General information and classification of concrete.

Comments:

Types of concrete are represented by a wide variety of artificially obtained materials due to the hardening of a compacted mixture containing a binder, aggregate particles, and water.

The quality of concrete is determined by the exact ratio of cement and other parts of the concrete mixture. The very state of cement plays an important role for the future composition. A mixture of several components that has not yet hardened with the inclusion of cement is called a concrete mix.

The most widespread in construction are the types of concrete in which high-quality Portland cement grade M 500 (400) is used.

Classification of varieties of concrete

There are concretes different type. And they differ in the main parameters:

• purpose of use;
• type of binder;
• density.

The concrete composition with the inclusion of cement is nominal and is working. Rated is produced by mixing aggregates in dry form. The working composition is performed by the method of recalculating the nominal type depending on the moisture content of the mixed fillers.

Depend on the degree of density concrete composition, which consists of the density of the constituent substances and the cement stone.

According to the density index, extra heavy and heavy, light and extra light concretes are distinguished.

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Concrete mixtures heavy and light

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Characteristics of heavy mixtures

For the production of a particularly heavy variety of concrete, high-density materials act as fillers: metal scrap, hematite, barite, magnetite.

Particularly heavy compositions are used in special buildings that protect against radioactive influence. This number includes concrete, the density of which exceeds 2500 kilograms per cubic meter.

A heavy mixture is prepared with the involvement of dense fillers, which is limestone, diabase or granite, based on crushed stone rocks. Everywhere for construction purposes, standard heavy concrete is produced, having a density of 1600 to 2500 kg / cubic meter. The branding of heavy compounds begins with the designation M100 (and further 150, 200, ..., 600).

Classification of heavy concrete:

• for reinforced concrete prefabricated structures;
• fast curing;
• high strength;
• with fine sand;
• for hydrotechnical purposes;
• and others.

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Parameters of lightweight concrete

Lightweight concrete is made with the addition of porous fillers. These, in particular, include pumice, expanded clay, expanded slag, agloporite, tuff. Lightweight mixtures are considered the basic building material for the construction of enclosing structures and load-bearing structures. In the latter, due to lightweight types of concrete, they achieve a reduction in their severity.

For such types of concrete, along with strength, an important indicator is their density. By density, concrete is divided into:

• especially light - with a density of less than 500 kg / cubic meter;
• light - from 500 to 1800 kg / cubic meter.

Lightweight concrete types:

1. Porous - they prepare it without sand on a large-pore aggregate. Porization is carried out by pre-formed foam or by the use of gas-forming or air-entraining components. Foam is used to porous sand-free mixtures, gas-forming additives - with and without sand, air-entraining substances - exclusively with sand.
2. Coarsely porous. This is a material based on large-pore light fillers (aggloporite, expanded clay gravel, slag pumice, natural fine- and coarse-pore natural aggregates). These mixtures are high rigidity. Therefore, when determining the composition, they monitor the non-separability of the solution.
3. Cellular - a particularly light composition, has a large amount (about 85% of the total mass of concrete material) of small and medium size air cells with dimensions of 1-1.5 mm.

The mechanically created concrete mixture is called foam concrete, and chemically - aerated concrete.

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Types of concrete by binder

The binder used in the material is responsible for both its basic properties and the name.

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Gypsum concrete

The gypsum variety is made with the inclusion of gypsum. Its strength is less than that of cement, because this concrete is successfully used for the construction of indoor partitions, suspended structures ceilings and decorative finishing elements.

A material made of gypsum with the addition of cement and a pozzolanic binder is a gypsum-cement-pozzolanic concrete used for low-rise construction.

Gypsum concrete is distinguished by one significant advantage - environmental friendliness.

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silicate concrete

The silicate mixture is created by heat-moisture action on a mixture of water, inorganic filler and lime-silica binder. silicate material, as well as cement, is widely used for industrial purposes and civil housing construction.

