How to mix concrete at home. How to prepare concrete: requirements for materials, proportions and composition calculation. Sand - what happens and what is needed

Concrete is a unique material. It is used not only in construction for the construction of buildings, ranging from the strongest foundation to the complete erection 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 preparing concrete and its processing make it possible to build this material almost on a level with such natural materials as granite or marble. Although it is not aesthetically pleasing like the latter, it is certainly known what it is made of, and there is no obligatory radiation background that natural stones often have. If you decide to abandon purchased concrete, then you should understand how to make concrete with your own hands of the required quality, which will suit the solution of the task and will have sufficient strength and durability.

Although the process of preparing concrete is quite simple, however, 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, we will 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 details about how concrete was evaluated for strength at different times, and we will focus on a modern system used everywhere. The strength of concrete is expressed in mega pascals (MPa), which determines the pressure that a certain class of concrete can withstand. On the basis of 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 crushed stone. The number in the class name indicates the pressure in MPa that the concrete can withstand in 95% of cases.

The simplest version of concrete is a simple mixture of cement mortar and coarse sand. Such concrete is mainly used as a substrate for the foundation. Preparation can be carried out directly at the bottom of the foundation formwork. At the same time, quite a bit of water is added so that the mixture acquires the density of wet soil. In this case, there is no need to talk about strength, but such concrete is excellent as a protection for the main foundation from subsidence and excessive moisture.

More durable concretes involve the use of various crushed stone with a fraction from 2-3 mm to 30-35 mm as a filler. The quality of concrete directly depends on the purity and composition of all its components. So before you deal with the proportions and methods of preparation, in order to make the concrete mortar correctly, it is worth considering each component separately.

Requirements for the components of concrete

Cement

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

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

Portland cement, in addition to good adhesion, is better suited for work at low temperatures. Even so, it is impossible to carry out 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 noted as a grade, there is also the designation "D", after which a number indicating the amount of foreign impurities in the cement is affixed. 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. Never purchase damp or lumpy cement, nor should you over-save and buy unmarked, stale, or discounted cement. Still, concrete will be used to build critical elements of the house, so your well-being and safety depend on it. In unsuitable conditions, cement can very quickly pick up 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 before. Check the labeling and integrity of the package.

Sand

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

Sand suitable for concrete preparation should have a fraction from 1.5 to 5 mm, it is best when it has a uniform size with a run-up of no more than 1-2 mm. The composition of the sand should not contain foreign impurities. All kinds of plant residues, construction debris and any inclusions that can decay or rot over time will adversely affect the strength of concrete. For reliability, if the sand is not completely clean, it is better to pass it through a sieve with sufficiently small cells. Actually, the same applies to rubble.

River sand is best suited, although it is more expensive than ravine sand, it has a suitable grain size and does not contain silt inclusions and 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 for concrete preparation at all, because it is very difficult to get rid of them. For this, the procedure for washing and settling sand is used, which, even in industrial conditions, is not always profitable and easy.

Alternatively, for places near which there are stone quarries, artificial heavy sand can be used. It is obtained as a result of crushing rocks, it has a greater mass and density. If it is normally washed and sifted by particle size, then it will be even somewhat better than river sand. It is only important to take into account during preparation and use that the concrete will turn out to be much heavier, this is important if it is used in the installation of screeds on top of interfloor ceilings. A significant obstacle to the use of heavy artificial sand may be perhaps an increased radiation background, which depends on that of the parent rock.

Aggregate. Crushed stone, gravel

It is the filling with gravel or crushed stone that gives the main strength to concrete. Sea or river pebbles are by no means suitable, because their surface is polished with water and does not provide proper adhesion to the solution. The material obtained just from crushed rock is best suited.

It is also important to take into account the characteristics of the breed that was used in this case. 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 choose the right material for the preparation of 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 for the most part in production, and even then rarely. As with sand, it is desirable that the aggregate contain as little dust or clay inclusions as possible on its surface. Debris must be removed before the gravel enters the solution. The higher the roughness on the particle faces, the better. A reliable grip depends on this.

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

Both sand and crushed stone or gravel, for storage, it is better to store in bulk near the place of use. In order to prevent material contamination and soil moisture, it is best to place the mounds on a spread tarp or area with a solid base. In the simplest case, when materials are poured directly onto the soil, the lowest layer that comes into contact with it should not be used.

Water

The choice of 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 impurities. You can not use river or even more so lake water, in which there are more than enough inclusions. It is best to follow a simple rule: water that is drinkable is also suitable for making strong and good concrete at home. Only if this rule is observed, it can be expected that the concrete will be strong and will lie for a long time without any damage or destruction.

