Bricks in Details

Brick is a block or a single unit of a ceramic material used in masonry construction with a size that can be held in one hand conveniently. They have been regarded as one of the longest lasting and strongest building materials used throughout history. The brick might be made from dried earth (clay), lime-and-sand, concrete, or shaped stone. 

According to various material used in manufacture bricks are classified as:

1. Common Burnt Clay Bricks
2. Sand Lime Bricks (Calcium Silicate Bricks)
3. Concrete Bricks
4. Fly ash Clay Bricks
5. Fire Clay Bricks

Common Burnt Clay Bricks

Clay bricks are fired bricks. These are formed by pressing in molds or by an extrusion and wire cutting process. Then these bricks are dried and fired in a kiln. 

Sand Lime Bricks (Calcium Silicate Bricks)

These bricks are mixtures of sand and hydrated lime pressed in molds and cured in a high-pressure steam autoclave.

Concrete Bricks

Concrete bricks are mixtures of cement, sand and aggregates vibrated in molds and steam cured.

Fly ash Clay Bricks

Fly ash is used along with clay in these bricks. Fly ash is obtained from boilers of thermal power stations. 

Fire Clay Bricks

Fire clay exists at much depth below the surface and is usually mined. Generally, Fire clays contain metallic oxides less than surface clays and have more uniform chemical and physical properties.  

Uses of Bricks:

Bricks are used for building, block paving and pavement.

Bricks are used where strength, low water porosity or acid (flue gas) resistance are needed.

Bricks in the metallurgy and glass industries are often used for lining furnaces

Classification According to Quality:

First Class Bricks  Second Class Bricks Third Class Bricks      Specification of First Class Bricks Made of good earth which is free from saline deposits and are sand molded. Burnt thoroughly without being vitrified and have deep red, cherry and copper color.  Regular and uniform in shape and size with sharp and square edges and parallel faces.   Must be homogeneous in texture and emit a clear ringing sound on being struck together. Free from flaws, cracks, chops, stones and lime.  Should not absorb water more than 20% of its own dry weight after 24 hours, immersion in cold water.  Have a minimum crushing strength of 105 kg per sq. cm when tested according to the test. Should not show appreciable sign of efflorescence either in dry state or subsequent to soaking in water.                                                      First Class Brick should be used for construction works.    Specification of Second Class Bricks They shall be well burnt or slightly over burnt. They must give clear ringing sound when struck. The may have slight irregularities in size, shape and color. They may have slight chips, flaws or surface crack but must be free from lime or kankar. The minimum crushing strength of second class brick should be 70 kg per sq cm.     Specification of Third Class Bricks These bricks are slightly under burnt or over burnt. They are not uniform in shape, size and edges. They shall not observe water more than 25% of their own dry weight after 24 hours, immersion in cold water. They have some signs of efflorescence.      Visual Characteristics:

·                    Good bricks should be burnt thoroughly so that they become hard and durable.

·                     Satisfactory burning of the bricks is ascertained by hard ringing sound when two bricks are                   struck together. 

·                     The bricks should have smooth and rectangular shapes with sharp corners and uniform colors. 

·                     The bricks should be free from cracks, chips, warp age, large particles of lime and organic matters.