The silicate composition has found its active use in the manufacture of wall ceilings and panels. In addition, it is made flights of stairs, load-bearing parts, columns. He is involved in the laying of road foundations, the production of tubing and railway sleepers.

The silicate material is waterproof and resistant to aggressive environments.

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cement concrete

The cement composition finds the most extensive use in the construction environment. It is made on the basis various brands Portland cement, they determine the existing classification cement compositions. In their production, as a rule, cement M 400 (500) is used.

According to the type and grade of cement used, concretes are distinguished by:

• specialized on aluminous binder;
• decorative with the inclusion of white or colored cement;
• for self-stressed structures.

Concrete mortar is a building material that is used for the construction of monolithic buildings, in road construction, in the production of reinforced concrete structures, etc. A wide range of applications makes a large number of varieties of concrete. They are distinguished by key features: strength, composition, purpose and technical, operational characteristics. This determines the division of the material into classification groups, which we will consider below.

Normative documents

Production building materials The overwhelming majority is regulated by state standards of various types. GOST 25192-2012 defines the classification of concrete according to the main features:

• Appointment;
• Corrosion resistance different types;
• The type of binder used, which determines the basic properties of the material;
• The structure of mortar and stone;
• curing conditions;
• Strength is the main parameter that is taken into account when choosing components for preparing a solution;
• The rate of strength gain;
• Density is average;
• Frost resistance;
• Waterproof;
• Abrasion resistance.

Consider the main features that must be taken into account when choosing concrete for construction.

Strength classification of concrete

Strength is the first indicator that is taken into account when choosing a brand and class of material when drafting a project and calculating it. The stone should normally perceive incoming loads, resistance to them should be in stock, but not in excess - this significantly increases the cost of the construction process, but is not effectively spent.

How is the strength of concrete stone measured:

1. When mixing the solution, take a small amount of the mixture and pour it into a cube shape with a side of 100 mm.
2. After 28 days (the period of full strength development), the sample is sent for testing to the laboratory, where the cube is examined under pressure with different efforts.
3. According to the result, compliance with the brand and class is determined.

The classification of concrete by grades and classes is always interconnected, the values ​​​​correspond to each other (see the table):

Brand - the average value of strength for a material of a given composition. This is a laboratory indicator, in practice, under operating conditions, the product is affected by destructive influences and the strength characteristics of the stone change.

The margin of error in strength virtually eliminates another type of classification, class. This is an accurate indicator permissible error no more than 5%. Modern designers and engineers in project documentation indicate mainly the designation of the class of concrete, sometimes in a paired version: B20 (M250).

It should be noted that not every manufacturer has laboratories, so the supplied concrete solution is mandatory tested by developer companies. It often happens that after the expiration of the curing period (28 days), experts reveal a discrepancy between the class and the specified one, then the structures are subject to dismantling.

GOST regulates an additional division by strength:

• Medium strength concrete (up to B50);
• High strength concrete over B55 inclusive.

Density

The ratio of mass to volume is the next indicator that is taken when choosing a material. Classification by concrete density according to GOST:

• Particularly light (nostrilous) with high porosity. Volume weight- up to 800 kg/m3. These are foam and aerated concrete;
• Lightweight with a density of 800-2000 kg/m3. These are pumice concrete, slag concrete, wood concrete and other materials based on cement binder with light aggregates;
• Heavy concrete or ordinary. Their density is 2000-2500 kg/m3. This is a standard material for the main construction of building structures, monolithic housing construction. Filler - crushed stone, gravel;
• Particularly heavy concretes contain a filler of barite, metals and iron ore. The volumetric weight of such material exceeds 2500 kg/m3. Concrete is used in the construction of specific facilities where protection from radiation of various nature is necessary (laboratories, test sites, nuclear power plants).

Lightweight and extra-lightweight concretes have low density and high porosity, retain heat well indoors. Their use is possible without additional insulation.

Heavy and extra heavy concretes are strong. Their use makes it possible to build objects of high responsibility and number of storeys, of any configuration in different climatic conditions, which cannot be said about porous materials. True, stones on crushed stone and metal filler do not retain heat well - in order to avoid additional thermal insulation, you will have to install a very thick structure, which will require considerable expenses.

