm to 50 mm.

2.8.4 Fineness of fine aggregate

Concrete strength decreases with increase in fineness of fine aggregate. This is because the

fine require a lot of cement for a total coverage, resulting in a leaner overall mix.

2.8.5 Placing the concrete

Concrete after mixing must be placed in the defined position and compacted before the initial

setting of cement starts.

Before placing of concrete starts, it must be ensured that the forms are rigidly braced, true to

their position, oiled, cleaned and dried of any standing water.

Special care must be taken that before placing the concrete that the steel reinforcement is

properly distanced from the formwork to ensure appropriate coverage of the steel members.

Place the concrete as close to its final position as possible. I f concrete is placed on the

ground, the soil should be thoroughly damp, but without any standing water when the concrete

is placed. Work the concrete right into the corners and along the edges on the form or hole

with a spade or a trowel.

Concrete should never be dropped from a height, as it will cause segregation.

wrong: placing heaps causes segregation

2.8.6 Compaction

It is extremely important that the concrete is thoroughly compacted immediately after placing in

to the forms. Not properly compacted concrete results into so called “honey comb” spots that

expose the steel reinforcement to air and resulting in rusting. Besides, not properly compacted

concrete has a reduced bearing capacity and is overall weakening the casted structure. A

vibrator needle can achieve best compaction.

2.8.7 Curing

After concrete is placed, a satisfactory moisture content and temperature (between 50°F

and 75°F) must be maintained, a process called curing. Adequate curing is vital to quality

concrete. Curing has a strong influence on the properties of hardened concrete such as

durability, strength, watertightness, abrasion resistance, volume stability, and resistance to

freezing and thawing and deicer salts. Exposed slab surfaces are especially sensitive to curing.

Surface strength development can be reduced significantly when curing is defective. Curing

the concrete aids the chemical reaction called hydration. Most freshly mixed concrete contains

considerably more water than is required for complete hydration of the cement; however, any

appreciable loss of water by evaporation or otherwise will delay or prevent hydration. If temperatures

are favorable, hydration is relatively rapid the first few days after concrete is placed;

retaining water during this period is important. Good curing means evaporation should be

prevented or reduced

2.8.8 Effect of aging

Basically if all rules and regulation for concreting are properly followed, concrete gains strength

by aging. However, the rate of increase in strength decreases with time.

2.9 Mixing of concrete

Mixing of concrete is usually made by hand for small quantities or by machine for big

quantities.

2.9.1 Hand mixing

Hand mixing is adopted where in smaller quantities of aggregates is involved or the involvement

or procuring of mixing machines is out of reach. Mixing shall always be done on watertight

platform in order to avoid cement water seepage.

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Procedure for proper hand mixing:

n Spread the measured quantity of sand in a layer of about 10 cm on the mixing platform.

n Place the cement on top of the sand and mix the two thoroughly together until thy form

an even color.

n Pile the mixture into a heap and make a hollow in the middle.

n Pour in water slowly in small quantities and mix until a smooth paste is formed.

n Add now the correct amount of aggregate and mix until every aggregate is properly

coated.

2.9.2 Machine mixing

Machine mixing is required for large quantities of concrete work and for good workability for

placing the concrete in a short time and with no wastage.

Concrete having coarse aggregates is mixed in concrete mixers.

Procedure for machine mixing:

n Measure the quantities of each ingredient

n First add the aggregates and some amount of water, then the cement, then the sand

n Mix and add more water until the right consistency is reached

n Empty the mixer completely when discharging each batch.

n Clean the concrete mixer thoroughly on completion.

2.10 Dos and don’ts

Dos:

Always calculate exactly how much finished concrete is required for the job to do and ascertain

how much cement sand, coarse aggregate and water will be required

Why?

Even a good guess can go wrong. While guessing the amount of material required it can

happen that you order to much, resulting into unnecessary expenses. It might also happen that

you order too less and organizing immediately the remaining material might proof to be difficult

or even impossible, resulting into unnecessary expenses and loss of quality.

Dos:

Use always-clean sand and aggregates for concrete.

Why?

Contaminated sand and aggregate (e.g. roots, leaves, plastic parts, saw dust, animal and

human excreta etc. will not bind with cement, hence is weakening the concreter. Also sand

and aggregate with high percentage of clay or silt will weaken the concrete, because the clay

or silt contains too many fines that needs to be covered by cement for proper binding, hence,

the concrete becomes weak.

Dos:

Always use fresh and lump free cement for concrete

Why?

Old cement is loosing its strength property. E.g. cement that has been stored for about 6

months is gaining 30% less strength than fresh cement. For good concrete work, strength is

important as it influences the overall building quality.

Dos:

Always mix the dry ingredients (sand & cement) together before adding water.

Why?

Wet sand particles have the tendency to stick together and are therefore hindering that cement

can cover them. This results in an un-uniform mix that is reducing the concrete quality, because

each sand and aggregate particle should ideally be fully covered with cement.

Further, adding water together with sand, aggregate and cement in one go makes mixing the

concrete extremely difficult for the laborers.

Dos:

Always protect the concrete-mixing place from wind, rain and sunshine.

Why?

Wind and sunshine is entraining the water from the concrete and is accelerating the hardening

process before it is being used. This is makes the concrete useless for any purpose. Rain is

adding water and the concrete is becoming too wet, resulting in a weak final strength.

Dogs will contaminate concrete raw material, therefore proper protection is required

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Dos

Use the concrete mix within a maximum of 1 hr. after wet mixing and do not ever retempering

by mixing in additional water

Why?

