Cement is one of the few building materials without which any construction is impossible. Whether it is a monolithic reinforced concrete skyscraper or a wooden hut. After all, only in a fairy tale the hut has chicken legs. In life, however, her "foundation legs" are made of concrete. The history of the creation and invention of cement deserves a separate discussion and does not fit into the framework of our section.

So what is Portland cement made of? What are its main characteristics: types, brands. Let's talk about everything a little bit, but in essence. That is to say - for general information. Let's start with the main thing - with the production of cement.

Cement production

If you don't go into details and look superficially at the process, then the production of cement can be represented in the form of three main stages:

1.Extraction and processing of raw materials.

• Limestone, clay, gypsum are mined.
• The mined limestone is crushed, dried, crushed and mixed with clay in the required proportion. Approximately 75% limestone and 25% clay. The composition is constantly being adjusted, depending on the characteristics of the materials used.
• This is how a sludge is obtained (wet, dry or combined method)

2.Raw material roasting and clinker production is the next step in cement production

• The sludge enters a special furnace, where it is fired at a temperature of about 1450 degrees.
• At this temperature, the sludge is sintered (almost like expanded clay grains), turning into the so-called clinker.
• The clinker is crushed in special millstones to a powdery state

3.Mixing of components and obtaining Portland cement.

• About 5% gypsum is added to the crushed clinker.
• Depending on the brand and type of cement, mineral additives are introduced (numbers d0, d5, d20 in the marking)

Actually, this is where the production of cement can be considered complete. The resulting powder is PC Portland cement. The use of Portland cement is so extensive that listing cement products can take a whole page. Actually about this you can read our article cement in the production of concrete and reinforced concrete

Main types of cement

• White cement
  The main use of the business center is the manufacture of dry building mixtures. In many respects it outperforms ordinary Portland cement: accelerated strength gain, increased resistance to weathering. The initial decorativeness of reinforced concrete products from the BC allows the exploitation of architectural reinforced concrete - without additional painting and cladding. Concrete goods made of white cement - do not darken, do not fade, do not turn yellow from time to time. Also, BC is used in plaster solutions, for the manufacture of colored surfaces decorated with a stone, etc. To do this, white cement is mixed with coloring pigments.
• Fast hardening cement
  Often, cements that include active mineral additives in their composition are in lower demand than their additive-free counterparts in the cement workshop. The reason for this is the slower setting rate of the additive cement. And such a delay is capable of making its own adjustments in the terms of the formwork turnover, in the speed of concreting, and in the entire construction process as a whole. In order for builders not to be tied to the prolonged setting times of cement with mineral additives, many cement plants produce fast-setting cement. Moreover, both additive and non-additive types of cement are quick-hardening. For example: The Mordovcement enterprise produces and sells non-additive quick-hardening cement m500 d0 in bags and in bulk.
• Expanding cement
  RC is obtained from alumina cement and gypsum. It differs from other types in expansion during hardening. Almost all other types shrink (except VBC and NC)
• Waterproof nonshrinking cement
  Basically, it is used for: waterproofing monolithic structures, sealing joints between reinforced concrete elements, sealing various joints, building waterproof concrete tanks for storing various liquids.
• Hydrophobic cement
  Cement with the introduction of special additives that increase its resistance to storage and transportation in a humid environment, Also, HZ is used to obtain ready-mixed concrete with increased moisture resistance and frost resistance up to F1000
• Alumina cement
  He is aluminate and bauxite. The main advantage is that concretes made from such a binder gain strength faster: up to 50% per day. The hardening process is accompanied by a large amount of heat, which can be relevant during winter concreting.
• Stressing cement.
  Cement expanding with strength gain, intended to create self-stressed reinforced concrete structures, incl. using special types of fittings. Solutions based on such a binder are used in the manufacture of crack-resistant (non-shrinking), waterproof joints, in the overhaul and modernization of old structures, in increasing their water resistance. Concretes based on NC are champions in terms of the water resistance coefficient: up to W20, which is important for the construction of basements on soils with high GWL, monolithic roofs, reservoirs, pool bowls, etc. - without additional waterproofing device. For the first 7-10 days of curing, concrete obtained from stress cement should be in an environment with high humidity. Such concretes are characterized by increased strength, moisture resistance and frost resistance.
• Portland cement
  Portland cement. The most common and used type. Probably 99% of the cement used in construction is PC Portland cement.
• Pozzolanic cement
  Potland cement with the addition of additives containing finely ground active silica. Differs in increased setting time and reduced heat generation. What may be relevant when concreting bulk structures. Namely: Large masses of freshly laid concrete generate a lot of heat. After all, cement hydration is still an exothermic process. Well, they work out and work out what the problem is. And the trouble is that the upper layers of concrete give off heat faster and more than those inside. The thermal conductivity of concrete is small. So the uneven shrinkage turns out. In a word, it cracks.
• Sulfate resistant cement
  SC has increased protection against the destructive action of salts (sodium, magnesium sulfates). More about sulfate-resistant cement. It is used in the production of sulfate-resistant concrete mixtures. (hydraulic structures, etc.)
• Well cement
  TC is used for plugging (plugging) oil and gas wells.
• Slag cement
  ШЦ, is obtained from ground blast-furnace slag, with the introduction of additives of activators: gypsum, lime, etc.
• Colored cement
  CC is obtained by introducing white cement clinker into the composition of coloring pigments. The main purpose of CC is to obtain decorative concrete products that do not require further processing.