Classification by binder type

Astringent is an essential component concrete mortar. The parameters of the future concrete stone depend on its characteristics. GOST 25192-2012 defines the classification of concrete according to the type of binder:

• Cement (Portland cement, slag cement, pozzolanic cement, etc.), used for the preparation of mortars general purpose;
• Slaked lime improves the quality of the mixture, plasticity, resistance to moisture;
• Slag increases the resistance of the material to sulfates;
• Gypsum is introduced into concrete for the preparation of plasters for internal works, for the manufacture of decor items and simple self-supporting structures;
• Special types of binder are polymers of a complex structure that are introduced into the solution in order to acquire the necessary specific qualities for the material.

In practice, binder components are combined to adjust the individual properties of concrete.

Frost resistance

When choosing concrete, it is necessary to take into account the climatic features in which the structure will be operated. For the middle and northern stripes, this is frost resistance (F). It is regulated by plasticizers:

• Low frost resistance less than F50;
• Medium frost resistance (F50…F300);
• High frost resistance (F300 and more).

Waterproof

Water resistance is the ability of a material to maintain its structure without being filled with water. The designation is W, behind it lies the pressure at which liquid penetrates into the hardened stone. As a rule, the higher the density, the higher this figure. State standard divides concrete into 3 groups according to water resistance:

• Low (up to W4);
• Medium (W4-W12);
• High (water resistance grade over W12).

Abrasion

This indicator is important when choosing concrete for pouring floors in rooms with different traffic and moving machines and mechanisms.

• Low (abrasion grade G1);
• Medium (abrasion grade G2);
• High (abrasion grade G3).

Strengthening rate

The rate of strength development can be controlled by additives-plasticizers. Concrete is divided into 2 types on this basis:

• Fast-hardening ones are used if necessary in fast construction, when the erection of overlying structures should be carried out in a few days;
• Slow-hardening concrete is a material without additives, gaining strength in the usual way.

Hardening conditions

For concrete with different composition required certain conditions hardening:

• Natural conditions (temperature 20-22°C, humidity about 50-70%);
• Heat treatment at normal pressure is necessary, for example, when winter construction when maintaining a positive temperature is required;
• Heat treatment at high pressure(autoclave). This is how they create individual structures for construction.

Classification of types of concrete helps to make right choice material, taking into account all the key qualities of the material. We recommend purchasing material with the selected characteristics from specialized manufacturers who provide documentation confirming the quality. Only in this case, all the conditions and subtleties of the recipe will be met, which means that the material will have the qualities laid down in the calculations.

Concrete is a mass that is well compacted and mixed. It is obtained from special material with the addition of water and other ingredients. The first is cement. During the production process, exact proportions should be followed, only then the solution will harden to a stone state and show durability and strength.

To date, there are several varieties of concrete mixtures, which are especially common in construction. Costs for concrete materials quite often exceed 20% of the value of the building. This does not take into account the cost of concrete on the walls. This allows us to conclude that the choice of concrete is an important component of construction.

A significant factor is the processes of preparation and application of the solution. However, first you need to familiarize yourself with the main types and properties of concrete. Before hardening, the mixture of water, sand, gravel and cement has a liquid consistency. Among the main advantages finished construction- resistance to loads, as well as durability. But at ultra-high loads, the material can become cracked. In order to avoid this, the prestressing method should be used.

Its essence lies in the fact that the concrete mass is compressed with tensioned reinforcement. All tensile forces that act on the structure will be taken up by the reinforcement. This allows you to increase the strength of the structure and the building itself, reducing the cost of reinforcement.

Concrete classification

Considering the types of concrete and their classification, you can distinguish several types of this material. Among other factors that allow us to subdivide the composition into individual groups, we should mention the average density. One of the variants of concrete is super heavy, the average density of which is more than 2450 kg/m 3 . In the production process, hematite and magnetite are used. These rocks are ore. They are first ground to scale, shavings or sawdust. The material is used in the construction of nuclear power plants and, if necessary, the protection of premises from radiation.

