What materials are used in the production of ceramics. Raw materials for ceramic materials and products. Topic: Ceramic materials

Ceramics is one of the main materials used in industry and everyday life. It is called the third industrial material, along with metals and polymers. This section presents types of ceramics and discusses the technology for manufacturing ceramic products. Particular attention is paid to methods of molding ceramic products.

b HISTORY OF CERAMICS

Ceramics was the first artificial material created by man long before the production of glass and metal, the production of plastics and composites. Ceramic products, unlike wooden and metal ones, are durable and resistant to changes in natural conditions, so archaeologists study the history of disappeared cities and countries using ceramic shards. Archaeological excavations carried out on the territory of many states provide extensive material for the study of this most interesting area of ​​human creative activity.

The invention of ceramics was helped by the unique properties of clay minerals, which allowed primitive people to sculpt vessels and figurines from wet clay, which, after firing in the flame of a fire, acquired strength. (As the Bible says, the first man on Earth - Adam - was also created by God from clay.)

The presence of clay, an easily accessible natural material, led to the rapid and widespread development of ceramic craft at the very dawn of human history, during the period of the primitive communal system. Having appeared in the Mesolithic era, it was developed already in the Neolithic era.

The first ceramic products were vessels for water and food with thick walls and a porous shard; for ease of installation in the ground, the bottom of such a vessel was round or conical. Crushed shells and crushed granite were added to the clay to give it strength during firing. Using fingerprints, scientists have determined that the oldest ceramic vessels were made by women. Such vessels were sculpted from strands and decorated with stamps in the form of pits, stripes, and grooves of various shapes. Depending on the clay used, the products ranged in color from terracotta to black. Later, colored clays with predominantly red, white, yellowish or dark colors began to be used for decoration, covering individual parts of the design (engobes). Some cultures began to use polishing - smoothing the surface.

The first glazed products appeared in the 4th-3rd millennium BC, in the regions of the Near and Middle East. Ceramic products (colored glazed bricks and facing tiles that make up a monumental panel) were used to decorate palace and religious buildings. The resulting glaze contained many alkalis and was fritted.

The most important factor in improving ceramic craftsmanship was the invention of the potter's wheel (IV millennium BC), the use of which sharply increased labor productivity and improved the quality of products. Men began to engage in pottery making.

In Ancient Egypt, vessels were made from coarse mass; finely chopped straw was added to the clay to reduce the viscosity of the clay, speed up drying and prevent large shrinkage of the product. The molding of vessels of heavy shapes in the Neolithic and Predynastic periods was carried out manually; later, a round mat, the predecessor of the potter's wheel, was used as a rotating stand. They also began to use molding on rope blanks. In Egypt, pottery kilns made of clay appeared, twice the height of a person, resembling a pipe expanding upward; the kiln door through which fuel was loaded was located at the bottom, and the vessels were loaded from above and the potter climbed the ladder.

Later in Egypt the mass becomes finer and the forms more varied, with relief and engraved designs. In addition to dishes, vases and bricks, the Egyptians made clay figurines, often with animal heads, necklaces, images of scarabs, children's toys, seals, even sarcophagi, etc.

The color of Egyptian ceramics depended on the type of clay, decoration (engobe) and firing. To make it, they used mainly two types of clay: brown-gray with a fairly large amount of impurities (organic, ferrous and sand), which acquired a brown-red color when fired, and gray calcareous clay with almost no organic impurities, which after firing acquired different shades of gray. colors, brown and yellowish color.

Gradually, the glazing process began to spread in Ancient Greece. Decoration with painting was carried out on a raw shard. The main methods of making ceramic vessels in Greece were hand-molding the vessel from flagella, molding on rope blanks and molding on a potter's wheel. Greek ceramics reached its peak in the 6th-5th centuries. BC.

In Ancient Greece, vases were not a luxury item - there were a lot of them and they were made from simple clay, and only black “varnish” (flux engobe) was used for painting. But with a small variety of materials used (the Greeks did not know either transparent glazes or colored enamels), painted vases turned into genuine works of art, which had a huge influence on the development of the entire world of decorative and applied art.

Painting of ancient Greek ceramics is usually divided into four styles:

• 1) IX-VIII centuries. BC. - geometric style - painting in the form of a geometric ornament with conventionally stylized figures of animals and people;
• 2) end of the 7th century. BC. - carpet, or orientalizing, style - painting with polychrome ornamental belts with oriental patterns and images of animals and fantastic creatures;
• 3) VI century. BC. - black-figure style - painting with multi-figure compositions from the life of the gods with black “varnish” on an unpainted yellow, orange or pinkish background;
• 4) around 530 BC - red-figure style - when the background was covered with black “varnish”, the unpainted figures had the natural color of a clay shard. This technique gave the master the opportunity to draw forms in more detail, conveying the natural movement of the figure.

Etruscan ceramics (XII-V centuries BC) are not inferior to Greek in terms of technology, but have less artistic value.

Etruscan pottery can be divided into two groups:

• 1) copies of Greek vases (amphoras and bowls);
• 2) unpainted vessels of the Central Asian and Egyptian type with roughly made plastic decorations. Based on the color of the shard, they are divided into black (bucchero, when fired, the clay acquired a black color) and red (impasto).

Roman culture inherited many Greek traditions without the reverent attitude towards ceramics, as was the case in Ancient Greece. Ceramic products are no longer works of art, but ordinary household products that, in the Roman style, have a purely utilitarian, pragmatic meaning. A hand-made pottery wheel was used to make dishes. The design of pottery kilns remained essentially unchanged, but kilns for mass production often reached larger sizes and allowed higher firing of ceramics. Roman ceramists made pots, soldiers' cauldrons, frying pans, water jugs, milk dishes, goblets in the form of bowls and glasses, large dishes, plates, gravy boats, and salad bowls. Roman builders widely used ceramics to create complex architectural details.

Initially, painted ceramics became widespread in Ancient Rome, but gradually it lost its artistic value and painting completely replaced the relief on pottery covered with red “varnish.” The ceramists of Arretium in Italy have achieved perfection in the production of red glaze, which has an even color and a shiny surface reminiscent of the shine of sealing wax.

For decoration, we used well-known techniques for making low relief on the outer surface of the walls using molds and stamps. The reliefs on some Arretine vessels were created using stamps that had “negative” in-depth images. They were imprinted in a soft ceramic mass on the surface of the vessels, and then covered with red “varnish” and fired in kilns.

The most active production of ceramic products in Kievan Rus began in the 8th-12th centuries. Initially, the products were made by modeling, but at the end of the 9th - beginning of the 10th centuries. There was a transition to pottery technology.

Various fillers were added to the mass to give strength: sand, crushed stone, mica, straw and chaff. To give the products strength, they began to decorate them by heating them in clean water, dipping them in a warm bread solution, and blackening them in an oven. The main products were various types of dishes (pots, jars, jugs, bowls), children's toys, lamps, washstands, bricks, facing tiles.

In the X-XI centuries. a manual potter's wheel replaces a foot wheel, which rotates faster and frees the potter's hands, which again changes the technology - the process of preliminary rough sculpting of the product is eliminated.

The Tatar-Mongol yoke threw away all the achievements of Russian potters of the 9th-12th centuries: some vessels completely disappeared, the ornaments were simplified, the technology of glazing was almost completely forgotten, and after the overthrow of the yoke, for another three centuries the products were distinguished by monotony and roughness of shape.

The culture of ceramic production in Western Europe was greatly influenced by Spanish-Moorish ceramics coated with tin glaze. At first, in Italy, only Spanish ceramics imported into the country were called “majolica” at the end of the 14th century. In Italy, the production of such ceramics began to develop intensively, and in the 16th century. The name "majolica" began to be applied to Italian ceramics.

In Italy, the ceramist Luca della Robbia (1399(1400)-1482) was the first to use the technique of glazing terracotta in circular sculpture and reliefs for the facades and interiors of buildings. His products began to be called majolica, and the glazes he developed became a secret of the della Robbia family until the 16th century. the production of majolica sculpture remained the privilege of the della Robbia family.

Covering the pieces with white pewter glaze created the perfect backdrop for painting. At first, the design was simply applied to the raw glaze (el fresco), and then the technology was improved by applying an additional coating of transparent glaze.

At first, most Italian ceramic products served only decorative purposes, but later decorativeness and utilitarianism were combined in albarelli - antique vessels of the Renaissance.

In turn, Italian majolica had a significant influence on the development of ceramics in Germany in the 15th century, as well as in France in the 16th-18th centuries, where it became known as “faience.”

In France, Bernard Palissy (circa 1510-1589 (1590)) is considered the founder of faience, who developed his own recipes for white enamel and various glazes - watering. He worked with “rural clays” and created numerous decorative works (mainly decorative dishes), in both a naturalistic and mythological spirit. At the same time, another technology is being developed in France - firing at low temperatures with painting on a pre-fired glaze.

Another technological type of ceramics of that time was stone mass. In the XIV century. German potters invented stone mass. It was mass produced in the XIV-XVII centuries.

Until the 15th century production technology was improved, relief decoration began to be used, and only by the beginning of the 16th century. stone ceramics acquired the classic appearance that it has now.

Thanks to the low-dispersity composition of the mass and slight shrinkage, the technology made it possible to decorate the walls of vessels with very thin and elaborate reliefs. The stamps for their manufacture were cut out separately and imprinted on a dried vessel. Due to the high firing temperature, up to 1300°C, the porosity of the shard was reduced. Therefore, utilitarian dishes made of stone mass often could not be glazed, but most vessels were still covered with a colorless salt glaze during firing. Stone ceramics acquired strength, which made it possible to export it far from the place of production: to Europe, to Russia, and even to North America.

When stone pottery came to England, ceramist Josiah Wedgwood used it to invent better earthenware masses - basalt shards, cream masses and “jasper masses”, from which the famous blue vases with white relief in the classicist style were made.

