Components of concrete: characteristics, proportions,

The components of concrete determine its quality, strength, brand and class affiliation, as well as a host of other parameters and characteristics of the mortar and hardened material. We will tell you what ratio of concrete components is considered normal, and also show how to calculate the components for concrete.

The composition of the concrete mix

General information

Concrete is called artificial stone, which is produced by mixing the binder with water with the introduction of large and small aggregates, as well as various target additives - plasticizers, water repellents, antiseptics, etc. There are also anhydrous concretes, such as asphalt concrete and some others.

We will talk about traditional concretes used in civil engineering - cement-based mixtures as a binder, since besides cement, various slags, polymers, resins, etc. are used as binders.

So, for the production of cement concrete use such ingredients:

• Portland cement (sometimes quick-hardening slag cement) - mineral dust, which reacts hydration with water and hardens with the formation of a dense and solid stone. Plays the role of glue, which binds all components into one monolithic structure;
• Sand - fine aggregate, which contributes to the saving of cement and plays a role in creating a fine-structured framework that prevents deformation and the formation of microcracks during hardening and shrinking processes;
• Rubble - large aggregate, which, along with sand, reduces the cost of the mixture, as the price of aggregates is low. It prevents fracture during shrinkage and hardening, creates a structural framework and increases the elastic modulus of the material, and also reduces its creep;
• Water - one of the most important components of the mixture, which is involved in the process of cement hydration and the formation of hardening glue, and is also the medium where the mixing, interaction and uniform distribution of the remaining components of the solution occur;
• Additives - plasticizers, water repellents, antiseptics, seals and others. Increase certain indicators, such as fluidity, moisture resistance, frost resistance, chemical and biological inertness, density, etc.

Note! As you can see, the composition of the concrete mix is ​​heterogeneous, so the quality of the product depends on many variables. Grades of concrete and the ratio of components, as well as their quality and type are directly related.

Component Requirements

Now let's talk about the components in more detail. One of the main components, without which nothing happens, is cement. In construction, as a rule, Portland cement of the M300 - M500 grades is used, however, it should be noted that for the production of concrete of the M350 grade cement of at least M500 is required, and cement M400 will produce concrete of the grade not higher than M250.

The brand shows the compressive strength of the material, and for individual and civil construction, the strength of the M250 - M350 is quite enough, so you can safely use the product of the M500 brand even for critical nodes. The only remark is that the ratio of components in concrete for the foundation must be selected most carefully, therefore, commercial-grade mortar from the factory is usually used to concrete this part of the house.

Crushed stone is another important ingredient of the mixture. It is believed that the strength of rubble should be approximately twice the design strength of concrete, which it gains within 28 days. This is due to the fact that the concrete stone matures for several years and gains additional strength, which as a result becomes approximately equal to the strength of rubble, which remains the same for this indicator.

For the manufacture of traditional concrete is sufficient strength gravel rubble, which is approximately 800 - 1000 kg / sq. cm, which is enough for a concrete material brand M450. For the production of products brand M100 - M300, you can use limestone rubble, but the most durable and expensive is granite stone, which is most often used for the production of special, road and high-strength varieties of concrete.

  Note! Sometimes, deliberately used limestone crushed stone is used intentionally, for example, when grinding or cutting of reinforced concrete with diamond circles is expected. Also in this way, diamond drilling of holes in concrete is facilitated.

Sand can be used career or river, washed from clay and dust-like impurities. Most often used medium and small fraction, and for the manufacture of sand concrete take sand of large grain size.

If we talk about additives, it is worth noting immediately that the high-quality introduction of chemicals is possible only in conditions of factory production. Components for the production of aerated concrete, for example, include aluminum powder, pastes and emulsions, the dosage of which must be accurate.

Likewise, the components for the production of foam concrete — frothers — also need to be exactly matched to the recipe, because the components for foam concrete can spoil the material and lower its brand with a slight deviation from the norm.

Payment

As mentioned, the ratio of components is the most important parameter in the production of concrete mix. The classical instruction assumes such proportion (cement / crushed stone / sand / water): 1: 4: 2: 0.5. Numbers in proportion to mass fractions.

Of course, this ratio is rather arbitrary and approximately, since in practice we are dealing with real materials that have a lot of impurities, absorb water differently, and have different initial moisture. For a more accurate definition of the recipe, you should use tables and special computer programs, however, they also do not guarantee that the product obtained corresponds to the expected brand or class.

Even in the conditions of factories where there are laboratories and special equipment for weighing, dosing, mixing and preparing components, it is necessary to do mandatory tests of the obtained stone for strength, and only after that we can confidently speak of the class or brand affiliation of the material obtained.

There is a method for calculating the composition in field conditions:

1. Pour rubble into the ten-liter bucket to the top and shake the container so that the stone is distributed evenly over the bucket volume;
2. Using a liter jar or other measuring utensils, we add water to the bucket with gravel until it reaches the same level as it. Remember the amount of water. So we determined the required volume of sand;
3. Now pour the rubble and fill the bucket with dry sand to the extent that we have just identified. Then again add water with a measuring jar (preferably the same) until the sand is covered with water. The amount of water will be equal to the required volume of cement;
4. To determine the optimal amount of water, you should take 50 - 60% of the volume of cement, which we found experimentally in the previous paragraph;
5. At the end, you should take the calculated volume of concreting and divide it by the volume of one bucket - 10 liters, and multiply the resulting number by the previously calculated values ​​for each component.

Note! For demanding work, use ready-mixed concrete from proven manufacturers, as it is problematic to make a quality product in the field for a number of compelling reasons.

Conclusion

Качество, тип и соотношение компонентов определяют марку бетонного раствора и прочность будущего изделия. Для определения оптимальных пропорций существуют различные способы, однако добиться в полевых условиях точного соответствия проблематично (см.также статью «Бетон М150 – технические характеристики и особенности применения»).

The video in this article will help you see this.