Another type of heavy concrete is the material of the same name, the density of which reaches 2400 kg / m 3. While the minimum value is 1700 kg/m 3 . This material is the most common type of mixture, because it is suitable for the construction of load-bearing and underground structures, as well as the construction simple walls, foundations and partitions. The main component of the solution is crushed stone from rocks, among them:

• granite;
• diabasite;
• limestone.

Considering the types of lightweight concrete, one should single out the composition of the same name, the density of which reaches 1700 kg / m 3. This mixture may have porous aggregates that are sometimes not even used. Fillers can be artificial or natural. The structure inside has closed pores. Such concretes have good thermal insulation properties and used in private homes.

Among the types of lightweight concrete is an ultra-light material, the density of which does not exceed 450 kg / m 3. Such mixtures are used as heat-insulating cellular material, which has a large number of pores based on light porous aggregates. Such structures are popular for their high thermal insulation and can be used not only for insulating floors, walls and ceilings, but also as a complete structure.

Types of concrete in relation to structure

The modern market for concrete mixes offers solutions that are also classified by structure. Thus, the material can be densified. With the help of such a mixture, it is possible to achieve maximum space filling, while there are practically no free zones, which contributes to hardness and density. This material is made from fine and coarse aggregates, as well as a dense binder.

In construction, porous concrete is also quite actively used, which has an appropriate structure, and is used in the construction of walls and facades. Aerated concrete is a mixture that does not include aggregates. Instead, artificial rocks are added to the ingredients in the form of closed cells that are filled with air. Such a solution is common in the construction of one-story houses.

Concrete is one of the most popular building materials today. The type of concrete that cannot be ignored is superporous. Its structure is formed by large aggregate, which is not supplemented by sandy rocks.

Types of concrete in relation to the binder and the purpose of mixtures

Considering the classes of concrete, it is possible to subdivide the material by internal fillers. Sometimes the solution is made on the basis of cement. Such a mixture may include the following types cements:

• clinker;
• slag Portland cement;
• Portland cement;
• pozzolanic cement.

The resulting mixture is used in the construction of multi-storey buildings. You can not ignore the silicate solutions, which are obtained from limestone. In the production process, autoclaves are used, where the material is subjected to heat treatment, which allows increasing its strength. If you decide to use concrete in construction, you should definitely study the types of concrete.

Among others, it is necessary to highlight gypsum mixtures, which have an impressive ability to absorb water. Such solutions are used in the construction internal walls and installation of ceilings. This material is popular because of its budget. The mixture can also be slag-alkaline. Slag alkali acts as a binder. This solution is resistant to aggressive external factors.

But polymer mixtures are made from components of the same name, in which resins act as the main binder:

• furan;
• polyester;
• epoxy.

It is rational to use compositions on this basis for office or residential buildings. Excellent polymer mixtures have proven themselves in the conditions of factories whose activities are aimed at the chemical production and processing of metals. This is because concrete has highly resistant and wear resistance in relation to thermal conditions.

Special concretes

Special types of concrete are mixtures that are made with the addition of components on water based. Polymers are used as a hardening ingredient. In addition, they are a binder and enhance the fastening of elements in concrete. The mixtures are well resistant to stretching, frost-resistant and water-repellent.

Classification of concrete according to purpose

The concretes described in the article can also be classified according to their intended purpose. Thus, compositions can be structural. They are designed for the construction of load-bearing structures and ceilings. Such solutions perfectly resist power loads. The main advantages are resistance to deformation, strength and the ability to use at low temperatures.

Structural and heat-insulating compounds are solutions that are widely used in outdoor structures, in the construction of facades and fences. The main feature of these concretes is the ability to thermal protection. Considering the main types of concrete, you will pay attention to heat-insulating mixtures. They are used to provide high thermal resistance, so they are used for building envelopes. The material allows you to form a small layer, but it can be used as load-bearing structures.