Additives

• Lime. Some masters 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 the cast section of the porch or outlet. And yet, in addition to this, lime can place a normal bond of cement with aggregate, which will affect strength. The choice whether to resort to the use of lime or not already remains with the master, when he knows exactly what is best at the moment. Lime has long been no longer necessary to extinguish on its own. Instead, ready-made slaked lime is used, which is sold in hardware stores and is called fluff.
• plasticizers. To make the concrete mortar more fluid or vice versa, various plasticizers are used, which change the properties of the mortar 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 dense enough 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 also be used to impart more progressive properties to concrete. Thus, additives can be used to ensure the setting and hardening of concrete at low temperatures or in the presence of a large amount of moisture. Appropriate additives are used for various purposes. It is important to decide on the need to use them and choose the necessary additive in a hardware store. Carefully study the instructions for use and the properties of the additive. If the conditions under which the concrete will be used have boundary parameters for temperature or humidity, then additives and plasticizers will be indispensable.
• reinforcing substances. In addition to concrete aggregates, specific additives are also often used for additional reinforcement. So when using concrete, a special polypropylene or polyvinyl chloride fiber is used to make a rather thin screed. It is in itself soft and not particularly strong, but it will help to avoid situations where the concrete cracks at the convergence of floor slabs or, in the case of an unstable base, when forming the main floor over soils.

Selection of ratios of materials for the preparation of concrete

For different purposes, a different composition of concrete is required. So, to form a foundation for a house, strong concrete is required with the inclusion of large crushed stone with elements ranging in size from 20 to 35 mm, and the amount of mortar is a sufficient proportion of the filler to be fixed. In this case, the solution must be fluid, because it is required to firmly compact the concrete and remove all air bubbles from it. However, before pouring the main part of the concrete, the substrate must be equipped. For this, the simplest in preparation and less durable concrete B7.5 is used, in which, in addition to the cement mortar, only coarse sand can be present. Moreover, for this, the concrete solution is not made liquid, but more like wet soil in consistency.

For the installation of foundations, an average-sized aggregate fraction and still a liquid solution will be required. This will ensure the ease of spreading the solution over the surface with a sufficiently thin layer. Also, the fine and medium fraction of the aggregate is indispensable in the formation of such elements as balusters, decorative elements or garden utensils and pouring, elements of insignificant volume, 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, the planned preparation and pouring of concrete can begin.

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, most often adhering to such a layout, an unsatisfactory result of concrete is obtained, and this will be visible only after a while, when it will be quite difficult to fix something. It is best, in accordance with the presented regulatory documents, to perform a simple, in fact, calculation and protect yourself from unpleasant consequences. All this is due to the fact that both aggregate and sand, as well as cement, can vary significantly in density parameters and binding characteristics.

After the calculations, you should decide on a practical way to measure the ingredients. After all, now only volumetric and weight parameters are on hand, and they are somewhat incompatible with those in a real situation. The same sand may be sufficiently wet or excessively loose that a 10 liter bucket will contain far less than what a density-to-volume ratio would suggest.

In terms of humidity of the same sand and gravel, it is better to dry them than to try to roughly calculate the number of servings of one or another ingredient. And to determine the friability and excretion of portions, it is enough to weigh the portions of each ingredient in relation to one volume. That is, a bucket or other convenient container is taken and filled without tamping with sand, cement and aggregate in turn, and the resulting portion is weighed. Further, by simple calculations, it will be possible to translate the previously obtained calculations into the ratio of buckets.

With what and where to mix concrete?

Whatever one may say, it is best to use specially designed concrete mixers for mixing concrete. This is the only way to quickly and efficiently mix all the components and deliver the concrete to its destination before it starts to set and delaminate. The old-fashioned manual method in a tub is not particularly suitable for more or less large volumes. At the same time, there is no way to control the mixing and adding of ingredients so that it happens according to the recipe. The last statement requires clarification. Indeed, many do not understand how, if everything is done by hand and under constant supervision, one can violate the recipe and spoil the concrete.

Everything is very simple. There are two options for making concrete with your own hands:

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

With dry mixing, the materials seem to be distributed evenly, however, with the addition of 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 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 delaminate. This will not affect the appearance, but the strength - yes. If everything is added to the water, again, the cement will be kneaded too long and will not be able to properly bond with the aggregates afterwards. The second option is at least a little, but better than the first, so this is how concrete should be kneaded in small quantities.

So, the hand kneading option is not particularly good. It is still better to rent a concrete mixer, or purchase and knead 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 not allow the concrete to exfoliate during transportation and mixing. All ingredients must also be nearby or at least delivered in parts to the concrete mixer.

concrete mixing

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

• The required amount of water is poured. Approximately 10-15% can be left to add later. This will facilitate mixing after all materials have been added.
• The cement is being laid. If water was left, then the same amount of cement should be set aside.
• Sand is added next. Stir at this stage until all components 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, reinforcing compounds.
• Lastly, the main aggregate (gravel, crushed stone) is filled up. If it is necessary to add water, then water is first mixed with cement and then only the resulting cement milk is poured into the concrete mixer.

The entire process should take approximately 10 minutes. If stirred too long, the cement in the mortar may begin to set.

The solution is transported by wheelbarrow. If the entire mixture does not fit in a wheelbarrow, then the remaining solution remains in the included concrete mixer and is mixed.

Video: manual concrete mixing

Pouring concrete

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

Vibration is used for the task at hand. The use of specialized vibrators allows you to compact concrete quickly and efficiently. For foundations and walls, a special tool is used, which has a vibrating hose. It is immersed in a solution, and thus tamping occurs. For thin layers, such as screed, surface units are used, which have a long rail. Under the action 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 pointed rebar and pierce the solution to the full depth. This releases all the air that could be stuck in the reinforcement mesh and in the mortar itself. Since the pouring is carried out gradually, even when piercing a new portion of concrete, one should go at least 10 cm deep into the previous layer for their reliable fastening.

