Cement is used everywhere: from laying the foundation to the arrangement brickwork and work on interior decoration. Such a wide and even vast scope of use of cement has led to the emergence of materials with different compositions and characteristics. You can’t just buy the first cement that comes across and start work - first it is important to make sure that the composition is up to the task. When going to a hardware store, it is important to know theoretical basis, so it's time to figure out how to choose cement, find out what brands and types of cement exist, where certain compositions are used, and also what to consider directly when choosing.

No. 1. Main types of cement

Cement is an inorganic binder. Cement powder, when interacting with water, forms a plastic mass, which quickly sets and forms a stone-like body. Often used to make and mortars. The composition of cement can vary greatly. Accordingly, the properties and scope of use will differ.

Today, the following main types of cement are produced:

• Portland cement- the most popular type of cement in construction. Produced from Portland cement clinker, gypsum and special additives. Clinker is obtained from limestone, clay and additives by firing. Ready Portland cement consists of 70-80% calcium silicates, the rest is gypsum (regulates the setting rate) and corrective additives. Portland cement is produced in grades M400-M600, used to create mortars, asbestos-cement and other materials. Not suitable for the construction of structures exposed to sea water;
• white portland cement are made on the basis of gypsum, diatomite and clay-sandy rocks with a minimum content of colorants. The result is a compound with high strength, weather resistance and fast setting. Only two brands M400 and M500 are produced. Often the composition is used for external finishing works, since it has aesthetic appearance and is not subject to cracking. It is used for the manufacture of decorative elements (statues,), in the organization of self-leveling floors, in road construction, c. Made from white Portland cement colored compositions;
• sulfate-resistant Portland cement produced on the basis of Portland cement clinker and gypsum. The composition is characterized by a reduced content of calcium aluminates, which ensures resistance to sulfates. Cement can be without additives or have additives in the form of granulated slag. Mark M400 and M500. It is used in the creation and construction of structures that will be operated under the influence of mineralized waters. Such cement is used in the manufacture of piles, bridge supports, in the arrangement of external elements of hydraulic structures;
  
• pozzolanic portland cement obtained from Portland cement clinker, gypsum and additives of sedimentary origin, part of which is 20-30%. The composition is resistant to fresh and sulfate-containing waters, water impermeability. Among the minuses is low frost resistance and low speed hardening. Used for pouring and laying basements of industrial and civil buildings, in the construction of the subway, mines, canals, locks, water communications;
• slag cements- a group of cements, which includes slag Portland cement (SHPC) and lime-slag cement (IShTs). The first is obtained on the basis of Portland cement clinker, gypsum and blast-furnace slag, part of which is 21-60%. The composition is characterized by a slow increase in strength, increased resistance to aggressive environments, but is not resistant to temperature extremes. It is used in hydraulic engineering construction. ISHZ is obtained from a mixture of slag with lime (its part is about 30%), small additions of gypsum and Portland cement are allowed. The composition slowly hardens, the most stable in fresh and sulfate waters ah, can be used for the manufacture of low-grade concretes, in mortars for and masonry;
  
• fast setting portland cement, as the name suggests, is characterized by a rapid set of strength in the first hours of hardening. Such properties are explained by the exact selection and dosage of special additives. As a result, the composition reaches the tensile strength after 3 days, which speeds up the production process. reinforced concrete structures;
• aluminous cement also different high speed hardening and hardening. Produced on the basis of bauxite or alumina with the addition of limestone. According to the content of alumina, ordinary (up to 55% alumina), high-alumina (up to 65%) and extra-pure high-alumina cements are distinguished. The compositions have high resistance to fire, corrosion and a rapid increase in strength. Such cement has found application in emergency work, high-speed construction and winter concreting;
• expanding cements- a group of cements that are characterized by an increase in volume during hardening. A similar effect is achieved due to the passage of the reaction between the powder and water, resulting in the formation of calcium hydrosulfoaluminate, a substance capable of binding a large number of water. In the group of expanding cements, waterproof, stressing, gypsum-alumina compositions and expanding Portland cement are distinguished. Let's consider all of them separately;
  
