A brick is a small, popular building material composed of fired clay and various additives. Bricks have been used for buildings for more than 5,000 years and were used by the Babylonians, Egyptians and Dutch until spreading worldwide in the 1800s. Depending on the type and color of brick, there will be slightly different materials, but it is almost always created from a clay base with minerals and other additives.
Kaolin is one of the main natural clay minerals that are used for the body of brick. Kaolin is a geological term that refers to a white clay rock that can be found in deposits throughout the world. Kaolin is used in the paper industry, the plastic industry, in ceramic and in pharmaceuticals. Kaolin has an extremely high melting point and when used in brick creation, it is fired between 1,000 and 1,200 degrees Centigrade.
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Shale is the other main material used in the body of brick. Shale is a sedimentary rock that makes up around 55 percent of all the sedimentary rocks on the planet. Shale is formed when mud or clay consolidates. This sedimentary rock is used in the cement industry, the coal industry and the brick industry. When bricks are created, the shale and kaolin are ground up in special equipment, organized, formed, coated, dried, fired and then cooled before becoming the bricks you know today.
Several minerals are incorporated into the brick process to improve the brick creation process. The minerals added are often those found in the clay itself, which include sodium, potassium and calcium. When these minerals melt, they form a silicate liquid, which will allow the bricks to be altered more quickly. They also leave a glassy coat to the brick and contribute to the hardening process.
There are many other potential additives to bricks, depending on the kind of brick that is being created. Flocculents are compounds that cause loose clusters in bricks, whereas deflocculents disperse loose clusters. Sand or grog (pre-ground and fired scrap material) is added to clays to improve the strength of the brick. Barium carbonate is a chemical compound added to improve how brick reacts to chemicals. Sand can be used that has been mixed with a colorant or a flux or frit can be used, which is a glass containing colorant, to create certain colors of bricks. These materials reduce the melting temperature of the brick and stick to the brick's surface. New brick techniques will continue to be created, including a new brick created from fly ash, which is a by-product of power plants that use coal.