How to prepare concrete mixture by hand proportions. How to mix high-quality concrete mortar yourself. Correct proportions

Concrete is a unique material. It is used not only in construction for the construction of buildings, from the strongest foundation to the complete construction of walls and roofs. You can also make piece items from it, such as balusters, vases, and even for the kitchen or living room. Modern methods of concrete preparation and processing make it possible to elevate this material almost on par with natural materials such as granite or marble. Although it is not as aesthetically pleasing as the latter, it is certainly known what it is made of, and there is no obligatory background radiation that natural stones often have. If you decide to abandon purchased concrete, then you should figure out how to make concrete with your own hands of the required quality, which will solve the problem at hand and will have sufficient strength and durability.

Although the process of preparing concrete is quite simple, it is necessary to take into account a number of features and points that will determine its quality and suitability. Depending on the purpose for which it is prepared, both the recipe and the method of its use change. So, first of all, let’s define what concrete is and what main characteristics it has.

In general, the composition of concrete is a mixture of cement mortar and filler. So the main ingredients are:

1. Cement;
2. Sand;
3. Filler (gravel, slag, crushed stone, pebbles, etc.).

In addition, modern technologies involve the use of special additives - plasticizers. Their role is to give concrete some unique properties.

The main characteristic of concrete is its compressive strength. We will not go into detail about how concrete was assessed for strength at different times, and will focus on the modern, universally used system. The strength of concrete is expressed in mega pascals (MPa), which determine the pressure that a certain class of concrete can withstand. Based on strength, concrete is divided into grades. In the CIS countries, according to GOST, classes are designated as B7.5 - B80. The difference depends on the type of cement used (M300-M600), sand and fraction, as well as the type of crushed stone. The number in the class name indicates the pressure in MPa that concrete can withstand in 95% of cases.

The simplest version of concrete is a simple mixture of cement mortar and coarse sand. This type of concrete is mainly used as a base for foundations. Preparation can be done directly at the bottom of the formwork under the foundation. In this case, very little water is added so that the mixture acquires the density of wet soil. There is no need to talk about strength in this case, but such concrete is excellent as protection for the main foundation from subsidence and excessive moisture.

More durable concrete involves the use of a variety of crushed stone as a filler with a fraction from 2-3 mm to 30-35 mm. The quality of concrete directly depends on the purity and composition of all its components. So before you figure out the proportions and preparation methods to make a concrete solution correctly, it’s worth considering each component separately.

Requirements for concrete components

Cement

Cement is the main and only ingredient of concrete that binds all components together. Portland cement is the most suitable for preparing concrete. It is distinguished by an increased and prevailing content of calcium silicates (up to 78-80%), which ensures improved adhesion and bonding of materials. However, depending on the task at hand, other types of cement are also used.

The most suitable grade of cement for private construction is 500. You can also use standard M400, but this will affect the durability of the same foundation.

In addition to good adhesion, Portland cement is better suited for working at low temperatures. Even so, you cannot work with concrete at temperatures below 16 degrees. If there is a good reason to use concrete at lower temperatures, then special additives and plasticizers will be required, but more on that later. For work in hot weather, Portland slag cement is better suited.

In the domestic marking of cement, in addition to the designation of its declared strength in the same MPa, which is marked as a brand, there is also the designation “D”, after which a number is placed indicating the amount of foreign impurities in the cement. Actually, for the preparation of high-quality concrete, cement M500-D0 or M500-D20 is suitable, that is, with impurities from 0 to 20%.

The cement must be dry and free-flowing. Under no circumstances should you purchase damp or lumpy cement, and you should also not save too much and buy unlabeled, stale or discounted cement. After all, concrete will be used to construct important elements of the house, so your well-being and safety depend on it. In unsuitable conditions, cement can very quickly absorb moisture from the air and lose a significant part of its qualities.

It is better to purchase the required amount of cement a maximum of 2 weeks before direct use or a few days in advance. Check the presence of markings and the integrity of the packaging.

Sand

Regardless of the aggregate used, crushed stone or gravel, sand will also be required. Only in some cases do they do without it, when it is possible to compact and select large aggregate so that the gaps between all components are minimal.

Sand suitable for preparing concrete should have a fraction of 1.5 to 5 mm, best when it has a uniform size with a variation of no more than 1-2 mm. The sand should not contain foreign impurities. All kinds of plant debris, construction debris and any inclusions that may disintegrate or rot over time will adversely affect the strength of concrete. To be on the safe side, if the sand is not completely clean, it is better to pass it through a sieve with fairly small cells. Actually, the same applies to crushed stone.

River sand is best suited; although it is more expensive than gully sand, it has a suitable grain size and does not contain silt inclusions or clay. Unlike cement mortars, which are used for the construction of brickwork or plastering, in which the presence of clay can only help, because it will be easier to level it, it is not permissible in concrete. It is important to ensure maximum adhesion of the cement mortar with large aggregates, which determine the overall strength of concrete. So it is better not to use sand with loam or grains less than 1 mm at all for preparing concrete, because it is very difficult to get rid of them. To do this, they use the procedure of washing and settling the sand, which, even in industrial conditions, is not always profitable or easy.