• waterproof expanding cement made of gypsum, aluminous cement and calcium hydroaluminate. The composition begins to set after 4 minutes, and after 10 minutes the hardening process is already over. It is used in underground and underwater construction, for sealing cracks and when creating monolithic structures from individual precast concrete elements;
• stress expanding cement produced from Portland cement clinker, lime, aluminous slag and gypsum stone. The composition hardens relatively quickly, is waterproof. Used in concreting bowls, production of pressure pipes;
• gypsum alumina expanding cement are made from aluminous blast-furnace slag and gypsum. The composition sets within 4 hours, the expansion ends after 3 days. Cement is characterized by high frost resistance, strength and deformation resistance. With its help, waterproofing works are carried out;
• expanding portland cement is a mixture of Portland cement clinker, slag with a high content of alumina, gypsum and mineral additives. Depending on the composition, the expansion ranges from 0.3 to 2.5%. The expansion period is long, so the volume is filled evenly. Used in furnishing pavement and repair of hydraulic structures;
• well cement used only when plugging oil and gas wells in order to isolate them from ground water. Produced from clinker and gypsum;
• hydrophobic cement in its composition, in addition to gypsum and clinker, has oleic acid or other hydrophobic substances that allow you to create on the surface of the dried cement waterproof film. Such cement is ideal for the foundation;
• magnesia cement differs in the content of magnesium oxide, due to which the elasticity of the composition increases, its resistance to aggressive substances. Used in the arrangement;
  
• waterproof non-shrink cement obtained on the basis of aluminous cement, gypsum and slaked lime. The composition sets quickly and is not afraid of water;
• acid resistant quartz cement- product of mixing quartz sand, sodium silicofluoride and liquid sodium glass. The composition is resistant to aggressive substances, but loses strength in water;
• cement with surface-active additives has increased mobility and is used when working on objects that are complex from an architectural point of view.

No. 2. Grades of cement by strength

The most important characteristic cement of any kind is its strength. This indicator is determined experimentally: a mortar is prepared from cement and in a ratio of 1: 3, a sample is created in the form of a parallelepiped with sides of 40 * 40 * 160 mm. The resulting sample is subjected to a gradually increasing load. The experiment is slightly different only for some types of cement.

The data obtained in the course of laboratory studies are reflected in the stamps. If the sample can withstand a load of 300 kg / cm 2, then this is the M300 brand, 500 kg / cm 2 - M500, etc. The grades are indicated by the letter M and the subsequent index from 200 to 600 in increments of 50 or 100. The higher the grade, the more durable the composition in front of us, and the more durable and high-quality concrete it will turn out:

Today, next to the classifications of cement by strength grades, a division into strength classes. If the brand is an average indicator, then the class is more accurate and provides a 95% guarantee of compliance with the specified data. Strength classes vary from 30 to 60:

• 52.5 - cement withstands a pressure of 52.5 MPa, corresponds to cement grade M600;
• 42.5 corresponds to cement M500;
• 32.5 corresponds to cement M400;
• 22.5 corresponds to M300 cement.

No. 3. Labeling of additives in cement

In addition to the strength grade, on the packaging you can see the marking of the percentage of various additives in cement. This indicator is denoted by the letter D, followed by a numerical indicator in percent. For example, cement D20 means that it contains 20% additives. The higher the number of additives, the lower the price of the composition.

No. 4. Curing rate marking

The time it takes cement to reach its maximum strength is another important indicator of composition. In some cases, it is required that it hardens instantly, in others, on the contrary, an excessive rate of curing will only hurt. According to this parameter, cement is divided into the following types:

No. 5. What else can be in the marking of cement?

In the characteristics of the composition, after the designation of the brand of cement and the percentage of additives, there may be various abbreviations indicating the specific qualities of cement:

No. 6. What to look for when choosing cement?

