Material and construction technolgy level 5 civil

Skills International Page 1
Properties of Matter
Handout 1
 Atom:
Atoms are particles of matter. They are the smallest unit of matter that defines chemical properties and their
isotopes. Every substance: solid, liquid, gas is made up of atoms. Atoms are very tiny, such that the size of an
atom is measured in picometers. (10-12
m).
Every atom is composed of a nucleus made of protons and neutrons .The nucleus is surrounded by a cloud of
electrons. The electrons are bound to the atom by the electromagnetic forces and protons and neutrons are
bound to each other by nuclear forces.
 Molecule:
A molecule is an electrically neutral group of two or more atoms held together by chemical bonds.
 Chemical Element:
A chemical element is a pure chemical substance consisting of a single type of atom distinguished by its
atomic number (No. of protons). Elements are divided into metals, metalloids and nonmetals.
 Solution:
In chemistry, a solution is a homogeneous mixture composed of only one phase. In such a mixture a solute is
the substance dissolved in another substance, known as the solvent. The concentration of a solute in a solution
is a measure of how much of that solute is dissolved in the solvent.
 Mixture:
A mixture is a material system made up of two or more different substances which are mixed but not
combined chemically.
 Chemical bonds:
Chemical compounds are formed by the joining of two or more atoms.
TYPES OF BONDS
 Ionic bonds:
Bonds in which one or more electrons from an atom are removed and attached to another atom.
E.g. - NaCl, MgCl2
 Covalent bonds:
Bond in which one or more pairs of electrons are shared by two atoms.
Eg-O2, N2, H2
 Other types of bonds: Metallic Bond, Hydrogen Bond

 Crystal:
A crystal or crystalline solid is a solid material whose constituents, such as atoms, molecules or ions are
arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. E.g.
snowflakes, diamond, table salt, metals, rocks, ceramics, glass, wax, plastics.
Physical States of Matter
Gases, Liquids & Solids are all made up of microscopic particles, but the behavior of these particles differ in
the three phases.
Solid Liquid Gases
Tightly packed, usually in a
regular pattern
Close together with no
regular arrangement
Well separated with no
regular arrangement
Does not flow Flows easily Flows easily
Vibrate but generally does not
move from place to place
Vibrate, move about and
slide on each other
Vibrate and move freely at
high speed
Non-compressible Less-compressible Compressible
Definite volume Definite volume No volume
Definite shape Takes the shape of the
Container
No shape
Change of state of matter

Physical and Chemical Properties
The characteristics that we use to identify matter and distinguish them from one another are called properties
of matter. We group these properties into two broad categories: Physical properties and Chemical
properties.
Physical properties
Physical properties of matter are usually those that we can observe with our senses. A substance's physical
property allows us to identify the substance without causing a change in the composition of the substance.
Examples of Physical properties
 physical state (solid, liquid or gas at certain temperature and pressure)
 colour
 odor
 solubility in water (the ability of substance to dissolve in water)
 density
 melting point
 boiling point
 hardness
 ductility
 malleability
Chemical properties
Chemical properties of matter are those that relate to how the substance changes in composition or how it
interacts with other substances.
Examples of chemical properties are:
 paper burns
 iron rusts
 hydration of cement
 wood rots
 thermosetting plastics char when heated to higher temperatures
In each of these, the substance's chemical property is its
 reactivity with other chemicals
 toxicity
 coordination number
 flammability
 enthalpy of formation
 heat of combustion
 oxidation states
 chemical stability
 types of chemical bonds

What is ENERGY?
Energy exists in a variety of forms. Energy associated with chemical reactions is evolved as heat. Other forms
of energies are:
 light energy
 sound energy
 electrical energy
 mechanical energy
 chemical energy
Although there are various forms of energies, they can be transferred from one form to another.
Chemical reaction: a process in which one or more substances (reactants) are converted to one or more
different substances (products). Substances are either chemical elements or compounds. A chemical reaction
rearranges the constituents of the reactants to create different substances as products.
Reactions
Endothermic and Exothermic Reactions
When physical or chemical changes occur, energy is either produced or absorbed. When the
process produces energy, it is an exothermic process. When the process absorbs energy, it is an endothermic
process.
Examples for Exothermic Reactions
 condensation of rain from water vapor
 rusting iron
 mixing water and strong acids
Examples for Endothermic Reactions
 melting ice cubes
 evaporation of water
 mixing water and ammonium nitrate
Law of Conservation of Energy
Energy can be neither created nor destroyed.
Scientists have reached the conclusion that although energy has many different forms that are
interconvertable, when one form of energy disappears, some other form of energy of equal magnitude must
appear, and vice versa. In other words, the total quantity of energy in the universe is constant.

Timber
Handout 2
The products of wood from felled trees suitable for construction purposes are called timber. Trees
meant for timber should be felled as soon as possible after reaching maturity. Prematurely felled
trees contain excess sapwood. The best time to fell trees for timber is midsummer or mid winter
when the movement of sap in wood is minimum. Timber from overaged trees is brittle and the
central portion of the tree will have cavities.
Classification of Timber
Hardwood Softwood
Definition Comes from angiosperm trees
that are not monocots: trees are
usually broad-leaved. Has
vessel elements that transport
water throughout the wood:
under a microscope, these
elements appear as pores.
Comes from gymnosperm trees
which usually have needles and
cones. Medullary rays and
tracheids transport water and
produce sap. When viewed
under a microscope, softwoods
have no visible pores because
of tracheids.
Uses Hardwoods are more likely to
be found in high-quality
furniture, decks, flooring
About 80% of all timber come
from softwood. Used for
windows, doors, medium
density fibre boards, paper,
furniture
Examples Oak, Teak, Walnut, Mahogany,
Beech
Pine, Redwood, Spruce, Yew,
Douglas fir
Density Most hardwoods have higher
density than most softwoods
Most softwoods have lower
density than most hardwoods
Cost Hardwoods are typically more
expensive than softwood
Softwoods are typically less
expensive compared to
hardwoods
Growth Hardwood has a slower growth
rate
Softwood has a faster growth
rate
Shedding of leaves Hardwoods shed their leaves
over a period of time in autumn
and winter.
Softwoods tend to keep their
needles throughout the year.
Fire Resistance More Poor

Hardwood
Softwood

Structure of Wood
Let’s consider the cross sections shown. The outer bark is like our skin. It protests the tree from
extremes of temperature, mechanical damage…etc. The inner bark is softer and moister that the outer
bark.
The outer layers are called sapwood and the inner layers heartwood. The sapwood is naturally
moister and softer than heartwood. The heartwood provides strength to the tree.
At the center is the pith or medulla. It is the original stem and tends to decay after the tree reaches
maturity.
Parts of a Tree
A tree trunk is composed of the following basic parts.
 Bark is the dead tissue, and its function is to protect the tree from weather, insects, disease,
fire, and injury.
 Phloem is a thin layer comprised of living cells, and its basic function is to transport food all
over the tree.

 Cambium is the living tissue. This layer produces both new phloem on one side and new
xylem on the other.
 The largest part of a trunk is the xylem, which is composed of both sapwood and Heartwood.
Sapwood
We can easily spot the difference between the two distinct parts of the xylem if you were to view a
crosscut of a matured hardwood trunk. Once you remove the thin outer layers, the tree is essentially
made up of the sapwood, which is light colour, and heartwood which is dark in colour.
Sapwood is the new wood and is like a pipeline which transports water through the trunk up to the
leaves. Essentially the working component of a tree, sapwood transports water and sap similar to the
way blood flows through our veins, capillaries, and arteries.
Most of a tree’s moisture is in the sapwood. Although it’s vital to a living tree, sapwood is usually
considered poor woodworking stock. Lumber cut from sapwood shrinks considerably as it goes
through the drying process. This part of the tree is susceptible to fungus than the center of the trunk.
Heartwood
As new rings of sapwood grow, the inner cells
are put out of commission and become
heartwood. The central strong pillar of a tree
is heartwood. Although this portion of the tree
is dead or retired sapwood, it doesn’t decay.
As long as the tree’s outer layers are intact,
heartwood remains strong.
As moisture is no longer transported through the straw-like cells, the pores in heartwood are filled
with organic material. The presence of chemicals called extractives cause the cell walls in heartwood
to change colour. Extractives create the rich color and unique character in heartwood.
The functional beauty of heartwood for a woodworker is threefold. First, it’s significantly less
susceptible to fungus. Secondly, heartwood contains less moisture than sapwood and will have less
shrinkage when it’s dried. Thirdly, heartwood becomes in some ways as strong as steel, as the fibers
are bound together.
Woodworking with the Xylem
 Many experienced woodworkers use only the heartwood of the tree for furniture projects.
Heartwood is undeniably stronger, richer, and more beautiful than sapwood.
 Sapwood can also have its uses if, the wood is dried to a proper level of moisture
content, which can be determined using a handheld moisture meter. Sapwood is used in
projects in which shrinking and drying of the wood won’t create problems and it’s sealed
thoroughly using paint or polythene when finished.

