The whole truth about the connecting link: how and from what cement is made. What is cement made of? Cement process

Cement is understood as a binder obtained by grinding clinker, as well as gypsum and additives. Clinker as a result of sintering of the raw material, which contains limestone and clay. Also, clinker may contain nepheline sludge, marl, blast-furnace slag. Clinker is the main component that is part of the cement and affects its quality characteristics.

The introduction of mineral additives in the amount of up to 20% of the mass can significantly change the properties of the starting material. If the additive content exceeds 20%, the output is pozzolanic cement.

Cement production

The production cycle consists of several stages:

• The first stage involves heating a mixture of clay and slaked lime (other components may be present, depending on the type of cement) to a temperature of + 1450 ° C, as a result of which clinker granules are formed.
• The second stage is mixing the granules with gypsum (gypsum is added in order to regulate the setting time, can be replaced with calcium sulfate) and grinding. Further, additives are introduced (if necessary), which will affect the properties of the cement. The average clinker parameters provide for the content of 67% - CaO, 5% - Al 2 O3, 22% - SiO 2, 3% - Fe 2 O 3 and other components in the amount of 3%.

What is the composition of the cement

• Alit(Ca 3 SiO 5) is a tricalcium silicate that reacts quickly with water. This component plays a significant role in the strengthening of cement. Its content in clinker is 50-70%.
• Belit(Ca 2 SiO 4) - dicalcium silicate. When mixed with water at first, it slowly reacts, while its effect on the strength of concrete is negligible. At a later date, whitewash significantly increases the strength of the structure. Belite content in clinker is 15-30%.
• Aluminate phase(Ca 3 Al2O 6) - tricalcium aluminate. Mixing with water, the component is able to provoke a quick setting. Therefore, gypsum or similar components are added to the cement composition to control the setting process. The content of the aluminate phase in the clinker is 5-10%.
• Ferritic phase(Ca 3 Al2O 6) tetracalcium alumoferrite. The reaction rate with water is intermediate between the indicators of belite and alite. The share of the ferrite phase in the clinker is 5-15%.
• Other elements(for example, calcium oxide or alkaline sulfates) no more than 3%.

The main characteristics of cement

According to GOST 10178-76, this material can be produced with or without additives. Their content can affect such properties of cement as:

• Strength - the ability of the material to perceive a certain volume of loads without destruction. There is a direct relationship between the strength and the ability of cement to harden when mixed with water. Strength is marked with the letter "M" and a digital value of 300, 400, 500, 550, 600, less often 700 and 800. This indicator is determined by calculating the ultimate bending strength of the sample and characterizes the load in kg per 1 cm 2.
• Setting time.The clinker grinding fineness has a direct influence on the time of setting and hardening of cement. The thinner it is, the stronger the material. The setting time of the test specimens is determined by testing the density of the cement paste. In addition to grinding, their duration is influenced by water demand and mineralogical composition.

The setting time for a composition of normal density is at least 45 minutes, maximum 10 hours. With an increase in temperature, they decrease, with a decrease, on the contrary, they increase.

• Water demand - the amount of water required to hydrate the composition and impart a certain plasticity to the cement paste. Typically, the hydration process uses 15-17% of the cement weight. If it is required to ensure the mobility of the solution, 2 times more water is taken.

• Bulk density. In a compacted state, this indicator is 1400-1700 kg / cm 3, in a loose state - 900-110 kg / cm 3. In this case, the true density of the cement is 3000-3100 kg / cm 3.
• Corrosion resistance.This characteristic depends on the mineral composition and density of the material. With an increase in the fineness of the grinding of clinker and an increase in the porosity of concrete, a decrease in corrosion resistance occurs.
• Heat dissipation.During the hardening process, the cement gives off heat. If this process is slow, then the risk of cracks on the surface of the structure is minimal.

If accelerated heat dissipation is noted, it is not recommended to use this material in the creation of massive structures. It is possible to regulate such an indicator as heat dissipation of cement by introducing inert and active additives into its composition.

• Frost resistance - the ability to withstand a certain number of thawing and freezing cycles in fresh or salt water.

Cement recipe М500

Despite the impressive selection of building materials and mixtures, M500 cement still does not lose its high popularity. As well as decades ago, it is used almost everywhere in foundation pouring and concrete production.

Such a high demand for the material is explained by its environmental friendliness (made on the basis of clayey rocks), high resistance to aggressive media and corrosion (used in the construction of dams and other hydraulic structures). On its basis, concrete, reinforced concrete, sand concrete, asbestos cement, building mixtures and mortars are produced.

