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Clay was used as a mortar in brick chimneys and stone walls where protected from water. Clay, relatively impermeable to water, is also used where natural seals are needed, such as in pond linings, the cores of dams, or as a barrier in landfills against toxic seepage (lining the landfill, preferably in combination with geotextiles). [35]
Clay minerals are hydrous aluminium phyllosilicates (e.g. kaolin, Al 2 Si 2 O 5 4), sometimes with variable amounts of iron, magnesium, alkali metals, alkaline earths, and other cations found on or near some planetary surfaces. Clay minerals form in the presence of water [1] and have been important to life, and many theories of abiogenesis ...
The first recorded use of medicinal clay is on Mesopotamian clay tablets around 2500 BC. Also, ancient Egyptians used clay. The Pharaohs’ physicians used the material as anti-inflammatory agents and antiseptics. It was used as a preservative for making mummies and is also reported that Cleopatra used clays to preserve her complexion. [1] [2]
In the Ancient Near East, clay tablets (Akkadian ṭuppu(m) 𒁾) [1] were used as a writing medium, especially for writing in cuneiform, throughout the Bronze Age and well into the Iron Age. Cuneiform characters were imprinted on a wet clay tablet with a stylus often made of reed . Once written upon, many tablets were dried in the sun or air ...
Stoneware clay is often accompanied by impurities such as iron or carbon, giving it a "dirty" look, and its plasticity can vary widely. [14] Non-refractory fire clay may be another key raw material. Fire clays are generally considered refractory, because they withstand very high temperatures before melting or crumbling.
Other uses include as an anticaking agent in animal feed, in papermaking to minimize deposit formation, and as a retention and drainage aid component. Montmorillonite has also been used in cosmetics. [8] Sodium montmorillonite is also used as the base of some cat litter products, due to its adsorbent and clumping properties. [citation needed]
The heating process causes gases trapped in the clay to expand, forming thousands of small bubbles and giving the material a porous structure. LECA has an approximately round or oblong shape due to circular movement in the kiln and is available in different sizes and densities. LECA is used to make lightweight concrete products and other uses.
The selection of material was based on local conditions and the function of the object being manufactured. Nile clay was principally used for household crockery and containers, as well as ceramics for ritual use. Marl clay was principally used for storage and prestige objects like figural vessels. [8]