Preparation of concrete mixture for walls. Proportions of concrete of different grades: M200, M250, M300 and M500
After reading this article, you will learn about how to make good concrete with your own hands, what characteristics good concrete should have, what is included in the composition and in what proportion, the advantages of manual and mechanical technology for mixing concrete and pouring it. Pouring concrete at positive temperatures is easier than.
Concrete is often called the main building material. Foundations, walls, roofs, screeds, cladding, paving slabs, balusters, vases - unlike granite or marble, concrete is easy to make yourself and in the right quantity. Depending on the scope of application, good concrete can be heavy or light, durable or frost-resistant, set quickly or for a long time, and be more or less mobile.
Typically, concrete is a mixture of cement, water and sand. To increase the strength of concrete, large aggregates in the form of crushed stone and gravel are used, and to give additional properties and ease of production and pouring, various reinforcing substances and plasticizers are added. The heaviest concrete is used in underground bunkers as a reliable radioactive barrier.
To obtain good concrete, you must carefully select all components.
The main link in concrete, a single connection of all components and the most expensive element. For good durable concrete you will need Portland cement grade M500, and if the concrete is prepared at temperatures above 30 degrees, then slag cement is needed. If we are talking about paving a bright garden path, it is better to use white cement; gray Portland cement will drown out any pigment paint. Lime cement has a low setting speed and is optimal for creating small decorative elements.
The cement should be dry and crumbly, without lumps or moisture. If the packaging is torn or the cement was stored outside, definitely pass by. The first cement in importance is the last in terms of timing; it is better to buy it no earlier than a few days before the start of concrete production.
Sand
The main characteristic is the absence of foreign impurities, which negatively affects the strength of concrete and its durability. By type, sand is usually divided into river sand, gully sand and artificial sand obtained by processing rocks. Gully sand is cheaper than river sand, but it contains much more silt and clay, and stone sand adds additional weight to the concrete composition in interfloor screeds.
You can buy ready-made washed sand or drive to the nearest quarry, and then use a sieve to obtain a homogeneous product at home.
To understand how clean the sand is, you need to pour it into a bottle of hot water, mix it and let it sit for several hours. If the water becomes cloudy, this indicates a high clay content. Concrete made from such sand will become loose and crumble.
Aggregate
To obtain durable concrete, you cannot do without coarse aggregate. For high-strength concrete, crushed stone is preferable, and for medium-strength concrete, much cheaper gravel is also suitable. The cost of the material is influenced by the type of crushing - crushed stone is obtained mechanically, it is characterized by roughness and the presence of sharp corners. Naturally, gravel has a more rounded shape. You cannot use river or sea gravel polished by the current; it will not provide the necessary adhesion to the solution. For the foundation, it is better to take gravel of different sizes - from medium to large (with elements from 10 to 35 mm), this will give the particles the opportunity to create a more uniform base. For stairs and decorative elements, you will need fine gravel with a diameter of no more than 7 mm.
Expert tip: Store crushed stone and gravel on a tarp to prevent natural contamination and moisture from the soil.
Water
The main rule: use drinking water. You can safely take water from a sewer or tap, but from a well or river it is not recommended; its composition can bring many unpleasant surprises.
Expert advice: to increase the elasticity of the solution, add liquid soap to the water.
Supplements
To make it easier to lay concrete, lime is usually added. It is sold already slaked in bags or in buckets in the form of lime paste. Sometimes it comes across under the name “fluff”. When working with lime, it is better to wear not only gloves, but also a mask, as it has strong corrosive properties.
If the foundation or concrete product has a complex shape, then plasticizers will need to be added to the solution, affecting viscosity and fluidity. They will help quickly fill the most inaccessible places and significantly speed up the process.
When forming a thin screed or unstable soil, special reinforcing substances will be needed. Such substances prevent the formation of shrinkage microcracks and increase the impact strength of concrete several times.
Expert advice: additives should not exceed 2 percent of the mass fraction of cement in the solution. At sub-zero temperatures, potash is added during mixing.
Types of concrete
To form the main part of the foundation for the house, you will need strong concrete with the inclusion of coarse crushed stone and high fluidity for compaction. To equip the base for the foundation, lighter concrete made of sand and cement is used. To achieve the optimal price-quality ratio, it is necessary to understand the purpose for which concrete is made. Depending on the composition and grade, concrete is divided into three groups:
- Lightweight concrete (M100 and M150) - wooden house, garage, curbs, screeds, stairs. The main advantage is that crushed stone can be replaced with gravel, especially if you have a farm and have a stone crushing machine.
- Medium concrete (M200, M250, M300) - reinforced concrete products, piles, good durable houses of 2-3 floors. This concrete can be used to build walls and pour monolithic foundations.
- Heavy concrete (M400, M500 and above) - can withstand 5 or more floors. Used in the construction of swimming pools, water parks and bank vaults, it sets quickly and is expensive.
Percentage composition
The most common ratio used when pouring a foundation is one part water and one part cement, three parts sand and six parts aggregate. For an accurate calculation, it is better to use a table based on M500 cement, sand and aggregate:
| Type of concrete | Composition C-P-W, % |
| 100 | 6–36–52 |
| 150 | 8–34–50 |
| 200 | 9–32–50 |
| 250 | 11–28,5–49,5 |
| 300 | 11,5–27,5–49,5 |
| 400 | 15–23–47 |
| 450 | 16–22–46 |
Mixing concrete
If you need to make a foundation for a house of about 100 square meters, then you can’t do without a concrete mixer. The cost of purchasing it (10,000–20,000 rubles) will be justified by the ease of kneading. It will not be easy to mix all the ingredients manually without adding a large amount of water, which, in turn, will affect the consumption of expensive cement. On the market today you can also buy mechanical concrete mixers so as not to be tied to the power grid. If we are talking about paving a path or making a concrete staircase, then improvised means are quite suitable.