In the 16th century Chinese porcelain was brought to Europe, where it became the most coveted jewel; porcelain products were in every palace in Europe and Russia. Expensive porcelain items were displayed and made it possible to demonstrate the high status, wealth and good taste of the owner. Even broken items were not thrown away; porcelain shards were set in precious metals and worn like beads on a gold chain. In the 17th century A fashion appeared for decorative painting of Chinese porcelain: the main painting motifs were various flowers (peonies, chrysanthemums, lotus), pine branches, birds and animals, dragons.

The Europeans really wanted to reveal the secret of making porcelain. It is believed that as a result of these experiments, faience, stone products and varieties of soft porcelain appeared. At first these were attempts by Italian masters, and in Florence in 1575 “Medici porcelain” was obtained. In its properties it was between hard and soft porcelain, had a yellowish color, was transparent thanks to white clay from Vicenza and was covered with a white majolica glaze. Cobalt oxide (blue color) and sometimes manganese oxide (bluish-purple color) were used for painting. The products were decorated with stylized flowers, branches, and birds. Such porcelain was produced until the first quarter of the 17th century. inclusive.

Then French ceramists at the end of the 17th century. conducted successful experiments in the production of porcelain (manufactories in Rouen, Saint-Cloud, Mennesy, Chantilly, Vincennes, producing products from soft porcelain). From 1673 to 1696, the Rouen manufactory produced fragile, transparent soft porcelain in a milky shade. Blue, red and green underglaze paints were used for painting.

From 1670 to 1766, at the Saint-Cloud factory, soft porcelain was created, the products from which had simple shapes, thick cream-colored shards and were covered with a shiny transparent dense glaze that covered the relief. For decoration, a pattern of molded or superimposed flowers and leaves, relief floral decoration and relief gilding were used.

Blue, turquoise, yellow and green overglaze paint were used for painting. Products were often set in silver.

In the 18th century Many factories producing soft porcelain opened in Britain: Chelsea, Bow, Derby, Worcester, Spode, Coalport, Minton. Each of them was distinguished by its own handwriting and style. The Chelsea factory produced decorative, impractical soft porcelain items from 1750 to 1784. At production in Bow in 1748, bone ash was first added to the mass and bone china, distinguished by its whiteness, was obtained; At the factory in Derby, figurines were produced from 1750, competing with Chelsea, and from 1764 to 1769, soapstone began to be used in the production of porcelain.

Varieties of soft porcelain of the 16th-17th centuries. had a complex composition, yellow color of the shard, and were greatly deformed during firing, but some types of soft porcelain, after improvements in composition and technology, continue to be produced to this day, such as bone china.

The presence of high porosity, fragility, and severe deformation during firing of soft porcelain products forced Europeans to look for a recipe for hard porcelain. In Saxony, from Elector Augustus in 1709 (1710), the alchemist Johann Friedrich Böttger, with the help of the scientist Ehrenfried Walter von Tschirnhaus, received samples of hard porcelain. They selected raw materials for porcelain and glazes, raised the firing temperature to 1300°C and developed high-temperature firing technology.

In 1710, the Meissen manufactory opened, which began to produce vessels similar in shape to Delft faience, vessels with double walls, decorated with carvings on the outside, cutlery and various sculptures were produced (one of the first sculptures was the figure of Augustus the Strong).

Morals of Europeans in the 18th century. became freer, and despite the efforts of the ruler of Saxony, Frederick Augustus I, to keep the technology of hard porcelain secret, Meissen masters went to other countries along with the secrets of production. Porcelain quickly spread to European cities and replaced the production of earthenware.

In France, at the Sevres manufactory, soft Sevres porcelain was produced in 1750, and from 1756 they began to produce hard porcelain. The factory developed an exquisitely refined style of Sèvres porcelain; products with painted gilded plastic and sculptures made of white unglazed porcelain (bisque) are especially characteristic.

Russian ceramics, after a decline caused by the Tatar-Mongol yoke, was revived again in the 14th-15th centuries. The main center became the Goncharnaya Sloboda in Moscow, where by the 17th century. A wide range of dishes, toys, lamps, etc. are produced.

In the 16th century In Russia, tsenin craft emerged (making clay objects with white enamel coating). Most tsenin products are tiles made on a clay basis, used to decorate temples and home furnishings. When describing the royal and boyar's chambers in the 16th century. There are certainly references to Tsenin stoves covered with white tiles with a blue pattern.

At the beginning of the 18th century. Gzhel craftsmen made simple white dishes and glazed dishes with multi-colored glazes and artistic painting - Russian majolica. The products were very diverse: sculpture, dishes and even sets. However, rich people wanted to have porcelain products.

In Russia, at the direction of Peter I, since 1718, attempts have been made to discover porcelain. In 1724, Afanasy Kirillovich Grebenshchikov opened the first tsenin (majolica) factory in Moscow and supplied his products to the imperial court. At first, smoking pipes were produced according to Dutch samples, then tiles - first in relief, then smooth with painting, and from the late 1730s. - valuable (enamel-coated) dishes. The factory began to produce high-quality majolica dishes painted with blue and three-color patterns on raw light blue enamel. In 1746 (before D.V. Vinogradov), the son of A.K. Grebenshchikov, Ivan Afanasyevich, independently discovered the secret of porcelain production, but did not receive permission to produce it and experiments on creating porcelain at the Grebenshchikov factory were discontinued.

According to the official version, porcelain appeared in Russia under Elizabeth Petrovna in 1746, but this recipe was developed by a Russian master who studied abroad (Bergmeister) Dmitry Ivanovich Vinogradov. Since 1744, he conducted experiments at the first porcelain (porcelain) Imperial manufactory under the leadership of Gunther and developed a technology for the production of porcelain based on several varieties of Gzhel clay. The first porcelain products created in Russia after the discovery of the secret of Russian porcelain were distinguished by their originality and independence, especially in terms of shapes. The manufactory produced candlesticks, smoking pipes, sculptures, and sets.

In 1765, the porcelain manufactory was transformed into the Imperial Porcelain Factory, where they continued to create decorative vases, busts, reliefs, and a series (about one hundred) of porcelain figures depicting the peoples of Russia.

In 1766, Franz Yakovlevich Gardner founded a private enterprise for the production of porcelain near Moscow, in the village of Verbilki, Dmitrovsky district (hence the name “Dmitrov porcelain”). It was to him in 1778 that Catherine 11 entrusted the production of the “order” “St. George service”. At first, the factory repeated Saxon plates and sculptures and even put a Meissen stamp in the form of two crossed swords and sold them to merchants, townspeople and wealthy peasants. At the beginning of the 19th century. The Gardner factory produced brightly painted figures - “Russian types”. In 1892, Gardner's heirs sold the plant to M. S. Kuznetsov.

At the beginning of the 19th century. Dozens of small private factories appeared in Russia. In 1812, a factory of merchant Sergei Batenin opened in St. Petersburg, which until 1839 produced large gilded vases in the Russian Empire style with paintings and stamps with lush bouquets of roses. Similar products were produced at the Popov, Terekhov and Kiselev factories in the Gzhel region from gilded porcelain and were called “bronze goods”.

In 1832, Terenty Yakovlevich Kuznetsov founded a ceramic factory in Likino-Dulyovo near Moscow. By 1889, his grandson Matvey Sidorovich Kuznetsov had concentrated all the largest factories in his hands and organized the M. S. Kuznetsov Partnership. Kuznetsov left the previous factory marks and tried to maintain the familiar appearance of the products, but hand-painting was replaced with decals and they began to combine different styles, manners, techniques and decorative elements. By the end of the 19th century. (“Kuznetsov porcelain”) forms became eclectic, overloaded with polychrome painting and rough color combinations. Hence the contemptuous name “Kuznetsovshchina” as a synonym for “merchant taste” and eclecticism in Russian applied art of the late 19th century.

Since 1870, in Konakovo, Tver province, at a factory also acquired by M. S. Kuznetsov, they began to produce porcelain products with typical “Kuznetsov” painting.

At the end of the 19th - beginning of the 20th centuries. ceramic production went in two main directions: the development of utilitarian household items (this direction was in decline during this period) and the exit from the historical framework (the second new direction created easel paintings in faience, decorative panels and sculptures in majolica). This conflict between mass production and art eventually led to the creation of design, responsible for creating not only a product, a style, but also a living environment. The design of ceramic products has come to the fore, which should reflect both folk traditions and new trends in everyday life and architecture. Ceramic products are used in architecture as construction, facing and decorative materials, in everyday life (dishes, vases), as plastic arts, and souvenirs.

Ceramic production - large factories, small workshops and individual ceramic artists - have at their disposal a large number of different masses for the production of a wide range of ceramic materials, as well as efficient equipment (primarily kilns) and waste developed over the decades of the 20th century. high performance technology.

Today, the following types of ceramics are used for the production of artistic ceramic products: majolica, pottery, terracotta, stone products, earthenware and porcelain. For the manufacture of ceramic products, the main molding methods can be distinguished: slip casting, plastic method, semi-dry method, dry method.

Slip casting and plastic molding on machines can greatly reduce the cost of production, copy and replicate ceramic products in any quantity.

Let us consider in the next chapter the classification of types of ceramics.

Questions and tasks for self-control

• 1. When did the first ceramic products appear?
• 2. What raw material was used to produce ceramic products?
• 3. How were the first ceramic products decorated?
• 4. Name the styles of painting on ancient Greek ceramics.
• 5. What technologies were used to make ceramic products in Kievan Rus in the 8th-12th centuries?
• 6. In which European countries did porcelain begin to be made?
• 7. When did porcelain appear in Russia?
• 8. List the main ceramic production in the 19th century. in Russia.
• 9. What modern ceramic factories are known in Russia?

• Imanov G. M., Kosov V. S., Smirnov G. V. Production of artistic ceramics: textbook. M. : Higher School, 1985; Akunova L.F., Pribluda S. 3. Materials science and technology for the production of artistic ceramic products. M.: Higher School, 1991; Boyko 10. A., Livshits V. B. Materials for artistic products (Ceramics and coatings. Metals and alloys). M.: OntoPrint, 2015; Volkova F.N. General technology of ceramic products. M.: Stroyizdat, 1989; Frantsuzova I.G. General technology for the production of porcelain and earthenware products. M.: Higher School, 1991.