The cement group includes:

• BTTS - fast-hardening,
• BPC - white,
• SPC - sulfate-resistant,
• CPC - color,
• HPC is a hydrophobic cement.

Plasticized PC is obtained by introducing 0.25% sulfate-alcohol stillage into the dry composition. When this component is added, the frost resistance indicators increase, the mixture acquires increased mobility. The gray color of the mixture is given by the iron compounds contained in it. Like any other building material, it differs in the amount of added additives.

Cement M500 - M (strength grade), 500 - load (kg) per 1 cm 2. The percentage of additives can be determined by the number near the letter D in the cement marking.

Chemical composition of cement M500 (PC 500 D0) (%)

• 21.55 - silicon oxide
• 65.91 - calcium oxide
• 5.55 - aluminum oxide
• 4.7 - iron oxide
• 1.9 - sulfuric acid anhydride
• 1.46 - magnesium oxide
• 0.35 - potassium oxide
• 0.49 - loss on ignition.

Quality indicators of M500 cement:

• steaming activity - 35.3;
• setting time, 155 minutes - beginning and 250 minutes - end;
• compressive strength, on the third day - 34.1 MPa and 51.3 MPa - on the 28th day;
• fineness of grinding - 92.3%.

Clinker chemical composition:

• magnesium oxide,% - 1.26
• sO 3 content,% - 0.1
• chlorine ion% - 0.0001
• insoluble residue,% - 0.41

Mineralogical composition of clinker (%):

• C 2 S (2CaO * SiO 2) dicalcium silicate - 16.7
• С 3 S (3CaO * SiO 2) three calcium silicate - 59.8
• C 4 AF (4CaO * Al 2 O3 * Fe 2 O 3) four calcium aluminoferrite - 14.3
• С 3 A (3CaO * Al 2 O 3) three calcium aluminate - 6.7

The main types of material:

• M500 D0 - powder composition without impurities and additives, capable of giving concrete high strength, frost and water resistance. It is used in industrial construction, effective in recovery, emergency and repair work due to high initial strength;
• M500 D20... The mixture contains 20% additives. It is characterized by high indicators of water and frost resistance, practically does not corrode. It is used in various branches of construction, in the production of foundations, reinforced concrete, beams, etc. This building material is widely used in the manufacture of masonry, plaster, building and concrete mortars, in carrying out repair and construction work.

Main characteristics of M500 cement:

• Long operational period.
• Fast response (setting occurs a few hours after mixing).
• Excellent adaptation to environments.
• Convenience of preparation and use of the composition.
• High quality finished structures, low wear and tear.

The use of M500 cement can significantly reduce the construction cycle and provide structures with high strength.

The cement industry is one of the most important branches of material production. The importance of this branch in the national economy is determined primarily by its inextricable link 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. Natural gas is used as fuel.

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 resembled 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 of Portland cement is the ability to harden when interacting with water. It is characterized by the brand of Portland cement, determined by the compressive and flexural strength of standard samples of cement-sand mortar after 28 days of hardening in humid conditions.

2. Cement production consists of two main technological processes: obtaining clinker (the most laborious 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 passing preliminary processing, source materials enter the wet autogenous grinding mill "Hydrofol", 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, which carries 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 the raw material are fused together to form clinker.

13. The kiln is a rotating metal cylinder that is tilted to a 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 into 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 concrete, 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. From silos, cement is shipped by railroad cars and by car in the following form: in bulk, in special FIBC containers weighing up to 1 ton, paper bags weighing 50 kg.

Cement is an astringent substance that hardens in water and outdoors. Let's figure out what cement is made of, however, there is still everything zaivist from. It is formed by grinding clinker, gypsum and special additives. Clinker is the result of firing a raw mixture that includes limestone, clay and other materials (blast furnace slag, nepheline sludge, marl). Ingredients are taken in a certain ratio, which ensures the formation of calcium silicates, aluminoferritic and aluminate phases.

For the first time a patent for cement was registered in 1824, in England, by D. Aspind. Then the author of the patent mixed lime dust with clay, processed the mixture by means of high temperature. The result was gray clinker. Then the material was ground and filled with water.

What is cement made of today? Clinker is still the main component of the cement. It is on him that properties and strength depend. building material... In addition, the composition includes active mineral additives (15%) in accordance with production standards. They insignificantly affect the basic properties and technical characteristics of the building material. If you increase the amount of additives to 20%, then the properties of the cement will be slightly changed, and it will be called pozzolanic cement.

