“Military Institute of Science & Technology (MIST)

Environmental, Water Resources, and Coastal Engineering Department

”
EWC 201: Construction Materials
3 Credit Hours
GLASS
GLASS: INTRODUCTION
• Glass is any structure or mixture of substance that has solidified from the
liquid state without crystallization.

• Elements, compounds and mixture of wide varying composition can

exist in the glass state.

• No definite chemical compounds can be identified in glass. It is an

amorphous substance having a homogeneous texture.

• ‘Glass’ ordinarily refers to material which is made by the fusion mixture of

Silica, the basic oxides and a few other compounds that react either
with silica or with the basic oxide

• ‘Glass’ may also be defined as a hard, brittle, transparent or translucent

material chiefly compound of silica, combined with varying proportions
of oxides of Sodium, Potassium, Calcium, Magnesia, Iron and other
materials.
CONSTITUENTS OF GLASS & THEIR FUNCTIONS
 Silica:

• It is the principle constituent of glass

• If silica alone is used in the manufacture of glass, it could be fused only

at a very high temperature, but it would give a good glass on cooling

 Sodium or Potassium Carbonate:

• It is an alkaline material and forms an essential component of glass

• It is added in suitable proportion to reduce the melting point of silica

and to impart viscosity to the molten glass
 Lime:

• It is added in the form of chalk

• It imparts durability to the glass

In place of lime, sometimes lead oxide is also added to make the glass bright
and shining

 Manganese Dioxide:

• It is added in suitable proportion to correct the colour of glass due to the

presence of iron in the raw materials of glass

• It is also called “Glass maker” soup

 Cullet:

• It is the old broken glass of same type which is intended to be prepared

• It is added in small quantity to provide body to the glass

 Coloring Substance:

While manufacturing a coloring glass, a suitable coloring substance is added

at fusion stage to provide the desired color to the glass. The various coloring
substances for manufacturing glass at different colors are given below:
Colour Colouring Substance
Black Cobalt, Nickel, Manganese Oxide
Green Chromic Oxide
Red Cuprous Oxide, Selenium
Violet Manganese dioxide
White Cryolite, Tin Oxide
Yellow Cadmium Sulphate
PROPERTIES OF GLASS
• No definite crystalline structure

• No sharp melting points

• Absorbs, reacts and transmits light

• Affected by alkalis

• An excellent electrical insulator at elevated temperatures

• Extremely brittle

• Available in beautiful colors

• Not affected by air and water

• Not easily attacked by ordinary chemical reagents

• Capable of being worked in several ways

• Can take up a high polish

• Possible to weld pieces of glass by fusion

• It can be lighter than cork or softer than cotton or stronger than steel
REQUIREMENTS FOR COMMERCIAL GLASS
• The materials must melt at commercially obtainable temperature

• The molten mixture must remain in the amorphous or non-crystalline

condition after cooling

• The fluidity of the molten glass must persist to a sufficient extent to

permit the formation of desired shaped while the glass is cooling

• The glass must be reasonably permanent in the use for which it is

intended.

Glass with a high proportion to Sodium Oxide is more readily attacked by

water and acids than glass that contains less sodium oxide and more
lime and magnesia. Glasses low in basic oxides are less readily attacked.
MECHANICAL PROPERTIES

Refractive index 1.46-2.179

Specific index 2.125-8.12
Compressive strength 600-1200 MN/m2
Tensile strength 27-700 MN/m2
Thermal conductivity 0.0018-0.0028 cal/cm⁰C/sec
Expansion co-efficient 8x10-7 – 140x10-7 cm/cm/⁰C
Softening point 500-1510⁰C
Annealing point 350-890⁰C
Volume resistivity 108 – 1018 ohm/cm3
Dielectric constant 3.7-16.5
• Strength: Glass is weak in tension but it is four to six times strong in
compression. Glass should therefore be used under compressive loads.
Strength depends upon surface conditions, cross-section and amount of
addition etc.

• Hardness and Brittleness: Some glasses can scratch steel. The relative value
of hardness can be evaluated by scratch or abrasion test. For ordinary
purposes the hardness of glass is a function of its tensile strength. When
glass is fixed, it bends only a little, then shatters. There is no plastic
deformation.

• Thermal endurance: The lower co-efficient of expansion and the thinner

the pieces the less likely it is to break under the thermal shock. Glass does
not break from thermal causes but from the tensile stresses set up by the
temperature gradient
ELECTRICAL PROPERTIES
• Conductivity: Conductivity depends on composition, temperature and
surface conditions. Sodium and Potassium ions are largely responsible for
imparting electrical conduction. Na2O and K2O increase the conductivity.
Al2O3 increases conductivity slightly; ZnO, PbO, MgO, Fe2O, BaO, B2O2 and
CaO decrease the conductivity. But the function of the Calcium ions or
the mechanism of conduction in an alkali-free glass is not known. In high
alkali glasses, the surface conductivity may exceed the volume
conductivity. The presence of CO2, SO2, H2S, solids and mineral soils also
affects the surface conductivity.

