Building Materials and Concrete Technology Unit I

NRI INSTITUTE OF TECHNOLOGY DEPARTMENT OF CIVIL ENGINEERING
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B U I L D I N G M A T E R I A L S A N D C O N C R E T E T E C H N O L O G Y
UNIT I{CO 1}
Stones: Classification of Stones – Properties of stones in structural requirements
Bricks: Composition of good brick earth, various methods of manufacturing of bricks
Tiles: Characteristics of good tile – Manufacturing methods, Types of tiles
Wood: Structure – Properties – Seasoning of timber – Classification of various types of
woods used in buildings – Defects in timber
Paints: White washing and distempering, Constituents of paint – Types of paints –
Painting of new and old wood – Varnish
Unit-I
S.No Short Answer Questions CO PO BTL Marks
1 Elaborate the Classification of Rx? 1 1,2,8 VI 7
2
What are the qualities of good building stones?
Discuss them 1 1,2,8 I 7
3 Explain the Classification of Stones 1 1,2,8 II,V 7
4
Explain the Properties of stones in structural
requirements 1 1,2,8 II,V 7
5
Explain in brief about the Composition of good
brick earth 1 1,2,8 II,V 7
6 Explain briefly about manufacturing of bricks? 1 1,2,8 II,V 7
7 Explain Seasoning of timber and its methods. 1 1,2,8 II,V 7
8 Illustrate about the Structure of wood 1 1,2,8 II 7
9 Explain in detail about the Properties of wood 1 1,2,8 II,V 7
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Explain in detail about the Classification of
various types of woods used in buildings 1 1,2,8 II,V 7
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Explain the qualities of a good timber & defects
observed in wood 1 1,2,8 II,V 7
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Explain the Characteristics of good tile Types of
tiles 1 1,2,8 II,V 7
13 Explain the Manufacturing methods of good tile 1 1,2,8 II,V 7
14 Explain about the Constituents of a paint 1 1,2,8 II,V 7
15
Illustrate about the process of Painting of new
and old wood 1 1,2,8 II 7
16
Distinguish between White washing and
distempering 1 1,2,8 IV 7
17 Illustrate about the different Types of paints 1 1,2,8 II 7
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Explain about Varnish and its usage as
building material in the construction process 1 1,2,8 II,V 7

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Introduction to Building materials
Building materials have an important role to play in this modern age of
technology. Although their most important use is in construction activities, no field
of engineering is conceivable without their use. Also, the building materials industry
is an important contributor in our national economy as its output governs both the
rate and the quality of construction work. There are certain general factors which
affect the choice of materials for a particular scheme. Perhaps the most important
of these is the climatic background. Obviously, different materials and forms of
construction have developed in different parts of the world as a result of climatic
differences. Another factor is the economic aspect of the choice of materials.
The rapid advance of constructional methods, the increasing introduction of
mechanical tools and plants, and changes in the organization of the building
industry may appreciably influence the choice of materials. Due to the great diversity
in the usage of buildings and installations and the various processes of production,
a great variety of requirements are placed upon building materials calling for a very
wide range of their properties: strength at low and high temperatures, resistance to
ordinary water and sea water, acids and alkalis etc. Also, materials for interior
decoration of residential and public buildings, gardens and parks, etc. should be,
by their very purpose, pleasant to the eye, durable and strong.
Specific properties of building materials serve as a basis for subdividing them
into separate groups. For example, mineral binding materials are subdivided into
air and hydraulic-setting varieties. The principal properties of building materials
predetermine their applications. Only a comprehensive knowledge of the properties
of materials allows a rational choice of materials for specific service conditions.
The importance of standardization cannot be over emphasized. It requires the
quality of materials and manufactured items to be not below a specific standard
level. However, the importance of standardization is not limited to this factor alone,
since each revised standard places higher requirements upon the products than the
preceding one, with the effect that the industry concerned has to keep up with the
standards and improved production techniques.
Thus, the industry of building materials gains both in quantity and quality,
so that new, more efficient products are manufactured and the output of
conventional materials is increased.
To develop products of greater economic efficiency, it is important to compare
the performance of similar kinds of materials under specific service conditions.
Expenditures for running an installation can be minimized by improving the quality
of building materials and products.

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Building industry economists are thus required to have a good working
knowledge, first, of the building materials, second, of their optimum applications on
the basis of their principal properties, and, third, of their manufacturing techniques,
in order that the buildings and installations may have optimum engineering,
economic performance and efficiency.
Having acquired adequate knowledge, an economist specializing in
construction becomes an active participant in the development of the building
industry and the manufacture of building materials.
Characteristics or Qualities of Good Building Stone
A good building stone should have the following qualities.
Density
It is the mass of a unit volume of homogeneous material denoted by
Bulk density
It is the mass of a unit volume of material in its natural state (with pores and voids)
calculated as
For most materials, bulk density is less than density but for liquids and materials
like glass and dense stone materials, these parameters are practically the same.
Properties like strength and heat conductivity are greatly affected by their bulk
density. Bulk densities of some of the
building materials are as follows:

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Bulk density
It is the ratio,
It indicates the degree to which the volume of a material is filled with solid matter.
For almost all building materials it is less than 1.0 because there are no absolutely
dense bodies in nature.
specific weight
It is also known as the unit weight) is the weight per unit volume of material,
Specific weight can be used in civil engineering to determine the weight of a structure
designed to carry certain loads while remaining intact and remaining within limits
regarding deformation. It is also used in fluid dynamics as a property of the fluid
(e.g., the specific weight
of water on Earth is 9.80 kN/m3 at 4°C). The terms specific gravity, and less often
specific weight, are also used for relative density.
Specific Gravity
Specific Gravity of solid particles of a material is the ratio of weight/mass of a
given volume of solids to the weight/mass of an equal volume of water at 4°C.
Porosity
It is the degree to which volume of the material of the material is interspersed
with pores. It is expressed as a ratio of the volume of pores to that of the specimen.
Porosity is indicative of other major properties of material, such as bulk density,
heat conductivity, durability, etc. Dense materials, which have low porosity, are
used for constructions requiring high mechanical strength on other hand, walls of
buildings are commonly built of materials, featuring considerable porosity.
Following inter relationship exists between void ratio and the porosity.

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Void Ratio (e)
It is defined as the ratio of volume of voids (Vv) to the volume of solids (Vs).
Appearance
For face work it should have fine, compact texture; light-coloured stone is
preferred as dark colours are likely to fade out in due course of time.
Structure
A broken stone should not be dull in appearance and should have uniform
texture free from cavities, cracks, and patches of loose or soft material.
Stratifications should not be visible to naked eye.
Strength
A stone should be strong and durable to withstand the disintegrating action
of weather. Compressive strength of building stones in practice range between 60 to
200 N/mm2
Weight
It is an indication of the porosity and density. For stability of structures such
as dams, retaining walls, etc. heavier stones are required, whereas for arches, vaults,
domes, etc. light stones may be the choice.
Hardness
This property is important for floors, pavements, aprons of bridges, etc. The
hardness is determined by the Mohs scale (Section 3.2).
Toughness
The measure of impact that a stone can withstand is defined as toughness.
The stone used should be tough when vibratory or moving loads are anticipated.
Porosity & Absorption
Porosity depends on the mineral constituents, cooling time and structural
formation. A porous stone disintegrates as the absorbed rain water freezes, expands,
and causes cracking.
Weathering
The resistance of stone against the wear and tear due to natural agencies
should be high.

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Workability
Stone should be workable so that cutting, dressing and bringing it out in the
required shape and size may not be uneconomical.
Specific Gravity
The specific gravity of most of the stones lies between 2.3 to 2.5.
Thermal movement
Thermal movements alone are usually not trouble-some. However, joints in
coping and parapets open-out in letting the rain water causing trouble. Marble slabs
show a distinct distortion when subjected to heat.
An exposure of one side of marble slab to heat may cause that side to expand
and the slab warps. On cooling, the slab does not go back to its original shape.
Water Absorption
It denotes the ability of the material to absorb and retain water. It is expressed
as percentage in weight or of the volume of dry material
Water absorption by volume is always less than 100 per cent, whereas that by
weight of porous material may exceed 100 per cent. The properties of building
materials are greatly influenced when saturated.
The ratio of compressive strength of material saturated with water to that in
dry state is known as coefficient of softening and describes the water resistance of
materials. For materials like clay which soak readily it is zero, whereas for materials
like glass and metals it is one. Materials with coefficient of softening less than 0.8
should not be recommended in the situations permanently exposed to the action of
moisture.
Hygroscopicity
It is the property of a material to absorb water vapour from air. It is influenced by
air-temperature and relative humidity; pores—their types, number and size, and by
the nature of substance involved.
Fire Resistance
It is the ability of a material to resist the action of high temperature without
any appreciable deformation and substantial loss of strength. Fire resistive materials
are those which char, smoulder, and ignite with difficulty when subjected to fire or
high temperatures for long period but continue to burn or smoulder only in the
presence of flame, e.g., wood impregnated with fire proofing chemicals. Non-
combustible materials neither smoulder nor char under the action of temperature.
Some of the materials neither crack nor lose shape such as clay bricks, whereas
some others like steel suffer considerable deformation under the action of high
temperature.

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Stones should be free from calcium carbonate, oxides of iron, and minerals
having different coefficients of thermal expansion. Igneous rock show marked
disintegration principally because of quartz which disintegrates into small particles
at a temperature of about575°C. Limestone, however, can withstand a little higher
temperature; i.e., up to 800°C after which they disintegrate.
Refractoriness
It denotes the ability of a material to withstand prolonged action of high temperature
without melting or losing shape. Materials resisting prolonged temperatures
of1580°C or more are known as refractory. High-melting materials can withstand
temperature from 1350–1580°C, whereas low-melting materials withstand
temperature below 1350°C.
Chemical Resistance
It is the ability of a material to withstand the action of acids, alkalis, seawater
and gases. Natural stone materials, e.g., limestone, marble and dolomite are eroded
even by weak acids, wood has low resistance to acids and alkalis, bitumen
disintegrates under the action of alkali liquors.
Seasoning of Stone
A freshly cut stone carries some natural moisture known as quarry sap
making it soft and workable. The quarry sap is a mineral solution and reacts
chemically with the mineral constituents when the stone is exposed to atmosphere
after quarrying.
The stone becomes harder and compact. The process takes about 6 to 12
months for complete seasoning. When the quarry sap evaporates, it leaves a
crystalline film on the faces of the stone and makes them weather resistant. The
dressing before seasoning improves the weather resistance. As such, the dressing,
carving and moulding, etc. should be done as early after quarrying as possible.
Durability
It is the ability of a material to resist the combined effects of atmospheric and other
factors.

