The cement industry is one of the most important branches of material production. The importance of this industry in national economy is determined primarily by its inextricable connection with the progress of capital construction. Cement is one of the most important building materials for the manufacture of concrete, reinforced concrete products, as well as for fastening individual parts of building structures, waterproofing and many other purposes.

Last summer, I filmed at the Lafarge ("Uralcement") plant located in the village of Pervomaisky, Chelyabinsk region... The plant has been producing cement using the wet method since 1957 and is one of the ten largest cement plants in Russia in terms of production volumes. Clay and limestone are used for the production of cement. The fuel is natural gas.

The history of Portland cement begins on October 21, 1824, when the English bricklayer Joseph Aspdin received a patent for a substance he called Portland cement because its color was reminiscent of the gray rocks around the city of Portland.

Portland cement is a hydraulic binder obtained by joint fine grinding of Portland cement clinker, gypsum and special additives. The properties of Portland cement depend on the composition of the clinker and the degree of its grinding. The most important property Portland cement - the ability to harden when interacting with water. It is characterized by a brand of Portland cement, determined by the compressive and flexural strength of standard samples cement-sand mortar after 28 days of curing in humid conditions.

2. Cement production consists of two main technological processes: obtaining clinker (the most labor-intensive and energy-consuming stage) and grinding it with appropriate additives.

3. To make cement, limestone and clay are first extracted from a quarry.

6. After pre-processing, the raw materials enter the wet autogenous grinding mill "Gidrofol", where they are processed into sludge. Then the sludge is crushed in raw mills and averaged in slurry tanks.

7. There is a special laboratory at the plant, where they carry out constant quality control and dosage of raw materials and additives. And including testing the end product for strength.

11. Then the finely ground raw sludge is introduced into a rotary kiln (about 200 m long and 4 m in diameter) and fired at a temperature of 1450 degrees Celsius.

12. During firing, the particles of raw materials are fused together to form clinker.

13. The kiln is a rotating metal cylinder that is tilted to the horizontal plane at an angle of 3-4 degrees to allow material to move along the kiln.

14. The resulting clinker is cooled in refrigerators, crushed and fed by conveyors to the hoppers of cement mills for grinding.

15. Electrostatic precipitators on rotary kilns can reduce dust emissions into the atmosphere by 10-30 times.

18. The cooled clinker is fed to the mill.

20. This is the noisiest production area. It is simply impossible to be in the shop without headphones.

21. Cement is obtained by joint fine grinding of Portland cement clinker, mineral additives (10-15%) and gypsum (3-7%), which serves to regulate the setting time. The grain size of the cement ranges from 1 to 100 microns.

24. Procedure LOTOTO (LockOut / TagOut / TryOut). A set of actions to improve industrial safety.

25. Various mineral additives are used to impart special properties to concretes, mortars and other cement-based products (speed of hardening, stability in natural waters, frost resistance).

28. The resulting Portland cement is transported from the mills to storage silos.

29. Cement is shipped from silos by railroad cars and road transport in the following form: in bulk, in special containers of large-size capacity up to 1 ton, paper bags weighing 50 kg.

Judging by the scale of application of mortars and concretes based on mineral binders in construction, it seems that the history of artificial stones based on cement goes back many centuries. But a truly proven production technology and the optimal composition of cement became known less than two centuries ago.

Stone invention

The stones of houses from prehistoric times were fastened in the wall with the help of clay, but they could not survive without firing, and the most ancient buildings that have come down to us were erected with the use of lime mortar. Burnt and crushed limestone (calcium oxide - Ca (OH) ₂) after mixing with water hardens, absorbing carbon dioxide from the air, and then again turns into stone. The main disadvantage of a lime binder is its low moisture resistance, so today it is used more in the manufacture of silicate bricks.

Another type of air mineral binder (that is, gaining strength in air) is gypsum. It is obtained by heat treatment and subsequent grinding of natural gypsum stone (CaSO 4 -2H 2 O) or natural anhydride (CaSCu). Gypsum binder has a huge history of use from ancient times to the present day. The most striking examples are luxurious stucco and sculptural decorations, sheet materials(GVL, GKL) for dry construction and finishing methods.