The demand for cement is huge, which has given rise to the emergence of many unscrupulous manufacturers who often mix additives into cement that greatly reduce quality. finished composition. In order not to make a mistake when choosing cement and buy really quality goods, you need to know something about what good cement looks like and what properties it should have:

• cement is sold in bags and in loose form. It is better to take cement in bags, because this way it is protected from external influence, retains its qualities longer, and on the packaging of the bag you can always find out information about the composition, production date, characteristics of cement and its manufacturer. Bags are usually made of two layers of paper, the inner one protects the cement from getting wet. By the way, the absence of any information on the packaging is also a sign that you may have low-quality material in front of you;
  
• if you buy cement in bulk, and it is packaged in bags, then it is better to check carefully best before date on each, since in the total mass you can be sold stale goods. The activity of cement after 6 months from the date of production drops several times;
• check freshness of cement possible by experience. It is enough to hit the bag - the sensations should not resemble a hit on a stone. The cement is the first to harden in the corners of the bag, so it also does not interfere with checking them. Naturally, if there is no production date on the package at all, then it is better not to take such a product;
• cement must be stored in dry and well-ventilated areas, otherwise it will quickly harden;
  
• quality cement color- gray, more precisely from light gray to dark gray and even greenish. Dark and marsh shades are not allowed. Good cement should crumble in the hand, and when compressed, it should not crumple into a lump;
• The fineness of the grind affects the curing process. The smaller the fraction of particles, the faster the composition will harden and the higher its price. Too fine a fraction increases water consumption, so ideally it is better to take cement where fractions from 40 to 80 microns are found;
• does not interfere with assessment of the composition and characteristics of cement. It is not difficult to do this, but in advance it is necessary to prepare bicarbonate-sodium water (Borjomi is suitable) or bicarbonate-chloride-sodium. It is necessary to release gas from the water. Next, we use it for kneading cement dough and forming cakes with a diameter of 15 cm from it. In the center it should be thicker (5 cm), narrower towards the edges (1 cm). High-quality cement should begin to set no later than after 10 minutes, and the thickened part will noticeably heat up. If setting does not occur even within 30 minutes, then you have a composition of poor quality.

No. 7. The best cement manufacturers

Finally, we emphasize once again the need for information on the brand of cement, its properties, production date and contact details of the manufacturer on the packaging.

What is Portland cement?

Impossible to imagine production construction works without binders connecting in monolithic structure blocks, slabs, bricks. Portland cement is the most common and in demand in this category of materials.

Mixing with water or solutions of various salts, cement forms an elastic mass, which, in the process of drying, turns into a cement stone. Without the use of mortars based on Portland cement, it is impossible to manufacture reinforced concrete structures, monolithic structures, high-quality mixtures for masonry and finishing activities.

Portland cement is produced by combining finely ground clinker with a small amount of gypsum, which speeds up the setting process of the mixture. During production, depending on the requirements for the mixture, various additives are added that increase the resistance of the material to the effects of negative factors.

One of the most common types of binder for concrete mixtures- Portland cement

Kinds

To give the finished product certain properties, Portland cement is enriched with mineral additives - belite, alite, celite, brownmillerite. Depending on the mineral components used, Portland cement is divided into the following types:

• Characterized by average speed setting.
• Fast curing compound.
• Plasticized.
• Moisture resistant, hydrophobic.
• With increased heat output.
• Particularly resistant to chemicals.
• Decorative (color or white), used in finishing work.

Grades of cement

Based on the requirements of regulatory documentation for a cement sample subjected to compression and bending tests, the main grades of Portland cement can be distinguished:

• M700- especially durable composition. The scope is limited to the production of concrete with increased strength characteristics for the construction of stressed structures. The price of such cement is high, which makes it unprofitable for conventional construction activities;

Any type of Portland cement grade 400 is used to create conventional and standard structures that are not subject to increased loads.

