What is cement made from? What is cement made from? What is cement clinker

The word cement is familiar to everyone. Even those who have never been involved in construction know that cement is needed for mortar when brickwork that it is the main component of reinforced concrete products. However, few people know what cement is made from.

Peculiarities

Cement is ubiquitous. It is used not only in the construction of all kinds of buildings. You can’t do without it when carrying out restoration and repair work. There is no replacement for cement yet. This justifies its demand.

The basis of the building material is astringent inorganic components. Cement is necessary in the production of panel boards. Plaster and masonry mortars are made from it. Cement has one of the main places in the composition of concrete.

Essentially, cement is a fine powder. The main feature of the powder mass is that when interacting with water, it gradually begins to harden. The process of interaction between two components (cement and water) ends with the formation of a solid mass, similar in hardness to natural stone.

A strong structure is formed with excess moisture. The reaction occurs as outdoors, and in water. After hardening, cement retains its strength for a long time.

Properties

The physical characteristics of cement depend on several factors.

The most significant are:

• types of additives;
• grinding degree;
• compound.

The fineness of cement grinding affects the strength and time required for hardening. Fine grinding provides greater strength and faster hardening.

The smaller the powder particles, the stronger the concrete, the faster it sets. The cost of the material also depends on the degree of grinding.

To determine the fineness of grinding, a special sieve with the smallest cells up to 80 microns is used. When preparing a mortar from cement that is too finely ground, more water is required. This disadvantage is eliminated by mixing particles different sizes: large and small. Dust grains are considered large at 80 microns, and small at 40 microns.

Cement has the following properties:

• strength;
• corrosion resistance;
• frost resistance;
• water demand;
• setting (hardening) time.

Strength

This indicator depends on the brand. Strength properties are determined by performing compression tests. The experimental blank is kept under load for lunar month– 28 days. After testing the sample, the cement is assigned the appropriate designation. Strength is measured in MPa.

Cement grades 300 – 600 are suitable for household use. For products requiring special strength, higher grades are used – 700 or even 1000.

Corrosion resistance

Reinforced concrete products begin to corrode when exposed to water and other liquid media. The negative impact is eliminated in several ways. For example, you can change the composition and introduce hydroactive materials into the powder mixture. The presence of specific substances prevents the occurrence of harmful chemical reactions.

Corrosion resistance increases with the use of polymer additives. As a result, microporosity is reduced and the durability of products is increased.

Pozzolanic cement has the greatest corrosion protection. Therefore, it is used for the construction of structures operated in conditions of high humidity.

Frost resistance

One of the main indicators of cement quality is the ability to repeatedly freeze and thaw a concrete product.

Cement stone has micropores that contain water. When water freezes, it can increase in volume by 8%.

Repeated freezing and subsequent thawing over the years leads to destruction of the structure of the stone and the appearance of cracks.

Cement without additives is not used in construction. Different brands add components that give the cement the ability to resist temperature changes.

During the manufacturing process of concrete, additives that involve air are included in it. The smallest air bubbles are distributed evenly inside the concrete body, which solves the problem associated with water freezing and its expansion.

Water demand

This is the percentage of water required to produce cement mortar optimal consistency.

The solution of nominal thickness contains as much water as the cement can hold. For example, in Portland cement this value is in the range of 22-28 percent.

Cement with low water demand produces better quality concrete, than from the one for which this indicator is high. In the first case, the products are resistant to temperature changes. In the second, concrete has increased porosity and is not at all suitable for construction. This cement is used for the production of reinforced concrete fences or drainage structures.

Setting time

This is the time period per change physical properties cement mortar from the state of plasticity to the formation of stone.

The ideal solution is one that hardens not too quickly, but not too slowly. The setting time is regulated by the presence of a certain amount of gypsum in the material. A larger volume of gypsum ensures faster setting. While a decrease in its content contributes to a longer solidification of the solution.