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STONES
1.0 Introduction:
Stone has been defined as the natural, hard substance formed from minerals
and earth material which are present in rocks. Rock may be defined as the portion
of the earth’s crust having no definite shape and structure. Almost all rocks have a
definite chemical composition and are made up of minerals and organic matter.
Some of the rock-forming minerals are quartz, felspar, mica, dolomite, etc. The
various types of rocks from which building stones are usually derived are granite,
basalt, trap, marble, slate, sandstone and limestone.
Use of stone in building construction is traditional in the places where it is
produced, although even there its high cost imposes limitations on its use. The
conditions which govern the selection of stone for structural purposes are cost,
fashion, ornamental value and durability.
Being aggregations of minerals, the properties of rocks are dependent upon
the character of these constituents, identified by their physical properties such as
hardness, cleavage, streak, colour, lustre, specific gravity and shape of crystals.
Some minerals feature great strength, hardness and resistance to chemical
attack (quartz); others have poor strength and readily soak in water (gypsum); some
minerals display a great tendency to cleavage and split readily along one or several
directions (mica), thus decreasing the strength of the rock they make up.
All the building structures are composed of different types of materials. These
materials are either called building materials or materials of construction. It is very
essential for a builder, may be an architecture or engineer or contractor, to become
conversant thoroughly with these building materials. The knowledge of different
types of material, their properties and uses for different purposes provides an
important tool in the hands of the builders in achieving economy in material cost.
The material cost in a building range 30 to 50 percent cost of total cost construction.
In addition to material economy, the correct use of material results in better
structural strength, functional efficiency and aesthetic appearance.
Some of the important properties of minerals are as follows:
Hardness
It is probably the most important property for rapid determination of minerals.
It is measured by scratching the mineral with a series of substances of known
variation in hardness
using the following scale of Mohs:
Talc, easily scratched with the thumb-nail: 1
Gypsum, scratched by the thumb-nail: 2

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Calcite, not scratched by thumb-nail but easily cut by knife: 3
Fluorite, can be cut by knife with greater difficulty than calcite: 4
Apatite, can be cut only with difficulty by knife: 5
Orthoclase, can be cut with knife with great difficulty on thin edges: 6
Quartz, not scratched by steel, scratches glass: 7
Topaz: 8
Sapphire: 9
Diamond: 10
If, for example, a given substance is scratched by fluorite and not by calcite its
hardness is
between 3 and 4.
Cleavage
It is the measure of the capability of some minerals to split along certain
planes parallel to the crystal faces. The various types of cleavage seen in the minerals
are Basal, Prismatic, Cubic, Rhombohedral and Octahedral.
Streak
It is the colour of the mineral in powder-form. For some minerals, their colour
is seen to be entirely different from that of their powder, which makes streak a useful
property in the identification of ore-minerals. Streak can be readily observed by
scratching it on a streak plate
made of unglazed porcelain or roughened glass.
Colour
It is a valuable characteristic of metallic minerals, but less reliable for non-
metallic minerals.
Lusture
It is shine on the surface of a mineral and its appearance under reflected light
is classified as vitreous (glassy), greasy, pearly, resinous, dull, silky and metallic.
Crystal
The crystal form is of importance when a mineral has had the opportunity to
develop its natural shape. This is not the normal condition in rock structure.

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1.1 Classification of Rocks:
The rocks may be classified on the basis of their geological formation, physical
characteristics and chemical composition as shown in Fig. 3.1.
Building stones are obtained from rocks occurring in
nature and classified in three ways.
1. Geological classification
2. Physical classification
3. Chemical classification
I. Geological Classification:
According to this classification, the rocks are of the following types
a. Igneous rocks:
Rocks that are formed by cooling of Magana (molten or pasty rocky material)
are known as igneous rocks.
Eg: Granite, Basalt and Dolerite etc.
b. Sedimentary rocks:
These rocks are formed by the deposition of production of weathering on the
pre-existing rocks.
Examples: gravel, sandstone, limestone, gypsum, lignite etc.
c. Metamorphic rocks.
These rocks are formed by the change in character of the pre-existing rocks.
Igneous as well as sedimentary rocks are changed in character when they are
subject to great heat and pressure. Known as metamorphism.
Examples: Quartzite, Schist, Slate, Marble and Gneisses.
II. Physical Classification:
This classification based on general structure of rocks.
According to this, the rocks are classified into three types
a. Stratified Rocks:
These rocks possess planes of stratification or cleavage and such rocks can be
easily split along these planes
Ex: sedimentary rocks

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b. A stratified rocks:
The structure may be crystalline granular or compact granular. Examples:
Igneous rocks and Sedimentary rocks affected by movements of the earth.
c. Foliated Rocks:
These rocks have a tendency to split up in a definite direction only.
Ex: Metamorphic rocks.
III. Chemical Classification:
According to this classification rocks are classified into three types.
a. Siliceous rocks:
In these rocks, silica is predominating. The rocks are hard; durable and not
easily effected by weathering agencies.
Ex: Granite, Quartzite, etc.
b. Argillaceous Rocks:
In these rocks, clay predominates. The rocks may be dense and compact or may
be soft.
Ex: slates, Laterites etc.
c. Calcareous rocks:
In these rocks, calcium carbonate predominates. The durability to these rocks
will depend upon the constituents present in surrounding atmosphere.
Ex: Lime Stone, marble etc.
Uses of stones:
1. Structure:
Stones are used for foundations, walls, columns, lintels, arches, roofs,
floors, damp proof course etc.
2.Face works.
Stones are adopted to give massive appearance to the structure. Wall are of bricks
and facing is done in stones of desired shades. This is known as composite
masonry.
3. Paving stones:
These are used to cover floor of building of various types such as residential,
commercial, industrial etc.
They are also adopted to form paving of roads, foot paths etc.
4. Basic material:
Stones are disintegrated and converted to form a basic material for cement
concrete, morum of roads, calcareous cements, artificial stones, hallow blocks etc.

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5.Miscelleneous:
Stones are also used for (i) ballast for railways (ii) flux in blast furnace (iii)
Blocks in the construction of bridges, piers, abutments, retaining walls, light
houses, dams etc.
1.3 Qualities of a good building stone:
The following are the qualities or requirements of a good building stone.
1.Crushing strength:
For a good building stone, the crushing strength should be greater than
l000kg per cm2.
2. Appearance:
Good building stone should be a uniform colour, and free from clay holes,
spots of other colour bands etc capable of preserving the colour for long-time.
3. Durability:
A good building stone should be durable. The factors like heat and cold
alternative wet and dry, dissolved gases in rain, high wind velocity etc affect the
durability.
4. Fracture:
For good building stone its fracture should be sharp, even and clear.
5. Hardness:
The hardness greater than 17, treated as hard used in road works. It is
between 14 to 17, medium hardness, less 14 said be poor hardness.
6. Percentage wear:
For a good building stone, the percentage wear should be equal to or less
than 3 percent.
7. Resistance to fire:
A good building stone be fire proof. Sandstone, Argillaceous stone resists fire
quite well
8. Specific gravity:
For a good building stone, the specific gravity should be greater than 8.7 or
so.
9. Texture:
A good building stone should have compact fine crystalline structure should
be free from cavities, cracks or patches of stuff or loose material.
10. Water absorption:
For a good building stone, the percentage absorption by weight after 24
hours should not exceed 0.60.

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11. Seasoning:
Stones should be well seasoned before putting into use. A period of about 6
to 12 months is considered to be sufficient for proper seasoning.
12. Toughness Index:
Impact test, the value of toughness less than 13 – Not tough, between 13
and 19 – Moderate, greater than 19- high
1.4 Characteristics of stones
In order to ensure suitable selection of stone of particular work, one must be
conversant with its composition, characteristics, uses and place of availability.
1.4.1 Granite
1. Igneous rock
2. Composed of quart, felspar and mica and minerals
3. Available in grey, green, brown and pink and red
4. Hard and durable
5. High resistance to weathering
6. The texture varies with its quality
7. Specify gravity 2.7 and compressive strength 700 to 1300
kg/cm2
8. Used for ornamental, road metal, railway ballast, aggregate
for concrete; for construction of bridges, piers and marine
works etc.
1.4.2 Balast
1. Igneous rock
2. It is compact, hard and heavy
3.Available in red, yellow grey, blue and greenish black colour
4. Specific gravity is 3 and compressive strength varies 1530 to 1890 kg/cm2.
5. Used for ornamental, rail road ballast, aggregates for concrete etc.
1.4.3 Sand Stone:
1. Sedimentary rock
2. It is available in variety of formations fine grained, coarse grained compact or
porous
3. Available in white, green, blue, black, red and yellow.
4. Specific gravity 2.65 to 2.95
5. Compressive strength is 650kgs / cm2
6. Used for ashlar works