Cement brands

Grade strength is akin to concrete grade. The number of the brand corresponds to the resistance to axial compression in kgf / cm2 or in MPa.
How to check the brand of cement:

Determination of the brand is carried out in this way: knead a solution of cement, with a composition: 1: 3, on standard sand, with a water-cement ratio of 0.4. Beams of 4x4x16 cm are cast from this solution in special molds. Then these samples are placed in a special chamber or simply covered with a cap (not forgetting to put a vessel with water next to it to increase the humidity under the cap). Withstand 24 hours. Then the beams are taken out of the formwork and placed in the steam chamber. They are steamed and the bending strength of the obtained samples is checked. A special press is used. The results obtained are multiplied by the corresponding coefficients (for each brand of cement - they are different) and the compressive strength is obtained.

Imported cement has long been labeled in compressive strength grades. For example: Cem 42.5 - minimum (guaranteed) compressive strength at 28 days -42. 5 MPa.

Cement marking in accordance with GOST 10178-85

• type - Portland cement, slag Portland cement. It is indicated as an abbreviation PC and SHPC.
• brand
• presence or absence of min. additives: d0, d5, d20 (percentage of additives). For example: m400 d20, or cement m500 d0.
• designation of fast-setting cement with letter B
• plasticization and hydrophobization of cement. The abbreviations PL and GF.
• designation of cement made from clinker of standardized composition. Liter N
• conformity standard designation.

Classification of cement in accordance with GOST 31108-2003.

Compressive strength classes of cement are gradually being introduced in Russia. So far, this concerns mainly imported Portland cement. Our Russian cement plants are in no hurry to switch to classes. Although, some cement plants are already producing cement classified in accordance with GOST 31108-2003. The official date of the beginning of the "new life" is January 1, 2008. It was then that the Russian cement producers were given the go-ahead for new designations. However, few people are in a hurry to introduce it into production. Well, if only Mordovcement has completely switched to the new GOST. The majority are still rushing about. In general, when general "class equality" finally takes place, the main characteristics of Portland cement, in accordance with GOST 31108-2003, will be designated as follows:

• cement I - Portland cement
• cement II - Portland cement with min. additives

Portland cement with min. additives will be presented in two subtypes:

• Subtype A - the percentage of min additions 6% - 20%,
• Subtype B - the presence of 21 to 35% additives in the composition

Difference in the types of additives: granulated slag with the letter Ш, pozzolan - with the letter P. By strength classes: 22.5; 32.5; 42.5 and 52.5, Numbers - denote the minimum (guaranteed) compressive strength of the cement stone in MPa at the age of 28 days of hardening.
Also, for classes 32.5-52.5, additional designations for strength at the age of 2 or 7 days are introduced: letters: H normally hardening, B - fast hardening. In view of the fact that additional Portland cements are characterized by slower setting times, which is not quite suitable for the pace of modern construction, cement plants produce Portland cements of grades M400 D20B and Cement 42.5B, which are included in the category - fast-setting. The reduction in the curing time occurs due to the use of cement clinker of a special mineralogical composition, or due to a finer grinding of conventional cement clinker. Sometimes, to speed up the setting and hardening times, special additives for concrete are used.

On the map below you can see the location of all cement producers in the territory of the Republic of Uzbekistan.