Other factors do not affect setting as dramatically as gypsum. In particular, the volume of water in the solution and the ambient temperature in the working area are important.

According to the standard, under normal conditions, Portland cement begins to set after three quarters of an hour. The hardening process should be completed after 10 hours.

Compound

Cement is produced at specialized enterprises. Cement factories are built in close proximity to the places where raw materials are extracted.

The raw materials for its production are obtained from natural rocks:

• carbonate type fossils;
• clay materials.

Carbonates have an amorphous or crystalline structure, which determines the effectiveness of the interaction of the material with other components during the firing process.

Carbonate rocks include:

• marl (marly limestone);
• limestones, including shell rocks;
• dolomite type rocks.

Clay materials are sedimentary rocks. Possessing a mineral base, they are endowed with plasticity, and with excess moisture they can increase in volume. Clay materials are used in the dry manufacturing method.

Clay rocks include:

• clay;
• loams;
• clay-based shales;
• loess.

In addition to raw materials, corrective additives are used in the production of cement.

They are obtained from fossils, which include:

• apatites;
• alumina;
• fluorspar;
• silica.

Additives introduced using a certain technology improve the quality of the material being described.

The composition of cement depends on the required characteristics, which are determined by the grade assigned to the material.

The most popular Portland cement consists of:

• 60% lime;
• 25% silicon dioxide;
• 10% iron oxides and gypsum;
• 5% aluminum (alumina).

In different brands, the percentage of starting materials differs, as does the composition itself. For example, Portland slag cement contains slag. Quantitative proportions may also change depending on the characteristics of the chosen manufacturing technology for the building material.

For any brand of cement and for any method of its production, limestone and clay remain unchanged. Moreover, limestone is always three times more clay. This ratio contributes to the production of high-quality clinker, from which cement is made.

In industry, the following components are used to produce cement:

• clinker;
• gypsum;
• special additives.

Clinker is the most significant component of cement. It determines the strength qualities of the final material. Clinker enters the production process in the form of granules. The diameter of the granules varies between 10-60 mm. Heat treatment of the component is carried out at a temperature of about one and a half thousand degrees.

The amount of gypsum is determined by the established curing period. In the basic version, gypsum in powder form is included in cement in a volume of 6%.

Additives allow you to enhance specific characteristics. With their help, cement receives additional properties, which significantly expands its capabilities.

Production stages of cement production

First, limestone and clay are mixed in a ratio of 3/1. The mixture is then fired at high temperature. As a result, the starting material for producing cement is formed. It's called clinker. Granulated clinker is sent for grinding in ball mills.

There are three ways to obtain cement.

Depending on the manufacturing technology, it can be:

• wet;
• dry;
• combined.

The differences lie in the methods used to prepare the raw materials.

In accordance with wet technology It is not lime that is used, but chalk. Its mixing with clay and other ingredients occurs with the addition of water. The result is a mixture with a moisture content of 30 to 50 percent. The charge is converted into clinker balls during firing.

Using dry technology, the manufacturing process is shortened, since two operations (drying and grinding) are combined into one. The resulting mixture becomes powdery.

Different enterprises use the combined method in different ways. In some cases, a dry mixture is first obtained and then moistened. Others use not a wet, but a semi-dry method with low humidity not exceeding 18%. Firing is performed in both cases.

Kinds

There are many different variations of cement. The most famous is Portland cement.

Other material options are also quite popular:

• slag;
• pozzolanic;
• aluminous;
• expanding.

Portland cement is produced in several grades: 400, 500, 550, 600. Construction mortars are made from M400 cement.

Higher grades are in demand in the manufacture of reinforced concrete structures, as well as in the creation of high-strength concrete products.

White Portland cement is characterized by fine grinding. The composition includes low-iron clinker, gypsum and dolomite additives. It is characterized by high strength and resistance to precipitation. Products made from white Portland cement have an aesthetic appearance. Used in the manufacture of self-leveling floors, decorative elements, as well as during road construction. It is the basis for colored cements.