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1.4.4 Lime Stone:
1. Sedimentary rock: It is available in a variety of forms which differ from one
another in colour Compaction, texture,
hardness and durable
a. Compact lime stone
b. Granular lime stone
c. Magnesia lime stone
d. Kanker lime stone
f. Used for paving, road metal, etc
1.4.5 Marble
1. Metamorphic rock
2. Available in white, blue, green, yellow black and red colour
3. High compactness,
4. Suitable for decorative works, wall lining columns, pile, table slabs, hearths,
tiled floors, steps of stair case etc.
1.4.6 Slate:
1. Metamorphic rock
1. Non-absorbent, compact fine grained and produce metallic ringing sound when
struck
2. Available in black, dark blue, grey, reddish brown etc.
3. Used for providing damp proof course, paving dados etc
1.5. Selection of stones
In contemplating the use of stone for various engineering works, the selection
of the nature and quality of stone is governed by the purpose in view, cost of stone,
its ornamental value and durability Suitability various types of stones for different
purposes and situation is briefly discussed below
a. For face work, in general marble, granite and close-grained sand stone are used
in the form of thin slabs (veneers) where the structure subjected to adverse weather
effects.
b. For pillars, balustrade, pedestals, columns statues and door and window sill and
paving stone, granite marble and compact lime stone can be recommend because
they can take good polish.
c. For ornamental works such as moulding and carvings, fine-grained sand stone,
fine grained marble and fine-grained granite are used.
d. For bridges, piers, docks, break-waters and other marine structures the stone
should be very hard, heavy, strong and durable granite and gneiss are recommended
for this purpose

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e. For road metal, stones should be hard, tough, resistant to abrasion and durable.
Basalt and course-grained granite are generally recommended for this purpose.
f. For railway ballast, the stone should be hard, dense, durable, tough and easily
workable sandstone, compact lime stone, trap and quartzite are commonly used
g. In situation like steps, doors sills, paving’s etc where there is a regular flow of
traffic, stone should be hard, dense, easily workable and durable. Marble, slates and
sand stones are
commonly use in such places.
h. In fire proof construction, compact sand stone should always be preferred.
1.6 Artificial stones:
These are also known as cast stones or reconstructed stones. Artificial stones may
take up various
forms such as
a. Cement concrete:
This is the mixture of cement, fine aggregates, coarse aggregates and water. It may
be cast in site
or pre-cast if steel is used with cement concrete, it is known as reinforced cement
concrete.
b. Mosaic tiles:
Pre-Cast concrete tiles with marble chips at top surface are known as tiles. They are
available in different shades and widely adopted at present.
c. Terrazzo:
This is a mixture of marble chips and cement. It is used for bathrooms residential
buildings, temples etc.
Advantages of artificial stones:
1. Cavities may be kept in artificial stones to convey pipes, electric wires etc.
2. Grooves can be kept in artificial stone while it is being cast which are useful for
fixing various fittings.
3. It can cast in desired shape
4. It can be made in a single piece and hence trouble of getting large blocks of stone
for lintels, beams etc is avoided.
5. It can be made stronger than natural stone
6. It is cheap and economical
7. It is more durable than natural stone
8. Natural bed is absent in artificial stones and hence, the question of taking
precautions with respect to the natural bed of stones does not arise.

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Clay Products
Clay And Its Classifications
Clay is the most important raw material used for making bricks. It is an
earthen mineral mass or fragmentary rock capable of mixing with water and forming
a plastic viscous mass which has a property of retaining its shape when moulded
and dried. When such masses are heated to redness, they acquire hardness and
strength. This is a result of micro-structural changes in clay and as such is a
chemical property.
Purest clays consist mainly of kaolinite (2SiO2.Al2O3.2H2O) with small
quantities of minerals such as quartz, mica, felspar, calcite, magnesite, etc.
By their origin, clays are subdivided as residual and transported clays.
Residual clays, known as Kaolin or China clay, are formed from the decay of
underlying rocks and are used for making pottery.
On the basis of resistance to high temperatures (more than 1580°C), clays are
classified as refractory, high melting and low melting clays.
The refractory clays are highly dispersing and very plastic. These have high
content of alumina and low content of impurities, such as Fe2O3, tending to lower
the refractoriness. High melting clays have high refractoriness (1350–1580°C) and
contain small number of impurities such as quartz, felspar, mica, calcium carbonate
and magnesium carbonate. These are used for manufacturing facing bricks, floor
tiles, sewer pipes,
etc.
Low melting clays have refractoriness less than 1350°C and have varying
compositions. These are used to manufacture bricks, blocks, tiles, etc.
Physical Properties of Clay:
Plasticity
tensile strength
texture
shrinkage
porosity
fusibility and colour after burning are
the physical properties which are the most important in determining the value of
clay.

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BRICKS
Bricks are obtained by moulding clay in rectangular blocks of uniform size
and then by drying and burning these blocks. As bricks are of uniform size, they
can be properly arranged, light in weight and hence bricks replace stones.
One of the oldest building material bricks continues to be a most popular and
leading construction material because of being cheap, durable and easy to handle
and work with. Clay bricks are used for building-up exterior and interior walls,
partitions, piers, footings and other load bearing structures.
A brick is rectangular in shape and of size that can be conveniently handled
with one hand. Brick may be made of burnt clay or mixture of sand and lime or of
Portland cement concrete. Clay bricks are commonly used since these are
economical and easily available. The length, width and height of a brick are
interrelated as below:
Length of brick = 2 × width of brick + thickness of mortar
Height of brick = width of brick
Size of a standard brick (also known as modular brick) should be 19 × 9 × 9
cm and 19 × 9 × 4 cm. When placed in masonry the 19 × 9 × 9 cm brick with mortar
becomes 20 × 10 × 10 cm. However, the bricks available in most part of the country
still are 9" × 4 1/2" × 3" and are known as field bricks. Weight of such a brick is 3.0
kg. An indent called frog, 1–2 cm deep, is provided for 9 cm high bricks.
Characteristics of Good Brick Earth
The essential requirements for building bricks are sufficient strength in
crushing, regularity in size, a proper suction rate, and a pleasing appearance when
exposed to view.
Size and Shape
The bricks should have uniform size and plane, rectangular surfaces with
parallel sides and sharp straight edges.
Colour
The brick should have a uniform deep red or cherry colour as indicative of
uniformity in chemical composition and thoroughness in the burning of the brick.

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Texture and Compactness
The surfaces should not be too smooth to cause slipping of mortar. The brick
should have precompact and uniform texture. A fractured surface should not show
fissures, holes grits or lumps of lime.
Hardness
The brick should be so hard that when scratched by a finger nail no
impression is made. When two bricks are struck together, a metallic sound should
be produced.
Water Absorption
It should not exceed 20 per cent of its dry weight when kept immersed in water
for 24 hours.
Compressive Strength
It should not be less than 10 N/mm2.should be free from stones, kankars,
organic matter, saltpetre, etc.
Ingredients of Good Brick Earth:
For the preparation of bricks, clay or other suitable earth is moulded to the
desired shape after subjecting it to several processes. After drying, it should not
shrink and no crack should develop.
The clay used for brick making consists mainly of silica and alumina mixed in
such a proportion that the clay becomes plastic when water is added to it. It also
consists of small proportions of lime, iron, manganese, sulphur, etc. The proportions
of various ingredients are as follows:
Silica 50–60%
Alumina 20–30%
Lime 10%
{Magnesia < 1%, Ferric oxide < 7%, Alkalis < 10%} Less than 20%
{Carbon dioxide, Sulphur trioxide, Water} Very small percentage
2.1 Composition - Manufacture Process.
Composition – Following are the constituents of good brick earth.
Alumina: -
It is the chief constituent of every kind of clay. A good brick earth should
contain 20 to 30 percent of alumina. This constituent imparts plasticity to earth so
that it can be moulded. If alumina is present in excess, raw bricks shrink and warp
during drying and burning.
Silica-
A good brick earth should contain about 50 to 60 percent of silica. Silica exists
in clay either as free or combined form. As free sand, it is mechanically mixed with

19
clay and in combined form; it exists in chemical composition with alumina. Presence
of silica prevents crackers
shrinking and warping of raw bricks. It thus imparts uniform shape to the bricks.
Durability of bricks depends on the proper proportion of silica in brick earth. Excess
of silica destroys the cohesion between particles and bricks become brittle.
Lime –
A small quantity of lime is desirable in finely powdered state to prevents
shrinkage of raw bricks. Excess of lime causes the brick to melt and hence, its shape
is last due to the splitting of bricks.
Oxide of iron-
A small quantity of oxide of Iron to the extent of 5 to 6 percent is desirable in
good brick to imparts red colour to bricks. Excess of oxide of iron makes the bricks
dark blue or blackish.
Magnesia-
A small quantity of magnesia in brick earth imparts yellow tint to bricks, and
decreases shrinkage. But excess of magnesia decreases shrinks leads to the decay
of bricks. The ingredients like, lime, iron pyrites, alkalis, pebbles, organic matter
should not present in good brick earth
Manufacture of bricks:
The manufacturing of brick, the following operations are involved
1. Preparation of clay
2. Moulding
3. Drying
4. Burning
(i) Preparation of clay: - The preparation of clay involves following operations
a) Unsoiling: -
Top layer of 20cm depth is removed as it contains impurities.

20
b) Digging: -
Clay dug out from ground is spread on level ground about 60cm to 120cm
heaps.
c) Cleaning: -
Stones, pebbles, vegetable matter etc removed and converted into powder
form.
d) Weathering: -
Clay is exposed to atmosphere from few weeks to full season.
e) Blending: -
Clay is made loose and any ingredient to be added to it is spread out at top
and turning it up and down in vertical direction.
Fig 2.1 Pug Mill
f) Tempering: -
Clay is brought to a proper degree of hardness, then water is added to clay
and whole mass is kneaded or pressed under the feet of men or cattle for large scale,
tempering is usually done in pug mill as shown in the fig 2.1
Process: -
Clay with water is placed in pug mill from the top. When the vertical staff is
rotated by using electric pair, steam or diesel or turned by pair of bullocks. Clay is
thoroughly mixed up by the actions of horizontal arms and knives when clay has
been sufficiently pugged, hole at the bottom of tub, is opened cut and the pugged
earth is taken out from ramp for the next operation of moulding.
Moulding:
Clay, which is prepared form pug mill, is sent for the next operation of
moulding. Following are the two ways of moulding.