• M600- composition of increased strength. Scope - production of responsible reinforced concrete products and structures;
• M500- cement, which has sufficiently good strength characteristics, which allows it to be used in the reconstruction of buildings and structures after accidents, the construction of military-technical facilities, laying the road surface;
• M400- the most affordable and widely used brand. This is explained by the fact that the inherent indicators of frost resistance, moisture resistance make it possible to use it in the construction of objects for any purpose.

Manufacturers produce Portland cement grades M200 and M300, but in rather limited quantities. This limitation is natural, since the demand for these brands is low.

The numerical index indicated in the marking of Portland cement indicates the amount of pressure that the reference sample of the material is able to perceive. For example, Portland cement, marked M500, perceives pressure in excess of 500 kg / cm².

Main raw material used

In the manufacture of Portland cement, lime and clay rocks are used in a certain proportion, providing the required chemical composition for roasting.

All types of Portland cement (PC) are made from different raw materials; only cement clinker is a common component for all

From calcareous rocks most often used:

• Limestone that does not contain silicon inclusions. Dense rock with fine crystalline structure.
• Marl is a transitional rock from limestone to clayey. Includes in its composition small particles calcium salts with an admixture of feldspar, dolomite, etc.
• Chalk is a malleable, easily crushed sedimentary rock.
• Shell limestone.

The clay component includes:

• Clay shales. Due to their layered structure, they are easily split, which greatly facilitates processing.
• Loess. Loose fine-grained rock containing a large amount of calcium carbonate.
• Clay. It is a mixture of the main clay substance - hydroaluminosilicate with compounds of iron, magnesium and other elements.
• Loams. They differ from clay in the increased content of sand.

To save natural raw materials and reduce the cost of cement production, waste is increasingly used metallurgical industry(sludge, ash).

Mineral constituents of clinker

To obtain the main component of Portland cement - clinker, the raw mixture (limestone + clay) is fired. As a result of this operation, mineral compounds are formed, the percentage of which should not exceed the allowable values.

In most cases, clinker is obtained from artificial mixtures, because in nature, raw materials containing approximately 75% calcium carbonate and 25% clay are quite rare.

The main minerals that determine the properties of the resulting clinker include:

• fast hardening alite. This component is responsible for the rate of hardening of the composition and the increase in operational strength. Its quantity is regulated within 45-60 percent;
• slowly hardening bleach. Its presence allows cement compositions to achieve high strength characteristics during long-term hardening. So that the belite does not lose its binding properties, the clinker is cooled as quickly as possible. The amount of the mineral is kept within 20-35 percent, which makes it possible to achieve optimal timing hardening;
• fast hydrating tricalcium aluminate, accelerates the hydration process, but at the same time reduces the strength characteristics and increases the possibility of corrosion. Therefore, the content is limited to 4-10 percent;
• the aluminoferrite formed at a certain firing phase does not significantly affect the processes of hardening and heat generation. Its content in clinker is in the range of 10-18 percent.

Since Portland cement is obtained from raw materials of different chemical and mineralogical composition, the output is cement that differs in properties. Using proven production technologies, adhering to the developed recommendations on the percentage of mineral inclusions, manufacturing enterprises will receive a high-quality product that meets the required parameters.

Production technology

Disputes over which method of producing a cement composition is better do not subside long years. There is an opinion that, using a heterogeneous raw material high humidity, it is preferable to use wet way. In parallel with this, the position is defended on the use of the dry method, as more economically feasible, if the charge is properly prepared in advance.

The clinker mixture is fired at high temperatures(up to 1500 ° C), obtaining granules at the exit, which are then crushed

Let's try to understand the main differences existing methods production of clinker from which Portland cement is obtained. There are three options for obtaining a mixture for firing:

• Wet. Initially, the components are crushed to the desired size (limestone - particle size 8-10 mm, clay - pieces up to 10 cm). The clay is soaked to 70% moisture and sent to limestone mills where mixing takes place.
• Dry. The technology makes it possible to produce Portland cement using a reduced method at reduced costs. This is due to the combination of technological stages, which make it possible to simultaneously dry the ingredients and grind them in special mills into which hot gases enter. The resulting charge material is characterized by a powder composition.
• Semi-dry (combined). This method combines elements of dry and wet manufacturing techniques used by manufacturers cement mixtures. It is allowed to reduce the moisture content of the charge material produced wet method, and obtain a charge composition, the moisture content of which does not exceed 18%. According to the second method, a dry mixture is prepared, which is saturated with water to 14% moisture content, granulated and fired.