To prepare the mixture manually we will need:
- Container for mixing - pallets or an old bathtub.
- The weight measure is a metal bucket.
- A pair of shovels for mixing.
Add the ingredients one by one, stirring constantly:
- Water.
- Cement.
- Sand.
- Supplements
- Aggregate.
Expert advice: we do not use all the water at once, but divide it into 2 parts. 80% - first, the rest - after adding all the ingredients.
The mixing time should take no more than half an hour, otherwise the cement will begin to set. It is better to prepare concrete in small portions for transportation by wheelbarrow to the place of installation.
Pouring concrete
The main danger when pouring concrete is uneven distribution over the surface and the formation of air voids. For this purpose, you can make a homemade vibrator from a hammer drill or drill. Depending on the thickness of the concrete coating, you will need a reinforcing rod of various lengths and a rubber hose that will prevent the solution from getting on the rod. Filling should be done gradually, in layers of no more than 10 cm. If the filler is well compacted, then cement laitance should appear on the surface.
Expert advice: the drill should be designed for long-term use; it is better to take a device with a power of 650 W or more.
To protect it from the external environment and ensure uniform drying, the concrete is covered with a film. Approximate drying time is 36 hours to 2 weeks, and the strength of the concrete will increase over time and reach its maximum after a year.
We are always building something on our six-acre plot, sometimes a house, sometimes a barn, sometimes a garage. We start, of course, from the foundation. For this we need a concrete solution.
Making suitable concrete is not a difficult task and anyone can cope with this task. It can be prepared at home without any problems. The most important thing is to maintain the correct ratio of all components.
Composition, proportions and grades of concrete
Concrete composition is a durable, strong material. If it is mixed correctly, it only gets stronger over time. Neither dampness, nor mold, nor fire affects it. The main component is gravel (or crushed stone). It is also the main filler, which makes up up to 80% of the finished composition.
To build an ordinary private house, you can prepare a solution of class B or another grade M-350. Today this is the most popular and versatile type. What is the best way to make concrete yourself, maintaining the correct proportions?
For one bucket of M-500 cement we will need:
- two buckets of river sand;
- four buckets of crushed stone (or gravel);
- about half a bucket of water.
If we convert this ratio into kilograms, then from the calculation of a ten-liter bucket we get the following proportions. Let’s take 13 kilograms of M-500 cement, 14 kilograms of sand and 14 kilograms of gravel.
It is important to note that if you, for example, take a cement of a different brand (say M-400), then even if all the above proportions are maintained, you will get a concrete composition of a different brand - M-250.
The most common composition is cement, sand, filler, water (1/3/5/1).
The process of preparing concrete composition at home
Inviting workers or a construction crew to pour the foundation of your country house is a very expensive business. Therefore, let’s ask ourselves the question: how to make concrete yourself, while saving your energy and finances?
You can mix all the ingredients in an old bathtub, or better yet, in a small concrete mixer, or, in extreme cases, on a metal sheet. For example, for 100 liters of mixture we will need:
- three buckets of cement;
- five buckets of sand;
- eight buckets of crushed stone or gravel.
Auxiliary additives:
- dishwashing liquid;
- PVA glue;
- liquid glass.
It is necessary to choose the right concrete mixer and you can read about it in this article.
Some of the home-grown craftsmen have adapted to adding Fairy dishwashing liquid. It increases the strength and ductility of the concrete composition. Other Kulibins, in order to make better and more plastic concrete with their own hands, add PVA glue at the rate of one glass per bucket of water. Liquid glass reduces porosity, increases hardness and setting time. The latter additive forms a waterproof film and protects the foundation from spring groundwater.
First, cement is mixed with sand, and then water is added. Gravel or crushed stone is added last. Now mix everything thoroughly and pour the resulting “porridge” into the prepared trench. If it is too liquid, then level it with a shovel, filling all the hollow spaces. With a “hard” composition, the work is more difficult; you have to use a tamper or a vibrator.
For small volumes of work, for example, when pouring concrete paths on a personal plot, experts advise using a dry mixture. Combine all dry ingredients into a single whole and mix thoroughly. After this, add water little by little and stir again. It is important to exclude small and medium-sized lumps in the mixture. The use of bayonet and shovel shovels is commonplace for every gardener.
Main components and requirements for them
The quality of cement is determined by the letter M with numbers. For example, M-150 can be used for preparing plaster mortars for interior work, and M-400 and higher can be used for preparing concrete mortars (pouring foundations, concrete supports). Also, the quality depends on the sand and crushed stone.
A mixture of coarse river sand and cement mortar works well. Concrete can be made as a substrate, both in the formwork and in the trench where the foundation will be located. In more durable bases, crushed stone of various sizes is used - from 5-7mm to 30mm.
It is necessary to take into account that the quality of the resulting mixture depends on the purity of each incoming component.
Now let's consider what characteristics are required for cement?. This is the only component that ties everything together. You cannot use damp, expired or discounted material that has been lying on the base for an unknown amount of time.
