History of the need for building materials

Level (6 points)

History of the need for building materials

Requirements to construction materials

The basic requirements for materials include:

1. Sufficient compressive strength, tensile, bending and so on. D.

2. Deformation (elasticity, plasticity, creep, etc.) - To ensure minimum deformability of structures.

3. Resistance to dynamic effects.

4. Resistance to high and low temperatures.

5. The hardness and friability

6. Resistance to chemically active media

7. Resistance to climatic factors (temperature, environment, solar radiation, and so on. D.

8. Resistance to radioactive and other emissions.

9. Ability to surface hardening and bonding with other materials

10. The ability to create composites

11. Other properties (permeability, specific heat, thermal conductivity)

12. processability during manufacture, and as a structural material

13. Maintainability and interchangeability of structures and their elements

14. Reuse and recycling

15. Ecological safety for humans and animals.

The most widespread applications are silicate materials, their amount is 80% of the total volume of materials used in construction.

 

Determination of clinker, cement and additives introduced in the grinding

The first "unified norms delivery and verification of Portland cement" appeared in Germany in 1878. It was the first German standard, which normalized the quality of the material, while the mass of the product. In 1909. Portland cement and ferrous were standardized in 1917. - Shlakoportlandtsement.Portlandtsement made from clinker with the addition of sulfate (gypsum rock or rock anhydrite in a quantity of 5-10%) and ferrous slag Portland cement further comprises granulated blast furnace slag, Open Path - additionally contains traces. In addition to these species in some countries it is also produced alumina cement and sulphate slag. These two types of cement in the Federal Republic of Germany are not made and are not standartizovany.Teper in Germany and many other European countries, there is a norm (standard) EN 197-1, gives a definition of cement as follows: "The cement - hydraulic binder, obtained by pulverizing inorganic material that, when mixed with water forms a cementitious paste, which hydrates, becomes stable and hardens under water and indoors "[As to standard EN 197-1 cement exists with the introduction of secondary components in an amount of 0-5%. The following possible basic components:

● Portland cement clinker (K)

● The granulated blast furnace slag (S)

● pozzolan

- Natural pozzolan (P)

- Natural volcanic pozzolan (Q)

● Fly ash

- Rich in silica fly ash (V)

- Lime rich fly ash (W)

● Burnt shale (T)

● Limestone (L, LL)

● Silikashtaub (D)

Additionally, the cement also contains calcium sulfate, cement and some technological additives.

 

Portland cement clinker.

Portland cement - the most important building material widely used in the national economy to the description of its properties, technology of production and application conditions is devoted a lot of work both in our country and abroad, but the published books are usually devoted to specific issues of chemistry and technology of production and application of this vyazh} conductive material.

This book is a continuation of the monograph "Portland cement clinker" (published Stroyizdat in 1967), in which the results of the study of the processes and the impact of clinker were compiled on these processes a variety of factors. This book examines the phase composition of Portland cement, the basic crystal structure of its minerals - two- and trehkalyshevogo silicates trehkalyshevogo aluminate, calcium alyumoferritov, as well as the composition and structure of the nonequilibrium and intermediate phases and complex compounds. Recent data on IP-adherence polymorphism tvertyh solutions, stability of minerals in pure form and in the composition of clinker.

He described in detail the relationship between the physical structure of the clinker and its resistance of grinding in the process of becoming a portlandtsement- iyn powder. The influence pores of different size and microstructure of clinker on the nucleation and growth of cracks in the grain for energy consumption for grinding material to form grain cement composition, as well as impact on the clinker modifying its microstructure chromium, phosphorus, sulfur, titanium, barium and other elements and the role of surfactants added to the milled material in a liquid or solid form.

Because of the general problem of hydration and hardening of binders in the book covered only "interviews concerning the activity of cements prepared from clinkers, modified chromium, phosphorus, sulfur, titanium, barium and arugpmn elements.

All sections of this monograph is given great attention to the modification of the composition and the physical structure of the clinker minerals crystals using various elements forming solid solutions in the major phases, and the impact of the relevant polymorphic transitions and a deformation processes gndratatsponpuyu cement activity.

 

Phase aluminate

Aluminate phase content is 5-10% for most normal cement clinkers. It tricalcium aluminate 3SaO * Al2O3, significantly modified the composition and sometimes the structure, due to foreign ions, especially Si4 +, Fe3 +, Na + and K +. Aluminate phase reacts rapidly with water and may cause undesirably rapid setting, if no seizure supervising added reagent commonly gypsum.

Aluminate phase is usually credited with the formula trehkaltsie Vågå-aluminate (S3L), although the amount determined by microscopic and X-ray methods, usually less than this estimate. This is because a certain amount of alumina compounds dissolved in the silicate clinker.

Alumina is included in the composition of the aluminate phases of Portland cement. Elevated amounts accelerate its setting time and a decrease in the durability of stone in the mineralized waters.

When hydration of granulated blast slag aluminate phase turns into hydrogarnet similar in composition and properties from the hexahydrate calcium hydroaluminates or in gidroalyuminatnye siliceous phases of variable composition.

However, it was found a discrepancy in the definition phase of the aluminate, which causes the need to improve the clinker composition assessment methods. Young showed that C3A strongly adsorbs surfactants from solution and therefore with a considerable content of aluminate phases to mitigate hydration needs a high percentage lignosulfate.

When calculating the mineralogical composition take that into the clinker contains only pure minerals C3S, C2S, C3A, C4AF; aluminate C3A phase is represented; sulfates - sul calcium sulfonate. It is believed that no vitreous phase.

The advantage of sodium nitrite, as well as other, nitrite salts introduced into the concrete mixture, consists in the fact that the nitrite ion with the aluminate phases unreacted cement and hydroaluminates cement stone calcium interacts with a slower rate and leads to a sparingly soluble double salt hydrate: gidrshitrialyumI Nat calcium with less complete than the chloride ion.

 

Phase Ferrite

Alyumoferritnaya phase ferritic phase (CaAlFe) is 5-15% of normal cement clinker. It - chetyrёhkaltsievy alumina ferrite 4CaO * Al2O3 * Fe2O3, the composition of which varies considerably when changing Al / Fe ratio in the structure and placement of foreign ions. The rate at which the ferrite phase is reacted with water, may vary somewhat due to differences in the composition or other characteristics, but usually, it is high in the initial period and is intermediate between the speed of alite and belite at a later date.

The clinker is typically present in small amounts of several other phases such as alkali sulfates and calcium oxide.

