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Q1.Define stones. What are the requirements of good building stones?
Ans:-
A hard substance that comes from the
ground and is used for building, carving,
etc. is known as stone.
:
a small piece of rock
:
a piece of rock used for a particular
purpose
Requirements of Good Stone
The essential requirements of building stones
used for structural work are given below:
Strength
Ordinarily, the strength of a stone is not of
primary importance, as very often the loads to
which it is subjected in a structure are much
below its permissible crushing strength
Durability
Stones should possess a natural durability to
withstand the destructive effects of various agents continuously operating on them. In fact,
the life of a structure depends upon the
durability of the materials with which it is built.
The durability of a stone depends upon the
relation between its chemical composition and
that of the atmospheric surroundings. The
texture of the stone also influences its durability.
Crystalline homogeneous and close-grained
varieties of stones with a dense structure should
be selected for good works. The surface of a freshly broken stone should be uniform in
texture, colour and hardness. Porous stones or
those containing patches of soft or objectionable
materials are liable to disintegrate quickly.
Cost
An important consideration in the selection of
building stone is its cost. Other things being
equal, the cost of a stone depends upon the
ease with which it can be quarried out, the
proximity of the quarry to the place of use, and
the transportation facilities available. The
subsequent cost of dressing a stone, before it is
placed directly in the structure, should also be
low.
Appearance
In the case of the stone used for face work,
where appearance is a primary factor, its colour
and ability to receive polish is an important
factor.
Hardness
The stone used in floors, pavements and aprons
of bridges, should be able to resist the abrasive
forces caused due to wear and friction. Hardness
of stones can be tested by the Mohr’s scale of
hardness in the laboratory and in the field by
scraping the surface with a sharp knife. A hard
stone will not show any scratches.
Fig: Building stones
Toughness
Building stones should also be tough enough to
withstand stresses developed due to vibrations of
machinery and moving loads over them. The
stones used in the construction of roads should
be hard as well as tough.
Specific Gravity and Weight
The stones used for the construction of dams,
weirs, barrages, docks and harbours should be of
a heavier variety. In case of dams and roof
coverings, lighter varieties of stones are
preferred. The specific gravity of good building
stones should be between 2.4 and 2.8.
Porosity and Absorption
A good stone should not be porous, rain water,
enter the pores which is generally acidic,
Chemical Composition of Stone Limestone and
weak sandstone are relatively less durable than a
good sandstone, granite or gneiss. Air and water,
containing carbon dioxide, seriously affect
limestone. Iron pyrites also tend to disintegrate
stones; excess iron oxide or carbonate in stones
develops rust in the presence of moisture;
presence of clay affects the efficiency of the
cementing materials; soda and potash also have
a disintegrating effect; all varieties of mica are
soft and are readily decomposed by exposure to
atmosphere. Stones with silicates as the
cementing material will weather better than
those with calcareous or ferruginous binding
material.
Q.2:- Explain the classification of bricks?
Ans:-
Brick is small rectangular block typically made of
fired or sun-dried clay, used in building.
Classification of Bricks
The classification of bricks is as follows:
(i) unburnt or sun-dried bricks; and
(ii) burnt bricks.
The unburnt or sun-dried bricks are
those bricks which are dried with the
help of heat that is received from sun
after the process of moulding. The
unburnt bricks can only be used in the
construction of simple temporary and
cheap structures. Unburnt bricks should
not be used at places exposed to heavy
rains.
The bricks used in construction works
are burnt bricks and they are classified
into the following four categories:
(1) First class bricks
(2) Second class bricks
(3) Third class bricks
(4) Fourth class bricks.
(1) First class bricks:
These first class bricks are table moulded
and of uniform shape and they are
burnt in kilns. The surfaces and edges of
the bricks are sharp, square, smooth and
straight. They comply with all the
qualities of good bricks. These bricks are
used for important work of permanent
nature.
(2) Second class bricks:
The second class bricks are ground
moulded and they are burnt in kilns. The
surface of the second class bricks is
slightly rough and shape is also slightly
regular. These bricks may have hair
cracks and their edges may not be sharp
and uniform. These bricks are commonly
used at places where brickwork is to be
provided with a coat of plaster.
(3) Third class bricks:
These bricks are ground-moulded and
they are burnt in clamps. These bricks
are not very hard and they have rough
surfaces with irregular and blunt edges.
These bricks give dull sound when they
are struck together. They are used for
unimportant works, temporary
structures and at places where rainfall is
not heavy.
(4) Fourth class bricks:
These are overburnt bricks with
irregular shape and dark colour. These
bricks are used as aggregate for concrete
in foundations , brick floors , surkhi,
roads, etc. because of the fact that the
overburnt bricks have a compact
structure and hence they are sometimes
found to be stronger than even the first
class bricks. It is thus seen that the above
classification of bricks is based on the of
manufacturing or preparing bricks.
Q3:-Explain the process of manufacturing of bricks?
Ans:-
PRIMARY STEPS OF
BRICK MANUFACTURING
PROCESS
STEPS INVOLVED IN BRICK
MANUFACTURIN
Manufacturing of bricks consists of the
following 4 operations or steps.
1. Preparation of brick clay or brick earth
2. Moulding of bricks
3. Air drying of bricks
4. Burning of bricks
The process of brick making
1. PREPARATION OF BRICK
CLAY OR BRICK EARTH
In this step the soil is excavated in steps and
then laid on leveled ground. Then the soil is
cleaned of impurities such as vegetation
matter, stones or pebbles etc. After removing
impurities it is exposed to weather for few
months. This is called the process of
weathering. After completion of weathering
process the soil is blended with other material
to prepare good brick earth. Then the mixed
soil is tempered by being thoroughly broken up,
watered and kneaded. The tempering is usually
done in pug mill.