House protects us from cold, heat, rain and enemies. A house is constructed with different materials, just as our body is
made of different organs. Every organ in our body does a specific function. Similarly different workers perform different
works that are necessary for the construction of a house. For construction a house we need a proper plot of land. We require
stones brick, cement, sand and other materials. Stones are used for the foundation and bricks for walls. For the roof we
require tiles or sheets. Iron is required if we put a concrete roof. To construct a house properly, we must have a knowledge
about the materials that are used. Then the construction becomes easy.

How the bricks are prepared:
Brick is the structural unit for the construction of walls. In villages people construct the walls with mud. The mud walls
are not strong. In the rainy season, the mud on the mud walls get washed away and the houses collapse. Houses, with brick
walls can with stand the effects of water. They are much stronger and last for a longer time. Bricks are prepared from clay.
Clay is mixed with water and made into paste. This paste of clay is put into rectangular wooden moulds and spread on an even
surface. The wet bricks are dried in the sun. The dried bricks are arranged one above the other in several rows. For the
passage of air, space is left between the rows of bricks. These spaces are filled with wood, charcoal or husk. The entire
block of bricks is covered with a layer of clay. This is called a "Brick kiln". The fuel in the spaces between the rows of
bricks is lighted and allowed to burn for a few days. This is called "Baking". Due to the heat, the moisture in the bricks
evaporates. Baking makes bricks strong and resistant to water. For testing the strength of a brick, keep the brick in water
for more than 3 hours. Then take it out from water and drop it on to the ground. If it does not break into pieces, it is a
good brick.

How the tiles are prepared:

Clay soil dried up ponds or tanks is used for making tiles. This soil is made wet with water and is ground in a grinder. Then
it is put into a machine. The machine moulds the soil paste into required shapes and sizes of tiles. These tiles are pressed
and then dried. The dried tiles are baked in a kiln.

How the Mortar is prepared:

Lime stone occurs in nature. It is heated in kilns. The water and carbon dioxide in limestone come out of it. It is called
dry lime. The dry lime, sand and water are mixed in proper proportions and are ground in a mortar. Then it becomes a paste
and is called mortar. Mortar is used to join the bricks in the construction of walls and for plastering them. Mortar hardens
when exposed to air.

How Cement is prepared:
Cement is a fine powder. It is very heavy and dirty greenish in colour. When cement comes into contact with water, it becomes
a very hard mass. This hard mass looks like Portland rock. So cement is called "Portland cement".
Lime stone and clay are the raw materials for the preparation of cement. The limestone and clay are separately made into a
powder in a machine. Then five measures of lime powder is mixed with one measure of clay powder. This mixture is ground into
a fine powder. The grinding of lime and clay is called "Pulverisation". The pulverised mixture of lime and clay is put in a
kiln and heated to a temperature of 1800 Degrees c. Due to the chemical reaction between the lime and clay, hard grey balls
of calcium silicates and calcium aluminates are formed. This is called "Clinker". The clinker is cooled. It is mixed with 2 to
3 % of gypsum and then finely powdered. The powdered clinker is called cement. Cement must be packed in polythene bags and
stored in dry conditions away from moisture. If it is allowed to come into contact with air or water, it hardens. Just before
use cement is mixed with sand and water. Cement is used in the construction of building, bridges and dams. In all these
construction, cement is used for joining layers of bricks or stones and to plaster the walls and other structures.

Preparation of Concrete:
Concrete is a mixture of cement, sand, small stones and water. These are thoroughly mixed by hand or in mixing machines and
used for construction. Concrete hardens very quickly and is much more stronger than cement or mortar. Concrete is used in the
construction of building, bridges and dams. It is also used in laying of roads. To give more strength, concrete is spread
over iron frame and this is called reinforced concrete. Reinforced concrete is much stronger than concrete.