In unsuitable storage conditions, it will gain moisture and lose some of its properties. In Russian labeling, in addition to strength (letter M), the amount of minor substances (letter D) is also indicated. For example, M400-D20 means that the cement contains twenty percent impurities.
Sand requirements. It is always used. Only in the rarest cases do they do without it. To make high-quality concrete correctly, we use sand of 1mm or 2mm fractions. To clean the sand you brought, run it through a sieve.
It is better to use river water, since it contains practically no admixtures in the form of clay and silt deposits. An additional option could be artificial heavy sand. If you sift it and wash it properly, it will be even better than natural river water.
Gravel (crushed stone) gives strength and reliability to the concrete composition. River pebbles are polished to a shine, so they are not suitable. In this case, the best breed is from mountain quarries. For example, expanded clay is often used because it is light and durable. The size of crushed stone varies from 10 mm to 35 mm. Large gravel is used only in production. Several sizes of filler must be used in the solution.
To make high-quality concrete, according to the rules, it is necessary to mix both large and medium crushed stone. It is clear that there is no special equipment for compaction at the dacha, so large and medium gravel will fill large voids.
Water requirements. It is better that it has neither alkaline nor acidic impurities. It is not advisable to fill with lake or swamp water, which contains many impurities.
Sometimes plasticizers are used. They are needed as a binder. For pouring a simple foundation in a country house, they may not be needed, but for foundations of complex shapes or for thin screeds they will definitely come in handy.
Auxiliary elements. These are special additives to ensure rapid setting or hardening of the mixture at low temperatures or with large amounts of moisture. The most important thing is to decide on the type of supplement and choose it correctly when purchasing.
A reinforcing agent is sometimes used when making thin screeds. For example, polyvinyl chloride or polypropylene fiber itself is not very strong, but soft. It is used to prevent cracking of the finished base.
Of course, each builder will have his own individual concrete solution. But if you apply everyday savvy and follow the instructions exactly, it will turn out strong and reliable. We wish everyone good luck!
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There are several types of concrete mortar, which differ both in quality and proportional composition. The use of one or another solution option is determined individually, depending on the location of concreting. We will learn further about how to make concrete with your own hands.
How to make concrete with your own hands, proportions and technology
The most important component of concrete mortar is cement. Its function is to connect the other components with each other. Portland cement is an ideal option for making concrete. This is explained by the fact that it contains a large amount of calcium silicates. Thus, it is possible to achieve high adhesion between all components.
The type of cement used in the process of making concrete mortar is determined by the individual indicators of the scope of its application. Most often, grade 500 cement is used. Lower quality grades are used to prepare concrete for surfaces that are not subject to high loads.
Portland cement is used to improve adhesion between all components at both high and low temperatures. However, the minimum temperature for using concrete mortar is fifteen degrees. If concrete is still used at low temperatures, then its composition must contain special substances in the form of additives and plasticizers. The substance in the form of Portland slag cement is used if work is carried out at temperatures above 25 degrees Celsius.
The amount of impurities in the cement substance should not exceed twenty percent. This is indicated in the marking with the letter D. When choosing cement for the mortar, pay attention to its external indicators. It should be free-flowing and should not contain additional moisture. It is not recommended to buy material that has lumps and has a damp appearance.
Critical elements are built from concrete, which will quickly collapse due to poor quality cement. The material should also be stored in specially designated conditions, at a temperature of 10 degrees Celsius and a humidity not exceeding 60%. Cement easily absorbs moisture and odors from the external environment and quickly loses its positive characteristics. We recommend purchasing fresh cement that will be used within one or two weeks.
The second component of concrete mortar is sand. There are varieties of concrete solutions in which you can do without sand. This is only possible if the filler composition has no gaps or they are minimal.
The optimal sand fraction is from one to five millimeters. When choosing sand, give preference to materials that have sand grains of equal size. Sand should not contain clay or other impurities. The presence of remnants of vegetation, stones, and construction debris negatively affects the quality of the resulting concrete solution.
If you have sand that is not very clean, we recommend sifting it several times before use. The best option is to use river sand, the cost of which is slightly higher than regular sand. However, such material does not have clay or foreign inclusions and has good performance characteristics.
The presence of clay in concrete is unacceptable; it negatively affects its strength and service life. The next point is to ensure maximum adhesion of concrete and coarse aggregate. These factors are the main ones in determining the overall strength of a concrete solution. In order to prepare the sand for work, we recommend washing it and leaving it to settle.
If it was not possible to purchase high-quality sand, then the option of using artificial sand is possible. To make it, rocks are finely crushed. This sand has greater density and weight. Please note that a concrete solution made from such sand will be heavy.
To increase the strength of the concrete solution, crushed stone or gravel is added to it. They act as a filler for concrete mortar. It is not recommended to use pebbles for these purposes, as their surface is smooth.
When choosing a filler, ask what type of litter it is made of. The expanded clay material is lightweight, but at the same time connects all the components well. The filler size ranges from 0.8 to 4 cm. It is recommended to choose medium-sized substances. It is recommended to choose a substance that does not contain dust and clay inclusions. The reliability of adhesion is determined by the roughness of the material.
Add a filler to the concrete solution that contains both large and medium particles. In this way, it is possible to achieve a tighter fit of the filler to the surface. Sand and filler should be located near the work site. In order to prevent contamination of sand or filler, we recommend pouring them onto a base previously covered with film.
