In the construction of industrial facilities, the construction of residential buildings, the production of finishing and repair activities, various building mixtures are used. They include cement, which is an astringent. It has unique characteristics and, despite the emergence of new building materials, has no analogues to date. Within the framework of a small article, it is difficult to tell everything about cement. At the same time, we will try to provide detailed information about 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. Indispensable in the construction industry, cement 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 (paste-like consistency);
• acquires a dark gray tint;
• rapidly gaining hardness in an airy and humid environment;
• turns into a stone of artificial origin.

Everyone who used cement was repeatedly convinced that this is a fairly durable building material. The artificial monolith is not inferior in hardness to natural stone.

It is difficult to imagine an area of ​​construction where cement would not be used.

Building material has an 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 excavations and scientific research, ancient cement has been repeatedly studied. When was it invented? Scientists have tried to answer this question. They came to the conclusion that the material appeared long before our era. This is confirmed by samples found in different countries. They contained gypsum, lime and even volcanic ash.

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

Compound

The complete chemical formula of a building material is quite 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 basis of the building material is 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 the 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, improves performance, gives the necessary properties. Granulated slags, crushed shale materials, pozzolanic ingredients and crushed lime are added. The regulatory documents regulating the composition of building materials contain information on the content of various chemicals 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 these main components, special additives are introduced that increase the resistance of the cement composition to high temperatures, the effects of acids, alkalis, and aggressive environments. Additives also increase moisture resistance, improve adhesion to steel reinforcement, and also affect the mobility 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 cement compositions of various grades. Strength is determined by a laboratory method by compressing a reference sample of a solidified mixture. Strength control according to 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 parameter value is measured in megapascals. The digital strength value corresponds to the brand of cement composition;
• grip duration. The parameter characterizes the time interval during which the plastic characteristics of the cement mixture change. A properly prepared solution begins to solidify a couple of hours after pouring in the hot season. In autumn, the hydration process can take 8-10 hours. The duration of setting at zero temperature sharply increases and can be 15–20 hours. The introduction of additives allows you to adjust the setting speed;
• resistance to negative temperatures. This characteristic is called frost resistance. It characterizes the ability of a hardened cement mass to accept deep freezing with further thawing over many cycles. At the same time, the integrity of the array and strength characteristics should be maintained. The reason for the destruction is an increase in the volume of water that saturates the pores. The introduction of additives increases the frost resistance threshold;
• density. The parameter characterizes the mass of a powdered substance in one cubic meter of material. Freshly prepared cement composition has the smallest specific gravity. During long-term storage, the material becomes caked, and during transportation it becomes compacted. At the same time, the density increases. The characteristic depends on the fineness 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 the stone

Other features include:

• hygroscopicity. The degree of water absorption is different for different brands;
• grind size. Determined by sifting through a sieve;
• corrosion resistance. Increased by the introduction of special additives;
• best before date. It depends on the storage conditions and the permissible level of humidity.

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

Varieties of material

In the construction industry, various types of cement materials are used, which differ in 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 reduce the duration of curing. 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 reducing calcium aluminates in the clinker. Used for structures operating in a humid or aggressive environment;
• hydrophobic. Contains surface-active components 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 cement compositions. Has a light gray color, does not contain titanium oxides, iron and manganese salts. Used for finishing events;
• color. Contains special pigments of organic and inorganic origin, added to the clinker material before grinding. Colored compounds, such as yellow cement, are used in finishing activities;
• pozzolanic. Resistant to sulphates, hardens quickly at elevated temperatures. Autoclaving significantly improves strength characteristics. It is intended for operation in the soil, and also in the damp environment;
• backfill. Produced exclusively for sealing wells in gas and oil developments. Provides reliable isolation from ground water, resistant to pressure and temperature. Acquires strength at the initial stage of hardening.

Cement is a dry mix that is used specifically for the preparation of concrete mortar.

Based on lime, slag and clay, the following cement compositions are produced:

• slag. Slowly gaining strength. It is used in the hydraulic engineering industry and port construction;
• slag-lime. Differs in the slow hardening. It is applied to plaster works and a laying;
• aluminous. Refers to refractory materials. Differs in resistance to corrosion, and also moisture impermeability.

When choosing a material for performing specific work, consider the purpose of the building material and the features of operation.