 

Conditions of synthesis of silicates, aluminates and ferrites of calcium that make up clinker, as well as a number of intermediate compounds are important in the chemistry of cement. A significant role is played by the thermodynamic analysis in their study.

As for the hydration reactions alyumoferrita calcium and iron, the complete lack of thermochemical data for calcium gidroferritov does not allow currently consider their thermodynamics.

With further increase in temperature calcium ferrite lines intensity decreases and begins to appear 2CaO - AbOa-SiCfe, which at temperatures of 1100 - 1200 C becomes the main phase.

The portland cement are silicates, aluminates and calcium ferrites formed in roasting raw Oomes. The resulting, after firing the raw mix product - clinker - is crushed and finely ground. A joint lomola clinker and additives yielding the final product - Portland cement.

Clinker minerals (silicates, calcium aluminates and ferrites) by reacting with water undergo hydrolysis and the salts formed by a strong base and a weak acid.

Hydrolysis of Tricalcium hydroaluminate formed and calcium ferrites.

Clinker minerals (silicates, calcium aluminates and ferrites) by reacting with water undergo hydrolysis and the salts formed by a strong base and a weak acid.

Locally on the boundaries between the crystals of magnetite and calcium ferrite observed globular discharge grayish-bluish crystals of potassium ferrite. This phase is anisotropic and hygroscopic, at high magnification, and especially in the study of immersion oil has a reddish-brown internal reflections. It has previously been shown that the catalysts prepared by standard methods (fuse resistance in melting furnaces and oxygen), potassium ferrites formed by introducing potassium hydroxide over 0.65 wt. Our research found that catalysts prepared at high temperatures, this phase is observed only in making potassium hydroxide over 2 wt. Based on these data it can be assumed that part of the potassium hydroxide dissolves magnetite lattice to form solid solutions isomorphous substitution, the remainder goes into a glassy phase.

Formed during firing lime silicates, aluminates and calcium ferrites according to its quantitative content may more or less influence on the physico-chemical properties of lime. In pure limestone and sandy clay content of impurities is expressed in small amounts. Therefore bystrogasya formed schiesya-lime due to its high content of free calcium oxide. However, they can always contain some substances that are holders gidravlichnosti properties. These substances include silicates, aluminates and ferrites of calcium, formed due to the presence of limestone in the fuel ash and calcium oxide impurities. At a low content of these formations in the hydraulic properties of lime binder did not show up.

Hydraulic hardening due to the presence of silicates, aluminates and ferrites of calcium that form in contact with water hydrosilicates, hydroaluminates and calcium gidroferrity.

Hydraulic hardening due to the presence of silicates, aluminates and ferrites of calcium that form in contact with water hydrosilicates, gkdroalyuminaty and calcium gkdroferrity.

With increasing content of silicates, aluminates and calcium ferrites conditions hardening hydraulic lime close to the conditions of curing romantsementa, and with increasing amounts of calcium hydroxide - to the conditions of an air hardening lime.

The smaller the product would be fired in silicates, aluminates and calcium ferrites, so rapid and complete is extinguished lime and relatively more malleable dough is obtained.

 

Other clinker phases

alite

It is the most important part of all conventional cement clinkers; its content is 50-70%. It trёhkaltsievy silicate 3SaO * SiO2 (abbreviated C3S), the composition and structure of which are modified due to placement in the lattice of foreign ions, especially of Mg2 +, Al3 + and Fe3 +. Alite relatively quickly reacts with water and normal phases of all cements plays the most important role in the development of strength; daily for 28 strength contribution of this phase is particularly important.

Belit

Content for normal belite cement clinker is 15-30%. This dicalcium silicate 2SaO * SiO2 (C2S), modified by introducing into the structure of the foreign ions and usually completely or predominantly present in a β-modification. Belit slowly reacts with water, thus affecting the strength weak during the first 28 days, but significantly increases the strength at a later date. A year later, the strength of pure alite and belite net under comparable conditions are about the same.

aluminate phase

Aluminate phase content is 5-10% for most normal cement clinkers. It tricalcium aluminate 3SaO * Al2O3, significantly modified the composition and sometimes the structure, due to foreign ions, especially Si4 +, Fe3 +, Na + and K +. Aluminate phase reacts rapidly with water and may cause undesirably rapid setting, if no seizure supervising added reagent commonly gypsum.

Alyumoferritnaya phase

Ferrite phase (CaAlFe) 5-15% of a conventional cement clinker. It - chetyrёhkaltsievy alumina ferrite 4CaO * Al2O3 * Fe2O3, the composition of which varies considerably when changing Al / Fe ratio in the structure and placement of foreign ions. The rate at which the ferrite phase is reacted with water, may vary somewhat due to differences in the composition or other characteristics, but usually, it is high in the initial period and is intermediate between the speed of alite and belite at a later date.

The clinker is typically present in small amounts of several other phases such as alkali sulfates and calcium oxide.

In Portland cement clinker is often 1-2% free CaO (free lime). The reasons may be: lack of training materials (roughly chopped or non-homogeneous raw meal), lack of temperature and firing time, resulting CaOnepolnostyu associated with other oxides, too slow cooling, when the partial decomposition of C3S and C3A, or too high saturation coefficient KH> 0,96-0,98). The polished sections of clinker free lime in the etching is visible in the form of colored particles from turquoise to blue. Often one can observe that the free lime occurs in the nests (Figure 1.2). This is due in most cases to poor homogeneity of the raw meal. Free lime is undesirable because it may cause (for example, in amounts of> 2.5%) non-uniform change in volume of cement, hardened cement stone can expand and cause cracks. Lime cracks occur due to increased volumes of approximately 2-fold when hydrated CaO with conversion to Ca (OH) 2. Saturated MgO clinker may contain free MgO - periclase. Since approximately 2,0-2,5% MgO as well as other ions can be introduced into the clinker phases, part of MgO can remain free and form periclase. The standardized cement according to EN 197 German industrial standard can contain a maximum of 5,0% MgO, a maximum of 2.5-3.0% of free periclase. The content of MgO, which binds to the other phases, depending on the chemical composition of clinker and its manufacturing conditions. The polished sections of MgO clinker in most cases occur in the hexagonal form. It is necessary to distinguish between emerging pink colored crystals of periclase from tricalcium silicate. Along with the different colors by etching it detects smaller size crystals, common jacks. They are somewhat uplifted and polished areas are extracted from the clinker as MgO has a higher hardness than the other phases of the clinker. Periclase is undesirable, since a higher content of hazardous magnesium (similar free lime) may occur. Harmful magnesia insidious, since the destruction of concrete products may appear only after many years. The finely crystalline and evenly distributed periclase expansion phenomenon is significantly less than in the coarse MgO or "nests" MgO. It is also typical for a free free lime.