Sulfate-resistant Portland cement is used in the manufacture of piles, supports for bridges, hydraulic structures, anywhere where structures are repeatedly moistened and dried, where structures are subject to freezing and thawing.

The main purpose of slag cements is to create concrete products for structures located underground and under water.

Pozzolanic cements are needed in the construction of dams, river hydraulic structures, and various underground communications, as they are resistant to fresh water.

Aluminous materials are not afraid of sea waters, so they are included in reinforced concrete products that come into contact with mineralized waters. Can be used for urgent plugging of wells, including oil wells; when concreting in winter time; for fixing cracks in rocks.

The beauty of expanding cements is that when they set, they do not shrink, but, on the contrary, expand in volume. Increase in volume - from 0.2 to 2 percent.

How to do it yourself?

You can prepare cement at home if you can reach a high temperature for firing. Perhaps the most that can be obtained using a homemade method is cement grade M 200. You will need chalk and kaolin in a ratio of 3 to 1. About 5% of gypsum powder must be added to the burned and crushed substance - and the cement is ready.

For home production it will require appropriate knowledge, suitable raw materials, special equipment and precise execution of the technological process.

Even when everything you need is found, it is hardly worth engaging in cement production on our own. Before you start work, answer yourself the question about the feasibility of the process. It is unlikely that your work and expenses will pay off. Most likely, it is more profitable to simply buy a bag of ready-made cement.

When choosing cement for certain needs, remember that there are many varieties. The right choice for initial stage work will guarantee the durability of the building. You should not always give your choice to higher and more expensive brands. This will not increase the strength of the product, and the costs will not be justified.

See the video below for the process of obtaining cement.

Cement (Latin caementum - “crushed stone, broken stone”) is an artificial inorganic binder, usually hydraulic, one of the main building materials. When mixed with water, aqueous solutions of salts and other liquids, it forms a plastic mass, which then hardens and turns into a stone-like body. Mainly used for making concrete and mortars.

Cement is fundamentally different from other mineral binders (gypsum, air and hydraulic lime), which harden only in air.

Cement is obtained by heating slaked lime and clay or other materials of similar gross composition and sufficient activity to a temperature of 1450 ° C. Partial melting occurs and clinker granules are formed. To obtain cement, clinker is mixed with a few percent of gypsum and ground finely. The plaster controls the rate of setting; it can be partially replaced by other forms of calcium sulfate. Some specifications allow the addition of other materials during grinding. A typical clinker has an approximate composition of 67% CaO, 22% SiO2, 5% Al2O3, 3% Fe2O3 and 3% other components and usually contains four main phases called alit, belite, aluminate phase and ferrite phase. Several other phases, such as alkali sulfates and calcium oxide, are usually present in clinker in small quantities.

Alite is the most important constituent of all conventional cement clinkers; its content is 50-70%. This is a tricalcium silicate, Ca3SiO5, the composition and structure of which is modified by the placement of foreign ions in the lattice, especially Mg2+, Al3+ and Fe3+. Alite reacts relatively quickly with water and in normal cements plays the most important role among all phases. important role in the development of strength; for 28-day strength, the contribution of this phase is especially important.

The belite content for normal cement clinkers is 15-30%. This is dicalcium silicate Ca2SiO4, modified by introducing foreign ions into the structure and usually completely or for the most part present as a β-modification. Belite reacts slowly with water, thus having little effect on strength during the first 28 days, but significantly increases strength in later periods. After a year, the strengths of pure alite and pure belite under comparable conditions are approximately the same.

The aluminate phase content is 5-10% for most normal cement clinkers. This is tricalcium aluminate Ca3Al2O6, significantly changed in composition, and sometimes in structure, due to foreign ions, especially Si4, Fe3+, Na+ and K+. The aluminate phase reacts rapidly with water and can cause undesirably rapid setting unless a setting control agent, usually gypsum, is added.