Conversion of Timber
Handout 3
Immediately after felling of trees, the branches are cut off and the trunk is cut into logs. The process
of cutting and sawing timber logs into suitable sections to be used for construction purposes is known
as conversion. Earlier this was done manually by saws, but nowadays it is carried out by a band and
circular saws run by machines.
The properties of timber vary in the longitudinal, tangential and radial directions. Also direction of
grain is very important and governs the strength properties. The strength parallel to grain is very
much greater than that of perpendicular to grain or inclined grain.
Long pieces of timber used as rafters, wall plates... etc are generally cut in such a way that their
longitudinal axis is parallel to the grain.
As we mentioned before due to the moisture fluctuation, timber shrinks and expands in all possible
directions.
Generally following are known by experiments.
 If tangential shrinkage is S mm
 Then radial shrinkage is S/2 to 2S/3 mm
 Longitudinal shrinkage is S/40 to S/70 mm
From this we can conclude that the timber shrinkage is very high in the tangential direction, next in
radial direction and very slightly in longitudinal direction.

Methods of Sawing of Timber
Method of Sawing will depend on several factors;
 The type of sawing machine
 The condition of the log
 Economy
 The size of log
 The wood species
 The end use of resulting timber
 Through and Through Sawing / Plain Swan / Flat Swan/Ordinary Sawing
This is one of the most popular methods of sawing. The log is cut in parallel cuts in the
direction of the grain.
 Advantages
 Low cost and fast
 Planks with the maximum width are
obtained from log.
 Little wastage.
 Reveals attractive grain pattern,
especially in softwoods.
 Disadvantages
 Not suitable for structural timber
 With this method cupping caused by
tangential shrinkage is a problem.
(cupping is the warping of the plank
away from the heart of the tree)
 They also tend to absorb more
moisture from the air which can also
lead to unwanted movement.

 Tangential Sawing
 The cut is made at a tangent to the annual
rings of the log.
 Log must be turned 90º after each cut.
 Timber will display a flame figure
 Advantages
 Produce boards with flame figure
 Tangential boards are strong boards, used for beams and joists
 Heartwood and sapwood are easily separated
 These boards can take a nail without splitting because of the position of their annual rings
 Disadvantages
 Prone to shrinkage (Cupping)
 It is expensive as the log is turned 90º for
each cut

 Quarter Sawing
 This method leaves the annual rings of the converted timber meeting the face of the board at
45 º or more.
 It is important to note that the log must be rotated each time a cut is taken.
 This method can bring the best features in wood as it produces silver grain which has clearly
defined medullary rays
 Advantages
 An attractive grain pattern is produced
 Boards are more stable and shrink less
 Boards wear more evenly, important for flooring
 More resistant to moisture penetration
 Twisting, cupping, and warping resistance
 Ages evenly over time
 Quarter Sawing
45 º or more.
 Advantages
 Quarter Sawing
45 º or more.
 Advantages

 Disadvantages
 Expensive, as the log has to be first quartered then turned for every cut.
 Narrower boards are produced
 Rift Swan
 Rift saw is typically narrow with a very straight grain pattern on the face of the board.
 The annular rings or a rift sawn board are about 30-60 degrees to the face of the board, but 45
degrees is the most optimum.
 Similar to quarter sawn, rift sawn is also referred to as radial grain.
 Each of these boards is cut radially perpendicular to the growth rings of the tree.
 High wastage of wood.
 Advantages
 Straight grain pattern on the face of the board
 Ideal for furniture legs and other linear parts.
 Vertical grain is shown from all sides
 Disadvantages
 Most expensive type because large triangles of waste are left.
 Take more time and labor

Seasoning of Timber
Handout 4
Freshly- felled wood contains a large amount of sap and moisture. Seasoning is the process of drying
timber in a controlled condition to remove sap and to reduce moisture content without introducing
any splits and distortions in the wood.
Seasoning is the process by which moisture is brought down to an acceptable limit. By seasoning the
moisture content is brought down to within 10% - 20%.
When moisture content is less than 22% the timber will maintain its shape without shrinkage and will
not be attacked by insects. The strength properties of timber will increase if moisture content is
brought below 28%.
Natural or Air Seasoning:
Air seasoning of timber products after sawing is usually carried out by stacking sawn horizontally in
layers in a covered shed. They are usually carried out by wooded battens (called crossers or spacers).
Air is allowed to freely circulate between the logs. The ends are generally painted with suitable
material to prevent end cracking. This type of seasoning may take 2 – 6 months. This process is
cheaper when compared to kiln seasoning because it promotes drying timber without any artificial
assistance.
Artificial Seasoning:
Seasoning of timber can be fastened if we use artificial seasoning.
 Kiln Seasoning
 Boiling
 Chemical Seasoning
 Electrical Seasoning
 Water Seasoning
 Vacuum Seasoning

Apart from the grain, growth ring structure and seasoning method mentioned earlier there are other
factors which determine the strength. They are
 Density
 Moisture content
 Defects
 Grain Pattern
 Inclination of grain
Density
Density of timber is a definite indication of strength .You would have observed that heavy timber
lasts long and light timber does not. E.g.-Teak
The reason being that denser the timber, closer are the growth rings .The heartwood is very strong
and hence the timber is very strong. Therefore one can say that high density timber is stronger.
When you come across a timber cross section just count the number of growth rings presents for
25mm measured radially from the centre. If the number of growth rings is between 6 and 15 it is
reasonable to conclude that the strength of timber is satisfactory.
Moisture Content
Where,
W1 – Original Weight
W0 – Oven Dry Weight
As mentioned earlier, higher the moisture content weaker the timber is. Shrinkage and expansion are
associated with high moisture contents and insects can easily attack timber in a moist atmosphere and
reduce the strength drastically. That is why timber has to be seasoned well before it is used.
Satisfactory moisture condition for timber = (20-22) % (For construction work)

Defects
Defects in timber reduce the strength drastically. Timber has many defects which could not be
controlled by man since it is a natural product. Therefore to account for defects a system of grading
of timber has been introduced. Higher the defects lower will be the grading. General grading are
Grade 75, Grade 60, Grade 50 and Grade 40 etc.
Tree in the ‘green’ state is not suitable for construction purposes and its moisture content has to be
brought down to a suitable value. The ‘green’ state moisture content is generally between 40%-200%
depending on the type of the tree.
 Moisture Movement:
Moisture content in the atmosphere varies from location to location as well as from time to time. But
at a given location, moisture content may be assumed as a constant over a certain period of time and
this moisture content depends on the ambient temperature and relative humidity. This moisture
content is defined as the Equilibrium Moisture Content (EMC)
If the moisture content in a place or timber piece is less than the EMC the moisture content in the
timber is increased to EMC, where as greater the moisture content in timber it reduces the moisture
content to (EMC). This is called as moisture movement in timber.

Defects and Preservation of Timber
Handout 5
Defects in Timber
 Natural defects
Civil Engineers should be able to identify defects in timber and classify them. Timber with defects is
priced much cheaper than the good timber. The commonly referred defects are the following.
 Knots:
These are the sections of branches of the tree
which will be present on the surface of wood
in the form of hard dark pieces. Knots are a
source of weakness in timber when used to
carry compressions. Timber with large knots
should be avoided. All knots in timber used
for buildings should be covered with two coats
of shellac before the wood is being painted.
 Shakes:
These are the cracks and splits in the felled log due to many causes.

 Twisted grain fiber:
This defect is caused in the tree itself due to
the action of high winds.
 Upset or Rupture
This is caused due to an injury during the
growth of the tree due to strong winds or bad
felling out of trees. This results a discontinuity
of fibres.
 Wane
It is a part of the original outside rounded
surface of the tree that remains in the timber
during conversion. It is important when the
timber is used for works like shoring, piling
…etc. Also used for decorative purposes.
 Presence of sapwood:
Sapwood is less durable than heartwood and it should not be present in wood used in important
places. Sapwood can be identified by the colour which will be much lighter than that of heartwood.
Also it does not take as good polish as heartwood.
 Sloping grains:
In living trees, the cells do not always grow perfectly vertical or straight and parallel to the length
of the trunk. The taper from bottom to the top causes sloping of grain in timber swan parallel to
the pitch.
 Cracks, fissures, resin pockets:
Cracks and fissures are fibre disruptions which appear in timber due to many causes. These
disruptions affect the strength of timber. Resin pockets and fissures containing resins are defects

which affect strength and suitability for decoration of wood. A long narrow crack is called a
steak.
 Chemical Defects
Chemical defects may occur when timber is placed in unsuitable positions and when get
contacted with other metals.
 Seasoning defects
Excessive or uneven drying, exposure to wind
and rain, poor seasoning and bad spacing during
seasoning can produce these defects.
 End Splitting
 Cupping
 Bowing
 Twisting
 Springing
 Honey Combing

Causes of decay of woodwork
Woodwork in buildings like doors, windows …etc should be maintained properly after they are put
up in the building. That is because of easy disintegration of wood with time. All woodworkers
require regular maintenance and treatment even if it is meant to last only for a shorter period.
The principle causes of deterioration are the following.
1. Fungal Decay
Fungi
Fungi are special living agents who do not contain chlorophyll. Organisms which contain chlorophyll
produce their own food by themselves. E.g. Plant leaves…etc
Therefore fungi have to rely on the food produced by another organism i.e. food produced by trees.
But in order to fungi to attack timber there should be a favourable condition. If the moisture content
is greater than 20% fungi can attack timber very easily. Therefore it is very important to avoid fungal
attack on timber by controlling the moisture content.
There are two types of fungal attacks. Namely
 Dry Rot
 Wet Rot
Dry Rot: (occur in slight moist conditions)
 Dry rot is more common than wet rot.
 It is produced by a fungus that grows in moist conditions, moist basements and moist wood.
 It can remain dormant even when dry until wet situation returns.
 It occurs in wood that touches the soil, in bathroom door frames, joints of beams or where
window frames are built against the sill.
 It can occur due to moist conditions and as a result of lack of ventilation.
 It is more dangerous than wet rot as the spores spread through the air.
 Typical appearance of dry rot is white fungi threads of which bear spores or seeds.
 If fungal attack has taken place, then the remedy lies in drying out the material and removing
the effected part, if the damage is extensive.
 We must also apply fungicide to prevent further reinfection.
 If the affected part is small, then it can be repaired by injection of epoxy resin.