 

Cement production

Most cement plants begin to feed the quarry where mined limestone (calcium oxide) and clay (oxides of silicon, iron and aluminum). D Depth can reach 100 meters, and the area - several dozen football fields. The raw material is crushed and mixed in a ratio of about 75% lime and 25% clay. The process of mixing the raw material mixture used to occur through mixing with water (slurry preparation - the so-called "wet" mode of production "). Now mainly used in the "dry method" of production, wherein the raw material mixture was prepared without mixing with water. This method can save up to 40 percent of the fuel (which was previously passed on subsequent drying of water), which significantly reduces the manufacturing cost of cement. There is also a combined method, or "semi-dry" method of production.

The obtained mixture was fed into a rotary searing oven where it is baked at 1450 ° C followed by quenching in air cooler. The output is a semi-finished product - the granules of up to 15 mm - so called cement clinker. The dimensions of the kiln at the wet process may be as high as 7 meters in diameter and 200 meters in length. In the dry method, the length of the furnace, typically less than 80 meters. The fuel for the clinker burning is usually natural gas. It is gaining popularity topic of alternative fuels such as used tires and rubber waste. Next is the step of preparing a proper cement from cement clinker - grinding in a grinding mill with the addition of gypsum (up to 5%, for adjusting the timing of cement) and mineral supplements (up to 30% depending on the brand of the resulting cement, slag, tripoli - to reduce costs). Incidentally, the grinding step is sometimes transferred to a separate independent production when purchased cement clinker and transported over long distances.

As a rule, cement factories, there are several production lines. For example, the plant capacity of 1.5 - 2.5 million tons can be up to 4 rotary kilns and cement mills to 6.

Ready cement is supplied to the warehouse - cement silos, and then sent to consumers, either in bulk hopper cars and cement trucks, or packaging - bags of 1 - 1.5 tons (big bags) and bags of 50 kg.

Limestone and clay

Limestone should meet the following requirements:

a) the content of calcium oxide (CaO) calculating the amount of calcium carbonate (CaCO3), the contents of which should be less than 75%;

b) the clay content is determined methylene solution in accordance with EN 933-9 and should not exceed 1.20 g / 100 g To test lime must be ground to a fineness of about 5,000 cm2 / g. Specific surface area is determined in accordance with EN 196-6.

c) the total organic carbon (TOC) for the EN 13639 test methods shall comply with one of the following criteria:

- LL: not exceed the mass fraction of 0.20%;

- L: must not exceed the mass fraction of 0.50%.

 

Izvestnyak- widespread monomineral rock composed of calcite; it can be easily determined by a violent reaction with hydrochloric acid. Due to the wide distribution, ease of handling and chemical properties of limestone is mined and used to a greater extent than other species, second only to the sand and gravel deposits. The limestones are of different colors, including black, but the most common breed of white, gray or have a brownish tint. The bulk density of 2.2-2.7. This soft rock, easy to scratch the knife blade. Limestone effervesce rapidly by reaction with a dilute acid. In accordance with its sedimentary origin has a layered structure. Net Limestone consists of calcite (rarely with a low content of other forms of calcium carbonate - aragonite). Present and impurities. The limestones are found in almost all continents except Australia. They were formed in different geological epochs. Seam Thickness varies from a few centimeters to hundreds of meters. The limestones are common in the United States and take up 75% of the country. In Russia, the limestone common in the central regions of the European part of, as well as common in the Caucasus, the Urals and Siberia. Limestone (in the broadest sense) have an extremely diverse range of applications. They are used in the form of lump limestone, crushed stone, piece (Saw, wall) and quarry stone, facing slabs, mineral crumbs, crushed sand, mineral powder, mineral wool, limestone powder. The main consumers - the cement industry (limestone, chalk, marl), construction (obtaining building lime, concrete, plaster, mortar, masonry walls and foundations; decorative-facing work, etc.), road and rail construction, rock placement for coastal protection and waterworks, metallurgy (limestone and dolomite - fluxes and refractories processing nepheline ore into alumina, cement and soda), agriculture (limestone flour in farming practices and animal husbandry), oil and coke, food (especially sugar), pulp and Paper, glass (limestone, chalk, dolomite), leather (limestone), rubber, cable, paint and varnish industry (chalk as a filler). Other areas of application - polishing products, non-ferrous metals and nacre (limestone), electric welding (chalk to cover the electrodes), writing chalk (chalk), insulation of building structures and technological equipment (mineral wool), etc.

Many cement plants use raw mixture of limestone and clay (or shale). Typically, these plants are being built in most limestone quarries and near the clay or shale deposits.

It should be borne in mind that not every limestone suitable for the production of portland cement. limestone deposits containing large admixtures MgC03, usually can not be used. Similarly, the presence of pyrite and gypsum inclusion can increase the content of sulfate in the cement, which is undesirable. There are deposits of chalk, littered with plenty of flint pebbles, in connection with which it is difficult to use for the production of cement.

In cases where the feed mixture to produce limestone is used with a high content of lime, it is necessary to mix with the clay-containing materials such chemical composition that could provide a given composition preparation of clinker.

 

Clay - sedimentary rock composed mainly of clay minerals; with water to form dough, dries able to maintain shape given to it, and get the hardness of stone after firing. Clay consists of one or more of kaolinite mineralovgruppy (derived from the area in China Kaolin), montmorillonite or other layered aluminosilicates (clay minerals), but may contain both carbonate and sand particles. Usually, rock-forming mineral is kaolinite clay, composition: 47% (by weight) of silicon oxide (IV) (SiO2), 39% of aluminum oxide (Al2O3) and 14% water (H2O).

Al2O3 and SiO2 - make up a large part of the chemical composition of yellow clay, brown, blue, green, purple and even black colors. Painting is caused by impurities of ions - chromophores, mainly iron valence of 3 (red, yellow) or 2 (green, bluish). The properties of clay: plasticity, fire and air shrinkage, fire resistance, caking, color ceramic crock, viscosity, shrinkage, porosity, swelling, dispersion. Clay is the most stable waterproofing - vodonepropuskaemost is one of its qualities. Due to this, the clay soil - the most stable type of soil developed on vacant lots and wasteland. Development of a plant root system clay deposits possible. Vodonepropuskaemost clay useful to preserve the quality of groundwater - a significant part of the quality of artesian springs lies between the clay layers.