• Dielectric constant, Power factor, Dielectric loss: The dielectric constant k

of the glass varies from 3.7 to 16.5 and remains relatively constant over a
wide frequency, the square of the voltage gradient, and to the product
of dielectric constant and the power factor. For the conditions of high
frequency or high voltage or both, the value of K should be kept as low as
possible.
 Both the dielectric constant and the power factor can be varied by
changes in the glass composition by a ratio of more than 200 to 1. Two
general glasses are available: those with high dielectric constant and low
power factor, and those with low dielectric constant and low power
factor.

• Dielectric strength: Electrical breakdown is influenced by the characteristics

of dielectric, the thickness, the duration of stress, temperature and edge
effects, the surrounding medium and the characteristics of the voltage,
whether direct or alternating; thermal failure of a dielectric is a result of
internal heating, which causes it to become a conductor. Alternating
currents cause failure at a lower voltage than direct current do.
CLASSIFICATION OF GLASS
As per composition and properties glass may be classified as:

1. Soda-lime or Crown glass

2. Flint Glass

3. Pyrex or heat resistant glass

 Soda-lime or crown glass:

• It is the cheapest quality of glass

• Its composition is not rigidly fixed, it can be varied both as to the amount of
ingredients and chemical compounds used.
** Composition by weight: Sand 75 parts, lime 12.5 parts, soda 12.5 parts,
alumina 1 part and waste glass 50 to 100 parts.

• It is easily fusible at comparatively low temperature

• It is available in clean and clear state

• It is possible to blow or to melt articles made from this glass with the help of
simple sources of heat

Uses: Its principle uses are for window glass, plate glass and container glass
 Flint glass:

• It contains various proportions of Lead Oxide to make it suitable for various

purposes
**Lead provides brilliance and high polish which makes the glass available
for special purposes
**Composition by weight: Sand 100 parts, red lead 70 parts, Potash 32
parts, waste glass 10 parts

• It liquefies at a lower temperature than soda lime glass and has better luster

• Owing to ease with which lead compounds are reduced. The glass must be
melted in an oxidizing temperature

Uses: For better quality of table wares; for optical glass, electric lamps,
thermometers, containers for food etc.
 Pyrex or heat resistant glasses:

• Elimination of basic oxides and inclusion boron oxide produce a glass

which is resistant to thermal shock and to attack by water and acids
**Composition by weight: Silica 80 parts, boron oxide 14 parts, sodium
oxide 4 parts, alumina 2 parts, with traces of potassium oxide, calcium
oxide and magnesium oxide.

• The temperature required to melt the glass is so high that it has to be

heated in the electric arc

Uses: Borosilicate glass are used extensively for cooking utensils and
laboratory wares
SPECIAL TYPES OF GLASS
 Annealing glass:

To prevent glass particles becoming too brittle and falling into pieces
and the slightest shock, they are kept while still hot in an annealing
furnace to cool very slowly. The longer the annealing period, the
better the quality of the glass.

 Sheet glass:

• It is roughly composed of 100 parts sand, 35 parts limestone or

chalk, 40 part soda and 50 part waste glass

• It is made by blowing glass in hollow cylinder, spitting the cylinder

and finally flattening it over a plane surface
• It is manufactured in thickness varying from 1.5 to 5 mm and sizes up to
1.5x1 meter

Uses: It is generally used for doors and windows

 Plate glass:

• Composition: White sand 100 parts, soda carbonate 33 parts, slaked lime
14 parts, manganese peroxide 0.15 parts, waste glass 100 parts

• It is made by pouring white hot glass over an iron table and rolling it to a
uniform thickness under heavy roller

• It is thicker than sheet glass and its thickness varies from 5 to 25 mm and
sizes up to 275cm x 90 cm

• It is stronger and more transparent to glass sheet

• Plate glass includes transparent, translucent, opaque and structural
glasses

Uses: It is used for making looking glasses, wind screens of motors, car
skylights and glass houses. It is also used for sales counter and table tops
after being laminated with plywood or metal sheet

 Fluted glass:

When there are corrugations on one side of the plate glass then it is known
as fluted glass. The other side is wavy but smooth. The light is entered
without the glare of the sun

Uses: It is used in situations where it is desirable to secure privacy without

obstruction of light. It is more used for skylight roofs and for window of
railway stations and factories
 Ground glass:

