The main types of raw materials for the production of building materials. Wood is a raw material for the production of building materials. Environmental problems in the production of building materials

A forest is a part of the Earth's surface covered with trees. FOREST FOREST AS A MEAN OF PRODUCTION From an economic point of view, the forest acts as
main means of production, forming a special group
production assets, which include land
forest fund and timber reserves.
The main task of forestry, which is an independent
branch of the national economy is the cultivation, care, protection and
protecting forests, using them to continuously satisfy
the needs of the national economy in wood and other forest products, as well as the comprehensive use of the social functions of forests in a growing state - water protection, sanitary and hygiene, recreational, etc. PROVERBS ABOUT THE FOREST
To live next to the forest is not to be hungry.
The forest is richer than the king.
The forest is not only a wolf, but also a man
feeds to the full. WHAT THE FOREST IS USED FOR
source of food (mushrooms, berries, animals, birds) source of energy (firewood), raw material for the production of paper material for the construction and production of furniture and various products. FOREST - RAW MATERIALS FOR PRODUCTION
BUILDING MATERIALS

Construction is what they do
professional builders and
wanting to build something
with your own hands. TYPES OF CONSTRUCTION civil engineering;
industrial engineering;
transport construction;
agricultural construction;
military construction WOOD BUILDING MATERIALS When building or renovating a house, rarely anyone
does not use wood building materials. Natural
wood and building products from it are environmentally friendly and
practical to use, good value
in terms of price - quality. Building materials differ from
wood, depending on the method of manufacture. Last
are very popular with builders
recently appeared plates, in the production of which
use oriented chip direction. Such
the plates are sufficiently elastic and have high mechanical
properties. Building materials made of wood perfectly combine
variety, practicality and decorative properties, which makes
indispensable for any type of repair work. WOOD Wood is the oldest building material
accompanying material
person all his life. WOOD OF DIFFERENT SPECIES OF TREES
Oak and beech wood Ash and maple wood Larch and cedar wood
Pine and spruce wood ALDER WOOD

Administration of the city district of Samara
AMOU VPO Samara Academy of State and Municipal Administration

Faculty of Economics
Department of Cadastre and Geoinformation Technologies

Test
discipline: "Materials Science"
on the topic: "Raw materials for the production of ceramic building materials»

Samara, 2013
Contents
Introduction………………………………………………..…… ……….…..…….….3
I. General information and raw materials for the production of ceramic building materials……………………………………………………………………………..4
II. The formation of clay materials and their chemical and mineralogical compositions………………………………………………………………………………….6
2.1 Main mineral constituents of clays………………………………. 7
2.2 Impurities………………………………………………………………………..8
2.3 Chemical composition clay………………………………………………………...9

3.1 Granulometric composition of clays………………………………………….12
3.2 Technological properties of clays………………………………………………13
3.3 Classification of clay raw materials for ceramic products………20
Bibliography………………………………………….…. 24
Applications……………………………………………………………………....25

Introduction
In this control work, on the topic: "Ceramic building materials" we will consider:

general information and raw materials for the production of ceramic building materials;
formation of clay materials and their chemical and mineralogical compositions;
technological properties of clay materials.

Ceramic production is one of the oldest on earth. The presence of an easily accessible material - clay - led to the early and almost universal development of the craft.
Ceramic production originated in prehistoric times after people learned how to make and use fire. The man saw that with the help of heat it is possible to preserve the shape of objects molded from clay and make them impervious to water. It was soon noticed that all clays have different properties and that different clays should be used to make certain products.
Ceramic building materials fully meet the requirements of durability and have high architectural and artistic qualities. They are resistant to aggressive environments, weather-resistant and frost-resistant.
Ceramic products find the most diverse application in many sectors of the national economy and in everyday life. They are used as building materials - bricks, tiles, facing tiles for walls and floors, sewer pipes, various sanitary products. Dishes made of porcelain and earthenware remain the most common and widely used to date.