In concrete that is older than 1 hr, the hydration process of the cement has started and remixing

It is destroying the bond between cement and sand / aggregates. This bond can not regain

power again by simply adding fresh water to the concrete.

Dos:

Use always-appropriate quantity measuring boxes.

Why?

Using empty cement bags, gold other means does not always ensure that the correct amount

of raw material is being added. This inaccuracy could lead into leaner or rich mix than

designed, either reducing the concrete quality or adding extra costs.

Dos:

Always make a final check of the formwork before placing the concrete into the form.

Why?

When placing the reinforcement of some supporting pools or bracing may have been

dislocated. If now concrete is pored in the framework, side shuttering or even slab shuttering

may collapse. This is the worst-case scenario, but unfortunately it still happens too often,

sometimes even killing people.

Do not

Do not make concrete work if the outside temperature is crossing 40 degrees Celsius.

Why?

The direct sunshine temperature at 40 degrees Celsius is about 50 degrees Celsius. So,

the water evaporation of the freshly placed concrete will occur immediately, causing serious damage

shrinkage cracks and hindering a proper and controlled hardening of the concrete. This will

finally seriously weaken the concrete work quality.

However, if it is unavoidable to stop concreting work, then the following precautions can be

taken:

n Cooling down the aggregates by water sprinkling

n Providing a shade at the casting side

n Placing immediately plastic on the casted concrete

Don’ts

Do not store the steel bars direct on the ground.

Why?

The steel bars might get dirty and covered with mud. If the mud will not be properly washed

away before concrete casting, the binding of the steel bar with the concrete is reduced,

resulting in a weak structure.

Don’ts

Do not clean the rust of the steel bars.

Why?

An alkaline environment, cement, surrounds the steel bars. The alkalinity of the cement will

clean the rust in a very short time, provided no air is accessing the steel bars.

2.11 Form work

Most structural concrete is made by casting concrete into previously made boxes that are

called forms or shuttering. Usually wall, column, beam and slab forms are built by joining

wooden boards edge on edge. Sometimes plywood may be nailed on since it is tighter and

more wrap resistant. In certain cases metal forms are used, e.g. when a large number of equal

structural members (pre-cast elements) have to be erected or when the parts should be very

exact in measurements.

The most suitable material for formwork is wood, in particular boards, rails, batten and planks.

All this timber is available in various quality and dimension. Hardwood should not be used for

parts where nailing is necessary. Boards of less quality and boards of rough surface do not last

very long as shuttering. Using plastic or metal sheets can extend the reuse.

Steel bars properly stored at

construction site.

All form work material (planks, boards, steel etc.) and elements formwork (moulds) are

sprinkled with water before placing concrete. After striking or dismantling, the formwork is

cleaned and eventually oiled as well as properly stored and protected from sun and rain. This

will guarantee the use of many times.

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Form work for pre-cast products like cover slabs, fence posts, well and culvert rings, and

element form work for standard structures like stand posts should be made of quality timber

or steel. The use of GI sheets as additional reinforcement for timber formwork is very suitable

because nailing of sideboards or batten is still possible

2.12 Removal of the forms

Forms should be left in place until the concrete has hardened enough to hold its own weight

and any other weight it may be carrying. The surface must be hard enough to remain uninjured

and unmarked when care is used in stripping the forms.

Under ordinary circumstances, forms for various types for construction be removed after

intervals as follows:

Side forms on beams, lintels, walls, columns 1 to 2 days

Slabs, lintels, beams

Clear span 3 m and below

Clear span 3 – 6m

Clear span more than 6m

8 to 14 days

16 to 14 days

24 to 35 days

Cantilever constructions

as long as possible but min. 35 days

(because of creeping of the concrete)

3. Principles of brick masonry

The craft of the bricklayer is concerned with embedding bricks in mortar and suitably arranging

them so that the mass, called brickwork conforms to certain requirements such as strength

and appearance. Strength depends a great deal upon the bond.

There are many rules for bonding and they are mainly related to the different bonds such as the

English bond, the Flemish bond or the Rat Trap bond.

Bonding means the arrangements of bricks in such a way that no vertical joint of one course is

exactly over the one below. This means that the brick is laid in such a way that it overlaps and

breaks the joint below.

An un-bonded wall, with its continuous vertical joints, has little strength and stability and such

joints in general must be avoided.

3.1 Brick overlap between layers

The amount of lap is generally half of the length of a brick. The minimum lap is ¼ of the length

of a brick

3.2 Size of bricks

Uniformity in the size of bricks is essential. The correct size of a brick for a proper bonding

should be twice its width plus the thickness of one vertical joint.

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Half Lap Quarter Lap

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3.2.1 Names of parts of a brick

Proper overlap is obtained by using closers.

They are also called Queen closer.

Rowlock course

Rowlock course: Bricks are laid on their

edge, normally used for window sills and

lintels

Soldier course

Soldier course: Bricks are lead on their end,

normally used over windows and for special

effects

Closer

Closer

3.3 Rules for joints

Basically, the mortar joints are the weakest as well as the most expensive part of the masonry.

Therefore, care must be taken to be as economically as possible with all type of joints so not

to make the masonry wall unnecessary weak and expensive.

3.3.1 Horizontal joints

For horizontal joints “Bed joint a thickness of 12 mm is recommended for brickwork to

ensure:

n Leveling of the brick in the mortar bed

n Placing the brick completely in the mortar

n No uneven or incomplete support of the bricks due to stones in the mortar

If the horizontal joints are too thick (more than 15 mm) the result is a waste of expensive

mortar (cement) as well as weakening of the structure.