The last of the main components of concrete mortar is water. It should not contain alkaline or acidic inclusions.
Substances in the form of:
1. Lime.
Using this material, the convenience of laying concrete mortar is increased. Thus, it is possible to improve the process of leveling the concrete solution. Lime reduces the strength of the mortar because the bond between cement and aggregates is reduced. Please note that lime must be slaked.
2. Plasticizers.
In order to make decorative concrete by hand, it is recommended to use substances in the form of plasticizers. With their help, it is possible to change the quality characteristics of the solution.
3. Additional components.
With the help of certain components, the concrete solution becomes more progressive. In addition, by using additives it is possible to improve the setting of concrete mortar. Before using additives, study their characteristics and instructions for use. If the work of pouring concrete is carried out at low temperatures, then additives cannot be avoided.
4. Reinforcing components.
With the help of special additives it is possible to perform additional reinforcement of the concrete solution. For example, it is recommended to add fibers based on polypropylene or polyvinyl chloride to the concrete solution used to screed. These components are soft and especially durable. In this way, it is possible to achieve ideal smoothness of the concrete and prevent its cracking.
How to make foundation concrete by hand - composition proportions
The composition of concrete and the amount of connection of its components is determined by the purpose of using the concrete solution. For example, in order to build a foundation, you need strong concrete, which contains large crushed stone and a mortar that secures it securely.
At the same time, it is important to achieve fluidity of the solution, since it should not contain air bubbles or foreign inclusions. Before you start pouring the solution, it is recommended to make a substrate. To do this, it is enough to use a solution that is less durable in composition and contains inclusions of fine sand. At the same time, the consistency of the solution resembles wet soil.
The foundation mortar can be made using concrete by hand. At the same time, the filler should be medium in fractional size, and the consistency should be fluid. In this way, it is possible to distribute the solution on the surface. In addition, fine or medium fraction filler is used for the manufacture of flowerpots, garden elements, and concrete balusters.
The composition and quantity of components that the concrete solution contains are determined by SNiP. In this case, the density of each ingredient should be taken into account. We recommend using a medium-density concrete solution. After completing the calculations, proceed to connecting the components together.
The most popular component ratio involves using one part cement to three parts sand and six parts filler, with the amount of water varying from 0.4 to 1. Water makes the solution more or less fluid.
After determining the optimal consistency of the solution, you should measure the components. Please note that it is not recommended to use wet sand for work; it is recommended to dry it before adding it to the solution.
Before you make concrete steps with your own hands, you need to prepare a concrete solution. Most often, a concrete mixer is used for this. This device allows you to mix all ingredients evenly and quickly. The manual method of preparing concrete mortar is relevant only if the amount of work is small. At the same time, there is no possibility of controlling the recipe in this case.
There are two ways in which you can build a concrete solution yourself:
1. First, the dry ingredients are mixed together, and then water is added.
2. Sand, aggregate and cement are added to the water.
The first option is also called dry, in which all components are uniformly mixed together. In this case, water is added last. Sometimes, this composition contains dry lumps that reduce the strength of the solution. In order to avoid their appearance, we recommend using the second method of mixing the solution. It is suitable for mixing concrete in small quantities.
In any case, we still recommend using a concrete mixer to mix the solution. If you do not have this device, then rent it. The concrete mixer must be located near the work site. Thus, it is possible to avoid delamination of concrete during transportation.
A standard concrete mixer contains about two hundred liters of solution. This amount should be used as a guide when calculating the amount of ingredients. The process of preparing a solution in a concrete mixer is as follows:
1. Measure out the required amount of water and pour it into the concrete mixer. Do not fill in all the water, leave about 10% for later to bring the solution to the desired consistency.
2. Put cement in the required quantity, also leave some cement.
4. After preparing the cement mortar, add substances to it in the form of additives and plasticizers, if necessary.
5. At the final stage, filler is added. If the solution needs to add water, then it is mixed with cement, the resulting mixture is added to the concrete mixer at this stage.
All work is completed within 10-15 minutes. If it was not possible to extract the entire solution at one time, then it is constantly stirred until complete extraction.
How to make colored concrete with your own hands
Before making a concrete flowerpot with your own hands, we recommend painting the solution with color pigments. Modern technologies make it possible to make various concrete surfaces colorful and bright.
Pigments are added either at the stage of preparing the solution or after the composition has hardened. There are two options for color pigments:
- natural;
- synthetic.
The color palette and saturation are determined by the chemical components of the pigment. It is recommended to add pigment to the composition at the mixing stage. In this case, it is possible to achieve a uniform and beautiful color. In order to maximize the color effect on the surface, we recommend using sand and white cement when preparing the solution.
Before adding pigment, it is diluted with water. The quality of mixing affects the homogeneity of the solution. Moreover, such a composition is prepared exclusively in a concrete mixer. It is impossible to prepare concrete mortar manually.
Before making a concrete path with your own hands, it is also recommended to prepare a solution in a concrete mixer. This device not only saves time, but also significantly improves the quality of the finished solution.
When pouring concrete mortar, it is recommended to use a concrete vibrator. With its help, it is possible to remove air bubbles and improve the quality of the finished coating. Additional reinforcement is provided by steel reinforcement bars. The optimal setting time for the solution is about two days. Complete drying of the solution takes about two weeks or more.