21
Details of Mould
Hand Moulding:
Moulds are rectangular boxes of wood or steel, which are open at top and
bottom. Steel moulds are more durable and used for manufacturing bricks on large
scale as shown in fig 2.2. Bricks prepared by hand moulding are of two types.
Fig 2.2 Wooden mould & Steel mould
a) Ground moulded bricks
b) Table moulded bricks

22
(a) Ground moulded bricks:
Ground is first made level and fine sand is sprinkled over it. Mould is dipped
in water and placed over the ground to fill the clay. Extra clay is removed by wooden
or metal strike after the mould is filled forced mould is then lifted up and raw brick
is left on the ground. Mould is then dipped in water every time lower faces of ground
moulded bricks are rough and it is not possible to place frog on such bricks.
Ground moulded bricks of better quality and with frogs on their surface are
made by using a pair of pallet boards and a wooden block.
Strikes
(b) Table-moulded bricks:
Process of moulding these bricks is just similar to ground bricks on a table of size
about 2m x 1m.
(1) Machine moulding:
This method proves to be economical when bricks in huge quantity are to be
manufactured at the same spot. It is also helpful for moulding hard and string clay.
These machines are broadly classified in two categories
(a) Plastic clay machines
(b) Dry clay machines
a) Plastic clay machines:
This machine containing rectangular opening of size equal to length and width
of a brick. Pugged clay is placed in the machine and as it comes out through the
opening, it is cut into strips by wires fixed in frames, so their bricks are called wire
cut bricks.

23
b) Dry clay machines:
In these machines, strong clay is first converted into powder form and then
water is added to form a stiff plastic paste. Such paste is placed in mould and
pressed by machine to form hard and well-shaped bricks. These bricks are
behaviour than ordinary hand moulded bricks. They carry distinct frogs and exhibit
uniform texture.
(2) Drying:
The damp bricks, if burnt, are likely to be cracked and distorted. Hence
moulded bricks are dried before they are taken for the next operation of burning.
Bricks are laid along and across the stock in alternate layers. The drying of brick is
by the following means
(i) Artificial drying –
drying by tunnels usually 1200C about 1 to 3days

24
(ii) Circulation of air-
Stacks are arranged in such a way that sufficient air space is left between them free
circulation of air.
(iii)Drying yard- special yards should be prepared slightly higher level prevent the
accumulation of rain water
(iv)Period for frying –
usually about 3 to 10 days to bricks to become dry
(v) Screens –
screens are necessary, may be provided to avoid direct exposure to wind or sun.
(3) Burning:
This is very important operation in the manufacturing of bricks to impart hardness,
strength and makes them dense and durable. Burning of bricks is done either in
clamps or in kilns.
Clamps are temporary structures and they are adopted to manufacture bricks
on small scale. Kilns are permanent structures and they are adopted to manufacture
bricks on a large scale. A typical clamp is as shown in fig 2.3
Fig 2.3 Clamp or Pazawah
(1) A trapezoidal shape in plan with shorter is slightly in excavation and wider end
raised at an angle of 150 from ground level
(2) A brick wall with mud is constructed on the short end and a layer of 70cm to
80cm thick fuel (grass, cow dung, ground nuts, wood or coal) laid on the floor.

25
(3) A layer consists of 4 or 5 courses of raw bricks laid on edges with small spaces
between them for circulation of air
(4) A second layer of fuel is then placed, and over it another layer of raw bricks is
put up. The total height of clamp in alternate layers of brick is about 3 to 4 m
(5) When clamp is completely constructed, it is plastered with mud on sides and top
and filled with earth to prevent the escape of heat
(6) The period of burning is about one to two months and allow the same time for
cooling
(7) Burnt bricks are taken out from the clamp
Advantages:
(i) The bricks produced are tough and strong because burning and cooling are
gradual
(ii) Burning in clamps proves to be cheap and economical
(iii) No skilled labour and supervision are required for the construction of clamps
(iv) There is considerable saving of clamps fuel
Disadvantages:
(i) Bricks are not of required shape
(ii) It is very slow process
(iii) It is not possible to regulate fire in a clamp
(iv) Quality of brick is not uniform
Kilns: A kiln is a large oven, which is used to burnt bricks by
1) Intermittent kilns
2) Continuous kilns
1) Intermittent kilns:
These intermittent in operation, which means that they are loaded, fired, cooled and
unloaded.
a) Intermittent up-draught kilns
b) Intermittent down-draught kilns
a) Intermittent up-draught kiln:
This is in the form of rectangular with thick outside walls as shown in the fig 2.4.
wide doors are provided at each end for loading and unloading of kilns. A temporary
roof may be installed to protect from rain and it is removed after kiln is fired. Flues
are provided to carry flames or hot gases through the body of kiln.

26
Fig 2.4 Intermittent kiln
(i) Raw bricks are laid in row of thickness equal to 2 to 3 bricks and height 6 to 8
bricks with 2 bricks spacing between rows
(ii) Fuels are filled with brush wood which takes up a free easily
(iii) Loading of kiln with raw bricks with top course is finished with flat bricks and
other courses are formed by placing bricks on edges
(iv) Each door is built up with dry bricks and are covered with mud or clay
(v) The kiln is then fired for a period of 48 to 60 hours draught rises in the upward
direction from bottom of kiln and brings about the burning of bricks.
(vi) Kiln is allowed to cool down and bricks are then token out
(vi) Same procedure is repeated for the next burning Bricks manufactured by
intermittent up drought kilns are better than those prepared by clamps but bricks
burnt by this process is not uniform, supply of bricks is not continuous and wastage
of fuel heat.
(b) Intermittent down-draught kilns:
These kilns are rectangular or circular in shape. They are provided with
permanent walls and closed tight roof. Floor of the kiln has opening which are
connected to a common chimney stack through flues. Working is same as up-
draught kiln. But it is so arranged in this kiln that hot gases are carried through
vertical flues up to the level of roof and they are then released. These hot gases move
down ward by the chimney draught and in doing so, they burn the bricks.
Advantages:
(i) Bricks are evenly burnt
(ii) Performance of this kiln is better than that of up-draught kiln
(iii) This kiln is suitable for burning of structural clay tiles, terra cota because of
close control of heat.

27
2. Continuous kilns:
These kilns are continuous in operations. This means that loading, firing, cooling
and unloading are carried out simultaneously in these kilns. There are three types
of continuous kilns.
a) Bull’s trench kiln
b) Hoffman’s kiln
c) Tunnel kiln
a) Bull’s trench kiln:
This kiln may be of rectangular, circular or oval shape in the plan as shown in fig
2.5. It is constructed in a trench excavated in ground either fully underground
partially projecting above ground openings is provided in the outer walls to act as
flue holes.
Dampers are in the form of iron plates and they are used to divide the kilns in
suitable sections and most widely used kiln in India.
Fig 2.5 Bull’s trench kiln
The bricks are arranged in such a way that flues are formed. Fuel is placed in
flues and it is ignited through flue holes after covering top surface with earth and
ashes to prevent the escape of heat usually two movable iron chimneys are employed
to form draught.
These chimneys are placed in advance of section being fired. Hence, hot gases
leaving the chimney warm up the bricks in next section. Each section requires about
one day to burn. The tentative arrangement for different sections may be as follows
Section 1 – loading

28
Section 2 – empty
Section 3 – unloading
Section 4 – cooling
Section 5 – Burning
Section 6 – Heating
b) Hoffman’s kiln:
This kiln is constructed over ground and hence, it is sometimes known as
flame kiln. Its shape is circular to plan and it is divided into a number of
compartments or chambers. A permanent roof is provided; the kiln can even
function during rainy season. Fig 2.6 shows plan and section of Hoffman’s kiln with
12 chambers
Fig 2.6 Hoffman’s kiln
Chamber 1 - loading
Chamber 2 to 5 – drying and pre-heating
Chambers 6 and 7 - burning
Chambers 8 to 11 - cooling
Chamber 12 – unloading
The initial cost in stalling this kiln is high, the following advantages:
(i) Good quality of bricks is produced
(ii) It is possible to regulate heat inside the chambers through fuel holes
(iii) Supply of bricks is continuous and regular
(iv) There is considerable saving in fuel due to pre heating of raw bricks by flue
gases

29
c) Tunnel kiln:
This type of kiln is in the form of tunnel, which may be straight, circular or
oval in the plan. Raw bricks are placed in trolleys which are then moved from one
end to the other end of tunnel.
Raw bricks get dried and pre-heated as they approach zone of fire. In zone of
fire, bricks are burnt to the required deque and they are then pushed forward for
cooling. When bricks are sufficiently cooled, they are unloaded. The kiln proves to
be economical when the bricks are manufactures on a large scale. As temperature
is under control, uniform bricks of better quality are produced.
COMPARISON BETWEEN CLAMP-BURNING AND KILN-BURNING
No. Item Clamp-burning Kiln-burning
1 Capacity About 20000 to 100000
bricks can be prepared at a
time.
Average 25000 bricks can
be prepared per day.
2 Cost of fuel Low as grass, cow dung,
litter, etc. may be used.
Generally high as coal
dust is to be used.
3 Initial cost Very low as no structures are
to be built.
More as permanent
structures are to be
constructed.
4 Quality of
bricks
Percentage of good quality
bricks is small about 60% or
so.
Percentage of good quality
bricks is more about 90%
or so.
5 Regulation
of fire
It is not possible to control or
regulate fire during the
process of burning
Fire is under control
throughout the process of
burning.
6 Skilled
supervision
Not necessary throughout
the process of burning.
Continuous skilled super
vision is necessary.
7 Structure Temporary structure. Permanent structure.
8 Suitability Suitable when bricks are to
be manufactured on a small
scale and when the demand
of bricks is not continuous.
Suitable when bricks are
to be manufactured on a
large scale and when there
is continuous
demand of bricks.
9 Time of
burning
and
cooling.
It requires about 2 to 6
months for burning and
cooling of bricks.
Actual time for burning of
one chamber is about 24
hours and only about 12

30
days are required for
cooling of bricks.
10 Wastage of
heat.
There is considerable
wastage of heat from top and
sides and hot flue gas is not
properly
utilised.
Hot flue gas is used to dry
and pre-heat raw bricks.
Hence wastage of heat is
the least.
2.2 Classification:
Bricks can broadly be divided into two categories.
(i) Unburnt or sundried bricks
(ii) Burnt bricks
(i) Un burnt or Sun-dried bricks-
UN burn or sun dried with the help of heat received from sun after the process of
moulding.
These bricks can only be used in the constructions of temporary and cheap
structures. Such bricks should not be used at places exposed to heavy rains.
(ii) Burnt Bricks:
The bricks used in construction works are burnt bricks and they are classified into
the following four categories.
Classification Of Bricks
Clay bricks are classified as
First Class,
Second Class,
Third Class And
Fourth Class…… based on their physical and mechanical properties.
First Class Bricks
1. These are thoroughly burnt and are of deep red, cherry or copper colour.
2. The surface should be smooth and rectangular, with parallel, sharp and straight
edges and square corners.
3. These should be free from flaws, cracks and stones.
4. These should have uniform texture.
5. No impression should be left on the brick when a scratch is made by a finger nail.
6. The fractured surface of the brick should not show lumps of lime.
7. A metallic or ringing sound should come when two bricks are struck against each
other.
8. Water absorption should be 12–15% of its dry weight when immersed in cold
water for 24 hours.

