The brick making process begins with the extraction of clay. The area where clay is mined is called a quarry. The quarry should be located close and conveniently to the plant, if possible in a dry place not flooded by rain, snow and groundwater.
The quarry must be developed in a certain order. Correct order clay mining provides ease of work, economical consumption of clay and obtaining more homogeneous raw materials.
In its natural state, clay is usually heterogeneous. Clays taken from different places of the same quarry and even the same face can be different in their composition, properties and moisture content. Usually this difference is especially great for clays taken from different depths of the quarry - some of them are plastic, others are sandy.
Therefore, clay in a quarry is mined in such a way as to obtain a mass consisting of clay taken from the entire thickness of its occurrence.
Clay extraction, depending on local conditions, can be manual or mechanized.
When manually extracting clay, they use ordinary bayonet shovels - spades. The most convenient shovels are pointed or semicircular. When developing very dense or frozen soils, crowbars and picks are used. To load the mined loose clay onto carts or wheelbarrows, you can use picking (scoop) shovels, and if the clay is very wet and sticks to the shovel, you can use a fork with fine teeth.
Clay can be transported to the plant, if the quarry is located close, in ordinary earth-carrying wheelbarrows on laid rolling boards.
If the quarry is remote from the plant, it is best to transport the clay by horses in special carts called grabs, or in tilting trolleys along narrow-gauge tracks. Grabbers can be two-wheeled or four-wheeled. For convenient unloading of clay, the side walls and bottom of four-wheeled grabbers are removable and removed during unloading, while in a two-wheeled grabber back wall reclines like the side of a car. Particularly convenient are carts that are unloaded through a bottom that can be folded down. Before loading the clay, the bottom is secured in a horizontal position with cap hangers to the side walls of the cart.
The development of a clay deposit using the manual method is carried out in the following sequence.
First, before extracting clay, it is necessary to remove the clearing, i.e., the top plant layer, and other top layers of soil unsuitable for production from the entire area planned for development this year.
The removed cleaning material must be taken to a place from where it cannot enter production. In the future, the mined-out part of the quarry can be filled with cleaning.
Rice. 7. Cutting trench for opening a quarry
After removing the clearing, or, as they say, stripping the quarry, they begin to develop it. If the quarry is located on the slope of a hill, it must be exposed in a straight line, and then the open face must be developed in a stepwise manner. To develop a quarry on a flat area, after removing the waste, it is necessary to dig a split trench about 4 m wide and 15-20 m long (Fig. 7).
The trench is gradually deepened to the bottom of the clay layer being mined in order to make a gentle entrance into the quarry.
Subsequently, as the quarry is developed, the trench at this level expands in all directions. In this case, the quarry is also developed in a stepwise manner.
Manual quarrying using a stepwise method is shown in Fig. 8. The height of the steps for ease of work is assumed to be equal to the bayonet of a shovel. With this method, clay is first taken with a shovel from one step, then from the second highest, then from the third, and so on up to the top. In this case, new steps are formed and the entire “staircase” seems to move along the face of the quarry by the width of the step (i.e., 30-40 cm)
Rice. 8. Manual quarrying in a stepwise manner
Thus, the steps are moved until the entire strip 1-1.5 m wide (along the length of the steps) has been mined to the end of the face. After this, they begin to develop the next strip of the same width along the face in the same way. The clay extracted from the steps is dumped onto trolleys, wheelbarrows or rakes.
The wall of the quarry face at a height of more than 1.5 m must have a slope. It is strictly prohibited to develop a quarry with steep face walls, as well as undermining, i.e., excavation of soil from the lower part of the wall, forming canopies hanging at the top, which can lead to collapse and accidents.
If the quality of the clay varies along the height of the face being mined, then clay from different levels along the face height must be dumped into each trolley, wheelbarrow or rake one by one. During further processing, the clay of different layers will mix and become fairly homogeneous.
If stones and other large inclusions are found in the clay, they must be selected manually and thrown into the mined-out area. If individual layers are clogged with numerous small inclusions, then all the clay clogged with these inclusions should be discarded. In cases where the clay in the quarry suddenly changes in appearance, its properties and suitability for brick production should be checked.
The developed quarry must be kept clean. Care must be taken to ensure that discarded tools, pieces of wood and other foreign objects are removed from the quarry.
Currently, thanks to the presence of various means of mechanization on collective farms, state farms, as well as the enterprises and organizations that patronize collective farms, it is possible to mechanize the processes of stripping a quarry and extracting clay using bulldozers or scrapers.