How cement is produced - manufacturing technology

The manufacturing process involves the following operations:

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

Cement is a widely used material that is used in all types of work related to repair, restoration, construction.

Various technologies are used, differing in the method of preparing the sludge:

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

Currently, manufacturers prefer the dry method of production.

Application of cement

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

• production of reinforced concrete products:
• building foundations;
• erection of walls of buildings;
• execution of plastering works;
• pouring screed;
• tile manufacturing.

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

Marking features

There are two labeling methods used for classification:

• according to the European classification according to GOST 31108-2003, various types of cement are assigned the CEM marking with a digital index from 1 to 5;
• according to the state standard 10178-85, each type of cement composition has a letter index - PC, ShPC, BC.

For example, Portland cement manufactured according to European standards is labeled CEM 1 or CEM 2, depending on the type of additives. A similar material manufactured according to the domestic standard is marked with PC. Accordingly, the designation of Portland slag cement can be CEM 3 or ShPTs. Both regulatory 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 building materials. Now there will be no questions at 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.

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 mortar.

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 finely ground. Gypsum controls setting speed; it can be partly replaced by other forms of calcium sulfate. Some specifications allow the addition of other materials when 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 alite, belite, aluminate phase and ferritic phase. In clinker, several other phases are usually present in small amounts, such as alkali sulfates and calcium oxide.

Alite is the most important constituent of all conventional cement clinkers; its content is 50-70%. It is a tricalcium silicate, Ca3SiO5, whose composition and structure are 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 of all phases plays the most important role in the development of strength; for the 28-day strength, the contribution of this phase is especially important.

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

The content of the aluminate phase 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 an undesirably rapid setting unless a setting controlling agent, typically gypsum, is added.

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

The most widely used is Portland cement.

What are cements?

Over the years that have passed since the advent of Portland cement, scientists have come up with, and industrialists have introduced a huge number of new modifications of it. The family of Portland cements has grown and, in order not to get 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%, but it is a basic, structure-forming component.

The classification of Portland cement and its "relatives" is based on two key parameters: the 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 (up to 5%). Designated PC I.

II Portland cement with additives: slag, pozzolana, 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 - W, for pozzolana - P, for fly ash - Z). In addition, the designation includes another letter indicating the maximum content of clinker. If it is "A" - at least 80% clinker, if "B" - at least 65%.

Composite Portland cement is also referred to this type. It may include 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-C or PC II / B-C.

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

IV Pozzolanic cement (may contain both pozzolana and fly ash). Designated PTSTS IV ("A" and "B").

V Composite cement KTs V ("A" and "B"). This cement, like composite Portland cement, may contain several additives, with the exception of limestone. The permissible minimum content of clinker in it is lower than in composite Portland cement, and is at least 40% for the letter "A" and at least 20% for the 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, the symbol may contain additional information about the special properties of cement. For plasticized cements, the index PL is introduced into the designation, for hydrophobized - 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 one of the main building materials. It is used in the creation of binding mortars, cement is used in the manufacture of concrete and reinforced concrete products. The quality of this material determines how strong and durable the building or reinforced concrete structure will be.

The history of cement began in England, where a patent for its invention was registered in 1824. At that time, lime dust mixed with clay was used to make cement. The resulting mixture was subjected to a high temperature at which it was sintered.

The fired semi-finished product of cement is called clinker. It becomes cement after grinding the clinker to a powder state.

In construction, the main property of cement is used - when mixed with water, it gradually hardens, and then turns into a durable stone. The strength characteristic of the finished product, the material can acquire even in the air, if there is excess moisture.

Raw materials for the production of cement, what it is made of, manufacturing technology

Today, the process of making cement has changed. It is made in several ways, and the components included in it also differ from those used two hundred years ago.

In order to understand what cement is made of and how it is produced, it is necessary to know what types of raw materials are used today by manufacturers of this important building material.

Since the raw materials for the production of cement are natural rocks, the enterprises involved in its manufacture are most often located close to the mining sites of these rocks.

All fossils from which cement is made are divided into two types:

1. Carbonate fossils that differ in characteristics and structural features. It is the structure of the rock that ensures its effective interaction with the rest of the ingredients of the product composition.
2. Clay and rocks of sedimentary origin. Having a mineral base, when moistened, they acquire plasticity and increase in volume. Since this type of raw material is characterized by viscosity, they can be used by producing cement in a dry way.