I. General information and raw materials for the production of ceramic building materials
Ceramic is called artificial stone materials obtained by firing raw material molded from clay rocks. Ceramic materials, used since ancient times, have many advantages: raw materials for them are widely distributed in nature; raw can be given any shape; fired products are strong and durable. The disadvantages of ceramic materials include: the possibility of manufacturing products of only relatively small sizes; high fuel consumption for firing; the difficulty of mechanizing work in the construction of structures made of ceramic materials.
Depending on the porosity, ceramic materials are divided into porous with water absorption of more than 5% and dense with water absorption of less than 5%. Both dense and porous materials can refer to rough pottery, characterized by a colored sherd, or fine pottery, characterized by a white and uniform sherd. Rough ceramics are widely used in construction. Regardless of the porosity and color of the sherd, ceramic materials can be unglazed and glazed. Glaze is a glassy layer applied to the surface of a material and fixed to it during firing. Glaze has a high density and chemical resistance.
Depending on the field of application in construction, ceramic materials are divided into the following groups:
wall - ordinary clay brick, hollow and porous-hollow plastic molding, full-bodied and hollow semi-dry pressing, hollow plastic molding stones;
hollow stones for often ribbed floors, for reinforced ceramic beams, stones for reels;
for facing the facades of buildings - facing bricks and stones, carpet ceramics, small-sized facade tiles, facade slabs and window sills;
for interior cladding of buildings - tiles for wall cladding, built-in parts, floor tiles;
roofing - ordinary, ridge, grooved end and special clay tiles;
ceramic pipes - sewer and drainage;
special-purpose materials - curved bricks, stones for sewerage facilities, sanitary and highly porous heat-insulating ceramics, acid-resistant products (bricks, tiles, shaped parts and pipes), refractory products (bricks, shaped tiles and parts).
According to the established tradition, porous products of a coarse-grained structure made of clay masses are called coarse ceramics, and dense products of a fine-grained structure, CA with a sintered shard, waterproof, such as floor tiles, are called fine building ceramics.
In the production of building ceramics, mainly methods of plastic formation and semi-dry pressing are used, and much less often casting in plaster molds (sanitary products).
Many scientists believe that mullite provides the main strength of sintered ceramic materials. Mullite 3Al 2 O 3 ? 2SiO 2 forms needle-shaped, prismatic or fibrous crystals with clearly visible perfect cleavage.
The composition of mullite has long been the subject of discussion, as a result of which the researchers came to the conclusion that the composition of mullite ranges from 2Al 2 O 3 ? SiO 2 to 3Al 2 O 3? 2SiO2.
The mineral can form intergrowths and clusters (Appendix A). Impurities Fe 2 O 3 and TiO 2 cause the appearance of pleochrysm in yellowish and bluish tones. The density of mullite is 3.03 g/cm 3 . The size of mullite crystals is varied: from 2 to 5 × 10 -6 m, in fireclay - up to 10 mm in length in mullite products. Also included in porcelain.