Thermal insulation concretes can be applied to the surface of conventional concrete structures. Among others, it is necessary to single out hydraulic mixtures that are used to provide high density, frost resistance, water tightness and resistance to aggressive external conditions. These concretes are popular in the northern part of the country, where they are used for the construction of residential buildings.

The article presents the types of concrete and their application. Among others - road concrete mixes, which are used as the top layer of the road and on the runway at the airport. This class of material is characterized by high resistance to cracks and deformations. Under the influence of temperature changes, the structure does not collapse.

Concretes, types, properties and application of which are described in the article, can also be chemically stable. They perfectly tolerate the effects of alkalis, acids and salts. They have unique characteristics and boast high wear resistance, as well as excellent resistance to vapors and chemical compounds. This concrete serves as insulating material, and you can apply it on the finished layer. But chemically resistant compounds cannot be used for load-bearing structures.

Purpose of heat-resistant concrete

Considering concrete, the types and purpose of this material should definitely be studied. Among others - a heat-resistant composition that retains the necessary physical and mechanical properties with prolonged exposure to elevated temperatures. Such compositions are used for production facilities as load-bearing structures, which are subjected to high temperatures during operation.

Appointment of decorative mixtures

Before using concrete in construction, the types of concrete must be studied. Among others - decorative compositions, which are used for texture processing in the process finishing works. Such a mixture can be found on the outer surface of buildings and structures. Concrete structures correspond to the selected texture and color. The material has a high resistance to atmospheric phenomena.

Basic properties of concrete

Among the main indicators that characterize concrete, compressive strength should be highlighted. It defines the material class. For example, the designation B25 indicates that a standard concrete cube of this class will be able to withstand a pressure of 25 MPa.

To determine the strength, coefficients should be taken into account. For the above material, in terms of compressive strength, the standard resistance will be 18.5 MPa, while the design resistance is 14.5 MPa. Along with the classes, the strength of the material is given by grades, which are indicated by the letter M and a number ranging from 50 to 1000. It means the compressive strength in kg / cm². If you decide to use concrete in construction, the types of concrete should definitely be considered. They are further subdivided according to ease of use. On this basis, the material is designated by the letter P and can be divided into concrete:

• hard;
• super hard;
• mobile.

Among the others important indicators need to highlight:

• bending strength;
• frost resistance;
• waterproof.

As for frost resistance, it is indicated by the letter F and numbers from 50 to 1000, which indicate the number of freeze and thaw cycles. But water resistance is indicated by the letter W and numbers from 2 to 20. They indicate the water pressure that a sample in the form of a cylinder will be able to withstand.

Varieties of concrete by grade

In order to get good concrete, you should follow the technology of its manufacture and follow the recommendations on proportions and composition. In many ways, the composition depends on the purpose and responsibility future design. For example, less cement will be used for M100 concrete than for M400 or M500 concrete. Most often, ready-mixed concrete is made from cement of the M400 and M500 grades using sand, crushed stone and various additives. The latter can be antifreeze.

When determining proportions, many factors should be taken into account, among them:

• fraction of sand;
• density;
• frost resistance;
• mobility;
• waterproof.

Considering the types and grades of concrete, one can distinguish the material, which is indicated by the letter M and numbers ranging from 100 to 450. The mass composition for the M100 concrete grade is as follows: 1: 4.6: 7.0. AT this case we are talking about the ratio of cement, sand and gravel. But if it is necessary to prepare the M250 concrete grade, the above components should be combined in proportions: 1: 2.1: 3.9. In order to make concrete grade M400, it is necessary to combine cement, sand and crushed stone in ratios that are equal to 1: 1.2: 2.7. In this case, we are talking about a solution that is made from cement grade M400.

Additionally, it is worth saying about the brands that there are M50-M1000 concretes. The choice of a particular brand will depend on the required strength and area of ​​\u200b\u200buse. In the project documentation, you can find the brand of the solution. If there is none, then you should trust the builders or make a choice yourself. Some believe that the brand of concrete depends on the brand of cement. However, the first is assigned taking into account the proportions used.