Make concrete with your own hands video:
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| Home construction always involves a lot of money. I am often asked how to save money and, in general, is it possible? On small home construction - of course, yes, but in no case on materials. After all, the main thing depends on them - quality and reliability. And you have to live in this house, and then complain all the time, oh, why did I spare the money and not take this and that normal thing - ruining your nerves and health. You can reduce the cost of home construction in a simple way - do the work yourself. That is, excluding particularly expensive equipment. For example, a concrete mixer. It costs, oh, how expensive, rent will be cheaper, but it will also take a decent amount of money out of your pocket. Therefore, my advice to you is to exclude the concrete mixer from the list of equipment if you have:
As you can see, I give examples of cases when mixing concrete is necessary, but not so much is needed. And it is quite possible to cook in small quantities - 20-30 liters. This is exactly the volume that can be easily pulled out by a construction mixer (not an ordinary drill, screwdriver or hammer drill with an attachment), namely a mixer. It is specially adapted for kneading - both the design with two handles and low speeds can be done. In such cases, simply destroy the drill. |
Preparing concrete mortar using is a labor-intensive process. It requires, firstly, good physical strength, as well as certain knowledge and skills. I’ll say right away that to create a uniform and high-quality concrete solution with your own hands, you need to work hard. But many developers interfere, and nothing happens. Often on forms they show off even particularly large batches using a mixer - a 100-liter barrel, or even several such containers in a row. I honestly admit that I haven’t mixed a 100-liter barrel with a mixer, so I don’t recommend it. It’s better to do it little by little, 30 (maximum 50) liters at a time, then the mixer will hold up accurately, and won’t overheat, won’t burn, and will mix well.
Basic tools for mixing concrete by hand
Mixing concrete, like every work process, begins with the preparation of materials - water, cement, sand. You also need a container - a large vessel - to mix it all.
Let us consider in detail the most important elements in preparing manual kneading of material:
1. Capacity
If you can mix manually with a shovel directly on the ground or on a metal sheet, then you need a bowl for the mixer. The container for mixing concrete should have a trough shape. The most convenient is a metal bathtub or basin. You can also do it in a barrel if it is shallow. The dimensions of the trough depend directly on your need for the finished product. For small amounts of concrete, it is better to take small containers. If it is necessary to lift the finished solution to a height, use containers with special hooks to secure the rope. To extend the service life of such vessels, you should follow a few simple rules. The first of these, which is mandatory, is to constantly clean the inner surface of concrete residues after each use.
2. Construction mixer
Preparation of concrete in small quantities involves the use of. Only this unit allows you to create a uniform mixture, which can then be easily distributed over the work surface. A mixer is the key to high-quality concrete pouring. To mix concrete, you should choose a powerful device that can withstand the full force of the workload. The quality of the nozzle, its material and shape also play an important role. You choose it yourself, since there are cases when the whisk is included. For concrete, screw nozzles are most often used, which prevent air from entering the mixture. A hand-held construction mixer will quickly and easily handle a uniform mixture.
3. Additional tools
Wheelbarrows, buckets and shovels are often used for transportation and further work with ready-made mortar. We carry it with a wheelbarrow, we measure it with buckets and we carry it. And shovels are used to collect ready-made concrete into containers for transportation and transfer. By the way, a shovel is also convenient for scraping fresh solution from the walls of a basin or bathtub after work.
4. Materials
It is impossible to mix concrete correctly without quality materials. That is why, before the work procedure itself, not only a reliable drill-mixer is selected, but also cement, sand, crushed stone and water that have good technological characteristics. The proportions for concrete may differ, which leads to the creation of types of material with different properties. Optimal ratios for home construction:
- 1 part cement to 3 parts sand;
- crushed stone - as much as sand and cement together - 4 parts;
- water - 1 part.
- Cement is a dry gray powder that can form a plastic mass when mixed with a salt solution or water. This solution hardens and becomes like stone. In the composition of cement, you can see the names of different substances, which led to the division of cement into types - alumina, slag, expanding, etc. The most popular type of cement in construction is PC cement (Portland cement). In turn, it is also divided into several types. The type of cement determines the quality of the concrete for which it was used. As the most suitable, I recommend Portland cement with its increased and predominant calcium silicate content. Brands designated M200, M300 - they harden normally and withstand loads and weight well.
- It is better to choose sand (as well as cement) that is dry and crumbly. Ideally - river, washed. The sand should have a fraction of 1.5 to 3 mm.
- Crushed stone is small pebbles that come in different sizes. Fine-fraction crushed stone - 5 mm, coarse-fraction - 20 mm. For home batches, it is good to take crushed stone with a diameter of 5-10 mm. If necessary, sand and crushed stone must be cleaned of foreign impurities.
The process of preparing concrete manually
How to prepare concrete with your own hands so that the mixture turns out to be of high quality? This question interests many builders, because you can mix concrete, but who will then be responsible for cracks and uneven coverage? Today there are two ways to prepare concrete using a mixer. To prepare a small amount of concrete in the shortest possible time and get excellent results, you can use either one or the other - your choice.
1. The first method is the most common. First, the dry ingredients are mixed in the required proportions. Cement is carefully and evenly mixed with sand in proportions of 1 to 3. Gravel is added. Stir for 5 minutes. Only then, make a funnel in the evenly stirred mixture (you can use a shovel). A measured amount of water is added to it. And they interfere again. This manipulation (water at the end) is carried out so that water cannot lift light cement to its surface, preventing uniform mixing. If you pour water over the cement itself, it will lead to lumps in the mixture, and who needs them? In terms of proportions, the optimal option for a mixer is:
- 3 kilograms of cement
- 9 kilogram of sand
- 12 kilogram of crushed stone
- 3 liters of water
The total approximate amount of the mixture is 27 liters. Very suitable for a normal construction mixer.
