The compressive strength of concrete is traditionally considered one of the main indicators characterizing the properties of concrete. This parameter is expressed in two concepts - the class and grade of concrete, which are taken into account when choosing a mixture for the implementation of certain works, are the main technical characteristics, and are extremely important for guaranteeing the ability of the hardened monolith to withstand certain loads, which affects strength, reliability, and durability.
A certain class of concrete in terms of compressive strength is marked with the letter B and a certain number; it demonstrates the so-called cubic strength (when a cube-shaped sample is compressed under a press and the mark at which it collapses is recorded). The pressure is calculated in MPa, which assumes the probability of destruction at the specified indicator is a maximum of 5 units out of 100 subjects. Regulated by SNiP 2.03.01-84.
The strength of concrete (MPa) can be different - classes are differentiated within the range of 3.5-80 (there are 21 types in total). About a dozen mixtures with classes B15 and B20, B25 and B39, B40 became the most popular. Any class is equated to its corresponding brand (in a similar way, the rule works the other way around). The strength of concrete in MPa (class) is most often indicated in the design documentation, but suppliers sell mixtures indicating the grade.
The grade of concrete is indicated by the letter M and a digital index in the range of 50-1000. Regulated by GOST 26633-91, corresponds to certain classes, a strength deviation of a maximum of 13.5% is considered acceptable. For a brand of concrete, the main requirements are the volume/quality of cement in the composition. In turn, the brand is indicated in kgf/cm2; determination of the brand is possible after the mixture has completely hardened and hardened (that is, at least 28 days after pouring).
The higher the number in the class and brand indices, the more durable the concrete will be and the higher its cost (both when purchasing a ready-made mortar, and when mixing it yourself due to the larger volume of cement and its higher grade).
Taking into account the above facts, the main task of the master is to determine the ideal characteristics for the solution, taking into account the scope of use and expected loads. After all, preparing concrete that is too strong will lead to unjustified costs, while preparing concrete that is not strong enough will lead to the destruction of the structure. Typically, the average strength of concrete for certain works or structures is indicated in GOSTs, SNiPs - these values are taken as a guide.
Types of material according to compressive strength:
- Thermal insulation mixtures – from B0.5 to B2.
- Structural thermal insulation mortar – from B2.5 to B10.
- Structural mixtures – from B12.5 to B40.
- Special concretes for reinforced structures – above B45.
Concrete grades table
Before building a private house or outbuilding for domestic purposes, you need to select the appropriate solution parameters that meet the stated requirements. The determining and main parameter in this case is the grade of concrete, which reflects the quality of the building material, strength, frost resistance and water permeability. All grades of concrete, the table with values given below, are proportionally mixed bulk materials with certain properties and characteristics, mixed with water. Once the solution is poured into the mold, it compacts, forms and hardens. Until the mixture begins to harden, it is called a solution. Special building mixtures are prepared without mixing with water.
Principle of concrete preparation
How to determine class and brand
Concrete products and structures are used almost everywhere:
- During the construction of structural objects, structures and buildings;
- During the construction of monolithic structures.
It is necessary to establish the required brand at the beginning of the design of the facility. Almost every significant element or detail of a structure is assigned standard values within the brand and class after the necessary calculations. Construction objects can be any concrete structures - foundations and substrates, floor slabs, walls (load-bearing or not), columns and arches, pile structures and foundations, floors and ceilings.
Strength growth chart
In addition to the classifications by classes and brands common in industrial and individual construction, special light and heavy materials with specific parameters and properties have been developed and are widely used:
- Low coefficient of sedimentation and mobility of the solution;
- Frost resistance;
- Duration of operation;
- Immunity to cracks and chips;
- High fire safety;
- Protection of humans from the negative effects of penetrating radiation, etc.
Varieties and classification
The main classes of concrete are established based on the binder:
- Cement concrete is the most popular and widespread;
- Asphalt concrete – for road construction;
- Lime building material;
- Gypsum concrete;
- Silica concrete;
- Clay concrete and other types of building materials.