Wet Rot: (occur in very damp conditions)
 Wet rot is produced by a fungus that requires constant supply of moisture.
 It occurs in places of permanent leak or other places where water is constantly in present.
 The spores of this fungus do not spread through air.
 In wet rot the threads are black or dark brown in colour.
 They will germinate in dry timber.
2. Attack by Beetles and Borers: They lay their eggs in holes and in surface cracks. The
most effective method against these insects is to treat the woodwork with insecticide and
preservatives. One of the common treatment material used against beetles is turpentine mixed
with a very small quantity of orthodichlorobenzene. This vapour is said to be deadly to
insects but not poisonous to human beings.

3. Attack by termites: Attacked by termites, especially in places where there is no human
habitation in the building. (Quite common in the tropics). Softwood is eaten more quickly
than hardwood. The only remedy is to arrange constant inspection and treatment with specific
anti-treatment in wood are emulsions of Heptachlor (0.5%) or Chlordane (1%) in kerosene
oil.
In all cases, timberwork in a building should be preserved by oiling, painting, varnishing etc, at
regular intervals. Woodwork should have proper ventilation around it. It should not be placed in
corrosive conditions as in lime or cement mortar or subjected to alternative wetting and drying.
Main stages of a wood destroying insect

Preservation of Timber
The basic idea behind preserving timber is to stop moisture penetrating it. When moisture content is
less than 20% no decay would occur.
Methods available are:
1. Moisture Resisting Coatings: Used on fresh surfaces. Firstly, a lead (Pb) based fibre paint
then an undercoating and two finishing coats of glass paint are applied. This will delay very
much the moisture penetration and preserve timber.
2. Impregnation treatment: By this method some synthetic resins are applied on timber which
on penetration will solidify and occupy the pores in timber. This method is very expensive
and used only on special situations such as preserving logged wood in archeological sites.
3. Chemical Preservatives: Most widely used method. The chemicals used are toxic to
organisms which attack wood. Less viscous liquid will penetrate well.
4. Charring: In this method, surface is burnt. This part acts as a protective coating.
5. Painting with tar or creosote: Chemical products obtained by distillation of tar are applied
on timber.

6. Treatment by diffusion: This is carried out on green timber (with moisture content over
50%). Just after conversion to timber very soluble boron compounds are applied on the
surface of the timber. The pieces are then stacked together and covered with impermeable
cover to prevent evaporation. Over a period of one month or more, the boron diffuses into the
wet timber and acts as a preservative.
Methods of applying preservatives:
1. Brushing or spraying: Preservatives should be flooded over the timber, particularly over
joints and cracks. Second application after 2 days must be done.
2. Deluging: Timber is fed through a tunnel conveyor of organic solvents.
3. Immersion: Timber is submerged in a bath of preservatives.
4. Pressure: Timber is placed in a closed cylinder and preservative fluid if forced into wood by
high pressure.

Industrial Timber Products
Handout 6
Nowadays solid wood of good variety is in short supply, particularly when wide and thin pieces like
door shutters and table tops are required. Natural wood can be made into many other industrial
products. These products are also known as composite boards. The common industrial products of
timber meant for these purposes are the following.
 Plywood
 Particle board or chipboard
 Hardboard
 Fibreboard
 Blockboard
There are also a large no of synthetics, laminates that can be used with wood for decoration purposes.
Boards with ornamental finishes on the surface are called ornamental grade while others are called
commercial grade.
Plywood
Plywood is the general term used to define thin layers or plies of wood bound together permanently
with adhesive, (pastes or resin) with the grain direction of one or more layers placed at 90o
to the
intervening layers.
Plywood is usually composed of an odd number of plies.
The moisture content of plies has to be in the range of 15% - 18% for effective use.
Advantages of Plywood
 The approximate equalization of strength properties along its length and width
 Very light in weight
 Easy to handle
 Highly resistive against defects
 Less change in dimensions with the change in moisture content.
 Impact resistance is high
Handout 6
 Plywood
 Hardboard
 Fibreboard
 Blockboard
commercial grade.
Plywood
to the
intervening layers.
 Easy to handle
Handout 6
 Plywood
 Hardboard
 Fibreboard
 Blockboard
commercial grade.
Plywood
to the
intervening layers.
 Easy to handle

 Bending properties are very high
 Very small cross sectional area gives larger strength compared to block of ordinary timber.
Uses of Plywood
 Doors
 Used as beautifying items with smooth finishes; cabinets
 Floors, stairs
But plywood cannot be used
 Where it will be in contact with ground or with water
 In areas where alkali or chemicals are present
 In areas where fire resistance in important
Particle board or chipboard
These boards are made with particles of wood (or other materials like rice husk, saw dust) embedded
in synthetic resins and subjected to heat with high pressure which could produce boards of thickness
6mm and above.
Advantages
 Large flat panels can be obtained
 Same properties in all directions
 Stable under fluctuating temperature and moisture contents
 Easily workable by hand and machine tools

Hardboard
Hardboard is made from wood that is pulped and compressed to make sheets usually 3mm thick. The
face surface is smooth and hard while the opposite side is rough with pattern or cross lines.
Fibreboard
The technology used to make fibreboard is a combination of those used for making particle board
and hardboard. For making fibreboards, wood chips are steamed to separate the fibres from each
other. These fibre products are blended with resin and wax and turned into sheets by passing through
a pressing machine under controlled heat and pressure.
They are suited for mass production of furniture, cabinets etc. and flush doors.

Blockboard
Blockboard is also known as batten boards or solid core plywood.
Blockboards are thicker than most of the plywoods and have a core made of strips of wood each not
exceeding 25mm in width, laid separately or glued or otherwise joined to form a slab with the
direction of the grains of each core blocks running in right angles to that of the adjacent block.
Laminates
Laminates are the products made by bonding together of two or more layers of materials.
Products such as glass laminates, composite glass laminates all come under this class. Special
laminates from plastics are also available in the market. These can be glued to wood to make the
surface aesthetic as well as heat resistant.
Since these laminates come in large width, furniture like large table tops can be made of joined wood
pieces and covered with these laminates to give an appearance of one piece furniture.

Cement
Handout 7
Cement is the most important material in building construction.
History of Cement
 Romans used a sort of cement made from volcanic ashes.
 In ancient Asia, it was based on lime and rice husks.
 What is generally referred as ‘cement’ is Ordinary Portland Cement (OPC). It was invented
by Joseph Aspdin in 1824.
 Manufacturing of cement was started in India in 1904, but was fully established only in 1912.
Portland Cement
Cement is manufactured from limestone and clay by the old wet process or the new dry process. In
the old wet process, the limestone is crushed and clay is dissolved by the addition of water. They are
again mixed together in correct proportions and very finely ground. The mixture is called ‘slurry’. It
is then conveyed into tanks and then to a long cylindrical rotary kiln where it is gradually heated to a
high temperature of 1300 to 1500o
C. In this process, it is converted to clinker (fused lumps), which is
then ground in ball mills and tube mills to an exceedingly fine powder to form cement.
However, in modern cement plants, the above wet process is being replaced by the dry or semi-dry
process, in which the limestone and shale are crushed to powder form and blended in correct
proportions. Then it is mixed in the dry form by means of compressed air. This mixture behaves like
a fluid (fluidized bed) and is sieved and sent to the calciner which converts it into clinker which is
ground to cement. The dry process consumes less fuel (100kg of coal per ton of cement compared to
350kg of coal for wet process). Modern cement plants incorporate a number of automotive devices
for quality control of the constituents of cement.
The main constituents in cement that give cementing properties are the following four compounds.
 Dicalcium Silicate 2CaO.SiO2 denoted as (C2S)
 Tricalcium Silicate 3CaO.SiO2 denoted as (C3S)
 Tricalcium Aluminate 3CaO.Al2O3 denoted as (C3A)
 Tetracalcium Aluminoferrite 4CaO.Al2O3.Fe2O3 denoted as (C4AF)
(Generally, the content of C2S is about 25% and that of C3S is about 45% of the cement)

Types of cement
1. Ordinary Portland Cement (OPC): is the basic cement used for general concrete.
2. Rapid Hardening Portland Cement: a finer cement used to give high early strength.
3. Low Heat Portland cement: used for massive concrete pours such as dams to reduce the
heat of hydration generated during the chemical reaction.
4. Sulphate Resisting Portland Cement: less affected by acid waters and other injurious
salts. Suitable for sewer works.
5. Coloured, blast furnace, pozzolanic, masonry, waterproof, hydrophobic, high alumina
and oil well cements.
Setting Action of Cement
When water is added to cement, the ingredients of cement react chemically and form complicated
compounds. Initially a cement paste is formed which slowly thickens. In about 30-45 minutes, it is
said to have reached its initial set. In about 10 hours, it becomes rock hard and is said to have
reached its final set. Compound gains further strength until 28 days (hardening period).
Storage of Cement
In major construction works, it will be always necessary to keep a good stock of cement at site. The
cement shall always be stored in such a manner as to be easily accessible for proper inspection. It
should be stored in a suitable weather-tight building which can protect it from dampness. It may be
stored in bags inside sheds made of concrete or steel. When storing cement in bags, the following
guidelines should be practiced.
 Long period storage should be avoided and storage during rainy seasons should be as
minimal as possible. The shed size is designed usually to hold the maximum quantity of
cement to be used in any two-consecutive weeks.
 Cement bags should not be piled against the wall. A space of 60cm should be left
between the exterior walls and the stacks. The distance between two consecutive stacks
should be the minimum to reduce circulation of air.
 They should be piled off the floor on wooden planks. A space of at least 10-20cm should
be left.
 The number of bags in one pile should not usually be more than ten to avoid lumping
under pressure. Otherwise it may be difficult to stack or remove them. However the stack
height should not be more than fifteen bags.
 Application of FIFO method for removal. The cement bags stacked first should be
removed first.
 Use no hooks when lifting cement bags.