Minerals contained in clays

• kaolinite (Al2O3 · 2SiO2 · 2H2O)

• andalusite, kyanite and sillimanite (Al2O3 · SiO2)

• Halloysite (Al2O3 · SiO2 · H2O)

• gibbsite (Al2O3 · 3H2O)

• Diaspora (Al2O3 · H2O)

• Aluminium oxide (Al2O3)

 

• Monotermit (0,2 [K2MgCa] 0 · Al2O3 · 2SiO2 · 1,5H2O)

• Montmorillonite (MgO · Al2O3 · 3SiO2 · 1,5H2O)

• Muscovite (K2O · Al2O3 · 6SiO2 · 2H2O)

• Cover (Al2O3 · SiO2 · 2H2O)

• Pyrophyllite (Al2O3 · 4SiO2 · H2O)

 

Proiskhozhdenie- main source of argillaceous rocks is feldspar, at which decay under the influence of atmospheric phenomena produced kaolinite and other hydrates of aluminum silicates. Some sedimentary clay formed in the process of local accumulation mentioned minerals, but most of them are deposits of water flows, dropped to the bottom of lakes and seas.

Clay - is a secondary product of the earth's crust, sedimentary rock, formed as a result of destruction of rocks during weathering.

application

• Pottery production,

• Technical ceramics,

• Production tsementa- for manufacturing cement is first extracted from limestone and clay quarries. Limestone (approximately 75% of the amount) was crushed and thoroughly mixed with the clay (about 25% of the mixture). The dosage of the raw materials is an extremely difficult process, as the lime content must meet the specified number of up to 0.1%.

These relationships are defined in the literature concepts of "lime", "flinty" and "aluminous" modules. Since the chemical composition of the starting raw materials is constantly fluctuating due depending on the geological origin, it is easy to understand how difficult it is to maintain the constancy of the modules. In modern cement plants is well established control with a computer in combination with the automatic analysis methods.

A legitimate slurry prepared according to the chosen technology (dry or wet method) is introduced into the rotary kiln (up to 200 m long and up to 2.7 m in diameter) and calcined at a temperature of about 1450 ° C - the so-called sintering temperature. At this temperature the starting material is melted (sintered), it leaves the furnace at a more or less large lumps of clinker (sometimes called Portland cement clinker). Firing occurs.

The clinker material formed by these reactions. Upon exiting the rotary kiln falls into the clinker cooler, where it is quenching from 1300 to 130 ° C. After cooling, the clinker is ground with a small amount of gypsum (6% maximum). cement grain size ranges from 1 to 100 microns. It is better to illustrate the concept of "specific surface area". If we sum the surface area of ​​the grains in one gram of cement, the cement grinding depending on the thickness are obtained value from 2000 to 5000 cm² (0.2-0.5 m²). The majority of the cement in special containers transported by road or rail. All overload produced pneumatically. A smaller part of the cement production is delivered in moisture- and razryvostoykih paper bags. Stored cement at construction sites mainly in silos.

• Application in medicine and cosmetology

The most common in nature are: red clay, white clay (kaolin), clay sandstone. Grades clay - for the production of porcelain, earthenware and refractory products - kaolin.

Level (6 points)

Reaction with cooling

An important process is the preparation of cement clinker it is cooled. From the rotary kiln clinker cooling zone out at a temperature of 1100... 1300 0C. Final cooling is carried out in its refrigerators.

Cooling the clinker has a significant effect on the structure, the mineralogical composition, grindability and thus the quality of the cement produced from it.

Primarily clinker cooling rate affects the ratio of crystalline and glassy phases. Slow cooling crystallization occurs, and with rapid - it slows down the formation of crystals and substantial portion of the melt solidifies in the form of clinker glass. The proportion of clinker melt in the rotary kiln is 20... 25%.

The rate of cooling affects the consistency of clinker cement volume change. Rapid cooling becomes large amounts of MgO in the glassy phase remain a microcrystalline state (grain size up to 5... 8 m). On slow cooling crystals of MgO increase in size, up to 30... 150 microns, which causes uneven changes in the volume of cement hardening. With a sharp firing and rapid cooling of the clinker formed small crystals alite, which increases the strength of the cement stone.

clinker cooling process also causes the chemical resistance of cement. Rapid cooling of the clinker increases cement sulphate. This is because C3A determining resistance clinker towards sulfate aggression by rapid cooling generally proceeds in a glassy form and becomes less sensitive to the effects against sulfates.

Grindability clinker depends on many factors, including the and the cooling rate. Comparison of grindability data quickly and slowly cooled clinker indicate that the clinker is cooled (slowly) in a drum cooler, requires higher energy consumption for grinding than clinker is cooled (fast) in a grate cooler. A higher content of the glassy phase and the small size of the crystals of clinker minerals grindability increases rapidly cooled clinker compared with cooled slowly. These data demonstrate the need for rapid cooling clinker.

Homogeneity of the raw meal

In the clinker burning process and fuel consumption affect the chemical composition, fineness of grinding, crystal size, nature of raw materials, the type and amount of impurities, the homogeneity of raw muki.Himichesky composition of the raw meal has a significant impact on the required firing time. It is defined as the time it takes to during firing the raw material mixture at a certain temperature the content of free CaO in the clinker should not exceed 2%. Oxides of alkali metals in larger amounts (about 2.5%) retard (inhibit) binding of lime during firing, while the content of MgO (about 2.0%) accelerates the firing.

The homogeneity of the composition of the raw meal is a necessary condition for the uniform clinker mineralogical structure and uniform operation of the kiln system. To do this, you must make sure that the raw material mixture in the smallest volume in the range (<1 mm3) is representative of a composition (thoroughly mixed, homogeneous). If the meal is poorly mixed, the clinker having "nest" of different phases, for example, free lime and belite clusters that formed in non-uniform material with valuable tricalcium silicate - alite. Using mineralizers (such as fluorspar, zinc oxide, manganese sulfide), the firing temperature can be lowered, and thus, can be achieved energy savings in the production of clinker.

Clinker cooler

In the cement industry for the final cooling of clinker after it leaves the cooling zone of the rotary kiln used refrigerators. clinker cooling mode affects the phase and mineralogical composition and it can therefore be regarded as an integral part of the process of clinker burning. The clinker is cooled by air entering the rotary kiln for burning fuel. Therefore, clinker coolers act as heat recovery boilers and improve the thermal efficiency of the furnace unit.

In Russia, 75% for cooling cement clinker and heat recovery in the furnace grate used refrigerators. This is, basically, two-chamber grate grate cooler type "Volga". Grate cooler unlike other heat recovery units, allow you to control the clinker cooling process or automate this process. In the United States, Japan and Western European countries used grate cooler with a number of chambers of three or more. The criteria for optimizing the following parameters can be selected: the maximum heat removal from grates or minimizing the output of clinker temperature.