Conclusion

Concrete, the types and properties of which were described above, is presented today in a wide variety. Therefore, builders should think about which mixture to choose. You should not make a rash purchase. It is important to determine the goals that you are pursuing and the loads that concrete structures will withstand.

It is important to pay attention to the indicators of deformation and strength. If these aspects are taken into account, then choosing a concrete mixture will be quite simple. For example, if you want to make a structure with high water resistance, then you should purchase or prepare a hydraulic solution. Buildings are being erected from it, which will be operated in marshy areas.

Concrete- this is one of the basic building materials, without which it is impossible to do on any construction site. Based on it, f foundations, ceilings, lintels and many other designs. They are valued for their strength and durability. But for production different designs different types of concrete will be required. For example, in different situations it will be necessary different strength, moisture resistance level and other indicators. That is why today the production of various types is practiced. concrete.

Classification and properties of concrete

The use of various ratios of the components that make up concrete, as well as the addition of various additives to concrete and the use of various binders, allows you to get a concrete mixture suitable for certain requirements, set by the customer of the concrete mix.

At a concrete plant, this is done by specially trained people, technologists who control the quality of the produced concrete mixture and, if necessary, change its composition so that the concrete mixture meets all standards and requirements under various external conditions. They can regulate the most important characteristics concrete mixture, such as: concrete frost resistance, concrete density, concrete water resistance, concrete grade and many others.

In this article we will tell you on what principles the classification of concrete is carried out and what it depends on.

To date, there are several principles for classifying concrete:

1. By function

The type of concrete mixture primarily depends on the future purpose and type of operation of the concrete structure being erected. Depending on the requirements, the necessary concrete mixtures are used. Usually deals with issues related to various extreme conditions operation of concrete products, for example, increased resistance to sulfate, as well as fire resistance, or resistance to vibrations, etc. may be required.

Thus, this indicator distinguishes general purpose concrete and concrete special purpose , and it also happens hydrotechnical concrete and special concrete used for construction airfields.

• General purpose concrete used for the construction of foundations, floor slabs, various beams and various columns, and other reinforced concrete structures.
• Special purpose concrete used in the construction of: bridges, roads and other structures, during the use of which the material will be subjected to special conditions of use, for example, such special concrete is used in the construction of buildings nuclear power plants, to prevent radiation leaks, there is also concrete resistant to fire and various acids.
• Hydrotechnical concrete used in the construction of dams, hydroelectric power plants, water-pressure structures.

Concrete strength- this is also one of the most important technical characteristics of concrete, which, in principle, does not depend on the classification of concrete. The strength of concrete depends on the amount of binder added and the type of aggregate used. The more cement is added to the concrete mixture, the higher the grade (class) of the concrete mixture is obtained. The stronger the aggregate, the stronger the concrete will be.

2. By type of binder

Type of binder. The type of binder directly affects both strength and other consumer properties.

The type of binder is very important in determining the various qualities and properties of concrete. On this basis, silicate, gypsum, slag-alkali, cement, polymer concrete and other special purposes are distinguished.

Combination is also used, usually no more than 2-3 binders are mixed. This combination allows some special properties of the concrete mixture, which may sometimes be needed, for example, for the manufacture of various dry plaster mixtures.

But let's look at each concrete in order:

Silicate concrete - made with the addition of lime. Hardening and curing of such concrete is carried out by autoclave. It should be noted that this silicate concrete is used quite rarely.

Gypsum concrete - this concrete is produced, as the name suggests, based on gypsum. This type of concrete has found wide application in the construction of internal interior partitions, is used in the construction of suspended ceilings, etc.

Slag-alkaline concrete - made from milled slag, by mixing with alkaline solutions. Recently given type concrete, began to be used in construction.

cement concrete- the most widespread and well-known type of concrete. Cement concrete is produced from cement. Portland cement is the most popular cement used in the production of cement concrete, pozzolanic Portland cement and Portland slag cement are also used. This also includes different kinds decorative colored cements, various types of non-shrinking and tension cements.