 If different brands of cement are meant to be used on one site, they should be stacked
separately.
 Rolling the cement bags regularly, and when they are taken out of the stack for use.
Hydration of Portland Cement
 Hydration reactions that take place between finely ground Portland cement and water
is highly complex, because the individual cement grains vary in size and
composition.
 In the presence of water, silicates and aluminates form products of hydration which
over time produce a firm and hard mass.
 As hydration takes place at the surface of cement particles, it is the surface area of
cement particles which provide the material available for hydration. The rate of
hydration is controlled by fitness of cement. For a rapid rate of hydration a higher
fitness is necessary.
The basic characteristics of hydration of Portland cement may be described as follows.
 As long as the individual cement grains remain separated from each other by water, the
cement paste remains fluid.
 The products of the hydration reactions occupy a greater volume than occupied by the
original cement grains.
 As the hydration products begin to intergrow, setting occurs.
 As the hydration reaction continues, additional bonds are formed between the cement grains,
leading to strengthening of the system.
Physical Properties of Cement
Portland cements are commonly characterized by their physical properties for quality control
purposes. Their physical properties can be used to classify and compare Portland cements.
 Setting Time
 Soundness
 Fineness
 Strength
Setting refers to a change from liquid state to solid state. During setting, cement paste acquires some
strength. Setting is different from hardening. Setting time is determined by the Vicat Apparatus.
The water content has a marked effect on the time of setting. In acceptance tests for cement, the
water content is regulated by bringing the paste to a standard condition of wetness. This is called
‘normal consistency’

Concrete
Handout 8
Concrete is a major building material used in building constructions. It is used in all parts of a
building like foundations, superstructure and roofs. Concrete is prepared at site by hand mixing or
machine mixing. It is now available as a factory-made product known as ‘Ready Mixed Concrete’.
Advantages
 Economical
 Durable
 Fire resistant
 Ability to cast
 On-site fabrication
 High compressive strength
Disadvantages
 Low tensile strength
 Low ductility
 Volume instability
 Low strength-to-weight ratio
Constituents of Concrete
 Cement
 Fine Aggregate (sand)
 Coarse Aggregate (broken stones or gravel)
 Water
However, in modern constructions a large number of additives known as ‘concrete additives’ are
also added as ingredients of concrete to enhance its qualities required for various constructions. Some
of the additives used are,
 Plasticizers
 Accelerators
 Retarders
 Fibres
 Polymers
 Pozzolanic material

Preparation of Concrete
 Mixing of Concrete
The aim of mixing is to blend all the ingredients of concrete to form a uniform mass and to coat the
surface of aggregates with cement paste.
Ready Mixed Concrete: In this type ingredients are introduced into a mixer truck and mixed during
transportation to the site.
 Wet-Water is added before transportation
 Dry-water is added at site
Mixing at the site
 Hand Mixed
 Mixer Mixed
Water-Cement Ratio:
The ratio of the weight of water to the weight of cement mixed in concrete. Strength of concrete
increases with decreasing water-cement ratio.
Mixing time should be sufficient to produce a uniform mass of concrete. The time of mixing depends
on the type of mixer and also type of concrete.
 Undermixing: non-homogeneity
 Overmixing: danger of loss of water, breakage of aggregate particles
Mixing at the site
 Hand Mixed
 Mixer Mixed
Water-Cement Ratio:
Mixing at the site
 Hand Mixed
 Mixer Mixed
Water-Cement Ratio:

 Placing of concrete
Concrete is placed in moulds called formwork which made of wood, steel or plastic. As air voids
present in the concrete mix, it has to be compacted by proper rodding or using concrete vibrators.
 Compaction of Concrete
The process of compacting concrete is essential for the elimination of entrapped air. This can be
achieved by;
 Tamping or rodding the concrete
 Use of vibrators
Vibrators
Internal Vibrator: The poker is immersed into concrete. The poker is easily removed from point to
point.
External Vibrators: External vibrators are clamped directly to the formwork. Therefore strong, rigid
forms are necessary.

Systematic Vibration
Correct: Vertical penetration of a few inches into previous lift (which should not yet be rigid) of
systematic regular intervals will give adequate consolidation
Incorrect: Hazard random penetration of the vibrator at all angles and spacing without sufficient
depth will not assure intimate combination of the two layers.
 Setting of Concrete
After placing concrete in the formwork, it begins to harden. The initial stage of this hardening is
called ‘setting’ as in cements. However the setting time as defined by concrete technologies need not
to be the same as defined by cement technologies. There is no separate test specified for the setting
time of concrete.
 Curing of Concrete
Properties of concrete improve with age as long as conditions are favourable for the continued
hydration of cement. These improvements are rapid at early ages and continue slowly for an
indefinite period of time.
Curing is the procedure used for promoting the hydration of cement and consists of a control of
temperature and the moisture movement from and into the concrete.
The primary objective of curing is to keep
concrete saturated or as nearly saturated as
possible.

Curing Methods
Methods of supplying additional water to the surface of concrete during early hardening stages:
 Using wet covers
 Sprinkling
 Ponding
Methods of preventing loss of moisture from concrete by sealing the surface,
 Water proof plastics
 Use liquid membrane-forming compounds
 Forms left in place
Methods of accelerating strength gain by supplying heat & moisture to the concrete.
 By using live steam (steam curing)
 Heating coils
 Hydration of Concrete
These diagrams represent the formation of
pores as calcium silicate hydrate is formed.
 In diagram (a) hydration has not yet occurred and the pores (empty spaces between grains)
are filled with water.
 Diagram (b) represents the beginning of hydration.
 In diagram (c), the hydration continues. Although empty spaces still exist, they are filled with
water and calcium hydroxide.
 Diagram (d) shows nearly hardened cement paste. Note that the majority of space is filled
with calcium silicate hydrate.
 The hydration will continue as long as water and unhydrated compounds present in the
cement paste.

Dicalcium silicate also affects the strength of concrete through its hydration. Dicalcium silicate reacts
with water in a similar manner compared to tricalcium silicate, but much more slowly. The heat
released is less than that of tricalcium silicate because the dicalcium silicate is much less reactive.
The strength of concrete is very much dependent upon the hydration reaction just discussed. Water
plays a critical role, particularly the amount used. The strength of concrete increases when the water
content used to make concrete is low. The hydration reaction itself consumes a specific amount of
water. Concrete is actually mixed with more water than the needed amount to gain sufficient
workability.

Properties of Concrete
Handout 9
 Properties of fresh concrete
 Workability
 Consistency
 Segregation
 Bleeding
 Setting Time
 Unit Weight
 Uniformity
Workability: It is desirable that freshly mixed concrete is relatively easy to transport, place,
compact and finish without harmful segregation. Factors affecting workability are,
 Method and duration of transport
 Quantity and characteristics of cementing materials
 Aggregate grading, shape and surface texture
 Quantity and characteristics of chemical admixtures
 Amount of water
 Amount of entrained air
 Concrete & ambient air temperature
Consistency: Consistency is the fluidity or degree of wetness of concrete. It is generally dependent
on the shear resistance of the mass. Also consistency is a major factor indicating the workability of
fresh concrete.
Tests for measuring consistency are,
 Flow Test- measure the amount of flow
 Kelly-Ball Test- measures the amount of penetration
 Slump Test-Most widely used test
Segregation: Segregation refers to the separation of the components of fresh concrete, resulting in a
non-uniform mix. The primary causes of segregation are differences in specific gravities and sizes of
constituents of concrete. Moreover improper mixing, improper placing and improper consolidation
also lead to segregation.

