What cement is extracted from. The whole truth about the connecting link: how and from what cement is made. "Dry" and "wet" method

What cement is made of: types and varieties of mixture + manufacturing process + necessary equipment + how clinker cement is made.

A business can be built in a variety of areas, but it is the construction industry that is basic for humanity, because primitive people were still engaged in the search for shelter and housing.

Today, the path has already been passed from primitive caves to modern skyscrapers or comfortable mansions. All this became possible thanks to the invention of cement, for which there is always a demand.

What is cement made of? We will answer in the article.

Cement business: the basics

Cement is a binder used in construction. The binder has the property of almost firmly fixing the elements trapped in it under the influence of water and air.

Drying, it creates a monolithic surface, which is very important in the construction of modern buildings. In addition, it is resistant to temperature extremes and most other climatic factors, and most importantly, when frozen, it is not harmful to health.

Since it is always necessary to build or patch holes in the walls, regardless of the economic situation in the country, the demand for this product is high, and consumables are cheap.

Therefore, the profitability of the business model of enterprises that make cement is always high. Isn't this an entrepreneur's dream: low costs with stable income?

But there are also disadvantages, the most important of which is the relative high start-up capital, which is needed to start a full-fledged cement production.

The next limiting factor for investment in this area is strict quality control: do not forget that the safety of buildings depends on this. If a high-rise building collapses because of your cement, who will be in demand?

But all these problems do not stop, which means that all this is quite realizable.

Types and types of materials from which cement is made

Today, the basic component of cement is clinker, but another 15% is the mineral mixture, as required by GOSTs.

By the way, if we bring the share of industrial chemicals in the mixture to 20%, then it will already be "pozzolanic cement", for which there are separate standards.

So, GOST 10178-76 regulates the production of pure composition, and GOST 21-9-74 - mixtures with various chemical additives.

In general, all the properties of cement can be combined into 7 points that allow you to customize production for a different client - from a farmer who needs to fill a hole in a barn to a large construction company from Moscow City:

In addition, the cement is divided with an eye to what it is made of and how it is used:

№	Type of	Brief description of properties; what cement is made of
1.	Lime	Standard cement without additives.
2.	Marly	A mixture based on marly rocks.
3.	Clay with slag and bauxite additives	Slag and bauxite make the cement waterproof, fire and frost resistant.
4.	Portland cement and slag Portland cement	Mixture with carbonate or slag additives, as well as with alumina residues. The peculiarity is that it is processed at a temperature of 1500 degrees. When dry, it turns into a strong stone mass, which is actively used in the construction of large buildings and monuments.
5.	Grouting	A mixture with improved airtightness characteristics. This cement is made for the needs of the gas production and other industries that require high-quality insulation.
6.	Hydraulic	High pressure mixture.
7.	Straining	Fast drying mixture.
8.	Sulfate resistant	Slow drying mixture with increased frost protection.
9.	Decorative	The mixture is made for decorative purposes, therefore it has a white color due to a large percentage of gypsum.

How is cement made?

We figured out what cement is made of, now a little about the technologies for its production.

Modern technology includes several stages and elements, forming a vertically integrated structure - from the extraction of rocks to the sale of a cement mixture or clinker on the wholesale market.

The production of cement on an industrial scale begins with the demolition of an entire mountain, so a small business is unlikely to be able to do this.

This will require expensive mining equipment, as well as a whole factory workshop with sophisticated equipment, so the initial investment can exceed 500,000,000 rubles, and taking into account inflation and exchange rate fluctuations - up to 1 billion.

Or a closed joint-stock company, with all permits (especially in terms of ecology).

At the first stage of production, a mountain is demolished or a deep pit is made to access the "mainland" - under the layer of soil and chernozems there are clays and limestones, which are needed for these purposes. The pit is made about 10 m deep.

Equipment used to make cement:

After that, limestone and clay are brought by dump trucks to the plant, where they are crushed to a powdery state.