Now it is necessary to name specifically which fossils belong to each of the types of raw materials used in the production of cement.

The carbonate rocks include the following types of natural raw materials:

• Chalk is a type of limestone. Has the ability to be easily crushed;

• marl limestone, found in nature in both loose and solid state. The rock may contain impurities of clay, so this type of limestone is considered a transitional raw material with properties characteristic of both limestone and clay;

• limestones - shell rocks that do not have silicon inclusions. The rock has a porous structure that easily collapses under compression;

Limestones - shell rocks

• dolomitic rocks and other fossils of sedimentary origin. They contain carbonates, which give the rock valuable properties.

Clay rocks include the following types of fossils:

• clay with mineral inclusions that swell on contact with water;

• loams containing an increased concentration of particles;

• shales with a clay base. This raw material is classified as a rock with increased strength. Under mechanical action, it is divided into lamellar plates. It is characterized by a stable composition and low moisture content;

• loess, porous rock, with inclusions of particles and silicate.

In addition to these types of raw materials, some types of industrial waste are used to produce a cement mixture at the plant. To improve the quality, additives are added to its composition, provided for by the technological process: alumina and silica, fluorspar and apatite.

The use of sand is simply necessary when carrying out a variety of repair and construction work. all about the use of quarry sand.

When carrying out finishing work in the kitchen, in the bathroom or in any other room, it is necessary to know the drying time of the tile adhesive. you can find out how long the tile adhesive dries.

Currently, decorative plaster is rightfully the most popular and progressive finishing method. Going to get acquainted with its independent preparation.

All additives, called plasticizers, are also of natural origin. They affect for the better the following qualities of cement:

• increase resistance to temperature changes;
• enhance strength;
• mobility and elasticity of the product;
• reduces the penetration of water into the finished product.

Depending on the properties of the plasticizers added to the cement, its solution will harden faster or slower.

The composition from which cement is produced

Some people working in the construction industry do not know what cement is made of.

The composition of cement may vary depending on the brand and purpose.

However, regardless of the type of cement, that is, the recipe used in its production, two components serve as the basis for it - limestone with the addition of clay.

The amount of limestone is three times the amount of clay. These are necessary to obtain high-quality clinker, which is a semi-finished product for the production of cement.

Now we can name the main components of the composition, so that it is clear to everyone what cement is made of:

• clinker, the basis of the final product, which determines its strength characteristics. It is used in the form of granules with a diameter up to 60 mm. Its heat treatment is carried out at a temperature reaching up to 1500 °. When melting the clinker, a mass is formed, which is characterized by a high content of silica and calcium dioxide;
• these components affect the performance of the final product. Before firing, the clinker granules are crushed to a dusty state;
• gypsum, which determines the rate of cement hardening. The basic recipes provide for the addition of pure gypsum to the composition of up to 6% of the total number of components;

• special additives (plasticizers, frost-resistant additives, liquid soap, etc.) that enhance the properties already available in the product, or give it special characteristics that can expand the scope of cement.

Production - how cement is made, the process of receiving at the plant

The production of the material is carried out in a certain order, in stages. The technology of its production provides for the following operations:

1. The ingredients intended for the manufacture of clinker are pre-mixed. It is imperative to strictly observe the proportions of the composition - 25% clay and 75% limestone.
2. The resulting composition is fired at high temperature. During high-temperature firing, clay and lime combine to form clinker.
3. The finished product is crushed by ball mills, which consist of drums located in a horizontal position, inside which steel balls are placed. The clinker placed in them is crushed to a state of powder.
4. The finer the cement fractions obtained, the better performance characteristics it will have.

There are several methods for manufacturing this building material. Their choice is due to many factors, the main of which is the specifics of the equipment available at the enterprise and the demand for certain brands of cement.

The developed technologies have a difference in the methods of preparation of raw materials used in the production of the composition. The order of its manufacture remains the same.