In a scattered state it is 900-1300 kg / m3, compacted - up to 2000 kg / m3. m. Calculating the storage capacity of warehouses, the weight of cement is 1200 kg / cu. m. Cement production without additives is regulated by GOST 10178-76, with additives - GOST 21-9-74.

The main characteristics of cement

Depending on what the cement is made of, the material has different properties. The main ones include:
1. Strength... This is a parameter that is responsible for the destruction of the material under the influence of certain conditions. Depending on the mechanical strength, four types of cement are distinguished: 400, 500, 550 and 600.
2.. It is determined by laying a cement paste of normal density on a flat surface - the cement should change its volume evenly when it dries. Otherwise, it will not be possible to use it in construction due to possible destruction of the coating as a result of excessive stress. Volume changes are checked by boiling the cured cement cakes.
3. Grinding grain... The parameter affects the drying rate and strength. The finer the grind, the better and stronger the cement, especially in the first stage of hardening. Grinding grain size is determined by the specific surface of the particles that are part of 1 kg of cement, and ranges from 3000-3200 kg / cubic meter. m.
4. Density... Water consumption to create a mixture. This is the amount of mixing water required to properly lay and dry the material. To reduce its consumption and increase the plasticity of cement, plasticizing organic and inorganic substances are used. For example, sulphide yeast mash.
5. Frost resistance... The parameter allows you to determine the ability to withstand temporary freezing of water, as a result of which its volume increases by 8-9%. Water presses on the walls of the cement (concrete) coating, and this, in turn, disrupts the structure of the solution, gradually destroying it.
6. Coupling with reinforcement.
7. Heat dissipation - heat is generated in the process of cement hardening. If this happens slowly and gradually, then the coating hardens evenly, without cracking. The amount and rate of heat release can be reduced by using a special mineralogical composition, which is added to the solution.

Many types of cement are produced today. What cement is made of is to a greater extent also affects its properties. Depending on the raw material base, the following types of cement are distinguished:

• lime;
• marly;
• clay cement with slag and bauxite additives. Its peculiarity is water resistance, frost resistance, fire resistance.

Basically, in the manufacture of cement, clay and carbonate compounds are used. Sometimes - artificial raw materials (waste, slags) or other natural materials (alumina residues).

Distinguish. Portland cement hardens quickly and can contain mineral additives from 10 to 15%. Clinker and gypsum (the main components) that make up it are fired at a temperature of 1500 degrees Celsius. Portland cement is actively used for modern construction work. Its main property is the ability to turn into a solid block of stone even when interacting with water.

In addition to Portland cement and slag Portland cement, the following types of cement are distinguished:

• hydraulic;
• straining - tends to quickly set and dry;
• plugging - designed for concreting gas and oil wells;
• decorative (white);
• sulfate-resistant - its distinctive feature - low speed of hardening and increased frost resistance.

Areas of use

Very often, cement is used in construction to create concrete and reinforced structures. Grade 400 is used for foundations and floor beams in high-rise buildings.

It is difficult to imagine an area of \u200b\u200bconstruction where no cement would be used. It is necessary at all stages of any construction process, from the arrangement of the foundation to interior decoration premises. Until now, analogues of this building material have not yet been found, which indicates the unique properties of cement.

What cement is made of, description

Cement is a crushed clinker powder, in which modifying additives and fillers are introduced. In dry form, it is a free-flowing homogeneous mass gray... When diluted with water, a paste-like binder is obtained that is easily applied to any rough surfaces.

After the cement hardens, a strong connection is formed, which is not inferior in its density to stone. It is not for nothing that artificial stones are made from cement.

Chemical composition and formula

When limestone and clay is heated to a temperature of about 1450 degrees, the structure of these materials changes, as a result of which clinker granules are formed. These granules are mixed with gypsum and ground to a powder. The chemical formula of the finished cement is as follows: 67% calcium oxide (CaO), 22% silicon dioxide (SiO2), 5% aluminum oxide (Al2O3), 3% iron oxide (Fe2O3) and 3% other components.

rather complicated and time consuming. It requires special equipment and compliance with technological standards and conditions.

Specifications

The main technical characteristic is cement grade... It is designated by the letter "M" and a digital indicator. The numbers indicate the maximum load in kilograms for a given volume of cured cement, i.e. its compressive strength.