Alternatively, for areas near which there are stone quarries, artificial heavy sand can be used. It is obtained as a result of crushing rocks and is characterized by greater mass and density. If it is washed properly and separated by particle size, it will be even slightly better than river sand. It is only important to take into account when preparing and when using that the concrete will turn out to be much heavier; this is important if it is used in the construction of screeds over interfloor ceilings. A significant obstacle to the use of heavy artificial sand may be the possible increased background radiation, which depends on that of the parent rock.

Aggregate. Crushed stone, gravel

The main strength of concrete comes from filling it with gravel or crushed stone. Sea or river pebbles are in no way suitable, because their surface is polished with water and does not provide proper adhesion to the solution. The best material is obtained from crushed rock.

It is important to take into account the characteristics of the breed that was used. Expanded clay or other similar materials are also often used, which are quite strong, but at the same time light. Below we will consider the principle by which you can select the appropriate material for preparing concrete, which will provide the necessary strength and reliability for specific situations. The size of gravel or crushed stone can vary from 8 to 35 mm; larger pieces are used mostly in production, and even then rarely. As with sand, it is desirable that the aggregate contains as little dust or clay inclusions on its surface as possible. The debris must be picked out before the gravel goes into the solution. The higher the roughness on the particle faces, the better. Reliable grip depends on this.

To prepare concrete yourself, it is better to choose either an aggregate, which itself has particles of several sizes, or mix coarse gravel with medium gravel. In the absence of professional equipment for compacting concrete, this will ensure a tighter fit of the aggregate particles to each other and will prevent the formation of large voids. Otherwise, the latter will be filled with mortar, and this will affect both the strength of the concrete and the consumption of the mortar itself.

For storage, it is better to store both sand and crushed stone or gravel in bulk near the place of use. In order to prevent contamination of materials and moisture from the soil, it is better to place the embankments on a spread tarpaulin or an area with a solid base. In the simplest case, when materials are poured directly onto the soil, the lowest layer that is in contact with it should not be used.

Water

The moment of choosing water is very important. There is, of course, no question of using any special water. However, it must be clean and free of alkaline or acidic foreign matter. You cannot use river or, especially, lake water, which contains more than enough inclusions. It is best to follow a simple rule: water that is suitable for drinking is also suitable for making strong and good concrete at home. Only by following this rule can you expect that the concrete will be durable and last a long time without any damage or destruction.

Supplements

• Lime. Some craftsmen add a little slaked lime to the concrete composition, this increases the workability of the solution. This somewhat facilitates the process of leveling the surface of the concrete screed or cast section of the porch or outlet. And yet, in addition to this, lime can interfere with the normal bond between cement and aggregate, which will affect the strength. The choice of whether to resort to using lime or not remains with the master, when he knows exactly what is best at the moment. There is no need to extinguish lime yourself for a long time now. Instead, ready-made slaked lime is used, which is sold in construction stores and is called fluff.
• Plasticizers. To give the concrete solution greater fluidity or reverse viscosity, various plasticizers are used, which change the properties of the solution in a given direction. The use of plasticizers can increase or decrease the amount of water required to prepare the solution. For work such as pouring a foundation, plasticizers may not be used, but they can play an important role if the reinforcement is quite dense or the foundation has a complex shape. At the same time, more fluid concrete will fill all voids and branches faster and more reliably, which will speed up the process and improve the result.

Plasticizers for concrete

• Auxiliary components. In addition to the above, special additives can be used to impart more advanced properties to concrete. Thus, additives can be used to ensure that concrete sets and hardens at low temperatures or in the presence of large amounts of moisture. Appropriate additives are used for various purposes. It is important to decide whether to use them and select the necessary additive at a hardware store. Carefully study the instructions for use and properties of the additive. If the conditions in which concrete will be used have limiting parameters in terms of temperature or humidity, then additives and plasticizers will be indispensable.
• Reinforcing substances. In addition to concrete aggregate, specific additives are often used for additional reinforcement. So, when using concrete, a special polypropylene or polyvinyl chloride fiber is used to make a fairly thin screed. It itself is soft and not particularly strong, but it will help to avoid situations where concrete cracks at the points of convergence of floor slabs or in the case of an unstable base when forming the main floor on top of soils.

Selection of ratios of materials for preparing concrete

Different purposes require different concrete compositions. So, to form a foundation for a house, you need strong concrete with the inclusion of large crushed stone with elements ranging in size from 20 to 35 mm, and the amount of mortar is sufficient to fix the aggregate. In this case, the solution must be fluid, because it is necessary to firmly compact the concrete and remove all air bubbles from it. However, before pouring the main part of the concrete, you should equip the substrate. For this purpose, the easiest to prepare and less durable concrete, B7.5, is used, which in addition to cement mortar may contain only coarse sand. Moreover, for this purpose the concrete solution is not made liquid, but more similar in consistency to wet soil.

To construct foundations, you will need an average size fraction of filler and still a liquid solution. This will ensure ease of distribution of the solution over the surface in a fairly thin layer. Also, the fine and medium fraction of the aggregate is indispensable when forming elements such as balusters, decorative elements or garden utensils and fills, small elements such as a porch or steps.

The composition of concrete in terms of ingredients and their ratio must be carried out in accordance with GOST 7473-94 and SNiP 5.01.23-83. This takes into account the density of each of the ingredients used and the required average density of concrete, which is necessary in a particular situation. After the weight and volume ratios of the ingredients have been calculated, you can begin the planned preparation and pouring of concrete.