As a result of the described actions, the concrete aggregate should be tightly compacted, and an even layer of mortar should come out 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 the foundation, it is necessary to create vibration. To do this, uniform blows are applied to the sides of the formwork with a sledgehammer. You should not beat on the boards of the shields, but on the bars that hold them together.

For uniform drying and protection of concrete from external factors, it is necessary to cover it with a film. This will not allow the concrete surface to dry too quickly ahead of the inside and will protect against external factors such as sun, heat, cold, etc.

Approximate drying time for concrete to a state where you can safely step on it is 36 hours. Everything naturally depends on the thickness of the layer. Complete drying can take up to a week or two. Concrete, in fact, even after that, will completely dry and harden within six months. Maximum strength will be achieved only after more than a year. Further work can be carried out in a week.

Video: concrete pouring features

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Discussion:

Gosha said:

When preparing concrete, it is important to know for what purpose this concrete will be prepared! Foundation, walkway, etc. Or what else?
And so 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 gravel or gravel.
In appearance, the solution should look like a thick gray “fatty” sour cream. If the solution looks a little darker (blacker), but in general, crushed stone with sand “floats” separately from water and is weakly “connected” with each other, then it means a) either there is a lot of water, or b) there is LITTLE cement!
Then you need to add more cement, until again the solution seems to you 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 solution. Without it, everything else will not “knit” and “stick” with each other!
.

Concrete is the main material that provides strength to the house. The construction of the foundation, walls, floors, floors requires a concrete solution. In private construction, it is unprofitable to order concrete in small portions, large-scale volumes are needed for large-scale construction. The time interval for using the material is small, it must be consumed quickly. You can easily make concrete with your own hands. Consider how to prepare concrete at home.

Main components

Despite the fact that the preparation process is simple, it is rather difficult to withstand a number of features while maintaining the quality of the solution. Concrete is a mixture of binder and fillers. The main components are:

• cement;
• sand;
• fillers.

The classic option is cement-sand mortar. The scope of its use is rather narrow, the strength is low, but as a protective layer against subsidence of buildings, it fits perfectly.

Component Requirements

Modern production of materials makes it possible to combine special additives, plasticizers in the solution, which give concrete exceptional characteristics. The composition of the solution includes a binder, sand, gravel, additives, water. Let's dwell on each in more detail.

The main and only binding ingredient in the solution is cement. For best results, Portland cement is best. Its differences lie in the increased content of calcium silicate, which ensures a strong connection of the components. Other types of mineral powder are used, it all depends on the goals and objectives. More suitable - m500, the use of m400 is acceptable, but the structures will turn out to be less durable, which will have a bad effect on the duration of operation.

The mineral element must be used in a dry, loose form. A damp, lumpy appearance of the powder is unacceptable. Poor storage conditions for an important component contribute to the loss of a significant part of the technical characteristics.

Modern marking includes an indicator marked with the letter "D", the number next to which shows the amount of impurities in the composition of cement. The maximum amount corresponds to 20%.

Sand

The sand fractions included in the solution have a size of 1.5 to 5 mm. An excellent result is given by the coincidence of fractions, the maximum discrepancy is within 2 mm. The content of impurities in the composition of the bulk element is unacceptable: dirt, dust, debris. To make sure the sand is clean, you need to sift it. The ideal option is river sand, with a suitable fraction size, without clay impurities.

rubble

It is the aggregate that gives the cement mortar the necessary strength. Crushed rock is ideal: gravel, crushed stone. The best strength result is given by aggregates of different sizes: large and small. Different sizes ensure that the components fit tightly to each other, preventing the formation of voids.

Gravel cleanliness is very important. In order to prevent contamination, the aggregate on the ground is located on a pre-laid tarpaulin, a film.

Water

At first glance, a simple component - water, should not contain acidic, alkaline compounds. The use of lake, river water is unacceptable. A strong concrete solution can make clear, clean water.

Additives

Depending on the natural conditions of construction, engineering tasks, lime, plasticizers, auxiliary and reinforcing substances are added to the solution during preparation. They improve adhesion, give elasticity, reduce the percentage of cracking.

The right ratio of materials

The purpose of construction determines the correct composition of the solution. For example, the foundation of a building requires a strong, fluid solution with the presence of large fractions. However, before pouring the main mass, it is definitely worth endowing the surface of the base with technical properties, using a simple composition of the solution. The composition includes cement and sand. By consistency, it is much less common than the composition for the foundation.

The structure and percentage of components in concrete is maintained in accordance with building standards, taking into account the density of all components. It is better to measure portions of the components yourself, it is important to follow an equal amount of a set of materials.

The amount of water depends on the desired consistency of the solution. It is important to remember that a lot of water will reduce the strength, a little water will have a bad effect on the condition of the concrete. The correct ratio of water to mineral powder is 5 to 10. The amount of water is 50% by weight of the powder.

The percentage of components, according to the popular grades of the mineral substance, is as follows (cement/sand/aggregate):

• M300 - 1:2.4:4.3;
• M 400 - 1:1.6:3.2;
• M 500 - 1: 1.4: 2.9.

The presence of additives is not included in the percentage, their amount is affected by the purpose and condition of use. Paying attention to the quality of the components, the correct proportions, the technology of preparation, you will get exactly the brand of binder that is needed.