Composition Properties

Portland cement has a complex positive characteristics for its widespread use in housing construction in the construction of industrial structures. The main characteristics are:

• specific gravity, depending on the degree of compaction of the composition. For bulk mixtures it is 1100 kg/m3, for compacted mixtures it reaches 1600 kg/m3;
• granulometric composition characterizing the fineness of the cement fraction and the quality of grinding. The parameters affect performance characteristics, intensity of solution hardening. The average particle size of cement is about 40 microns, which provides the necessary strength and hardening time;

• water consumption, which affects the ability of the array to absorb a certain amount of liquid. The lack of moisture reduces the strength, and the excess causes the delamination of the cement mass. According to a proven recipe, 25-28 percent of water is introduced for kneading of the total volume of the mixture;
• setting time, regulated by the standard, up to 45 minutes after mixing with water. The duration of the final curing depends on temperature regime and slows down in winter;
• high strength characteristics, allowing to perceive compressive loads, which is reflected in the designation of Portland cement.

Conclusion

The information presented in the article about Portland cement, which is common in the construction industry, introduces the features of production, properties, marking and technological features manufacturing. Developers confirm that this durable material, providing a high service life of structures and structures.

Increased performance provides broad scope popular material.

Before starting construction work and purchasing building materials of any kind, we recommend that you familiarize yourself with the factories producing these building materials, as well as reviews about the quality of the products. This must be done, first of all, in order to be sure of the authenticity of the purchased material and be ready for the appropriate quality of the material when buying a particular building material.

There are not many cement manufacturers in Russia. As a rule, the manufacturer packs cement in bags weighing 5 kg, 10 kg, 25 kg and 50 kg. The sale of cement from the manufacturer's plant occurs to sales representatives or directly to construction companies.

Thus, in order to buy high-quality cement, you must directly contact a sales representative who sells the products of this manufacturer's plant. Cement packaged in bags will ensure the reliability of product quality.

When buying cement Special attention be given to packing cement. The packaging should indicate, first of all, the brand of cement (M500), the name of the manufacturer, the legal address of the manufacturer's plant, telephone numbers of sales departments, address Email, GOST products, product weight and product composition. In addition to the design of the packaging, the packaging itself must also meet the requirements. For example, cement packaged in a 5 kg bag should consist of five layers of paper and a sixth protective waterproof white layer.

During the period of active construction work, this is the beginning of spring - summer, products of unknown companies appear on the market. These firms buy bulk cement from the manufacturer's plant and package it themselves. In this case, it is difficult to obtain a quality assurance.

As a rule, the products and packaging of such “commodity producers” differ from those of trade distributors that have proven themselves in the market. Most often, the packaging does not contain all the necessary information about the manufacturer and the composition of the product. Therefore, the packaging is business card purchased goods. Fake products may also not have the exact weight, but rather its lack.

Thus, to minimize the risks of buying low-quality goods it is necessary to buy cement either directly from a sales representative or from retail chains that have established themselves in this market.

Requirements and GOSTs

Cement, like other goods, is produced in accordance with the established state standards. V Russian Federation there are two GOSTs for cement such as,.

GOST 10178-85 corresponds to the following characteristics:

1. The external qualities of cement, the name is Portland cement and Portland slag cement. There is an abbreviated name for the characteristics of cement PC and ShPTs.
2. A brand of cement that corresponds to a certain quality of the material.
3. The presence of the letter "B", which indicates the speed of cement hardening.
4. The presence of impurities in cement and its percentage. DO - without additives, D5 - additives not more than 5%, D20 - additives not more than 20%.
5. Additional qualities of cement such as hydrophobization or plasticization (GF, PL).
6. The presence of clinker in the composition of cement is marked with the letter "H".
7. The presence of a symbol corresponding to the standard.

