Fire brick

Building material

A fire brick, firebrick, fireclay brick, or refractory brick is a block of ceramic material used in lining furnaces, kilns, fireboxes, and fireplaces. Made of primarily oxide materials like silica and alumina in varying ratios, these insulating materials are able to withstand extremely high temperatures, and have a low thermal conductivity for greater energy efficiency. Refractory bricks generally range from 25-45% alumina, and ~60% silica, with additional magnesium, calcium, potassium oxides.

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