Cooking process

How to make concrete with your own hands? What to mix it with? From the required amount of solution, the kneading method will be selected. There are two options: manual and mechanical.

Manual way

How to prepare concrete at home if the construction plans do not include the cost of a concrete mixer? There is an old bathtub, a shovel, you can use your own hands. This method is not suitable for large volumes, it is indispensable for small volumes. There are two ways to make a solution:

• First. Sand, cement are mixed in dry form, after which water is added, the remaining components. Materials are distributed evenly, but the procedure for adding water should be given special attention. There is a possibility that some of the dry ingredients may remain at the bottom, not get into the solution, violating the percentage. Thoroughly, but not for long, mix the components, do not allow the concrete to harden. Such trifles will not be displayed on the external characteristics of the solution; for technical characteristics, these are not trifles, but the danger of losing strength.
• Second. The required amount of water is measured, cement, sand, aggregate and additives are added. The second method is better than the first combined with a small amount of concrete. Feel free to use it yourself.

Concrete is one of the modern materials that are used to create strong and durable structures. It consists of sand, some fillers and a binder. When the concrete mortar completely hardens, it becomes a stone. It is impossible to imagine any construction event in which concrete would not be used.

However, the material must meet certain requirements. Only in this case it is possible to build a solid structure from it that will last for more than a dozen years. To make the material as durable as possible, it should be made using a special technology. The proportions of concrete for the foundation of various structures are selected in accordance with the strength requirements for the structure.

Cement

Cement always acts as a binder when creating a concrete mix. It is made in different variations. The choice of a particular brand of cement depends on the final destination of the concrete product and the conditions for its use. The quality of binding is one of the main characteristics of cement.

When choosing cement, it is important to consider its technical data. They affect the maximum load that the finished product can experience. This indicator is measured in megapascals. When designating a brand of a domestic product, the letter D (impurities) is added. For example, if M400-D20 is written on the bag, then a concrete product made from such cement will withstand a load of up to 400 MPa, and the percentage of impurities in the powder is 20%.

For domestic purposes, Portland cement grade 400 is often used. It has good strength and is suitable for low-rise construction. For industrial purposes, cement grades from 500 are chosen. When erecting structures that will experience serious loads, cement powder of a higher grade should be chosen.

Cement powder has such a characteristic as an expiration date. After a certain time, the material begins to lose its useful properties. If the cement is fresh, it is friable, does not have seals and lumps. When various seals are in the powder, cement should not be used in the work. Such a powder has already absorbed a certain amount of moisture, which is reflected in its binding properties.

Sand selection

Sand can have different characteristics. The strength of the final result will depend on how well it is selected. During the preparation of concrete mortar, different types of sand are used. One of the main conditions is the absence of dust or clay particles in it. If there are quite a lot of such inclusions, the mixture will turn out to be of low quality. This can be especially attributed to fine sand, which contains a high percentage of dust particles. It cannot be used to make concrete.

How not to miscalculate when choosing sand? After all, only when choosing a quality material can you make the most durable concrete. It is better to choose river or sea sand. He is the purest. Quarry sand should not be used to create a concrete mixture without prior cleaning. Usually it contains a lot of tree roots, leaves and bark. Quarry sand must be washed and settled.

If any organic inclusions get into the concrete, it will lose a certain percentage of strength. This is due to the formation of voids in the finished solution when mixing concrete with dirty sand.

Another important factor is the moisture percentage of the sand. Even if the material is dry, it can contain up to 2% water, in wet sand up to 10%. If you use too wet sand for the mixture, the strength of the finished product will be significantly reduced. The exact proportions for the preparation of concrete are selected in accordance with the requirements for the final result. The differences between concrete of different grades are analyzed in the table:

gravel and crushed stone

Gravel and crushed stone are often among the main fillers for concrete. This material is a rock that is crushed to a certain size. It can be classified according to the size of individual elements. Crushed stone can have a rough or smooth texture.

Crushed stone can be:

• very small - individual components have a size of 3 to 10 mm;
• small - stones differ in diameter of 10-20 mm;
• medium - such crushed stone has a size of 20 to 40 mm;
• large crushed stone differs in diameter of 40-70 mm.

To make concrete that will last for many years, it is necessary to choose such crushed stone so that the size of its individual parts is no more than 1/3 of the thickness of the finished product.

In addition, it is important to take into account another indicator - the voidness of the filler. It is determined by the amount of empty space between the stones. It is quite easy to define it. To do this, you need to fill a 10-liter bucket with crushed stone and see how much water is needed to fill the remaining space. When using 3 liters of water, we can say that the voidness of the filler is 30%.

This indicator affects the amount of sand and cement that will be used to create concrete. The smaller the void, the less other components will have to be used to create a mixture.

To fill the voids as much as possible, crushed stone of different fractions is used. Stones are taken as small, as large and medium in size. It should be borne in mind that the elements of the fine fraction must be used at least 1.3 of the total amount of crushed stone.