V industrial production cement is produced from grade M100 to M700. The brand of cement gives a technical characteristic that the finished product from the corresponding brand of cement can withstand.

Letter and numeric coding corresponding to a certain standard is written on the package. For example, M500 DO, which means cement grade 500 bad additives. The numerical designation indicates strength finished product when it is squeezed kg / cc. When testing the strength of cement, take half of the prisms measuring 40 x 40 x 160 cm.

Means that one cubic centimeter can withstand a compressive load of up to 200 kg.

M300 cement means that one cubic centimeter can withstand a compressive load of up to 300 kg.

Means that one cubic centimeter can withstand a compressive load of up to 400 kg.

M500 cement means that one cubic centimeter can withstand a compressive load of up to 500 kg.

Thus, the main difference between M300 cement and M500 cement is the amount of withstand load per 1 cubic centimeter. That is, in its strength and ability to withstand loads.

Mainly used in the construction of foundations and load-bearing structures. This type of cement has the necessary strength and ensures the reliability of the structure. In addition, this brand of cement is moisture resistant and suitable for use in climatic conditions in high humidity.

M300 grade cement is used for internal works such pouring floor screed, interior work.

The main difference between cement 300 and 500 is its strength.

How to distinguish cement M300 from M500?

Most reliable way These are laboratory tests. But, alas, they are not always available. At home, you can distinguish cement 300 from 500 and check its quality by preparing a solution in mineral water and by touch. And in this one you will learn how to distinguish cement grade M300 from M400.

Take mineral water and prepare on its basis a cement mortar from the selected brand of cement. And by going to this one you will read how the difference between the brands of cement M500 and M600. When preparing the solution, it will heat up and may boil. For this you need to use protective equipment in the form of glasses and gloves. Make a pancake from the prepared solution.

A high-quality solution should warm up, a bad one - not always. In addition, high-quality cement will not harden after 15-20 minutes, and vice versa, cement Low quality will seize in parts, when dried it will crack. Cement good quality, being in a wet state, should not burst and crack.

Freshly prepared cement, if taken in hand, will be sieved between the fingers. Cement prepared a few months ago will set into a lump. Cement that sets into a lump can be used if this lump can be kneaded in the hands. If the cement is kneaded in the hands, then it can be used for construction. But it must be remembered that the consumption of cement will increase from 20% to 50%.

Also keep in mind that the shelf life of cement is 12 months. With each month of storage of cement, its quality decreases by about 5 percent per month. Therefore, the consumption of cement increases.

In order to avoid additional financial costs, buy cement from well-known manufacturers from reliable suppliers and a recent preparation date.

Comments:

Cement is used to perform many construction works as a binder. Portland cement is considered the most common variety. This material belongs to the group of hydraulic binders - it hardens when water is added. Portland cement is characterized by excellent binding properties and the ability to increase its hardness limit by outdoors as a result of a combination of chemical processes occurring in it.

Portland cement has good binding properties and the ability to increase its hardness limit in the open air.

Mineralogical composition

Portland cement is produced by fine grinding of clinker, gypsum and various additives.

In most cases, clinker is obtained from artificial mixtures, because raw materials containing approximately 75% calcium carbonate and 25% clay are quite rare in nature. Most cement plants operate on specially prepared raw mixes with the optimal ratio of components to obtain a quality product.

The clinker mixture is fired at high temperatures (up to 1500 ° C), obtaining granules at the exit, which are then crushed. The percentage of gypsum does not exceed 5%. It is introduced into the working mixture to ensure the mobility of the cement paste for 45 minutes required for molding products or performing certain jobs.