Ceramic are artificial stone materials and products obtained through the technological processing of mineral raw materials and subsequent firing at high temperatures.

The name "ceramics" comes from the Greek word "keramos" - clay.

Therefore, ceramic technology has always meant the production of materials and products from clay raw materials and its mixtures with organic and mineral additives.

The material from which ceramic products are made after firing is called in ceramic technology. ceramic shard.

Clay has always been and is one of the main types of building materials in human history.

In the beginning - 8000 BC. - clays were used in unfired form for adobe construction and the production of adobe and mud bricks. 3500 BC marks the beginning of the use of ceramic bricks, and 1000 BC. - glazed bricks and tiles.

From the middle of the first millennium, the production of porcelain products began in China.

In Russia, the first brick factory was built in Moscow in 1475, and in 1744 the first porcelain factory began operating in St. Petersburg. At the end of the 18th - mid-19th centuries. The rapid development of the metallurgical, chemical and electrical industries has led to the development of the production of fire-resistant, acid-resistant, electrical insulating ceramics and floor tiles

Since the beginning of this century, the production of efficient bricks and hollow stones for the construction of walls and ceilings, as well as ceramic tiles for interior and exterior decoration and sanitary products, has developed.

Recently, the production of special ceramics with unique properties for the needs of nuclear energy, mechanical engineering, electronics, rocket and other industries has become widespread.

Cermets consisting of metal and ceramic parts are of great practical interest.

The concept of ceramic materials and products includes a wide range of materials with different properties.

They are classified according to a number of characteristics:
- according to their intended purpose, ceramic products are divided into the following types: wall, finishing, roofing, floors, floors, road, sanitary, acid-resistant, heat-insulating, fire-resistant and concrete fillers;

Based on their structure, ceramic products are distinguished between porous and sintered (dense) shards. Products with water absorption by weight of more than 5% are considered porous. These include products of both coarse (ceramic wall bricks and stones, products for roofing and ceilings, drainage pipes) and fine (cladding tiles, earthenware) ceramics. Dense products include products with water absorption by weight of less than 5%. These also include products of both coarse (clinker bricks, large-sized facing slabs) and fine (faience, semi-porcelain, porcelain) ceramics;

According to the melting point, ceramic materials and products are divided into low-melting (with a melting point below 1350 °C), refractory (with a melting point of 1350 °C-1580 °C), fire-resistant (1580 °C-2000 °C), high-melting (more than 2000 °C). °C).

The ability to obtain any specified properties, a wide range, large reserves of ubiquitous raw materials, comparative simplicity of technology, high durability and environmental friendliness of ceramic materials ensure that they are one of the first places in terms of importance and production volumes among other building materials.

Thus, the production of ceramic bricks accounts for about half the volume of all wall materials.

2. Raw materials for the production of ceramic materials

The main raw material for the production of building ceramic products is clay raw materials, used in pure form, and more often in a mixture with additives - leaning, rock-forming, flux, plasticizers, etc.

Clay raw materials

Clay raw materials (clays and kaolins)- a product of weathering of igneous feldspathic rocks, containing admixtures of other rocks.

Clay mineral particles with a diameter of 0.005 mm or less provide the ability, when mixed with water, to form a plastic dough that retains its given shape when dried, and after firing it acquires the water resistance and strength of stone.

In addition to clay particles, the raw material contains a certain content of dust particles with grain sizes of 0.005-0.16 mm and sand particles with grain sizes of 0.16-2 mm.

Clay particles have a lamellar shape, between which, when wetted, thin layers of water form, causing the particles to swell and allow them to slide relative to each other without loss of cohesion. Therefore, clay mixed with water produces an easily moldable plastic mass.

When drying, clay dough loses water and decreases in volume. This process is called air shrinkage .

The more clay particles there are in the clay raw material, the higher the plasticity and air shrinkage of the clays. Depending on this, clays are divided into highly plastic, medium plastic, moderately plastic, low plastic and non-plastic.

Highly plastic clays contain up to 80-90% clay particles, a plasticity number of more than 25, water requirement of more than 28% and air shrinkage of 10-15%. Medium and moderately plastic clays contain 30-60% clay particles, a plasticity number of 15-25, water requirement of 20-28% and air shrinkage of 7-10%.

Low plasticity clays contain from 5% to 30% clay particles, water requirement less than 20%, plasticity number 7-15 and air shrinkage 5-7%.

Non-plastic clays do not form a plastic, moldable dough.

Clays with a content of clay particles of more than 60% are called “fat” and are characterized by high shrinkage, to reduce which “leaning” additives are added to the clays.

Clays with a content of clay particles of less than 10-15%* are “lean” clays; fine additives, for example, bentonite clay, are added to them during the production of products.

Different combinations of chemical, mineralogical and granulometric composition of components determine different properties of clay raw materials and their suitability for producing ceramic products of various properties and purposes.

The granulometric composition of clays is closely related to the mineralogical composition.

Sandy and dusty fractions are presented mainly in the form of remains of primary minerals (quartz, feldspar, mica, etc.).

Clay particles mostly consist of secondary minerals: kaolinite, montmorillonite, hydromicas and their mixtures in various combinations.

Clays with a predominant content of kaolinite are light in color, swell slightly when interacting with water, are characterized by refractoriness, low plasticity and little sensitivity to drying.

Clays containing montmorillonite are very plastic, swell strongly, are prone to curling when molded, and are sensitive to drying and firing with the manifestation of curvature of products and cracking.

Highly dispersed clayey rocks with a predominant content of montmorillonite are called bentonites .

Samples with a predominance of hydromica minerals in the clay part are characterized by intermediate indicators of plasticity, shrinkage and sensitivity to drying.

The chemical composition of clays is expressed by the content and ratio of various oxides.

The presence of iron oxides reduces the fire resistance of clays, fine limestone imparts a light color and reduces the fire resistance of clays, and its stone-like inclusions cause the appearance of “dutikon” and cracks in ceramic products

Alkali metal oxides are strong fluxes and contribute to increased shrinkage, compaction of the shard and increase its strength. The presence of soluble salts of sulfates and chlorides of sodium, calcium, magnesium and iron in clay raw materials causes the appearance of white efflorescences on the surface of products.

For the manufacture of certain types of fire-resistant heat-insulating products, clay raw materials from tripoli and diatomite, consisting mainly of amorphous silica, are used, and for the production of lightweight aggregates, perlite, pumice, and vermiculite are used.

Currently, natural clays in their pure form are rarely suitable raw materials for the production of ceramic products. In this regard, they are used with the introduction of additives for various purposes.

Additives to clays

Leaning Supplements. They are introduced into plastic clays to reduce shrinkage during drying and firing and prevent deformations and cracks in products. These include: dehydrated clay, fireclay, slag, ash, quartz sand.

Pore-forming additives. They are introduced to increase the porosity of the shard and improve the thermal insulation properties of ceramic products. These include: sawdust, coal powder, peat dust. These supplements are also fattening.

Plavni. They are introduced to reduce the firing temperature of ceramic products. These include: field stones, iron ore, dolomite, magnesite, talc, sandstone, pegmatite, cullet, perlite.

Plasticizing additives. They are introduced to increase the plasticity of raw material mixtures with less water consumption. These include highly plastic clays, bentonites, and surfactants.

Special additives. To increase the acid resistance of ceramic products, sand mixtures sealed with liquid glass are added to the raw mixtures. To obtain some types of colored ceramics, metal oxides (iron, cobalt, chromium, titanium, etc.) are added to the raw material mixture.

Glazes and engobes

To increase sanitary and hygienic properties, water resistance, and improve appearance, some types of ceramic products are covered with a decorative layer - glaze or engobe.

Glaze- a glassy coating 0.1-0.2 mm thick, applied to the product and fixed by firing. Glazes can be transparent and dull (opaque) of various colors.

To make the glaze, the following are used: quartz sand, kaolin, feldspar, salts of alkali and alkaline earth metals. Raw mixtures are ground into powder and applied to the surface of products in the form of a powder or suspension before firing.

Angobom is a thin layer of white-burning or colored clay applied to a product, forming a colored coating with a matte surface. The properties of the engobe should be close to the main shard.

3. Scheme of production of ceramic products

With all the variety of ceramic products in terms of properties, shapes, purpose, type of raw materials and manufacturing technology, the main stages of the production of ceramic products are common and consist of the following operations: extraction of raw materials, preparation of the mass, molding of products, drying and firing.

Clay is extracted from quarries, usually in open pits using excavators, and transported to a ceramics factory by rail, road or other means of transport.

Quarry development is preceded by preparatory work: geological exploration to establish the nature of occurrence, useful strata and clay reserves; clearing the surface of plants a year or two before the start of development, removing rocks unsuitable for production.

Preparation of clays and molding of products

Quarry clay in its natural state is usually unsuitable for making ceramic products. Therefore, it is processed in order to prepare the mass.

It is advisable to prepare clays using a combination of natural and mechanical processing.

Natural processing involves aging pre-extracted clay for 1-2 years with periodic wetting by precipitation or artificial soaking and periodic freezing and thawing.

Mechanical processing of clays is carried out for the purpose of further destruction of their natural structure, removal or grinding of large inclusions, removal of harmful impurities, grinding of clays and additives and mixing of all components until a homogeneous and workable mass is obtained using specialized machines (clay rippers; destoners, perforators, disintegrators, rough and fine grinding rollers; runners, clay grinding machines, basket disintegrators, rotary and ball mills, single- and double-shaft clay mixers, propeller mixers, etc.).

Depending on the type of product being manufactured, the type and properties of the raw material, the mass is prepared using plastic, hard, semi-dry, dry and slip methods. The method of preparing the mass determines both the method of molding and the name of the production method as a whole.