Hydraulic binders

The scope of application of air binders is limited to those places where ready-made structures not exposed to moisture, in otherwise it is necessary to use water-repellent (water-repellent) additives or carry out waterproofing measures, therefore the use of hydraulic binders is more convenient and widespread.

These include substances that form hydration (a water molecule enters the crystal lattice as component) connections, when transformation into a stone-like body and further strength gain can occur in a humid environment, and the effect of water during the operation of structures does not lead to their destruction.

Mortars and concretes for the implementation of waterproof structures are prepared on the basis of hydraulic lime (from sedimentary lime rocks of a special composition - marls) and Portland cement, and it is the latter that gives the monolithic and prefabricated elements of the building the necessary strength, and lime mortars used where the loads are minimal.

History of cement

Attempts to overcome the low water resistance of lime and gypsum compositions have been made since ancient times. Cement (caementum in Latin - crushed, broken stone) appeared by adding various minerals with hydrophobic properties to lime. For this, crushed remains of baked clay bricks and various volcanic rocks were used. So, in the composition of cement, which was used by builders Ancient rome, included pozzolans - ash deposits of the famous Vesuvius volcano.

The experiments continued for many centuries, while the need for a large number durable and inexpensive binder did not force builders to develop optimal technology for its production. A decisive contribution to such research was made by the Russian military technician Yegor Cheliev, who published a book on cement for underwater work (1825), and the bricklayer from English Leeds, John Aspdin, who received a patent for Portland cement (1824). This name comes from the English island of Portland, located in the English Channel and consisting of limestone rocks. The stones from a quarry located on this island were considered the most prestigious building materials in England. Received by Aspdin fake diamond was very similar in color and strength.

Interestingly, Cheliev's technology is more in line with what is now called Portland cement, and Aspdin's cement was manufactured without the sintering of the raw material now accepted.

Production technology

Cement binder different manufacturers may differ in raw materials, but the main technological operations are identical. The first stage is the preparation of the initial mineral raw materials, i.e. several stages of grinding lime stones and clay, mixing these components in the right proportions. What is cement made of? Usually it is 3 parts by weight of limestone and 1 part of clay. Sometimes a sedimentary rock is used - marl, where these components are contained in the right proportion.

"Dry" and "wet" method

There are two ways to obtain the desired state of the mixture: "dry" and "wet". If the moisture content of the components is high, clay and soft limestone (chalk) dissolve in water, then water is removed from this suspension, called raw sludge, by strong heating (evaporation). A uniform, finely ground mixture is obtained. A more economical method is "dry", where there is no stage of bringing the sludge to a boil, and the mixture is crushed mechanically.

Further, in rotary kilns - cylinders with a diameter of about 5 m, a length of about 200 m, with a slope for moving the raw material during the firing process, clinker is formed - rounded granules that appear during the sintering of the mixture at a temperature of 1450 ° C as a result of physical and chemical interactions.

The clinker is cooled and aged for up to two weeks before the final operation - joint grinding with a certain amount of gypsum, which is added to slow down the setting process. Here the composition of the cement is finally formed, at the same stage various mineral additives are introduced, giving the binder the desired specific properties.

Chemical base

The required properties of the most popular binder determine chemical composition cement. As a result technological processing raw material clinker becomes a combination of various chemical substances in the form of four main minerals:

1. Alite - tricalcium silicate - makes up most of the clinker - 50-60%. The presence of manganese, aluminum and iron ions in the molecular lattice determines the strength of the finished solution or concrete mix, recruited during the first 28 days.
2. Belite - dicalcium silicate - is 15-30%, and it is the basis of the strength gained by the structure at a later date.
3. Aluminate phase - tricalcium aluminate - 5-10%. The rapid reaction of the aluminate with water and the possible setting too quickly require the introduction of gypsum, which slows down this process.
4. Ferrite phase - tetra calcium alumoferrite - 5-15%

By changing the percentage composition of these phases, introducing additional components, it is possible to produce cement, the composition and properties of which will best match specific situation during construction.