To provide Portland cement with the necessary specifications, often use active clinker mineral additives, the share of which can be 20 - 25% of the total mass of raw materials:

1. Aluminate - characterized by a high solidification rate and rather low strength indicators. Such qualities determine its content in cement no more than 15%.
2. Alumoferrite - its addition in the range of 10 - 18% allows to reduce the hardening time. The action of this mineral is similar to aluminate.
3. Belit - slowly hardens and has an astringent effect, has medium strength characteristics. Belite additives allow you to adjust the hardening time (slow down), however, too much of this substance can adversely affect the strength of the cement. In different grades of Portland cement, it can contain from 15 to 37%.
4. Alit - its content in the finished Portland cement is the highest - up to 60%. It provides fast hardening to cements of high grades.

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Brands and main characteristics

The brand means the tensile strength of the sample tested for compression, bending. For its manufacture, a solution of sand and cement is used in a ratio of 1: 3, from which a sample of 4 x 4 x 16 cm is formed. The test is carried out 28 days after pouring, and its hardening should occur in conditions of high humidity.

Otherwise, the strength of the sample may be significantly reduced. To speed up the hardening process, steaming of the samples is allowed. Currently, the most common brands are 400, 500, 600.

In addition to strength, Portland cement has the following characteristics:

1. Seizure period. High-quality Portland cement, subject to the proportions after adding water, should set in 40 - 45 minutes. The fineness of grinding, temperature, and mineralogical composition have a direct influence on this indicator.
2. Water requirement - determines the amount of liquid to prepare the solution optimal density. Usually the water content is in the range of 25%. To reduce water demand, plasticizers or sulfite-yeast mash can be used.
3. Water separation is the extraction of water in the prepared solution, which occurs under the influence of the gravity of the cement particles. To reduce water separation, special mineral additives are often used.
4. Frost resistance is the ability to withstand a certain number of freezing and thawing cycles without loss of strength and integrity. As additives that can increase this indicator, washed wood pitch, sodium abietate are used.
5. Heat generation is the ability of cement to release heat during the curing process. Cement, which is characterized by too rapid heat release, is optimized with the help of active mineral additives.
6. Corrosion resistance directly depends on the degree of porosity of the finished concrete and the fineness of the grinding of cement.

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Varieties of Portland cement

Depending on the properties and scope of use, Portland cement can be divided into several main groups:

1. Quick-drying cement, due to special additives of slags and minerals, hardens already in the first 3 days. This allows you to significantly reduce the holding period of the monolith in the formwork. Marks of fast-hardening Portland cement - M400, M500.
2. Normally hardening cement does not contain additives that affect the hardening lines, and does not require particularly fine grinding. This product corresponds to the characteristics defined in GOST 31108-2003.
3. Plasticized Portland cement is distinguished by special plasticizer additives that provide the cement mortar with the required mobility, density, thermal stability, and minimal moisture absorption.
4. Hydrophobic cement is obtained by introducing asidol, mylonafta and other hydrophobic additives. It is characterized by a slight increase in the setting period and the ability to not absorb moisture.
5. Sulfate-resistant is used to obtain frost-resistant concrete in the construction of structures exposed to sulfate waters. This cement prevents the development of sulfate corrosion. Grades 300, 400, less often 500 are produced.
6. White Portland cement is made from pure limestones and white clays. For additional bleaching of the resulting clinker, it is cooled with water. Cement is produced grades M400, M500. The main scope of application is finishing and architectural work, the basis for colored Portland cement.
7. Portland slag cement is used to produce heat-resistant concrete. Due to the low frost resistance coefficient, it is used in the construction of various structures under water, underground and on the ground. It is characterized by a high content of metal particles due to the addition of blast-furnace slags.
8. Slag-alkaline cement contains additions of alkali and ground slag, possibly with clay inclusions. Seizes in the same way as ordinary sandy Portland cement, but is characterized by high resistance to aggressive environments, low temperatures, has a low moisture absorption rate.

Markings and difference different brands cement from each other. Which one to choose?

Cement is the most commonly used building material.

Not a single construction or repair can do without it. To choose a truly high-quality cement, you should understand how one brand of material differs from another and which one should be chosen for construction.

