Why does clay turn into hard bricks when burned?

Clay because it contains light green reducing state of iron salts and black humus so show gray-black, when the gray-black brick billet into the fire after calcination, it can become bright red brick.

Black mud brick billet in the calcination, the occurrence of two chemical changes, humus are organic, at high temperatures and oxidation into carbon dioxide and other substances, the black color will disappear, the mud in the reduced state of iron salts are also gradually oxidized, into trioxide di-ferric iron, it becomes a red brick.

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Note:

1, red brick building can cause great harm to the human body. Some experts have learned through testing that the use of red bricks to build houses for long-term residence will produce harmful chemicals to the human body, long-term residence in such an environment will make people suffer from disease.

2, the production process of red brick will have an impact on the air, the environment. The burning process of red bricks will produce a large amount of dust and carbon dioxide, which will increase the chances of neighboring residents suffering from tuberculosis and lung cancer, and also cause irreversible damage to the local air environment.

3, red brick production of raw materials for the red sand, a large number of mining will be on the local arable land, soil, riverbed and other hazards, increasing the chance of natural disasters.

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