3.3.2 Vertical joints

For vertical joints “Cross joint and Collar joint” a thickness of 10 mm is recommended for

brickwork. The reduction of approx. 2 mm to the horizontal joints is possible because the

contact area is much smaller at the side than at the bottom. Care must be taken to ensure

that the entire vertical joint is filled with mortar; otherwise the brick masonry wall is prone to

leakages.

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Bed Joint Cross Joint

Collar Joint

Mortar Joint

Basic Construction Training Manual for Trainers

3.4 Selection of bricks

Where good and bad quality of bricks is supplied in one truck load, it is advisable to select first

of all the good quality out of the supplied bricks. This is especially important where bricks are

used for constructing load bearing walls and foundations. Bad quality bricks should generally

not be used for wall construction purpose. However, if it is unavoidable to use bad quality of

bricks, then it should be used in the Flemish double bond brick wall as center fillers.

3.5 Brick cuttings

Before one is cutting a brick it is advisable to look just around and confirm that there is no cut

brick already there. Otherwise, use first the cut bricks available.

In order to avoid too much wastage, only good bricks (without crack) should be cut. The mason

needs to check each brick (sound test with a hammer) and must reject bricks that are faulty.

The correct size to be cut should be marked on the brick. A brick-cutting hammer is the most

suitable tool to cut a brick, avoid cutting bricks with a trowel. The trowel is not meant for

this work.

3.6 Brick soaking

Before brick is placed for masonry work, it needs to be thoroughly soaked in water. The

minimum watering time is 6 hours. Dipping the brick into a bucket water just before placing it

will not be good enough. Essentially, the soaking of bricks is done for two reasons:

Dust

The surface of the brick is always covered with a lot of dust, sometimes-even dirt. If this dust

The dirt layer is not properly removed, the binding between the brick and the mortar will not be

effective, hence the entire brick masonry wall will be weakened and the appearance of cracks

will be very likely.

Soak of Water by Brick

Furthermore, a dry and porous brick will immediately consume the water from the mortar. It is

however exactly this water is required for ensuring the proper hardening and control

setting of the cement. If the cement does not have enough moisture to ensure proper

hydration process the final mortar strength will be considerably reduced and the masonry wall

weakened in general.

3.7 Maximum brick wall height per day

The maximum brick wall height per day should not exceed over 12 to 14 layers. Because

The added weight of each new brick layer (course) needs to be carried by the mortar. The

mortar however needs time to harden and to be able to carry those 12 to 14 layers per

day without developing cracks under this heavy load. This cracks can not be seen; still

they are there and will reduce the total power of the masonry wall.

3.8 curing

A brick wall needs to be cured for at least 7 days. Several times a day, water needs to be

poured over the brick wall. The walls are mostly very exposed to wind and sunshine

the water (moisture) of the wall will be dried out very quickly. However, to gain the right

bearing strength, the mortar needs some moisture content for hardening. So, all brick

Masonry needs regular curing for at least 7 days.

3.9 Pointing

The main reasons for pointing the block or brickwork joints are to increase its

weather resistance and to give a neat looking finish to the work.

Pointing can be carried out as the construction of the brickwork proceeds, using the common mortar in

which the bricks are bedded.

Another method is to finish the masonry work first and then make the pointing work with a 1:2

cement mortar later. The joints must be raked out to the depth of about 1 to 1.5 cm., brushed,

washed and filled with a 1:2 cement mortar.

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3.10.2 Flemish bond (One and half brick thick)

Courses 2,4,6,8 etc. Courses 1,3,5,7 etc.

3.10 Most common bonds

3.10.1 Flemish bond (One brick thick)

3.10.3 English bond (One brick thick)

Courses 1,3,5,7 etc. Courses 2,4,6,8 etc.

3.10.4 English bond (One and half brick thick

Courses 2,4,6,8 etc. Courses 1,3,5,7 etc.

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3.10.5 Rat trap bond

Rat trap bond masonry is a cost effective application of brick masonry that has been popularized

in India by the Architect Laurie Baker in the last 20-30 years. In rat trap wall, the bricks are

placed on edge, thereby leaving a cavity of 4” between the two leaves in case of a 10” thick

wall. The bricks are placed alternate headers and stretchers as in Flemish bond. The rate trap

masonry reduces cost by reducing the consumption of bricks and cement mortar for the same

cubic meter of brickwork.

Where to use Rat Trap Bonded brick masonry ?

Where good quality of bricks is available. Bricks used in a rat trap masonry wall need a

minimum compressive strength of more than 35 kg per square centimeters and the other

properties as per IS 1905-1987.

Advantages

n Compared to a 10” thick solid brick wall, consumption of brick is reduced by 25% in rat

trap.

n Due to reduction in number of bricks, the consumption of cement mortar is also reduced.

n Stability of wall is not affected as the excess material is eliminated from around the

center line.

n Acts as a good thermal insulator due to the cavity in the wall.

n Plastering of the outside face is not needed as well as inside plaster is minimized since

both surfaces are fair faced.

Limitations

n Not a good sound insulator.

The rat-trap bond is a masonry technique that reduces brick and mortar consumption. Bricks

are placed with a 3” cavity between two leaves of brick-on-edge. The cavity provides for

thermal insulation.

Rat trap bond

Courses 2,4,6,8 etc. Courses 1,3,5,7 etc.

Rat trap bond T-Junction

3.10.6 Stretcher bond

Courses 1,3,5,7 etc. Courses 2,4,6,8 etc.

All bricks are placed as stretchers.

Alternate layers start with a half bat.

All joints break at the center of the brick below

Stretcher walls are generally used in half brick walls like partition or compound walls etc.

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3.10.7 Header bond

Courses 1,3,5,7 etc. Courses 2,4,6,8 etc.