2. Method two. It consists of pouring water first. And then, cement, sand and crushed stone are poured into a measured amount of water, according to the proportion of concrete preparation. Then, using a drill, this mixture is brought to a uniform consistency. I prefer the first method, because the second can lead to lumps. But, in principle, with a good mixer and the right attachment, the mixture should be homogeneous. The advantage of this method is that less solution sticks to the walls of the container.
Tricks of mixing concrete by hand
Preparing concrete with your own hands is a little labor-intensive, but, in principle, there is nothing complicated. Especially if you have certain skills and also know the basic tricks of this process. I'll try to highlight the main secrets:
- Kneading time should not exceed 10-15 minutes.
- The mixing point should be no more than 50 m from the installation site.
- Hand mixing with a mixer is best used for small amounts of concrete. Optimally 20-30 liters. This makes it easier to achieve uniformity.
- You can knead 50 liters, just make sure that the nozzle reaches the bottom of the container. Its standard length is about 60 cm, if it is not enough, lengthen it by purchasing a special device.
- It is better to take crushed stone of two different fractions - small (5 mm) and larger (10 mm).
- When kneading by hand, it is better to mix the dry ingredients first and then add water. In the concrete mixer, just the opposite - first pour a little water.
- At sub-zero temperatures, I do not recommend mixing and pouring concrete. The result is unpredictable, because water can cause freezing and cracks.
- In cold weather, the water can be slightly heated - it should be warm, but not hot.
conclusions
Concrete is widely used in construction and renovation work. It is necessary for creating foundations, frames, and also when connecting structures. Complex concretes for creating large monolithic structures, as well as mortars for large-scale construction projects, are mixed using special equipment. For a small home line or renovation, it is most convenient to use a construction mixer with a screw attachment. It will mix 20-30 liters of mixture evenly and quickly.
Preparing a concrete mixture is quite simple. Need to:
- Have everything you need on hand (container, mixer, cement, sand, crushed stone and water);
- Prepare additional tools - a wheelbarrow, a shovel and a bucket;
- Know the proportions;
- Follow the methods I indicated step by step.
I hope that now that you have learned how to make concrete, each of you will be able to prepare the required amount and confidently carry out repairs and minor construction work.
Concrete is the bread of construction. Without it, no construction project can be completed; various structures and products are produced, from construction ones - foundations, walls, stairs - to decorative ones - benches, garden paths and small architectural forms. And all this is a simple mixture. True, the proportions of concrete and its characteristics can be very different - to perform different tasks.
Concrete is used to make large multi-storey buildings, paths and small sculptures. For this purpose, concrete of different compositions is used.
Concrete composition: components, their sizes and characteristics
- The binder is most often cement, sometimes lime.
- Fillers - sand, crushed stone, pebbles.
- Water.
Different quantities of just three components give a wide range of qualities and characteristics. To impart special properties, various additives and additives are also used, which greatly expands the scope of use of this material.
The main characteristic of concrete is its strength or the load that it can withstand for a long time without losing its strength characteristics. This parameter is the key. Water permeability and frost resistance may also be important. But these are the characteristics of the “ripened” material, which depend on the recipe. And when kneading, you may be interested in such a characteristic as workability. It reflects the degree of concrete fluidity and depends on the amount of water in the composition. You can increase fluidity without adding water using additives, as well as increase frost resistance and water-repellent properties.
The strength of concrete depends on how accurately the recipe was followed, on the quality of the ingredients and on how thoroughly everything was mixed. Only with a homogeneous composition and high-quality components can design characteristics be achieved. Read more about what components can be used and the requirements for them at the end of the article.
Principle of concrete marking
The main characteristics of concrete are its strength and compressive class. The compression class is indicated by the letter “B”, followed by class numbers from 3 to 40, the strength grade is indicated by the letter “M”, followed by numbers from 50 to 1000. They indicate the maximum load that this type of concrete can withstand. For example, the M300 brand means that the maximum load per 1 square centimeter cannot be higher than 300 kg.
In private construction, the most popular grades are M200-M250; for the foundations of two-story houses, M300-M350 concrete can be used; M400 is much less often poured - for heavy buildings on difficult soils. Higher ones are generally rare. Their area of application is industrial construction and objects with special properties (piers, dams, roads, etc.).
The correspondence between concrete grades in terms of strength and compression is given in the table (used in private construction).
| Concrete class by compressive strength | Compressive strength of concrete kg/cm2 | The closest concrete grade in terms of strength |
|---|---|---|
| AT 5 | 65.5 | M 75 |
| B 7.5 | 98.2 | M 100 |
| B 10 | 131.0 | M 150 |
| B 12.5 | 163.7 | M 150 |
| B 15 | 196.5 | M 200 |
| B 20 | 261.9 | M 250 |
| B 22.5 | 294.4 | M 300 |
| B 25 | 327.4 | M 350 |
| B 30 | 392.9 | M 400 |
| B 35 | 458.4 | M 450 |
| B 40 | 523.5 | M 500 |
Proportions of concrete of different grades
This entire range and range of qualities is obtained by using the same materials, just in different quantities. To achieve the required characteristics, the recommended proportions must be strictly observed.