The heat that is selected from the clinker cooler and partly returned to the furnace together with the secondary air, which is needed for combustion. According to different authors and producers of cement activities grate cooler automation can reduce fuel consumption needs for clinker firing by 2.5 - 5%. Automation of the cooling process can be one of the main and the first steps to improve production efficiency.

The most common clinker coolers are heat recovery (planetary), grates and drum (pipe). There are other types of refrigerators, but the extent of their application in industry are less significant.

Types of cooling drum depending on the cooling method of the processed material:

- Air cooled

- Water-cooled

- Tube refrigerators

-As Refrigerators, air-cooled material is cooled by air which is supplied in cocurrent or countercurrent fan.

-As Refrigerators with water cooling drum is irrigated outside water that has passed through the cooling bath. To increase the time of contact with a cooled wall of the material in the drum longitudinal shelves installed.

- Pipe refrigerator is an internal drum of the heat-resistant steel and an outer casing made of carbon steel. The inner drum mounted pipes. On the inner drum casing mounted guides, facilitating advancement of the product as the drum rotates. Upon rotation moves the product cooler the annulus and cooled in contact with the outer walls of the tubes. As a counter-tube space sucked air. The heated air is used in the lime burning kiln.

 

Storage of clinker

In order to have sufficient reserves (reserves) for grinding cement, clinker stocks are normalized. The stock is about a monthly productivity of the furnace. For this purpose, the closed space (capacity) to avoid dust emissions and a reduction in the quality of clinker due to weather conditions (rain, snow).

For storage of clinker in modern cement plants installed clinker stocks of various designs.

International AUMUND group developed a clinker storage depots of the following types:

- Round, without central support capacity of 3500... 156 000 tonnes;

- Cylindrical silos with a capacity of 5,000... 60,000 m;

- Round, with central support capacity 51000... 190000 tonnes;

- In-depth warehouses with a capacity of 45000... 201 000 tonnes;

(Bulk density clinker γ = 1500 kg / m3).

Round without central support clinker warehouse made of reinforced concrete, a cylindrical shape with a diameter of 40... 80 m, a height of 10... 25 m, the top cone

Cooler SF (Smidth-Fuller).

The basic principle of all types of cooling is that cooling air passes through the clinker layer on the grate and the cross-flow heated air completely or partially fed to an incinerator nozzle fuel supplied to the furnace. It is important clinker cooling mode selection, since the cooling mode and the quality depends on the microstructure of clinker. By optimizing the clinker cooling process created a good opportunity to improve clinker production at the lowest possible capital and operating zatratami.V JSC "Kokshe Cement" for the clinker cooling a refrigerator SF (Smidth-Fuller) cross output of 5500 tons / day. Grate area is 139 m2. Design feature of the refrigerator is mixed with the clinker via crossbars moving over the fixed grate, and the flow is controlled by motor controllers available in each reshetke.Kolosnikovye lattice modules in the refrigerator as well as in the inlet modules are mounted in the foundation. clinker is transported by a reciprocating compressor with crossbars, located on the line 50 mm above the grate. Each unit has a refrigerator 12 crossbars, 6 fixed and 6 mobile. Moving cross connected to two longitudinal profiles, which are actuated by a hydraulic cylinder, located under the grate, one for each module. a drive system connected to the unit drive system in the previous and next module. Settings "to the right" modules "in the middle" and "left" then can be moved independently of each other for optimum distribution and transport of clinker. Since reserved grates fixed bed of clinker, they, unlike the other contemporary refrigerators and will not wear out and degrade air distribution with a large amount of sealing air. Grate is made with labyrinth air path to avoid loss of clinker. Therefore, transportation equipment under the grate is missing. Grate has a low pressure drop. To ensure optimum air distribution grate, each equipped with a mechanical flow regulator (MPP). MPP maintains a constant flow of air through the grate and independent of the layer height clinker the clinker bed, the particle size distribution, temperature, etc.: a separate flow control for each of the grate. RAM allows one fan for relatively large areas and completely eliminates the use arranged under the grate tubes and louvers that are present in other modern refrigerators. SF modular principle allows the refrigerator factory assembly of large parts of the refrigerator and quick installation on the construction site.

Storage of clinker

In order to have sufficient reserves (reserves) for grinding cement, clinker stocks are normalized. The stock is about a monthly productivity of the furnace. For this purpose, the closed space (capacity) to avoid dust emissions and a reduction in the quality of clinker due to weather conditions (rain, snow). For storage of clinker in modern cement plants, clinker stocks set different konstruktsii.Mezhdunarodnaya AUMUND group for clinker storage warehouses has developed the following types:

- Round, without central support capacity of 3500... 156 000 tonnes;

- Cylindrical silos with a capacity of 5,000... 60,000 m;

- Round, with central support capacity 51000... 190000 tonnes;

- In-depth warehouses with a capacity of 45000... 201 000 tonnes;

(Bulk density clinker γ = 1500 kg / m3).

Round without central support clinker warehouse made of reinforced concrete, a cylindrical shape with a diameter of 40... 80 m, a height of 10... 25 m, the top cone. The top of the conveyor and mounted precipitators. Discharging clinker is carried out by 2... 4 channels.

Cement Grinding

clinker crushing

While the raw material mixture for the preparation requires two steps of cleavage - primary and secondary, clinker crushing is performed in a single operation and, moreover, not everywhere. Typically, the clinker discharged from the rotary kiln, is small, so that optionally crush it. In addition, when a two-stage grinding clinker pre-grinding it is produced.

Recently, however, are increasingly practiced by the special grinding clinker, which da'et opportunity to feed the mill for more uniform material size, improve its efficiency and to minimize fluctuations in the grind and mill performance. They do not need to be pre-split only such clinkers, which are highly uniform particle size.

But if clinker crushing is not always necessary, pre-grinding it plays an important role in grinding technologies. As in the raw material grinding, in this case, the mills of two types: centrifugal ball and which have different structures depending on the purpose. Some types of mills for the pre-crushing are characterized by low energy consumption, but expensive to operate; others have high performance at minimal cost to install and take up little space; others have good mechanical and performance characteristics, but do not provide the necessary grain composition of ground clinker, which may affect the quality of the final product - cement.