All bricks are placed as headers.

Overlap is achieved by laying a three quarter bat in alternative course at the corners

Header bond walls are generally used for footings in foundation and walls curved in

plan.

4. Principles of stone masonry

Evidently for building purpose, a good stone should possess strength, durability, cheapness and

fine appearance. The strength of a stone under compression and cross strain is an important

factor for the weight of the masonry. Floor loads must be supported, resulting in considerable

pressure on the lower course. Therefore, for a given load, the lower the compressive strength

of the stone, the thicker the wall should be for safe loading.

4.1 Stone surfaces

For the proper shaping of stones, it is important to know the different surfaces of the stone.

Face This is the exposed surface of a stone in elevation.

Returned face This is the exposed face to the side elevation e.g. a corner stone.

Bed This is the top or the bottom of a stone. The lower surface on which the

stone rests and the upper surface which supports the stone immediately

above.

Joint (Side) These are the surfaces prepared to meet other surfaces, (e.g. Linestone).

To shape or dress a good stone is not a problem if a man takes the pains to do it.

The stonemason should hammer, dress, shape or cut inequalities which prevents the stone

from facing up with the rest of the wall, or that will interfere with the bedding or fitting of the

next course. Always select the stones making sure that they have no cracks, which could lead

to unexpected breaking off.

In shaping and dressing we classify the different shapes of the stones according to their

purposes.

Line stones

Corner stones

Arch stones

4.2 Rules for stone shaping

Stone shaping must be made by a very experienced stonemason to avoid unnecessary

wastage. He needs to have a good feeling to assess the potential use of each stone. Since

stone handling and cutting is quite an accident prone activity, it is important that basic safety

rules are followed such as:

n Workers shaping stones should always use eye protection glasses and wear good shoes.

n All the stones should be of a size and weight that can be carried by one person only.

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The following general stone cutting and shaping rules are relevant

n Select the stone and then choose the way you want to shape it.

n Cut it first roughly on all sides, if possible according to its natural shape.

n No angle of the face to side surface should be more than 90 degrees.

n Dress the face straight and check it with a square or a straight edge.

n Select the stones, which could be used as corners and shape the reverse face.

4.2.1 Line stones

Cut out the sides to form the beds and the joints. The beds should be such that they can keep

the stone when laid without supports. If the joints and the beds are shaped, the face can now

be produced. Lay the stone down with the intended face up and cut off the high parts with a

chisel, bush hammer etc. to a plain surface. Use a straight edge to check the surface.

4.2.2 Cornerstones

Cornerstones are the stones placed at the external angle of a building and prepared to bond

with other stones in the wall in each direction. In any building good corners are essential

therefore good cornerstones must be used for easy plumbing.

A good cornerstone must have good arises and the two faces must be squared to each

other.

Cut first the beds and the joints and give particular attention to the returned face. If the joints

and the beds are well prepared, lay the stone with the intended face up, shape it and make

sure that it is straight by using a straight edge.

Then shape the returned face by chiseling and squaring it to the face. Care must be taken not

to damage the arises.

4.2.3 Arch stones

Unlike the cornerstone the arch stone is shaped like a wedge and is more difficult to shape than

any other stone, because it has to be shaped to specific measurements and dimensions.

First cut out the beds to the required height of the arch. Then cut the joints and form the

wedge, giving special attention to the dimensions required. Finally cut out and shape the face,

checking it with a straight edge.

4.3 Unsquared rubble masonry

Stone masonry may be classified in various ways, as for instance, according to the kind of

stones used, surface finished, bonding etc.

Masonry rubber is composed of unsquared stones. They are found in a quarry or are dug and

broken out of the field, the irregularities being made up by filling with mortar, as the stones

are set. The quarried variety is preferable because they approach almost almost rectangular

shape and is better for stonework because their faces are sharper and form a better hold for

the cement than the weather worn and smoother surfaces of fieldstones. However, fieldstones

are much used in the building of houses

There are three kinds of masonry rubble known as:

n Uncrowed rubble

n randomly rubbed

n Coursed rubble

4.3.1 Unloaded rubble

This kind of masonry covers all kinds and all sizes of stones in which faces, joints and beds

are roughly shaped.

No special attention is given to the level of the courses.

With a good surface finish (joint finish, joints flash) an attractive wall will result.

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4.3.2 randomly rubbed

In this kind of rubble masonry all the stones, which are used, beds, joints and faces are well

shaped. In laying the stone special attention is required to bring each race to as close to the level

as possible.

The difference of unconditionally and randomly rubbed can be seen in the surface finish.

In randomly rubble smaller stones are used than in uncoursed rubble.

4.3.3 Coursed rubble

In particular, it is given shaping the stones. The faces are roughly

squared and the height of all the stones should be almost the same. Special attention by laying

of the stones are given to the bonds, the height of each race and a proper alignment.

4.4 How to build with shaped stones

n The normal procedure to build a stone wall is such that it involves two masons working

one at each face of the wall.

n The bottom or footing course should be laid with the larger, straightest stones since the

stability of the wall depends on the bearing of stones on the ground.

n First the corners of the wall are up to a height of about 1m, making sure that outer

and inner faces are plumbed and squared.

n The corners must be of large stones that will bond the two walls together in the best

way to resist strain. Additional strength may be given to the wall by the addition of

galvanized iron or wire bonds, especially if small stones are used.

n When the corners are up, the building can now continue by fixing two lines (rope) in and

outside the wall. The purpose of those lines is to guide the masons during laying, and

they should be 2 mm away from the face of the wall. The shaped line stones are then laid

in a mortar-bed to the line and then checked for alignment.

n Instead of shaping a stone’s bed, which does not bed firmly, “spalls” or pieces broken off

in trimming can be slipped under the stone. It is easier than the painful labour involved

in handling, trimming and correct setting. Though contrary to the best practice, if these

spalls are correctly used and set in mortar so as to actually support and hold the stones

that they can not move or be displaced, it simplifies the making of a rubble wall and

proves much satisfaction for an ordinary building.

n After a thorough check small stones (spalls) are laid into the interior cavities and filled with

mortar to tie the two faces (lines) together. These interior cavities are known as hearting.

n Bond stones (trough stones) should cover the thickness of the wall at frequent intervals of

not over 1.50 m. Their ends should be dressed to conform to the wall on either side.