When building your house, you want to do everything as best as possible, and therefore, when making concrete, you want to add more cement to make it stronger. This should not be done. It's unlikely to get better, but it could easily get worse. To gain strength, concrete needs a certain amount of water and other components. If there is little water, there is a lot of cement, bonds between particles are formed in insufficient quantities, which is why the concrete can crack and crumble. The same applies to the number of fillers. Both their too high and insufficient content negatively affects the qualities of concrete stone.
Concrete proportions are usually displayed in fractions. The amount of cement is taken as a unit, and the remaining components are prescribed in relation to it. The data is presented in the form of tables for the corresponding brands; the units of measurement must be indicated. You can see such a table of concrete components below.
How to determine the required proportions of concrete using this table? In the second column, find the required grade of concrete. For example, you need an M250. Depending on which Portland cement you will use M 400 or M 500, choose one of two lines. The third column shows the proportions for concrete in kilograms: for 400 cement it is 1/2.1/3.9. This means this: to obtain concrete grade M 250, for 1 kg of Portland cement M400 you need to add 2.1 kg of sand and 3.9 kg of crushed stone. Similarly, determine the proportions for concrete M200 - the data for it in the table is slightly higher, or concrete M 300 - slightly lower.
The fourth column presents volume fractions: all components are given per 10 liters. They are selected in the same way.
Such tables do not indicate the amount of water. It depends on how thick the solution is needed. The water-cement ratio is given in separate tables. For example, below are data on the number of inputs in relation to a kilogram of cement, provided that medium-sized aggregates are used.
For example, to obtain concrete grade M 300, the proportions of cement M 500 and water are defined as 0.61. This means that for 1 kg of cement, 0.61 liters of water (610 ml) are added to the solution. This produces a medium-plastic solution, which is used most often. But when pouring foundations or other structures with dense reinforcement, a plastic solution may be needed. Then, when determining the amount of water, in addition to the brand of cement, it is also necessary to take into account the size of the aggregates and how fluid the solution should be. These data are presented in the table below.
Sometimes it is necessary to determine how much cement you will need for a particular task. To do this, you need to know how much cement is contained in a cubic meter of concrete. Data on concrete and cement grades can be found in the table below.
Areas of use
We have decided what materials are required for concrete in what proportions, but what brand is needed? This depends on the purpose of the structure and its operating conditions. It will be easier to navigate if you know which grades of concrete can be used for what (let’s name only those that are used in the construction of a private house, its renovation or landscaping).
M100 (B7.5). This is the so-called lean concrete. It is used to prepare sites for critical structures. For example, during construction, a layer of lean concrete is laid on a gravel-sand backfill, and then they begin. The same composition is used when laying curb stones, for example, when making paths or.
M150 (B12.5). This composition is used in preparation for slab foundations, for screeds, pouring concrete floors or garden paths. This type of concrete can be used to make foundations for small lightweight buildings such as a wooden bathhouse or a small guest house made of timber or logs.
M200 (B15). One of the most popular brands of concrete. It is used to make foundations of any type for light houses on normal soils, screeds, stairs, blind areas, paths. Cement blocks are made from this brand of concrete at home, and it is also used in factories for the production of foundation and building blocks.
About how to build it yourself.
M250 (B20). The scope of application is almost the same, but in more difficult conditions. They make any foundations on difficult soils, or on normal ones, but for houses built from heavy materials. They make blind areas that will be used as paths, external stairs, concrete porches, fences, etc. It is also used to make floor slabs for light loads.
M300 (B22.5). Also suitable for all areas listed above, but under even more severe operating conditions. They make foundations for heavy houses on heaving soils, make monolithic walls, paths, waterproof blind areas, etc. This brand of concrete is mainly used to make floor slabs and grillages for pile-grillage foundations.
M350 (B25). The strength of this brand for private construction is generally excessive. This concrete is used for the construction of monolithic pool bowls or for the manufacture of foundations at high groundwater levels, for other structures that require high water resistance. This brand is already more often used in industrial construction.
M400 (B30). This is already an expensive brand of concrete, which is used in facilities with special requirements: for large swimming pools, dams, bank storage facilities, etc.
Preparation of concrete
For large volumes of work, it is better to order concrete from the factory. Making large quantities of mortar by hand or even using concrete mixers is a difficult task, and laying it in batches requires additional effort to ensure that the layers adhere well. However, you can prepare concrete manually. In this case, there are two sequences of actions:
In the first option, there is a possibility that during manual mixing, unmixed composition will remain at the bottom, near the walls of the container, which will lead to a decrease in the strength of the concrete. The solution is to mix everything well and thoroughly. But you can’t spend too much time on this: the solution will begin to set.
The second option has its disadvantages: obtaining a homogeneous cement laitance (a mixture of water and cement) sometimes takes a lot of time. As a result, there is simply not enough of it to form bonds with the backfill: the cement “seizes” and the strength of the concrete also decreases.
All this is not so critical when using concrete mixers, but it is also not ideal. There is another difficulty here. Concrete is usually delivered to the construction site in carts. The entire volume does not fit into one, and the remainder is left to spin in a concrete mixer. This is better than leaving it just standing, but if you mix it too long, the solution may begin to delaminate, resulting in lower concrete strength. The solution is two carts and two people to carry them. The filling method - first or second - choose for yourself.