Then the mixture is fired at a temperature of 1500 degrees, as a result of which granular clinker is obtained - the base from which cement is made. Some manufacturers sell the clinker itself to smaller companies.

To obtain clinker, the maximum of all costs will be required, since you will have to purchase limestone and clay or purchase dump trucks, excavators, etc.

Plus, crushers are needed that work in three stages - from crushing large stones to turning the mixture into powder. You will also need a special industrial oven. All this is connected by a conveyor belt.

According to the estimates of market players, the production of clinker accounts for over 70% of the cost of the finished product. To pay for itself, you need to produce about 800 tons of mixture per day or 176,000 tons per year.

How is clinker cement made?

The finished mixture is made from clinker, gypsum, sand and mineral additives. After grinding and firing, large lumps are crushed to a granule size of 1 - 100 microns, as required by GOST.

At the same time, the technology requires alternate crushing of individual components before mixing. So, for example, first of all, the frozen clinker is crushed, then crushed gypsum is added, and only then a cement mixture is made, adding industrial chemicals there. Then comes drying and final grinding.

If you intend to sell a dry product, then the next step is packing into bags. If you intend to sell it ready-made, then before loading it onto cement trucks, water and other liquid chemicals are added to the mixture, which prevent premature solidification inside the car.

It is important to understand that if you decide to build your cement manufacturing enterprise without intermediaries, and sell a finished product with a higher added value, then it makes sense to bring this process to the end.

For this, it is necessary to purchase one more furnace and crushers, a cooler, and a dosing unit.

Plus, you need to immediately decide how you will ship the cement to the market. Large construction companies make their choice in favor of cement trucks, where they transport a ready-made liquid mixture - with sand and other chemicals (if necessary), so that it can be used in work right now.

Small firms, as well as retail chains, give priority to packages with dry mix, which are made in several versions - from small packages up to 5 kg, to bags of 40 or more kilograms. use disposable paper.

If you choose this dry method, you will need special equipment for packing and sorting cement, as well as a warehouse.

Having dealt with the fact what cement is made of, you can safely take up its production at your enterprise.

Do you want to know how and from what cement is made?

The entire technological process in one video:

The situation during the crisis is not easy, but people will still build, which means there will be demand for cement.

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In our article, we would like to talk about the amazing building material from which numerous concrete structures, walls of houses, bridges, foundations, small architectural forms and similar structures are made. It's about cement. As you know, cement is a non-natural building material.
The production of this demanded material is a very expensive and energy-consuming process, but what is obtained is ultimately worth it. Cement, as a rule, can be used alone, or it can be a component of another building material, such as concrete. Manufacturing plants are usually located right where the raw materials needed for the cooking process are mined so as not to incur shipping costs.
The production of cement has two stages: the first - the production of clinker, the second - the clinker is processed to the state of a powder, gypsum or other additives are added to it.
The first stage of the process is the most expensive, it consumes about seventy percent of the cost of cement preparation, because at this stage the main raw material is extracted. The upper part of the limestone mountain is driven down and, as a result, the limestone layer is exposed. It occurs four to five times at a depth of ten meters (no more), each such layer reaches a thickness of seventy centimeters.
The mined limestone is crushed so that the largest piece does not exceed ten centimeters in circumference. Then the material is dried, ground again and mixed with other components (such as active mineral additives). Then the resulting mixture is fired .. The clinker is ready.
The second stage also consists of many operations: crush the clinker, dry mineral additives, crush gypsum, mix the clinker together with the rest of the components. Raw materials in composition and texture will not always be the same. Each type of raw material implies its own method of production. Three methods are used in the manufacture of cement: dry, wet and mixed. Each method has its own unique technologies and equipment, and each has its own pros and cons.
With a dry method of production, the raw material is pre-dried before grinding, and after grinding it will turn out in the form of a powder (mixture). The wet method is used when cement is made from chalk, clay with the use of various additives containing iron (carbonate component, silicate component, converter sludge, etc.). The moisture in the clay should not be more than twenty percent, and in the chalk more than twenty-nine percent. This method is called wet from the fact that the mixture is ground in water, as a result, an aqueous suspension is obtained, in other words, a sludge. Then it is fired in a furnace, releasing carbon dioxide, then the clinkers in the form of balls are processed into the smallest powder - this is cement.
With a mixed method, both of the previous ones are involved. This method has two types. In the first, raw materials are prepared with water - a wet method, receiving a sludge, then moisture filters are removed up to fifteen to eighteen percent and burned in furnaces in the form of an almost dry mass. In the second method, dry raw materials are used, gradually diluting it with water and turning into granules, ranging in size from ten to fifteen millimeters, and fired.
In each of these methods, it is very important to observe proportions, special equipment and a clear sequence of actions. Ready-made bulk or packaged cement in bags weighing fifty kilograms is loaded onto road or rail transport and sent to its destination.
No construction site can do without such an important building material as cement, which indicates its high operational characteristics.