Minimum length of a bond stone is 1/3 of

the wall thickness

Bond stones or through stones provide

stability to the masonry wall

Bad example, stone wall construction

without bond stones

Bad example, stone wall construction with

too many small stones and no proper bonds

n Dirty stones must be brushed (iron brush) and washed clean before laying them into

mortar because the dirt prevents adhesion between the stone and mortar.

n The stones should be wet before laying them into mortar.

n Use up all sizes and shapes of stones to the best advantage and the least cutting by

sorting and placing them at the same time preserving the strength and the quality of the

wall, and bring each to as near a level as possible.

n A lone stone needs uniform bedding. If it is too long, break it and lay it as two stones.

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n Spread the mortar, force the stone to its bed without its touching the stone underneath,

and maintain a perfect alignment with the face of the wall. The thickness of the joint

between two stones is equal a flat hand (2 – 2.5 cm).

n After building up the wall in stages, cover it with cement bags or plastic to protect the

mortar against sun and rain.

4.5 Bonding

In stonework too it is important to secure a proper bonding. In bonding the following rules

should be strictly observed:

n Headers should extend not less than 2/3 the thickness of the wall.

n The vertical joints of each course should break with the joints of the course below.

n The largest stones should be used for the lowest courses!

n Stratified stones should be laid on their natural beds (Sandstones).

4.6 Curing

The walls are mostly very much exposed to wind and sunshine and the water (moisture) of

the wall will be dried out very quick. However, to gain the appropriate bearing strength, the

mortar needs certain moisture content for hardening. Therefore, a stone masonry wall needs

to be cured for at least 7 days. Several times a day, water needs to be sprinkled over the stone

masonry wall.

4.7 Pointing

The main reasons for pointing the surface of the stone masonry wall or joints are to increase

its weather resistance and to give a neat looking finish to the work.

Pointing can be carried out as construction of the stone masonry work proceeds, using ordinary

mortar in which the stones are bedded.

Another method is to finish the stone masonry work first and then make the pointing work

with a 1:2 cement mortar later. The joints must be raked out to the depth of about 1 to 1.5 cm.,

brushed, washed and filled with a 1:2 cement mortar.

4.8 Dos and don’ts

Dos

Use mortar in stone masonry as economical as possible.

Why?

Mortar is expensive and is also the weakest part in the stone masonry wall.

Don’t

Do not build up a stone masonry wall higher than 1.00 m per day

Why?

The heavy weight of the stone needs to be carried by the lowest mortar joint. If the mortar is

not properly hardened, it will develop cracks if the weight becomes too much, resulting in a

weak masonry wall

Don’t

Do not partly lift up the stone after placing into the mortar bed for final adjustments with small

stones or additional mortar.

Why?

While partly lifting up the stone and placing additional mortar or small stone pieces a gab will

be created between the stone and the mortar bed resulting in a very week stone masonry

bonding. The correct procedure is to remove the entire stone and place additional mortar so

that the entire stone be is again covered in mortar.

Don’t

Do not level at the end of the day the stone masonry wall with mortar.

Why?

The next morning new mortar will be placed on top of the old mortar. This old mortar is anyway

not properly cured and most likely very weak. Hence, this joint becomes a weak spot in the

stone masonry wall.

Don’t

Do not allow anyone to stand on the fresh wall

Why?

A person standing or much worse, working on top of a stone masonry wall will disturb the

mortar joints while moving. This will create cracks as well as gabs between the stones and the

mortar, resulting in a very weak stone masonry wall.

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5. Principles of curing

5.1 What is curing?

Curing must be made with every building material, construction part or product that is using

cement as part of the raw material. This is because Cement requires water to initiate the

hydration process and to control the internal temperature generated by this process in order

to obtain optimal hardening and strength of the cement. This internal temperature controlling

with water is called curing.

Uncontrolled hydration process initiated temperatures will lead to overheating of cement and

a very substantial loss of hardness and final strength of the cement product such as concrete,

mortar etc.

Good curing means evaporation should be prevented or reduced

5.2 Type of curing

There are generally 3 main type of curing used in the construction sector, namely:

n Water curing

n Vapor curing

n Steam curing

5.2.1 Water curing

Water curing is the most commonly used practice. It is the system that is most appropriate for

house construction and does not require any special infrastructure or skill.

However, water curing requires a lot of water, which is not always easy at hand and might be

even expensive.

Water tank curing method. Cement products are only partly immersed into water,

resulting into loss of quality

In order to economize on water it is important that all measures are taken to prevent water

evaporation of cement products. E.g. concrete must be protected from direct sunshine and

winds to prevent rapid water evaporation. Methods such as covering the concrete with wet,

earth, sand, sawdust, grass and leaves are inexpensive, still quite effective.

Further, plastic, jute bags, hessian clothes too are common used material to prevent rapid

water evaporation of cement products. Wood forms left in place also furnish good protection if

they are loosened and flooded with water at frequent intervals.