If stripping work is carried out with a bulldozer, then the unusable layer of soil is scraped off with the bulldozer's blade and moved to the side. When using a scraper for stripping operations, the scraped layer of soil fills the scraper bucket, which then transports the soil to a designated area, where it is emptied by lifting the bucket.
Bulldozers and scrapers can be used to pile clay into ridges for natural preparation within a short quarry distance from the ridge location. With a bulldozer, you can not only move clay from a quarry to a certain place, but also arrange it in several parallel shafts, which can then be easily shaped into regular piles or ridges. It is also easier to prepare clay into piles using a scraper.
The use of these mechanisms for stripping and clay harvesting will significantly speed up and reduce the cost of this work.
If the face is shallow, the clay is relatively homogeneous, and clay is transported by carts or vehicles, clay can also be extracted as follows: the slope of the walls of the face is arranged flat so that carts or vehicles can move along it. The clay is loosened (plowed) with a plow and loaded manually onto carts or vehicles. This method of work eliminates the most labor-intensive and difficult operation - digging clay by hand. To mechanize the loading of clay into vehicles, forklifts can also be used. Of course, in these cases, it is necessary to average the clay, choosing it not from one place, but evenly from different areas of the face.
Clay belongs to sedimentary type rocks. When dry, it exists in the form of lumps or dust, which when wet acquire plastic properties. Extraction of clay is the first stage in the process of producing bricks and numerous ceramic products.
This fossil is formed due to the destruction of rocks. The main material for the formation of clay layers is fossils, such as feldspar. After the destruction of the formation under the influence of atmospheric factors, silicates are formed from a number of clay minerals.
The clay consists of kaolinite, illite and other aluminosilicates, and also contains inclusions of sand and carbonates. Silica and alumina are the basis of clay minerals.
The color of the rock may vary due to pigment impurities and organic matter. Pure rock is usually gray in color; red, yellow, and blue types of clay are also common.
Some clay rocks are obtained as a result of the accumulation of the above-mentioned minerals, but for the most part, these are rocks that represent sediment from water currents accumulating at the bottom of reservoirs.
Based on its origin, this mineral is divided into subgroups.
Sedimentary clays. They are formed as a result of the application of water to destroyed rock layers.
Clays of this type are divided into marine and continental. From the name of the first it is clear that clay is formed on the seabed, in the second case the formation occurs on continents, in the bottom sediments of rivers and lakes.
The following are the characteristics of marine clay groups.
- Coastal and sea.
- Lagoon. They accumulate in sea or fresh lagoons. In the case of sea bays, clay is a heterogeneous mass and has numerous impurities.
- In fresh lagoons, the clay layers are quite thin and have fewer impurities. Deposits of fire-resistant clay are often found in such lagoons.
- Offshore. They are formed at a depth of about two hundred meters. A prerequisite is the absence of any kind of currents. It has a granulometric shape.
Continental clays are divided into the following groups:
- Deluvial. They have multi-layer granulometry;
- Ozernye. Clays of this origin include the best fire-resistant clay rocks that lie at the bottom of lakes. The advantage of this rock is that it contains all clay minerals.
There is another category - residual clays. These are, as a rule, low-plasticity rocks formed as a result of weathering of other fossils. These clays include kaolin and other illuvial clays.
Mining locations
Clay is ubiquitous, this is natural, since it belongs to sedimentary rocks, and is, in fact, rocks crushed to a powdery state.
Mining sites are often located along the banks of water bodies. Outcrops are numerous, but not all deposits are suitable for industrial production.
Where is clay mined in Russia? The most known deposits– Kyshtymskoye, Astafievskoye, Palevskoye. It is worth noting that fireproof and kaolin clay occurs much less frequently. Often, refractory varieties are adjacent to fire-resistant types.
Currently, clay is mined by quarrying. Clay pits can be of varying depths. Often different types of clays can be produced in one quarry.
Clay mining sites are divided into groups according to the degree of complexity of their development:
- Compacted clay, saturated with moisture – II;
- Lumpy, with an admixture of gravel – III;
- Hardened shale – IV;
- Loam – II;
- Frozen clay soil – IV;
- Soil with plant residues – I.
Quarrying methods
Development methods are different, they depend on the number of rock deposits and their location. Methods for obtaining clay:
- The most common method of extracting clay is based on excavating the fossil using hobbing excavators;
- Disruptive technologies are used for large deposits;
- Kaolin and blue clay are mined using hydromonitors. This is especially true when the layer humidity is high;
- For ceramics production enterprises, production is carried out in quarries with subsequent transportation by road or rail.