The ferrite phase makes up 5-15% of ordinary cement clinker. This is tetracalcium aluminum ferrite Ca2AlFeO5, the composition of which changes significantly when the Al/Fe ratio changes and the placement of foreign ions in the structure. The rate at which the ferrite phase reacts with water may vary somewhat due to differences in composition or other characteristics, but is generally high early on and intermediate between the rates of alite and belite later in life.

The most widely used is Portland cement.

What types of cements are there?

Over the years since the advent of Portland cement, scientists have come up with and industrialists have introduced a huge number of new modifications. The family of Portland cements has grown and, in order not to be confused in their diversity, a special nomenclature has been developed. It is set out in the state standard of Ukraine DSTU B V.2.7-46-96 “Cements for general construction purposes. Specifications" All cements included in this document are united by the mandatory content of ground Portland cement clinker. Although its content can be quite low - in some cements it is only 20%, it is a basic, structure-forming component.

The classification of Portland cement and its “relatives” is based on two key parameters: type and amount of additive (or additives) and grade strength.

Depending on the additives contained, cements are divided into five types:

I Actually, Portland cement. Without additives or with a minimum amount of them (up to 5%). Designated PC I.

II Portland cement with additives: slag, pozzolan, fly ash, limestone. His index is PC II. To make it clear which additive is included in the composition, the corresponding letter is indicated to the right of the type designation (for slag - Ш, for pozzolana - P, for fly ash - З). In addition, the designation includes another letter indicating the maximum clinker content. If it is “A” - at least 80% clinker, if “B” - at least 65%.

Composite Portland cement belongs to the same type. It may contain several of the above additives at once. To distinguish it from Portland cement with additives, the designation was supplemented with the letter “K”. It turned out: PC II/A-K or PC II/B-K.

III Slag portland cement. As the name suggests, the material contains granulated blast furnace slag. And since slag itself has astringent properties, cement can “accommodate” much more of it than other additives. Accordingly, the clinker content in Portland slag cement is low: ShPC III with the letter “A” can contain only 35% slag, and with the letter “B” - even less: 20%.

IV Pozzolanic cement (may contain both pozzolan and fly ash). Designated PCC IV (“A” and “B”).

V Composite cement KC V (“A” and “B”). This cement, like composite Portland cement, may contain several additives, with the exception of limestone. The permissible minimum clinker content in it is lower than in composite Portland cement, and is at least 40% for letter “A” and at least 20% for letter “B”.

In terms of strength, DSTU B V.2.7-46-96 regulates grades 300, 400, 500, 550 and 600 for type I and II cements, and 300, 400 and 500 for other types.

In addition to the above symbols, symbol may contain additional information about the special properties of cement. For plasticized cements, the PL index is introduced into the designation, for hydrophobized cements - GF, for cements with high early strength - R.

For example, plasticized Portland slag cement grade 500, containing 40% slag and characterized by high early strength, will be designated as follows: ShPTs III/A-500R-PL DSTU B V.2.7-46-96.

Cement is included in many compositions: concrete, reinforced concrete, plaster, putty, masonry mortar. It is used in the construction complex structures, in underwater, underground construction, for autoclave materials.

Speaking about such a popular building material, one immediately remembers a homogeneous granular mixture gray. However, the definition will be inaccurate if it is not supplemented - this is an artificially obtained, inorganic binder. When interacting with water, it transforms into a fairly plastic mass, which subsequently hardens and becomes stone-like. Due to its ability to gain strength under wet conditions, it is classified as a hydraulic substance.

The grade of cement is the main indicator of its strength. There are many classes: M100, 150, 200, 250, 300 and even M600. But the brands from M350 to 500 are in greatest demand. The numerical value indicates what load 1 cm2 of the hardened composition can withstand. For example, the tensile strength of M400 in bending and compression is 400 kg/cm2.

What is the material made of?