31
9. The crushing strength of the brick should not be less than 10 N/mm2. This limit
varies with different Government organizations around the country.
Uses:
First class bricks are recommended for pointing, exposed face work in masonry
structures, flooring and reinforced brick work.
Second Class Bricks
These are supposed to have the same requirements as the first-class
ones except that
1. Small cracks and distortions are permitted.
2. A little higher water absorption of about 16–20% of its dry weight is allowed.
3. The crushing strength should not be less than 7.0 N/mm2.
Uses:
Second class bricks are recommended for all important or unimportant hidden
masonry works and centering of reinforced brick and reinforced cement concrete
(RCC) structures.
Third Class Bricks
These are under burnt.
They are soft and light-colored
They produce a dull sound when struck against each other.
Water absorption is about 25 per cent of dry weight.
Uses:
It is used for building temporary structures.
Fourth Class Bricks
These are overburnt
They are badly distorted in shape and size
They Possess brittle in nature.
Uses:
The ballast of such bricks is used for foundation and floors in lime concrete and
road metal.
2.3 Qualities of Good Brick:
(i) Bricks should be table moulded, well burnt in kilns, copper coloured, free from
cracks and with sharp and square edges.
(ii) Bricks should be uniform shape and should be of standard size.
(iii) Bricks should give clear ringing sound when struck each other.
(iv) Bricks when broken should show a bright homogeneous and compact structure
free from voids.

32
(v) Bricks should not absorb water more than 20 percent by weight for first class
bricks and 22 percent by weight for second class bricks, when soaked in cold water
for a period of 24 hours.
(vi) Bricks should be sufficiently hard no impression, should be left on brick surface,
when it is scratched with finger nail.
(vii) Bricks should be low thermal conductivity and they should be sound proof.
(viii) Bricks should not break when dropped flat on hard ground from a height of
about one meter.
(ix) Bricks, when soaked in water for 24hours, should not show deposits of white
salts when allowed to dry in shade.
(x) No brick should have crushing strength below 55kg/cm2
2.4 Special Types:
Bricks are made in a wide range of shapes and to suit the requirements of the
location where they are to be used. Special form of bricks may be needed due to
structural consideration or for ornamental decoration as defined by the architect.
Specially moulded bricks avoid the cumbersome process of cutting and rounding
the rectangular bricks to the desired shape. Some of the special types of bricks
commonly used are given below.
a. Squint Bricks:
These bricks are made in a variety of shapes and are used to the construction of a
cute and obtuse squint quoins as shown.
Fig 2.7 Types of Special Bricks
b. Bull Nosed Bricks:
These bricks are used to form rounded quoins.

33
c. Perforated Bricks:
These bricks may be standard size bricks produced with perforations running
through their thickness. Perforated bricks are easy to burn and their light weight
makes it possible to cut down the weight of the structure and effect in foundations.
The aperture of the perforations is such that it gives maximum amount of
ventilation. But does not permit the entry of rats or mice. These bricks are used for
constructing load bearing walls of low buildings, panel walls for multi-storeyed
buildings and for providing partition walls.
d. Hallow Bricks:
These bricks are made of clay and are provided with one or more cavities.
Hallow bricks are light in weight and are used to increase insulation against heat
and dampness. They are used for the construction of load bearing walls, partition
walls or panel walls to multi-storeyed buildings.
e. Circular Bricks:
These bricks have internal and external faces curved to meet the requirement
of the particular curve and radius of the wall. These bricks are used for wells, towers
etc

34
f. Plinth cornice and String Course Brick:
These bricks are moulded in several patterns with the object of adding
architectural beauty to the structure and at the same time to helping to throw the
rack water off the face of the walls.
g. Coping Bricks:
These bricks are manufactured in a variety of shapes to set the thickness of
the wall and are throated on the underside to throw off rain water
h. Paving Bricks:
These bricks are specially made for paving the surface of streets and highways.
These bricks are usually made from shale, fire clay on a mixture of the two. They
are unaffected by weather and ordinary traffic wear. They are loaded on the bed of
sand which in term rests on foundation of stone or concrete.
The bricks are laid by grouting with cement mortar or asphalt.
They are machine moulded and are burnt in a continuous kiln to ensure high degree
of vitrification.
TILES
Tile products which are manufactured from clay are called "clay products".
E.g.: Bricks, earthen ware's stoneware etc. The tiles are thin slabs available in
various shapes which are used for covering of roofs, flooring walls or even making
drains (to send was water from houses).
Tiles
Tiles are manufactured from stronger clay they may be moulded by hand or
machine. The handmade tiles thickness varies from 12 to 15 mm whereas the
machine-made tiles have minimum thickness of 10 mm. While in manufacturing
these tiles at most care should be taken because due to their thickness and liable
for damage in drying or at burning by way of cracking and varying.

35
The tiles should be free from any defects such as cracks, distortions, non-
uniformity of size and shape etc. The manufacturing of tiles is just similar to those
of bricks. The main difference is that the clay used for tiles should be very pure, fine
and strong plastic clays (shales) mixed with clay and moulded in the same way'.
These tiles are fired at temperatures about 1100° to 1300°C. Tiles should possess
high strength and low water absorption.
Manufacture of tiles:
Following four distinct operations are involved in the general process of
manufacturing tiles:
(1) Preparation of clay
(2) Moulding
(3) Drying
(4) Burning.
Each operation will now be briefly treated.
(1) Preparation of clay:
The selected clay is taken and it is made free from any impurity such as grit,
pebbles, etc. Such clay is then pressed and converted into fine powder in pug mills.
For tiles of superior quality, a large quantity of pure water is added to the powdered
clay and it is well mixed in a tank.
Mixture is then allowed to stand quietly. Coarse heavy particles settle at the
bottom of tank. Fine particles arc taken into other tanks and water is then allowed
to dry off. Fine clay left after such process is used for the manufacture of tiles. To
make the tiles hard and impervious, a mixture of ground glass and pottery ware may
be added in required quantity to clay of tiles.
(2) Moulding:
Clay is placed in moulds which represent the pattern or shape in which tile is
to be formed. Moulding may be done either with the help of wooden moulds or
mechanical means or potter's wheel. Wooden moulds should be prepared from well-
seasoned timber.
Clay is pressed into such moulds and tiles are ready for drying when clay is
taken out of moulds. Care should be taken to preserve the shape of tiles during the
removal of moulds. Moulding with the help of mechanical means includes the
provision of machines and clay is pressed into such machines to get tiles of desired
section and shapes. Method of moulding by potter's wheel is similar to one that is

36
adopted by a potter in the manufacture of earthenware vessels. This method is
adopted when tile is of circular shape when on the wheel. It may, however, have
diameter varying along its length.
(3) Drying:
Tiles, as they come out of moulds, are placed flat one above the other in
suitable number. Different heaps are thus formed. After about 2 days, the
irregularity of tiles due to warping is corrected with a flat wooden mallet. Tiles are
then lifted as they have by now become hand-hard.
Edges and under surfaces arc cleaned. They are stacked on edge under a
shade to dry for about two days or so. Drying under a shade prevents warping and
cracking of tiles due to rain and sun.
(4) Burning:
Tiles are then burnt in kilns. A typical kiln for accommodating about 30000
to 40000 tiles is shown in fig. 2-1. It is circular in shape and is protected b y a shed.
A layer of bricks is laid flat on the rows of long, narrow flues. Burning is affected by
firing wood placed in. these flues. Bricks are arranged in such a way that open
spaces are left in between them. Above the layer of bricks, dried tiles are placed on
edge layer by layer. Closing of doorways is affected by brickwork in mud. Top of kiln
is covered with a layer of old tiles placed in a loose condition.
Regulation of heat is important to achieve better results. Fire is gentle in the
beginning. It removes moisture. It is then raised to about 800°C
Section on AB

37
Circular kiln for burning tiles
It is slackened for a period of about 6 hours and again raised to white heat,
temperature being 1300°C. This temperature is maintained steady for a period of 3
hours. Process of slackening the fire for 6 hours and then raising the temperature
to white heat is repeated. White heat is maintained for 4 hours.
Finally, flues are filled with fuel and doorways are closed by brickwork in mud.
The kiln is then gradually allowed to cool down. It requires about 72 hours to
complete the process of burning the tiles.
Tiles are taken out of the kiln. Under burnt tiles are sorted out and they are placed
on the top of kiln in the subsequent burning of tiles.
Types of Tiles
According to their use, the tiles are divided into the following types:
Roof tiles
Floor tiles
Walls tiles
Drain tiles
Glazed earthen ware tiles.
CHARACTERISTICS OF GOOD TILES
The following are the characteristics of good tiles.
 It should have Uniform Texture.