Mining Features
The excavation, or in other words, the excavation of clay is carried out by gear hobbing excavators by cutting off layers of various thicknesses.
- The steepness of a slope is an important parameter that characterizes the angle of inclination to the horizon or the ratio of the height to the underlying rock layer.
- Before mining rocks, preparatory work, which include clearing the quarry horizon, removing the cover, arranging access roads, and delivering equipment to the mine face.
- As a rule, the cost of preparatory work accounts for up to 30% of the total cost of clay extraction.
- Soil and sand are removed from the quarry to a special dump, and the target product is transported to the place of consumption. It often happens that several types of clay lie in a layer. In this case, each layer is mined separately. This technique is called selective clay production; it is much more effective than bulk mining, in which the product is cut simultaneously from all layers.
How clay is mined in the summer
In summer, clay is extracted using excavators. Since it lies in layers, it is better to cut it in layers of different thicknesses. Excavation is carried out until the equipment reaches the loam layer, after which the excavators are sent to other places of rock deposits.
A clay quarry can have different depths. IN summer period year, the area is cleared of soil and plant residues. After that, transport approaches to the mining site are arranged. Waste rocks such as sand are removed. If clay occurs at the level of the aquifer or below, drainage is installed. The target product is transported to the processing site.
At open method mining uses bulldozers or belt-type conveyors. If necessary, subversive measures are carried out.
How clay is mined in winter
In the cold season, with large volumes of work and high density of clay rocks, the explosive mining method is used.
- To prevent the soil from freezing, the excavation site is insulated with materials with low thermal conductivity - peat or sawdust.
- When extracting clays with a high degree of instability and quarry humidity, mineral extraction is carried out using hydraulic monitors.
In the north, where the soil freezes quite deeply, so-called hothouses are used. These are closed structures equipped with heaters - calorifiers. Using heaters, the mining site is heated. The greenhouses are equipped on special rollers, they are moved as needed.
The most economical development method is based on the use of belt-type spreaders and transport bridges.
Transportation
It is not always the case that a clay quarry is adjacent to production. Often the deposits are located outside populated areas. In addition, kaolinite clay High Quality, which is mined in clay quarries of the Russian Federation, is not a common occurrence. There is a need to transport raw materials to the place of processing.
Clay is transported by road and rail. When transporting clay by road, you must remember that the cargo must be covered with an awning. The volume of clay transported must correspond to the load-carrying capacity of the body, this will help avoid unwanted overpayments for unused space.
Transportation over long distances is best done by rail using tilting platforms.
The nuances of obtaining a production license
Legislation regulates the extraction of minerals, including clay. Subsoil use license – necessary condition rock mining on an industrial scale.
It is worth noting that a license is not needed if mining is carried out by persons who are not on the state balance sheet, without blasting, at a depth of no more than five meters. Without a license, for example, summer residents can mine clay on their own plots.
To obtain a license for clay extraction, contact specialists For the licensing procedure to be successful, it is best to contact specialists in this field. To obtain permission to use natural subsoil, you need to have certain knowledge and considerable experience in this field, otherwise there is a risk that the package of documents will be returned to the applicant.
How to obtain a clay mining license:
- First of all, you need to decide on the site;
- Prepare a package of documents that reflect the financial condition of the company;
- Pay state taxes;
- Participate in auctions.
- Having received a license, you need to develop, coordinate and approve a project for the development of clay deposits.
Clay is a very common rock. Complex, both in composition and in physical and technological properties. Pure rock consists of complex chemical compounds - “clay” minerals, which include aluminum, silicon and water. In mineralogy they are called hydrous aluminosilicates.
The properties of clay depend on its chemical and mineral composition. Earthy rock - clay easily dissolves in water, forming “suspensions” (dregs) or plastic dough, which retains its shape after drying and acquires the hardness of stone after firing. Also, another property of clay can be considered “sorption” - the ability to absorb from a liquid some substances dissolved in it. Since clay contains a large amount of aluminum oxide, it is used as a chemical raw material to produce sulfuric acid salts.
Characteristics and types
For ease of use, all existing clay was divided into the following types:
- Kaolin- the most popular type, white, consisting of the mineral kaolinite. It is used in the porcelain, earthenware and paper industries.
- Fire-clay, comes in white or gray. When fired, it can withstand temperatures of approximately 1580°. The composition includes kaolinite and hydromica minerals. Used to make fireproof cookware.
- Acid-resistant clay is a type of fireclay that contains iron, magnesium, calcium and sulfur.
- Molding clay- has increased plasticity and binding ability. Used as a fastening material in the manufacture of containers for metallurgical casting.
