Bricks

Definition: A brick is an artificial kind of stone made of clay whose chief characteristics are a plasticity when wet and stone like hardness after being heated to hight temperature.

Factors that Affect the Quality if Bricks: The following are the factors on which the quality of bricks depends:

                         1. Chemical properties of the clay used.                                                                                                                     2. Preparation of the clay.          
                         3.Different degrees of building.

Constituents of Bricks Clay and their Functions:  A good brick-clay should be  such a  miture of pure clay and sand that when prepared with water, it can easily be moulded and dried without cracking or warping. It should also contain alumina, (alumina oxide) lime, iron oxide magnesia (magnesium oxide). Chemical analysis of a good brick-clay should give the following chemical.

                    Silica                                                                      55%       

                   Alumina                                                                 30%       

                   Iron oxide                                                                8%       
                   Lime                                                                         1%       

                   Magnesia                                                                5%       

                   Organic matters                                                     1%        

                                                                                                 

                   Total                                                          =           100%

Silica: Silica exists in all clays in a state of chemical combination with alumina forming silicate of alumina and sometimes exists in a free state when it is called flint or sand. The presence of sand prevents cracking, shrinking, and warping. The higher the proportion of sand, the more shapely and uniform in texture shall be the brick. But too much of sand makes the brick brittle and weak. 

Alumina (Aluminum oxide): The principal constituent of brick clay. It imparts plasticity to clay which is very essential for the purpose of moulding. It also imparts density. But the clay containing too much alumina should not be used decase bricks will crack and warp burning brying and becomes very hard under the influence of heat.

Iron Oxide: The presence of iron in clay enhances the impermeable and durable qualities. Iron and limes in small quantities give creamy colour to bricks. The colour of bricks is very much dependent upon the conents of iron and the colour ranges from lights yellow to range and red.

Magnesia (Magnesium Oxide): Presence of magnesia in small quantity decseases shrinkage and gives yellow tint.

 Lime: It reduces shrinkage of bricks during drying and enable the silica to melt in burning and thus binds the particles of brick together. In excess, however, it will cause the brick to fuse too readily and the shape will be lost. Lime should be present in a very finely divide state. Because, if present in the form of lumps it is very injurious to bricks, because on burning it becomes quick lime and absorbs moisture causing disintegration. 

Organic Matters: A small quantity of organic matter will assist burning bricks, Excess in bad, because if it is no completely burnt, the bricks will be porous. Small quantity of alkalies will lower the fusion point of clay.