Types of cement

Portland slag cement is obtained by adding granulated slag to Portland cement clinker, a by-product of pig iron smelting in blast furnaces. The use of slag reduces the cost, and the composition of the cement produced using this technology gives structures made on its basis, increased resistance to the effects of water with a saturated mineral composition, for example, sea.

Fast-hardening is a cement with a predominance of alite and aluminate phase in the clinker, it is distinguished by an especially fine grinding - all this accelerates the set of strength.

Sulphate-resistant Portland cement is used for hydraulic structures, the underwater parts of which are constantly exposed to substances that cause sulphate corrosion. What does the cement intended for such critical structures consist of? In clinker raw materials, the presence of tricalcium aluminate and belite is minimized.

Portland cement with reduced heat generation during strength development is necessary for the manufacture of structures of large mass and volume, when the heat released by the exothermic hardening reaction can lead to cracking. The composition of such cement is similar to sulfate-resistant.

White cement

Products made with white cement have enhanced aesthetic qualities. The presence of iron oxide and manganese oxide in the feedstock gives the finished powder a characteristic gray-green color, respectively, the composition of white cement assumes the minimum presence of such salts and the use of light, kaolinic clay grades for the feedstock.

There are many more types of cement binder with special properties: hydrophobic, aluminous, waterproof expanding, tensile, plasticized, sandy, etc.

Composition and strength

The most important indicator of the quality of cement is the strength of products made on its basis. GOST established the necessary indicators, which are indicated by special marking. The number means the ultimate strength in bending and compression in laboratory tests of reference materials, the load resistance of which is also influenced by the composition of the cement. M400 means that the samples withstood a load of 400 kg / cm² (or 40 MPa).

Research shows that the mineral composition of the feedstock is the most important factor affecting strength cement mortars and concrete. Correct selection components allows you to find the right proportion between the rate of strength development and the final value of resistance to loads, which only increases over time. The composition of M500 cement allows you to create beams and slabs that can withstand colossal loads.

Today the world produces great amount cement of the most varied quality. The choice of raw materials for it is often determined by economic factors, and with the right attitude to the construction process, you should know what the cement consists of, which will be used in order to make the right choice and be confident in the strength and durability of the future home.

In the construction of industrial facilities, the construction of residential buildings, the production of finishing and repair measures, various building mixtures are used. These include cement, which is a binder. It has unique characteristics and, despite the emergence of new building materials, has no analogues to this day. It is difficult to tell everything about cement in a short article. At the same time, we will try to provide detailed information on the composition, properties, varieties and production technology.

What is cement

Many have heard the word "cement". The definition of this term can be found in specialized sources. Cement, indispensable in the construction industry, is a dry powdery substance of inorganic origin. It is made by high-temperature firing of a lime-clay mixture containing these components in certain proportions. The resulting building material has special performance characteristics.

When water is added, it changes properties:

• becomes viscous (pasty consistency);
• takes on a dark gray tint;
• rapidly gains hardness in air and humid environments;
• turns into a stone of artificial origin.

Everybody who used cement was repeatedly convinced that it is a sufficiently strong building material. Artificial monolith in hardness is not inferior to natural stone.

It is difficult to imagine a construction area where no cement would be used.

The building material has ancient history... There is no reliable information about cement in the sources. Who invented it first is unknown. Historians also find it difficult to give an unambiguous answer to the question of where cement was invented. As a result of excavation and scientific research ancient cement has been studied many times. When was it invented? Scientists have tried to answer this question. They concluded that the material appeared long before our era. This is confirmed by the different countries samples. They contained gypsum, lime, and even volcanic ash.

The methods of making cement have changed over the millennia. Binders with reduced strength have gradually lost their relevance. They were replaced by clinker obtained by firing, as well as special modifying components.

Composition

The complete chemical formula of the building material is rather complex. It contains the following substances:

• calcium oxide in the amount of 67%;
• silicon dioxide in the amount of 22%;
• aluminum oxides of the order of 5%;
• iron oxide, the content of which is 3%;
• modifying components - no more than 3%.