- Cement clay has a rich color palette. It is part of Portland cement.
- Brick clay- low-melting, contains a significant admixture of quartz sand. Widely used in brick production.
- Bentonite clay- the main forming mineral is montmorillonite. Rich color range. Has the highest whitening power. This type is indispensable for the purification of petroleum products, vegetable and lubricating oils.
- Mineral natural clay- used in medicine and cosmetology
(The picture shows a type of cosmetic clay)
In industrial practice, clay is divided into “fat” and “lean” groups. It all depends on the degree of contamination with quartz sand. In “fat” clays there is not a lot of sand, but in “lean” clays there is a large amount of it.
Field and production
Clay is widespread in nature and occurs at shallow depths. All this contributes to low production costs, making raw materials cheap. Typically, brick and tile factories are built on the clay deposit itself. The largest clay deposits are located in Ukraine and Russia. Relatively small accumulations of the rock are found in Georgia, Kazakhstan, Uzbekistan, Turkmenistan and other CIS countries.
Application of clay
Clay can be classified as a mineral raw material for mass consumption. It is used in a wide variety of industries, for example in the household sector, where dishes and other products are made. In the construction industry, for the production of building bricks of any color and cement. And also in industry: soap making, perfumery, textiles and many others.
Factories use a certain type of clay to purify petroleum products, vegetable oils and fats. Clay is also indispensable in art; plastic colored clay is an excellent material for creating sculptures. Has earned wide popularity in agriculture: for laying stoves, clay ceilings, whitewashing walls, etc.
Clay is a fine-grained sedimentary rock, dust-like when dry, plastic when moistened.
Origin of clay.
Clay is a secondary product formed as a result of the destruction of rocks during the weathering process. The main source of clay formations are feldspars, the destruction of which under the influence of atmospheric agents forms silicates of the group of clay minerals. Some clays are formed by the local accumulation of these minerals, but most are sediments from water flows that accumulate at the bottom of lakes and seas.
In general, according to their origin and composition, all clays are divided into:
- sedimentary clays, formed as a result of the transfer to another place and deposition there of clayey and other products of the weathering crust. Based on their origin, sedimentary clays are divided into marine clays, deposited on the seabed, and continental clays, formed on the mainland.
Among marine clays there are:
- Coastal- are formed in coastal zones (turbulence zones) of seas, open bays, and river deltas. They are often characterized by unsorted material. They quickly change into sandy and coarse-grained varieties. Replaced by sandy and carbonate deposits along the strike. Such clays are usually interbedded with sandstones, siltstones, coal seams and carbonate rocks.
- Lagoon- are formed in sea lagoons, semi-enclosed with a high concentration of salts or desalinated. In the first case, the clays are heterogeneous in granulometric composition, insufficiently sorted and wind together with gypsum or salts. Clays from desalinated lagoons are usually finely dispersed, thin-layered, and contain inclusions of calcite, siderite, iron sulfides, etc. Among these clays there are fire-resistant varieties.
- Offshore- are formed at a depth of up to 200 m in the absence of currents. They are characterized by a uniform granulometric composition and large thickness (up to 100 m or more). Distributed over a large area.
Among the continental clays there are:
- Deluvial- characterized by a mixed granulometric composition, its sharp variability and irregular layering (sometimes absent).
- Ozernye with a uniform granulometric composition and finely dispersed. All clay minerals are present in such clays, but kaolinite and hydromicas, as well as minerals of hydrous oxides Fe and Al, predominate in clays of fresh lakes, and minerals of the montmorillonite group and carbonates predominate in clays of salt lakes. Belongs to lacustrine clays best varieties refractory clays.
- Proluvial, formed by temporary flows. Characterized by very poor sorting.
- River- developed in river terraces, especially in the floodplain. Usually poorly sorted. They quickly turn into sands and pebbles, most often non-stratified.
Residual - clays resulting from the weathering of various rocks on land, and in the sea as a result of changes in lavas, their ashes and tuffs. Down the section, residual clays gradually transform into parent rocks. The granulometric composition of residual clays is variable - from fine-grained varieties in the upper part of the deposit to uneven-grained ones in the lower part. Residual clays formed from acidic massive rocks are not plastic or have little plasticity; Clays formed during the destruction of sedimentary clay rocks are more plastic. Continental residual clays include kaolins and other eluvial clays. IN Russian Federation In addition to modern ones, ancient residual clays are widespread - in the Urals, in the West. and Vost. Siberia (there are also many of them in Ukraine) - of great practical importance. In the mentioned areas, clays predominantly montmorillonite, nontronite, etc. appear on basic rocks, and on medium and acidic rocks - kaolins and hydromica clays. Marine residual clays form a group of bleaching clays composed of minerals of the montmorillonite group. 