Is of paramount importance that the entire cement product (concrete, stone masonry, brick

masonry, plaster work, cement flooring work etc.) is kept wet and that it does never fully dry

out, otherwise the final strength of the cement product will suffer. If the hydration process

has prematurely ended due to overheating (no curing), sprinkling water onto the fully dried

out cement product will not reactivate the hydration process, the loss in strength will be

permanent.

In water curing, the cement product must be kept fully wet for at least 7 days. After 7 days, the

cement product should be regularly sprinkled with water for additional 14 days.

5.2.2 Vapor curing

Vapor curing is done where water is scare and cement based prefabricated elements such as

toilet slabs, tiles, stairs, beams etc are mass-produced. Vapor curing reduces the curing time

compared with simple water curing of about 50 to 60%.

The principle of vapor curing is to keep the cement product in a humid and hot environment

that allows the cement to gain strength in a much quicker way then with simple water curing.

To create this humid and hot environment a simple chamber with water retaining walls and

floor needs to be constructed which is covered with plastic to allow the sunshine to heat the

chamber up and prevents the water from evaporating. A floor water level of about 5 to 7 cm is

to be kept all the time to keep the vapor system working.

5.2.3 Steam curing

Steam curing is normally used in only sophisticated industrial plants that produce mass

cement based produces. A steam curing system is expensive and requires a lot of energy to

generate the required heat required for the steam.

However, steam cured products can be used after approx. 24 to 36 hrs. after production,

providing distinctive advantage over all other curing systems.

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6. Principles of plastering

6.1 What is plastering?

Plastering is the process of covering rough surfaces of walls, columns, ceilings and other

building components with thin coat of mortars to form a smooth surface surface. The coating

of mortar is called plaster.

Plastering is done to achieve the following objects:

n To protect the outer surfaces against penetration of rainwater and other atmospheric

agencies.

n To give smooth surface in which dust and dirt can not lodge.

n To give decorative effect.

n To protect surfaces against vermin.

n To conceal inferior materials or defective workmanship.

6.2 Requirements of good plaster

The plaster material should fulfill the following requirements:

n It should stick to the background, and should remain adhered during all variations in

seasons and other atmospheric conditions.

n It should be hard and durable.

n It should possess good workability.

n It should be possible to apply it during all weather conditions.

n It should be cost effective.

n It should effectively check penetration of moisture.

6.3 Types of mortars for plastering

The selection of type of plaster depends on the following factors:

n Availability of binding materials.

n Durability requirements.

n Finishing requirements.

n Atmospheric conditions and variations in weather.

n Location of surface (ie exposed surface or interior surface).

6.3.1 Cement mortar

Cement mortar is the best mortar for external plastering work since it is practically nonabsorbent.

It is also preferred to lime plaster in both rooms etc., and in damp climates. Cement

mortar is much stronger than lime mortar. The mix proportion (i.e. cement:sand) may vary from

1:4 to 1:6. Sand used for plastering should be clean, coarse and angular.

Cement plaster is applied either in two coats or in three coats, the former being more common.

For inferior work, single coat plaster is sometimes provided.

6.4 Number of coats of plaster

The background over which plastering is to be done depend upon the type of wall construction,

such as random rubble (R.R.) masonry, coarsed rubble masonry, brick masonry

6.4.1 Background No. of Coats

Stone work 3 or 2

Brick work or hollow blocks 2 or 1

Concrete cast in situ 2 or 1

If plastering is done in single coat only, its thickness should not exceed 12 mm nor should it

be less than 6 mm.

6.4.2 Two coat plaster

The following procedure is adopted:

n The background is prepared by raking the joint to a depth of 20 mm, cleaning the surface

and well-watering it.

n If the surface to be plastered is very uneven, a preliminary coat is applied to fill up the

hollows, before the first coat.

n The first coat or rendering coat of plaster is applied, the thickness being equal to the

specified thickness of plaster less 2 to 3 mm. In order to maintain uniform thickness

of plaster, 15 cm x 15 cm size. Two dots are so formed in vertical line, at a distance of

about 2 m, and are plumbed by means of a plumb. A number of such vertical screeds are

formed at suitable spacing. Cement mortar is then applied on the surface between the

successive screeds and the surface is properly finished.

n Before rendering hardens, it is suitably worked to provide mechanical key for the final

or finishing coat. The rendering coat is trowelled hard forcing mortar into joints and over

the surface. The rendering coat is kept wet for at least 2 days, and then allowed to dry

completely.

n The thickness of final or finishing coat may vary between 2 and 3 mm. Before applying

the final coat, the rendering coat is damped evenly. The final coat is applied with wooden

floats to a true even surface and finished with steel trowels. As far as possible, the

finishing coat should be applied starting from top towards bottom and completed in one

operation to eliminate joining marks.

6.4.3 Three coat plaster

The procedure for applying three-coat plaster is similar to the two-coat plaster except that an

intermediate coat, known as floating coat is applied. The purpose of this coat of plaster is to

bring the plaster to an even surface. The thickness of rendering coat, floating coat and finishing

are kept 9 to 10 mm, 6 to 9 mm and 2 to 3 mm respectively. The rendering coat is made rough.

The floating coat is applied about 4 to 7 days after applying the first coat. The finishing coat

may be applied about 6 hours after the application of floating coat.

6.4.4. Single coat plaster

This is used only in inferior quality work. It is applied similarly as two-coat plaster except that

the rendering coat, as applied for two-coat plaster, is finished off immediately after it has sufficiently

hardened.