Types of concrete by type of binder
How to classify concrete by aggregates:
- Ordinary building material or heavy, with a density ≥ 1700 Pa. Crushed stone or gravel dense aggregates from rocks are added to the solution. Heavy concrete is used in the construction of reinforced concrete or concrete structures with high operational strength;
- Extra heavy, with a density ≥ 26500 Pa. Barite and materials with iron impurities are added to the solution to minimize the harmful effects of radiation on the human body when working at nuclear power plants, in research and testing laboratories;
- Brands of lightweight concrete with a density ≤ 1700 Pa - consist of wood concrete, blast furnace or ash slag, pumice, etc. Porous building materials with low thermal conductivity are needed in the construction of internal partitions and unloaded coverings or fences;
- Particularly lightweight material - spongy foam and aerated concrete with a density of ≤ 5000 Pa.
Concrete by type of aggregate
How to classify concrete by inclusions of reinforcing elements:
- Reinforced concrete is a material with steel reinforcement;
- Concrete reinforced with non-stressed reinforcement;
- Concrete reinforced with prestressed reinforcement;
- Wood concrete;
- Reed concrete;
- Material with artificial reinforced fiber;
- Concrete reinforced with fiber reinforcement (dispersed reinforcement method), etc.
Types of concrete by type of reinforcement
Types of concrete by viscosity state:
- Rigid composition designed for monolithic powerful structures;
- Plastic concrete for structures with thin load-bearing walls and floors and densely laid reinforcement.
Material properties:
- Concrete is waterproof - it is not saturated with moisture when exposed to water pressure ≥ 0.2 MPa. Designed for mines, used in hydraulic engineering and road construction;
- Frost-resistant concrete, designed for an increased number of freeze-thaw cycles compared to conventional material;
- Concrete has particularly high fire resistance, withstanding high temperatures longer than conventional material.
Classification by concreting method:
- Shot concrete, for the production (not preparation) of which a special cement gun is used. Torquetting is the spraying of a cementitious solution under high pressure in several layers.
Torquet concrete
Brands - classification by strength
Performance quality is determined by its brand, which depends on the following parameters:
- The quality of the binder in the solution;
- W/C ratio (water - cement). If the W/C parameter increases, the strength of concrete decreases. The accepted average value of W/C is 0.3-0.5;
- Density of aggregates and final density of concrete.
Each grade of concrete has an actual strength corresponding to the arithmetic average of the minimum and maximum compressive strength of a 28-day-old concrete cube from each batch. The sample is taken with sides of 20 cm.
Concrete samples in cubes
How concrete is divided into regular and lightweight concrete according to grades:
- Ordinary concrete: grades M 25 - M 600;
- Lightweight and durable building materials: M 10 - M
This table of concrete grades will be useful for matching the grade and class:
| Concrete class | Material grade |
| V 3.5 | M 50 |
| AT 5 | M 75 |
| B 7.5 | M 100 |
| AT 10 | M 150 |
| At 12.5 | M 150 |
| At 15 | M 200 |
| IN 20 | M 250 |
| At 22.5 | M 300 |
| At 25 | M 350 |
| At 27.5 | M 350 |
| At 30 | M 400 |
| At 35 | M 450 |
| At 40 | M 550 |
| At 45 | M 600 |
| At 50 | M 700 |
| At 55 | M 750 |
| At 60 | M 800 |
| At 65 | M 900 |
| At 70 | M 900 |
| At 75 | M 1000 |
| At 80 | M 1000 |
Classification is carried out according to workability and rigidity:
| Workability of the mortar Ultra-hard, rigid and flexible mixtures | Mixture hardness | Cone draft |
| SJ 3 | ≥ 100 | — |
| SJ 2 | 51-100 | — |
| SJ 1 | ≤ 50 | — |
| F 4 | 31-60 | — |
| F 3 | 21-30 | — |
| F 2 | 11-20 | — |
| F 1 | 5-10 | — |
| P 1 | ≤ 4 | 1-4 |
| P 2 | — | 5-9 |
| P 3 | — | 10-15 |
| P 4 | — | 16-20 |
| P 5 | — | ≥ 21 |
Branded frost resistance
The ability of water-saturated concrete to withstand freeze-thaw cycles for a long time without destruction or reduction in strength parameters is called frost resistance. Frozen water, turning into ice, expands and penetrates the air pores of concrete, destroying it. Therefore, frost resistance indicators depend on the structure of the concrete: the larger the pore size, the lower the frost resistance of the building material.
Frost resistance of concrete
Frost resistance as a technical and operational parameter is especially important for northern climate zones. In northern conditions, almost all concrete structures are operated at low outdoor temperatures, absorbing atmospheric moisture and undergoing repeated freezing and thawing. Concrete objects made from conventional building materials lose their strength after some time. The main reason for the accelerated wear and destruction of concrete objects is low frost resistance and discrepancies in the requirements of frost resistance standards.