Factors affecting segregation are,
 Sizes and proportions of particles
 High specific gravity of coarse aggregates
 Decrease in the amount of fine particles
 Particle shape and texture
 Water-cement ratio
Bleeding: Bleeding refers to the tendency of water to rise up to the surface of freshly placed
concrete. It is caused by the inability of solid constituents of the mix to hold up of the mixing water
as they settle down.
Undesirable effects of bleeding are:
 With the movement of water towards the top, the top portion becomes weak & porous (high
w/c). Thus the resistance of concrete to freezing-thawing decreases.
 Water rising up to the surface can carry fine particles of cement which weaken the top
portion. This portion is not resistant to abrasion.
 Water may accumulate under the coarse aggregates and reinforcement. These large voids
under the particles may leak to weak zones and reduce the bond between past and aggregate
or paste and reinforcement.
 It is caused by sedimentation (settlement) of solid particles and aggregates and simultaneous
upward migration of water.
The tendency of concrete to bleed depends largely on properties of cement. It is decreased by,
 Increasing the fineness of cement
 Increasing the rate of hydration
 Adding pozzolans
 Reducing the water content

 Properties of hardened concrete
The principle properties of hardened concrete which are of importance can be listed as,
 Compressive Strength
 Permeability
 Durability
 Shrinkage and creep deformations
 Response to temperature variations
Strength of concrete
The strength of a concrete specimen prepared, cured and tested under specific conditions at a given
age depends mainly on,
 W / C ratio
 Degree of Compaction
 Curing
Note:
 Thermal expansion of concrete matches that of steel. Even though the coefficient of
expansion of concrete depends on the aggregates used, its value with the common types of
aggregates is around 10x10-6
to 14x10-6
per degree of centigrade and that of steel is 13x10-6
per degree of centigrade. Hence, there is compatibility between the two in the usual range of
temperatures. This is one of the reasons that concrete and steel match well. Reinforced
concrete is exposed to large variations of temperature differences therefore the coefficient of
expansion of the aggregate and steel should not be more than 5.4x10-6
per degree of
centigrade.

Concrete Testing
Handout 10
There are many tests that are prescribed for concrete. Some of them are meant to test the quality of
fresh concrete while others are meant to test the strength of hardened concrete.
 Tests on Fresh concrete
The following are the important tests to be done on fresh concrete at the site as soon as it is
discharged from the mixer. They test the placing quality of concrete.
 Slump test ( for plastic workability)
 Flow test ( for quality of concrete with respective to cohesiveness, consistency and tendency
for segregation)
 Bleeding test
 Setting time
 Tests on hardened concrete
The following tests are needed to check the final product.
 Compression test for compressive strength
 Tension test for tensile test
 Flexure test for modulus of rupture

Slump Test
The standard apparatus for this test is the
slump cone as shown. It is used to measure the
workability of concrete.
 The slump cone is placed on a G.I. sheet with the person conducting the test standing with his
foot placed on each of the foot pieces.
 A quantity of concrete necessary to fill the cone is taken to a tray and thoroughly mixed
together as quickly as possible after the concrete is discharged from the mixer.
 The slump cone is filled in 3 layers. Every layer is evenly rodded 25 times.
 The top level of concrete is finally stuck off so that the cone is full of concrete.
 The cone is gradually lifted and concrete is allowed to slump.
 Measure the slump by determining the vertical difference between the top of the mold and
the displaced original center of the top surface of the specimen.

Compression Test
The compression test is used for specifying grade of concrete in design and for quality control of
field concrete.
 Preparation of specimen: The specimens are made in 15 cm cube moulds.
 Curing and Storage: The cubes are properly cured for 28 days.
 Method of testing: The dimensions and weight of cubes are first measured and tested in a
machine
Testing for Flexural Strength
The flexural tensile strength at failure or the modulus of rupture is determined by loading a concrete
beam specimen.
The results obtained are useful because concrete is subjected to flexural loads more often.

Defects of Concrete
Handout 11
 Concrete Consolidation
Inadequate consolidation can result in:
 Honey combs
 Excessive amount of entrapped air voids
 Sand streaks
 Placement lines (cold joints)
Honey Combs
Entrapped air voids
Sand Streaks Cold Joints
Defects of Concrete
Handout 11
 Honey combs
 Sand streaks
Honey Combs
Entrapped air voids
Defects of Concrete
Handout 11
 Honey combs
 Sand streaks
Honey Combs
Entrapped air voids

Efflorescence
The water leaking through cracks, faulty joints or through the area of poorly compacted porous
concrete dissolve some Ca(OH)2 compounded by leaching. After evaporation, white deposits of
calcium carbonate are left on the surface of concrete. These deposits are called efflorescence.
Concrete in aggressive Environment
At sites where alkali concentrations are high or may become very high, the ground water should be
lowered by drainage so that it will not come in direct contact with the concrete.
Aggressive Environments
 Sulphate Attack
 Chloride Attack
 Acid Attack
 Effect of Sea Water
 Efflorescence
 Resistance of concrete to fire
 Alkali-Aggregate reaction
Sulphate Attack

 The sulphates of Calcium, Sodium, Potassium and Magnesium are present in most soils, and
ground water.
 Agricultural soil and water contains ammonium sulphate, from fertilizer or from sewage and
industrial affluents.
 In marshy lands decay of organic matters leads to the formation of H2S, which is converted
into sulphuric acid by bacteria.
 Solid salts do not attack concrete, but when present in solution they can react with hardened
cement paste.
Methods of controlling sulphate attack
 Use of sulphate resisting cement
 Addition of Pozzolana
 Quality of cement
 Use of air-entrainment
 High pressure steam curing
 Use of high alumina cement
 Liming of polythene sheet
Chloride Attack
Due to high alkality of concrete protective oxide film is formed on the surface of steel reinforcement.
This protective layer can be lost to carbonation and presence of chloride in the concrete. The action
of chloride inducing corrosion of reinforcement is more serious than any other reasons.
Sea Water
Sea water contains sulpahtes and hence attacks concrete in a manner similar to the sulphate attack.
The deterioration of concrete in sea water is not easily characterized by the expansion, as found in
concrete in sulpahte attack. Calcium Hydroxide and Calcium sulpahte are considerably soluble in sea
water, and this will increase the leaching action.
Steps to improve durability of concrete in sea water:
 Use of pozzolana or slag cement is advantageous under such conditions.
 Slag, broken brick bat, soft limestone, or other porous, weak aggregates shall not be used.
 As far as possible, preference shall be given to precast members, plastering should be
avoided
 Sufficient cover to reinforcement, preferably 75mm shall be provided.
 Care should be taken to protect reinforcement from exposure to saline atmosphere during
storage, fabrication and usage. It may be achieved by treating the surface of reinforcement
with cement wash or suitable methods.

Mix Design of Concrete
Mix design is the process of selecting suitable ingredients of concrete & determining their relative
quantities with the objective of producing as economically as possible along with the properties such
as workability, strength and durability
Using less cement causes a decrease in shrinkage and increase in volume stability
Designing the right concrete mix
1. Choose the target slump
2. Choose the maximum aggregate size
3. Estimate the water and air content from the tables
4. Select the water-cement ratio.
5. Calculate the cement content by dividing the water content by the water-cement ratio.
6. Estimate the coarse aggregate content.
7. Estimate the fine aggregate content.
8. Adjust for aggregate moisture (wet aggregate can significantly reduce the amount of water to be
added)
9. Make trial batches to see what you've got

Metals
Handout 12
Nowadays metals are extensively used in the construction industry. Large commercial buildings use
structural steel. Construction fields make use of metal windows, doors, studs, beams, joists, wall facings,
roofing, plumbing, hardware, etc.
 Physical Properties of metals
• Heat conductivity
• Electric conductivity
• Luster(can be polished)
• High melting point
• High density (larger atomic size)
• Malleable (can be hammered into thin sheets)
• Ductile (can be stretched into wires)
• Usually solid at room temperature (except mercury)
 Chemical Properties of metals
• Have 1-3 electrons in the outer shell
• Corrode easily (react with O2)
• Lose electrons easily
• Form basic oxides
• Good reducing agents
Differences and similarities- metals and non-metals
Metals Non-Metals
Generally solids. (except: Mercury, gallium) Found in all three states
Heavy Generally light in weight
Hard and non brittle. Solids are hard but brittle.
Good conductors of heat and electricity Bad conductors of heat and electricity
Ductile and malleable Neither ductile nor malleable
High melting point and boiling point Low melting point and boiling point
Produce ringing sound on collision Do not produce ringing sound
Metals
Handout 12
Metals Non-Metals
Metals
Handout 12
Metals Non-Metals

Lustrous and can be polished Non-lustrous and cannot be polished
Types of Metals
Metals can be divided into two categories,
 Ferrous
 Non-ferrous
Ferrous Metals
 Ferrous metals contain iron (Fe) as the principal element.
 ‘Ferrous’ is an adjective used to indicate the presence of iron.
 Small amounts of other metals or other elements are added, to give the required properties.
 Most importantly, ferrous metals make up the most recycled materials in the world.
 These metals are primarily used for their tensile strength and durability (especially mild steel).
 Due to the high amounts of carbon used most ferrous metals and alloys are resistant to rust. Less
resistant to oxidation.
 Most ferrous metals also have magnetic properties, which make them very useful in creation of
large motors and electrical appliances. Stainless steel is an exception.
Name Composition Properties Uses
Mild Steel 0.15 to 0.30% carbon Tough, high tensile
strength, ductile.
Girders, Plates, nuts,
bolts, general
purpose.
High speed steel Medium carbon,
tungsten, chromium and
vanadium
Can be brittle. Retains
hardness at high
temperatures (700 o
C)
Cutting tools for
lathes.
Stainless Steel 18% chromium, and 8%
nickel added
Corrosion resistant Kitchen draining
boards, Pipes, cutlery,
aircraft, surgical
instrumentation
High Tensile Steel Low carbon steel, nickel
and chromium
Very strong and very
tough
Gears, shafts, engine
parts
High Carbon Steel 0.70 to 1.40% carbon The hardest of the carbon
steels. Less ductile, tough
and malleable
Chisels, hammers,
drills, files, lathe
tools, taps,
Medium carbon steel 0.30 to 0.70% carbon Stronger and harder than
mild steel. Less ductile,
tough and malleable
Metal ropes, wires,
garden tools, springs
Cast Iron 2 to 6% carbon Hard, brittle, strong,
cheap, self-lubricating.
Heavy crushing
machinery, machine
tool parts, gear
wheels, plumbing
fittings, manhole
covers
Wrought Iron 100% Iron Corrosive Gates, Fences