The following methods have been developed:

1. Wet technology that replaces lime with chalk. In the process of mixing the components of the composition, they are crushed in a ball mill. This process is carried out with the addition of water. As a result, a mixture is formed with a moisture concentration of up to 50%.
2. The resulting material is then fired in a kiln. After firing, it already becomes clinker. Then it is crushed.
3. Dry technology significantly reduces the cost of production, as it combines several technological operations into a single process. When using this technology, the components entering the ball mill are simultaneously ground and dried.
4. Hot gases are used for drying. The finished charge mass has the consistency of a powder.
5. Combined technology combines the features of the above-described production methods. Depending on the equipment used in the enterprise, a semi-dry composition with a moisture content of up to 18% can be obtained.
6. In the second option, dry is initially prepared, then moistened to 14%. In both cases, the prepared composition is then annealed and ground.

For more information about cement production, see the video:

Classification of cement mixtures

There are many varieties and different of this building material. They are distinguished by their basic composition and additives, which give each species special properties.

Among the main types are:

• Portland cement, which began the production of a product popular in construction. It is not used for the manufacture of binder solutions. It is used to create high-strength concrete products, and mortars;
• aluminous cement, characterized by resistance to moisture, rapid hardening;

• acid-resistant cement, which uses quartz and sodium silicofluoride. The material is resistant to acids, but short-lived.

When purchasing any type of cement, you should be aware that its composition actively interacts with the environment, losing its strength during long storage.

Even if it is stored in a dry room, after a few months its brand will change down. Therefore, when purchasing it, you should pay attention to the date of manufacture. You can also read our article on technical specifications.

Cement. Classification and marking.

That's what you can't do without at any construction site, so it's without cement. It does not matter what kind of house is being built: wooden or brick. The difference is only in its quantity. Every home needs a foundation. And in brick, in addition, he goes to masonry. With block construction, whole rooms are cast from it. What about road construction? And protection from the elements of the sea? What about mudflow diversion? What about bridges and dams across turbulent rivers? This building material has been gained by suffering through experience over the course of centuries, therefore it is reliable and has such significance.

background

As soon as a person began to build a dwelling out of stone, a means was immediately needed that would bind these stones. At first it was just clay. But such buildings did not differ in durability, and outwardly the building looked unpresentable. Then the binding properties of lime were noticed. First, the ancient Greeks and Romans discovered this, and the Romans discovered that when pozzolana (volcanic ash) and trass (hardened volcanic ash) are added to lime, the dried masonry becomes almost monolithic. In Russia from clayey limestonesgray lime was obtained, seizing in damp and wet masonry. In practice, both Rome and Russia almost approached the production of cement experimentally: both clays and pozzolana contained oxides of iron and aluminum, which, as a result of exposure to water and lime, underwent a hydration process. Then for a long time there were no changes in the composition of the binder (only fillers in solutions changed). And more recently in 1822- 1824 .G. almost simultaneously, the Russian Cheliev and the Scot Aspind received building mixtures similar in composition to modern cements. Andthe Scot thought of obtaining clinker and producing cement from it. The name "Portland cement" also came from England, since the concrete from the Scot cement both in color and strength resembled a stone mined in the mountains near the city of Portland.

What is cement?

By itself in nature, it does not form anywhere. And, thank God, otherwise we would not see sand and grass, we would walk on concrete. This is an artificial building material that, when mixed with water, forms an astringent plastic mass. Over time, the mass hardens and becomes a stone-like body, a monolith. What distinguishes cement from other binders is that it gains strength and solidity.in high humidity conditions and even under water. If you take air lime or gypsum as a binder, then they harden only in air. The reason is that in concrete, the cement hardens not so much due to the evaporation of water, but because the water reacts with the cement. In this case, only solid or crystalline substances are formed and heat is released. Most likely, this is why the process of mixing cement and water is called a shutter, and not a dissolution. The formation of a monolithic mass occurs as a result of cement hydration. Therefore, if the concrete is allowed to dry quickly in the sun, it will "tear", that is, it will crack and its destruction will begin. To prevent this from happening, it is wetted until the concrete is completely hardened.