Cement is made from 2 main elements: gypsum and clinker. The latter should be understood as the product of uniform firing of a raw material mass consisting of clay and limestone of a certain composition before sintering. Sometimes clinker may additionally contain marl, nepheline sludge, and blast furnace slag. With the introduction of mineral additives (up to 15-20% by weight), the properties change somewhat. The most common modifier impurities are: bauxite, pyrite cinders, sand, flue dust. If the content of additive substances exceeds 20%, pozzolanic cement is obtained, which is not afraid of interaction with sulfate and fresh waters.

The composition of the binder product is determined by the firing of the raw material mixture. Calcium oxides are formed from limestone at certain temperatures, which upon further heating enter into a complex reaction with clay components. As a result, compounds are formed that, after fine grinding and mixing with water, can harden and turn into a stone-like body.

Chemical composition:

1. CaO – calcium oxide 67%;
2. SiO 2 – silicon dioxide 22%;
3. Al 2 O 3 – amphoteric aluminum oxide 5%;
4. Fe 2 O 3 – iron oxide 3%;
5. foreign elements 3%.

Types of cement

The characteristics largely depend on the content of mineral compositions and the proportions of the components. In industrial and private construction, the most popular compositions are:

1. Portland cement.

It is a mixture of finely ground gypsum, cement clinker and corrective additives (tripoli, opoka, pyrite cinders) with a predominant proportion of calcium silicates (up to 80%). The greater its mechanical strength, and the sooner it is achieved, the higher quality the material is considered. In this regard, PC, which is characterized by a high increase in strength, is called rapid-hardening. It is called ultra-strong when it can withstand maximum compressive and bending loads. These characteristics are reflected in the marking. It is used in almost all areas, from building cladding to mass production of prefabricated concrete/reinforced concrete structures. Read about such an indicator as cement density.

2. Portland slag cement.

It is created by grinding a certain amount of gypsum, clinker and granulated slag (usually blast furnace - a product obtained by smelting cast iron in a furnace). The technology for manufacturing the binder implies the mandatory drying of waste from metallurgical production to a moisture content not exceeding 1%. Upon completion, the material is not as frost-resistant as ordinary cement, and it hardens more slowly. However, low cost and excellent resistance to sulfates make it popular.

Scope of use: cooking concrete mixtures, wall blocks, all kinds of mortars. It can be used when creating not only above-ground structures, but also underground ones that are exposed to mineralized/fresh waters.

3. Aluminous.

They are made according to a proven technology: the initial components are enriched with alumina - pure limestones and bauxites. The latter should be understood as rocks whose content is based on hydrates and impurities. The predominance of mono-calcium aluminate in the clinker composition is inherent. This determines the main characteristics: to set quickly, to be resistant to moisture, thermal influences, in particular, open fire.

Due to its water resistance, it is often used in winter. And thanks to its high hardening speed, it is indispensable for surgical emergency work. Another area is the production of various heat-resistant concretes based on it.

4. Magnesian.

The key difference is that the active component here is magnesium oxide. To obtain it, finely dispersed magnesite (or dolomite) is taken, which is subsequently subjected to calcination. The mineral itself, when dissolved with water, exhibits almost no astringent properties. But after diluting it with magnesium salts (sulfide/chloride), the final mixture acquires the necessary parameters and is quite suitable for construction work.

Famous for its good adhesion to various fillers, including organic origin, strength, low thermal conductivity. Thanks to such unique qualities, it can be used in the production of facing slabs, stair steps, partitions, thermal insulation products (foam, gas magnesite). But the main area is the installation of seamless monolithic floors.

5. Pozzolanic.

The production technology is based on the use of clinker, active additives (pozzolana - a mixture of volcanic ash, tuff, pumice; burnt shale; fly ash; microsilica), the proportion of which is 20-40% of the total mass. Additional additives may be included. Gypsum is poured in the amount necessary to regulate the setting time.