Polymer concrete - produced in a mixed binding basis, from the following components: cement, latex and special resins.

Special concrete- Produced using special binders. If refractory and acid-resistant concrete is required, then a component such as liquid glass, and glass-alkali, nepheline and slag components are selected from binders.

3. Classification of concrete by density

Classification of concrete by strength (density). The density (strength) of concrete primarily depends on the type of aggregate. The filler can be porous, dense, as well as for special purposes. Also, aggregates may differ by fraction. They also significantly affect the basic properties of the final product. The following types are most often used: gravel, granite, expanded clay, diabase, limestone. It is the density that determines the compressive strength, water resistance and frost resistance.

Classification of aggregates for concrete and types of concrete by density:

Lightweight concrete- the density of which is from 500 kg/m3 to 1800 kg/m3. Such lightweight concretes are used as aggregates of expanded clay (expanded concrete), pumice and other aggregates with a porous structure. Cellular concrete, such as aerated concrete and foam concrete, also belong to the category of lightweight concrete.

heavy concrete— density from 1800 kg/m3 to 2500 kg/m3. In such heavy concrete aggregates from a stone of rocks are used: granite and diabase.

Extra heavy concrete- whose density is more than 2500 kg / m3, metal shavings or iron ore are used as a filler.

4. According to the structure of concrete

The structure distinguishes a lot of types of concrete, as we wrote above. The most popular among them are dense, cellular, large-pore.

5. According to the conditions of solidification

Concrete is distinguished according to the conditions of hardening. According to this indicator, concretes are distinguished that harden naturally and during special conditions(for example, under conditions high blood pressure or high temperature).

Thus, to date, an extremely wide variety of types of concrete has been developed. GOST classification of concrete which can be used for different purposes and for different building objects. To properly navigate in such a wide variety, you need to seek help from a qualified specialist.

Types of concrete and their classification

Concrete - it's artificial stone material, obtained as a result of the hardening of a mixture of binder, water, aggregates and special additives (in a certain proportion), thoroughly mixed and compacted.

Before hardening, this mixture is called concrete mix .

One of the main properties of concrete is high resistance to compressive loads and low tensile loads: Rcom is 10-12 times higher than Rgrowth.

To improve tensile strength in concrete structures reinforcement is laid, which mainly perceives tensile forces. Reinforced concrete is called reinforced concrete - it resists both compression and stretching well.

Widely used in construction practice prestressed concrete . The essence of prestressing is that the concrete zone subject to tension is compressed by tensioned reinforcement. As a result, tensile forces are absorbed by the reinforcement, reducing the compressive stress in the concrete. This technique ensures high crack resistance of concrete. Prestressed reinforced concrete structures compared to conventional reinforced concrete, it is more economical, because as a result effective use high-strength materials (steel and concrete), the consumption of reinforcing steel is reduced.

Concrete is classified according to a number of criteria.

A.) By medium density concretes are divided into:

Particularly heavy more than 2500 kg / m 3;

Heavy 1800 - 2500 kg / m 3;

Light 500 - 1800 kg / m 3;

Particularly light less than 500 kg/m 3 .

For cooking especially heavy concrete, heavy aggregates from stone ore-bearing rocks (magnetite, hematite) are used; in the form of steel filings or shavings, iron shot, scale, etc. Such concretes are used for radiation protection during construction. nuclear power plants, as grouting concrete for filling workings.

heavy concrete received the greatest application in the practice of construction for the construction of underground and above-ground load-bearing structures and structures (foundations, walls, columns, beams, trusses, floor and ceiling slabs, etc.). Crushed stone of dense rocks (granite, limestone, diabase, etc.) is used as a large aggregate for such concrete.