Cement production

First you need to prepare raw materials. The raw material is limestone. The best limestones for cement productionThese are marl, chalk and calcareous tuffs. Dolomites and gypsum, although they are limestones, degrade the quality of the cement. That is, the best cement is obtained from finely porous limestones with no silicon inclusions. Limestone is crushed and thoroughly mixed with clay. In the resulting mixture of clay, about a quarter, the rest is limestone. This composition enters a rotary kiln with a diameter of 2 to 7 meters and about 200 meters long. In the kiln, 1450°C is the "sintering temperature", at which time the clay and limestone particles melt and diffuse into each other. The composition leaves the kiln after 2-4 hours in the form of sintered lumps of various sizes, this is the so-called cement clinker. Next, the clinker is crushed to particles of 1-100 microns. At the same time, up to 6% gypsum is added, this is necessary to prevent the process of cement setting from moisture in the air. Why is cement in such a "rush" to set from atmospheric moisture? Yes, it's just that the sticking surface after grinding is very large: the surface area of ​​​​particles of just one gram reaches 5000 cm2. Are other mineral supplements added? Naturally, after all, cement is needed in the foundation, and for masonry, and for floors, for example, water-repellent or quickly hardening cement is needed. To obtain different properties, a different composition is needed, so mineral additives are designed to provide certain properties.

Classification of cements

There is no unified and comprehensive classification of cement, similar to the periodic system of Mendeleev or the classification of the plant world of Carl Linnaeus. Therefore, there are several classifications, each of which takes into account some separate category of features.

For example, there is classification of cement division by clinker, which is the basis of their production:

• - Portland cement clinker;
• - high alumina and alumina clinker;
• - sulfate ferritic clinker;
• - sulfate aluminate clinker.

By appointment cements subdivided into:

• - special;
• - general construction.

Some classifications are based on the material composition. Then cements are subdivided as follows:

• - cements with mineral additives;
• - non-additive cements.

There is a classification that takes into account compressive strength:

• - cements, where strength is not taken into account;
• - cements with strength M600, M550, M500, M400, M300, M200.

A couple of classifications generally take into account time periods. One, taking into account the speed of hardening, divides cements into:

• - normally hardening;
• - fast hardening.

Another takes into account the setting time:

• - fast-setting (up to 45 min);
• - normally setting (45 min-2 hours);
• - slow-setting (more than 2 hours).

Cement marking

The determination of the brand of cement is based on the determination of its strength. How is it defined? Cement is thoroughly mixed with sand in a ratio of 1:3. The finished mixture is closed with water. Water is taken in an amount of 40% by weight of cement. Cubes or parallelepipeds are molded from the resulting plastic mass. To correctly determine the strength, such a workpiece is kept in water for28 days. Then these pieces of concrete are pressure tested for bending and compression. Most often, to check the compressive strength, take the halves formed as a result of a break from a bending test. And, attention! The amount of pressure that was needed to crush the workpiece is the brand of cement. Let's say that it took a pressure of 500 kg / cm 2 . So this is cement with a brand of 500.

Now let's deal with the markings written, for example, on the bag. The inscription is MPTs400-D20. "M" means that structures using this cement will be frost-resistant, the letters "PC" mean that it is Portland cement, the number 400 is a brand that means compressive strength, "D" is the presence of organic additives, and the number after it shows the percentage these additives. Thus, we have a bag with frost-resistant Portland cement grade 400 with 20% organic additives.

Varieties of cement

At the head it is necessary to put high-quality Portland cement, which does not even contain mineral additives. Next come cements containing mineral additives to change properties. The next group includes cements containing organic additives (usually resins). Slag cement is also distinguished, from which massive concrete elements of the building are made. Additional letters on the marking can tell a lot about the varieties of cement.

1. 1. B. Fast hardening, intended for repair work.
2. 2. BC. White cement for finishing and sculptural works.
3. 3. PPC. Pozzolanic cement with finely ground silica. The main advantage is reduced heat dissipation. Because of this, the upper and inner layers give off heat evenly, which means that the concrete will not crack.
4. 4. SC. Sulfate-resistant cement with protection against the destruction of concrete by salts. Therefore, it is perfect for hydraulic structures.
5. 5. shopping center. Grouting cement for plugging gas and oil wells.
6. 6. ShTs. Slag cement produced without a clinker base.
7. 7. CC. Colored cement obtained by the introduction of coloring pigments.
8. 8. PL means that plasticizers are used, HF - hydrophobic additives, due to which the effect of non-wetting, water repellency appears.

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The word "cement" itself comes from the Latin name, which literally means "broken stone". This loose substance is one of the most common materials on earth used in various types of construction.