In addition to gravel and crushed granite, depending on the purpose of using the concrete product, expanded clay and blast-furnace slag are used. Other fillers may also be used. If lightweight concrete is being prepared, wood shavings are chosen as the filler. When creating ultralight types of concrete, gases are the filler. However, in the manufacture of such concretes, certain requirements must be observed. Otherwise, the finished product will not meet standard standards. Table of general requirements for concrete:

Fillers for concrete mixes can be dense or hollow. Natural materials have a lower radiation background than artificial ones. Granite rocks have the lowest index. However, finished products with any fillers will not be sources of radioactive contamination, so this indicator is often not taken into account.

Water

Water is one of the most important components of the solution, which must also meet certain requirements. If the water quality is poor, it will adversely affect the strength of the concrete product. The main rule in the manufacture of the mixture can be considered such a condition - if water can be used for cooking, it is also suitable for mixing the concrete mixture. It is not recommended to use swamp water.

Each element of the solution has a certain moisture index. Moisture that is present in building materials is excess water that can spoil the finished concrete mix. To figure out how to prepare concrete, you will need to determine the necessary properties of the finished product.

The volume of water used affects such an indicator as the ductility of concrete. The plasticity of the solution is usually determined "by eye".

To determine this indicator, you should take the solution on a shovel. If it slides off a horizontally placed tool, it has high ductility. When concrete slips in the case of a slight inclination of the shovel, it can be considered medium-plastic. Concrete has low plasticity, which will not roll, even if the shovel is strongly tilted.

Strength set

Concrete acquires a certain strength only after a certain time. After a week, the finished material gains a certain strength (up to 40%). However, only within 28 days from the date of pouring concrete can become as strong as possible. Special requirements for this indicator are imposed when creating concrete for the foundation.

The calculation of the composition of concrete must be carried out taking into account certain data. Among them should be highlighted:

• brand of cement powder;
• characteristics of the granulometric composition of crushed stone and sand;
• plasticity of concrete to be achieved;
• required brand of ready-made concrete.

The composition of concrete can be calculated by the mass of its components or their volume. Cement is always taken as a unit. Other components of concrete are calculated as a certain part of the volume of cement. Determine which proportions of concrete to choose for the foundation should be according to the required indicator of the brand of the finished product.

Calculation by weight

The calculation of the composition can be carried out according to certain standards. The main goal is to obtain a solution of medium plasticity.

At the beginning of work, it is necessary to determine what the water-cement ratio will be. For this, the W / C indicator is determined. It represents the ratio of water and cement. The determination of such a characteristic is carried out empirically or according to a special table.

To measure the amount of materials that make up concrete, a 10-liter bucket is usually used. It is used as a measuring vessel. For ease of calculation, it should be mentioned how much a 10-liter bucket contains certain materials:

• about 13-15 kg of cement powder;
• from 14 to 17 kg of sand - this figure depends on the percentage of moisture in the material;

It should be understood that the methodology for such a calculation is somewhat inferior to the methods used by professional builders. However, this method is still good for domestic purposes. In addition to using proportions by weight, proportions of the composition of the mixture according to volume are also used. This method is less accurate.

Proper concrete mixing

Concrete can also be kneaded by hand, but mixers or concrete mixers are more often used for such work. In the first case, the finished mixture is obtained in a small volume. To properly knead the solution, you need a container of a certain volume. Usually a tin trough is chosen for this purpose.

The proportions for the preparation of concrete of medium plasticity grade M400 should be as follows:

• cement - 1 part;
• crushed stone - 2.7 parts;
• sand - 1.2 parts.

With 10 liters of cement, 31 liters of water must be used. Manual mixing is the most popular when creating concrete products in home gardens. The number of components used can be calculated using the table:

Preparing concrete by hand is quite simple. Sand is poured into the trough. Then a strip is drawn in it in the middle. Cement is poured into the groove. Then these ingredients must be thoroughly mixed. After that, crushed stone is added. The resulting mixture is kneaded until each stone is covered with a solution. At the same time, water should be added a little at a time. Its quantity regulates the plasticity of concrete. When the mixture is homogeneous, the concrete can be poured.

During manual mixing, it is important to pour the finished solution as quickly as possible. If there is a momentary delay, the concrete will begin to delaminate. In this case, water begins to appear from above the solution. It is better to mix concrete in a concrete mixer.

Using a concrete mixer

When using a concrete mixer, cement powder is first poured into the device and water is poured. Then you need to add sand. Then the solution should be kneaded, adding water along the way. When a homogeneous solution is obtained, filler is poured into it.

The advantage of this method is that the concrete will not delaminate. It can be in the mixer for about 1 hour without losing its properties. The device should not be placed far from the place where the concrete is to be poured. This condition must be observed so that the concrete does not lose its properties during delivery to the place of laying. If you follow these simple rules, you can get a reliable and durable design.

In private construction, the foundation is usually poured on their own, without ordering kilotons of concrete in a mixer. Because imported concrete is much more expensive, given the small volumes. If, for example, you pour a strip foundation for a garage or a masonry fence, the cost of a mixer will not be justified in any way. Therefore, in such cases, concrete is prepared with a hand-made shovel in a convenient, sweet trough. If, of course, they know the proportions and technologies ...

Composition and material

Concrete is not a masonry mortar, so the presence of aggregate must be taken into account. The composition will certainly include crushed stone or other crushed material, small red brick breakage, gravel. The ratio of materials is taken depending on the purpose and the required brand of concrete. The more irregularities on the surface of the aggregate, the better its adhesion coefficient. Pellets (river gravel) are not suitable for concrete preparation!