In the pre-grinding and final grinding of clinker should always bear in mind the construction properties of cement. This differs from the grinding of clinker grinding raw materials. In this case it is necessary not only to grind the clinker to a certain size, such as to obtain a product of the mineralogical and grain composition to the required chemical and physical characteristics of the 'cement were provided. In this regard, some plants are more willing to remodel the old, proven mill for pre-grinding clinker than establish new, although the costs are about the same. At one plant manufacturing high-early portland cement, it was found that when installing a new mill for pre-grinding of cement quality has deteriorated, although grinding is produced to the same surface area as before.

The final grinding

For final grinding of cement used is basically the same equipment as for the secondary grinding of raw materials, namely, tube mill and combined in different sizes. The two-stage in the grinding tube mills discussed above, is still the most common system for cement grinding. This system is very flexible and provides good grain structure of the finished product. With proper separation chamber otgtrtntr mill to corresponding selection double grinding bodies and grinding (if necessary) an optimal match between the preliminary and final grinding even in cases where the cements produced with different specific surface area. At two hundred-diynom grinding mill temperature is usually below ceteris paribus.

In order to provide greater flexibility of the grinding system, the application of multi-mills are increasingly used air separation. Fig. 24 shows a typical separator commonly used in cement plants.

Air separation makes it possible to produce cement with different fineness or specific surface at a constant load and the size of the grinding bodies. Also, when grinding from cage relatively hot material moves in a system with a large radiating surface, whereby its temperature is reduced significantly and improving the working conditions of the mill. In some plants to further reduce the temperature in the system is used water or air cooling mills and separators.

When grinding a clinker are added a few percent unfired gypsum to control the setting (such that the total content of SO3 in the cement was not more than 3%), and 15% granulated blast slag or active siliceous drbavok or up to 10% inert additives which, while not lowering practically cement quality, increase its amount, In the manufacture of blended cements

with more aktivnyx or inert additives can grind clinker and additive separately and as thin as possible, and then mix them.

Ready Portland - very fine powder is greenish-gray color. After exiting the mill it is still high Temperature (up to 120-130 °) and directed by conveyor or pneumatic pump to storage in silos. Soaking in the cement silos is necessary for cooling and quenching of free calcium oxide residues, which occurs under the influence of air vglagi. Cement silos maintained as long as the test it will not detect a uniform change in volume and have a normal setting time.

From silos cement is supplied to weigh out and pack

Milling equipment

Currently used for grinding cement and vertical tubular ball mill roll which can reduce power consumption compared with ball mills 25 to 40% [4, 100].

In order to improve grinding efficiency by about 50% using the press roller (roller presses) - High-pressure rollers (Figure 1.22). In cement plants Roller - press mainly used for pre-grinding clinker to cement grinding in a ball mill pulverizing [99].

Grinding the material in the press roller is made between two rolls rotating towards each other, which are compressed high pressure of about 150 bar. Material flows into the expansion box, the amount of material is regulated by the metering slide valve

Clinker is ground in a mill together with 4-10% gypsum (anhydrite). and other additives are introduced if necessary. Dosage is carried out by means of weight feeders or feeders.

Figure 1.23 shows a two-compartment mill construction company UMS FL SMIDTH to support housing and driven by the ring gear.

When the mill, especially in dry grinding, the bearing can be very warm by passing through a pin of hot material. The temperature coming out of the cement mill is 100... 150 ° C. There is also heated by friction bearings, especially in the case of dust. To cool the bearings provides their water cooling.

On the performance of tube mill the following factors:

- Grindability of the material (hardness);

- Size of food material;

- Fineness of the finished product;

- The range and weight of grinding bodies;

- Design and dimensions of the mill;

- Grinding technology used (open or closed loop, grinding aids, press rolls, etc.).

Clinker Grinding can be carried out in the open and closed tsikle. When grinding in an open loop whole material received by the mill exits therefrom as a finished product and can not achieve high udelnoy surface, increasing energy consumption for grinding, since a significant amount of fines accumulated in the mill.

Ready cement has a particle size range that impairs its properties. In open loop cements ordinarily is milled to udelnoy surface not more than 300 m2 / kg. To achieve a higher specific surface area is necessary in the process of grinding to separate fine particles, ie. E. Closed tsiklpomola apply. This izmelchaemy material passes through the separator, which separates the fine fraction, which is a finished product, and cereals Thanks to the timely removal of the fine fraction of mill finished product more uniform in composition granulometricheskomu contains significantly less major fraktsy that remain in the cement stone ballast, and have almost no influence on the strength. Grinding clinker in a closed loop can osuschestvlyat two schemes. Cement grinding process in a closed loop circuit is shown in Figure 1.24.

For this skhemeizmelchenny in the pipe mill clinker fed by bucket elevator and chanels in cages, where grit is returned to regrinding mill in the first chamber, and the finished product is supplied in silos. This scheme is simple and easy to use, it can be quickly translated into an open loop. High dispersion Material directed into the separator promotes effektivnosti last work as fine fractions increases yield and increased plant productivity. Lack of installation - increased power consumption due to some

Pozzolan (P, Q)

5.2.3 pozzolan (P, Q) 5.2.3.1 General pozzolan is a natural substance with silica or alumino-silicate composition tion or a combination of them. Although fly ash and silicate dust show putstsolanicheskie properties are described elsewhere (see para. 5.2.4 and 5.2.7). Pozzolans alone does not harden when mixing with water, but the water in finely divided or without react at ordinary temperature in the water with the dissolved Ca (OH) 2 with the formation of calcium aluminates and silicates. These compounds are similar to those that occur during hardening of hydraulic substances. Pozzolans consist essentially of reactive SiO2 and Al2O3. Balance being trivalent iron (Fe2O3) and other oxides. Mass the share of reactive CaO does not affect the curing process. Mass fraction of reactive SiO2 bodied should be at least 25%. Pozzolan must be properly prepared, ie After extraction homogenized, dried and crushed or burned. 5.2.3.2 Natural pozzolana (P) Natural pozzolans O are substances of volcanic or sedimentary origin of the corresponding chemical and mineralogical composition, which must comply with 5.2.3.1. 5.2.3.3 Natural calcined pozzolans (Q) Natural calcined pozzolans O are solid thermally activated substance kanicheskogo volcanic origin, clays, shales or sedimentary rocks, which must comply with 5.2.3.1.

Ash (V, W)

Fly ash is obtained by electrostatic or mechanical precipitation of dust-like particles from the flue gases of combustion plants micronized coal. The ash that is produced by other methods can be used in the production of cement if complies with EN 197-1, others - can not be used.

Fly ash is composed of glassy spherical particles with a diameter of 0.5-100 microns (see Figure 1.26). This latent hydraulic and their composition can be rich in silica and lime. The first of these has pozzolanic properties; the latter may additionally have hydraulic properties.