Concrete is made from cement, it is poured into the foundation, it is used for plastering, restoration work. Popular concrete products, reinforced and ordinary, are also made on the basis of this bulk material.

What is cement made of and what is it essentially. Depending on the type of mixture and brand, the composition will be slightly different, but the main components will remain unchanged.

What is cement, its chemical properties

M 800

Cement M 800, this is the most rarely used brand. Its number means that concrete made from this cement can withstand loads up to 800 kg/cm3.

It consists of crushed stone from high-strength rocks, plasticizers, additives that increase the strength characteristics of concrete.

It is designed to strengthen structures that have very high requirements for strength, the proportions of the mortar are carefully observed.

Its properties:

• high ability to withstand the aggressive effects of sulfates for a long period;
• frost resistance;
• affects the accelerated hardening of the finished composition;
• does not require a lot of liquid in the manufacture for better mobility.

M 700

Concrete from cement M 700 belongs to heavy concrete and has high strength. The composition of the cement mixture includes substances that accelerate the setting rate of the mortar and, like M 800, increase the strength of structures.

The composition of concrete includes: Portland cement, crushed stone, selected sand, various plasticizers, a small amount of well-purified water. For greater mobility, substances are added that will maintain strength at the desired level.

Cement M 700 has the following advantages:

• aesthetic qualities;
• high strength;
• water resistance;
• use on any type of coating;
• white cement is resistant to sub-zero temperatures.

M 600

Cement M 600. This grade is made, like most other frequently used grades, from clay and limestone and is processed at high temperature.

This cement is durable and most often used in the construction of strategic structures and military facilities.

It is also used for:

• emergency work;
• reconstruction;
• restoration work.

This type of cement is not used in the manufacture of general purpose reinforced concrete products. Of course, this brand can be used, for example, in private construction to increase the service life of structures, but this will lead to a complete lack of savings that will not be justified.

Grade of cement, similar to brand 600, but has a wider scope:

• production of reinforced foundations;
• reinforced slabs and columns;
• emergency recovery work;
• production of beams and floor slabs;
• pavement installation.

A mixture is made from intermediate clinker, gypsum stone and blast-furnace charge, which has thermal strength.

The brand has two varieties.

The first is M500 D0 in which there are no impurities and additives, this pure mixture of clay and limestone rocks, concrete from this mixture is waterproof and quickly hardens.

The second - M 500 D20, involves additives in the composition of cement no more than 20%.

The first option is used in the construction and manufacture of concrete, the second option with additives is more often used for the preparation of finishing mixtures and for masonry work, a mixture of such cement resists corrosion well.

Cement is used in many types of construction, refers to Portland cement.

The mixture is applied:

• in the manufacture of reinforced concrete products;
• in multi-storey construction;
• during the construction of bridges;
• for the manufacture of retaining walls;
• in the device of pile and strip foundations.

Cement M 300 is one of the most common brands, and it is used:

• in low-rise construction;
• in civil engineering;
• for installation work.

An economically justified scope of this mixture is the construction of monolithic.

According to its characteristics and composition, this brand is also well suited for the manufacture of belt-type barriers, retaining structures, roads and pavement, tile frames, floor slabs, walls, stairs, etc.

M 200, M 100

These two brands have a lower cost than the others and do not differ in increased durable characteristics. The main area of ​​​​use of the M100 is finishing work, floors, rough road work.

Cement M 200 is used to prepare a concrete mixture that is suitable for the construction of light weight structures.

Both brands are currently out of production.

Each brand of cement has an additional letter designation, for example:

• PC stands for Portland cement;
• ShPTs - slag Portland cement;
• PL - plasticizer;
• SS - sulfate-resistant cement;
• BC - white cement; GF - hydrophobic;
• VRTs - cement with fast hardening.

Hydrophobic cement, which is able to repel water and be resistant to moisture, is made with the addition of finely ground substances that do not soak in water. Such cement in a dry form is stored longer. Hydrophobic dry material gives concrete and increased frost resistance compared to conventional.

A wide choice of cement and constantly developing technologies in its production and mining make it possible to translate into reality many ideas for construction or repair, architectural work, even under any climatic conditions.

This was not always the case, and although concrete buildings existed more than 5,000 years ago, a truly high-tech cement manufacturing process appeared only in the 20th century and continues to develop.