Bricks - Basic

Introduction

Bricks are obtained from molding of clay in regular shape and uniform in size by burning and drying. Bricks are uniform in size so that they can be arrange in required form easily without any special care. No need of special lifting equipment is there. Hence it is useful where stones are not available and clay is available in ample. Bricks are also light weight then stone and easy to handle.

Comparison between brickwork and stonework

Brickwork superior to stonework in the following respect.

• Place where plenty of clay available and stones are not easily available brickwork become more economic than stonework.
• Overall cost of construction for brickwork is lesser than stonework as less skilled labours are used.
• Bricks can handle without special equipment, so that it can be easily moved by labour manually.
• Bricks are more fire resistant than stones, they do not disintegrate easily.
• More better weather resistance than stones.
• Mortar joints thin and durable. Due to thin joints mortar consumption and wastage is less.
• Opening and connection can be easily established than stonework.

Stonework superior to brickwork in the following respect.

• Stonework more watertight than brickwork, as bricks absorb more moisture from atmosphere it will leads to dampness.
• Stonework produce more solid structure than brickwork, for monumental and public building stonework is more useful instead of brickwork.
• Stonework is more stronger than brickwork.
• Better architectural effects developed by stonework.
• If at a place stones are available nearby it will prefer over brickwork.

Composition of good brick

Easy to remember :- SALIM

1. Silica

It is main constituent in brick making earth/clay. Silica present either free or combined form in clay. Free silica mixed with clay and combined silica chemically available in alumina. Amount of silica for a good brick earth is 50 to 60 %. 

Silica provide shape, prevent cracking, shrinkage and warping of brick during manufacturing process. Durability of bricks depends upon amount of silica in brick earth. 

Excess of silica looses brick's shape and make it brittle.

2. Alumina

Alumina is main constituent for all kind of clay. For a good brick earth amount of alumina ranges between 20 to 30 %. 

Alumina imparts plasticity to the brick.

Excess of alumina makes brick shrink and warp during burning. 

3. Lime

A small quantity of lime is desirable in brick making earth. It should be in powdered form. Lime makes silica fusible at lower temperature and prevent from shrinkage. 

Excess of lime make the brick to melt while burning. Lime should be free from lumps, if lumps are present it will burn and converted into quick lime after burning and expands in presence of moisture, which causes the brick to split into pieces.

4. Iron

Iron imparts color to the bricks. Iron of 5 to 6 % is desirable in good brick earth. Iron is midway for lime to fuse sand.

Excess of iron oxides make the bricks dark in color. Less amount of iron oxide make the brick yellowish in color.

5. Magnesia

Magnesia in small amount makes brick plastic and reduce shrinkage.

Excess of magnesia makes decay of bricks.

Constituents	Amount
Silica(SiO2)	50 – 60
Alumina(Al2O3)	20 – 30
Lime(CaO)	2 – 5
Iron Oxide(Fe2O3)	< 7
Magnesia(MgO)	< 1

Undesirable ingredient for a good brick earth

1. Lime
2. Iron pyrite
3. Alkalies
4. Pebbles
5. Organic matter

1. Lime

Lime lumps causes disintegration of brick as discussed above.

2. Iron Pyrites

Presence of iron pyrite makes the brick crystalline and disintegrated during burning.

3. Alkalies

Alkalies present in the form of soda and potash. It acts as a flux in kiln burning. It causes the brick to shrink and warp and looses its shape. After all this some amount of alkalies still present in the brick which will absorb moisture from atmosphere and leaves gray sheds upon drying and spoiled whole wall aesthetic view.

4. Pebbles

Pebbles present in the brick causes immature and undesirable failure of bricks. It should not be allowed in the brick making earth.

5. Organic matter

Organic matters in earth helps in burning of bricks at earlier stage, but when this matter is not completely at former stage, later it will cause to brick become porous. Porous bricks fails early and not satisfying its durability.

"To Be Continued..."