With the plastic method of mass preparation and molding, the starting materials with natural humidity or pre-dried are mixed with water additives to obtain a dough with a moisture content of 18 to 28%.

This method of producing ceramic building materials is the simplest, least metal-intensive and therefore most widespread.

It is used in cases of using medium-plastic and moderately plastic, loose and wet clays with a moderate content of foreign inclusions, which soak well and turn into a homogeneous mass.

Technology system production of ceramic bricks:

1 - clay quarry; 2 - excavator; 3 - clay reserve; 4 - trolley; 5 - box feeder; 6 - additives; 7 - runners; 8 - rollers; 9 - belt press; 10 - cutter; 11 - stacker; 12 - trolley; 13 - drying chambers; 14 - tunnel oven; 15 - self-propelled trolley; 16 - warehouse

The set and types of machines for mass preparation may differ from those shown in Fig. 1, depending on the properties of the raw materials and additives.

However, molding using the plastic method is always carried out on a machine of the same operating principle - a belt screw press with or without vacuuming and heating.

Vacuuming and heating the mass during pressing makes it possible to improve its molding properties and increase the strength of the fired product up to 2 times.

A screw-shaft with screw blades rotates in the press body. The clay mass is moved by a screw to a tapering transition head, compacted and extruded through a mouthpiece in the form of a continuous bar or tape, or pipe under a pressure of 1.6-7 MPa.

Belt Vacuum Press:

1 - screw shaft; 2 - press head; 3 - mouthpiece; 4 - clay beam; 5 - impeller; 6 - vacuum chamber; 7 - grate; 8 - clay grinder

The productivity of modern belt presses for brick production reaches 10,000 pieces per hour.

Hard The molding method is a type of modern development of the plastic method.

The humidity of the molded mass using this method ranges from 13% to 18%. Molding is carried out on powerful vacuum screw or hydraulic presses. The vacuum press of the Italian company Bongeni, for example, creates a pressing pressure of up to 20 MPa.

Due to the fact that “rigid” molding is carried out at relatively high pressures of 10-20 MPa, less plastic clays with natural low moisture content can be used.

This method requires lower energy costs for drying, and the production of a raw product with increased strength allows one to avoid some operations in the production technology that are required with the plastic method.

Molding using plastic and rigid methods is completed by cutting a continuous strip of molded mass into individual products using cutting devices.

These molding methods are most common in the production of: solid and hollow bricks, stones, blocks and panels; tiles, etc.

Semi-dryway production of building ceramic products is less common than the plastic molding method. Ceramic products using this method are formed from a charge with a moisture content of 8-12% at pressures of 15-40 MPa.

The disadvantage of this method is that its metal consumption is almost 3 times higher than that of plastic.

But at the same time it also has advantages.

The duration of the production cycle is reduced by almost 2 times; products have a more regular shape and more accurate dimensions; fuel consumption is reduced by up to 30%; in production, low-plasticity lean clays can be used with a large amount of production waste additives - ash, slag, etc.

The raw material mass is a powder, which should have about 50% particles less than 1 mm and 50% 1-3 mm in size.

Products are pressed into molds into one or more individual products using hydraulic or mechanical presses. This method is used to make all types of products that are also made using the plastic method.

Dryway is a type of modern development of semi-dry production of ceramic products. Press powder with this method is prepared with a moisture content of 2-6%.

This completely eliminates the need for a drying operation. In this way, dense ceramic products such as floor tiles, road bricks, earthenware and porcelain materials are produced.

Slipway It is used when products are made from a multicomponent mass consisting of heterogeneous and difficult-to-sinter clays and additives, and when it is necessary to prepare the mass for the manufacture of complex-shaped ceramic products by casting.

Products are cast from a mass containing up to 40% water. This method is used to produce sanitary products and facing tiles.

Drying products

Before firing, products must be dried to a moisture content of 5-6% to avoid uneven shrinkage, distortion and cracking during firing.

Previously, raw materials were dried mainly under natural conditions in drying sheds for 2-3 weeks, depending on climatic conditions.

Currently, drying is carried out mainly artificially in continuous tunnel or periodic chamber dryers for from several to 72 hours, depending on the properties of the raw material and the moisture content of the raw material.

Drying is carried out at an initial temperature of the coolant - exhaust gases from kilns or heated air -120-150 ° C.

Firing of products

Burning- the most important and final process in the production of ceramic products. This process can be divided into three periods: heating of the raw material, firing itself and controlled cooling.

When the raw material is heated to 120 °C, physically bound water is removed and the ceramic mass becomes non-plastic. But if you add water, the plastic properties of the mass are preserved.

In the temperature range from 450 °C to 600 °C, chemically bound water is separated, clay minerals are destroyed, and the clay becomes an amorphous state.

At the same time, and with a further increase in temperature, organic impurities and additives burn out, and the ceramic mass irreversibly loses its plastic properties.

At 800 °C, the strength of products begins to increase due to the occurrence of reactions in the solid phase at the boundaries of the surfaces of the component particles.

In the process of heating to 1000 °C, the formation of new crystalline silicates, for example sillimanite, is possible, and when heated to 1200 °C, mullite is formed.

At the same time, low-melting compounds of the ceramic mass and flux minerals create a certain amount of melt, which envelops the unmelted particles, tightens them, leading to compaction and shrinkage of the mass as a whole.

This shrinkage is called fire shrinkage.

Depending on the type of clay, it ranges from 2% to 8%. After cooling, the product acquires a stone-like state, water resistance and strength. The property of clays to compact during firing and form a stone-like shard is calledsinterability of clays.

Depending on the purpose, the products are fired to varying degrees of sintering. A shard with a water absorption of less than 5% is considered sintered. Most building products are fired to produce a shard with incomplete sintering in a certain temperature range from the refractory temperature to the start of sintering, calledsintering interval .

Sintering interval for low-melting clays it is 50-100 °C, and for refractory clays up to 400 °C. The wider the sintering interval, the less the risk of deformation and cracking of products during firing.

The firing temperature range ranges from 900 °C to 1100 °C for brick, stone, expanded clay; from 1100 °C to 1300 °C for clinker bricks, floor tiles, pottery, earthenware; from 1300 °C to 1450 °C for porcelain products; from 1300 °C to 1800 °C for refractory ceramics.

4. Structure and properties of ceramic products

Ceramic materials are composite materials in which the matrix or continuous phase is represented by a cooled melt, and the dispersed phase is represented by unmelted particles of clay, dust and sand fractions, as well as pores and voids filled with air.

The matrix material, in turn, is a microcomposite material consisting of a matrix - a continuous glassy phase of a solidified melt and a dispersed phase - crystalline grains of sillimanite, mullite, silica of various fractions and other substances that crystallize upon cooling (mainly aluminosilicates).

The glassy, ​​amorphous phase (supercooled liquid) is represented in the microstructure by low-melting components that did not have time to crystallize at a given melt cooling rate.

The true density of ceramic materials is 2.5 - 2.7 g/cm; density 2000 - 2300 kg/m; the thermal conductivity of an absolutely dense shard is 1.16 V/(m °C). The heat capacity of ceramic materials is 0.75 - 0.92 kJ/(kg °C).

The compressive strength of ceramic products varies from 0.05 to 1000 MPa.

Water absorption of ceramic materials, depending on porosity, varies from 0 to 70%.

Ceramic materials have frost resistance grades: 15; 25; 35; 50; 75 and 100.

5. Wall products

The group of wall products includes: ordinary ceramic brick, effective ceramic materials (hollow brick, porous-hollow brick, lightweight brick, hollow stones, blocks and slabs), as well as large-sized blocks and panels made of brick and ceramic stones.

Ceramic bricks and stones

Ceramic bricks and stones are made from fusible clays with or without additives and are used for laying external and internal walls and other elements of buildings and structures, as well as for the manufacture of wall panels and blocks.

Depending on their size, bricks and stones are divided into types:
- ordinary;
- thickened;
- modular;
- ordinary stone;
- enlarged;
- modular;
- with horizontal arrangement of voids.

Types of ceramic bricks and stones

Brick: a) ordinary; b) thickened; c) modular. Stone: d) ordinary; e) enlarged; e) modular; g), h) with horizontal arrangement of voids

Brick can be solid or hollow, but stones can only be hollow. Thickened and modular bricks should also only have round or slotted voids so that the weight of one brick does not exceed 4 kg.

The surface of the edges can be smooth or corrugated.

Brick and stone must be properly fired, since underburned (scarlet color) has insufficient strength, low water resistance and frost resistance, and overburned brick (iron ore) is characterized by increased density, thermal conductivity and, as a rule, has a distorted shape.

It is allowed to produce bricks and stones with rounded corners with a radius of up to 15 mm. The size of cylindrical through voids along the smallest diameter must be at least 16 mm, the width of slot voids no more than 12 mm. The diameter of blind voids is not limited.

The thickness of the outer walls of bricks and stones must be at least 12 mm. In appearance, brick and stone must meet certain requirements.

This is established by inspecting and measuring a certain amount of brick from each batch (0.5%, but not less than 100 pcs.) for deviations from the established dimensions, non-straightness of edges and edges, broken corners and edges, and the presence of through cracks running along the bed of the brick.

The total number of products with deviations higher than acceptable should be no more than 5%.

Brick grade depending on compressive and bending strength

Frost resistance of bricks and stones is 15, 25, 35 and 50. Water absorption for solid bricks should be at least 8% for grades up to 150, and at least 6% for solid bricks of higher grades and hollow products.

Based on dry density, bricks and stones are divided into 3 groups:
- ordinary - with a density of more than 1600 kg/m;
- conditionally effective - with a density of more than 1400-1600 kg/m;
- effective - with a density of no more than 1400-1450 kg/m.

Effective wall materials also include porous solid and hollow bricks and stones made from diatomites and tripoli and having a density: class A - 700-1000 kg/m, class B - 1001-1300 kg/m, class B > 1301 kg/m .

The use of effective ceramic wall materials makes it possible to reduce the thickness of external walls, reduce the material consumption of enclosing structures by up to 40%, and reduce transportation costs and loads on the foundation.