In practice, this means the weight that the cement can support without breaking. For example, if it can withstand a weight of 200 kg, then the cement is assigned the M200 grade.

In addition to the brand, the packaging also indicates the percentage composition of additives... It is designated by the letter "D" and shows what it consists of given view cement. For example, the symbols "D10" mean that 10% of additives have been added to the dry mixture.

Such additives are introduced to improve water resistance, corrosion resistance, frost resistance and other properties of cement. Let us also consider other characteristics of cement that should be paid attention to when performing construction work.

M400... Its strength is 400 kg / cm2. It is the most popular cement grade used universally for all types of construction and finishing works... This is the construction of buildings, monolithic construction, the production of concrete slabs, blocks, staircase structures, foundations, well reinforced concrete rings, paving slabs and a whole range of other products.

M500. Strength is 500 kg / cm2. This brand of cement is characterized by fast solidification and high strength indicators. Cement is used for the monolithic construction of high-rise structures, the manufacture of load-bearing elements, floor slabs, prefabricated reinforced concrete structures, beams, as well as in other cases requiring increased strength and durability of structures.

In addition to brands, classes, types and degree of grinding, which differ in the combination of individual components and composition.

According to GOST. The production of general construction cements should be based on the requirements of GOST 31108-2003. The standard regulates the ratio of the required components in the dry mix and the technology for making cement. This does not include special formulations.

Activity. This is the strength of a single sample cement mortar for compression. Experts compare the obtained activity indicators with the standards and assign an appropriate grade to this cement. The activity indicator depends on several factors: the activity of the clinker granules, the intensity of grinding, the presence of additives. For example, active additives will significantly increase the activity of the cement itself.

Application of the automatic meter of cement activity CEMENT-PROGNOZ:

Density. The lowest density is recorded for freshly prepared cement. On some of its particles electrostatic forces act, repelling particles from their fellows. Then, in the process of transportation and storage, the mixture is caked and compacted.

The density also depends on the degree of grinding of the clinker granules. When making calculations, the indicator medium density cement is taken equal to 1300 kg per cubic meter. But in practice, the density depends on the storage conditions of the material.

Specific and volumetric weight. The specific gravity of cement is determined by the ratio of its weight to the volume it occupies. This concept is necessary for the correct composition of the proportions of cement mortars. The specific gravity of cement can vary significantly depending on the condition of the mixture. So, fresh powder can have a specific gravity of the order of 1000 kg / cubic meter, and a caked mixture - 1500 kg / cubic meter.

Volume weight calculated by the average density of the cement. The average density is approximately 1300 kg / cu. Therefore, a 50 kg bag will have about 0.04 cubic meters. Bulk density increases when cement is caked or transported.

Shelf life. Cement has a limited shelf life. Manufacturers guarantee its safety under normal conditions for 2 months. If the storage conditions are sealed, the cement can lie down without problems for a year.

It should be borne in mind that the higher the grade of the stored cement, the faster it can lose some of its properties. So, cement M500 after being in a warehouse with high humidity, in a month will correspond in quality to cement M400, and after 2 months - M300.

Bulk density. This is the ratio of the mass of loose cement to its volume. That is, this is practically the same as the specific gravity if you take a loose mixture. It is determined empirically. Cement is poured into a measuring container from a certain height. Weighing is carried out after filling the container. Knowing the weight of the empty container, determine the value of the bulk density. For fresh mixes, this figure is about 1200 kg / cu. For caked cement, the bulk density is about 1500 kg / m3.

Setting time. The prepared cement mortar sets and hardens after a few hours. In the summer, this process can occur in 2-3 hours. In cold weather, the setting process takes up to 10 hours. So, at a temperature of 0 degrees, the solution will be able to harden only after 20 hours. The additives introduced into the solution are capable of accelerating or slowing down the solidification process.

With the help of cement, they equip the foundation, plaster the walls, make the floor screed. Each of these operations requires, which in any case must be prepared with high quality.

Grinding fineness. The smaller the size of the crushed cement particles, the faster the solution hardens, and the more reliable it will be in the solidified state. The fineness of grinding directly depends on the equipment used for this. The recommended particle size is 40 to 80 µm.

Certificate of conformity

Cement certification in Russia is performed according to GOST 10178-85, 30515 97, but more often according to GOST 31108-2003. All large Russian enterprises have already switched to the new GOST 31108-2003, which was adopted in 2004. It spelled out more stringent criteria for the quality of cement, as well as its testing. New requirements fully comply with European quality standards.