According to standards EN 196-2 the loss on ignition for 1 hour front fly ash should be no more than 5%. Fly ash with a loss on ignition of 5 to 7% by weight can also be acceptable, provided that certain requirements of strength, in particular to the frost in accordance with applicable standards or regulations for concrete and mortar are made. When used in the composition of cement fly ash with a loss on ignition of from 5% to 7% by weight, the upper limit of 7.0% should be indicated on the packaging and delivery of documents cement.

Level (8 points)

Fly ash rich in silica (V)

Fly ash is obtained by electrostatic or mechanical precipitation of dust-like particles from the flue gases of combustion plants micronized coal. The ash that is produced by other methods can be used in the production of cement if complies with EN 197-1, others - can not be used.

Fly ash is composed of glassy spherical particles with a diameter of 0.5-100 microns (see Figure 1.26). This latent hydraulic and their composition can be rich in silica and lime. The first of these has pozzolanic properties; the latter may additionally have hydraulic properties.

According to standards EN 196-2 the loss on ignition for 1 hour front fly ash should be no more than 5%. Fly ash with a loss on ignition of 5 to 7% by weight can also be acceptable, provided that certain requirements of strength, in particular to the frost in accordance with applicable standards or regulations for concrete and mortar are made. When used in the composition of cement fly ash with a loss on ignition of from 5% to 7% by weight, the upper limit of 7.0% should be indicated on the packaging and delivery of documents cement.

 

Field of the Invention -This invention relates to a high utilization of fly ash and in particular, the recovery process silica and alumina from fly ash, and more particularly relates to a method, wherein the first silica is recovered from fly ash, keeping Al ratio to Si, greater than or equal to 2, then known method, the metallurgical alumina, the remainder of which is used as a filler or for cement.

BACKGROUND-A large number of fly ash comes from power plants that burn coal, bringing serious pollution and losses to agriculture and natural ecology around the stations. Therefore, this project of high utilization of fly ash is an urgent need to translate.

Fly ash is also a source of minerals. Usually it contains approximately 15-40% Al2O3 and, for the most part, more than 40% SiO2, and fly ash with a high content of Al contains even greater than 40% Al2O3 and approximately 50% SiO2.

Lime ash dust (W)

Fly ash is also known as influenza ash is a residue produced in the combustion, and includes fine particles that rise with the flu gases. The ash, which does not increase, referred to as bottom ash. In the industrial context, fly ash generally refers to the ashes produced during the combustion of coal. Fly ash is generally captured by electrostatic precipitators or other equipment particle filtration before the flue gases reach the chimneys of power plants, coal-fired, and at the bottom ash removed from the furnace base, in this case, together known as coal ash. Depending on the source and coal burned structure, components of fly ash vary considerably, but all fly ash contains a significant amount of silicon dioxide (of SiO) (and amorphous and transparent) and slaked lime (CEO), both being local ingredients in many coal-bearing strata of rock.

In the production of hydraulic binder used slag mixture of different chemical and mineralogical composition with a high content of SiO2, and therefore its properties and applications is usually regarded with lime-pozzolan binder. However, as the artificial mineral additives, a mixture of ash and slag have a number of differences from the pozzolanic additive due to its high content of A12O3, CaO Fe2O3i, in their composition may not had time to burn from the combustion of the fuel and organic carbon. The presence of CaO is higher than 15% may impart ashes and slags obtained from the combustion of coal, the property exhibit hydraulic activity without introducing into it an alkaline curing activator or sulfate. The presence of these products aluminate and calcium aluminosilicate enhances the binding properties of ash and slag.

Similarly lime-slag binder content tszvesti in the lime-ash binder should be in the range of 15-30%; properties of this binder and scope similar to lime-slag binder.

One of the most active hydration is angry ash from the burning of oil shale - Kukersite containing up to 50% of CaO. Further crushing the ash exhibits pronounced cementing properties, and in the production of shale ash-Portland cement with fly ash content of 20-40% can be obtained cement marks 400, 500 and 600.

Calcined shale (T)

Slate is a bituminous, calcareous shales contain an average of 11-20% organic matter. Other major components are calcium carbonate (about 41%), clay minerals (about 27%) and quartz (about 12%). In Germany, the use of oil shale is concentrated mainly in the north-western slope of the Swabian Alps (region Dotternhausen in Baden-Württemberg).Goryuchy slate can serve both as a fossil fuel, as well as the clay component in the clinker burning process. When blowing in a special furnace at a temperature of about 800 ° C in a fluidized bed formed by a binder which has a hydraulic or pozzolanic properties. Formed with the heat of combustion is used to generate electricity. In accordance with the composition of the natural starting material containing combustible phase consists of slate klinkeroobrazuyuschih oxides, mainly silicon dioxide (SiO2), in addition it contains small amounts of free calcium oxide (CaO), calcium sulfate, and larger proportions of pozzolanic oxides. Accordingly, in a finely divided state, burned shale must be expressed hydraulic properties as portland cement and pozzolanic calcined shale svoystva.Soglasno requirements should, when tested in accordance with EN 196-1 achieved after 28 days compressive strength of at least 25.0 MPa. The test solutions can be obtained only with finely ground burnt shale cement instead. Samples after preparation of mortar prisms are up to 48 h., Then removed from the mold and stored until testing (testing) of not less than 90% in relative humidity. Degree of stretching (expanding) the calcined slate when tested in accordance with EN 196-3 using a mixture containing 30% of calcined slate with 70% of cement CEM I in accordance with EN 197-1, should be up to 10 mm

Limestone (L, LL)

Limestone should meet the following requirements:

a) the content of calcium oxide (CaO) calculating the amount of calcium carbonate (CaCO3), the contents of which should be less than 75%;

b) the clay content is determined methylene solution in accordance with EN 933-9 and should not exceed 1.20 g / 100 g To test lime must be ground to a fineness of about 5,000 cm2 / g. Specific surface area is determined in accordance with EN 196-6.

c) the total organic carbon (TOC) for the EN 13639 test methods shall comply with one of the following criteria:

- LL: not exceed the mass fraction of 0.20%;

- L: must not exceed the mass fraction of 0.50%.