The building material is based on the following ingredients:

• clinker made from clay and limestone. Strength properties depend on the quality of clinker. Clinker is the main component produced by heating a lime-clay composition in a rotary kiln. During firing, clay-containing raw materials and limestone materials are melted to form granules saturated with silica. Then the clinker is re-annealed and crushed to a dusty state;

Until now, analogues of this building material have not yet been found, which indicates the unique properties of cement.

• components of mineral origin. The introduction of special additives expands the scope of application, increases the performance characteristics, and gives the necessary properties. Granular slags, crushed shale materials, pozzolanic ingredients and crushed lime are added. In the normative documents regulating the composition of building materials, there is information about the content of various chemical substances in the mineral components;
• special additives and auxiliary components containing calcium sulfate. The addition of these ingredients does not affect the rate of moisture absorption and the duration of use of the working mixture. Changing the concentration of calcium sulfate, which is part of the modifiers, allows you to adjust the duration of the hydration process within the required limits. For this, gypsum powder is added.

In addition to the indicated main components, special additives are introduced that increase the resistance of the cement composition to high temperature, to the action of acids, alkalis, corrosive environments. The additives also increase moisture resistance, improve adhesion to steel reinforcement, and also affect the flowability of the cement slurry.

In dry form, it is a free-flowing homogeneous mass of gray color

Main characteristics

The use of cement is related to its properties. The current standard regulates the following characteristics:

• strength properties. They vary for different brands of cement compositions. Strength is determined laboratory method by compressing a reference sample of the solidified mixture. Strength control in accordance with the requirements of the regulatory document is carried out in three stages: after two days, as well as one and four weeks after pouring. The value of the parameter is measured in megapascals. The numerical value of the strength corresponds to the brand of the cement composition;
• setting duration. The parameter characterizes the time interval during which the plastic characteristics change cement mix... A properly prepared solution begins to solidify a couple of hours after pouring in the hot season. In the autumn, the hydration process can take 8–10 hours. The setting time at zero temperature increases sharply and can be 15–20 hours. The introduction of additives allows you to adjust the setting speed;
• resistance to impact negative temperatures... This characteristic is called frost resistance. It characterizes the ability of the hardened cement mass to perceive deep freezing with further thawing over many cycles. At the same time, the integrity of the massif and strength characteristics must be preserved. The cause of destruction is an increase in the volume of water saturating the pores. The introduction of additives increases the frost resistance threshold;
• density. The parameter characterizes the mass of a powdery substance in one cubic meter material. Freshly prepared cement composition has the smallest specific gravity... During long-term storage, the material is caked, and during transportation, it is compacted. At the same time, the density increases. The characteristic depends on the size of the crushed clinker. The average value is 1.3 t / m3.

After the cement hardens, a strong connection is formed, which is not inferior in its density to stone

Other characteristics include:

• hygroscopicity. The degree of water absorption is different for different brands;
• grind size. Determined by sieving through a sieve;
• corrosion resistance. Increased by the introduction of special additives;
• shelf life. It depends on storage conditions and acceptable level humidity.

Quality decreases after long-term storage in a warehouse with high humidity. When purchasing building materials, pay attention to the presence of a certificate of conformity, which guarantees the quality of products.

Varieties of material

The construction industry uses different kinds cement materials with the following parameters:

• composition;
• concentration of ingredients;
• the presence of special additives;
• appointment;
• properties.

On the packaging, in addition to the brand, the percentage of additives is also indicated.