6.5 Preparation of background

For plastering new surfaces, all masonry joints should be raked to a depth of 10 mm in brick

masonry and 15 mm in stone masonry for providing key to the plaster. All mortar droppings

and dust, and laitance (in case of freshly laid concrete) should be removed with the help of stiff

wire brush. Any unevenness is levelled before rendering is applied. For finish applied in three

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coats, local projections should not be more than 10 mm proud of general surface and local

depressions should not exceed 20 mm. For two-coat plaster, these limitations are 5 mm and

10 mm respectively. The surface should be washed with clean water and kept damp uniformly

to produce optimum suction. In no case should the surface be kept so soaked that it causes

the green mortar to slide off, or so dry that it causes strong suction which withdraws moisture

from mortar and makes it weak, porous and friable. If plaster is to be applied on old surface,

all dirt, scool, oil, paint etc. should be cleaned off. Loose and crumbling plaster layer should be

removed to its full thickness and the surface of the background should be exposed and joints

properly raked. The surface should be washed and kept damp to obtain optimum suction.

6.6 Recommended mortar mixes

Situation Composition of Mortar

I.S. Grading

of Lime

1 External Plaster in localities where rainfall is less

than 500 Mm per year and where sub- Soil water

is not within 2.5 m Below the ground surface:

(a) Below D.P.C. 1 cement 6 sand -

1 cement 2 lime 9 sand B or C

1 lime 2 sand A

1 lime 1 sand 1 surkhi B or C

1 lime 2 surkhi B or C

(b) Above D.P.C. 1 cement 2 lime 9 sand B or C

1 lime 2 sand A

1 lime 1 surkhi sand B or C

1 lime 2 surkhi B or C

2 External plaster in localities where rain fall is

more than 1300 mm per year and where subsoil

water is not within 2.5m below ground surface:

(a) Below D.P.C. 1 cement 4 sand -

1 cement 1 lime 6 sand B or C

1 lime 2 surkhi B or C

(b) Above D.P.C. 1 cement 2 lime 9 sand B or C

1 lime 2 sand A

1 lime 1 sand 1 surkhi B or C

1 lime 2 surkhi B or C

3 External plaster in localities where the subsoil

water is within 2.5 m of the ground

Below D.P.C. 1 cement 3 sand -

4 Internal plaster in all localities 1 lime 2 sand A

1 lime 1 surkhi 1 sand B or C

1 lime 2 surkhi B or C

1 cement 2 lime 9 sand B or C

Note: the ratio of lime varies with % purity of lime and these ratios may be suitably adjusted

depending upon local practice.

6.7 Defects in plastering

The following defects may arise in plasterwork:

6.7.1 Blistering of plastered surface

This is the formation of small patches of plaster swelling out beyond the plastered surface,

arising out of late slaking of line particles in the plaster.

6.7.2 Cracking

Cracking consists of formation of cracks or fissures in the plaster work resulting from the

following reasons:

n Imperfect preparation of background.

n Structural defects in building.

n Discontinuity of surface.

n Movements in the background due to its thermal expansion or rapid drying.

n Movements in the plaster surface itself, either due to expansion (in case of gypsum

plaster) or shrinkage (in case of lime sand plaster).

n Excessive shrinkage due to application of thick coat.

n Faulty workmanship

6.7.3 Crazing

It is the formation of a series of hair cracks on plastered surface, due to same reasons which

cause cracking.

6.7.4 Efflorescence

It is the whitish crystalline substance that appears on the surface due to presence of salts in

plaster-making materials as well as building materials like bricks, sand, cement etc. and even

water. This gives a very bad appearance. It affects the adhesion of paint with wall surface.

Efflorescence can be removed to some extent by dry brushing and washing the surface

repeatedly.

6.7.5 Flaking

It is the formation of very loose mass of plastered surface, due to poor bond between

successive coats.

6.7.6 Peeling

It is the complete dislocation of some portion of plastered surface, resulting in the formation

of a patch. This also results from imperfect bond.

6.7.7 Popping

It is the formation of conical hole in the plastered surface due to presence of some particles,

which expand on setting.

Principles of Construction

MODULE 3

Basic Construction Training Manual for Trainers

6.7.8 Rust stains

These are sometimes formed when plaster is applied on metal laths.

6.7.9 Uneven surface

This is obtained purely due to poor workmanship.

7. Flooring

7.1 What is flooring?

The layer that separates the ground from the floor finish is called the flooring.

7.2 Components of flooring

n Sub-floor (also called base)

n Floor Finish

7.2.1 Sub floor

This is the waterproofing layer

It prevents water from seeping up from the ground to the floor.

It also provides the solid bedding for the final finish. Thus, it must be

n Solid and hard, dense

n Waterproof

n Absolutely level

7.2.2 Floor finish

This is the visible and usable floor. Thus, it must be:

n Easy to clean

n Resistant to dampness

n durable with long life

n hard

n Easy to maintain

7.3 Types of floors

7.3.1 Brick bat floor

Materials used

n Brickbats as bedding layer (55mm)

n sand in between brickbats

n Cement mortar (1: 4) (20mm)

n Cement slurry finish

Principles of Construction

MODULE 3

Basic Construction Training Manual for Trainers

Laying bricks into a bed of

sand

Placing the cement mortar

Filling the brick joints with

wet sand

Cleaning the frog of the

brick from wet sand for

better binding

Prepare the floor top finish Brick bat floor example

completed

Advantages:

n Cheap

n durable

n Easy to clean

Disadvantages:

• n Not 100% waterproof

• n needs good workmanship

n Not very resistant to impacts.

7.3.2 Concrete floor

Materials used:

• n Cement - 1

• n Sand 2

• n aggregate 4

• n Mortar of 1: 2 Cement: Sand mix is used for the finishing coat.