Different countries produce wall materials that differ from each other, both in nomenclature and in standard sizes and brands. Thus, the grade of brick produced abroad is 125-600, and the bulk of bricks are produced with grade 400

In Germany, for example, the “Wall Brick” standard provides for the production of: ordinary solid and hollow bricks and stones of 14 types with dimensions 240x115x52-490x300x238 grades from M40 to M280 and a density of 1200-2200 kg/m(3); light hollow bricks and stones of 13 standard sizes, grades from M20 to M280 and a density of 600-1000 kg/m (3); high-strength bricks and stones of the M360, M480 and M600 brands: for internal walls and partitions - hollow bricks, stones and slabs with dimensions 330x175x40-945x320x115.

In foreign practice, it is known to produce tongue-and-groove bricks for mortarless masonry, large-size ceramic wall elements, soundproofing bricks and other wall products.

Wall panels and blocks made of bricks and ceramic stones

Wall panels and blocks made of bricks and ceramic stones are made to increase the industrial nature of construction.

They are usually made in a horizontal position in a metal mold with a matrix that has cells for fixing the position of each brick and stone and providing jointing on the front side of the product or with a matrix with a special pattern of the finishing layer.

They are manufactured in three-, two-, and single-layer lengths for one or two planning steps and a height of 1 and 2 floors, the thickness of the panels for internal walls and partitions is 80, 140, 180 and 280 mm.

Single-layer panels are made of ceramic stones. A two-layer panel consists of one layer of 1/2 brick and a layer of insulation up to 100 mm thick.

The three-layer panel consists of two outer brick layers, each 65 mm thick, with a 100 mm thick insulation layer between them. To ensure the strength of the panels during transportation and installation, they are reinforced with steel wire frames around the perimeter of the panel and openings.

6. Cladding products

Ceramic cladding products are used for external and internal cladding of buildings and structures not only for the purpose of decorative and artistic finishing, but also to increase their durability.

Ceramic products for external cladding of buildings

Ceramic products for external cladding of buildings are divided into face bricks and stones, large-size slabs, ceramic facade tiles and carpets made from them.

Brick and facing stones are not only facing products. They are laid together with the wall masonry and at the same time serve as a structural load-bearing element along with ordinary bricks.

Face bricks and stones are produced in the same sizes and shapes as regular ones, and differ from the latter in their higher density and uniformity of color. Produced in strength grades 75, 100, 125 and 150, and frost resistance of at least 25

By adjusting the composition of the raw material and the firing mode, colors range from white, cream to light red and brown.

In the absence of high-quality raw materials, they are manufactured with a textured front surface: engobing, two-layer molding, glazing and shotcrete with colored mineral chips.

Two-layer products are made by molding from two masses: the main part - local red-burning clays and the front layer 3-5 mm thick from light-burning colored or unpainted clays.

Relief texture is also used, which is produced by processing still wet raw materials with special metal brushes, combs, and grooved rollers. For buildings constructed of brick, facing bricks are the most economical type of building cladding.

Large-sized plink-type ceramic facing slabs for universal use are available glazed and unglazed with a smooth, rough or grooved, single- or multi-color surface.

The slabs have water absorption of less than 1% and frost resistance of 50 cycles or more. They are manufactured in square or rectangular shapes with a length of 490, 990, 1190 mm, a width of 490 and 990 mm and a thickness of 9-10 mm.

They are used for cladding facades and plinths of buildings, underground passages.

Ceramic facade tiles and carpets made from them are produced by plastic and semi-dry pressing.

They are used for cladding external walls of brick buildings, external surfaces of reinforced concrete wall panels, plinths, underground passages and decoration of other building elements.

Tiles are produced glazed and unglazed, ordinary and special purpose with a smooth and embossed surface of 26 types with dimensions from 292x192x9 mm to 21x21x4 mm

The standard allows the production of tiles and other standard sizes. Water absorption of ordinary tiles is 7-10%, and special ones - no more than 5%.

Frost resistance should be at least 35 cycles for ordinary tiles, and at least 50 cycles for special ones.

Tiles can be supplied in carpets. Factories produce carpets with tiles glued with their front side on kraft paper.

Ceramic tiles for interior cladding

Ceramic tiles for interior cladding are divided into two groups - for wall cladding and for floor covering. These products are not exposed to negative temperatures under operating conditions, so frost resistance requirements are not imposed on them.

Tiles for wall cladding are used in two types -majolica And earthenware. Earthenware tiles are made from a raw mixture of kaolin, feldspar and quartz sand, and majolica tiles are made from red-burning clays, followed by glaze coating.

Tiles classify: by the nature of the surface - flat, relief-ornamented, textured; by type of glaze coating - transparent and dull, shiny and matte, single-color and decorated with multi-color designs.

According to the shape, purpose and nature of the edges, tiles are produced in the following types: square, rectangular, shaped corner, shaped cornice straight, for finishing external and internal corners; shaped plinths - straight, for finishing external and internal corners.

Types of ceramic tiles for interior decoration:

1-5 - square; 6-10 - rectangular; 11, 12 - shaped corner; 13-16 - shaped cornices; 17-20 - shaped plinths

The dimensions of the tiles for interior decoration are (150200) x (50200) x (58) mm.

Water absorption of tiles for interior decoration is up to 16%, bending strength is 12 MPa.

Tiles must withstand temperature changes from 125±5 °C to 15-20 °C without the appearance of defects.

Ceramic tiles for floors - Metlakh (n The name comes from the city of Mettlach in Germany, where their production was established in the Middle Ages)made from refractory and refractory clays with and without additives

They are used for laying floors in buildings where high demands are placed on cleanliness, where there may be exposure to fats and other chemicals, heavy traffic, and also in cases where the flooring material also serves as a decorative element in the architectural design of the room.

During production, the tiles are fired before sintering, as a result of which they have a water absorption of no more than 4% and high wear resistance.

Tiles can be square, rectangular, four-, five-, six- and octagonal.

Dimensions of tiles of 16 types (2004) x (17349) x (1013) mm.

Depending on the type of front surface, the tiles are produced smooth, with relief and embossing: single-color and multi-color, matte and glazed, with and without patterns.

Large-sized universal ceramic tiles with dimensions of (1200500)x500 mm are also produced, which are used for cladding walls and floors.

Types of ceramic floor tiles:

1 - square; 2 - rectangular; 3 - triangular; 4 - hexagonal; 5 - tetrahedral; 6 - pentagonal; 7 - hexagonal; 8, 9 - curly

For flooring, mosaic tiles of square or rectangular shapes measuring 23 and 48 mm with a thickness of 6-8 mm, assembled into “carpets” on kraft paper measuring 398x598 mm, are also used.

The world leader in the production of ceramic tiles is Italy, which produces about 30% of world production.

7. Ceramic products for roofing and ceilings

The greatest use of ceramic products for roofing and tiles is found in Western European countries, in some of them the roofing of up to 100% of residential buildings is achieved through the use of tiles.

Tiles, having a durability of up to 300 years, significantly exceed any other roofing materials in terms of this indicator, and are not inferior to them in textural qualities and cost.

The disadvantages of tiles include the need for a large slope (at least 30%) of the roof and the significant weight of the roof, which requires special structural strength of the rafters, and the high labor intensity of roofing work.

However, high durability, fire resistance, weather resistance and abundant raw materials make ceramic tiles one of the most effective roofing materials.

There are different types of tiles known. According to their intended purpose, tiles are divided into: ordinary, ridge, gutter, end tiles for closing rows and special-purpose tiles. The tiles are made from low-melting clays.

Types of ceramic tiles:

a) groove stamped; b) grooved tape; c) flat tape; d) ridge; e) Dutch; e) grooved; g) Tatar

During installation, the tiles are stacked on top of each other and therefore the useful area is, respectively, for flat tiles - 50%, for stamped and grooved tiles - 75-85%.

When tested, the tiles must withstand at least 70 kg with a distance between supports of 180 mm for flat tiles and 300 mm for grooved and stamped tiles. The weight of stamped and strip grooves laid in the roof and saturated with water should be no more than 50 kg/m, and flat - no more than 65 kg/m.

Frost resistance of tiles must be at least 25 cycles.

Stones and slabs for floors

Floors made of hollow stones and slabs are fire-resistant, durable, and have good heat and sound insulation properties.

Their installation requires little consumption of cement and steel and does not require additional backfill.

Ceramic stones for floors are divided according to their intended purpose for: prefabricated decking elements, frequently ribbed prefabricated or monolithic floors, roll-ups (filling between beams). The hollowness of ceramic stones for floors is 50-75%.

Ceramic stones for floors:

a) load-bearing; b) non-load-bearing

8. Sanitary ceramics and pipes

Sanitary ceramic products- washbasins, toilets, cisterns, bidets, urinals, sinks and other similar products are made from porcelain, semi-porcelain, earthenware and fireclay masses, which are obtained from the same materials.

Typical compositions of masses for the production of sanitary products (% by weight)

Physical and mechanical properties of sanitary ceramics

Ceramic sewer pipes are used for the construction of non-pressure sewer networks transporting industrial, domestic, rain, aggressive and non-aggressive waters.

Pipes are made from plastic, refractory and refractory clays, cylindrical in shape, 1000-1500 mm long with an internal diameter of 150-600 mm.

At one end there is a socket for connecting individual sections of the pipeline.

The water absorption of pipes should be no more than 8%, and the acid resistance should not be lower than 93%.

Pipes must be waterproof and withstand internal pressure of at least 0.15 MPa.

Ceramic drainage pipes are made from clay with or without additives and are used in land reclamation construction to install closed drainage with joints protected by filter materials.

Pipes are produced with a cylindrical, hexagonal and octagonal surface with an internal diameter of 50-250 mm and a length of 333 mm.

Their frost resistance is at least 15 cycles, and the destructive external load is from 3.5 to 5.0 kN, depending on the diameter.

The outer surface of the pipes is covered with glaze. Water enters the pipes through round or slot-shaped holes in the joints, as well as through pipe joints.