Sand is better to take medium-grained, mined in quarries, and not washed along the banks of rivers. River sand, in addition to having a fine fraction, also contains a large percentage of clay particles, which is an aspect that worsens performance for high-quality concrete.

It is optimal to choose crushed stone or another type of aggregate with a fraction of 5-20 for pouring the formwork or 20-40 for pouring the foundation “on the ground”.

Lightweight concretes (containing a minimum of gravel, granite or other heavy crushed stone) are not suitable for pouring the foundation. The same applies to the masonry mortar prepared according to the technology without aggregates at all.

The standard ratio of cement / sand / crushed stone for concrete grade M200 and cement grade M400 is 1 / 2.8 / 4.8 (proportions are indicated by weight, not by volume). To prepare M250 concrete from the same grade of cement, you will need to mix the solution in proportions by weight of 1 / 2.1 / 3.9. To prepare M300 concrete, mix the components in a ratio of 1 / 1.9 / 3.7.

Pay attention to the mixing method! This is not a masonry mortar, and mixing all the ingredients before adding water will be very problematic, unless you had a worthy nickname "excavator" in your childhood. Therefore, first mix the sand and cement, as in a normal mortar, and gradually add water and crushed stone, achieving the desired consistency in the end result. It should be noted that in order to fill a strip foundation without formwork, “in the ground” to the level of the upper soil layer, a more liquid consistency is always prepared.

So, you will need materials:

cement brand M400 or M500;

river or quarry sand;

aggregate;

additives, hardeners, additives, softeners and others - only with the subsequent use of the prepared concrete in non-standard conditions (high humidity, constant rain, air temperature less than + 5 ℃, the need to quickly load a freshly poured foundation and other circumstances).

Prepare your tools:

electric or manual concrete mixer;

large capacity (trough) for manual stirring;

10-12-liter bucket for transporting components, water;

shovel;

the sieve is capacious enough for sifting sand from weeds. "Handicraftsmen" often use a metal mesh from an old spring bed set at an angle of 45 ° and above.

It is worth noting that the purchase of a concrete mixer for one-time use is also unprofitable, as in the case of ordering a mixer with ready-made concrete for small volumes of construction. The foundation for an ordinary garage will be much cheaper to prepare in the “old-fashioned” way, stirring the components in a trough. It will take a little more time. Proven by time and billions of private developers.

Construction technologies used in everyday life provide for the formation of a concrete solution directly at the construction site. Making concrete for the foundation with your own hands is not a particularly difficult task.

Most often, domestic construction work is carried out precisely in the use of self-made concrete solutions. The formation of a concrete mixture of proper quality provides for the presence of the following components: aggregate, cement, lime, additives, water.

Aggregate concrete

The manufacture of mortar for construction purposes most often involves the use of fine sand or crushed stone. It is also possible to use large crushed stone or gravel. The preparation of mortar for plastering or masonry work is carried out using fine sand. Stucco with a special, non-smooth texture can be made from coarser sand.

As a rule, the sand offered by manufacturers is of river or ravine origin. The first is considered medium-grained. Its cost is high, but the quality matches. The second type of sand can be fine-grained, but the presence of impurities and clay particles in its composition makes it not the best choice for making good concrete, but mortars can be made with such material.

The manufacture of high quality lightweight concrete mortar involves the use of sand exclusively as a filler. Gravel and crushed stone are used to make stronger concrete.

The best option is a combination of a mixture of crushed stone of different fractions, such a composition contributes to the formation of a minimum number of voids. All kinds of contaminants such as soil, glass, peat and plants are unacceptable in the composition of the solution.

Cement - characteristics

Such a common name is given to substances of a powdery texture, made on the basis of clay and calcareous rocks with the use of various additives to them.

The most applicable is Portland cement. This type of material contains a large amount of calcium silicates. There are two types of this substance:

• Type 1 - the content of additives does not exceed 5%;
• Type 2 - additives reach 35% in the composition.

Domestic cement is marked with the letter D, to indicate the presence and amount of additives in its composition. For example, the inscription on the packaging PC 300-D20 informs the buyer about the presence of 20% additives in this product.

When buying cement, you should check for proper labeling on the package, as well as check the absence of moisture in the package itself.

As a rule, this can be understood in appearance or simply felt with your hands. Stale cement is not the best purchase for construction repairs or work.

Lime - why is it?

Lime can improve the properties of the solution and ensure its high-quality laying. Previously, it was required to “extinguish” it before adding it to the solution. Now slaked lime (fluff) packed in bags is available for sale. You can use both a dry mix and a water-based lime paste. Lime is added to make plaster or masonry mortars.

When working with lime mortars, it is necessary to observe safety precautions:

• wear protective gloves and avoid getting lime on your skin or eyes. This composition has strong corrosive properties. In case of contact, rinse with water.

Additives - nuances of application

To improve or improve the properties of the cement mortar, additional additives are included in its composition.

• plasticizers. They improve the flow properties of concrete. The use of such substances allows you to create concrete structures of various shapes and generally improves the laying properties of concrete.
• Superplasticizers or thinning additives help reduce water in the solution. Also, such elements make the concrete structure frost-resistant and waterproof;
• additives that promote rapid hardening;
• additives that allow working with concrete at temperatures from -10 to +35 degrees;
• Aerating or air-entraining components. Serve to increase resistance to frost and reduce the moisture content in the finished product;

You can buy additives at a hardware store, checking for dosage information on the package. They are sold already in finished liquid form, adding them to the solution should not exceed 2% of the total mass.