The most common proportions of concrete are 1:3:6 parts, respectively, of cement, sand and aggregate and 0.5-1 part of water, depending on the required fluidity of the solution. However, more often than not, adhering to such a layout results in an unsatisfactory concrete result, and this will be visible only after a while, when it will be quite difficult to correct anything. It is best, in accordance with the presented regulatory documents, to perform an essentially simple calculation and protect yourself from unpleasant consequences. All this is due to the fact that both aggregate and sand, and cement, can vary significantly in density parameters and bonding characteristics.

After the calculations, you should decide on a practical method for measuring the ingredients. After all, we now only have volumetric and weight parameters, and they are somewhat incompatible with those in a real situation. The same sand can be quite wet or excessively loose, so that a 10-liter bucket will contain far less than the weight that would be expected from calculations of the density-to-volume ratio.

In terms of the moisture content of the same sand and gravel, it is better to dry them than to try to roughly calculate the number of servings of a particular ingredient. And to determine the looseness and the removal of portions, it is enough to weigh the portions of each ingredient in relation to one volume. That is, take a bucket or other convenient container and fill it without compacting it with sand, cement and filler alternately, and weigh the resulting portion. Then, through simple calculations, it will be possible to convert the previously obtained calculations into the ratio of buckets.

With what and where to mix concrete?

Whatever one may say, for mixing concrete it is best to use concrete mixers specially designed for this purpose. This is the only way to quickly and efficiently mix all the components and deliver the concrete to its destination before it begins to set and delaminate. The old-fashioned manual method in a tub is not particularly suitable for more or less large volumes. However, there is no way to control the mixing and addition of ingredients so that it happens according to the recipe. The last statement requires clarification. After all, many people don’t understand how, if everything is done by hand and under constant supervision, you can violate the recipe and ruin the concrete.

Everything is very simple. There are two options for making concrete yourself:

1. In the first case, first all the ingredients, or at least cement and sand, are mixed dry, and then water is only poured in.
2. In the second case, cement, sand and aggregate are poured into poured and measured water.

With dry mixing, the materials seem to be distributed evenly, but when adding water and manual mixing, there is no guarantee that the entire volume will get wet quickly and efficiently. As a result, it turns out that a dry, unmixed composition remains at the bottom, and therefore a violation of the proportions. If you mix thoroughly and for a long time so that there are no dry lumps left, then too much time will pass, and again the solution will begin to set and separate. This will not affect the appearance, but the strength – yes. If you add everything to water, again the cement will be mixed for too long and will not be able to properly adhere to the fillers later. The second option is at least a little better than the first, so this is how concrete should be mixed in small quantities.

So, the hand kneading option is not particularly good. It’s better to rent a concrete mixer, or buy one and mix everything in it. The concrete mixer should be located no further than 40 meters from the place where the concrete will be used. This will prevent the concrete from delaminating during transportation and mixing. All ingredients should also be nearby, or at least in parts, delivered to the concrete mixer.

Mixing concrete

The volume of a conventional concrete mixer is equal to 200 liters of the mixed solution. It is to this figure that all calculations for the amount of each ingredient should be made. Next, we begin preparing the concrete, gradually adding everything to the concrete mixer.

• The required amount of water is poured. About 10-15% can be left to add later. This will make it easier to mix once all the materials have been added.
• Cement is being laid. If water was left, then the same amount of cement should be put aside.
• Sand is poured in next. At this stage, stir until all ingredients are evenly distributed, this is about 2-3 minutes.
• When the cement mortar is ready, all the necessary additional components are added to it, such as plasticizers, additives, and reinforcing compounds.
• Lastly, the main aggregate (gravel, crushed stone) is poured. If it is necessary to add water, then first mix water with cement and then only the resulting laitance is poured into a concrete mixer.

The entire process should take approximately 10 minutes. If you stir for too long, the cement in the solution may begin to set.

The solution is transported by wheelbarrow. If the entire batch does not fit into the wheelbarrow, the remaining solution remains in the turned on concrete mixer and is mixed.

Video: mixing concrete by hand

Pouring concrete

Now you need to properly pour and distribute the concrete. The result depends on this no less than on the two previous stages. Concrete is a heterogeneous solution, and therefore for its correct distribution it is necessary to compact it so that the aggregate is packed as tightly as possible inside the solution. In addition, you should make sure that there are no air bubbles left in the solution.

Vibration is used for this task. The use of specialized vibrating units allows for high-quality and quick compaction of concrete. For foundations and walls, a special tool is used that has a vibrating hose. It is immersed in the solution, and thereby compaction occurs. For thin layers, such as screed, surface devices that have a long lath are used. Under the influence of fine vibration from the drive, it is moved along the surface. In this case, the surface of the concrete is leveled, and it is immediately compacted.

In the process of pouring concrete, it is necessary to use a sharpened rod of reinforcement and pierce the solution to the entire depth. This releases all the air that could be stuck in the reinforcement mesh and in the solution itself. Since the pouring is done gradually, when piercing a new portion of concrete, you should go at least 10 cm deeper into the previous layer to securely fasten them.