 

Izvestnyak- widespread monomineral rock composed of calcite; it can be easily determined by a violent reaction with hydrochloric acid. Due to the wide distribution, ease of handling and chemical properties of limestone is mined and used to a greater extent than other species, second only to the sand and gravel deposits. The limestones are of different colors, including black, but the most common breed of white, gray or have a brownish tint. The bulk density of 2.2-2.7. This soft rock, easy to scratch the knife blade. Limestone effervesce rapidly by reaction with a dilute acid. In accordance with its sedimentary origin has a layered structure. Net Limestone consists of calcite (rarely with a low content of other forms of calcium carbonate - aragonite). Present and impurities. The limestones are found in almost all continents except Australia. They were formed in different geological epochs. Seam Thickness varies from a few centimeters to hundreds of meters. The limestones are common in the United States and take up 75% of the country. In Russia, the limestone common in the central regions of the European part of, as well as common in the Caucasus, the Urals and Siberia. Limestone (in the broadest sense) have an extremely diverse range of applications. They are used in the form of lump limestone, crushed stone, piece (Saw, wall) and quarry stone, facing slabs, mineral crumbs, crushed sand, mineral powder, mineral wool, limestone powder. The main consumers - the cement industry (limestone, chalk, marl), construction (obtaining building lime, concrete, plaster, mortar, masonry walls and foundations; decorative-facing work, etc.), road and rail construction, rock placement for coastal protection and waterworks, metallurgy (limestone and dolomite - fluxes and refractories processing nepheline ore into alumina, cement and soda), agriculture (limestone flour in farming practices and animal husbandry), oil and coke, food (especially sugar), pulp and Paper, glass (limestone, chalk, dolomite), leather (limestone), rubber, cable, paint and varnish industry (chalk as a filler). Other areas of application - polishing products, non-ferrous metals and nacre (limestone), electric welding (chalk to cover the electrodes), writing chalk (chalk), insulation of building structures and technological equipment (mineral wool), etc.

The quartz dust (D)

Quartz dust formed during production of ferrosilicon and silicon, quartz and carbon alloys in an electric arc furnace. It consists of very fine globular particles 0.02-1 microns in diameter containing amorphous silicon dioxide, at least 85%.

Quartz dust must satisfy the following requirements:

a) Loss on ignition (RFP) was measured according to EN 196-2 at 1 hour annealing time, the mass fraction of the SPT must not exceed 4.0%;

b) the specific surface area (BET) of untreated silica dust when tested in accordance with ISO 9277 should be at least 15.0 m2 / g;

For general use grinding clinker and calcium sulfate, silica dust in their original condition, compressed or compressed with addition of water to form granules.

Small components

 

Calcium sulphate

Sulfatkaltsiya (CaSO4) - inorganic compound, the calcium salt of sulfuric acid.

Located in nature in the form of dihydrate CaSO4 • 2H2O (gypsum, selenite) and anhydrous state - anhydrite.

Anhydrous calcium sulfate - colorless crystals under normal conditions - with the rhombic crystal lattice, the density of 2.96 g / cm³, melting point 1450 ° C. At elevated temperatures (above 1200 ° C) can exist in the form of a stable cubic or two metastable modification of α- and β-hexagonal modification. Very slowly adds water, hydrating crystalline to 1/2 or 2 molecules of water to 1 molecule of sulfate, respectively, CaSO4 · 0,5H2O and CaSO4 · 2H2O. Slightly soluble in water. The solubility decreases with increasing temperature, if at 20 ° C, it was 0.2036 g / 100 g of water, the water near boiling point (100 ° C) is reduced to 0.067 g of sodium sulfate per 100 g of water. Dissolved in water, natural calcium sulfate is one of the factors that determine the hardness of water.

The physical properties of the calcium sulfate dihydrate

When the temperature rises, but not more than 180 ° C, calcium sulfate dihydrate loses part of the water turning into a semi-aquatic - the so-called "plaster zhzhёny" fit for further use as a binder. Upon further heating to 220 ° C gypsum loses water to form the anhydrous CaSO4, which during prolonged storage only absorbs moisture and becomes hemihydrate. If firing is conducted at a temperature above 220 ° C, the obtained anhydrous CaSO4, which does not absorb moisture and have not "grasped" by mixing with water (this substance is often referred to as "dead gypsum"). Upon further heating to 900-1200 ° C can be obtained "hydraulic gypsum" which, after cooling properties regains contact with water. The first method partial degidratitsii used in industrial environments to obtain calcium sulfate hemi-hydrate (burnt gypsum, alabaster) CaSO4 ∙ 0,5H2O, heating the dihydrate to about 140 ° C, the reaction equation: CaSO4 · 2H2O = CaSO4 · 0,5H2O + 1,5H2O.

receipt

In industrial scale is produced as a part of natural minerals, such as gypsum, selenite or alabaster, or obtained synthetically - fusing CaCl2 with K2SO4.

In analytical chemistry, it can be obtained by the influence of sulfuric acid as the oxide, hydroxide, carbonate, oxalate or calcium acetate.

Formed by the oxidation of calcium sulfide when heated to 700-800 ° C by reaction of CaS + 2O2 = CaSO4.

Significant volumes of plaster used in construction (it is made from dry plaster, boards and panels for walls, gypsum stone, architectural details, etc.). Products made of gypsum are characterized by relatively low density, fireproof and relatively low thermal conductivity. Property plaster to harden when mixed with water and has been used in medicine, and the arts. "This is the property of gypsum is widely used in orthopedics, traumatology and surgery for the manufacture of plaster bandages which provide a record of individual body parts. Curing kneaded with plaster with water accompanied by a slight increase in volume. This allows for fine reproduction of all details of modeled forms that are widely used by sculptors and architects. "

The cement admixture

According to GOST 24640-81 Additives for cements are divided into 5 classes.

1. The components of the material composition (active mineral supplements).

2. Fillers.

3. Technology - grinding aids.

4. Control the basic properties of the cement:

- Setting time;

- Accelerate the hardening;

- Increasing strength;

- Increase the porosity of the cement - sandstone (air-entraining);

- Regulating the water-holding capacity;

- Increase the plasticity of cement-sand mortar (plasticizers);

- Reduce water wetting the surface of the cement particles.

5. Regulatory special properties of cement:

- Reduce heat;

- Regulatory and dimensional deformation;

- Increase the corrosion resistance;

- Coloring;

- Improving the decorative properties;

- Stabilizing (warning bundle);

- Sealing (bridging the pores)

- Enhancing the heat resistance.

Well cement

Designed for cementing oil and gas wells to protect them from the effects of groundwater. They are divided into cement for the "cold" (up to 40? C) and hot "(above 40? C) wells. Thus, the cement for the "cold" wells has increased the amount of C S and C, A, and for the "hot" - With the S and C AF. Start setting oil-well cements for the "cold" wells not less than 2 hours, the "hot" - 1 hour 45 minutes. They maintain high mobility, they have the ability to harden in conditions of high temperatures and pressures developed at great depths in the wells.