What is the difference between cement and concrete

Cement is a dry mixture that is used specifically for preparing concrete mortar... Concrete is cured fake diamondconsisting of cement, water and fillers. Gravel, sand, screenings, slag, expanded clay and other materials are usually used as fillers. Until the moment of hardening, concrete is a mobile concrete mixture.

Not only in construction and renovation work. If you want to make something solid and strong, you can't do without cement.

Cement strength class and strength test methods

According to GOST 31108-2003, such a term as "cement grade" has been transformed into the term "strength class". Therefore, the digital marking of cement means its strength class.

Cement strength tests are performed in a factory laboratory using modern equipment and advanced methods of analysis. In this case, the fineness of grinding, the density of the cement paste diluted with water, and the setting time of the cement mortar are determined. The compressive or flexural strength of the hardened specimens is also determined.

Determination of normal cement paste density in a virtual laboratory:

The most common bonding material in construction is cement, which is made on the basis of magnesian or carbonate-silicate rocks. The latter type occupies more than 90% of the market and is called Portland cement. The production process includes several stages, the range of produced mineral binders is wide, and it will be useful for every builder to find out by marking the field of application of the powder.

What cement is made of - the main raw material

The raw materials for production are solid minerals, near which cement plants are located. They are used in the manufacture of clinker - a product of joint firing of rocks - carbonate stones and clays. The first category of mineral formations is consumed in greater quantities and is represented by limestone varieties of amorphous or crystalline structure, these are:

• chalk is a soft rock white, consists of calcium carbonate with an admixture of magnesium, metal oxides and quartz grains;
• marl is a natural mixture of 50-75% calcite derivatives with 25-50% silicate clay formations, well suited for production;
• shell rock is limestone from the shells of marine animals, its metamorphosed by pressure at high temperature the variety is called marble;
• dolomite - in addition to calcium carbonate CaCO3, it contains a magnesium component: MgCO3.

The clayey rocks that bring silicates into the clinker are loess, loams and shales. To reduce the cost of production and give cement special properties, the technology uses alloying additives - alumina, iron, silicon, waste from metallurgical plants.

What is cement clinker

This is a product obtained by sintering at a temperature of 1450 ° C of two rocks: 75% limestone and 25% clay. The clinker comes out of the kiln in the form of granules Ø10-60 mm.

By chemical composition the calcined crushed stone of each of the manufacturers may differ, the average spread in percentage is given:

• CaO - 67;
• SiO2 - 22;
• Al2O3 - 5;
• Fe2O3 - 3.

Crushed stone from the kiln is not the only component in the production of Portland cement. To slow down the setting time of the final product, grinding the granules to a fine powder is carried out with the addition of up to 6% calcium sulfate CaSO3 contained in gypsum or gypsum stone to the clinker.

Grinding of ingredients is carried out by ball mills with pumping of the finished product into multi-ton silos by pneumatic transport.

The manufacture of cement is regulated state standards: GOST 30515-2013 - general technical conditions, GOST 10178-85 and 31108-2003 for construction Portland cement. Separate standards have been developed for special types.

Main product features

Indicators of cement density: bulk - 900-1100 kg / m³, with compaction - 1400-1700. Values \u200b\u200btrue specific gravity reach 3 t / m³. There are several technical characteristics, by which the quality of the binder powder is judged:

1. Fineness of grinding - determines: the smaller the particles, the larger the surface in one layer they cover. Control measurements are performed by scattering on a sieve with a mesh of 80 microns.
2. Water demand - the amount of moisture required to hydrate the cement and give the dough plasticity. Excessive water in the solution leads to the formation of pores and cracks, and a decrease in strength.
3. Frost resistance - the ability of products based on cement powder to withstand repeated frost and thawing without destruction. The required indicator is achieved with special additives when mixing the solution.
4. Setting time - depending on the density of the mix, it is in the range of 0.7-10 hours. The indicator also depends on the amount of gypsum added to the clinker during grinding.
5. Strength is determined from the fracture of a cement specimen from each batch of slurry released. The age of the cubes is set by the standard - 28 days.

For all volumes shipped by the cement plant, quality certificates are filled out, in which the listed characteristics are entered. Consumers independently carry out incoming checks to confirm the supplier's bona fides.

What is a brand of cement

The strength characteristic of Portland cement is its grade, which is established based on the results of compression tests of cubic specimens with a facet of 10 cm. The composition of the solution for filling forms: for 1 part of the binder powder 3 measures of pure quartz sand.