Classification by frost resistance
Concrete prepared in compliance with all standards, regulations and requirements can be used without damage for more than a hundred years. If frost resistance indicators are not met, then damage may appear after just a few years of operation. Mandatory requirements for compliance with the recipe for preparing frost-resistant mixtures, in addition to the water-cement ratio, the type of cement used and setting conditions, include providing the recipe with special air-entraining additives and other additional conditions for maintaining frost resistance.
Frost resistance is indicated by the Latin symbol “F” and numbers in the range of 50-1000, indicating the number of freezing and thawing cycles that will not lead to the destruction of the characteristics of the material.
Strength tests
In the table you can see how the grade of a specific concrete sample is determined according to the freeze-thaw cycles that will be carried out using the above methods:
- Method I: any concrete, except for that used for the construction of road surfaces and airfields;
- Method II: except for those used for the construction of road surfaces and airfields, as well as lightweight concrete of medium density ≤ D1500;
- III method: for concrete used in the construction of road surfaces and airfields.
| Brand Definition | F-35 | F-50 | F-75 | F-100 | F-150 | F-200 |
| I method | 2,5:3,5 | 3,5:5 | 5:7,5 | 7,5:10 | 10:15 | 15:20 |
| II | — | -:8 | -:13 | -:20 | 20:30 | 30:45 |
| II | — | — | 2 | 3 | 4 | 5 |
| III | — | 35:50 | 50:775 | 75:100 | 100:150 | 150:200 |
| III | — | — | — | 5 | 10 | 20 |
| Determination of strength | F-300 | F-400 | F-500 | F-600 | F-800 | -1000 |
| I method | 2:3 | 3:4 | 4:5 | 5:6 | 6:8 | 8:10 |
| II | 45:75 | 75:110 | 110:150 | 150:200 | 200:300 | 300:450 |
| II | 8 | 12 | 15 | 19 | 27 | 35 |
| III | 2:3 | 3:4 | 4:5 | 5:6 | 6:8 | 8:10 |
| III | 37 | 55 | 80 | 105 | 155 | 205 |
Water permeability is the ability of a material to resist moisture during cyclic wetting and drying. Water permeability is calculated by the ratio of the ultimate strength after a certain number of cycles of wetting and drying, and the initial strength value. The water permeability grade is designated by the letter “W” of the Latin alphabet and numbers from two to twenty, which indicate the maximum water pressure.
Concrete waterproofing control
The process of preparing high-quality concrete requires strict adherence to the quantity of ingredients in the solution, which serves as the key to the strength and long-term operation of structures. Concrete of commercial quality with specified characteristics is in demand in industrial and private construction due to its effective use in monolithic structures. The qualities inherent in concrete - seismic resistance, high strength, seamless construction, uniform shrinkage of the mixture and low cost are increasingly attracting consumers.
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Flexural strength
This indicator increases with the growth of the brand's numerical index. Tensile and bending values are much less than the load capacity of concrete. For young concrete this ratio is about 1/20, for older concrete it is 1/8. Flexural strength is taken into account at the design stages of construction.
It is determined in the following way. Concrete is poured in the form of a beam with dimensions, for example, 120x15x15 cm. After final hardening, it is placed on supports located at a distance of 1 m, and a load is placed in the center, which is gradually increased until the sample is destroyed. The size of the beam being tested and the distance between supports may vary.
Read also: K3525a description operating principle switching diagram
The bending strength indicator is calculated by the formula:
where L is the distance of the supports (1 m in our case); P – load weight + sample weight, N; b, h – width and height of the beam section (0.15 m). This strength is indicated by Btb and a number from 0.4 to 8.
Marking and characteristics of concrete
Primary indicators - brand and class of concrete - are one of the fundamental characteristics when choosing a mortar. The use of different marks varies depending on a range of encrypted values in an alphanumeric format. The finished mixture is usually ordered by brand - the main characteristic is the strength of the future monolith.
1. In the design documentation, the grade is indicated by the capital letter M and the indicator of the ultimate strength of concrete in kgf/cm2. There are grades of concrete from M50 to M1000, but use is most often limited to M100-M450.