38
 It should be well burnt (without cracks, warping shrinkages etc.). It should
have accurate size and shape.
 It should be free form cracks, flaws, bends, twisted etc. It should have uniform
colour with good appearance. It should be hard and durable.
 It should have good resistance to dampness.
 It should have good resistance to adverse atmospheric (weathering agencies)
effects.
 It should be fit in properly, when placed in position.
 It Should Possess less Water Absorption (Less Than 15 Per Cent).
 Good tile produces ringing sound when struck with another tile.
FIG: Corrugated Tile
Roofing Tiles
These tiles are used for covering the roof of a structure. They are divided into the
following.
1. Flat tiles
2. Curved tiles
3. Inter locking tiles.
1. Flat Tiles:
These are generally made in rectangular shape with various dimensions. To fix them
on battens, two or more holes are provided on their surface. Nails are used to fix the
tile to the wooden battens (reefers) permanently. They are laid in lime or cement
mortar. They can be laid in one or two Layer’s
Suitable lays are provided at sides and edges. These can be used for sloped as well
as flat roofs. Flat tiles can be further sub divided into the following types;
(i) Slate
(ii) Burnt clay terracing tiles
(i)Slate Tiles: The used sizes are:
600 x 300 x 15 mm and
500 x 250 x 10 mm

39
The water absorption of these tiles should not be mor, then 21 %.
(ii) Burnt Clay Terracing Tiles: The usual size is:
Length: 250 to 150 mm in the stages of 25 mm
Width:200 to 100 mm in the stages of 25 mm
Thickness: 35 to 50 mm in stages of 5 mm.
The compressive strength should be less than 7.5 N/mm2 (75 kg/cm2) the water
absorption should not be more than 20 % by weight tolerances shall be + 3% in
dimensions (L, W, T).
(a) Single Lap Arrangement of Slates (b) Double Lap Arrangement of Slates
Fig: Plain Tailing
2. Curved Tiles:
These tiles are divided into the following. (1) Pot (ii) Pan tiles
Pot Tiles:
They may be called as country roofing tiles. They are made by hand with the
help of potter’s wheel. The cross-section of the tube is circular the potter makes two
vertical cuts before removing from the wheel. These cuts assist in splitting the tils
into two parts. After drying, the tiles are burnt in an open clamp mainly pot tiles are
kept over flat tiles.

40
They look like half round (semi-circular and tapering in shape. These tils are laid
alternatively concaveness convex sides. while forming roof.
Disadvantages:
(a) It is un uniform in shape and size as because they are handmade.
(b) It is difficult to repair broken tiles laid on roof.
(c) These tiles are brittle and break under pressure.
Fig: Hip Tailing
Pan Tiles:
Actually, these tiles are little bit flat in nature but less curved. Drying and
burning of tiles are done carefully to get better quality of tiles. The dimensions of
these tiles are as follows:
Length: 330 to 380 mm Width: 230 to 280 mm
These tiles are stronger than pot tiles.
Fig: Arrangement of Laying Pot Tiles

41
Inter Locking Tiles:
These tiles are made flat with surface corrugations. They inter lock as shown
in figure. They are made from selected clay by moulding under pressure in machine:
and burnt very carefully in kilns.
Ex: Allahabad, Mangalore, Sialkot tiles.
These belong to roofing tiles. Tiles of special shapes are made for hip, ridge and
valley portion of the roof.
Mangalore Tiles:
As these tiles are manufactured at Mangalore city, so these tiles are named as
Mangalore tiles. These tiles are in special pattern with flat and with suitable keys
and projections. Generally, these tiles are suitable for sloped roofs The length and

42
width of these tiles are suitable for sloped roofs. The length and width of these tiles
are:
L X W L X W
320 X 210 mm 410 X 235 mm
350 X 220 mm 425 X 260 mm
340 X 215 mm 420 X 250 mm
According to IS 654 - 1962, these tiles are divided as class AA and class A on the
basis of
W.O: Water absorption & B.O: Breaking load the average weight of 6 tiles should not
be less than 2 kgs and more than 3 kgs thickness ranges from 30 to 50 mm.
Name of Properties Class AA Class A
Water Absorption
(Max.)
19% 24%
Minimum Average Load
Breaking
1.02 kN 0.82 kN
Min. Breaking Load Above 0.9 kN 0.66 kN
The life of these roofing tiles is estimated at about 25 years with replacement of
about 5% per year.
(a) Plan Back of Tile (b) Plan Face of Tile
(c) Section on YY (d) Arrangement of Two Tiles Length wise

43
(e) Arrangement of Two Tiles Breadth Wise
(f)Eaves Lugs - 2 with base thickness not less than 15 mm top thickness not less
than 10 mm projection from lug 10 mm
FIG: Mangalore Pattern Tile
Flooring Tiles:
Flooring tiles are thicker and stronger than ordinary tiles so that they can
withstand the load on the floor. These tiles are made from China clay or cement.
Generally, these tiles are laid on the surface of the floor for good appearance. The
top surface of the tile is glazed and the bottom is left rough as it has to adhere to
the surface of the floor. These tiles are made in different colours with designs and
shapes (square, rectangular, hexagonal shapes)
vitrified to prevent water absorption.
The different sizes are
15 x 15 x 6 cm
60 x 30 x 5 cm
There dimensions are given as
L W T
150 150 18
200 200 20
225 225 22
Generally, these tiles are very hard and compact to withstand the wear and
tear. Generally, these tiles are used in bathrooms kitchens, hospitals, hotels etc.
Requirements of Floor Tiles:
1. These tiles should be hard and compact
2. It should resist wear and tear
3. These should be free from cracks, pebbles lime etc.
4. The tile when struck with other tile it should produce a ringing sound.
5. When the tile is immersed in water for 24 hours it should not absorb water
more than 24 %.

44
GLAZE TILES AND PROCELAIN
Glaze Tiles
These tiles are manufactured from combination of China clay (kaolin) flint,
and felspar. The wetted mixture is pressed into the mould and they are burnt in kiln
at 2300°F for 5 days and then dipped in a glaze.
Glaze:
It is made from iron oxides, copper oxide, cobalt oxide or manganese oxide.
These are kept in an oxidizing atmosphere for about 2 days at 1900°F
The usual sizes of these tiles are:
150 x 150 mm &100 x 100 mm
The thickness may vary from 6 to l0mm. These tiles are also called as
"Encaustic tiles". These tiles are used in important buildings as these are very costly.
For example, these are used for decoration of floors, walls, walls of bathrooms,
hospitals, star hotels etc. These tiles are used especially for hygienic conditions and
cleanliness purpose. These tiles can be cleaned easily. These tiles are also used at
toilets, railway stations, Bus stations, Bus stands waiting rooms etc.
Uses:
1. These are used as sanitary appliances.
2. Glazed earthen ware tiles are used for bathrooms, kitchens etc.
3. Glazed articles are also used in laboratories as jars etc. to hold chemicals etc.
Porcelain
These are many types. Porcelain is mainly made from kaolin. It is burnt at
such high temperature that it melts and is glazed. It is semi-transparent. Some flux
is added to kaolin (Bone ash, felspar etc. act as flux). Porcelain is mainly used in
electrical industry.
These are vitrified at a temperature of 1320°C to make it non -porous and
non-absorption of water. Generally, porcelain is in white colour. These may be hard
or soft in touch.
Soft Porcelain:
Soft porcelain is manufactured from white clay to which some known
percentage of flint is added. By adding this flint will act as flux and it makes easy to
melt into glass when is under firing the burning of the slurry product is done in two
steps.
At the first stage it is heated up to 1200°C temperature and coated with a glaze
solution and the temperature rises to 1500°C. At this stage the product attains its
final state in the presence of glaze solution. The glaze percolates into the product
and the finished stage are the porcelain product.

45
Ex: Crockery like dishes, plates. some ornamental articles some gift articles, toys
etc. comes under this category.
Hard Porcelain:
The name itself tells that the product is hard and non-ferrous. It is also made
form kaolin quartz and felspar are added to kaolin (clay) in act as filler and flux while
at the time of burning process. The glaze coat is applied to the green product. It is
mainly used for electrical installations and bathrooms. toilets fixtures etc. As it is
quite hard and non-absorbent.
Fig: Stoneware Pipe or Sewer
Uses of Porcelain:
It is used for Sanitary Wares in bathrooms and toilets.
It is used as electrical installations.
Wood and Wood Products
Introduction
Wood is a hard and fibrous substance which forms a major part of the trunk
and branches of a tree. It can also be defined as a natural polymeric material which
practically does not age. Wood as a building material falls in two major classes—
natural and man-made. With the advances in science and technology, wood in its
natural form as timber, lumber, etc. is being rapidly replaced by composite wood
materials in which natural wood is just a basic ingredient of a matrix or a laminate.
The latter are found to be more useful and adaptable as they may be treated
chemically, thermally or otherwise as per requirements. Some examples are
plywood, fibreboards, chipboards, compressed wood, impregnated wood, etc.
Wood has many advantages due to which it is preferred over many other
building materials. It is easily available (this won’t be true after some years) and easy
to transport and handle, has more thermal insulation, sound absorption and
electrical resistance as compared to steel and concrete. It is the ideal material to be
used in sea water. Wood is a good absorber of shocks and so is suitable for
construction work in hilly areas which are more prone to earthquakes. Finally, since
wood can be easily worked, repairs and alterations to wood work can also be done
easily.