After adding water, the mass is mixed and remains solid for 28 days. 6-10 molds are poured simultaneously.

Of these, 6 samples are randomly selected and crushed under a press. The arithmetic mean pressure is calculated for 4 cubes that collapsed under the greatest load. The values \u200b\u200bmeasured in kg / cm² will indicate the cement grade according to GOST 10178-85. The display of stress in the metric system of units is performed in accordance with GOST 31108-2003 in MPa. Here, the distribution is carried out according to the strength class of the cement.

It turns out that the old and new classifications are used simultaneously to assess the strength characteristics. The digital range of brands: M200, M300, M400, M500, M600. The corresponding values \u200b\u200bof the hardness class: B15; B22.5; B32.5; B42.5; B52.5.

Marking

The given designations of the strength indicators of Portland cement are only a small part of the information on the properties of the cement produced, encrypted in the full marking.

In the context of the simultaneous use of standards with the previous designations and from 2003, many codes carry identical information.

Cement manufacturers try to convey information about the quality and properties of products using the terms of both standards.

What does the marking of cement by the type of additives mean?

In addition to the main components, additives are introduced into the composition of the binder mineral, allowing the use of cement in concrete for special purposes. Information about special properties is embedded in product labeling. Powder and additives are encrypted in letters:

• PC - Portland cement without improving additives;
• ШПЦ - when grinding clinker, slag is added in an amount of ≥20%, the product is called slag Portland cement;
• PPTs - used for concreting in waterlogged conditions (pozzolans are products of volcanoes: ash, tuff, pumice);
• SPC, SSPTs, SSSHPTs - sulfate-resistant binders, anticorrosive;
• B - fast-hardening powder;
• BC -; clinker for its production is made from kaolin and light varieties of limestone;
• G - fast-setting alumina powder, raw materials for firing are carbonate rocks and bauxite;
• GF - hydrophobic cement for concrete products in water;
• PL - plasticized, provides the convenience of laying the mortar even at low temperatures;
• VRC is a moisture-proof expanding cement that hardens in any environment.

In the GOST 10178-85 marking, the number of additives is indicated by a letter and a number of percentages: D0, D5, D20. At the end of the code, the standard according to which the product is manufactured is indicated. Example: PC 400-D20-B-PL GOST 10178-85 - Portland cement with a strength of 400 kg / cm² with additives in the amount of 20%, quick-hardening, plasticized.

Decoding of cement marking according to the new regulations

Product information coding in accordance with GOST 31108-2003 is based on the division of cement types into 5 groups, denoted by Roman numerals. The first 3 letters are taken from the name of the powder - CEM.

Each association has signs indicating the peculiarities of manufacturing:

• I - no additives Portland cement, consists of 95-100% of cement clinker;
• II - this group is subdivided into subclasses A with additives of 6-20% and B - 21-35%. There are also pozzolanic cements containing<20% пуццолана, и композитные, в которых присадки суммарно не превышают того же значения;
• III - slag Portland cement with a slag content of 36-65%;
• IV - pozzolanic cement with the addition of 21-35%;
• V is a composite powder containing 11-30% slag and, within the same range, pozzolan.

Each of the additives has its own letter in the designation: I - limestone, Z - fly ash, MK - microsilica, K - composite additive, G - glezh, W - slag, P - pozzolan. This is followed by the number of the strength class, followed by the letters: H - normal hardening time, B - fast setting. Example: slag portland cement CEM III / A 32.5N GOST 31108-2003. It stands for this: the strength of the cement is 32.5 MPa, it is normally hardening, it contains 36-65% slag.

Cement grades and their application

Portland cements are used in accordance with the labeling, which directly indicates special conditions, if any. For construction work, when choosing a brand, attention is paid to the indicator of the strength class or brand of cement.

Arrangement steps depending on the hardness of the binding powder:

• M200 - cement is intended for plastering, manufacturing;
• М300 - corresponds to the monolith М200, is used for concreting the underlying surfaces for foundations, pouring foundations for low-rise buildings;
• М400 - construction of reinforced concrete structures with strength М300, road surfaces, paving slabs, supporting structures;
• М500 - all types of external concrete works, production of airfield slabs and hydraulic structures from the М400 monolith.

The compositions of the solutions may vary and are set according to the conditions of the object being built. The formulation of the mixtures is determined by the project.