There are the following types of Portland cement:

• fast hardening. Contains additives of mineral origin, which shorten the curing time. It is used for the accelerated implementation of construction activities and the manufacture of reinforced concrete structures;
• sulfate resistant. The main advantage - resistance to sulfates, is achieved by a decrease in calcium aluminates in the clinker. Used for structures operating in a humid or aggressive environment;
• hydrophobic. Contains surfactants that significantly reduce hygroscopicity. The result of the introduction of additives is an increase in mobility, ease of laying the solution. The material retains its properties at high humidity;
• White. It is easy to distinguish from other cementitious compounds. It has light gray, does not contain titanium oxides, iron and manganese salts. Used for decoration activities;
• color. Contains special pigments of organic and inorganic origin, added to the clinker material before grinding. Colored compounds, for example, yellow cement, are used in finishing activities;
• pozzolanic. Resistant to sulfates, hardens quickly at elevated temperatures. Autoclaving significantly improves the strength characteristics. Designed for use in soil, as well as in a humid environment;
• backfill. Produced exclusively for sealing oil and gas wells. Provides reliable isolation from groundwater, pressure and temperature resistant. It gains strength at the initial stage of hardening.

Cement is a dry mixture that is used specifically for preparing concrete mortar

On the basis of lime, slag and clay, the following cement compositions are produced:

• slag. Gains strength slowly. It is used in the hydraulic engineering industry and port construction;
• slag-limestone. Differs in slow hardening. It is used for plastering and masonry;
• aluminous. Refers to refractory materials. Differs in resistance to corrosion, as well as moisture resistance.

When choosing material for specific work, take into account the purpose of the building material and the features of operation.

How cement is obtained - manufacturing technology

The manufacturing process provides for the following operations:

1. Development of deposits of limestone, gypsum and clay.
2. Grinding mined materials.
3. Drying of the crushed raw material mass.
4. Obtaining limestone-clay sludge.
5. Roasting of raw materials to obtain clinker granules.
6. Crushing clinker to a powdery consistency.
7. Dosage and mixing of components.

Cement is a widespread material that is used in any type of work related to repair, restoration, construction

Used by different technology, characterized by the method of sludge preparation:

• dry. Drying and crushing are carried out in a grinder, into which heated air is injected. The finished fraction has the required moisture content;
• wet. Provides for the use of chalk. It is crushed in a wet state, then the charge is fired and crushed;
• combined. Combines the features of the previous methods, depending on the equipment used in the technological cycle.

Currently, manufacturers prefer dry production.

Application of cement

The scope of application in industrial and civil construction is quite wide:

• production of reinforced concrete products:
• construction of foundations;
• erection of walls of buildings;
• performing plastering works;
• filling the screed;
• production of tiles.

In addition, the material is widely used for road construction, bridge building, hydraulic engineering industry.

Features of marking

There are two labeling methods used for classification:

• according to the European classification in accordance with GOST 31108-2003, various types of cement are assigned the CEM marking with a digital index from 1 to 5;
• on state standard 10178-85, each type of cement composition has an alphabetic index - PC, SHPC, BTs.

For example, Portland cement manufactured according to European standards is labeled CEM 1 or CEM 2, depending on the type of additives. Similar material manufactured according to the national standard is marked with PC. Accordingly, the designation of Portland slag cement can be CEM 3 or ShPTs. Both normative documents are now in effect, which is convenient for manufacturers of cement products.

Conclusion

After reviewing the material, you can get information about the composition, characteristics, manufacturing features, marking and properties of the building material. Now there will be no questions about the word "cement". What is it - we figured it out. When buying, you need to pay attention to the characteristics and grade of the material according to the specifics of the work performed. The information provided will help you make the right decision.

Raw materials in the production of cement are mainly clay and carbonate rocks, as well as other natural raw materials and some types of industrial waste, slag, etc.

Carbonate rocks are limestone, shell limestone, chalk, marly limestone, marl, metamorphic or sedimentary rocks of dolomite, carbonate-clayey and limestone composition. The quality and value of such rocks as raw materials for creating cement is determined by their structure and physical properties... Rocks with a crystalline structure are worse, in comparison with rocks with an amorphous structure, interact with other elements of the mixture during firing.

• Chalk is an easily grinded soft sedimentary rock, a type of smearing limestone. It is easy to grind and is a popular raw material for cement making.
• Marl is a sedimentary rock, transitional from limestone to clayey. May have a hard or loose structure, different density and moisture depending on the percentage of clay impurities. Marl-based mortars are actively used in the construction of stoves, fireplaces, etc.
• Of the limestones for the production of cement, porous and marly types with a small threshold for compressive strength and without the content of silicon inclusions are preferred.
• From clayey rocks in the production of cement are used: loam, clay, loess, shale, as well as loess-like loam.