In some cases, additives can be made independently. For example, the manufacture of plasticizers from soap or soap solutions is common.

Compliance with the dosage when using such substances is of key importance, a violation of the proportion can lead to a decrease in the quality of the solution.

And, of course, water for concrete mix

The choice of water for the preparation of a mixture of concrete must be carried out in accordance with GOST. Water requirements include the absence of impurities, sugars, oils or acids.

It is recommended not to use water from dubious sources, such as a lake or river, but to take a liquid suitable for drinking. If, nevertheless, it is planned to use water from a reservoir, then it is better to check its suitability in a special laboratory.

Proportions and composition of the solution

Parameters such as the composition of the concrete mixture and the proportions of the components used depend on the purpose of this solution. When making concrete for the foundation with your own hands, it is better to take high-density concrete, which has sufficient strength.

• The manufacture of elements such as the base for the fence can be made of concrete of a lighter grade. It is better if the concrete for self-production of the mixture corresponds to the M300 or M400 grades.
• The proportions of the components necessary for the manufacture of high-quality mortar: 1 part of cement, 3 parts of sand and 5 parts of crushed stone. The weight of the added water should be half the weight of the dry mixture.
• Components can be added during mixing. When forming a solution of too thick consistency, you can add water.
• The use of wet sand requires less fluid to be added.
• The consistency of the solution should be such that mixing it with a shovel is not carried out with excessive effort.
• Works with concrete, performed in conditions of negative temperature, should be carried out with heating of the material itself and water. If this condition is not met, then premature solidification of the mixture is possible and, as a result, a violation of construction technology.
• It is better to mix the components in a purchased concrete mixer, but it is also possible to use home-made devices.

The implementation of recommendations for the manufacture of concrete contributes to the improvement of the quality of work performed. The right choice of material brand, components and additives will allow you to create a solution that is optimal for the implementation of each specific task.

Be sure to observe safety precautions in the process of work, as well as the use of high-quality tools and devices.

It is quite difficult to exaggerate the importance of concrete in modern construction. It is used at various stages of building construction, starting with the creation of the foundation, ending with the final decorative work on the design of the landscape of the green zone near the house.

According to its physical properties, concrete is an artificial stone made from a certain set of components.

What is concrete made of?

All components are divided into four groups in accordance with the principle of operation of the component:

• astringent base
• mixing liquid
• aggregate
• additional substances.

Important! The materials of the last category are used mainly when laying concrete in difficult conditions or at the request of the manufacturer.

What are the main ingredients of the solution?

To create a concrete mix, prepare:

• Cement
• Rubble.

Important! A wide range of dry concrete mixes is presented on the building materials market, which are enough to be diluted with water exactly according to the instructions. But, making concrete with your own hands, with the right components, is also not difficult.

In the process of choosing a finished building mixture, be attentive to the presence of specific additives. Some of them affect frost resistance, hardening rate, degree of plasticity of concrete.

Criteria for the selection of concrete components

Water

In production processes, for the preparation of concrete mix, water is used, the composition indicators of which comply with GOST standards. When making your own, prepare drinking water.

Important! Check the quality of the water, it should be free of alkalis, sugar, oils, acids and other impurities.

Cement

The general name of the binder, which is based on marl, calcareous, clay rocks. Most often today, Portland cement is used in construction, with a high percentage of calcium silicates in the composition.

Cement classification:

• Without additives, that is, their content in the composition does not exceed 5%. Marking "TO" or "CEM I".
• With additives, the percentage of which varies within 35. Marking D + Indicator of the content of additives in percent, for example, "D15" or "CEM II".

When buying, pay attention to the following nuances:

• admissible period of use of the mixture
• storage conditions
• make sure that the moisture level is correct, that is, that the cement is not damp
• check the flowability of the substance (it should not be stale, compressed)
• make sure each bag is labeled accordingly
• the grade of cement should exceed the grade of the planned concrete (see below) by 2-3 times.

Important! Do not buy cement too early, enough for 1-2 weeks. If the terms and conditions of storage are not observed, it loses its quality, which will affect the strength characteristics of concrete.

The choice of sand has its own conditions and requires the right approach.

Pay attention to the following points:

1. Granule size. There are several types, the size range of which varies from 1.2 to 3.5 mm. Give preference to coarse sand.
   

   Important! Please note that the smaller the granules, the greater the consumption of sand in the manufacture of the concrete mixture and the lower the strength of the finished hardened composition.

2. The purity of the substance. Use the cleanest material without impurities and dirt (plant particles, silt, clay, glass, soil, dust). Check for their presence by sifting or washing the sand.
   

   Important! This criterion affects setting degree, consumption of cement for the preparation of concrete and water.

3. Flowability. The sand should be well dried, not wet, since the recipes indicate the amount of dry matter.

Important! In any state of sand, there is a certain percentage of absorbed moisture in it, which is usually taken into account when compiling the proportions of substances. In dry - this figure does not exceed 1%.

rubble

Pay attention to the following criteria:

Important! Please note that most often it is the quality of crushed stone that affects the strength of concrete.