Cement is an artificially created material that no construction can do without. At the same time, depending on the method of production and the type of cement, the materials for its production can be various natural substances that give each type of cement special properties.

What substances does cement consist of?

The main raw materials for the production of cement are clay and carbonate rocks - clinker, and in some cases industrial waste - metallurgical blast furnace slag.

By "carbonate rocks" is meant and used for the production of cement: limestone, shell rock, chalk, marl, dolomite and other sedimentary rocks that have an amorphous carbonate-clay, chalk or limestone structure.

The fact is that chalk and limestone are easily grindable substances, which is very important in the production of cement - a fine powder with unique properties.

Clay means clay, loam, loess and shale. These rocks consist of different types of minerals (feldspar, quartz, silicate, etc.), which have the ability to increase in volume, and also acquire plasticity upon contact with water.

Cement is obtained by fine grinding of clinker and gypsum. Clinker is a product of uniform firing prior to sintering of a homogeneous raw mixture consisting of limestone and clay of a certain composition, which ensures the predominance of calcium silicates.

In addition to the main types of raw materials in the production of cement, all kinds of additives are used that give the "binder" special properties: alumina and silica additives, fluorspar, gypsum, apatite, fluorite, sodium silicofluoride, sodium chloride and others.

The main stages of the cement production technology, clearly demonstrating what the cement consists of /

• Extraction and beneficiation of the main raw materials (limestone, clay and gypsum stone);
• Crushing, drying, grinding, mixing and adjusting raw materials in proportions clearly specified in regulatory documents;
• Sludge production, depending on the accepted production methods: wet, dry or combined;
• Firing a mixture of raw materials at a temperature of 1 450 degrees Celsius - obtaining clinker;
• Grinding clinker to a finely dispersed state;
• Mixing of components: crushed clinker, gypsum and mineral additives.

The resulting finely dispersed powder of gray-green color is the most widely used type of "binder - Portland cement of this or that brand."

Cement types - purpose and features

• White cement. It is used for the production of packaged building dry mixes and the construction of decorative colored structures. It is characterized by an accelerated set of strength, unique decorative properties, increased resistance to atmospheric factors and a high cost in relation to standard Portland cement;
• Fast hardening cements. They are Portland cement with special additives that accelerate the setting and hydration process;
• Expanding cements. This type of cement is made from alumina cement and gypsum. Unlike all other types of "binder" that shrink during setting, expanding cement, in accordance with its name, increases in volume;
• Waterproof non-shrinking cement. It is used for waterproofing joints, construction of hydraulic structures, underground concrete tanks, tunnels and other structures operating in high humidity conditions;
• Hydrophobic cement. It is a cement with special additives that increase the period of guaranteed storage and transportation in conditions of high air humidity. Used for the preparation of frost-resistant and moisture-proof concrete;
• Alumina cement. It is characterized by a very fast set of strength - up to 50% of the brand strength within 24 hours. The hydration process takes place with a significant release of heat, which is a positive property when concreting at low temperatures;
• Stretched cement. Cement-based concrete of this type has the positive property of expanding with strength. In addition, such concretes are leaders in terms of the water resistance coefficient - up to W20, which is very important for the construction of tanks, pools, monolithic roofs and hydraulic structures without additional waterproofing;
• Pozzolanic cement - Portland cement with the addition of finely dispersed silica. It is characterized by an extended setting time and low heat generation during hydration. It is used for the construction of powerful bulk concrete structures;
• Sulfate resistant cement. It is characterized by high resistance to aggressive salts. It is used for the construction of hydraulic structures operating under the influence of sea water;
• Slag Portland cement. It is made from crushed metallurgical slag with the addition of active substances: lime, gypsum, etc.