Clay is everywhere. Not in the sense - in every apartment and plate of borscht, but in every country. And if there are not enough diamonds, yellow metal or black gold in some places, then there is enough clay everywhere. Which, in general, is not surprising - clay, sedimentary rock, is a stone worn by time and external influences to the state of powder. The last stage of stone evolution. Stone-sand-clay. However, the last one? And sand can form into stone - golden and soft sandstone, and clay can become brick. Or a person. Who's got some luck?
The clay is colored by the creator stone and salts of iron, aluminum and similar minerals that happen to be nearby. Various organisms reproduce, live and die in clay. This is how red, yellow, blue, green, pink and other colored clays are obtained.
Previously, clay was mined along the banks of rivers and lakes. Or they dug a hole specifically for it. Then it became possible not to dig the clay yourself, but to buy it from a potter, for example. During our childhood, we dug out ordinary red clay ourselves, and bought noble white clay in artists’ stores or, especially pure clay, in a pharmacy. Nowadays, a nice little shop selling cosmetics will certainly have clay. True, not entirely in its pure form, but mixed with various detergents, moisturizers and nourishing agents.
Our land is rich in clay. Roads and paths cut into loamy soil become sources of dust in the heat, and in slush they become pure mud. Clay dust covered the traveler from head to toe and added to the housework of the housewives whose house stood by the road. Surprisingly, there was no less dust near roads covered with asphalt. True, he turned from red to black. Ledum, thickly mixed with clay, not only prevents a pedestrian from walking and a wheel from moving, but also, depending on the mood, you don’t mind swallowing a boot or a jeep.
Clay consists of one or more minerals of the kaolinite group (derived from the name of the locality Kaolin in the People's Republic of China (PRC)), montmorillonite, or other layered aluminosilicates (clay minerals), but may also contain sand and carbonate particles. As a rule, the rock-forming mineral in clay is kaolinite, its composition is: 47% silicon (IV) oxide (SiO 2), 39% aluminum oxide (Al 2 O 3) and 14% water (H 2 0). Al2O3 And SiO2- constitute a significant part of the chemical composition of clay-forming minerals.
The diameter of clay particles is less than 0.005 mm; Rocks consisting of larger particles are usually classified as loess. Most clays are gray in color, but there are clays in white, red, yellow, brown, blue, green, purple and even black. The color is due to impurities of ions - chromophores, mainly iron in valence 3 (red, yellow) or 2 (green, bluish).
Dry clay absorbs water well, but when wet it becomes waterproof. After kneading and mixing, it acquires the ability to take different shapes and retain them after drying. This property is called plasticity. In addition, clay has a binding ability: with powdery solids (sand) it produces a homogeneous “dough” that also has plasticity, but to a lesser extent. Obviously, the more sand or water admixtures in the clay, the lower the plasticity of the mixture.
According to the nature of the clays, they are divided into “fat” and “lean”.
Clays with high plasticity are called “fat” because when soaked they give a tactile sensation of a fatty substance. “Fatty” clay is shiny and slippery to the touch (if you take such clay on your teeth, it slips), and contains few impurities. The dough made from it is tender. Bricks made from such clay crack when dried and fired, and to avoid this, so-called “lean” substances are added to the mix: sand, “lean” clay, burnt brick, potter’s scrap, sawdust and etc.
Clays with low plasticity or non-plasticity are called “lean”. They are rough to the touch, with a matte surface, and when rubbed with a finger, they easily crumble, separating earthy dust particles. “Skinny” clays contain a lot of impurities (they crunch on the teeth); when cut with a knife, they do not produce shavings. Bricks made from “lean” clay are fragile and crumbly.
An important property of clay is its relationship to firing and, in general, to elevated temperatures: if soaked clay in air hardens, dries and is easily wiped into powder without undergoing any internal changes, then at high temperatures chemical processes occur and the composition of the substance changes.
At very high temperatures, clay melts. The temperature of melting (beginning of melting) characterizes the fire resistance of clay, which is not the same for its different varieties. Rare types of clay require colossal heat for firing - up to 2000°C, which is difficult to obtain even in factory conditions. In this case, there is a need to reduce fire resistance. The melting temperature can be reduced by adding the following substances (up to 1% by weight): magnesia, iron oxide, lime. Such additives are called fluxes (fluxes).
The color of the clays is varied: light gray, bluish, yellow, white, reddish, brown with various shades.