The thickness of theor is normally 1½ ".

For the bedding layer, two alternatives cn be used:

• n Brickbats in 1: 6 mortar cement (3 ")

• n Lean Concrete Bed - 1: 4: 8 (3 ")

Notes:

• n The aggregate would be a mix of 12 mm and 6 mm down down chips in ratio of 1: 1, for

the 1½ "floor of 1: 2: 4 PCC.

•n PVC / Glass strips are inserted to form grids of max. 1m × 1m. These strips are inserted

in the Concrete Floor. The purpose is to make joints, to avoid large expanses of unjointed

floors. This helps in avoiding cracks, which may otherwise form due to temperature

variations.

Advantages of IPS Flooring:

•n Reasonable Cost

•n Very hard and durable

•n No need to procure different materials

•n Easy to clean and maintain

•n Attractive colors can be added to give colored flooring, patterns etc.

Disadvantages:

•n Surface cracks appear in areas of high temperature variation.

7.3.3 Other common types of floors

Type Materials for Floor Finishing Where used Normally

Stone Slab Flooring

(Rough)

Kota Stone Cuduppah

Stone etc. (mainly

sandstones)

Rough Outdoors in Paving etc.

Stone Slab Flooring

(Polished)

Sand Stones:

Kota, Marble Cuduppah

etc.

Polished Indoors, cost ranges from

Rs. 30 - Rs. 100 / sft can be

used in toilets etc.

Mosaic or Terrazzo Marble/hand stone

chips are used as

aggregates in mix of

1 : 2, laid in base of

1 : 3 Cement sand

mortar

Polish with

carborundum stone

and wax

Anywhere, mostly

indoors

Ceramic Tiles Ceramic tiles laid on

1 : 3 cement mortar

Pre-polished Wet areas, and on toilet

/ kitchen dados.

Principles of Construction

MODULE 3

Children using construction site as play ground

Safety

MODULE 4

Safety

MODULE 4

Content

Principles of safety ............................................................................................86

1. Introduction...............................................................................................86

2. Rules to prevent accidents:......................................................................86

2.1 General rules: ............................................................................................86

2.2 Storage.......................................................................................................88

2.3 Conduct ......................................................................................................88

2.4 Working conditions ...................................................................................88

2.4.1 Cleanliness, hygiene & resting place:............................................88

Basic Construction Training Manual for Trainers

Principles of safety

1. Introduction

“Accidents do not happen,

accidents are made” .

The main reasons for construction related accidents are carelessness, technical faults, inappropriate

use of tools, wrong reaction of workers, abuse of alcohol, and most important no proper

awareness about potential sources of accidents.

A construction site is the place where people come to work together mainly to earn money

to support their families. A place where people come together for doing a living must be safe;

no economical consideration justifies an accident. What a great tragedy for a family, if for the

reason of a preventable working accident, no more income is available.

Knowing the sources of potential and predictable accidents means that we can prevent them.

It is the duly of a construction supervisor to know the potential sources of accidents and to

prevent them as far as possible.

2. Rules to prevent accidents:

2.1 General rules:

n Only professionals should make electrical installations.

n No electrical wires would be allowed to lie free on the ground.

n No person without a valid license must be allowed to drive a tractor, truck or any other

vehicle at the construction site.

n No fire will be made at the construction site.

n No ladder with default structural should be used. The supervisor is responsible for order

its repair and maintenance.

n Erect ladders in places where people do not have to walk underneath them.

n When you go up or down a ladder, always face the ladder.

n Do not leave discarded timber with sticking out nails. Shuttering timber must always be

collected and stored in one place.

n Special care needs to be taken for scaffolding work. The scaffolding material needs to be

strong and well fixed.

n Scaffoldings need to be checked every day by the supervisor.

n Floor openings and floor holes must be covered or protected by a guardrail.

n Proper access path with side railings (claim stairs) needs to be constructed for carrying

material from ground level to higher elevations.

n Always bend down or cover the ends of vertical steel bars that stick out of concrete.

n Weights more than 50 kg. should not be carried by one person alone.

n Lifting stones, cement and other heavy building materials should not be made with a bent

back. Always lift the weight with a straight back.

n Prevent any material from falling down that could hurt people or could damage other

building materials.

No proper working platform for wall

painting made, workers at increased

risk of serious accident

Safety

MODULE 4

Scaffolding not properly protected

from vehicles, workers at increased

risk of serious accident

Basic Construction Training Manual for Trainers

2.2 Storage

n Storage of explosive and health hazardous materials should not be allowed at the

construction site.

n Bricks or blocks will not be piled up higher than 1 m at the storage as well at the

construction site.

n Material such as steel bars, timber, sand and cement should be stored in such a way, that

access to the construction site is not blocked.

2.3 Conduct

n No alcohol consumption should be allowed at the construction site.

2.4 Working conditions

n For night work, proper lighting arrangements need to be in place.

n For stone cutting and chiselling works, the workers need to be instructed how to avoid

eye injuries

2.4.1 Cleanliness, hygiene & resting place:

n A person shall be made officially responsible for the cleaning of the construction site.

n A toilet, separate for men and women must be provided for the construction workers.

n The construction site should be kept clean. Workers need to be instructed that the toilet

must be used and that no urination is allowed inside the construction.

n A resting-place official protected from rain and sunshine should be established at site.

n Clean drinking water should be provided at the resting place as well as at the working

place.

n mothers who attend to their children should do so at the official resting place only.

Pavement blocks dangerously piled

up, workers at increased risk of

accident

The rest of one story story collapsed during earthquake

Earthquake resistant

construction practices

MODULE 5

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