2. Concrete class, letter B (B 3.5 – B 60). It implies a guaranteed strength value, that is, a load in megapascals that the monolith must withstand in 95% of cases. In operation, the most common classes are B 7.5 – 35.
3. Indicators of frost resistance, water resistance, mobility, and rigidity are inferior to the above, but are also important in a number of specific cases.
The frost resistance of concrete is indicated by the letter F (25 - 1000), which means the number of freezing and defrosting cycles during which the mixture does not deform. This indicator is extremely important for foundations in very wet soils, bridge structures where there is constant contact with moisture, especially in autumn and spring during periods of temperature changes.
Various manufacturers additionally introduce antifreeze additives into the composition to increase the material’s resistance to temperature changes. Typically, such an additive is a hydrophobic (stressing) cement. Important: abuse of such means will result in a loss of concrete strength. For our climate zone, the use of concrete with frost resistance F 100-200 is suitable.
Water resistance is a characteristic of a concrete mixture based on the bond strength within the material. The importance lies in the fact that water, penetrating into microcracks, destroys it from the inside when it freezes.
Water resistance is indicated by the sign W from 2 to 20 - this is a numerical indicator of resistance to the penetration of moisture into the thickness under pressure. To achieve the required hydraulic resistance characteristics, the same hydrophobic cement or other sealing and hydrophobic additives are used.
It is worth noting that the price will be much higher, but a number of positive qualities will appear:
- the opportunity to save on waterproofing foundations in areas with close groundwater;
- extension of service life due to increased frost resistance, in relation to unprotected structures, such as fences, blind areas, concrete paths.
The table shows the main characteristics of concrete grades, including the consumption of materials for preparing the solution and the approximate cost.
| Brand | Class | Frost resistance | Waterproofness | Proportions: cement-crushed stone-sand-water, part. | Price per m3, rubles | |
| Cement grade M400 | M500 | |||||
| M 100 | B 7.5 | F 50 | W 2 | 1:4,6:7:0,5 | 1:5,8:8,1:0,5 | 3 500 |
| M 150 | At 12.5 | F 50 | W 2 | 1:3,5:5,7:0,5 | 1:4,5:6,6:0,5 | 3 600 |
| M 200 | At 15 | F 100 | W 4 | 1:2,8:4,8:0,5 | 1:3,5:5,6:0,5 | 3 800 |
| M 250 | IN 20 | F 100 | W 4 | 1:2,1:3,9:0,5 | 1:2,6:4,5:0,5 | 3 900 |
| M 300 | At 22.5 | F 200 | W 6 | 1:1,9:3,7:0,5 | 1:2,4:4,3:0,5 | 4 000 |
| M 350 | At 25 | F 200 | W 8 | 1:1,5:3,1:0,5 | 1:1,9:3,8:0,5 | 4 100 |
| M 400 | At 30 | F 300 | W 10 | 1:1,2:2,7:0,5 | 1:1,6:3,2:0,5 | 4 450 |
| M 450 | At 35 | F 300 | W 14 | 1:1,1:2,5:0,5 | 1:1,4:2,9:0,5 | 4 700 |
| M 500 | At 40 | F 400 | W 16 | 1:1:2:0,5 | 1:1,2:2,3:0,5 | 4 800 |
The grade of fluidity of the composition, otherwise called workability or cone slump, is indicated in the mixture passport with the letter P, this index is from 1 to 5. It is a temporary characteristic, since it appears only during the drying period of the solution. It is expressed in the ability of the concrete mass to uniformly fill the proposed form under the influence of the gravity of its own mass.
For standard monolithic work, it is advisable to use grades P2 - P3. When pouring narrow forms, formwork or pillars, reinforced structures where pouring is difficult to access, it is recommended to use P4 or more - this mixture allows you to do without vibration.
Hardness – F – coefficient from 1 to 4. Typically, rigid concrete means “lean concrete” with a reduced percentage of cement and water. This composition is produced in relation to mortar for highways.