• It is made either by grinding one side, or by melting powdered glass

upon it

• This glass is mostly translucent

• This type of glass is known as frosted glass or obscured glass

Uses: This glass is used in situations where light is required without

transparency. It is normally used for window panes and bathroom
ventilators etc.
 Wired glass:

• It is glass with wire netting or similar strengthening material embedded

in it during manufacture. This is why this glass is known as reinforced
glass

• It resists fire better than ordinary plate glass

• In case the glass is fractured, it does not fall into pieces

Uses: It is used for skylight and roofs, for fire resisting doors and windows
 Safety glass:

• It is produced by sandwiching sheets of celluloid or other transparent

plastic between two sheets of glass and sticking the whole
combination together by means of colorless and heat resisting glues

• Wired glass falls into this category

 Bullet Proof glass:

• This glass is made of several layers of plate glass and alternate layers
consist of vinyl resin plastic. The outer layers of plate glass are made
thinner than the inner layers. Special care is to be taken for heating
and cooling of layers during manufacture
• Thickness varies from 15 mm to 75 mm or more

• This glass will not allow to bullet fierce through it

Uses: It is extensively used for glazing bank teller, cages, cashier booths,
jewelry stores, display cases etc.

 Insulating material:

It is transparent glass unit composed of two or more plates, of glass

separated by 6 to 13 mm of dehydrated captive air, hermetically sealed
inside, is scientifically cleaned and dried. Insulating glass provides a high
resistance to heat flow. The sealed air makes the co-efficient of heat
transmission of the glass low and hence keeps the apartment cool in
summer and warm in winter.
 Foam glass:

• It is prepared from powdered glass to which is added the desired quantity

of carbon or any gas which makes the mass porous and light in weight

• It is also waterproof

• It can be easily cut and worked with common masonry tools

Uses: It is used for sound and heat insulation purposes. It is specially

recommended for use in air conditioning of buildings
 Glass blocks:

• These consist of two halves so fused together as to form a hollow inside

• They provide insulation against heat, cold and noise and are easy to
clean

Uses: They are widely used for constructing wall partitions

 Soluble glasses:

• It is prepared by melting quartz sand, grinding it and thoroughly mixing

with soda ash, sodium sulphate or potassium carbonate. The melting is
carried out in glass tanks at a temperature between 1300⁰C to 1400⁰C
and it takes about 7-10 hours

• It is soluble in water, under normal conditions

Uses: It is used in the windows of schools, hospitals etc.

 Ultra Violate ray glass:

• It transmits ultra violate rays effectively even though it is not in the

direction of the rays of sun

• It is made from the raw mixture with minimum admixtures of iron, titanium
and chrome

Uses: It is used in the windows of schools, hospitals etc.

 Structural glass:

• This type of glass is available in the form of glass-crete square blocks, tiles
or lenses in thickness varying from 5mm to 30mm

• These glass products are hollow, light and transparent

Uses: Widely used for pavement lights, partitions, lantern lights etc.
USES OF GLASS
• The fibre glass reinforced with plastics can be used in the construction
of furniture, cars, trucks, lampshades, bath room fittings etc.

• Glass is used to form a rifle barrel which is lighter and stronger than
conventional type

• Thousands of items in the body of a guided missile are made of glass

• Glass is used in the construction of noses of deep-diving vehicles

• Optical glass is finding wide application for the development and

advancement of sciences of astronomy and bacteriology

• The glass linings are applied on equipment likely to be affected by

the chemical corrosion such as valves, pipes, pumps etc.
• Hollow glass blocks can be used for the construction of the walls and
ceilings of the modern homes

• Windows with color-changing glass are transparent during the day

which is a source of light at night

These are some of the important uses of glass, based on the recent
developments in the glass industry.
INSULATING MATERIAL
INSULATING MATERIAL : INTRODUCTION
The materials which control transmission of heat and cold and offer
resistance to reflection and transmission of sound and electricity are
known as insulating material.

While designing and constructing public and residential buildings, much

importance needs to be given to heat, sound and electrical insulation.
In order to provide comfortable living, safety, efficiency of work and
auditory of building, it is imperative to provide good thermal, acoustical
and electrical conditions.
• Heat or thermal insulation is provided to control the transmission of heat
or cold as to provide a proper temperature inside the rooms of the
building

• Sound insulation is provided to control the disturbance due to noise and

to remedy the acoustical defects as to achieve the best sound effects.
(Acoustics is a broad field which embraces music radio, sound
reproduction and other fields. It includes those aspects of sound control
associated primarily with man’s normal environment.)