Clays, sedimentary rocks, are composed of different kinds minerals, when moistened, acquire plasticity and swell. In the dry method of cement production, the binding capacity and plasticity of the clay makes it possible to granulate flour and briquett. Loam is called clay, which contains a high amount of dusty and sandy particles.

Shales are dense and hard rocks that can easily delaminate into thin plates. Compared to clay, shale has a more constant composition and lower moisture content.

Loess is a fine-grained rock, loose and porous, consisting of the finest particles of clay materials, feldspar, quartz and other silicates. Loess is not highly plastic. Loess-like loam is a material that, in its properties, is transitional between loam and loess.

In addition to the main raw materials, various types of corrective additives in cement are actively used in the production process, which make it possible to change some of the properties of the final product. It can be alumina, silica, clay-containing additives, as well as fluorspar as mineralizers (sodium silicofluoride, gypsum, apatite, phosphogypsum, fluorite)

I would like to note that the raw material composition, both dry and wet way production of cement, may vary depending on the location of the cement plant, on the availability of a particular type of raw material, on the capabilities of equipment, demand for certain types of products in this region and much, much more

Today it is impossible to imagine the construction of any facility without the use of cement. It is used at all stages construction process... Without it, it is impossible to complete the foundation, wall masonry, as well as interior and exterior decoration. Until now, no analogues of this building material have been invented, which speaks about unique properties cement. Do you know what cement is made of?

What is cement

Cement is construction material, which is presented in the form of a crushed powder obtained on the basis of clinker. It may contain modifying components and fillers.

According to GOST

The process of obtaining general construction cements should be carried out taking into account the requirements of GOST 31108-2003. It is the standard that is able to regulate the proportions of the necessary ingredients that make up the dry mass and the technology for the production of the material. But this standard does not include special purpose material.

About what specific gravity of cement grade M 500 is described in this

Definition of species

Today, the definition of the most common materials includes:

• aluminous;
• lime-ash;
• waterproof.

Aluminous

The process of obtaining such a material is carried out thanks to the melting method when exposed to a temperature of 1380 - 1600 degrees. In this case, there is no need to use a fine grind of the batch. The process of obtaining this type of material is carried out in furnaces different types... Most often they use blast furnaces and electrical ones.

The composition of this material assumes the following components:

1. Aluminium oxide.
2. Calcium oxide.
3. Silicon oxide.
4. Iron oxide.

How dry cement-sand mixture M 150 is used is described

In addition, the composition of alumina cement is rich in dicalcium silicate. It allows you to get delayed hardening. To increase some properties, the composition can be supplemented with aluminates and ballast admixtures. This mixture will provide a reliable and durable construction.

Airtight

This cement contains finely ground blast-furnace slag and gypsum stone in a 2: 1 ratio. The structure, laid out on the basis of such material, acquires the necessary hardness in water and air. If solidification was carried out in water, then the percentage of shrinkage is minimal.

The setting process takes place after 10 minutes, and for complete drying it is necessary to wait 3 days. The resulting solutions based on an airtight material are characterized by properties such as water resistance, fire resistance, durability, and stability. Compared to Portland cement, such a material has every indicator of fire resistance. In addition, the hardening process is faster than that of alumina.

What is bulk density cement M 500 is described

Ash-lime

To obtain this composition, components such as fuel ash and slag with lime are used. After mixing these elements, they are finely ground. To improve the properties of lime-ash cement, 5 g of gypsum is added. It allows you to achieve quick hardening and increase the strength of the structure.

When erecting a structure for a specific purpose, it is necessary to buy the required grade of cement, which would include all the necessary components. If all proportions are exactly observed by the manufacturer, then the resulting products will have excellent strength indicators, durability, resistance to various aggressive environments. And read about what it is in our article.