For home master accustomed to doing everything with his own hands, this problem is all the more urgent - because sometimes the fruits of many days of work nullify low-quality materials.

On the pages of our site, the issue of using cement was raised in almost every second article.

It is also used for interior finishing work, for example, for the preparation and installation of self-leveling floors.

Cement like any other construction material, differs in physical and technical characteristics, depending on the conditions under which it is supposed to be operated. It is not difficult to choose it, the main thing is to understand the intricacies of marking and find a suitable supplier.

Choosing cement

Cement is labeled according to two characteristics, such as the ability to withstand a certain load and the composition of the material.

The first parameter is denoted by the letters M (PC) and a number indicating the maximum strength properties of cement. For example, the M400 marking indicates that this type of cement is able to withstand a load of 400 kg / cm. The second parameter is denoted by the letter D and a number showing the amount of additives as a percentage. For example, cement labeled D20 contains 20% additives. Their number directly affects the plasticity and strength of the material.

Many people think that the numbers in the marking indicate that measure (part) of sand, which is necessary for the preparation of high-quality mortar. In fact, this is far from the case - the numbers 400, 500, etc. in the marking of cement, this is nothing more than production characteristics its strength. They are given when testing cement at the factory, when a cube formed from cement is subjected to weight tests - if it collapses under a pressure of 400 kilograms, then such cement is assigned grade 400, 500 - respectively M500.

On the front side of the bag, the name of the product, the trade mark and the relevant state standards must be indicated. On the reverse side look for the weight, density and other technical specifications of the product, as well as the address and phone number of the manufacturer.

In private and agricultural construction, cement is most often used, or, as it is also called, Portland cement grades M (PC) 400 / D20 and M500 / D20. The first has increased frost and water resistance. It is usually used in the manufacture of precast concrete, wall slabs, foundations, etc. The second one is ideal for plastering, masonry, other repair and construction work and the preparation of various mortars. In addition to good water and frost resistance, this type of cement has a reduced resistance to corrosive effects.

Before buying cement, carefully study the packaging in which the material is packaged. In addition to the brand and weight, the manufacturer must be indicated on it - the name of the company, country and city. Remember that when buying a bulk batch of loose cement, you run the risk of purchasing low-quality or expired goods. Also ask under what conditions the material was transported and stored: the quality of cement is greatly affected by the environment, especially high humidity.

We offer several practical advice, which will help you choose really high-quality cement, as well as properly transport and store it.

Check not only the integrity and labeling of the package, but also the cement itself - whether it is prone to pelletizing. To do this, take a little substance and squeeze it in a fist. Fresh cement will easily seep through your fingers, but one that has been sitting in a warehouse for a long time is likely to turn into a lump.

Read also in detail: In addition, the quality of cement can be determined by the date of its manufacture and expiration date. The longer the cement is stored, the more its quality indicators decrease. So, after six months, its activity decreases by almost a third.

To preserve all the qualities of cement, it must be transported in compliance with certain requirements. Cement is a pulverized cargo, the loss of which as a result of spraying during transportation and loading and unloading operations on non-specialized rolling stock reaches 5-10%. In addition, cement hardens when even a small amount of moisture gets on it, and when the shelf life increases, it becomes caked. Cement dust is harmful to humans and environment, therefore, it is necessary to transport this material in closed, sealed tanks - cement trucks.

It is best to use cement immediately after purchase. If for some time it needs to be stored, it is better to do this in a well-ventilated and well-protected room from moisture. For the winter, paper bags with cement are recommended to be additionally placed in plastic bags. Loose cement can be stored in drums tightly wrapped plastic wrap. And be sure to ensure that the shelf life of cement does not exceed six months.

Preparation of the simplest cement mortar:

1. Cement is poured first, and then water is added (average 1 part water to 3 parts cement).
2. The finished solution is a homogeneous mass of sour cream consistency.
3. The mixture is stirred with a special mixer.
4. Trowel and spatula prepare the portions necessary for a particular type of work.