Minerals contained in clays:
- Kaolinite (Al2O3 2SiO2 2H2O)
- Andalusite, disthene and sillimanite (Al2O3 SiO2)
- Halloysite (Al2O3 SiO2 H2O)
- Hydrargillite (Al2O3 3H2O)
- Diaspore (Al2O3 H2O)
- Corundum (Al2O3)
- Monothermite (0.20 Al2O3 2SiO2 1.5H2O)
- Montmorillonite (MgO Al2O3 3SiO2 1.5H2O)
- Muscovite (K2O Al2O3 6SiO2 2H2O)
- Narkite (Al2O3 SiO2 2H2O)
- Pyrophyllite (Al2O3 4SiO2 H2O)
Minerals contaminating clays and kaolins:
- Quartz(SiO2)
- gypsum (CaSO4 2H2O)
- dolomite (MgO CaO CO2)
- Calcite (CaO CO2)
- Glauconite (K2O Fe2O3 4SiO2 10H2O)
- Limonite (Fe2O3 3H2O)
- Magnetite (FeO Fe2O3)
- Marcasite (FeS2)
- Pyrite (FeS2)
- Rutile (TiO2)
- Serpentine (3MgO 2SiO2 2H2O)
- Siderite (FeO CO2)
Clay appeared on earth many thousands of years ago. Its “parents” are considered to be rock-forming minerals known in geology - kaolinites, spars, some varieties of mica, limestones and marbles. Under certain conditions, even some types of sand transform into clay. All known rocks that have geological outcrops on the surface of the earth are subject to the influence of the elements - rain, whirlwind storms, snow and flood waters.
Temperature changes day and night and heating of the rock by the sun's rays contribute to the appearance of microcracks. Water gets into the cracks that form and, freezing, breaks the surface of the stone, forming a large amount of tiny dust on it. Natural cyclones crush and grind dust into even finer dust. Where the cyclone changes its direction or simply dies down, huge accumulations of rock particles form over time. They are pressed, soaked in water, and the result is clay.
Depending on what rock the clay is formed from and how it is formed, it acquires different colors. The most common clays are yellow, red, white, blue, green, dark brown and black. All colors, except black, brown and red, indicate the deep origin of the clay.
The colors of clay are determined by the presence of the following salts in it:
- red clay - potassium, iron;
- greenish clay - copper, ferrous iron;
- blue clay - cobalt, cadmium;
- dark brown and black clay - carbon, iron;
- yellow clay - sodium, ferric iron, sulfur and its salts.
Various colored clays.
We can also give an industrial classification of clays, which is based on the assessment of these clays based on a combination of a number of characteristics. For example, this appearance products, color, sintering (melting) interval, resistance of the product to sudden changes in temperature, as well as the strength of the product to impacts. Based on these characteristics, you can determine the name of the clay and its purpose:
- china clay
- earthenware clay
- white-burning clay
- brick and tile clay
- pipe clay
- clinker clay
- capsule clay
- terracotta clay
Practical use of clay.
Clays are widely used in industry (in the production ceramic tiles, refractories, fine ceramics, porcelain-faience and sanitary ware, construction (production of brick, expanded clay and other building materials), for household needs, in cosmetics and as a material for artistic works (modelling). Expanded clay gravel and sand produced from expanded clay by annealing with swelling are widely used in the production of building materials (expanded clay concrete, expanded clay concrete blocks, Wall panels etc.) and as a heat and sound insulating material. This is a lightweight porous building material obtained by firing low-melting clay. It has the shape of oval granules. It is also produced in the form of sand - expanded clay sand.
Depending on the clay processing mode, expanded clay of different bulk density (volume weight) is obtained - from 200 to 400 kg/M3 and higher. Expanded clay has high heat and noise insulation properties and is used primarily as a porous filler for lightweight concrete, which has no serious alternative. Expanded clay concrete walls are durable, have high sanitary and hygienic characteristics, and expanded clay concrete structures built more than 50 years ago are still in use today. Housing built from prefabricated expanded clay concrete is cheap, high quality and affordable. The largest producer of expanded clay is Russia.
Clay is the basis of pottery and brick production. When mixed with water, clay forms a dough-like plastic mass suitable for further processing. Depending on the place of origin, natural raw materials have significant differences. One can be used in its pure form, the other must be sifted and mixed to obtain a material suitable for the manufacture of various trade items.
Natural red clay.