As a result of the described actions, the concrete filler should be compacted tightly, and an even layer of mortar should appear on the surface. The last step will only be to level the top layer. This can be done in several passes as the solution adheres and dries within two to three hours.

If it is not possible to purchase or rent professional equipment, then you should try to do the same manually. In the case of a foundation, vibration must be created. To do this, apply uniform blows to the sides of the formwork with a sledgehammer. You should hit not on the boards of the shields, but on the beams that hold them together.

To ensure uniform drying and protect the concrete from external factors, it is necessary to cover it with film. This will prevent the surface of the concrete from drying out too quickly ahead of the interior and will protect it from external factors such as sun, heat, cold, etc.

The approximate time for concrete to dry to the point where you can safely step on it is 36 hours. Everything naturally depends on the thickness of the layer. It may take up to a week or two to dry completely. Concrete, in fact, will completely dry and strengthen within six months after this. Maximum strength will be achieved only after more than a year. Further work can be carried out within a week.

Video: features of pouring concrete

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Discussion:

Gosha said:

When preparing concrete, it is important to know for what purpose the concrete will be prepared! Foundation, path, etc. Or what else?
And therefore the ratio of cement to the amount of crushed stone or gravel is also important. But the classic scheme, I think, is this: 1 bucket of water, 1 (1.5) bucket of cement, 3 buckets of sand, 3 buckets of crushed stone or gravel.
In appearance, the solution should look like thick gray “fat” sour cream. If the solution looks a little darker (blacker), but in general the crushed stone and sand “float” separately from the water and are weakly “connected” with each other, then it means a) either a lot of water, or b) LITTLE cement!
Then you need to add more cement until the solution again seems like thick GRAY sour cream! Gray thick sour cream is the “face” of a good concrete solution.

In the matter of concrete (and not “mortar” for laying bricks, for example), the key and “connecting link” is still cement! It is the “main” material in the solution. Without it, everything else will not “knit” and “stick” with each other!
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Concrete is a building material with unique properties. It is used not only when constructing structures, objects and buildings, when pouring foundations or erecting roofs, ceilings, partitions and walls. Concrete is often used in the manufacture of pieced architectural and construction elements, exterior and design elements. Modern technologies for making concrete and working with it correctly place this artificial building material on a par with such super-durable natural materials as marble and granite.

The aesthetics of concrete leaves much to be desired in comparison with marble, but its advantage is that builders know its composition, which means they can make changes to it both in terms of strength or durability, and in terms of the appearance of products and structures. In individual construction, most often there is no need to purchase concrete from a manufacturer - the required amount of mortar can be made independently, you just need to know how to make concrete correctly.

Requirements for concrete preparation

It is not difficult even for an amateur to prepare a concrete solution, if you correctly take into account some of the features of the preparation and characteristics of the mixture, which determine the quality and technical and operational characteristics of concrete. The operating conditions of a concrete product determine its composition and method of preparation.

1. Portland cement;
2. Purified or river sand;
3. Mortar filler (crushed stone, pebbles, gravel, blast furnace or ash slag);
4. To improve some parameters, plasticizers are added to the solution.

The main requirement for concrete is sufficient compressive strength, which is measured in MPa (megapascal). This unit reflects the pressure that a particular prepared concrete can withstand. Based on the strength indicators, the grade of material is determined, designated by symbols in the range B 7.5-B 80. The numbers in the designation reflect the pressure limits that concrete can withstand in 95% of cases.

The simplest concrete mortar - a mixture of cement and sand - is often used to fill the foundation. Brands of concrete with greater strength use coarse crushed stone. Also, the strength of the material depends on the degree of purification and the composition of the ingredients.

Requirements for concrete mortar components - cement

Cement (Portland cement) is the main ingredient of the solution, binding all substances into one. It is called a binder. Portland cement has an increased content of CaSiO 3 (calcium silicates) to 78-80% to improve the adhesion of components. The most popular grade of cement in individual construction is M 500. The lower the grade, the lower the durability of the cement and the strength of the concrete structure.

Portland cement behaves well at negative street temperatures, but not lower than -16 0 C. If it becomes necessary to work with concrete at temperatures below the threshold, then plasticizers are added to the solution. At temperatures above +25 0 C it is better to use Portland slag cement.

More advanced marking of cement includes the symbol “D” with a number indicating the percentage of plasticizers. For example, cement grade M 500-D10 or M 500-D25 contains 10 and 25% impurities, respectively.

High-quality working cement is a dry bulk substance. If the cement is wet to the touch and has lumps, then it is not suitable for work. The quality of cement is also affected by the period of its production and storage. Therefore, it is better to buy cement in the required quantity 10-14 days before use.

1. M 600 – 90 days;
2. M 500 – 180 days;
3. M 400 – 180 days.

For other brands, shelf life without loss of quality is ≤ 60 days. Cements with rapid hardening properties can be stored for ≤ 45 days.

Importance of sand in concrete mortar

Cement cannot be prepared without sand, except in certain cases when it is allowed to use fine-grained crushed stone or gravel filler. The most suitable fraction size is 1.5-5 mm, without impurities and excessive moisture. Unrefined sand is sifted through a fine metal sieve.