9. Special ceramic products

Specialty ceramic products include chimney bricks, clinker bricks and acid-resistant products.

Bricks for chimneys used for laying chimneys and lining industrial pipes if the temperature of their heating by flue gases does not exceed 700 °C.

Brick is produced in grades from 125 to 300.

Brick sizes: length 120 and 250 mm, width 120 or 250 mm, thickness 65 or 88 mm.

Brick can be rectangular or wedge-shaped.

The shorter lengths of wedge-shaped bricks are 70, 100, 200 and 225 mm. The water absorption of the brick must be at least 6%, and frost resistance 25, 35 and 50.

Clinker brick It is obtained by firing clays until completely sintered, but without vitrifying the surface, so it differs from ordinary ones in its high strength and frost resistance.

Brick size 220x110x65 mm.

In accordance with the ultimate compressive strength, it is divided into 3 grades - 1000, 700 and 400, the frost resistance of which is, respectively, 100-50 cycles, and the water absorption is, respectively, no more than 2-6%.

Clinker brick is also called road brick and is used to cover roads and pavements, lining sewer collectors and lining embankments.

It is also used in the chemical industry as an acid-resistant material.

Acid-resistant bricks are used to protect equipment and building structures operating in acidic aggressive environments, and for lining chimneys that serve to remove flue gases containing aggressive environments.

Bricks are produced of the highest and first category of quality in three classes A, B and C and in four shapes: straight, wedge (end and edge), radial (transverse and longitudinal) and shaped (tear-shaped).

Brick sizes 230x113x65 and 230x113x55 mm.

The properties of bricks have the following meanings: acid resistance - (98.5-96)%; compressive strength (60-35) MPa; thermal resistance (5-25) thermal shifts.

Acid-resistant tiles are used for lining equipment and protecting building structures and structures operated in conditions of exposure to aggressive environments.

Tiles are produced of the highest and first grades of 6 brands: acid-resistant porcelain - KF, thermal acid-resistant dunite - TKD, thermal acid-resistant for the hydrolysis industry - TKG, acid-resistant for building structures - KS, acid-resistant fireclay - KSh and thermal acid-resistant fireclay - TKSh.

The shape of the tiles is:
- square flat;
- square radial;
- rectangular;
- wedges;
- paired.

On one side, the tiles have a ribbed surface, which provides better adhesion to the lined structure.

The sizes of the tiles vary within the following range: length and width 50-200 mm, thickness 15-50 mm.

The properties of tiles, depending on the type and brand, range from: water absorption - (0.4-8)%; acid resistance - (97-99)%; compressive strength - (10-150) MPa, and bending strength - (10-40) MPa; thermal resistance 2-10 thermal cycles; frost resistance - 15-20 cycles.

Clay is considered the basis for pottery making. Mixed with water, it creates a dough-like mass suitable for subsequent processing. Raw materials of natural origin differ depending on the place of formation. One type can be used in its pure form, others require sifting and mixing. The result is clay for ceramics - a material quite suitable for making various products.

Structurally, clay consists of small crystals that form the clay-forming silicate mineral - kaolinite. Clay for ceramics contains water, silicon and aluminum oxides.

Red clay

In nature, such pottery clay is characterized by a greenish-brown tint imparted by iron oxide, which accounts for five to eight percent of the total. In progress heat treatment Depending on the temperature or type of oven, the clay becomes red or whitish. The material kneads easily and can withstand heating up to 1,100 degrees. The raw material is highly elastic, excellent for modeling small sculptures or for working with clay plates.

White ceramics

Deposits of this type are found everywhere. When sufficiently moistened, the clay is light gray; the process of pressing gives it a white or ivory tint. The main qualities of the material are elasticity and translucency, since the composition does not contain iron oxide. Used for making dishes, tiles, plumbing fixtures, and clay crafts.

A type of raw material containing an increased amount of white alumina is majolica. It is burned at low temperatures, after which the surface is covered with a glaze containing tin. Majolica ceramics has a second name - earthenware, since for the first time this material was used for the manufacture of tableware at a factory for the production of earthenware products.

Sandstone clay

This material is especially suitable for working on a special machine for making pottery. The composition contains loam and silica impurities. The second name for the raw material is “pot clay”. After firing at temperatures exceeding 1,000 degrees, the clay becomes denser and completely impenetrable. It is used for the production of dishes and decorative crafts. Color shades are varied - grayish, beige, ivory, brown.

Clay for porcelain production

This clay contains kaolin, feldspar and quartz. With sufficient moisture, the clay has a light gray tint; firing at a temperature of 1,300 - 1,400 degrees makes it white. The raw material is elastic; working with such material involves high technical costs, for this reason it is recommended to use ready-made molds.

Fire-clay

This type of clay has the most valuable qualities. This rock is obtained by firing kaolin (white clay) under the influence of a temperature of at least 1,000 degrees. Heat treatment gives the material additional heat resistance. The heat treatment process evaporates liquid and various impurities from the clay material. In a special kiln, the clay rock is given the strength properties of stone, which is then crushed to produce fireclay. The raw materials are used in the production of refractory bricks, for laying stoves and decorative elements.

Criteria for choosing a clay composition for work

When choosing ceramic clay suitable for work, you need to take into account a large number of factors:

• what method of work you will use and what you ultimately want to get - a sculpture, a decorative piece or a functional item. If you plan to work on a potter's wheel or hand sculpt, you should choose the pottery look;
• determine what shade you need. The color of the material depends on its constituent components. When choosing the appropriate option, it is recommended to check the probes for the temperature conditions at which firing is planned, since the shade of the clay may change after heat treatment. To make the right choice, you need to plan the decoration of the product in advance;
• Before choosing the type of clay for ceramics, you should decide what temperature you will set during firing. There are materials that cannot withstand temperatures of more than 1,000 degrees and begin to melt. It follows that you need to select a mass that can be fired in your oven.

Before you find the best option, you will have to try a large number of types of clays from different manufacturers. An experienced master prefers to work with several types designed for various tasks. Some experienced professionals create suitable clay with their own hands or improve ready-made raw materials.

Stages of preparing clay for work

In order for clay to become suitable for making ceramics, it must go through several stages of preparation.

Screening

To do this, the clay must be spread out in small lumps on a wooden flooring and dried in the sun. In winter, the material dries well in the cold if you spread it under a canopy and prevent snow from getting in. Preparing clay in small quantities can be done in a warm room near a stove or radiators. The peculiarity of fast drying is that the clay must be divided into small pieces.

The dried raw materials are poured into a wooden box with thick walls and broken with a tamper. The resulting dust is sifted through a sieve, removing pebbles, chips, blades of grass and large grains of sand.

For modeling, the powder is mixed according to the principle of preparing bread dough, water is added in small portions, and the mass is thoroughly kneaded. Some of the clay powder is kept in a dry state if it is necessary to add thickness to the mass, and there is no time for drying or evaporation. In this case, the powder is added to the clay mass, and the kneading is repeated.

Exhaustion

At this stage, the clay is cleaned, it acquires plasticity and fat content. Low plasticity clay raw materials containing large amounts of sand are most often subjected to this procedure. To soak, you will need a tall container, for example a bucket.

Part of the clay is filled with three parts of water and left overnight. In the morning, the contents are thoroughly stirred to form a homogeneous solution, which is left until completely settled. When the water becomes clear from above, it is carefully drained using a hose.

For such a procedure there is a more convenient method, invented by ancient masters. To do this, use a wooden tub, in which there are holes at a certain level, previously closed with plugs.

When settling a clay solution, first of all the pebbles and heavy grains of sand contained in its composition reach the bottom, then the clay begins to settle. The clarified water is gradually drained through the holes, removing the plugs from them one by one until all the liquid has drained.

To speed up the settling process, add Epsom salt (a pinch per bucket) to the clay solution.

After the water has been drained, the liquid clay is scooped out, being careful not to touch the lower layer of sediment. The solution is poured into a basin or wide box and placed in the sun so that the moisture quickly evaporates from it. When the clay begins to dry out, it is recommended to stir it periodically with a wooden spatula. The material, which has become like a thick dough and does not stick to your hands, is covered with polyethylene and stored until use.

Interruption

The procedure is used before sculpting to remove air bubbles from the clay and improve uniformity. Kneading is considered indispensable when the clay is poorly cleaned at the initial stages and contains small impurities.

Processing begins with the process of rolling the kolobok, which is then thrown forcefully onto the workbench. The workpiece is slightly flattened and takes the shape of a loaf. Using a pottery string, it is cut into two parts, the upper half is again thrown onto the table with a cut, and the second part is done in the same way, without turning it over. The glued halves are cut again, and the throwing procedure is repeated.

The void areas are sharply destroyed and air bubbles are pushed out. The state of homogeneity of the raw material depends on the number of cuts. For this processing, you can use a carpenter's plane or a large knife.

Next, the clay lump is compacted, pressed against the surface of the table, and thin plates are cut from it. All foreign matter that falls under the blade is thrown aside. In this procedure, the purity of the material and its uniformity depend on the thinness of the plates. Having finished planing, the clay plates are again collected into a single lump and compacted to a monolithic state. The layering process is repeated again.

Peremin

This is the final process of preparing your own clay for pottery making. Take a lump, roll it into a roller, bend it and knead it to its original state. Mining operations are repeated several times in the specified sequence. If the material is very dry, before the next kneading it is generously sprayed with water.

Storage Features

The qualitative condition of the material is determined by the conditions of its preservation. The highest demands are placed on the quality of clay, which is intended for the manufacture of artistic ceramic products.

Raw materials arriving at the warehouse are packed into bags and placed on high pallets; the height of the stacks should not exceed two meters. Such installation conditions are necessary to prevent contamination of the raw materials. Each type of clay and incoming batches of material must be stored separately to prevent mixing.

If it is not possible to store clay indoors, it is stored on concrete platforms.

If all requirements for storing and preparing clay raw materials for work are met, you can obtain an excellent material for the manufacture of ceramic products.