In nature, this clay has a greenish-brown color, which is given to it by iron oxide (Fe2O3), which makes up 5-8% of the total mass. When fired, depending on the temperature or type of oven, the clay acquires a red or whitish color. It kneads easily and can withstand heating of no more than 1050-1100 C. The great elasticity of this type of raw material allows it to be used for working with clay plates or for modeling small sculptures.
White clay.
Its deposits are found all over the world. When wet, it is light gray, and after firing it becomes whitish or ivory. White clay is characterized by elasticity and translucency due to the absence of iron oxide in its composition.
Clay is used to make dishes, tiles, and plumbing items, or for crafts made from clay plates. Firing temperature: 1050-1150 °C. Before glazing, it is recommended to work in an oven at a temperature of 900-1000 °C. (Firing of unglazed porcelain is called bisque firing.)
Porous ceramic mass.
Clay for ceramics is a white mass with a moderate calcium content and high porosity. Its natural color ranges from pure white to greenish-brown. Fires at low temperatures. Unfired clay is recommended, as for some glazes a single firing is not sufficient.
Majolica is a type of raw material made from fusible clay with a high content of white alumina, fired at a low temperature and covered with a glaze containing tin.
The name "majolica" comes from the island of Mallorca, where it was first used by the sculptor Florentino Luca de la Robbia (1400-1481). Later this technique was widespread in Italy. Ceramic trade items made from majolica were also called earthenware, since their production began in workshops for the production of earthenware.
Stone ceramic mass.
The basis of these raw materials are fireclay, quartz, kaolin and feldspar. When wet it has a black-brown color, and after wet firing it has an ivory color. When applying glaze, stone ceramics are transformed into a durable, waterproof and fireproof product. It can be very thin, opaque or in the form of a homogeneous, densely sintered mass. Recommended firing temperature: 1100-1300 °C. If it is disturbed, the clay may crumble. The material is used in various technologies for making commercial pottery items from lamellar clay and for modeling. Trade items made of red clay and stone ceramics are distinguished depending on their technical properties.
Clay for porcelain trade objects consists of kaolin, quartz and feldspar. It does not contain iron oxide. When wet it has a light gray color, after firing it is white. Recommended firing temperature: 1300-1400 °C. This type of raw material is elastic. Working with it on a pottery wheel requires high technical costs, so it is better to use ready-made forms. This is a hard, non-porous clay (with low water absorption - Ed.). After firing, the porcelain becomes transparent. Glaze firing takes place at a temperature of 900-1000 °C.
Various porcelain trade items, molded and fired at 1400°C.
Large-pored, coarse-grained ceramic materials are used for the manufacture of large-sized commercial items in construction, small-form architecture, etc. These varieties can withstand high temperatures and thermal fluctuations. Their plasticity depends on the content of quartz and aluminum (silica and alumina - Ed.) in the rock. The overall structure contains a lot of alumina with a high chamotte content. The melting point ranges from 1440 to 1600 °C. The material sinteres well and shrinks slightly, so it is used to create large objects and large-format wall panels. When making artistic objects, the temperature should not exceed 1300°C.
This is a clay mass containing an oxide or colorful pigment, which is a homogeneous mixture. If, penetrating deep into the clay, part of the paint remains suspended, then the even tone of the raw material may be disrupted. Both colored and ordinary white or porous clay can be purchased in specialized stores.
Masses with colored pigment.
Pigments- these are inorganic compounds that color clay and glaze. Pigments can be divided into two groups: oxides and colorants. Oxides are a naturally occurring basic material that forms among the rocks of the earth's crust, is purified and atomized. The most commonly used are: copper oxide, which takes on a green color in the oxidizing firing environment; cobalt oxide, which produces blue tones; iron oxide, which gives blue tones when mixed with glaze, and earth tones when mixed with clay. Chromium oxide gives the clay an olive green color, magnesium oxide gives it brown and purple tones, and nickel oxide gives it a grayish-green color. All these oxides can be mixed with clay in a proportion of 0.5-6%. If their percentage is exceeded, the oxide will act as a flux, lowering the melting point of the clay. When painting trade items, the temperature should not exceed 1020 °C, otherwise firing will not produce results. The second group is dyes. They are obtained industrially or by mechanical processing of natural materials, which represent a full range of colors. Dyes are mixed with clay in a proportion of 5-20%, which determines the light or dark tone of the material. All specialized stores have an assortment of pigments and dyes for both clay and engobes.
Preparing ceramic mass requires a lot of attention. It can be composed in two ways, which give completely different results. A more logical and reliable way: add dyes under pressure. A simpler and, of course, less reliable method: mix dyes into the clay by hand. The second method is used if there is no exact idea about the final coloring results or there is a need to repeat certain colors.