• Electrical insulation is provided to separate the electrical conductors

from other bodies to prevent escape of electricity
INSULATING MATERIAL : CLASSIFICATION
The insulating materials may be classified as follows:

1. Heat insulating materials

2. Sound insulating materials

3. Electrical insulating materials

HEAT INSULATING MATERIALS
 General Aspects

• The function of a heat insulator is to resist the flow of heat through its body

• They grant protection against heat and cold

• The materials are generally porous and their properties depend on the
nature of pores, their distribution, size and whether they are open or
closed. The materials with a great number of fine, closed and air filled
pores are the best heat insulating materials

• Their bulk density is usually below 7000 N/m3 and coefficient of thermal
conductivity does not exceed 0.75 kj.per in hr ⁰C

• The heat insulators should be protected against moisture

 Requirements of a heat insulating materials

The main requirements of a good heat insulating materials are:

• Thermal stability

• Chemical & Physical stability

• Low thermal conductivity

• Low specific gravity

• Odorless

• Resistance to vibration and shock

• Porous and fibrous texture

• Economical in its initial cost

SOUND INSULATING MATERIALS
The materials which offer resistance to reflection and transmission of
sound are called sound insulating materials

These materials can be incorporated in building structures either in

compressed or suspended or free state
 Requirements of sound insulating materials

A good sound insulating material should fulfill the following requirements:

• It should be able to absorb noise to the desired extent

• It should be such that it can be cleaned, washed or painted easily to

maintain a clean appearance

• It should be resistant to attacks of vermin, insects, termite and dry rot

• It should be free resistant

• It should be able to withstand weathering effects

• It should be lighter so that can be handled and fixed easily

• In its finished form, it should offer pleasant appearance

• It should be economical in its initial cost

 Classification & Description of sound insulating materials

The sound insulating/ absorbent materials may be classified as follows:

• Soft materials:

These materials have sufficient porosity and are good absorbers.

Examples: Asbestos, rockwool, glass, silk, hanefelt.

• Semi-Hard Materials:

They are stiff enough to stand rough handling and can also serve as building
panels.

Examples: Mineral wool boards, cane fibres

• Hard Materials:

These are hard materials which have been made porous during
manufacture. They also serve as protective and surfaces.

Examples: Porous tiles or masonry

Some of the common types of sound absorber materials are described below:

 Acoustical plaster:

• It is made from the mineral called the perlite

• It is also called fibrous plaster

• It also possesses as absorbent coefficient of 0.30 at 500 cycles per second

• It is available in different colors and is usually applied in two coats of finished

thickness of about 12 mm. The rough finish of such a surface has slightly better
sound absorption effect compared to a smooth finish

• The acoustic plaster boards are also available which can be fixed on the wall
and in that case co-effiecient of absorption varies from 0.15 to 0.30
 Acoustic pulp:

• It is mainly composed of asbestos and cellulose fibres mixed with certain

binders and preserving chemicals. When water is added, it becomes
plastic and can be applied then to the wall and ceiling surfaces to a
thickness up to 20 mm

• It is applied in layers of 6 mm thickness

• It is easily shaped and finished (being plastic)

 Unifil acoustical plaster:

• It is manufactured from vermiculite, other constituents being gypsum

and lime and portland cement. Water is added to make it plastic for
application

• It is inert, featherweight and a granular substance

Uses: It is adopted to energy type of architectural treatment and is

mainly used for interior finishes.
 Acoustical boards of tiles:

• They are usually made of either compressed cane or wood fibre or

mineral wool

• They are pre-finished at the factory and can be painted or colored to

give desirable decorative appearance and light reflection characteristics

• They have uniform physical and sound absorption characteristics

• They can be made in different sizes and shapes to suit the requirements

• The acoustical tiles are relatively costly than other absorbent materials

• Pre-fabricated boards may be of unperforated or perforated type

Acoustic tiles are the most suitable for rooms in which small area is available
for acoustical treatment
Some of the common types of boards and minerals made of material
other than mineral fibre are:

• Corkoustic

• Celotex building board

• Acousti-lux

• Heraklith

• Econacoustical tiles

• Acousti-celotex

• Muffleto tiles
 Glass Fibres:

• Glass fibres of 0.15 diameter are used for the purpose of sound insulation

• When faced on one or both sides with a non-metallic flexile material such as
paper, muslin, or glass cloth it is known as fibre glass blanket. Such blankets
are extensively used in broadcasting, television and film studios.

• Fibre glass boards and tiles can be manufactured into a lightly decorative
material having uniform texture and excellent light properties
 Quilts & Mats:

• These are prepared from glass wool or mineral wool and are fixed in
the form of acoustic blankets

• Their absorption coefficients depend on the density, thickness,

perforation, and nature of backing, frequency of sound and mode of
fixing
Thank You