To the group lungs includes concretes on porous aggregates of natural or artificial origin, as well as cellular concretes (without aggregates) with a significant number of artificially created closed pores in the concrete body. This also includes concrete on porous aggregates in combination with porous cement stone. They are used as heat-insulating and structural material.

Extra light (thermal insulation) - this is mainly cellular concrete with a high degree of porosity (sandless) and on light porous aggregates. Such concretes have low thermal conductivity and are used as an effective heat-insulating material.

B.) By structure concretes come with a dense, porous, cellular and large-pore structure.

dense structure - when the ratio of components is selected so that there is no free space left in the concrete body (the method of absolute volumes). Concrete consists of coarse and fine aggregate (or only fine aggregate) and dense cement stone (or other hardened binder) between aggregate particles.

porous - when the space between the grains of inert components (large and small or one of them) is filled with a binder that has hardened in a porous state.

Cellular - without aggregates, with a significant amount of artificially created pores in the body of concrete in the form of closed cells filled with air.

Large porous concrete - with only one large aggregate, without sand at all (sandless) or with a very small content of it.

B.) By type of binder concretes are distinguished: cement, silicate, gypsum, slag-alkali, polymer concrete, polymer cement and special concretes.

Cement - concretes on clinker cements, mainly on Portland cement and its varieties, Portland slag cement and pozzolanic cement.

silicate concretes are obtained on a lime binder. To ensure the hardening process of such concretes, autoclaves are used, where the concrete is subjected to heat treatment under pressure.

Gypsum concretes have low water resistance, therefore, structures inside the building are made from them ( dropped ceilings, partitions).

Slag-alkaline concretes (binder - ground slags and alkaline solutions) have high strength and resistance to aggressive environments.

Polymer concretes (binder - epoxy, polyester, furan and other resins) highly resistant to aggressive environments, used in the construction of structures for the copper-smelting and chemical industries, enterprises for processing agricultural products (sugar and breweries), tanks for storing acids, mineral waters, etc.

Polymer cement concretes are produced with the addition of aqueous dispersions of various polymers, which are added to the mixture together with mixing water. The polymers are deposited in the form of a film on the surface of the aggregate, increasing the adhesion between the elements of the concrete structure. Such concretes resist stretching well, have increased frost resistance, water resistance and chemical resistance.

D.) By scope and for the respective purposes technical specifications the following types of concrete are distinguished.

Structural - general purpose, used in structures that perceive external force effects (loads). The defining properties of such concretes are strength and deformation characteristics, as well as frost resistance when structures operate under conditions of sign-variable temperatures. These are foundations, columns, beam structures, roofing and floor slabs, etc.

Structural and heat-insulating - are used in enclosing structures (external walls, coatings). Such concretes should provide not only bearing capacity structures, but also their heat-shielding properties.

Thermal insulation - their purpose is to provide the necessary thermal resistance enclosing structures with a relatively small layer thickness, while the bearing capacity of structures provides ordinary concrete(in two- and three-layer constructions).

Hydraulic , which, along with the necessary strength and deformation characteristics, must have increased density, water resistance, frost resistance, as well as resistance to aggressive effects environment- water.

Road - for the top coverings of roads, runways of airfields. They must have increased strength, high wear resistance, well resist the alternating effects of temperature and moisture.

Chemical resistant – salt-, acid- and alkali-resistant. Along with the necessary indicators technical properties should have the ability to long period withstand without destruction and deterioration operational qualities exposure to concentrated solutions of salts, acids and alkalis and their vapors. Such concretes are used as the main material of structures, or for protective coatings conventional concrete structures.

Heat resistant - retaining their physical and mechanical properties within the specified limits during prolonged exposure high temperatures. Apply to industrial units and building structures subjected to high temperatures during operation.

Decorative – for finishing layers with textured processing on the front surfaces building products. Such concretes (mortars) must meet the requirements in terms of color, texture, and have a sufficiently high weather resistance.

The types of concrete considered above, despite significant differences in certain properties and their indicators, are subject to general patterns, which follow from the general principles of the formation of their structure and structure.

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