II. Formation of clay materials and their chemical and mineralogical compositions
Clay - a finely dispersed product of decomposition and weathering of a wide variety of rocks (the predominant particle size is less than 0.01 mm) - is able to form a plastic mass with water, which retains the shape given to it, and after drying and firing acquires stone-like properties.
Depending on the geological conditions of formation, clays are divided into residual or primary (eluvial), formed directly at the site of the parent rock, and sedimentary or secondary, formed by transfer and redeposition by water, wind or glaciers to a new location. As a rule, eluvial clays are of poor quality, parent rocks are preserved in them, they are often clogged with iron hydroxides and are usually of low plasticity.
Secondary clays are divided into deluvial, transferred by rain or snow waters, glacial and loess, transferred by glaciers and wind, respectively. Deluvial clays are characterized by layered stratifications, a large heterogeneity of composition, and clogging with various impurities. Glacial clays usually lie in lenses and are heavily clogged with foreign inclusions (from large boulders to small gravel). The loess clays are the most homogeneous. They are characterized by high dispersion and porous structure.
Clay rocks (clays, loams, mudstones, siltstones, slates, and others) used as raw materials for the production of ceramic bricks and stones must comply with the requirements of OST 21-78-88 (valid until 01.01.96), and the classification of raw materials is given in GOST 9169-75*.
The suitability of clay for brick is determined based on the mineral-petrographic characteristics, chemical composition, indicators of technological properties and rational characteristics.
2.1 Main mineral constituents of clays: kaolinite, montmorillonite, hydromica (illite).
Kaolinite (Al 2 O 3 ? 2SiO 2 ? 2H 2 O) - has a relatively dense structure of the crystal lattice with a relatively small interplanar distance of 7.2 A. Therefore, kaolinite is not able to attach and firmly retain a large amount of water, and when drying clay with a high content kaolinite relatively freely and quickly release the attached water. The particle size of kaolinite is 0.003 - 0.001 mm. The main varieties of the kaolinite group are kaolinite, dickite, and nakrit. Kaolinite is the most common. Kaolinite is not very sensitive to drying and firing, slightly swells in water and has a low adsorption capacity and plasticity.
Montmorillonite - (Al 2 O 3? 2SiO 2? 2H 2 O? nH 2 O) (app. B) - has a weak bond between the packages, since the distance between them is relatively large - 9.6-21.4 A, and it can increase under the influence of wedged water molecules. In other words, the crystal lattice of montmorillonite is mobile (swelling). Therefore, montmorillonite clays are able to intensively absorb a large amount of water, hold it firmly and are difficult to give up when dried, and also swell strongly when moistened with an increase in volume up to 16 times. The particle size of montmorillonite is much smaller than 1 micron (<0,001мм). Эти глины имеют наиболее высокую дисперсность среди всех глинистых минералов, наибольшую набухаемость, пластичность, связность и высокую чувствительность к сушке и обжигу.
The main representatives of the montmorillonite group are: montmorillonite, nontronite, beidelite.
Halloysite - Al 2 O 3 ? 2SiO2? 4H 2 O - includes halloysite, ferrigalloysite and metahalloysite, is a frequent companion in kaolinites and kaolinite clays. Halloysite, compared with kaolinite, has greater fineness, plasticity, and adsorption capacity.
Hydromicas - (illite, hydromuscovite, glauconite, etc.) are the product of varying degrees of hydration of micas. They are found in significant quantities in fusible clays and in small quantities in refractory and refractory clays.
Illite (hydromica) - K 2 O? MgO? 4Al2O3? 7SiO2? 2H 2 O - is a product of long-term hydration of micas, and its crystal lattice is similar to montmorillonite. According to the intensity of bonding with water, hydromicas occupy a middle position between kaolinite and montmorillonite. The particle size of hydromica is about 1 micron (~0.001 mm).
2.2 Impurities.
In addition to clay components, clay rocks contain various impurities, which are divided into quartz, carbonate, ferruginous, organic and alkaline oxides.
Quartz impurities are found in clay in the form of quartz sand and dust. They thin the clay and impair its plasticity and molding properties, although coarse quartz sand improves the drying properties of clays, while fine sand worsens them. At the same time, quartz impurities worsen the firing properties, lowering the crack resistance of fired products during their cooling, and reduce strength and frost resistance.
Carbonate impurities are found in clays in 3 structural forms: in the form of finely dispersed evenly distributed silt particles, loose and farinaceous impurities, and in the form of dense stony particles.
Finely dispersed carbonate impurities, decomposing during firing according to the reaction CaCO 3 =CaO + CO 2, contribute to the formation of a porous shard and reduce its strength. These small inclusions are not harmful to wall ceramics. Loose deposits and accumulations during the mechanical processing of clay are easily broken down into smaller ones and do not significantly reduce the quality of products.
The most harmful and dangerous are stony carbonate inclusions with a size of more than 1 mm, since after ceramics are fired, these inclusions remain in the crock in the form of burnt lime, which subsequently, when moisture is added from the atmosphere or, for example, when the fired products are moistened, passes into calcium hydroxide according to the scheme
CaO + H 2 O \u003d Ca (OH) 2 + Q (heat).
Considering that the volume of hydroxide increases more than four times compared to CaO, significant internal stresses arise in the shard, causing the formation of cracks. If there are many of these inclusions, the complete destruction of the ceramic product is possible.
Ferrous impurities color ceramics in different colors: from light brown to dark red and even black. Organic impurities burn out during firing, they significantly affect the drying of the product, as they cause large shrinkage, which leads to the formation of cracks.
2.3 Chemical composition of clays.
The content of the main chemical components in the clay rock is estimated by the quantitative content of silicon dioxide, including free quartz, the sum of oxides of aluminum and titanium, iron, calcium and magnesium, potassium and sodium, the sum of sulfur compounds (in terms of SO 3), including sulfide.
Usually the chemical composition of fusible clays is, %: SiO 2 - 60 ... 85; Al 2 O 3 together with TiO 2 - not less than 7; Fe 2 O 3 together with FeO- no more than 14; CaO + MgO - no more than 20; R 2 O (K 2 O + Na 2 O) - no more than 7.
Comparative characteristics of the chemical composition of various clays are given in table. one.