Non-ferrous metals
 The metals which do not contain iron.
 Most of these metals prevent continual corrosion, by forming a film over the surface from the
initially formed oxide
 Non-ferrous metals are much more malleable than ferrous metals.
 Non-ferrous metals are also much lighter: well-suited for use where strength is needed, but the
weight is problematic,
 Since they doe not contain iron, non-ferrous metals have a higher resistance to rust and corrosion.
Therefore gutters, water pipes, roofing, and road signs. etc are made of non-ferrous metals
 They are also non-magnetic, makes them perfect for use in small electronics and as electrical
wiring.
 As for recycling, aluminum is the third most recycled material in the world. However, many other
non-ferrous materials like copper, brass and lead are relatively scarce.
Name Composition Properties Uses
Aluminium Pure Metal Grayish- White, soft, malleable,
conduct heat and electricity,
corrosion resistant.
Air craft, boats, window frames,
saucepans, packaging and
insulation
Aluminium
Alloys
(Duralumin)
Aluminiun 4%
Copper 1%
Manganese
Ductile, malleable, work, hardness,
light, high strength
Aircraft and vehicle parts
Copper Pure Metal Red, tough, ductile, high electrical
conductor, corrosion resistant, can
work hard or cold.
Electrical wire, cables and
conductors, water and central
heating pipes and cylinders.
Printed circuit boards, roofs.
Brass Copper65%
Zinc 35%
Very corrosive, yellow in colour,
tarnishes very easily. Harder than
copper. Good electrical conductors
Castings, ornaments, valves,
forgings.
Lead Pure metal The heaviest common metal. Soft,
malleable, bright and shiny when
new but quickly oxidizes to a dull
grey. Resistant to corrosion
Protection against X- Ray
machines. Paints, Roof
coverings, Flashings.
Zinc Pure metal A layer of oxide protects it from
corrosion, bluish white, easily
worked
Makes brass. Coating for steel
galvanized corrugated iron
roofing, tanks, buckets, rust-
proofing tanks, buckets, rust
proofing paints
Tin Pure Metal White , soft, corrosion resistant Tin plate, makes bronze

Industrial Metal Products
Handout 13
Steel
Steel Alloys
Alloy agents are added to improve one or more of the following properties.
 Hardness
 Corrosion Resistance
 Workability
 Ductility
 Strength
Mechanical Testing of steel
Major tests are:
 Tension Test
 Torsion Test
 Impact Test
 Bending Test
 Hardness Test
Relationship between Stress and Strain
Relationship between Stress and Strain is derived on the basis of the elastic behaviour of material
bodies.
A standard mild steel specimen is subjected to a gradually increasing pull by the Universal Testing
Machine. The stress-strain curve obtained is as shown below.

A -Elastic Limit
B - Upper Yield Stress
C - Lower Yield Stress
D -Ultimate Stress
E -Breaking Stress
Elasticity and Elastic Limit:
Elasticity is the property of a body by virtue of which the body regains its original size and shape when the
applied force is removed. Most materials are elastic in nature to a lesser or greater extent, even though
perfectly elastic materials are very rare.
The maximum stress up to which a material can exhibit the property of elasticity is called the elastic limit.
If the deformation forces applied causes the stress in the material to exceed the elastic limit, there will be a
permanent deformation in it. That is the body will not regain its original shape and size even after the
removal of the deforming force completely. There will be some residual strain left in it.
Yield Stress:
When a specimen is loaded beyond the elastic limit the stress increases and reaches a point at which the
material starts yielding. This stress is called yield stress.
Ultimate Stress:
Ultimate load is defined as maximum load which can be placed prior to the breaking of the specimen.
Stress corresponding to the ultimate load is known as ultimate stress.
Working Stress:
Working Stress = Yield Stress/ Factor of safety
Modulus of Elasticity or Young’s Modulus (E)
Modulus of Elasticity is the ratio of direct stress to corresponding linear strain within the elastic limit. If p
is any direct stress below the elastic limit and e the corresponding linear strain, then
E = p / e.

Steel verses concrete in construction
Office buildings, hotels, sports complexes and other buildings have the purpose of bringing people inside
confidently. The goal is to keep occupants comfortable and safe, while keeping the cost of construction and
maintenance of the building low.
When selecting the main construction material for a building, many important factors have to be
considered.
1. Cost
2. Strength
3. Speed of erection
4. Design flexibility
5. Ductility-Mechanical
6. Chemical stability
7. Adaptability
8. Sustainability
9. Dimensional stability
10. Recyclability
11. Fire resistance
 Stability
Reinforced concrete is safer than steel and can resist explosions and high impacts. The weight of
concrete allows it to resist higher winds better than steel. Steel structures designed with redundancy,
(more support beams than required) can remain standing even if a portion of the building’s support
has weakened. Steel also can resist high winds because the material can bend.
Steel is ideal for seismic zones, since it can bend and absorb energy from earthquakes.
 Behaviour in fire
Concrete is notably safer and stronger than steel. It is able to resist fire for extended lengths of time
without losing structural integrity; whereas concrete structures are less likely to collapse in the event
of a fire.
Steel will both soften and melt when exposed to high temperatures for longer time periods.
Fireproofing sprays can be used to strengthen the steel available. Because of this, some building
codes do not let build steel structures without adequate concrete support, especially in densely
populated areas.
 Time Frame
Steel structures can take longer time to build than concrete structures. However, construction
contractors save time by fabricating steel structures off-site. Also, advances in steel fabrication have
fastened the steel construction process.

 Designs
Steel buildings offer greater design flexibilities than concrete buildings because the weight and
strength of the steel allow the designers to form different shapes. Concrete has little flexibility and lot
of weight. However, in composite work, concrete and steel are often used together to make the
structure more strong. Builders can also create steel with longer spans than with concrete, which
expands the construction possibilities.
 Availability of materials
Availability of materials depends on the country or the region.
 Coefficient of thermal expansion
Both steel and concrete have similar coefficients of thermal expansions. Therefore both materials
expand simultaneously without performing any cracks or failures.
Aluminium
Aluminium is now utilised for a variety of applications in building construction and is the material of
choice for curtain walling, window frames and other glazed structures. It is extensively used for
rolling blinds, doors, exterior cladding and roofing, suspended ceilings, wall panels and partitions,
heating and ventilation equipment, solar shading devices and complete prefabricated buildings.
Structures like offshore living quarters, helicopter decks, balustrades, scaffolding and ladders, are
also commonly made of aluminium.
Properties of Aluminium products
 Durability: Aluminium building products are made from alloys, which are weather-proof, corrosion
resistant and immune to the harmful effects of UV rays, ensuring optimal performance over a very
long serviceable lifetime.
 Design flexibility: The extrusion process offers an almost infinite range of forms and sections,
allowing designers to integrate numerous functions into one profile. Rolled products may be
manufactured flat, curved, shaped into cassettes, or sandwiched with other materials. In addition,
aluminium can be sawed, drilled, riveted, screwed, bent, welded and soldered in the workshop or
building site.
 High strength-to-weight ratio: This unique property allows architects to meet required performance
specifications, while minimising the dead load on a building’s supporting structure. Also, the
material’s light weight makes it easier to transport and handle on site, reducing the risk of work-
related injury.
 Hundreds of surface finishes: Aluminium can be anodised or painted in any colour, to any optical
effect, using any number of surface touches, in order to meet a designer’s decorative needs. Such
processes also serve to enhance the material’s durability and corrosion resistance, as well as
providing an easy-to-clean surface.

 High reflectivity: This characteristic feature makes aluminium a very efficient material for light
management. Aluminium solar collectors can be installed to lower the energy consumption for
artificial lighting and heating in winter, while aluminium shading devices can be used to reduce the
need for air conditioning in summer.
 Heat conductivity: Aluminium is a good conductor of heat, which may be a disadvantage in some
applications. However, this property can easily overcome by the profile design and the use of thermal
breaks made of low conductivity materials.
 Fire safety: Aluminium does not burn and is therefore classed as a non-combustible construction
material. Aluminium alloys will nevertheless melt at around 650°C, but without releasing harmful
gases. Industrial roofs and external walls are increasingly made of thin aluminium cladding panels,
intended to melt during a major fire, allowing heat and smoke to escape and thereby minimising
damage.
 Optimal security: Where high security is required, specially designed, strengthened aluminium
frames can be used. Also light in weight.
 Low maintenance: Besides routine cleaning for aesthetic reasons, neither bare nor painted
aluminium requires any maintenance, which translates into a major cost advantage over the lifetime
of a product.
Some Applications
External
 Roofing or tiles
 Chimney
 Solar panel
 Gutter
 Doors
 Cassette
 Fence
 Shutter
 Balcony
 Window frames and window sill
 Garage door
 Shading devices
 Curtainwall

Internal
 Ceiling system
 Doors
 Elevator cab
 Floor
 Furniture
 Partition walls
 Signs