Features of application
Differences in the percentage of the components of the solution give rise to differences in the properties and characteristics necessary for one type of work or another. Thus, the use of concrete depending on the brand is expressed in the table.
| Brand | Scope of application |
| M 100 | The so-called “skinny concrete”. It is used in the form of preparation in the construction of roads, for the installation of curbs, in the field of preparation, in anticipation of pouring the foundation and reinforcement. |
| M 150 | A type of lightweight concrete for auxiliary needs in construction, production of floor screed, laying paths. Allowed as a foundation for low-weight structures. |
| M 200 | A fairly common brand due to its increased stability. Suitable for most types of foundations, blind areas, arrangement of platforms, pedestrian paths, construction of concrete flights of stairs, retaining walls, leveling floor screeds. |
| M 250 | Used for various types of foundations, when equipping blind areas, pouring platforms, concrete stairs. They are also used as bases for fences and tiled floors with light loads. |
| M 300 | A fairly popular composition is a practical sales leader. It is used for pouring foundations of any degree of complexity, making walls, ceilings, fences, producing concrete platforms, constructing concrete stairs, blind areas. |
| M 350 | The brand has decent water resistance, so it is suitable for making swimming pool bowls. It is used under extreme loads - when equipping foundations for multi-storey buildings, manufacturing monolithic walls, supports and other load-bearing systems. The main material for the production of reinforced concrete products, airfield slabs, pile-grillage reinforced concrete structures, crossbars, tiled floors. |
| M 400 | A characteristic feature is relatively fast setting and high price. Due to these characteristics, it is rarely used in home construction. Most often it is part of the structures of bridges, various kinds of hydraulic structures, and reinforced concrete products for special purposes. Indispensable for public facilities with special safety requirements - water parks, shopping centers, indoor swimming pools, and so on. |
| M 450 | In private construction, the use of this brand is inappropriate. The application is associated with the production of specialized reinforced concrete structural elements, the requirements for which are regulated by design documentation. Necessary for the construction of platinums, bank vaults, bridges, subways, and dams. |
| M 500 | This brand is used in the design of hydraulic structures, subways, construction of bank vaults and other structures. Not used for domestic purposes. |
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Brickwork installation - optimal temperature range
In order for the finished masonry to be of high quality, it is recommended to carry out work at an air humidity of no higher than 75%, and the temperature can vary in the range of 10 - 25 0 C.
Warm and dry weather improves the adhesion of the mortar to the brick, which has a positive effect on the quality of the finished masonry, and also contributes to the durability and strength of the finished structure. Of course, even if work is carried out exclusively in the warm season, the presented optimal combination of parameters will not always be observed. Deviations in both humidity and temperature are quite acceptable. If they make up no more than 10%, then this will not have a fundamental impact on the quality characteristics of the finished structure.
However, as the ambient temperature approaches zero, it is necessary to reconsider the approach to organizing masonry work.
Concrete mortar and its characteristics
Since ancient times, concrete has been the main binding material for various structures. Recipes for its preparation were kept and passed down from generation to generation until they reached a more modern society. Today, experts can classify the solution. This means that there are more and more such recipes.
Scheme for determining the plasticity of a solution.
Primary and secondary parameters
Today, you can increasingly see its use in private construction. If we are talking about large volumes, then you will need to have special tools for preparation. As a rule, they are not available, so ready-made concrete is purchased from the manufacturer. Solutions have a number of parameters that are worth paying attention to.
The main ones are the following:
- brand and class;
- frost resistance;
- mobility;
- waterproof.
Brand and class are, perhaps, those indicators that must be taken into account without fail. It is with their help that the scope of application of this solution is determined. If we talk about all the other parameters, then they can safely be called secondary. For example, the mobility of concrete can be changed independently, and the desired level of water resistance of a concrete structure can be achieved using special materials.
It is also worth noting that its strength, that is, the design, or as it is often called, the design strength of the structure, depends on the brand and class.
Scheme for determining the mobility of a concrete mixture.
It would not be amiss to note the fact that the strength is constantly changing throughout the entire period of its operation. In the freshly prepared state, the strength is practically zero. However, after about 3 days, this figure approaches 70% of its estimated value. After another 3 weeks the indicator becomes 100%. However, it doesn’t end there, since we are talking only about the calculated strength, and not about the real one. After the first few years, the strength of the structure constantly increases.
This process lasts until the reverse begins, i.e. destruction.
As for the class and brand, we can say that today there are quite a lot of them, as well as areas of application.
The range of brands starts from M50 and ends with M1000. The most commonly used are all brands that lie in the range from M100 to M500. Each subsequent brand is 50 units higher than the previous one, that is, M50, M100, M150 and so on.
The range of classes starts from B3.5 and ends at B80. The most commonly used classes are in the range from B7.5 to B40. The following classes of concrete are distinguished: B7.5, B10, B12.5, B15, B20, B22.5, B25 and so on.