Table 1. Chemical composition of clays

Silica (SiO 2) is found in clays in bound and free states. The first is part of the clay-forming minerals, and the second is represented by silica impurities. With an increase in the content of SiO 2, the plasticity of clays decreases, porosity increases, and the strength of fired products decreases. Limiting content of SiO 2 - no more than 85%, including free quartz - no more than 60%.
Alumina (Al 2 O 3) is in the composition of clay-forming minerals and micaceous impurities. With an increase in the content of Al 2 O 3 increases the plasticity and refractoriness of clays. Usually, the content of alumina indirectly judges the relative value of the clay fraction in the clay rock. Alumina is contained from 10-15% in brick and up to 32-35% in refractory clays.
Oxides of alkaline earth metals (CaO and MgO) are present in small amounts in some clay minerals. At high temperatures, CaO reacts with Al 2 O 3 and SiO 2 and, forming eutectic melts in the form of aluminum-calcium-silicate glasses, sharply lower the melting point of clays.
Oxides of alkaline earth metals (Na 2 O and K 2 O) are part of some clay-forming minerals, but in most cases they are involved in impurities in the form of soluble salts and in feldspar sands. They lower the melting point of clay and weaken the coloring effect of Fe 2 O 3 and TiO 2 . Alkali metal oxides are strong fluxes, contribute to increased shrinkage, compaction of the shard and increase its strength.
As the limiting value of sulfur compounds in terms of SO 3, no more than 2% is taken, including sulfide - no more than 0.8%. In the presence of SO 3 more than 0.5%, including sulfide not more than 0.3%, in the process of testing clay rocks, methods should be determined to eliminate efflorescence and efflorescence on unfired products by converting soluble salts into insoluble ones.

III. Technological properties of clay materials
3.1 The granulometric composition of clays is the distribution of grains in clay rock by their size. Typically, the grain composition of various clays is characterized by the data shown in Table 2.
Table 2 . Grain composition of clays

Comparing the data of the tables of chemical (table 1) and granulometric (table 2) compositions, we can conclude that there are significant fluctuations for various clays, which does not allow us to accurately establish the relationship with the properties of raw materials. However, there are certain general patterns. A slight content of alumina (Al 2 O 3) with a high content of silica (SiO 2) indicates a high content of free silica, which is mainly found in the coarse component of clays and is a natural lean additive.
Low-melting clays are characterized by the highest content of SiO 2 and fluxes (R 2 O, RO, Fe 2 O 3) and the lowest content of Al 2 O 3 . Here, alumina is almost completely included in the composition of clay-forming minerals, as indicated by the data of Table 2, where the content of particles less than 0.001 mm in low-melting clays is the lowest compared to refractory and refractory ones.
The increased content of Al 2 O 3 in clays indicates a large amount of clay matter, its greater dispersion, and, consequently, greater plasticity and connectivity of the material. A high content of fluxes and especially R 2 O (Na 2 O and K 2 O) with a low content of Al 2 O 3 indicates a low fire resistance of clay. The less smoother clay contains, the more refractory it is and sinter at higher temperatures. However, the simultaneous presence in the clay of a significant amount of alkali oxides (mainly K 2 O) with a simultaneous high content of Al 2 O 3 and a low content of other fluxes can also determine the high refractoriness of clays and the ability to sinter at low temperatures, which makes it possible to produce a wide range of porous and sintered products. Thus, based on the knowledge of the chemical-mineralogical and grain composition of raw materials, it is possible to approximately estimate its properties.

3.2 Technological properties of clays characterize the material at different stages of its processing in the process of making products from it. The technological properties of clayey rocks are studied in the laboratory, and the results of the study, as a rule, are verified in semi-industrial conditions. For bentonite, refractory clays and ceramic raw materials, the results of laboratory studies are verified under industrial conditions. With the planned use of clay rocks for purposes for which there is no experience of processing under industrial conditions, as well as when studying the possibility of using raw materials that do not meet the requirements of standards and specifications, technological research is carried out according to a special program agreed with interested organizations.
The most important technological properties of clay rocks that determine their use in industry are plasticity, fire resistance, sintering, swelling, as well as swelling, shrinkage, shrinkage, adsorption capacity, binding capacity, hiding power, color, the ability to form stable suspensions with excess water, relative chemical inertness. . These properties are determined by the processes occurring in the material when it is mixed with water, molded, dried, and fired.
If dry clay powder is moistened with water, its temperature will rise. This is due to the fact that water molecules are strongly associated with clay-forming minerals and are located on them in a certain order.