Composition of concrete made from cement grade M 500:

An intermediate solution to the use of sand is to use heavy sand of artificial origin, for example, from a stone quarry. This sand is obtained by crushing or blasting rocks; it has a high density and large mass. With high-quality washing and sifting, quarry sand has some characteristics superior to river or sea sand. The peculiarity of using quarry sand is that the concrete becomes much heavier - this must be taken into account when building several floors in a house.

The role of aggregates in concrete

Concrete becomes strong precisely because of the addition of crushed stone or gravel. Smooth pebbles cannot be added, as they will not adhere well to the solution. The best fillers are crushed stone and gravel, which have a rough, rough surface. Less commonly, expanded clay or slag plays the role of filler.

Fractions of crushed stone or gravel used in individual construction can have dimensions of 8-35 mm; larger crushed stone is used in the industrial preparation of concrete. Like sand, the filler must be clean, free of impurities and excess moisture. High roughness of fillers is welcome, as it improves the adhesion of particles inside the solution.

Before preparing concrete, the proportions of which take into account the place of its use, you need to select a filler with the presence of different fractions, or mix large and medium gravel (crushed stone). If compacting concrete is done manually, then such mixing of aggregates will only add strength to the concrete, since less air will remain in the solution.

It is advisable to store all bulk building materials near the construction site until use. To prevent materials from drawing moisture from the soil, they should be laid on waterproofing - tarpaulin, polyethylene, etc. If it is not possible to protect sand, crushed stone and loose cement from the effects of soil moisture, then it is not recommended to use the bottom layer of bulk building materials to prepare the solution.

How to choose water for concrete

Water with unique or special characteristics is not needed - it is enough that it is clean, with a normal pH level. It is not recommended to add water from a river, lake or pond - the acidity will be disturbed in any case, and this will affect the strength of the concrete. The basic rule when choosing: water suitable for drinking is also suitable for preparing concrete.

Additives and plasticizers

Adding lime to concrete mortar improves its workability. For example, when leveling complex surfaces, such an additive will be beneficial. But it is necessary to decide whether to add lime or not locally, based on the functional and operational purpose of the concrete structure, since lime can reduce the adhesion of components. You need to use slaked lime, which is commercially available everywhere.

To change the properties of a concrete solution in one direction or another (for example, to make it more fluid or viscous), various synthetic plasticizers are added to the mixture. Such additives also affect the volume of water added - more or less may be needed, depending on the parameters of the additives. When pouring a foundation that does not have high requirements, plasticizers may not be added, but with a complex structure of the reinforced frame or a geometrically complex shape of the foundation, such additives are necessary - they will make the structure stronger and more reliable. The flowing solution will quickly fill the voids, displacing excess air, accelerating the process of setting and strength gain.

If construction is carried out in winter, then anti-frost additives will significantly improve the progressive characteristics of concrete. There are also additives that allow you to work with concrete mortar in conditions of high humidity or hot weather. To achieve different goals, various auxiliary components can be added to the solution. Rules for the use of plasticizers, stabilizers and other additives of artificial origin are always indicated on the product packaging. The use of additives for various purposes is mandatory and necessary if the conditions of concrete use have extreme characteristics in terms of humidity, temperature or pressure.

Reinforcing additives increase the strength properties of fillers - crushed stone or gravel. For example, if you need to make a thin but strong concrete screed, it is recommended to add special polyvinyl chloride or polypropylene fiber. Its presence in the concrete solution prevents microcracks from appearing at the joints of floor slabs, as well as if an unstable base is used when building up the load-bearing layer of a concrete floor.

Optimal concrete proportions can be obtained by mixing four components: crushed stone, cement, sand and water. The first component is the binding link in the mixture, making it homogeneous and quite thick.

In some cases, it is permissible to use gravel instead of crushed stone, but in this case it must consist of different fractions. As a rule, flat and wide stones included in the gravel mixture should not exceed 10% of its volume. Foreign additives and impurities in gravel are also unacceptable, as they can negatively affect the strength of the finished foundation. Online calculation of the composition of cement mortar.

When choosing other components, it is also necessary to comply with the necessary requirements. River sand is an ideal choice as an ingredient. It is strictly not recommended to use sand mixed with clay, which completely reduces the strength of concrete and makes the solution greasy. Due to the property of clay to shrink and swell under the influence of water, cracks will form on the surface of the material, even at the hardening stage. After some time, the foundation will disintegrate due to the high concentration of clay.

Unlike gravel, the size of the crushed stone fraction should be in the range from 1 to 2 cm, which is the best option. Crushed stone must be clean and free of any impurities.

People who have no experience in construction mistakenly believe that the more cement poured into the solution, the better. However, in reality this is not the case. An excess of the component will lead to the monolithic structure falling into pieces. This is why it is necessary to comply concrete proportions, established by GOST.

The amount of cement directly depends on the purpose of the future solution. If the goal is a foundation, as a rule, cement grade M 500 is used.

As for water, it must be clean and not contain any impurities. In particular, the ingress of particles of gasoline, oil or paint, which will lead to deterioration of the strength and delamination of concrete, is unacceptable.

Preparation of concrete according to proportions.

High-quality materials will not be enough to build a concrete foundation. You must be able to mix concrete and know several nuances of preparation.

If you use a concrete mixer to prepare the mixture, after turning on this machine, you need to adhere to this procedure.

