Raw Materials

Date: 2015-10-07; view: 505.

Natural clay minerals, including kaolin and shale, make up the main body of brick. Small amounts of manganese, barium, and other additives are blended with the clay to produce different shades, and barium carbonate is used to improve brick's chemical resistance to the elements. Many other additives have been used in brick, including byproducts from papermaking, ammonium compounds, wetting agents, flocculents(which cause particles to form loose clusters) and deflocculents (which disperse such clusters). Some clays require the addition of sand or grog (pre-ground, pre-fired material such as scrap brick).

A wide variety of coating materials and methods are used to produce brick of a certain color or surface texture. To create a typical coating, sand (the main component) is mechanically mixed with some type of colorant.

Before the brick is fired, it must be dried to remove excess moisture.

After forming and coating, the bricks are dried using either tunnel dryers or automatic chamber dryers. Next, bricks are loaded onto cars automatically and moved into large furnaces called tunnel kilns. Firing hardens and strengthens the brick. After cooling, the bricks are set and packaged.

Exercise 4. Put 10 questions to the text.