46
Owing to the above-mentioned advantages, wood is very widely used in
buildings as doors, windows, frames, temporary partition walls, etc. and in roof
trusses and ceilings apart from formwork.
Classification of Trees
Trees are classified as endogenous and exogenous according to the mode of growth.
Endogenous Trees
Trees grow end wards, e.g., palm, bamboo, etc.
Exogenous Trees
Trees grow outwards and are used for making structural elements. They are further
subdivided
as conifers and deciduous.
Coniferous
These are evergreen trees having pointed needle like leaves, e.g., deodar, chir, fir,
kail, pine
and larch. They show distinct annual rings, have straight fibres and are soft with
pine as an
exception, light in colour, resinous and light weight.
Deciduous
These trees have flat board leaves, e.g., oak, teak, shishum, poplar and maple. The
annual
rings are indistinct with exception of poplar and bass wood, they yield hard wood
and are non-resinous, dark in colour and heavy weight.
Growth of Trees
In spring the roots of the tree suck sap as food from the soil which reaches
the branches and the leaves. Sap contains moisture which gets evaporated. It
absorbs carbon from air in presence of sunlight and becomes denser. In autumn,
the sap descends and deposits in the form of a layer below the bark. This layer,
referred to as the cambium layer, hardens and adds a layer of wood to the outside of
tree every year in the form of concentric rings. These annual rings furnish valuable
information regarding the age of the log, the rapidity and the uniformity of its growth.

47
Generally, the rings are widest at the centre and narrower nearer the bark.
Also, the rings are widest at the bottom in young, thrifty trees and near the top in
old ones. The cells formed in the cambium layer are primarily cellulose and are
commonly referred to as fibres because of their needle-like shape. They are cemented
into groups by lignin, which gives the strength to wood.
The comparative width of annual rings, the direction and the arrangement of
the cells and fibres are the causes of the grains of the wood. Rapidly growing trees
having wide annual rings produce coarse grained wood, while those of slower growth
produce wood with narrow rings or fine grain. The wood is said to be straight-grained
when the wood elements are straight and run parallel to the pith and cross-grained
when the elements do not run parallel to the axis.
Cross-grain has a pronounced weakening effect on the strength of beams when the
slope of the grains is 1:15 or greater.
Timber should be felled as soon as it is matured. The best time is midsummer
or midwinter, when the sap is at rest. If it is felled, when the sap is vigorous in
movement, the timber decays. If the tree is cut young, it yields soft wood and if it
stands too long, the decay starts.
Structure of Timber
A tree can be divided into three portions, crown—composed of branches and
leaves, trunk, and roots. The trunk accounts for about 80 per cent of the total bulk
of wood. Figure 4.1 shows the structure of well grown timber from trunk of the
exogenous tree. The structure of timber visible to naked eye or at a small
magnification is called macro structure, and that apparent only at great
magnifications, the micro structure. Macro structure of the timber can be studied by
cutting the trunk in three directions (Fig. 4.1 (a)). In the cross-sectional and radial
ducts, the following main parts of a tree, e.g., bark, cambium, sap wood, heart wood
and pith, become readily apparent (Fig. 4.1(b)). Each of the components has a
specific function.

48
Bark
The bark protects the wood against mechanical damage.
Bast
Its inner layer, called bast conveys the nutrients from the crown downwards
and stores them.
Cambium
The function of cambium is to grow wood cells on the inside and smaller bast
cells on the outside.
Sapwood
The sapwood assists in the life process of tree by storing up starch and
conducting sap. The cells in the sap wood are active.
Heart Wood
The heart wood gives a strong and firm support to the tree. With the growth
of tree, the cells in the inner older portion of trunk gradually become inactive and
lifeless, but do not decay. This portion of the trunk is called heart wood.
Pith
At the centre of the cross-section is the pith, a small area occupied by friable
tissues consisting of thin walled, loosely connected cells called pith. In a felled tree,
it easily crumbles and rots.
Medullary Rays
In the cross-sectional direction, nutrients pass from bast to the heart through
groups of cells running at right angles to the cambium layers and are referred to as
medullary rays.
Fig. Cross-Section of a Tree
Characteristics Of Good Timber
The principal characteristics of timber of concern are strength, durability and
finished appearance.
1. Narrow annual rings, closer the rings greater is the strength.

49
2. Compact medullary rays.
3. Dark colour.
4. Uniform texture.
5. Sweet smell and a shining fresh cut surface.
6. When struck sonorous sound is produced.
7. Free from the defects in timber.
8. Heavy weight.
9. No woolliness at fresh cut surface.
Seasoning of Timber
Timber cut from freshly felled trees is too wet for normal use and is
dimensionally unsuitable. Seasoning is the process of reducing the moisture content
(drying) of timber in order to prevent the timber from possible fermentation and
making it suitable for use.
It can also be defined as the process of drying the wood to a moisture content
approximately equal to the average humidity of the surroundings, where it is to be
permanently fixed. Very rapid seasoning after removal of bark should be avoided
since it causes case hardening and thus increases resistance to penetration of
preservatives. Some of the objects of seasoning wood are as follows:
1. Reduce the shrinkage and warping after placement in structure.
2. Increase strength, durability and workability.
3. Reduce its tendency to split and decay.
4. Make it suitable for painting.
5. Reduce its weight.
Methods of Seasoning
Timber can be seasoned naturally or artificially.
Natural or Air Seasoning
The log of wood is sawn into planks of convenient sizes and stacked under a
covered shed in cross-wise direction in alternate layers (Fig. 4.2) so as to permit free
circulation of air. The duration for drying depends upon the type of wood and the
size of planks. The rate of drying is however very slow. Air seasoning reduces the
moisture content of the wood to 12–15 per cent. It is used very extensively in drying
ties and the large size structural timbers.

50
Artificial Seasoning
The prevalent methods of artificial seasoning are as follows:
Water Seasoning
The logs of wood are kept completely immersed in running stream of water,
with their larger ends pointing upstream. Consequently, the sap, sugar, and gum
are leached out and are replaced by water. The logs are then kept out in air to dry.
It is a quick process but the elastic properties and strength of the wood are reduced.
Boiling in water
Boiling in water or exposing the wood to the action of steam spray is a very
quick but expensive process of seasoning.
Kiln seasoning
It is adopted for rapid seasoning of timber on large scale to any moisture
content. The scantlings are arranged for free circulation of heated air with some
moisture or superheated steam. The circulating air takes up moisture required from
wood and seasons it. Two types of kilns, the progressive (Fig. 4.3 (a)) and the
compartment (Fig. 4.3 (b)) are in use.
For most successful kiln-seasoning the timber should be brought to as high
a temperature as it will stand without injury before drying is begun; otherwise, the
moisture in the hot outer fibres of the wood will tend to flow towards the cooler
interior. With kiln drying there is a little loss in strength of timber, usually less than
10 per cent. Also, the wood is more thoroughly and evenly dried, thus reducing the
hygroscopicity of the wood.

51
Chemical or Salt Seasoning
An aqueous solution of certain chemicals has lower vapour pressures than
that of pure water. If the outer layers of timber are treated with such chemicals the
vapour pressure will reduce and a vapour pressure gradient is setup. The interior of
timber, containing no salts, retains its original vapour pressure and, therefore, tends
to dry as rapidly as if there had been no treatment.
The result is to flatten the moisture gradient curves, to reduce the slope of the
curves, and consequently to reduce the internal stresses induced during drying.
Since it is these stresses which are responsible for defects such as checks, etc. a
chemically treated timber will exhibit fewer defects. Common salt or urea are
generally used; the latter is preferred as the corrosive action of common salt is a
drawback.
Electrical Seasoning
The logs are placed in such a way that their two ends touch the electrodes.
Current is passed through the setup, being a bad conductor, wood resists the flow
of current, generating heat in the process, which results in its drying. The drawback
is that the wood may split.

52
Mc. Neil’s Process
It has no adverse effects; it is the best method although most expensive. The
timber is stacked in a chamber with free air space (l/3rd of its capacity) and
containing products of combustion of fuels in the fire place. The time required for
complete seasoning is 15 to 60 days.
DEFECTS IN TIMBER
Defects can occur in timber at various stages, principally during the growing
period and during the conversion and seasoning process. The defects in the wood
are due to irregularities in the character of grains. Defects affect the quality, reduce
the quantity of useful wood, reduce the strength, spoil the appearance and favour
its decay.
DEFECTS DUE TO ABNORMAL GROWTH
Following are some of the important defects commonly found in wood due to
abnormal growth or rupture of tissues due to natural forces.
CHECKS
It is a longitudinal crack which is usually normal to the annual rings. These
adversely affect the durability of timber because they readily admit moisture and
air.
SHAKES
These are longitudinal separations in the wood between the annual rings.
These lengthwise separations reduce the allowable shear strength without much
effect on compressive and tensile values. The separations make the wood
undesirable when appearance is important.
Both the shakes and checks if present near the neutral plane of a beam they
may materially weaken its resistance to horizontal shear.

53
Heart Shake occurs due to shrinkage of heart wood, when tree is overmatured.
Cracks start from pith and run towards sap wood. These are wider at centre and
diminish outwards.
Cup Shakes appears as curved split which partly or wholly separates annual rings
from one another. It is caused due to excessive frost action on the sap present in the
tree, especially when the tree is young.
Star Shake are radial splits or cracks wide at circumference and diminishing
towards the centre of the tree. This defect may arise from severe frost and fierce heat
of sun. Star shakes appear as the wood dries below the fibre saturation point. It is
a serious fault leading to separated log when sawn.
Knots are bases of twigs or branches buried by cambial activity of the mother
branch. The root of the branch is embedded in the stem, with the formation of
annual rings at right angles to those of the stem. The knots interrupt the basic grain
direction of the wood, resulting in a reduction of its strength. In addition, these affect
the appearance of the wood.
A dead knot can be separated from the body of the wood, whereas live knot cannot
be. Knots reduce the strength of the timber and affect workability and cleavability
as fibres get curved. Knots are classified on the basis of size, form, quality and
occurrence.
Size Pin knot (under 12 mm), small knot (12–20 mm), medium knot (20–40 mm) and
large knot (over 40 mm).
" Round knot and spike knot (a round knot exposed by sawing lengthwise).