Moisture capacity characterizes the ability of clay to contain a certain amount of water and retain it. With an increase in the dispersion of clay, its moisture capacity increases. Montmorillonite clays have the highest moisture capacity, kaolinite clays have the lowest.

Swelling refers to the ability of clay to increase its volume by absorbing moisture from the air or by direct contact with water. The swelling process decays with time. Loose clay rocks swell faster than dense ones. The sand content of clays reduces the degree of their swelling. Montmorillonite clays swell more than kaolinite clays.

Soaking is the disintegration of large clay aggregates in water into smaller or elementary particles. The first stage of the disintegration of the clay aggregate occurs during its swelling, when water molecules, being drawn into the gaps between the clay grains, wedged them. As the thickness of the water shell increases, the connection between the individual grains of clay is weakened, and they begin to move freely in the water, being in suspension in it - the clay is completely soaked. To speed up the soaking process, the clay is stirred, mechanically destroying its pieces, or water is heated.
Clay soaks in water. Dense clays get wet very hard. Pre-crushing and stirring during soaking speed up this process. When soaked, water, penetrating into the pores between the clay particles, wedged them. Aggregated particles decompose into smaller grains or elementary particles of clay minerals with the formation of a polydisperse system. At the same time, clay particles begin to absorb water, which is absorbed between the layers of groups of atoms (“package”) of the crystal lattice of clay particles. In this case, the particles swell, increase in volume.
Water in clay always contains a certain amount of dissolved salts, the molecules of which are dissociated into ions. The cations of these salts, being carriers of positive charges, are also surrounded by their “own” water shell and, together with it, can be located either in a diffuse layer or on the surface of a grain of a clay-forming mineral, creating the so-called sorbed complex.
The processes that take place with the participation of the exchange complex of ions dramatically affect the stability (resistance to settling) of clay suspensions of slips, the filtration of water in clay-containing masses during the processes of dehydration (filter pressing) of the masses or during drying. They affect the mechanical properties of plastic clay masses and dry semi-finished products.

Thixotropic hardening is the property of a wet clay mass to spontaneously restore the broken structure and strength. So, if a freshly prepared slip (a clay mass of a liquid consistency) is left alone for some time, then it will thicken and harden, and after mixing, its fluidity will be restored. This may be repeated many times. Self-hardening of clay occurs due to the process of reorientation of clay particles and water molecules, which increases the strength of their adhesion. In this case, part of the free water passes into the bound. The thixotropy of clays is of great importance in the preparation of slips, plastic dough and molding of products.

The phenomenon of thixotropic hardening of clay slurry in the ceramic industry is called thickening. The amount of thickening depends on the nature of the clays, electrolyte content and moisture content.

Liquefaction - the property of clays and kaolins to form mobile stable suspensions when water is added. The amount of water required for liquefaction is determined by the mineralogical composition of the clays and is controlled by the addition of electrolytes. Optimum dilution, i.e., the combination of sufficient fluidity and the lowest content of hearth, is achieved with the right choice of electrolyte and its concentration. As electrolytes, usually 5% or 10% solutions of soda, liquid glass, sodium pyrophosphate, etc. are used.
Plasticity - the ability of clay to form a dough when mixed with water, which, under the influence of external mechanical forces, can take any shape without breaking the continuity and retain this shape after the cessation of the forces. The plasticity of clays depends on grain and mineralogical compositions, as well as sandy clays. With an increase in the dispersion of clays, their plasticity increases, montmorillonite clays have the highest plasticity, and kaolinite clays have the lowest.

Binding ability - the property of clays to bind particles of inelastic materials (sand, fireclay), while maintaining the ability of the mass to be molded and give a sufficiently strong product after drying. The binding capacity depends on the grain and mineralogical composition of the clay.
The changes that occur in the clay mass during its drying are expressed in such properties as air shrinkage, clay sensitivity to drying, and moisture-conducting ability.