Copper
Nowadays copper has a very high demand in the related field of architecture, building construction
and interior design including roofs, flashings, gutters, downspouts, domes, spires, vaults, wall
cladding and building expansion joints.
Properties of Copper products
 Corrosion Resistance: As a construction metal copper provides excellent corrosion resistance.
Copper surfaces form tough oxide-sulfate patina coatings that protect underlying copper surfaces and
resist corrosion for a very long time.
Copper corrodes at negligible rates in unpolluted air, water, de-aerated non oxidizing acids, when
exposed to saline solutions, alkaline solutions and organic chemicals.
 Durability: Copper roofs are extremely durable in most environments. Primarily because of their
protective film that forms on copper surfaces.
 Low thermal movement: Properly designed copper roofs minimize movements due to thermal
changes. Copper’s low thermal expansion, 40% less than zinc and lead, helps to prevent deterioration
and failure. Also, copper’s high melting point ensures that it will not creep or stretch as some other
metals do.
 Low maintenance: Copper does not require cleaning or maintenance. It is particularly suited for
areas that are difficult or dangerous to access after installation.
 Light weight: Copper claddings offer additional opportunities to reduce the weight of copper
structures
 Ventilation: Copper does not require complex ventilation measures. It is suitable for both
unventilated ‘warm’ and ventilated ‘cold’ roof constructions.
 Lightening Protection: Copper and its alloys are the most common materials used in residential
lighting protections, however in industrial, chemically corrosive environments, the copper may need
to be clad in tin. Copper effectively facilitates the transmission of lightening energy to the ground
because of its excellent electrical conductivity.
 Wide range of finishes: It is sometimes desirable to chemically alter the surface of copper or copper
alloys to create a different colour. The most common colour produced is brown finish for brass or
bronze and green or patina finishes for copper.

 Cost effectiveness: Performance, maintenance, service life and recovery costs from recycling are the
factors that determine the cost effectiveness of building components. While copper’s initial cost is
higher than some other metals, it is usually does not need to be replaced during the lifetime of a
building.
Protection of metals against corrosion
What is corrosion?
Corrosion is the deterioration of materials by chemical interaction with their environment. The term
corrosion is sometimes also applied to the degradation of plastics, concrete and wood but generally
refers to metals. The most widely used metal is iron (usually as steel).
Failures of various kinds and the need for expensive replacements may occur, even though the
amount of metal destroyed is quite small. Some of major harmful effects of corrosion can be
summarized as follows.
1. Reduction of metal thickness leading to loss of mechanical strength and structural failure or
breakdown. When the metal is lost in localized zones so as to give a crack like structure, very
considerable weakening may result from quite a small amount of metal loss.
2. Hazards or injuries to people arising from structural failure or breakdown(e.g. bridges,
aircrafts, ship)
3. Reduced value of goods due to deterioration of appearance.
4. Mechanical damage to valves, pumps…etc or blockage of pipes by solid corrosion products.

Corrosion Prevention
 Cathodic Protection:
A technique used to reduce corrosion of a metal surface by making it act as a cathode, while having
a second metal in direct contact with it which is easily oxidizing (second metal acts as the
anode).This means that the material with less corrosion potential will experience corrosion at a
higher rate than the material with high corrosion potential.
Galvanization is a localized form of cathodic protection where the strongest reducing agent acts as a
sacrificial metal. For example, this means that the second material eg: zinc, will undergo the majority
of the corrosion rather than the material that is being preserved such as the iron pipe line.
 Paint or bituminous coating:
These waterproof paints or coatings are applied to protect metals from water, oxygen and direct
sunlight. For structural steelwork also these tar products are widely used. Also suitable for gates,
benches, tanks, ground pipes, above ground pipes.. etc. This method is the most economical method
but long lasting.
 Chemical Inhibition:
A corrosion inhibitor is a chemical additive, when added to a corrosive aqueous environment,
reduces the rate of metal wastage.
1. Anodic Inhibitors: an anodic inhibitor interferes with the anodic process. E.g.
orthophosphate, nitrite, ferricyanide and silicates.
2. Cathodic Inhibitors: major cathodic reaction is reduction of oxygen E.g. Zinc Ions.
3. Adsorption Inhibitors: many organic inhibitors work by an adsorption mechanism. E.g.
amino, carboxyl, phosphonate functional groups.
4. Mixed Inhibitors: E.g. Zinc, chromate ions

Plastics
Handout 14
All plastics are polymers of carbon compounds. They are called plastics because their resins are capable
of plastic deformation when heat and pressure are applied on them. Their molecular structure consists of
long chains of large molecules loosely tangled together. This causes plastics to have light weight and lack
of stiffness. It has toughness and good tensile strength. A large no. of plastics can be manufactured by
changing the composition, length and character of their chains. There are more than 10, 000 varieties of
plastics and their number is increasing everyday as new ones are being invented.
Polymerization of Plastics
The process of producing resins of plastics is called polymerization. A substance containing one primary
unit is a monomer. Combining thousands of monomers as a long chain of molecules to form another
complex molecule is called polymerization.
Classification of Plastics
Plastics can be classified according to its thermal property or mechanical property. According to thermal
property, plastics can be classified as follows.
Thermoplastics:
 Soften when heated without undergoing any chemical changes.
 Possible to remold and recycle these plastics by applying heat and pressure without
affecting the material’s properties.
 Associated with weak van der waals forces.
 These are rigid, flexible and high dense materials.
Advantages
 Highly Flexible
 Highly recyclable
 Aesthetically superior finishes
 High impact resistance
 Chemical resistance
 Remolding/reshaping capabilities
 Eco-friendly manufacturing
Disadvantages
 Not resistant to higher temperatures
Examples
 Polyvinyl chloride (PVC)
 Acrylics (Perspex)
 Polycarbonate
 Polyethylene (polythene)
 Nylon

Thermosets:
 Thermosetting materials are generally stronger than thermoplastic materials due to its three-
dimensional network of bonds (cross-linking).
 Forms an irreversible chemical bond.
 Ideal for high-heat applications such as electronics and appliances
 Urea-formaldehyde foam used in plywood, particleboard and medium-density fibreboard
 Bakelite, a phenol-formaldehyde resin used in electrical insulators and plastic ware
 Comprised of giant molecular structures.
Advantages
 More resistant to high temperatures than thermoplastics
 Chemical resistance.
 Resistance to deformation
 Excellent aesthetic appearance
 Cost-effective
 Structural Rigidity: High levels of dimensional stability
Disadvantages
 Cannot be recycled
 Cannot be remolded or reshaped
 More brittle.
 Undergo chemical changes when heated
 These materials char when heated to higher temperatures
Examples
 Polyester (terylene)
 Bakelight
 Formica

Properties of plastics
 Appearance: It can be made in attractive colours.
 Chemical resistance: good resistance against almost all chemicals.
 Dimensional stability: good dimensional stability as with other engineering materials.
 Durability: many plastics are quite durable if protected
 Electric Insulation: used for plugs, switches
 Easiness in fixing
 Finishing
 Light in weight: because of their molecular structure, plastics are light
 Maintenance
 Thermal conductivity: similar to wood
 Thermal stability: stable under low temperatures
Disadvantages of plastics
 Non- biodegradable.
 High Thermal expansion: about ten times as much as steel.
 High creep properties
 Lack of durability: under direct sunlight, they are not durable.
 Lack of fire resistance: all plastics cannot withstand high temperatures. They may also emit toxic
fumes in case of fire.
 Low melting point: Thermosetting plastics are less affected by heat and burn at high
temperatures.
 Non- suitability for structural members: Plastics has not yet become a popular material for
fabrication of structures. For structural use, they are usually used only with embedded metals like
steel.
Some Plastics in common use
1. Vinyls – Polyvinyl chloride (PVC)
Ethyne is a member of the alkyne group. HCl reacts with ethyne to form vinyl chloride. Vinyl chloride is
polymerized to polyvinyl chloride consisting of a long molecular chain represented by CH – CHCl group.
PVC is represented as - CH2 - CHCl – CH2 – CHCl - CH2-------CHCl------
PVC is one of the cheep plastic materials. It is available in three forms, ordinary, plasticized and post-
chlorinated. The last one is more resistant to heat up to 120o
C which makes it suitable for hot water pipes.
PVC can also be made rigid by compounding. One of its popular uses is for pipes for all situations
because of its high resistance to most of the chemicals. They are also used to make doors, windows, floor
coverings, wall coverings, etc.
Advantages of PVC pipes
 Resistant to corrosion to chlorides in water. Where GI pipes tend to corrode, PVC pipes do not
get affected by these salts.
 PVC pipes cost much less than metal pipes
 Light in weight, easy to transport and install. The fixing devices for PVC pipes are also simple.