1. First of all, a little water is supplied to the device. Subsequently, cement is added to the water and mixed with water until smooth.

2. The next step is to add some sand. You cannot pour all the sand at once; you need to do this gradually, in small batches.

3. Having mixed the sand with the remaining components into a homogeneous mixture, you can pour in crushed stone and the remaining part of the water. All components are added little by little until the solution becomes homogeneous, the same goes for water.

By adding too much water to the mixture, you will get too thin a solution and, as a result, low foundation strength. Accordingly, a small amount of water will lead to excessive thickness of concrete. Such concrete is very difficult and inconvenient to work with; it will be difficult to pour it into formwork and level it.

Therefore, it is necessary to know the optimal concrete proportions. Not taking into account water, the ratio of components should be 1: 3: 5, corresponding to cement, sand and crushed stone. That is, if you need 1 kg of cement, then you will need 3 kg of sand, and 5 kg of crushed stone. This is the formula that is used to lay the foundation during private individual construction. Depending on the purpose, the ratio of water to cement can vary from 0.4 to 0.7.

Brands, proportions of concrete.

To obtain one or another brand of concrete, a different ratio of components will be required. M450 concrete is considered the most durable, while grades like M100 and M200 are more fragile.

Let's consider the ratio of the three components using the example of different grades of concrete

• Concrete M100 - 1:5.8:6.1 (cement:sand:filler)
• Concrete M200 - 1:3.5:5.6 (cement:sand:filler)
• Concrete M300 - 1:2.4:4.3 (cement:sand:filler)
• Concrete M400 - 1:1.6:3.2 (cement:sand:filler)
• Concrete M450 - 1:1.4:2.9 (cement:sand:filler)

If you study carefully concrete proportions different brands, then a certain trend can be observed in which the amount of sand and filler decreases relative to cement. The higher the grade of concrete, the smaller the difference between the components.

To get a good mortar for the foundation, it is best to use cement grade M 500. Having studied all the components to obtain a high-quality mortar, it is important to remember that you should not hesitate with the prepared mortar, since the concrete mixture hardens quickly and cannot be stored. The resulting concrete must be used within the first two hours after preparation.

If foundation pouring work is carried out in winter or in very cold places, then it is necessary to use warm water, since concrete hardens faster in the cold than in warm seasons. In addition, in winter it is recommended to use special additives that are added directly to the solution itself. This is done to preserve the properties of concrete, since proportion of concrete components is not the only deciding factor.

The composition of the concrete mixture is no secret to anyone: all that is required is to mix sand, cement and gravel, add water and mix. However, the resulting solution is completely different from industrial concrete slabs. It is fragile, afraid of moisture and cannot withstand the cold. To prevent the preparation of concrete mortar from turning into such a disaster, it is important to correctly measure the proportions, carefully select materials and take into account all the recommendations of experts. We'll start with materials.

Scheme for preparing a concrete mixture.

To make a high-quality concrete solution, you need to use Portland cement marked M350-M500, no less, for the base. This is a heavy and especially strong cement from which high-quality concrete can be made. Cement grades less than 350 are lighter, they are suitable for plastering work, but not for heavy and durable structures. It is best to opt for Portland cement M500.

The next component is sand. It would be correct to make concrete mortar from river rather than sea sand. The latter contains many impurities that can affect the quality of the composition. You should not take sand contaminated with organic substances (oils, algae) or clay. You can also use gully sand. Its grains of sand are less smooth than those of river sand, so it adheres better to the components of the mixture. Whatever sand you choose, it must be well washed and cleaned.

Composition of the concrete mixture.

The next element is gravel or crushed stone. Those who use pebbles, broken brick, gypsum, chalk or other types of gravel in the solution instead of gravel do it wrong. Pebbles are poorly fixed in the composition due to their smooth surface; broken brick crumbles heavily, absorbs water and breaks; other types of gravel are not strong enough. To prepare a solution for concrete, it is correct to use granite gravel.

Additives and plasticizers

Plasticizers are substances that increase the characteristics of a concrete mixture, its strength and durability. Preparing concrete mortar at home without plasticizers is simply impossible.

A good plasticizer can make concrete waterproof, plastic, and increase adhesion to reinforcement and surfaces.

Plasticizers enhance the strength and durability of concrete.

The solution with the plasticizer mixes well, completely fills the mold, there are no undissolved lumps of cement or sand, and no voids are formed. Water resistance allows you to best protect the concrete mixture from destruction due to freezing and freezing of water in it.

There are a huge number of plasticizers and additives on sale from different manufacturers for every color and taste. You should focus on the declared properties, cost and professional reputation of the manufacturer. A good plasticizer increases strength, fluidity, adhesion and water-repellent properties.

When a composition of special strength is required, it is correct to use reinforcing additives that increase the tensile strength of the material. To do this, when preparing a solution for concrete, fibers are added to the composition, which additionally fasten the structure. Glass fiber, polymer fiber, basalt fiber, metal threads, and fiber are used as such reinforcing components.

Manufacturing algorithm

Table of components for making concrete mixture.

