If brick had been discovered today, it would undoubtedly have been the sensation of the century.
Clay is formed by the grinding and disintegration of rock. In a dry state, clay can be described as Al2O3 x 2SiO2 x 2H2O, which means a high content of silicon dioxide. By adding water, clay becomes workable. The process is reversible.
Clay can be formed and fired up to 1000 °C. All water is then evaporated so the formula becomes Al2O3 x 2SiO2, and this change is irreversible. Water cannot be reintroduced into the clay. It has become a ceramic material, with areas of use that have been the same for thousands of years, in construction, on floors and roofs, as water pipes and tanks. When the temperature in specially built kilns is increased even more, the clay begins to expand, turning into expanded clay pellets, which in recent years have become an important insulation material and a light weight aggregate in concrete. If expanded clay is poured into moulds and heated to an even higher temperature, it melts and becomes a highly insulating building block called Zytan.
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