So after all, how to prepare concrete. The choice is yours. If the volumes are small, you can knead by hand. Just do it carefully. To pour the foundation, it is better to order a mixer, but you can also use a concrete mixer (or two, depending on the volume). And to solve problems with the heterogeneity of the mixture (although it is better that it is good), treat the concrete being laid with a vibrator. Most of the problems will go away.
Requirements for cements for concrete
For most construction work, cement concrete is used, where Portland cement is used as a binding component. There is also limestone, but its scope of application is limited mainly to finishing work, which is done “the old fashioned way.”
Types of Portland cement and their storage
There are several types of Portland cement: Portland slag cement, aluminous cement and pozzolanic cement. They all differ slightly in characteristics, but any are suitable for private construction. The difference can only affect the setting time: slag Portland cement takes the longest to harden - up to 12 hours, followed by standard Portland cement - up to 10 hours, and aluminous binder hardens the fastest - no more than 8 hours.
Cement is demanding on storage conditions, and especially humidity. For the manufacture of important structures - foundations, floors, etc. It is advisable to use fresh one, recently released from the factory. Within a month it loses up to 10% of its properties, and after 6 months they deteriorate by 30-35%. Therefore, for example, when pouring a foundation, it is better to take it a maximum of two weeks ago and purchase it shortly before use.
Store in a dry, ventilated area. If there is no room, they are stored under a roof or wrapped in several layers of film to protect them from moisture. Please note - wrapped, not covered. And preferably not on the ground, but on a wooden floor. The thing is that when moisture gets in, even in a vapor state, the cement becomes lumpy, which greatly worsens the characteristics of concrete. If there is an abundance of moisture, it simply becomes a stone and there is no way to use it. Therefore, take care of a place to store cement in advance.
Cement marking
What brand of cement should be used is usually indicated in the concrete recipe. It is designated by the letter M and numbers that indicate the maximum concrete strength that can be achieved with this binder. For example, with M400 grade cement you can get maximum concrete grade M400, as well as lower grades.
Fillers - crushed stone and sand
The composition of concrete is determined by the functions and characteristics of concrete that are necessary during its operation. The most common are sand and crushed stone. They are subject to no less stringent requirements than the quality of cement. Sometimes pebbles are used, but only if they have sharp edges and not round ones. In the presence of broken lines, the adhesion of the aggregate to the solution is better, as a result, the strength of the concrete is much higher.
Sand
Construction sand can be river or quarry sand. River water is more expensive, but it is usually cleaner and has a more uniform structure. It is best used when preparing concrete for pouring foundations and screeds. For masonry or plastering, it is appropriate to use cheaper quarry sand.
In addition to its origin, sand is distinguished by fractions. For construction work, large or medium ones are used. Small and dusty ones are not suitable. The normal size of sand grains is from 1.5 mm to 5 mm. But optimally in solution it should be more homogeneous, with a difference in grain size of 1-2 mm.
The cleanliness of the sand is also important. It should definitely not contain any foreign organic inclusions - roots, stones, pieces of clay, etc. Even the dust content is standardized. For example, when mixing concrete for a foundation, the amount of contamination should not exceed 5%. This is determined empirically. 300 ml of sand is poured into a half-liter container, everything is filled with water. After a minute, when the grains of sand settle, the water is drained and refilled. This is repeated until it is transparent. After this, determine how much sand is left. If the difference is no more than 5%, the sand is clean and can be used when mixing concrete for the foundation.
For those jobs where the presence of clay or lime is only a plus - when laying or plastering - there is no need to take special care of the cleanliness of the sand. There should be no organic matter or stones, and the presence of clay or lime dust will only make the solution more plastic.
Crushed stone
For critical structures - floors and foundations - crushed crushed stone is used. It has sharp edges that adhere better to the mortar, giving the structure greater strength.
Crushed stone fractions are standard:
Several different fractions are used simultaneously in concrete. The largest fragment should not exceed 1/3 the size of the smallest element of the structure being poured. Let me explain. If a reinforced foundation is being poured, then the structural element that is taken into account is the reinforcement. Find the two elements closest to each other. The largest stone should not be more than 1/3 of this distance. In the case of pouring, the smallest dimension is the thickness of the concrete layer. Choose crushed stone so that it is no more than a third of its thickness.
Fine crushed stone should be about 30%. The remaining volume is divided between medium and large in arbitrary proportions. Pay attention to the dustiness of the crushed stone. Lime dust is especially undesirable. If there is a lot of it, the crushed stone is washed, then dried, and only then poured into concrete.
Aggregate storage
It is clear that a construction site is not the cleanest and most organized place, and sand and crushed stone are often dumped directly onto the ground. In this case, when loading, you must ensure that no soil gets into the mix. Even a small amount will negatively affect the quality. Therefore, it is advisable to pour aggregates onto solid areas.
It is also necessary to protect them from precipitation. In concrete formulations, the number of components is given based on dry components. You learn to take into account the moisture content of components with experience. If you don’t have one, you have to take care of the condition and cover the sand and gravel from rain and dew.
Water
To obtain concrete of normal quality, drinking water must be used. This is what is stated in SNiP: “drinkable, including after boiling.” You cannot take water from a river or lake, especially technical water. No pollutants, acids, salts, alkalis, oils, etc. All these substances negatively affect the strength of concrete, and what’s worse is that the result cannot be predicted.
