- Concrete brand
- Concrete class
- Concrete water resistance
- Concrete frost resistance
- Concrete mobility
- The use of different concrete brands
- Concrete selection for building foundations
The leading position among building materials has been holding concrete for many years. He owes such popularity to his unique operational qualities, incl.high strength, frost resistance and moisture resistance. Moreover, varying the ratio of the constituent components of concrete allows us to obtain a material with slightly different properties, which allows it to be used in almost any conditions. The question of choosing the right concrete remains the most important and difficult, because further construction properties depend on it.
It is equally difficult to choose a suitable concrete manufacturer. The growing demand for this building material has led to the emergence of a huge number of proposals, to navigate in which is quite difficult. So that a potential buyer of concrete could quickly find the best offer for himself, the concrete tender system “M350” was developed. It is presented on the http: //m350.ru/price/m350/ page and allows the user to quickly familiarize themselves with all offers for the sale of M350 concrete and other brands in the Moscow region and choose the most suitable one based on the price, the location of the plant or the mode of operation of the manufacturer. The system allows
to save time and money.
To be able to choose the right concrete mix for specific purposes, you need to know which indicators to pay attention to. Among the most important are the brand and class of concrete, the characteristics of moisture and frost resistance, as well as the mobility of concrete.
The most important characteristic of concrete is its ability to withstand the compressive stress of .This parameter is denoted by the letter M, and the index behind it indicates how much load each square centimeter of concrete can withstand. The exact value is determined under laboratory conditions, testing concrete that has hardened for 28 days, and a rounded value is recorded in the marking. For example, concrete that can withstand 98 kgf / m2 is designated as M100 , and concrete that can withstand 196 kgf / cm2 is M200.Simply put, the digital index says about the number of kilograms, which can press on 1 cm2 of concrete, without destroying it.
As of today, concretes are made from M50 to M1000 , but is most favored by concretes of the M100-M500 brands. The different level of concrete strength is explained by the differences in the composition of the : the proportions of the components used and their quality influence. The composition of the concrete includes sand, cement, crushed stone or gravel. Sand together with rubble( the so-called skeleton) are responsible for the bearing capacity of the future structure, and cement, when combined with water, is responsible for the strength of molecular bonds. The higher the proportion of cement in the concrete composition, the higher the strength of the concrete itself.
Plays the role and quality of components. Sand can be both river and pit - it is important that it be coarse and with a minimum amount of clay impurities. The optimum size of crushed stone is 20-25 mm, it should be from hard rock. Brand cement also affects the strength of concrete. As a rule, M400 and M500 cement is used, the latter will need less for the preparation of concrete of a given strength.
The least durable concrete grades are used in the construction of the lightest and less demanding structures. Foundations of private and multi-storey buildings, industrial buildings are created using more durable compositions( M200 and higher).With an increase in strength, the price of the composition also increases, so it is useless to use excessively durable compositions, as well as save.
The concrete class also speaks of the strength of the material, it is the modern derivative of the concrete brand .If, when determining the grade, the average value of the material strength is used, then the strength class assumes strength determination with guaranteed security. This is a more accurate value, which is expressed with a variation factor of 13%.Despite the fact that the class more accurately determines the characteristics of concrete, today most experts use the concept of brand.
Classes define with the letter B and the number from 3.5 to 60 : the higher it is, the more durable you are. There is a direct connection between classes and brands: for example, the M100 grade corresponds to the class B7.5, the M200 mark to B15, etc.
Relationship between grade and concrete grades by strength
Water-tightness of concrete
Water-tightness of concrete is understood to mean its ability not to pass water. Previously, this characteristic was denoted by the Russian letter B, now uses W , and the numerical designation next to it can start from 2 and reach 20 , equaling the water column pressure in kgf / cm2, at which a standard-sized cylindrical concrete does not let in.
If a foundation is built of concrete in conditions of high groundwater level , then it makes sense to choose a composition with a high water resistance value, to which special hydrophobic additives are added. By the way, the use of such material will reduce the cost of full waterproofing the foundation.
The hydraulic concrete has the highest water resistance and water resistance. For its production using hydrophobic or plasticized portland cement, sand and crushed stone of higher quality than for ordinary concrete. High waterproof performance is also achieved through installation with maximum compaction.
Frost resistance of concrete
The frost resistance of concrete is indicated by the letter F with a numeric value from 25 to 1000 : the higher it is, the greater the number of freezing and thawing cycles that the concrete can withstand without losing its strength properties. The choice will depend on the conditions in which the finished structure will be operated, on the climate, the number of freezing and thawing periods during the cold period of the year.
For the construction of hydraulic structures, airfield pavements and bridge piers, it is better to choose the most frost-resistant structures. In private construction, concrete class F100 or F200 is suitable for building a foundation. You can also focus on the density: the higher its value, the more frost-resistant the composition will be.
Concrete mobility( P) speaks about degree of fluidity , which is why the convenience of working with the composition directly depends. The numerical coefficient is expressed in the range of from 1 to 5 : the higher it is, the more liquid the composition will be. In private construction, the P2 and P3 concrete is used in the construction of the foundation. More fluid formulations are used only in cases when it is necessary to fill in a tightly reinforced base, or when concrete is supplied using concrete pumps.
Of course, it is more convenient to work with a more fluid composition, but you cannot add water to the ready-made concrete to increase the mobility of the composition. In this case, the grade of the solution immediately decreases, reducing the final strength.
Areas of use for different grades of concrete
Concrete is widely used, it is used to create foundations and a variety of other structures. Depending on the purpose of use select the concrete of a particular brand. Here are the main areas of use of the most common types of concrete:
- M100 is used to create road curbs and before pouring strip foundations;
- M150 suitable for pouring floors, foundations for the fence, as well as for organizing parking for cars;
- M200 is used in the restoration of buildings, the filling of paths, as well as for creating blind areas and the foundation of light buildings;
- M250 suitable for creating different types of foundations, as well as for sites and paths;
- M300 is used to create the foundation of brick houses, paving slabs and roads exposed to heavy loads;
- M350 suitable for creating monolithic foundations and foundations for high-rise buildings;
- M400 can be used both to create the foundations of residential buildings, and in the construction of bridges and structures on the water;
- M450 and M500 suitable for the construction of tunnels, sewers, bridges.
Choosing Concrete for the Foundation
Since concrete is used in organizing the absolute majority of foundations, the question of choosing it for these purposes requires more detailed consideration. In order to select the required brand, you need to know the weight that will be placed on the structure, the conditions of its operation, take into account the type of soil, the level of groundwater, etc. All this should be mentioned in the project documentation, and for those who are building themselves, we will provide information on the use of different grades of concrete.
The smaller the load from the building being erected, the less durable concrete will be needed. If an frame house is being built, then you can get by using concrete M200 , for a wooden house it is better to arrange the foundation of concrete M250.For two-story wooden houses, houses, it is better to choose concrete M300 from gas silicate and expanded clay concrete blocks. If reinforced concrete wall panels are to be used or plans are to build a brick house, then concrete M350, M400 and higher will be used for the foundation.
Affects the choice of concrete grade and soil type .The more heave the soil, the greater the differences in the load are on the foundation. So, for clay soils, it is better not to use concrete below M350, and for sandy and rocky soils, M200 is also suitable. If the groundwater level in the place where the house is built is high, then it is better to choose concrete with increased water resistance: even if M250 is suitable for loads, it is better to use M350, for which W is almost twice as high.
Whatever brand of concrete is used, the characteristics of the finished structure are also greatly influenced by the accuracy of the mixture dilution with water, as well as the process of filling the mold with concrete and the uniform distribution of concrete.