bricks
TRANSCRIPT
BRICKS
INTRODUCTION
Bricks may be defined as artificial material obtained by moulding clay in rectangular blocks of uniform size, which are finally dried and burnt at high temperature to form a dense and compact product.
Bricks are chiefly employed in building construction and architectural compositions.
Easy availability, light weight, comparative cheapness, ease in handling, flexibility of moulding into required shape and size and ease in working are the main characteristics of bricks.
Clay bricks, when properly manufactured, are nearly as good as stones.
COMPOSITION OF EARTH :
1 . Alumina: It is the chief constituent of every kind of clay. A good brick earth should contain about 20% to 30% of alumina. This constituent imparts plasticity to the earth so that it can be moulded.
2. Silica: It exists in clay either as free or combined. As free sand, it is mechanically mixed with clay and in combined form, it exists in chemical composition with alumina. A good brick earth should contain about 50% to 60% of silica. The presence of this constituent prevents cracking, shrinking and warping of raw bricks. It thus imparts uniform shape to the bricks.
2. Lime: A small quantity of lime not exceeding 5 % is desirable in good brick earth. It should be present in a very finely powered state because even small particles of the size of a pin head cause flaking on the bricks. The lime prevents shrinkage of raw bricks.
4. Oxide of iron: A small quantity of oxide of iron to the extent of about 5 to 6 [percent is desirable in good brick earth. It helps as lime to duse sand. It also imparts red color to the bricks. The excess of oxide of iron makes the bricks dark blue or blackish. If, on the other hand, the quantity of iron oxide is comparatively lee, the bricks will be yellowish in color.
5. Magnesia: A small quantity of magnesia in brick earth imparts yellow tint to the bricks and decreases shrinkage. But excess of magnesia leads to the decay of bricks.
MANUFACTURING PROCESS :
The fundamentals of brick manufacturing have not changed over time.
However, technological advancements have made contemporary brick plants substantially more efficient and have improved the overall quality of the products.
A more complete knowledge of raw materials and their properties, better control of firing, improved kiln designs and more advanced mechanization have all contributed to advancing the brick industry.
PREPARATION OF RAW MATERIAL:
Manufacturing process of bricks begins with collecting surface clays and shale from the quarry.
In the preparation for crushing, raw materials are transported to storage.
The crusher breaks up the large pieces of clay passes it to conveyers heading for the grinders.
The materials are crushed by the grinders to a fine consistency.
The crushed material passes over a vibrating screen, in which the fine material will be passes through to the next step and the coarse material is returned to the grinder.
Till this the material will be kept dry. Soon after screened, the materials will be sent to the pug mill, where it will be tempered to for shaping in the required brick form.
The pug mill consists of a chamber that has one or two revolving shafts with attachment of blades rigidly, which mixes the material thoroughly, water is added provide proper plasticity and manganese are added to change the body color.
MAKING PROCESS
The next step in manufacturing process of bricks is to make the material into shape of brick. Handmade, machine molded or extruded are used to shape the material.
In Handmade method, a soft mixture is passed through the extruder; it is cut into slugs and conveyed to work stations.
Then the slugs are picked up, rolled in sand and thrown into a pre sanded wooden mold.
In machine molded, bricks are made from clay material is mixed with water and positioned in the machine that squashes the wet mix into molds.
Then the mold box is bumped and dumped.
The variety of sands is used to keep brick from sticking in the molds.
SETTING AND DRYING Once the brick is formed using the above mentioned method, the unit is sent into Kiln cars. Before sending into kiln the unfired or green brick should be dried. The drying process is done by keeping the green brick in enclosed dryers.
hand setting on kiln cars robotic setting on kiln cars dry, green brick emerges from dryer (to right is fired brick)
FIRING AND PACKING The continuous tunnel kiln involves the combination of vertical and horizontal drafts. The preheating, cooling, and burning is done in the zone where the temperature varies up to 2000 degree. When the green brick enters the kiln, the manufacturer will determine the type of firing required for producing the color. After coming out of Kiln, the brick is allowed to cool before handling.
Inside tunnel kiln Packaged cube of brickBrick inside kiln
CLASSIFICATION OF BRICKS
First class bricks:These bricks are table-moulded and of standard shape and they are burnt in kilns. The surfaces and edges of the bricks are sharp, square, smooth and straight. These bricks are used for superior work of permanent nature.
Second class bricks: These bricks are ground-moulded and they are burnt in kilns. The surface of these bricks is somewhat rough and shape is also slightly irregular. 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
Third class bricks:These bricks are ground-moulded and they are in clamps. These bricks re not hard and they have rough surfaces with irregular and distorted edges. These bricks give dull sound when struck together. They are used for unimportant and temporary structures and at places where rainfall is not heavy.
Fourth class bricks:These are over burnt with irregular shape and dark color. These bricks are used as aggregate for concrete in foundations, floors, roads, etc. Because of the fact that the over burnt bricks have a compact structure and hence they are sometimes found to be stronger that even the first class bricks.
PROPERTIES OF GOOD BRICKS 1. Color: The color of good brick should be uniform. It may deep red, cherry
or copper colored.
2. Shape: Bricks should be uniform in shape with sharp straight right angled edges.
3. Size: Size of the bricks should be standard as prescribed by Indian standards. [19cm x 9cm x 9cm]
4. Soundness: A good brick should give metallic ringing sound when struck with another brick.‘
5. Hardness: A good brick should be sufficiently hard which can be tested by a finger nail. No mark should be left on the surface of the brick when scratched with thumb-nail.
6. Crushing strength: The crushing strength of a brick should not be less than 3.5N/mm2
7. Water absorption: First class brick should not absorb water more than 20% of its dry weight when soaked in water for 24hrs.
8. Structure: A good brick should show fine, compact and uniform structure in broken form.
9. Thermal conductivity & Fire resistance: It should have thermal conductivity. A good brick should have adequate fire resistance. Ordinary brick can resist temperature up to 12000C
10. Strength: Bricks should not break when dripped on hard ground from a height of about 1m.
11. Durability: A good brick should be able to resist the effects of weathering agencies like temperature, rain, etc.
FEW TYPES
Plinth Brick
Perforated Bricks
Hollow Bricks
Fire Bricks
Cornice Bricks
Coping Bricks
Bullnosed Brick
USES OF BRICKS Bricks are used for building and pavement.
Bricks in the metallurgy and glass industries for lining furnaces,
Bricks are used where strength, low water porosity or acid (flu gas) resistance are needed.