54
Sound knot—as hard and solid as the surrounding wood, decayed knot—contains
advanced decay and is softer than the surrounding wood, encased knot—the annual
rings fail to grow into the fibres of the surrounding wood, tight knot—a knot so
securely fastened that it holds its position in the finished product.
Occurrence Single knot—when wood fibres deflect around one knot, cluster knot—
when wood fibres deflect about two or more knots as a unit and, branch knot—two
or more knots radiating from a common centre.
Rindgall is characterised by swelling caused by the growth of layers of sapwood
over wounds after the branch has been cut off in an irregular manner. The newly
developed layers do not unite properly with the old rot, thereby leaving cavities, from
where decay starts.
Twisted Fibres are caused by wind constantly turning the trunk of young tree in
one direction.
Upsets are caused by the crushing of fibres running transversely during the growth
of the tree due to strong winds and unskilled felling consequently resulting in
discontinuity of fibres.
End Splits are caused by greater evaporation of sap at the end grains of log and
can be reduced by painting the exposed end grains with a water proof paint or
capping the exposed end with hoop iron bandage.

55
Foxiness is a sign of decay appearing in the form of yellow or red tinge or
discolouration of overmatured trees.
Rupture is caused due to injury or impact.
Defects due to Conversion
Conversion is the term used to describe the process whereby the felled tree is
converted into marketable sizes of timber. Conversion defects are basically due to
unsound practice in milling or attempts to economise during conversion of timber.
A wane occurs in timber which contains, on one or more faces, part of the
bark or the rounded periphery of the trunk. This reduces the cross-sectional area,
with consequent reduction in strength in the parts affected. Excessive slope of grains
may also be classed as a conversion defect when conversion has not been done
parallel to the axis of the trunk.
Defects due to Conversion
Defects due to Seasoning
These defects are directly caused by the movement which occurs in timber
due to changes in moisture content. Excessive or uneven drying, exposure to wind
and rain, and poor stacking during seasoning can all produce distortions in timber.
These defects result in loosening of fixings or disruption of decoration, or both.
The common types of seasoning defects are:
checks—longitudinal separation of fibres not extending throughout the cross-
section of wood;
splitting—separation of fibres extending through a piece of timber from one face to
another;
warpage—consists of cupping, twisting and bowing.

56
Defects due to Seasoning
Decay of Timber
Timber does not deteriorate by natural, physical or chemical changes or by
pure ageing. It is, however, affected by destructive elements, such as weathering,
chemical attack, fungi, insects or rodents. The most crucial amongst these are fungi,
insects and rodents and are described as follows.
Decay due to Fungal and Bacterial Attack
Wood is essentially an organic substance, made up of a skeleton of cellulose
impregnated with lignin. The organic substances are susceptible to attack by both
bacteria and fungi. Bacteria are the smallest of living organism and do not cause
any serious damage to timber, except for some discolouration’s. Fungi are a system
of plant organism which live in and attack timber causing rot and decay.
The method by which bacteria decompose wood is probably similar in nature
to a fungal attack. Fungi reproduce through minute particles called spores, millions
of which are produced at the fruiting stage. These spores send out mycelia, which in
turn destroy the wood tissue by secretions of solvent chemicals and enzymes.
After a considerable proportion of the cell wall has been destroyed by mycelia,
the wood becomes brittle and weak.
The basic requirements for the existence of fungi are moisture, suitable
temperature and food supplies. The wood itself forms the food supply and optimum
temperature conditions are in the range of 18°C to 30°C. Some fungi like Merulius

57
lacrymans and Poria incrassata provide moisture by themselves and seem to thrive
even in fairly dry wood leading to what is technically known as dry rot.
The various symptoms of incipient decay are discolouration, abnormal mottled
appearance, roughness of surface and presence of soft spots of intense
discolouration.
Control of Fungi and Bacterial Attack
One of the prime requirements in the control of fungal attack is the dryness
of timber. The timber should not be subjected to alternate wet and dry conditions.
When this is unavoidable, a proper preservative treatment should be made.
Felled trees should be air-dried as rapidly as possible and sawn timber should
be kiln-seasoned properly in accordance with good air-seasoning practice.
Thereafter, they should be protected from rain and other sources of moisture. It
should be ensured that adequate ventilation is there around the timber to prevent
fungal attack. Also, no timber used in a structure should contain sapwood which is
more susceptible to fungal attack because of the food supplies stored in its
parenchyma.
Damage due to Insects
Termites
Termites, or white ants as they are inappropriately called, are the most
destructive of all insect agencies. They are small, social insects which form vast
colonies and possess differentiated casts to carry on specialized functions in the
social structure. They completely excavate the wood at the centre leaving the outer
shell intact. They also attack furniture and wood work in houses and railway
sleepers, etc.
Beetles
These are small insects and they cause rapid decay of timber by converting
them into fine powder. Usually, the outer shell of timber remains intact and hence
the timber looks sound from outside until it fails completely.

58
Carpenter Ants
These are usually black in colour and vary in size within the same nest. Unlike
termites, they do not eat wood but merely tunnel it out for habitation. Their food is
largely nectar, honeydew, and other sweet substances.
They normally attack slightly rotted or water softened wood but may continue
into wood which appears perfectly sound. Timbers are often riddled with galleries
before the presence of ants is detected. The frass ejected from the workings is quite
coarse and shredding.
Control of Insects is much simpler than eradicating fungi. The tunnels made by
the insects help in the deep penetration of toxic elements that are used to destroy
them.
Large scale fumigation is carried out using powerful hydrocyanic acid gas, but
this method is not recommended as this gas is highly poisonous and dangerous.
The use of creosote is also not desirable because of its odour and undesirable
colour. A good insecticide which does not damage the paint or varnish and vaporises
easily is yet to be found. The vapours should also not be dangerous to human beings.
It is found that no insecticide can fulfil all these requirements in one application and
periodic applications are required to be effective.
The best alternative is common turpentine mixed with a small quantity of Orth
dichlorobenzene. This vapour is very deadly to insects and is not poisonous to
human beings and animals.
Damage Due to Rodents
Although the domestic rodents do not destroy timber in the same sense as the
organism so far considered, they are capable of penetrating both wood and concrete.
The problem of rodents is more serious in food-handling establishments.
Control of Rodents
The guiding principle is to close all openings or passages and making doors
and windows capable of closure in a rat-tight manner by fixing metal sheets over the
lower parts of doors.
Wood Products
Many wood-based products have been developed to economise on the use of
timber. These wood products are manufactured under controlled conditions in
factories. As such, these have desired shape and dimensions, appearance, strength
and durability. Some of these are described below.

59
S. No Name of
Timber
Description of Timber Uses
1. Teak Dark brown to deep yellow or
reddish brown, Durable, seasoned
hard, takes up a good polish. Good
fire resistant very valuable material
and costly. It’s lost after seasoning
at 12 % moisture content is 625
kgs/m3
Used in house
construction such
as Doors, windows,
frames, panels,
flooring ship
building, railway
carriages furniture
etc.,
2. Rose wood
or black
wood
Dark in color, strong and tough,
closed grained structure. It is very
hard wood. It can take a high polish
it maintains its shape well. Its wt.
After seasoning at 12% moisture
content is 990 kg/m3
Used for furniture
superior quantity or
ornamented works.
Decorative cabinet
(TV stands, kitchen
works etc.,)
3. Mango Deep gray in color, strong it
maintains its shape well, its weight
after seasoning at 12% moisture
content is 655 kg/m3
Used for cheap
furniture toys,
packing boxes,
cabinet works panels
for doors and
windows, planks
for boats etc.
4. Guava Flexible but it is hard and tough. But
not strong enough fine-grained
structure. Its wt. after seasoning is
750 kg/m3.
For making top toys
instrument handless
5. Tamarind Dark brown, durable, knots may
present. Its wt. after seasons is1280
kg/m3.
Sugar mill tool,
carts, Ag tools
well curbs etc.,
6. Stain Wood Yellow It is close hard and durable.
Its wt. after seasoning is about 960
kg/m3.
Used for
furniture and
other
ornamental
works.
7. Bamboo It is endogenous tree. It is strong and
durable but also flexible. It should
be seasoned carefully
Used for
scaffolding, roofs,
rafters, tool
handles
agricultural
instruments, parts
cart roofing’s,
temporary bridges
etc.

60
8. Yack Yellow As age passes it becomes dark
to darkness, even grained, compact,
hard and smooth
Used for houses
boats windows
and doors panels
cabinet making
etc.
9. Babul It grows to a max height of 15 mts the
max pink color contains closed
compacted grains, heavy, strong,
hard and tough its wt. after
seasoning at 12 % m.c. is 835
kg/m3
Used for wheels,
bodies of a bullock
carts, Ag
instruments tool
handless, roofing,
scaffolding etc.,
10. Sal Brown in color fibrous close
grained, durable hard it is best
suited for underground works. It can
take good polish. Its wt. after
seasoning at 12 % moisture content
is 800 kg/m3.
For house works,
ships railway
sleepers, bridges,
etc. Ground and
under water work.
11.
Palms
Dark brown in color, fibrous structure
strong and durable. Its m.c. is 1040
kg/m3
Roof coverings,
rafters’ joists,
furniture etc.,
12. Black palm Reddish grey. Durable more
suitable for under water works
Thatched roofs,
rafters etc.
13.
Gumar
Pale yellow. It is best suited for
under water construction strong
and durable. Its wt. after seasoning
is 580 kg/m3.
Planks for doors
panels
well cubs, carriages
furniture.
14. Bijasal Light from colour, strong and
durable, its texture is coarse
grained. It is not easily attacked by
termites. Its wt. after seasoning at
12% moisture content is 800
kg/m3.
Bullock cart wheels,
ordinary building
works.
15. Irul It is very hard, heavy and durable.
It requires slow and careful
seasoning. Its wt. after seasoning at
12% moisture content is
835 kg/m3.
Ag instruments
head constructions,
railway sleepers
etc.
16. Kathal Yellow to deep brown. It is very heavy,
hard and durable.
Doors, window
panels platforms for
wooden bridges,
used for files etc.
17. Aini Yellowish brown, close grained. Its
wt. after seasoning at 12 %
moisture content is 595 kg/m3. It
takes a good polish.
Used for under
water works

Building Materials and Concrete Technology Unit I

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