Pozzolanic composition differs from the classic composition in that it is characterized by higher resistance to corrosion and sulfate waters. Sufficiently frost-resistant, shows minimal heat generation during the hardening process. Due to the addition of light mineral additives, it has a lower specific gravity, but the same additives help to increase the yield of cement mortar. Most often used for the preparation of concrete/reinforced concrete products in underground/underwater structures. If we are talking about above-ground buildings in a dry climate, it is inappropriate to use it, since it will be much inferior to Portland cement.

Rarely used materials are romancement (a combination of clinker with dolomitized marl and gypsum) and acid-resistant products based on quartz/diabase, the mixing of which is carried out not with water, but liquid glass. White and colored compositions, on the contrary, are in demand, but only in the field of architectural finishing works.

Production technology

To obtain cement, the following steps are addressed:

1. heating the mixture of slaked lime and clay to temperatures + 1450-1480̊ C; at the end of this process, the necessary clinker granules are formed;
2. combining the intermediate product (clinker) with gypsum and further grinding it until it becomes powdery;
3. the introduction of additives and additives (if necessary), which will positively affect the properties.

In the manufacture of the binder composition, not only production processes are strictly observed, but also preparatory measures, the ratio of components. After the cement gets its finished look, it is transported to warehouses, where it waits for shipment to the consumer.

Cost of different brands

Many factors influence the formation of the final price:

1. packaging - it is more profitable to purchase in large volumes, so it is not surprising that a bag weighing 0.05 tons will cost less per 1 kg than a 5 kg package;
2. seasonality (active period) - spring/summer, part of autumn - the time when construction and repairs are in full swing, and, therefore, the rise in price of binders is not unreasonable;
3. territorial pricing policy;
4. manufacturer's prestige;
5. strength characteristics are the main aspect in determining cost: the higher the compressive strength limit of cement, the better quality it will be, and its price will be higher.

With aqueous solutions of salts and other liquids it forms a plastic mass, which then hardens and turns into a stone-like body. Mainly used for making concrete and mortars. Cement is a hydraulic binder and has the ability to gain strength in wet conditions, which is fundamentally different from some other mineral binders (gypsum, airborne lime), which harden only in air.

Cement for mortars- low-clinker composite cement intended for masonry and plaster mortars. It is produced by joint grinding of Portland cement clinker, active mineral additives and fillers.

Historical information

• Romancement - predominance of belite, currently not produced;
• Portland cement - predominant alite, most widely used in construction;
• aluminous cement - predominance of the aluminate phase;
• magnesia cement (Sorel cement) - based on magnesite, sealed with an aqueous solution of salts;
• mixed cements - cements obtained by mixing the above cements with air binders, mineral additives and slags with astringent properties.
• acid-resistant cement - based on sodium hydrosilicate (Na 2 O mSiO 2 nH 2 O), a dry mixture of quartz sand and sodium silicofluoride, mixed with an aqueous solution of liquid glass.

In the vast majority of cases, cement refers to Portland cement and cements based on Portland cement clinker. At the end of the twentieth century, the number of varieties of cement was about 30.

Based on strength, cement is divided into grades, which are determined mainly by the compressive strength of halves of prism samples measuring 40*40*160 mm, made from a 1 to 3 cement solution with quartz sand. Grades are expressed in numbers M100 - M600 (usually in increments of 100 or 50) indicating compressive strength of 100-600 kg/cm2 (10-60 MPa), respectively. Currently, cement grade M300 or less is not produced. Due to its strength, cement with grade 600 is called “military” or “fortification” and costs significantly more than grade 500. It is used for the construction of military facilities such as bunkers, missile silos, etc.

Also, cement is currently divided into classes based on strength. The main difference between classes and brands is that strength is not derived as an average indicator, but requires at least 95% security (that is, 95 samples out of 100 must correspond to the declared class). The class is expressed in numbers 30-60, which indicate compressive strength (in MPa).

Production

Cement is produced by finely grinding clinker and gypsum. Clinker is a product of uniform firing before sintering a homogeneous raw material mixture consisting of limestone and clay of a certain composition, ensuring the predominance of calcium silicates.