Air shrinkage is a decrease in the linear dimensions and volume of a clay sample during its drying. The amount of air shrinkage depends on the quantitative and qualitative composition of the clay substance and the moisture capacity of the clay and ranges from 2 to 10%. Montmorillonite clays have the highest shrinkage, while kaolinite clays have the lowest. The sand content of clays reduces air shrinkage.
For the same clay, the amount of air shrinkage depends on the initial moisture content of the sample. In the first drying period, the volumetric shrinkage is equal to the volume of moisture evaporated from the product. In this case, first of all, capillary water evaporates from the clay, which has a less strong bond with clay particles. Then water from the hydration shells begins to move into the capillaries, the thickness of the shells decreases, and the clay particles begin to approach each other. Then there comes a moment when the particles come into contact, and the shrinkage gradually stops. Grains of non-plastic materials can also come together due to the convergence of clay particles, however, other grains prevent the complete convergence of clay particles, i.e., the presence of non-plastic materials in the mass reduces air shrinkage.

The sensitivity of clays to drying affects the drying time - the greater the sensitivity of the clay to drying, the more time it takes to dry to get a product without cracks. With an increase in the content of clay matter, especially montmorillonite, the sensitivity of clays to drying increases.

Moisture-conducting capacity characterizes the intensity of moisture movement inside the drying product. The process of drying a clay product includes three phases: the movement of moisture inside the material, the formation of vapor and the movement of water vapor from the surface of the product into the environment. A quantitative measure that indirectly characterizes the intensity of moisture movement inside a drying product is the diffusion coefficient. It depends on the size of the capillaries, temperature, moisture content, type of clay mineral (in montmorillonite clays it is 10-15 times less than in kaolinite clays), sand content of clays.

In the process of heating clays, their thermal properties are manifested. The most important of them are refractoriness, caking and fire shrinkage.

Fire resistance - the ability of clays to resist exposure to high temperatures without melting. The fire resistance of clays depends on their chemical composition. Alumina increases the refractoriness of clays, fine silica decreases it, and coarse-grained silica increases it. Alkali metal salts (sodium, potassium) sharply lower the fire resistance of clays and serve as the strongest fluxes, oxides of alkaline earth metals also reduce the fire resistance of clays, but their effect is manifested at higher temperatures. In terms of refractoriness (°C), clay raw materials are divided into three groups: 1st - refractory (1580 and above), 2nd - refractory (less than 1580 - up to 1350), 3rd - fusible (less than 1350).
Refractory varieties of clayey rocks are mainly of kaolinite, hydromicaceous and halloysite composition or consist of a mixture of these minerals with an admixture of quartz and carbonates. The chemical composition of refractory clay rocks is dominated by SiO2 and Al2O3, which in the best varieties of refractory clays are in quantities close to their content in kaolinite (SiO2 - 46.5%, Al2O3 - 39.5%). In some varieties of refractory clays, the content of A12O3 is reduced to 15–20%. Iron oxides and sulfides are found in subordinate amounts. Harmful impurities are calcite, gypsum, siderite, Mn and Ti compounds.
Refractory clayey rocks are not consistent in terms of mineral composition: they contain kaolinite, halloysite, hydromica and, as impurities, quartz, mica, feldspar and other minerals. Alumina is contained in them in the range of 18–24%, sometimes up to 30–32%; silica - 50-60%, iron oxides - up to 4-6%, less often 7-12%.
Low-melting clay rocks, as a rule, are polymineral. Usually they contain montmorillonite, beidellite, hydromicas and impurities of quartz, micas, carbonates and other minerals. The content of alumina in these rocks does not exceed 15–18%, silica - 80%, and the content of iron oxides is increased to 8–12%. They are also characterized by a high content of floodplains - finely dispersed impurities of ferruginous, calcium, magnesium and alkaline minerals.
Caking - the ability of clays to compact during firing with the formation of a solid stone-like shard. It is characterized by the degree and interval of sintering.

The degree of sintering is controlled by the amount of water absorption and the density of the ceramic shard. Depending on the degree of sintering, clay raw materials are divided into strongly caking (a shard is obtained without signs of burnout with water absorption of less than 2%), medium sintering (a shard with water absorption of 2-5%) and non-sintering (a shard with water absorption of 5% or less without signs of burnout is not obtained) . Signs of overburning are deformation of the sample, visible swelling or a decrease in its overall density by more than 0.05*10 g/cm3. The indicated water absorption values ​​\u200b\u200bshould be maintained at least at two temperature points with an interval of 50 ° C. For example, if during the firing of clay at a temperature of 1150 ° C, the shard has a water absorption of 0.5%, and at 1100 - 2%, the clay is highly caking, and if the same clay at a temperature of 1100:; "C forms a shard with a water absorption of 4%, it is referred to as medium sintering.

Clay sintering can occur at different temperatures
etc.................