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 of 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. Fired 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 decoration methods.

Hydraulic binders

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

These include substances that form hydrated (a water molecule enters the crystal lattice as a component) compounds, when transformation into a stone-like body and further strength development 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 making 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 are 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 to lime that had hydrophobic properties. For this, crushed remains of baked clay bricks and various volcanic rocks were used. So, the composition of the cement, which was used by the builders of Ancient Rome, included pozzolans - ash deposits of the famous Vesuvius volcano.

The experiments continued for many centuries, until the need for a large amount of a durable and inexpensive binder forced the builders to develop an 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 material in England. The artificial stone obtained by Aspdin was very similar to him in color and strength.

Interestingly, Cheliev's technology is more consistent with what is now called Portland cement, and Aspdin's cement was manufactured without the currently accepted sintering of the feedstock.

Production technology

Cement binder from different manufacturers may differ in raw materials, but the basic technological operations are identical. The first stage is the preparation of the initial mineral raw materials, that is, several stages of grinding lime stones and clay, mixing these components in the required 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 mass 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 are determined by the chemical composition of the cement. As a result of technological processing of raw materials, clinker becomes a combination of various chemicals 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 ready-made mortar or concrete mixture, accumulated 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 suit a 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 by this technology gives the 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 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 increased 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 the strength of cement mortars and concretes. The correct selection of 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, a huge amount of cement of the most varied quality is produced in the world. 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.

Cement is called a binder that hardens in water and in air, obtained by joint fine grinding of clinker and the required amount of gypsum and additives. The clinker is obtained as a result of firing before sintering a raw mixture consisting of limestone and clay or some other materials (marl, nepheline sludge, blast furnace slag), taken in a ratio that ensures the formation of calcium silicates, aluminate and aluminoferrite phases in the clinker. Clinker is one of the most important components of cement, the main properties of the cement obtained on its basis depend on its composition.

The introduction of up to 15% of the active mineral additives provided for by the standard into the composition of the cement affects its properties to a relatively small extent. If you introduce more such additives (above 20%), the properties of the resulting product will already noticeably differ from the properties of cement. This product is called pozzolanic cement. The standard gap in the dosage of hydraulic additives from 15 to 20% is made in order to more clearly distinguish between cement and pozzolanic cement.

The specific gravity of Portland cement ranges from 3.0 to 3.2. The bulk density of cement in a loosely filled state is 900-1300 kg / m3, and in a compacted state it is 1400-2000 kg / m3. When calculating the capacity of warehouses, the volumetric weight is taken equal to 1200 kg / m 3, and when the volumetric dosage of materials for the preparation of concrete mixture is 1300 kg / m 3.

Cement (GOST 10178-76) produced without additives or active mineral additives that meet the requirements of OST 21-9-74. The main properties of cement include: strength (activity), setting time, uniformity of volume change, fineness of grinding, density, water demand, water separation, frost resistance, heat release, adhesion to steel reinforcement.

Water demand of cement paste. The water added to the cement during mixing is necessary for the normal flow of chemical processes that occur during cement hardening, and for imparting mobility (plasticity, fluidity) to the freshly prepared cement slurry or concrete, which ensures its density in the form or formwork. It is possible to reduce the water demand and increase the plasticity of cement by introducing plasticizing organic and inorganic surfactants, for example, sulphite-yeast brew.
More details - water demand and binding capacity of cement paste.