When grinding clinker, additives are introduced: gypsum CaSO 4 ∙ 2H 2 O to regulate the setting time, up to 15% of active mineral additives (pyrite cinders, flue dust, bauxite, sand, opoka, tripoli) to improve some properties and reduce the cost of cement.

The firing of the raw material mixture is carried out at a temperature of 1470°C for 2-4 hours in long rotary kilns (3.6x127 m, 4x150 m and 4.5x170 m) with internal heat exchange devices to simplify the synthesis of the necessary cement clinker minerals. Complex physical and chemical processes occur in the fired material. The rotary kiln can be divided into zones:

• heating (200...650 °C - organic impurities burn out and the processes of dehydration and decomposition of the clay component begin). For example, the decomposition of kaolinite occurs according to the following formula: Al 2 O 3 ∙2SiO 2 ∙2H 2 O → Al 2 O 3 ∙2SiO 2 + 2H 2 O; further, at temperatures of 600...1000 °C, aluminosilicates decompose into oxides and metaproducts.
• decarbonization (900...1200 °C) decarbonization of the limestone component occurs: CaCO 3 → CaO + CO 2, while the decomposition of clay minerals into oxides continues. As a result of the interaction of basic (CaO, MgO) and acidic oxides (Al 2 O 3, SiO 2) in the same zone, processes of solid-phase synthesis of new compounds begin (CaO∙Al 2 O 3 - abbreviated form of SA, which at more high temperatures reacts with CaO and at the end of liquid-phase synthesis C 3 A is formed), proceeding in steps;
• exothermic reactions (1200...1350 °C) the process of solid-phase sintering of materials is completed, here the process of formation of such minerals as C 3 A, C 4 AF (F - Fe 2 O 3) and C 2 S (S - SiO 2) - 3 is completed of the 4 main minerals of clinker;
• sintering (1300→1470→1300 °C) partial melting of the material, clinker minerals pass into the melt except C 2 S, which interacts with the CaO remaining in the melt to form the mineral ALIT (C 3 S);
• cooling (1300…1000 °C), the temperature drops slowly. Part of the liquid phase crystallizes with the release of crystals of clinker minerals, and part freezes in the form of glass.

World cement production

In 2002, world cement production reached 1.8 billion tons. The three largest producers included China (704 million tons), India (100 million tons), and the USA (91 million tons).

The price of cement on European exchanges is about $100 per ton. Cement prices in China are about $40 per ton. The majority of exchange transactions in cement in Russia for 2010 are carried out on the Moscow Stock Exchange.

Sources

Reichel V., Konrad D. Concrete: In 2 parts. Part 1. Properties. Design. Trial. - M.: M.: Stroyizdat, 1979. P. 33. Trans. from German/Ed. V. B. Ratinova.

• Dvorkin L.I., Dvorkin O.L. Handbook of construction materials science. - M.: Infra-Engineering, 2010.

see also

Notes

Links

Wikimedia Foundation. 2010.

See what “Cement” is in other dictionaries:

cement- a, m. ciment m., German. Zement, Cement, goal. cement lat. caementum broken stone. 1. The outside walls of the sluices, only an arshin and a half or less, are lined with cut stone and greased with cement, and then laid with field stones and lime. 1725. Tatishchev... Historical Dictionary Gallicisms of the Russian language

The quality of any artificial binder is determined by its manufacturing method and the percentage of raw materials. Cement is no exception; of all types, it is one of the most complex. This substance is obtained by grinding gypsum and burnt homogeneous multicomponent clinker to a powder state and combining them with special additives. As a result, the properties and scope of the binder depend on the ratio of these substances to each other, the processing temperature and the fineness of grinding.