Expanded clay

This material does not belong to the main components of concrete, but to create a lightweight solution (to reduce the load on the floors and frame of the structure), expanded clay is often used instead of crushed stone.

When choosing this material, pay attention to:

• fraction size — from 3 to 5 mm
• flowability of a substance
• purity and uniformity.

Concrete marking

The classification of concrete is carried out according to:

• class (B)
• brand (M).

The brand of concrete indicates the compressive strength and load capacity. The indicators vary from 50 to 1000 kgf / cm2. That is, for example, M300 concrete can withstand up to 300 kg / cm2.
The mortar class indicates guaranteed strength in 95 cases out of 100. The range of indicators is from 3.5 to 80.

Plan the specific type of mixture based on the purpose.

The table below shows the acceptable grades and classes of concrete with strength indicators.

How to prepare a concrete solution?

You can prepare the mixture yourself in two ways:

• manual
• mechanical (using a concrete mixer).

The first will, of course, be more laborious, but, with a small amount of work, it is quite acceptable and economical.

Use a concrete mixer for large volumes or increased requirements for the strength characteristics of the concrete mixture.

Preparatory work

Preliminary work is necessary regardless of the further method of preparing the solution. They consist in the preparation of materials.
Sequencing:

1. Sift the sand.
2. Wash gravel.
3. Dry both substances.

Norms for the preparation of concrete

In order to get concrete of a certain brand and strength, follow the recipe.
Choose the most convenient principle for calculating the consumption of components:

• kilograms
• liters
• percentage
• number of parts.

Carefully consider the tables below, which indicate the various possible proportions for the preparation of concrete.

Important! Please note that in each individual case, deviations from the norm are permissible, which are regulated by the quality of the materials.

Cooking conditions

When preparing concrete on your own, be sure to observe not only the technical aspects of the process, but also the conditions under which the solution is produced:

• air temperature 15-20
• humidity level within 90%.

Important! If pouring is carried out in conditions of severe aridity or low temperatures, use special additives that regulate the solidification process, thermal insulation materials and additional irrigation.

Manual method for making mortar

The procedure for preparing concrete:

Mechanical concrete preparation

Types of concrete mixers

There are two types of concrete mixers:

• gravitational
• coercive action.

In the first case, mixing occurs due to the rotation of the drum with fixed blades installed inside it. In the second, mixing is performed by blades rotating in a certain mode with a stationary bucket.

Each type has its own advantages:

• compactness, light weight, low cost are inherent in gravitational devices
• get a better mixing quality when using a forced-type concrete mixer.

Important! For self-preparation of concrete at home, a gravitational apparatus is quite enough. Please also note that with a very large amount of work, you will most likely need not one, but 2-3 concrete mixers.

How to prepare high-quality concrete?

In the process of preparing concrete in a concrete mixer, an important factor is the sequence of loading the components. The quality of the prepared mixture directly depends on how correctly the technology is chosen.

There are many opinions on this matter. Below is a technology for a more rational approach to doing this work.

Cooking technology

1. Place the concrete mixer on a level surface.
   
2. If necessary, create additional underlays to increase the stability of the machine.
3. Lubricate the blades and walls of the concrete mixer with a mixture of water, cement and fine aggregate.
   

   Important! This action will prevent the solution from sticking.

4. Turn on the machine.
5. Pour in half of the prepared water.
6. Pour crushed stone into the drum - half of the total volume.
   
7. Wait 2-3 minutes for mixing.
8. Add cement.
   

   Important! When supplying cement after crushed stone, larger aggregate fractions prevent cement from sticking to the walls and blades. Plus, crushed stone helps to break up the resulting lumps.
   

9. Wait for some mixing time (about 3-5 minutes).
10. Add sand.
    
11. Leave to stir for 2-3 minutes.
12. Add the remaining gravel.
13. In the process of mixing, pour in the rest of the water, bringing the solution to the desired consistency.
    

    Important! After adding all the components, rotation for more than 2-3 minutes is not recommended. This can lead to loss of plasticity, delamination and water evaporation.
    

14. Switch off the unit.
    

    Important! Observe the following safety precautions during all work:

    • do not stick your hands and shovel inside when rotating

    • wear protective gloves

    • do not lean close to the drum.

15. Pour a small portion of the prepared mixture into a wheelbarrow.
16. Check the quality of the concrete.
    

    Important! One way to check the quality of the mortar is to make a few ribs with a shovel. If the concrete is of the right consistency, they will retain their shape. But, at the same time, the mixture should be fluid.

17. Unload into a container if the desired plasticity is achieved.
    
18. Pour the mixture back and mix again if the concrete is not ready, then unload into a container.
19. Wash the concrete mixer.
    

Important! Consider the allowable mixing volume of the particular apparatus you have chosen. The main criterion is a large aggregate, which, if excessive, interferes with making a full-fledged batch of the proper level. For example, for a concrete mixer with a capacity of 132 liters, the maximum amount of crushed stone in one preparation is 4 buckets.

Video of concrete mix preparation

Conclusion

Ready-mix concrete can be used for a limited period, so calculate your actions and time to avoid long-term storage of the mass and premature drying of the solution. This will lead to a decrease in the initial quality, and, accordingly, will affect the strength during operation.