The standard proportions of concrete mortar are as follows: 1 part cement: 2 parts sand: 3 parts gravel. Additionally, to make the solution stronger and more durable, additives and plasticizers are added in accordance with the manufacturers' instructions. Water should be added with extreme caution, just enough so that the composition becomes fluid and flows off the trowel. It is best to add water in small portions in several stages. Good and liquid solutions differ from each other by only 2% water content. Therefore, be careful and take your time. The volume of water in the mixture is equal to half the weight of the cement, that is, 50 kg of cement requires 25 liters of water. The proportion is approximate; when adding water, you should focus on the consistency of the solution.

The homogeneity of the mixture is the key to preparing a high-quality concrete solution. The composition should not contain lumps, clots, cavities with water or air bubbles. A completely homogeneous, homogeneous composition is a prerequisite. Until it is completed, you cannot move on to the next steps. Concrete hardens quickly, so it makes sense to prepare the exact amount of mixture that will be used immediately.

Preparation in a concrete mixer

An electric concrete mixer makes life much easier for builders, both professionals and beginners. The device allows you to not only save time, but also effort, because manual production of concrete is a very, very labor-intensive process. In addition, an electric concrete mixer can perform a much larger amount of work than a person in one unit of time. And the mixture prepared in a concrete mixer is more homogeneous.

The process of preparing concrete in a concrete mixer (1, 2, 3 – movement of concrete).

As practice shows, the sequence of adding components does not matter for the homogeneity of the composition. Provided that the proportions and mixing are carefully observed, 10-15 minutes of operation of the concrete mixer guarantees complete homogeneity of the composition. The operation of a concrete mixer, due to the special thoroughness of mixing the composition, makes it possible to increase the strength of concrete by 40-80% than when mixing manually. Therefore, if possible, it is better to order a ready-made concrete solution from the manufacturer, which will meet all the requirements for strength, reliability, uniformity and proportions.

The classic recipe for preparing concrete in a concrete mixer is simple: first pour in water (about 80% of the norm), followed by gravel, and then sand. They are mixed for several minutes. Next, cement and the rest of the water are added, the amount of the last component is adjusted depending on the actual consistency of the mixture. Run the mixing cycle again. A concrete mixer is simply necessary for large volumes of concrete production that cannot be prepared at home.

Manual mixing of concrete

If the concrete solution is prepared manually, you will need the following tools:

If the concrete will be mixed by hand, a shovel type will be required.

• a wooden panel or box with a bottom made of roofing iron;
• shovel type;
• bucket;
• watering can with mesh;
• rake.

And materials:

• cement;
• sand;
• gravel (crushed stone);
• water;
• plasticizers and additives.

It is best if the wooden flooring is covered with roofing iron. For ease of mixing, it is recommended to raise the shield 30-50 cm above the ground. It is highly not recommended to prepare the concrete composition directly on the ground, as foreign impurities will get into it, deteriorating the quality of the concrete. When manually preparing concrete mortar, cement and sand are first mixed in dry form. Sand is poured onto a wooden flooring in the form of a bed with a depression. Cement is added to it. The composition is thoroughly mixed until completely homogeneous in color and texture; the components should be mixed at least 3 times. The dry mixture is easier to work with than the solution, so try to make it as homogeneous as possible at this stage. You can mix the dry mixture with your hands, which is much more convenient, or with a shovel.

Scheme of manual mixing of concrete.

For high-quality grouting for joints, sand and cement should be additionally sifted dry. Then form the bed again with a depression and add gravel (crushed stone) and other fillers. Knead the mixture again at least 3 times. Add some water and stir again. Gradually add water in small portions, mix the mixture thoroughly until it reaches the desired consistency. It is best to add water through a watering can with a mesh so that a strong water jet does not wash out cement particles. To facilitate the process of mixing the concrete mixture, it is recommended to wait 5-10 minutes after the first watering. During this time, water will have time to penetrate into the lower layers of the composition.

You can also make a concrete mixture in a box with a roofing iron bottom using a metal rake. This is one of the simplest, but at the same time time-consuming methods. The dry mixture, as in the method described above, is mixed in small portions with a rake, moving from one edge of the box to the other. Water is then added and the cycle is repeated again.

Table of proportions for the production of concrete.

There is a direct relationship between cement grades and concrete grades. Depending on the purpose of use (pouring foundations, slabs, load-bearing walls, decorative structures), concrete is divided into grades. The higher the grade, the stronger the concrete. To produce concrete, the grade of cement must exceed the grade by 2-3 times. For example, to get concrete M150, you should take cement M300-M400. The same dependence in strength can be seen in crushed stone: its grade should be approximately 2 times higher than the design grade of concrete. The fact is that the design grade of concrete, the so-called 28-day grade, is always inferior to its real strength, which the material gains in 0.5-1 year. Crushed stone is not endowed with the ability to increase strength, unlike concrete, therefore, to level out the difference, strength selection is required.

It is best to measure proportions using measuring buckets. Putting components in with a shovel can result in incorrect proportions or the introduction of inappropriate components. To be sure that the entire solution will be the same in strength, with an even color after drying, it is best to measure sand and cement with a bucket. After mixing the mixture, it is recommended to check it for homogeneity. To do this, leave the composition for a few minutes so that small air bubbles appear in it. Then the mixture is scooped onto a shovel, shaken and turned over. If the solution falls, then you should add a little dry mixture or water to it.