Groups of cements by composition

The main components are oxides of aluminum, calcium and silicon, when mixed with water, they form chemical compounds that harden when solidified in a humid environment. General requirements are regulated by GOST 30515-2013; according to this interstate standard, all cements are classified into groups that differ according to the type of clinker: Portland cement, aluminous and mixed (PC and sulfatoaluminate). In the first case, the typical composition contains CaO (67%), SiO 2 (22%), Al 2 O 3 (5%), Fe 2 O 2 (3%) and up to 3% foreign substances.

For the production of aluminous and high-alumina cements, bauxite and limestone are used as raw materials (the share of low-basic calcium aluminates predominates, the percentage of Al 2 O 3 increases to 50%). The ratios of the remaining components depend on the intended purpose and vary within the following limits: CaO - 35-45%; A1 2 O 3 - 30-50%; Fe 2 O 3 - 0-15%; SiO 2 - 5-15%. For the production of sulfate-containing mixtures, clinkers based on calcium ferrites are used.

Depending on the proportions of the components and the material composition, the following groups, in demand in private and industrial construction, are distinguished:

• Portland cement is the most popular variety, representing a mixture of finely ground clinker with a predominant proportion of highly basic calcium silicates and gypsum. The raw materials are limestone (up to 78%) and clay (up to 25%).
• Aluminous, made by grinding raw materials from bauxite and limestone, burned or melted to a homogeneous state. These types are characterized by a high rate of hardening; they are used both as an independent binder and for the production of special grades: waterproof, expanding, tensile. Due to the increased hardness of clinker, they are inferior to Portland cement in energy consumption and cost.
• Portland slag cement – ​​with a proportion of blast furnace, electrothermophosphorus or fuel slag from 36 to 65%.
• Pozzolanic, with the addition of active mineral additives to the PC clinker grinding products. Their proportion reaches 40%; due to the formation of chemical reactions with cement grains, they have properties different from conventional brands.
• Mixed - obtained by grinding clinkers together different types or by introducing multicomponent mineral mixtures (for example, slag and fly ash).

Less commonly used types include romancement (a combination of grinding PC clinker and limestone and magnesia marls, not produced on an industrial scale), magnesia (mixed with saline solutions, characterized by a high setting speed and resistance to mechanical loads after hardening) and acid-resistant compositions based on quartz, diluted with liquid glass.

Chemical composition of cements of different groups

Proportions of clinker and other components:

The scope of application and main properties of the varieties are given below:

Main brands

The type of binder chosen determines the proportions and properties of building mixtures. It is important to check in advance what the cement consists of, its water demand, grain size and setting time. The main quality criterion is the compressive strength, in the laboratory it is determined for products from CPR, mixed in a ratio of 1: 3 and hardened under normal conditions for 28 days. Depending on the pressure withstand, groups from 100 to 600 kg/cm 2 are distinguished. Of these, brands from M300 to M500 are most in demand in private construction, but there are exceptions.

The next factor is the percentage of additives to clinker; for standard types the maximum is 20%. The marking of this indicator is indicated by the letter “D”, the number following it characterizes the proportion of mineral impurities (example: PC M400 D0 is indicated for Portland cement with a compressive strength of at least 400 kg/cm 2 without additives). The given marking corresponds to GOST 10178-85; in addition to the above, it includes information about additional properties (indicated only if available), also depending on the composition of the clinker and the additives introduced. Of these, the most in demand are:

• H - normalized;
• B - fast hardening;
• SS - sulfate-resistant;
• VRTS – expanding waterproof;
• PL - with plasticizers;
• BC – white (decorative) cement.

Since 2003, GOST 31108 (corresponding to European standards) came into force, according to which the composition is first indicated with a note about the presence or absence of additives (II or I). All options with mineral impurities are divided into two groups: A - with a percentage content from 6 to 60%, B - from 21 to 35%. The type of additive is indicated by Roman numerals. The last ones are the strength class and compression rate of the material. The standard range for general construction mixtures varies from 22.5 to 52.5 (corresponding to grades from M300 to M600). To avoid errors, GOST is always indicated next to the marking; the introduction of cement is carried out in strict compliance with proportions.