Technical ceramics.
Technical ceramics is a large group of ceramic trade items and materials obtained by heat treatment of a mass of a given chemical composition from mineral raw materials and other high-quality raw materials that have the necessary strength, electrical properties (high volumetric and surface resistivity, high electrical strength, small tangent angle dielectric losses).
Cement production.
To make cement, calcium carbonate and clay are first extracted from quarries. Calcium carbonate (approximately 75% of the quantity) is crushed and thoroughly mixed with clay (approximately 25% of the mixture). Dosing of starting materials is an extremely difficult process, since the lime content must correspond to the specified amount with an accuracy of 0.1%.
These ratios are defined in the specialized literature by the concepts of “calcareous”, “siliceous” and “alumina” modules. Because the chemical composition Due to the dependence of the starting raw materials constantly fluctuating due to their geological origin, it is easy to understand how difficult it is to maintain a constant modulus. In modern cement plants, computer control in combination with automatic analysis methods has proven itself well.
Properly composed sludge, prepared depending on the chosen technology (dry or wet method), is introduced into a rotary kiln (up to 200 m long and up to 2-7 m in diameter) and fired at a temperature of about 1450 °C - the so-called sintering temperature. At this temperature, the material begins to melt (sinter), it leaves the kiln in the form of more or less large lumps of clinker (sometimes called Portland cement clinker). Firing occurs.
As a result of these reactions, clinker materials are formed. After leaving the rotary kiln, the clinker enters the cooler, where it is sharply cooled from 1300 to 130 °C. After cooling, the clinker is crushed with a small addition of gypsum (maximum 6%). The size of cement grains ranges from 1 to 100 microns. It is better illustrated by the concept of “specific surface area”. If we sum up the surface area of the grains in one gram of cement, then, depending on the grinding thickness of the cement, we get values from 2000 to 5000 cm² (0.2-0.5 m²). The predominant part of cement in special containers is transported by road or rail. All overloads are performed pneumatically. A minority of cement products are delivered in moisture- and tear-resistant paper bags. Cement is stored at construction sites mainly in liquid and dry states.
Supporting Information.
First of all, it should be noted that in this article I am looking at clay that is suitable for modeling - a hobby that you like to devote a little time to. After all, what we're talking about is - where to get clay and, of course, for industrial scale production, clay mining is very different from mining to satisfy one’s own creative needs.
If you were preparing to open your own industrial production line clay products- I would advise you to contact the suppliers of the material, test the clay and conclude a supply agreement. Unless, of course, you own a plot of land that is a significant and extensive source of this natural material..
For small-scale production and simple modeling, there are only two answers to the question of where to find clay: either in a store or in the ground.
The easiest way to prepare clay is to buy it. No, I’m not at all going to sell you clay, as it would be done on other materially interested resources, but I just want to say that a number of stationery stores sell powdered and ready-made clay, packaged in various packages. This is, most often, high-quality clay, ideal for learning the basics of modeling and the basics of sculpture. A kilogram of powdered clay is enough to master plastic arts.
If a waste Money on natural material somehow contradicts your principles, then the second method is ideal for such cases.
Where can you get clay?
If you look closely, red clay deposits can be found everywhere, at least in our middle zone.
- Places where preparations are made for construction work. Visit any construction site. The foundation pits have mountains of rock, and among them, most likely, there will be exposed clay deposits. This also includes:
- road construction. By the way, when creating embankments, they try to get rid of clay, since it spoils any road surface;
- places of communication (where trenches are dug - under a pipeline, for example);
- quarries for the extraction of natural materials, even if they mine sand, there is a chance to find dumps of clay rocks and all that remains is to find a way to get to the protected site..
- Natural places where clay forms
- at the dacha (if you dig deeper and in different places, there is a chance to stumble upon deposits);
- on the banks of rivers and ravines you can find screes, where clay is visible among the layers of rock;
- in places where water does not drain for a long time - a sure sign of the presence of clay.
The most important thing in finding clay is to choose the clay suitable for modeling based on its properties.
Determining the right clay is quite simple. Roll a small roller in your hand and try to bend it smoothly. The desired clay should not have cracks at the bend. If you still couldn’t find plastic clay, don’t despair - you can make something out of thin clay, you just have to be more careful and careful, omit some of the small details and make the shapes smoother. When fired, such clay exhibits less shrinkage and cracks, but the surface is rougher and less moisture resistant. For pottery production, the selection of clay is more strict and demanding.
If the quality of the clay does not suit you, you should give it the necessary properties by working magic on it using simple but labor-intensive methods, for example,