Concrete should be plastic, moderately fluid, moderately thick. To make one cubic meter of concrete you will need approximately 350 kg of cement, 0.6 m 3 of sand, 200 liters of water and 0.8 m 3 of crushed stone. This consumption is imprecise; it depends on the brand of cement, the purpose of the concrete, weather conditions during mixing and many other factors. The concrete mixture is checked for readiness as follows: a row of ribs is made in the solution with a shovel, moving the tool towards you. If the surface of the composition remains smooth and even, the ridges retain their shape and do not fall off, the mixture is ready.

Most often, concrete is used in the construction of certain objects and serious finishing work. They are used not only for the construction of walls or roofs, but also for the most important thing - for the base, for the foundation of the building. The better the concrete, the higher the quality, the stronger the building will be. In addition, concrete is also used in the manufacture of one-piece objects with your own hands, for example, paving slabs, garden vases, urns, and in special cases you can even make a tabletop.

Concrete is very popular due to its qualities, which are in many ways similar in strength characteristics to natural stone, such as marble or granite. Yes, concrete is not that beautiful. But, unlike stone, it has a number of advantages. For example, it does not emit radiation, is much cheaper, and can be made beautiful by the light of the correct finishing if the repair is done by hand. There are also modern processing methods that increase the aesthetic appeal of the material.

When using concrete mixtures, many people prefer store-bought ready-made mixtures. But you can do it yourself if you know the required qualities, characteristics and proportions.

What should the concrete composition be?

To talk about mixing with your own hands and about proportions, you need to immediately decide on the components used in the production of such building materials.

So, what ingredients need to be used to make the mixture:

1. Cement. These are the main elements for making the solution. Cement is made from limestone, which when mixed with liquid causes crystallization, which then allows the concrete mixture to harden.
2. Ballast or general mixture. This is the name of the gravel-sand component. Although concrete can be different and the proportions needed are different, most often three parts of gravel to one part of sand are used. The sand taken is fine-grained river sand.
3. Construction sand. It can be lacustrine, marine, aeolian. Less commonly alluvial or deluvial. It should be a sand-round component that easily fits bricks or concrete slabs.
4. Crushed stone. And finally, remember the crushed stone. This rock is crushed, with a size of no more than five millimeters.
5. Water. Water gives it a cohesive structure. It is necessary to make concrete, taking into account not only the proportions of water and dry parts, but also the moisture content of other elements, as well as their ability to absorb moisture.

As you can see, the components are simple and affordable, but you need to be able to understand their quality before buying.

The cement-sand mortar used in the production of concrete has also found its application in brickwork, plastering of surfaces, and construction of stoves. It’s easy to make such material with your own hands. In this case, clay can, of course, serve as an alternative to cement, and to replace sand, you can safely use slag or sawdust. The main thing is that there is one binder and one filling element.

How to make concrete: proportions

As mentioned earlier, to make concrete with your own hands, you need to know the proportions and be able to apply them. In addition, it is worth having an internal sense of proportion, which comes after several operations with these components, allowing you to determine by eye the consistency of the concrete mixture and its quality. So, what is the proportion, you ask.

It's simple. The main thing is to use a ratio of 1:3:6. What does this mean? In fact, you need to take for every three parts of sand one part of cement and six parts of additional materials. In addition, do not forget about water, which will require one part. Thus, per kilogram of cement you need three kilograms of sand, a liter of water and six kilograms of additives. The amount of water needs to be adjusted: you may need less, depending on the acquisition of a certain consistency.

To make high-quality concrete of a certain brand, you need to pay attention to the quality of cement and sand, as well as the cement grade and class.

We also offer you a detailed table of proportions, which shows the material consumption per 1 m3:

Proportions of concrete with dyes

As already noted, the concrete mixture is not very aesthetic in appearance. At the same time, it is extremely difficult to give it this property. But people came up with the idea of ​​using dyes, which made life much easier.

Coloring pigments are used to color concrete. It is impossible to say for sure in what exact proportions to add them to the concrete mixture. The whole point is that you need to look at the exact shade you want to achieve. It is often more advisable to make your own surface dye from an adhesive, solvent, coloring pigment and strengthening filler.

Concrete can be mixed mechanically, but better quality building material is obtained if you use a special concrete mixer.

To avoid the appearance of lumps when mixing with your own hands, first pour the prepared cement into a dry container. Next, add sand and mix them. Gradually add water and mix thoroughly. And only then we introduce crushed stone.

What are the main additives used?

Don’t forget that properly selected additives will help make the concrete mixture high-quality. In modern construction they are especially common and choosing the right one is not difficult. In doing so, they will add some beneficial characteristics to the concrete mixture.

So let's look at the rest of the DIY concrete additives and the features they add:

• Plasticizers: as the name implies, they make concrete more plastic, which increases the convenience of its laying;
• Hydraulic seals: increase resistance to moisture, which prevents additional excess moisture from entering the bowels of the structure;
• Dust removers: again, everything is clear from the name - eliminates excessive dust, or rather increases resistance to abrasion during operation;
• Accelerators and retarders of hardening: under certain conditions, one or another reaction of the concrete solution may be required;
• Antifreeze additives: this not only increases frost resistance, but also allows you to work with concrete in the cold.

You can see more details about how to mix concrete in the video: