Clay, properties, types and varieties, origin, extraction and use

Clay, properties, types and varieties, origin, extraction and use.



Clay is a sedimentary rock with fine grained and complex structure. Plasticity, viscosity, fire resistance and other properties of clay are determined by what ponadobytsya substance is the main.



Characteristics and properties of clay. “Fat” and “skinny” clay. Color. At the same time. Plasticity. Refractoriness. Sintering behavior

The types and varieties of clay

The origin of the clay

Clay mining. Methods of quarrying

The application and use of clay. Advantages



Clay is a sedimentary rock with fine grained and complex structure. Plasticity, viscosity, fire resistance and other properties of clay are determined by what ponadobytsya substance is the main.

It can be such clay materialsas kaolinite (Al2O3·2SiO2·2H2O), andalusite, kyanite and sillimanite (Al2O3·SiO2), montmorillonite (MgO·Al2O3·3SiO2·1. 5H2O), a halloysite, it (Al2O3·SiO2·H2O), hydrargillite (Al2O3·3H2O), Diaspora (Al2O3·H2O), corundum (Al2O3), monotrema (0,2[K2MgCa]O·Al2O3·2SiO2·1. 5H2O), Muscovite (K2O·Al2O3·6SiO2·2H2O), the renting (Al2O3·SiO2·2H2O) and pyrophyllite (Al2O3·4SiO2·H2O).

For example, montmorillonite, which refers to layered silicates, has a sorption properties and a pronounced ability to strong swelling.

Different types of clay can contain different proportions of particles of kaolinite, andalusite, Muscovite, hydrargillite, renting, corundum, pyrophyllite and other components of the minerals.

Among the impurities most commonly found particles of quartz, gypsum, calcium, dolomite, pyrite, siderite, magnetite, glauconite.


Characteristics and properties of clay:

The characteristics of clay materials depend on their composition, grain size, humidity of the material, the place of production. In the evaluation of the properties of clay is applied a range of characteristics of density and solubility in water up to porosity and thermal conductivity.

The basic properties of clay:

– when released into water it gets soaked and disintegrates into individual particles, forming a suspension or forms a mass similar to dough;

– in the dry state it has the structure of dust in the wet becomes soft, pliable, easily takes any shape;

after drying or firing, it becomes strong and durable. Dries, it is slightly reduced in volume due to natural shrinkage;

in moist condition it has good binding abilities. Because of these qualities it is used in the manufacture of brick, some types of dishes;

– clay in the wet state, has good hiding qualities, so early it is often used for coating wood-burning stoves, walls of houses and outbuildings;

– this material is able to absorb substances dissolved in liquids. Sorption properties can be used for filtration and purification from impurities of vegetable fats, petroleum products.

Technology of processing clay, change its structure or “fat” allow you to obtain a raw material with desired properties – the right tone with more resistance, less shrinkage, etc.


“Fat” and “skinny” of clay:

A change in the proportions of the main components and impurities do clay “skinny” or “fat”. This property depends on the plasticity of the material, the quality of the final product.

Products too “fat” clay spoil at the stage of drying or kiln, covered with cracks or warp. A emaciated use of additives can reduce the shrinkage of the material in the natural drying or heat treatment. As such an additive, most commonly used sand: small, medium or large dispersion. It is washed thoroughly to rid of dust, because it reduces the viscosity of the clay mass.

“Skinny” clay has low plasticity and are unsuitable for modeling or molding. To improve plastic properties of the technology of otmuchivanie. This enrichment of the material by separating the clay particles from impurities. After dilution of the feedstock with water slowly settling clay particles filtered from the heavier sand, stones.


The colors of clay:

The color of the rock can be yellow, brown, blue, green, black. The color depends on the concentration of chromophores, unsaturated atoms. Compounds of cobalt give the material a blue cast, chrome makes it olive, impurities of magnesium and Nickel brown and gray. After firing, the clay becomes red or white.


Water resistance of clay:

After the material absorbs enough moisture, it ceases to pass through the water. This property allows you to make clay vessels and containers.


Plasticity of the clay:

Plastic material properties are determined by its ability to make desired shape. They depend on the volume of water required to produce a well-formed mass. Among the natural materials clay is one of the first places on plasticity – it can easily take on any form and retains it for a long time. The products from material with low plasticity fast crack, covered with cracks.


Fire resistance of clay:

The ability to withstand high temperatures without loss of strength of clay materials are:

– fusible. Their processing is done at a temperature of 1350 °C. They are used in the production of bricks, tiles, decorative elements of walls;

– refractory. The minimum number of impurities in the composition makes it possible to process at a higher temperature — up to +1580 °C. They are used in the manufacture of facing building materials, sewer pipes;

– refractory. Materials in this group contain almost no impurities in its composition, therefore, their melting temperature above 1580 °C. they are used mainly in the production of refractory bricks for lining furnaces, masonry fireplaces, chimneys.


Sintering behavior of clay:

This property is defined as the ability of a plastic material with high-temperature roasting to go in hard, solid state. Clay after firing, should not be soaked in water. This property sold because of irreversible changes of material structure, namely the removal of physically bound water, decomposition of the clay material on silicon oxide and aluminium oxide. At a temperature of +1000 °C +1200 °C formed a new water-resistant mineral compounds. The melt low-melting constituents when cooled hardens, making the mass hard and durable.


The types and varieties of clay:

In industry, construction, cosmetology used clay of different composition, characteristics, color. Material separation into types is determined by a combination of properties such as plasticity, sintering behavior, resistance, amount of impurities. The most common are:

kaolin (white) clay. White clay used in the manufacture of porcelain and earthenware;

blue clay. In demand in cosmetology and medicine;

bentonite clay. In the manufacture of an aqueous solution it increases in volume several times. This property makes it indispensable in the construction of pile foundations, drilling wells;

fireclay. Used in the manufacture of refractory bricks;

shale. Clay shale for making cement;

pottery (lump) of clay. Ball clay for making pottery;

montmorillonite (smectite) clay. It is used to clean products such as molasses, beer, wine, syrups, juices, oils, petroleum products, and is also used as improving additive in the manufacture of soap.


The origin of clay:

Clay is a product of natural origin, formed from feldspar and igneous rock which in dry state has a fine structure. The origin of these rocks are continental, educated on the mainland, and sea — educated on the seabed.

As a result of the shifts of the earth’s layers, earthquakes, floods occurred crushing of granites, volcanic glass, tuffs, porphyrites. On physical alteration and destruction of rocks influenced the crystallization of salt, freezing of water, the activity of microorganisms.

The formation of layers of marine clay took place with the application of clay substances in water currents, their accumulation and subsidence. Clay marine group are:

coastal-marine. Their place of formation of the coastal regions, river deltas and bays. Often the clay strata alternating with the coal, sand, silt;

– the lagoon. Clay, formed in marine lagoons contain high concentrations of sulfides, calcite, and iron. Among lacustrine alluvial rocks often refractory types;

– shelf. Rocks that were formed at depths greater than 200 m, have a more dense structure and uniform composition.

Continental clay are also divided by place of origin. They are:

– talus. Characteristic of mixed composition, its heterogeneity even in the same time the reservoir;

lake. The best refractory clay that is formed on the bottom and shores of the lakes. In their composition contains all components required for the manufacture of refractory materials;

– proluvial. They are formed by the destruction of rocks, washed and handed down by erosion furrows to the foot of the mountains. Their characteristic layering, porosity, non-uniform composition;

river. They can be found in floodplains, they contain large amounts of impurities in the composition, and often go into the gravel.

Still emit residual rocks with low ductility, formed by the weathering of rocks.


Clay mining. Methods of quarrying:

In our country the extraction of clay is in the Urals, in Eastern and Western Siberia. Often one field is the development of several types of clay. On the complexity of mining careers there are 3 groups:

– the first group. The development of upper soil layers with plant remains, work is underway on dredging loam;

– the second group. This compact breed is saturated with moisture, and deposits of lumpy rocks, with admixtures of gravel;

– the third group. Is developing a hardened shale formations, the frozen clay soil.

Methods of quarrying depend on the volume and depth of deposits, their location. The most common method of mining clay-containing rocks is the excavation of minerals in the aid of machinery – gear hobbing excavators. The undermining of the rock used in the deep development of large deposits. Kaolin white and blue clay is mined with the use of devices that create dense water jet. Often jetting is used at high humidity layer.

Production of materials for enterprises for the production of ceramics is gear hobbing machines by removing layers of different thickness. Before you design the training:

– the construction of access roads;

– clear career horizon;

– delivery of equipment.

Developed by soil and sand taken from the quarry and dumped into a dump, and clay are transported to the destination. If one field was found several varieties of clays, the development of the layers is carried out separately. This technology is called “Selective development”. It is more effective than gross production, which simultaneously cut all the layers.


The application and use of clay:

When connecting dry clay with water, it forms a plastic mass. Depending on the places of production and composition it is used in various fields and industries:

the production of ceramics. This is one of the main applications of clay. Different varieties are going to manufacture ceramics, pottery, porcelain. These materials are produced tableware, figurines, vases, Souvenirs. Although pottery has been known for a very long time, it continues to improve and now;

making of construction materials. Clay is the main component of the solutions, which are used in the manufacture of facing and masonry bricks, tiles. Clay or ceramic tiles is one of the best roofing materials. It is characterized by durability, strength, frost resistance, holds heat well, not “noise” in the rain;

the manufacture of cement. For the manufacture of cement use of clay slate, which contains 22% silica, 5% calcium oxide. The clay content in cement is not more than 25%, the proportion of the second component, limestone, accounting for 75%. Components diluted with water, the resulting mass is sent for firing. The obtained granulated clinker is cooled, crushed to a state of dust, add 5% gypsum;

technical ceramics. This category refers to a large group of ceramic products, which are characterized by increased hardness, heat resistance, resistance to abrasion and mechanical deformation. Principal of technoceramica — structural, instrumental, electroradiotechnics, ceramics with special properties. Is plumbing, electrical insulators, siteprovides headset, rollers, couplings, bushings. Corundum ceramic materials used in the manufacture of armor plates and body armor.


The advantages of using clay:

environmental safety. The composition of the material includes natural ingredients of natural origin.

temperature resistance. Dry, it retains its properties when exposed to high and low temperatures;

operational characteristics. Clay after processing acquire high strength and hardness;

universality. Due to the large variety of types and properties of clay is the material used in the manufacture of building materials, technical ceramics, decorative items, tableware.


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