Physical meaning of class and brand
Scheme of processes during concrete hardening.
As already mentioned, the choice of one class or another brand depends on the specific task facing the builder. However, it is worth noting that the brand numbers indicate the average value of compressive strength, that is, the ability to withstand any load. This load is measured in force pressure per unit area - kgf/sq.cm.
This indicator is checked using a special press. A cube is placed under it, which gained its strength for 28 days under normal temperature conditions.
It is worth mentioning separately that each brand of concrete has its own class. In a general sense, we can say that these two concepts are identical. However, their physical meaning is slightly different. If we talk about a brand, we mean the average value of its strength, then when we talk about a class, we mean its guaranteed strength.
There are such concepts as coefficients of variation and others like that, which are taken into account by specialists when performing calculations. For private construction, such complex calculations are useless. The only thing you should pay attention to is the desired class indicated in the design documentation.
Transfer strength
This value is a standardized indicator of the strength of concrete of stressed elements during the transfer of tension from reinforcing parts to it. Transfer strength is provided for by regulatory documents and technical conditions for a specific type of product.
In most cases, it is assigned to at least 70% of the design grade and depends on the properties of the reinforcement. The recommended value of this indicator is at least 15 or 20 MPa for various types of reinforcement. In short, this is an indicator indicating the level when the reinforcing rods do not slip when removed from the conductors.
Artificially increasing the rate of hardening
The hardening time of cement mortar in cold weather increases greatly, but the time frame still remains limited. To speed up the procedure, various techniques have been developed.
BITUMAST Anti-frost additive for concrete
In modern construction, drying time can be accelerated by:
- adding additives;
- electric heating;
- increasing the required proportions of cement.
Using Modifiers
The easiest way to complete work on time even in winter is to use modifiers. When a certain proportion is added, the hydration period is reduced; when using some additives, hardening occurs even at -30°C.
Conventionally, additives that affect the rate of hardening are divided into several groups:
- type C – drying accelerators;
- type E – water-substituting additives with accelerated hardening.
The foundation hardening calculator and reviews show maximum effectiveness when potassium chloride is added to the solution. The material is consumed economically, since its mass fraction is up to 2%.
If you use type C concrete curing mixtures, you should take care of heating, since they do not protect against freezing.
Plasticizers and additives for concrete
It is recommended to take care of laying communications in the foundation or screed in advance, otherwise drilling holes will be required. Making communication holes after hardening will require a special tool and grinding of the concrete surface. The procedure is quite labor-intensive and reduces the strength of the structure.
Concrete heating
Mostly, a special cable is used to heat the composition, which converts electric current into heat. The technique provides the most natural way of hardening. An important factor is the need to follow the instructions for installing the wire. The method protects against liquid crystallization; there are also tools (hair dryer, welding machine) and thermal insulation to protect against freezing.
Increasing cement dosage
Increasing the cement concentration is used only with a slight decrease in temperature. It is important to increase the dosage in small quantities, otherwise the quality and durability will be significantly reduced.
Concreting in dry, hot climates
Concrete does not like not only frost, but also heat. When the air temperature rises to +35 and above, and the humidity is at 50%, water evaporates too quickly, which provokes a violation of the water-cement balance. Hydration slows down or stops altogether, and therefore the concrete must be protected from too rapid loss of moisture.
To lower the temperature of the mixture, use chilled (or diluted with ice) water. This prevents rapid evaporation of water during the laying of the mixture. After a certain time, the mixture heats up, so it is important to ensure the tightness of the formwork (so that water does not evaporate through the cracks). Formwork can also absorb moisture, and therefore, to limit the adhesion of concrete and structural material, it is treated with special compounds before pouring.
Hardening concrete is protected from direct ultraviolet rays - the surface is covered with tarpaulin (burlap), and the surface is wetted every 3-4 hours. Moisturizing may be necessary during the entire 28 days of the monolith gaining strength.
The following method is often used to protect concrete from heat: an airtight cap made of PVC film with a thickness of at least 0.2 millimeters is created above the surface.
Concrete prepared according to the recipe is able to set, harden and acquire all design characteristics at an ambient temperature of +20 degrees and a humidity of about 100%. If work is carried out in frost or heat, it is necessary to take care of heating or cooling measures that will guarantee the strength and durability of the finished structure.