Ceramic materials are obtained from clay masses by molding and subsequent firing. In this case, an intermediate technological operation often takes place - drying of freshly molded products, called “raw”.

Based on the nature of the structure of the shard, ceramic materials are distinguished between porous (unsintered) and dense (sintered). Porous ones absorb more than 5% of water (by weight), on average their water absorption is 8...20% by weight. Brick, blocks, stones, tiles, drainage pipes, etc. have a porous structure; dense - floor tiles, sewer pipes, sanitary products.

Based on their intended purpose, ceramic materials and products are divided into the following types: wall - ordinary brick, hollow and porous bricks and stones, large blocks and panels made of brick and stones; For floors - hollow stones, beams and panels made of hollow stones; For external cladding - ceramic facing bricks and stones, carpet ceramics, ceramic facade tiles; For internal lining Andbuilding equipment - slabs and tiles for walls and floors, sanitary products; roofing -tiles; pipes - drainage and sewerage.

Raw materials

The raw materials for the manufacture of ceramic materials are various clay rocks. To improve the technological properties of clays, as well as to give products certain and higher physical and mechanical properties, quartz sand, fireclay (crushed refractory or refractory clay fired at a temperature of 1000...14000°C), slag, sawdust, coal dust are added to the clays. .

Clay materials were formed by the weathering of igneous feldspathic rocks. The process of rock weathering consists of mechanical destruction and chemical decomposition. Mechanical failure occurs as a result of exposure to variable temperature and water. Chemical decomposition occurs, for example, when feldspar is exposed to water and carbon dioxide, resulting in the formation of the mineral kaolinite.

Clay is the name given to earthy mineral masses or clastic rocks that are capable of forming a plastic dough with water, which, when dried, retains its given shape, and after firing, acquires the hardness of stone. The purest clays consist predominantly of kaolinite and are called kaolins. The composition of clays includes various oxides (AI2O3, SiO 2, Fe 2 O3, CaO, Na 2 O, MgO and K2O), free and chemically bound water and organic impurities.

Impurities have a great influence on the properties of clay. Thus, with an increased content of SiO 2 not associated with Al 2 Oz, the binding capacity of clays in clay minerals decreases, the porosity of fired products increases and their strength decreases. Iron compounds, being strong fluxes, reduce the fire resistance of clay. Calcium carbonate reduces refractoriness and sintering interval, increases firing shrinkage and porosity, which reduces strength and frost resistance. Oxides Na2O and K2O lower the sintering temperature of clay.

Clays are characterized by plasticity, cohesiveness and binding ability, and attitude to drying And to high temperatures.

The plasticity of clay is its property of forming a dough when mixed with water, which, under the influence of external forces, is able to take a given shape without the formation of tears and cracks and retain this shape during subsequent drying and firing.

The plasticity of clay is characterized by the plasticity number

P =W T - W R ,

Where W t and W p - moisture values ​​corresponding to the yield strength and rolling limit of the clay rope, %.

According to plasticity, clays are divided into highly plastic (P>25), medium plastic (P = 15...25), moderately plastic (P = 7... 15), low-plasticity (P <7) and non-plastic. For the production of ceramic products, moderately plastic clays with a plasticity number P = 7... 15 are usually used. Low plasticity clays are difficult to mold, while highly plastic clays crack during drying and require thinning.

In the production of firing materials, along with With The clays used are diatomites, tripoli, shale, etc. Thus, in the production of light bricks and products, diatomite and tripoli are used, and intumescent clays, perlite, and vermiculite are used to produce porous aggregates.

Many ceramic factories do not have raw materials suitable in their natural form for the manufacture of corresponding products. Such raw materials require the introduction of additives. Thus, by adding thinning additives up to 6...10% (sand, slag, fireclay, etc.) to plastic clays, it is possible to reduce the shrinkage of clay during drying and firing. Fractions smaller than 0.001 mm have a great influence on the binding ability of clays and their shrinkage.

The higher the content of clay particles, the higher the plasticity. Plasticity can be increased by adding highly plastic clays, as well as by introducing surfactants - sulfite-yeast mash (SYB), etc. Plasticity can be reduced by adding non-plastic materials called slag agents - quartz sand, fireclay, slag, sawdust, coal chips.

Clays containing an increased amount of clay fractions have higher cohesion, and, conversely, clays with a low content of clay particles have low cohesion. With an increase in the content of sand and dust fractions, the binding capacity of clay decreases. This property of clay is of great importance when molding products. The binding ability of clay is characterized by the ability to bind particles of non-plastic materials (sand, fireclay, etc.) and form a sufficiently strong product of a given shape upon drying.

Shrinkage is the reduction in linear dimensions and volume during drying of a sample (air shrinkage) and firing (fire shrinkage). Air shrinkage occurs when water evaporates from the raw material during its drying process. For various clays, linear air shrinkage ranges from 2...3 to 10...12%, depending on the content of fine fractions. Fire shrinkage occurs due to the fact that during the firing process, the low-melting components of the clay melt and the clay particles at the points of their contact come closer together. Fire shrinkage, depending on the composition of the clays, can be 2...8%. Complete shrinkage equal to the algebraic sum of air and fire shrinkage, it ranges from 5...18%. This property of clays is taken into account when manufacturing products of the required sizes.

A characteristic property of clays is their ability to turn into a stone-like mass when fired. In the initial period of temperature increase, mechanically mixed water begins to evaporate, then organic impurities burn out, and when heated to 550...800 ° C, dehydration of clay minerals occurs and the clay loses its plasticity.

With a further increase in temperature, firing occurs - some low-melting component of the clay begins to melt, which, spreading, envelops the unfused clay particles, and upon cooling hardens and cements them. This is how the process of turning clay into a stone-like state occurs. Partial melting of the clay and the action of surface tension forces of the molten mass cause its particles to approach each other, and a reduction in volume occurs - fire shrinkage.

The combination of processes of shrinkage, compaction and hardening of clay during firing is called clay sintering. With a further increase in temperature, the mass softens - melting of the clay occurs.

The color of fired clay is influenced mainly by the content of iron oxides, which color ceramic products red when there is an excess of oxygen in the kiln, or dark brown and even black when there is a lack of oxygen. Titanium oxides cause a bluish coloration of the shard. To obtain white brick, firing is carried out in a reducing environment (in the presence of free CO and III in gases) and at certain temperatures in order to convert iron oxide V nitrous.

Processes that occur during firing and drying of clays

ceramic products production diagram

Despite the extensive range of ceramic products, the variety of their shapes, physical and mechanical properties and types of raw materials, the main stages of the production of ceramic products are general and consist of the following operations: extraction of raw materials, preparation of the raw material, molding of products (raw materials), drying of raw materials, firing of products, processing of products (trimming, glazing, etc.) and packaging.

Raw materials are extracted in open-pit mines using excavators. Transportation of raw materials from the quarry to the plant is carried out by dump trucks, trolleys or conveyors at a short distance from the quarry to the molding shop. Plants for the production of ceramic materials are usually built near a clay deposit, and the quarry is an integral part of the plant.

The preparation of raw materials consists of destroying the natural structure of the clay, removing or grinding large inclusions, mixing the clay with additives and moistening until a moldable clay mass is obtained.

The molding of the ceramic mass, depending on the properties of the initial raw material and the type of product being manufactured, is carried out using semi-dry, plastic and slip (wet) methods. At semi-dry method In production, clay is first crushed and dried, then crushed and with a moisture content of 8...12%, it is fed for molding. At plastically During molding, the clay is crushed, then sent to a clay mixer (Fig. 3.2), where it is mixed with lean additives until a homogeneous plastic mass with a moisture content of 20...25% is obtained. The molding of ceramic products using the plastic method is carried out mainly on belt presses. In the semi-dry method, the clay mass is molded on hydraulic or mechanical presses under pressure of up to 15 MPa or more. By slip method the starting materials are crushed and mixed with a large amount of water (up to 60%) until a homogeneous mass is obtained - slip. Depending on the molding method, the slip is used both directly for products obtained by casting, and after drying it in spray dryers.

A mandatory intermediate operation in the technological process of producing ceramic products using the plastic method is drying. If the raw material, which has high humidity, is fired immediately after molding, it will crack. When drying raw materials artificially, flue gases from kilns and special furnaces are used as a coolant. In the manufacture of fine ceramic products, hot air generated in heaters is used. Artificial drying is carried out in batch chamber dryers or continuous tunnel dryers (Fig. 3.4).

The drying process is a complex of phenomena associated with heat and mass transfer between the material and the environment. As a result, moisture moves from the inside of the product to the surface and evaporates. Simultaneously with the removal of moisture, the particles of the material come closer together and shrinkage occurs. The reduction in the volume of clay products during drying occurs up to a certain limit, despite the fact that the water has not yet completely evaporated at this point. To obtain high-quality ceramic products, the drying and firing processes must be carried out under strict conditions. When the product is heated in the temperature range O...15O°C, hygroscopic moisture is removed from it. At a temperature of 70°C, the pressure of water vapor inside the product can reach a significant value, therefore, to prevent cracks, the temperature should be raised slowly (5O...8O°C/h) so that the rate of pore formation inside the material does not outstrip the filtration of vapors through its thickness.

Firing is the final stage of the technological process. The raw material enters the oven with a humidity of 8...12%, and in the initial period it is completely dried. In the temperature range of 550...800°C, dehydration of clay minerals and removal of chemically bound constitutional water occurs. In this case, the crystal lattice of the mineral is destroyed and the clay loses its plasticity, at which time shrinkage of the products occurs.

At a temperature of 200...800°C, the volatile part of the organic impurities of clay and burnable additives introduced into the mixture during the molding of products is released, and, in addition, the organic impurities are oxidized within the limits of their ignition temperature. This period is characterized by a very high rate of temperature rise - 300...350°C/h, and for efficient products - 400...450°C/h, which contributes to the rapid burnout of fuel pressed into the raw material. Then the products are kept at this temperature in an oxidizing atmosphere until the carbon residues are completely burned out.