 PVC pipes are smooth inside and have good flow characteristics to convey liquids.
 PVC is a good insulator. PVC pipes are extensively used for concealed electrical conduits. They
are not affected if buried in brickwork, concrete etc.
 It is easy to make leak proof joints in PVC pipes. Cutting them and joining them is easy.
 PVC doors and windows are becoming popular for the following reasons.
o They are termite-proof
o Used to make airtight doors and windows necessary for air-conditioned rooms
o It is an alternate to valuable timber of good quality which is getting scarce.
o They are unaffected by rain when used as external doors.
Disadvantages of PVC pipes
 Some of the PVC pipes are brittle and get broken easily in compression
 They creep under loads much more than metals
 Being thermoplastic, ordinary PVC cannot be used for higher temperatures. They are best suited
for temperatures up to 80o
C under normal pressure.
 They have high coefficient of expansion. (ten times that of steel). Sufficient care should be taken
for their expansion. (need to be provided with room for movement)
 They do not weather well in direct sunlight. When installed they should be protected from the
direct rays of the sun.
2. Unplasticized polyvinylchloride (uPVC)
When PVC is compounded with rubber stabilizers, filters etc. it becomes less brittle and more
temperature resistant. This process is called plasticizing. Pipes with less than 4% plasticizers are called
unplasticized PVC pipes or uPVC or rigid plastic pipes.
However, it is susceptible to physical damage if exposed above ground and it becomes brittle when
exposed to ultraviolet rays. The pipe is light to handle, but it is too bulky for aesthetically acceptable
internal use in domestic buildings. It is used extensively around the world for drainage (waste or soil and
storm water) applications.
uPVC is available with a solvent cement or rubber (elastomeric) ring jointing system for internal or
external drainage systems. Caution must be exercised when using them close to water heaters and similar
heat sources. In addition to the inherent problems associated with the expansion and contraction of
plastics, the material will soften and deform if exposed to higher temperatures.
Advantages
 Flexibility
 High tensile strength
 Corrosion resistance
 Chemical resistance
 High stiffness
 Cost effectiveness

Use of plastics for doors and windows
As good timber is becoming scarce and costly,
traditional wood and door systems are being
substituted by steel and aluminum structures.
Nowadays, thermovinyl polymer sections reinforced
with steel have also come to the market replacing
these items. They are especially applicable in coastal
areas where corrosion of steel windows and doors is
a serious problem.
Use of plastics for roofing
Corrugated plastic roofing sheets with and without
fibre reinforcements are nowadays extensively used
for roofing of buildings. Sheets with reinforcements
last longer. As they are weak in ultraviolet radiation
nowadays, we get such sheets that are especially
treated on the exposed side for such radiation. Such
treatments protect the sheet from effects of
ultraviolet radiation of sunlight.
Polyethylene (polythene) water tanks
Tanks made of high-density or low-density
polythene (HDPE or LDPE) are used to make
overhead water tanks. The plastic is usually
compounded with up to 2.5 percent carbon black to
make it more resistant to the ultraviolet rays from
the sun as these tanks are usually kept exposed.
Addition of carbon makes it black in appearance.
These tanks are generally square or cylindrical in
shape. The cylindrical tanks are manufactured by
rotational molding process. Each tank is of a single
piece construction.
Plastics compounded with rubber.
We have already seen that ordinary PVC pipes are
developed to unplasticized (UPVC) pipes. When
PVC is compounded with synthetic rubber and
other compounds, it becomes plasticized and
becomes less brittle. Similarly, polystyrene plastics
alone are very brittle but by adding a butadiene
rubber compound, their performance is greatly
improved.

Some Important facts
Plastic pipes are light, easily handled, transported and require fewer joints than metal pipes when utilized
in long lengths. This in turn can reduce transportation and handling costs.
It is important for plumbing systems that different pipe types remain separated and not intermixed with
similar products. For example, rainwater or storm water drainage pipes and fittings should not be used for
sanitary plumbing (soil, waste or vent pipe) applications. Conversely soil, waste, vent pipes and fittings
could be used for rainwater or stormwater, but they are unnecessarily expensive for those applications.
By using different coloured pipe lines and fittings to define the designated application of the product and
to assist installers for future identification cross connections can be prevented. (Standards and colour
codes).
For example, PVC pipe and fittings are easily manufactured in various colours. Other materials that are
not so easy to colour may rely on a stripe of colour set onto the pipe during extrusion or painted bands
and labels applied after installation, with specific markings or instructions with regard to fittings, etc.
Other authorities, such as electricity and gas providers, may also utilize colour coding for their buried
pipelines.
Why copper is still preferred to plastic for many plumbing work?
Copper tubing, due to its thinner wall section, is relatively light to handle and is available in
coil form or straight lengths as required. When assembled and installed correctly it can blend into
building structures without difficulty. Copper piping systems can be assembled with the aid of
compression fittings, couplings, or by lead-free solder or brazing.
Copper tube or pipe is also useful for hot water supply systems. However, heat loss can
become an issue if adequate insulation is not provided. As with all metallic materials, the risk of
electrolytic corrosion should be considered. System designers must be aware that water flows through
copper tube piping systems must not exceed 3 meters per second. When this occurs there is a high risk
that the internal bore of the piping system will be eroded by high flow and velocity scouring. Due to its
electrical conductivity there is a need for care to ensure that grounding connections are separated from
piping systems and any electrical wiring.

Site Evaluation
Handout 15
A site investigation is the overall process of discovery of information, appraisal of data, assessment
and reporting of the existing site conditions that affect the design and construction of the intended
building. This helps to identify the extent of work involved in construction.
A site investigation is a preliminary examination or survey of the proposed site. It involves gathering
of information required for proceeding with the proposed construction. This helps to locate the
construction properly and to ascertain ground conditions. The principle objectives for a construction
design site are:
 Suitability: Are the site and surroundings suitable for the proposed construction?
 Design: Obtain all the design parameters necessary for the works.
 Construction: Are there any potential ground or ground water conditions that would affect the
construction?
 Ground features: Slopes and ground failures such as landslides, marshy lands, mining …etc
 Materials: Are there any materials available on site? What quantity and quality?
 Effect of changes: How will the design affect adjacent properties and the ground water?
 Identify alternatives: Is this the beat location?
It is clear that a site investigation should be undertaken for every site, since without a properly
procured, supervised and interpreted site investigation, hazards which lie in the ground beneath the
site cannot be known.
Site investigations are conducted to assess general site conditions to ascertain any anticipated
problem that might arise during the construction. It is usual to observe the actual site and ground
problems with particular reference to:
 Terrain: physical features of land
 Vegetation: plant life or plant cover of the site
 Swamps: possibility of being submerged in water
 Water runoff: water from rain or melting snow flowing through the site.
 Ground layer formation and any rock exposures.
 Topographic characteristics: flat land, hilly areas, swamps or pits…..etc
 Location of ground water table
 Photographs of the proposed site
 Interviewing local residents for any relevant information
The first step is to inspect the site and its vicinity to get a preliminary idea of the site conditions. This
includes the study of the existing buildings in the neighborhood and if possible the type of their
foundations. Prior to site investigation, as much information as possible should be collected about the
site. This includes study of ordnance maps, land archives, Ariel photographs of the area… etc to
know the history, nature and suitability of site.

The types of obstructions that should be considered include,
 Existing foundations (ground slabs, bases, piles, basements…)
 Buried tanks (concrete, metal)
 Services (below, above ground)
 Water ways (rivers, culverts,)
 Tunnels (services, subways, transport)
 Adjacent properties
Services
 Electricity Cables
 Gas Mains
 Water Mains
 Sewers
 Telecommunication cables
Soil Investigation:
Soil investigation is carried out to provide design recommendations for the most suitable type of
foundation. An investigation must possess sufficient information about the physical properties and
arrangement of underground materials. The field and laboratory investigations required to get these
essential information is known as soil exploration. The process of soil investigation includes the
following steps:
 Planning the details and sequence of operations
 Collection of soil samples from the field
 Conducting all field tests determining the strength, compressibility…etc characteristics of the
soil
 Study of ground water level conditions and collection of water samples for chemical analysis
 Testing all samples of rock, soil and water in the laboratory
 Preparation of drawings and charts
 Analysis of the results of the tests
 Preparation of report
Test Pits: Test pits are dug by hand or by excavating machines. The size of the pit should be such
that a person can easily enter the pit and have a visual inspection. Both disturbed and undisturbed soil
samples are collected from the pit for detailed analysis.

Boring: In this process, bore holes are made in the ground and the soil samples are collected.
Boring helps in obtaining:
 Extent of strata of soil/rock
 Nature of strata and the engineering properties of the soils
 Location of ground water table
The depth and number of boreholes will depend upon the type of the structure and nature of the soil
as obtained from preliminary examination. The depth of boreholes is governed by the depth of the
soil affected by the loading. As a rough estimate, it is advisable to investigate the subsoil to a depth
of at least twice the width of the anticipated largest size of the foundation. In case of a pile
foundation, the depth of boring should extend into the bearing stratum.
Methods of Boring for soil Investigations:
Auger Boring: Auger is a device which is used for manual boring. For shorter depths hand augers
or manual augers are commonly used. For deeper depths other auger such as helical auger or post
auger…. etc are commonly used. For the diameter range of about 300mm to 1m the type of auger
used is power auger.
The examination of the soil for ordinary buildings can be done by a post hole auger. The auger is
held vertically and is driven into the ground by rotating its handle. At every 30cm of depth, the auger
is taken out and the soil samples collected.

Wash Boring: Wash boring is commonly used for boring in difficult soils. The hole is advanced by
an auger and then a casing pipe is pushed to prevent the sides from caving in. A stream of water
under high pressure is forced through the rod into the hole. The loosened soil in suspension in water
is collected in a tub. This method is effective for cohesive soil and does not comparatively cost much.
This method is not suitable for collapsible soil.
Percussion Boring- In this method, the substrata is broken by repeated blows by a bit or chisel.
Water is circulated in the hole and the slurry is bailed out of the hole. Suitable for most projects,
cable percussive boreholes are a common method of site investigation.

Material and construction technolgy level 5 civil

Material and construction technolgy level 5 civil

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