A further rise in temperature from 800°C to the maximum is associated with the destruction of the crystal lattice of clay minerals and a significant structural change in the shard, therefore the rate of temperature rise is slowed down to 1OO...15O°C/h, and for hollow products - to 200...220° S/h. Upon reaching the maximum firing temperature, the product is held to equalize the temperature throughout its entire thickness, after which the temperature is reduced by 1OO...15O°C, as a result the product undergoes shrinkage and plastic deformation.

Then the cooling intensity at temperatures below 800°C increases to 250...300°C/h or more. The temperature decline can only be limited by the conditions of external heat exchange. Under such conditions, brick firing can be carried out in 6...8 hours. However, in conventional tunnel kilns, high-speed firing modes cannot be implemented due to the large unevenness of the temperature field across the cross section of the firing channel. Products made from low-melting clays are fired at a temperature of 900...1100°C. As a result of firing, the product acquires a stone-like state, high water resistance, strength, frost resistance and other valuable construction qualities.

General information

Natural stone materials are materials and products obtained by mechanical processing (crushing, splitting, sawing, etc.) of rocks. Natural stone, used directly as a building material, attracts with its decorativeness and durability.

A huge amount of natural stone materials is used as raw material for the production of most building materials: ceramics, glass, mineral binders.

The raw material base for the building materials industry is rocks. They are used for the production of inorganic binders, ceramic materials, building glass, crushed stone, gravel, sand in road construction and for the preparation of concrete and mortars, cladding of buildings, structures and many other purposes.

Rocks are called accumulations of mineral masses that form geological bodies characterized by a fairly constant composition, structure and properties. The percentage of minerals in a rock determines its mineral composition. The shape, size, relative position of minerals, presence of pores, etc. determine the properties of the rock.

Mineral called a natural body, homogeneous in chemical composition, structure and properties, formed as a result of physical and chemical processes on the surface and in the depths of the earth. The overwhelming majority of minerals are solids: crystalline and amorphous.

If a rock consists of one mineral, it is called monomineral, if it consists of two or more, it is called polymineral.

Depending on the conditions of formation, rocks are divided into three types: primary - igneous, secondary - sedimentary, modified - metamorphic.

Erupted The rocks are very diverse in physical and mechanical characteristics. If the magma solidified at depth, and its components had time to crystallize, then the so-called deep (intrusive) rocks, which are characterized by a holocrystalline structure, were formed. If, as a result of volcanic activity, magma erupted to the surface, into a zone of significantly lower temperatures, its components did not have time to crystallize and, when solidified, formed rocks with hidden and fine-crystalline structures (effusive).

Many natural stones of this group are distinguished by high density, thermal conductivity, strength and are used exclusively as structural, finishing and finishing materials.

At the same time, clastic (loose and cemented) igneous rocks characterized by relatively high porosity - pumice, volcanic tuff - are also quite widespread.

Sedimentary rocks formed as a result of the transformation of destruction products of igneous rocks, marine and continental sediments in the form of separate layers and layers on and near the earth's surface at relatively low temperatures and pressure. Mechanical sediments were formed as a result of the deposition or accumulation of loose decay products of pre-existing rocks, some of which were subsequently cemented, forming conglomerates, breccias and sandstones. Chemical sediments were formed as a result of precipitation of mineral substances from aqueous solutions, followed by compaction and cementation. Organogenic formation is the result of direct sedimentation, compaction and cementation of the remains of algae, organisms and their metabolic products.

Modified (metamorphic) rocks are formed in the thickness of the earth's crust as a result of more or less deep transformation of igneous or sedimentary rocks under the action of high temperatures and pressure, as well as possible chemical exposure. Metamorphic rocks differ from the original ones in structure and properties. Based on their structure, they are divided into massive or granular (marble, quartzite) and schistose (gneisses, schists).

Technology Basics

Stone blocks obtained from the quarry are sent to stone processing plants for processing. The process by which the stone is given the required shape, size and texture of the front surface includes a number of operations performed in strict sequence using a variety of stone-processing machines. In modern enterprises, stone is processed using a mechanized method. Depending on the nature of the tool used, three main types of processing are distinguished: cutting, grinding and chipping. Each of these types, in turn, is divided into two stages: giving the shape and size of the product and its texture processing. To do this, the front surface of the product is given a given degree of relief.

Machining– the most modern stone processing process: this method is highly productive, produces less waste and allows for automation of production to the greatest extent. Depending on the hardness of the stone, steel and carbide cutters are used (for soft and medium-hard stones) or diamond and carborundum tools (for medium-hard and hard rocks) of a special design.

Chip processing is also a widely used method, but in most cases it requires constant operator participation and is therefore more labor-intensive. Impact processing of stone is mechanized and not fully automated.

Giving a stone the required shape, regardless of the adopted processing method, is carried out in two stages: first, the product is given a shape that roughly approaches the given one, and only then the product receives its final shape in accordance with the project.

Grinding The surface of the stone allows you to achieve a high degree of smoothness, up to a mirror shine (for this, a felt circle is used, under which polished powder is dropped).

Nomenclature

The range of natural stone materials includes blocks, stones, slabs, architectural and construction products (planar and profile).

Blocks with a volume of at least 0.1 m 3 for laying foundations and walls, depending on the technology of their processing, they are produced chipped, hewn, sawn.

Stones size 390*190*188; 490*240*188; 390*190*288 mm, etc. are similar in purpose to blocks.

Plates up to 2000 mm wide, usually no less than wide and with a thickness from 3 to 40 mm, used for external and internal cladding. The sizes of slabs for floor coverings are usually 300*300; 305*305; 400*400; 600*300 mm. For interiors with heavy traffic their thickness is at least 20mm.

Architectural and construction products used for external and internal cladding, staircases, platform parapets, and fences. This group of products includes base slabs, sawn and chipped, sawn and chipped covering slabs, sawn treads, solid sawn and chipped steps, rectangular and curved parapets, columns, balusters, portals, cornice details, belts, cordon stone, decorative balls.

Baluster – a relatively low figured column in the shape of a body of rotation. This is an element of fencing for stairs, terraces, balconies, the upper part of which is covered with railings. Balusters are made mainly from marble.

Portals– profile products for framing doorways, usually made from granite, gabbro, labradorite and other igneous rocks.

Cornice detail- a profile product in the form of a decorative protrusion on the upper part of the outer cladding of the wall field, protecting it from water flowing from the roof. Obtained by appropriate processing of igneous rocks.

Belt detail- a horizontal protruding element of the external cladding that separates the basement from the overlying wall. Sufficiently dense and durable rocks are used for production.

Cordon stone– a profile product of the upper part of a massive base made of dense and durable rocks.

Decorative ball– a spherical profile product. Balls (solid, but more often composite), mainly made of granite, are used in the design of building facades, fountains, embankments, and in landscape architecture.

TO special purpose material include rubble stone (pieces of irregular shape no more than 500 mm in greatest dimension), crushed stone (pieces up to 150 mm from crushed rubble), slabs for hydraulic structures made from igneous and sedimentary rocks; paving stones in the form of a block, slightly tapering downwards, from homogeneous fine- and medium-grained igneous rocks for paving roads; side stones up to 400 mm high from dense igneous rocks to separate the road from the sidewalk; pavement slabs (often made of gneiss) with a thickness of at least 40 mm.

Properties

Taking into account the characteristics of minerals, their quantity and nature of arrangement, as well as the type and location of the cementing substance, we distinguish crystalline, glassy, ​​porphyritic and other rock structures.

When determining the nature of the crystalline structure of a rock, in particular, the grain size is determined. Depending on their size, hard rocks (granite, etc.) have coarse-grained structures - more than 40 mm; medium-grained from 2 to 10 mm; fine-grained - up to 2 mm. Natural stones of medium hardness (marble, etc.) have a structure with a grain size of more than 1 mm that is considered coarse-grained; up to 1 mm – medium-grained; up to 0.25 mm - fine-grained.

Methods of extraction and processing of natural stone, its rational use in construction are associated, first of all, with hardness material.

When determining the hardness of natural stones, the Mohs scale is used, comparing their hardness with the hardness of certain minerals, arranged in a characteristic order as their hardness increases: talc, gypsum, calcite, fluorspar, apatite, orthoclase, quartz, topaz, corundum, diamond.

Hard natural stones have a higher solidity of structure compared to materials of medium hardness and soft ones. In architectural and construction practice, rocks of hard or medium hardness are usually used.

The average density of natural stone materials, depending on their type, is usually in the range of 800... 3100 kg/m 3.

Water absorption hard natural stones, as a rule, is in the range of 0.01 ... 5%; for granite and syenite - 0.1 ... 1%; gabbro – 0.1…0.2%; labradorite and teschenite – 0.2 ... 1%; diabase – 0.01 ... 0.2%; quartz porphyry – 0.1…5%; basalt – 1…5%. Water absorption of natural stones of medium hardness is 0.1...40%, including marble - 0.1...0.7%; limestone – 0.5… 40%; sandstone – 0.2…2.5%; tuffs – 4...40%.

The softening coefficient of these natural stone materials of medium hardness is, as a rule, not less than 0.6.

Frost resistance stone materials is relatively high. Hard natural stones (granite, diorite, syenite, gabbro) withstand 300 or more cycles of laboratory tests; diabase, basalt – 50 or more. Natural stones of medium hardness - more than 25 cycles, soft - 15 cycles or more.

Tensile strength when compressing natural stone materials, depending on hardness, is given in table.9 .

To determine the compressive strength, samples in the form of a cube or cylinder, sawn or drilled from the whole product, are usually tested. To test relatively large blocks, the height of which is more than 1.5 times the thickness, two samples are prepared (cut, drilled): from the upper and lower edges.

Abrasion is of great importance, first of all, for natural stone materials that are used for floor coverings in various public buildings. The abrasion rate of hard materials is very low - no more than 0.5 g/cm2.

Durability natural stones, as a rule, is associated with their hardness.