Before mixing concrete, the proportions of which will be indicated below, it is necessary to select the components correctly. Generally speaking, concrete is a mixture based on all kinds of aggregates and cement. Thus, concrete contains gravel, pebbles, crushed stone, sand and cement. Among other things, special additives such as plasticizers can be used. Their task is to impart certain properties to concrete. We can highlight the main characteristic of concrete, which is its compressive strength. Based on the strength of the solution after hardening, it is divided into grades.
Concrete composition
If you are thinking about how to mix concrete, the proportions of which will be indicated in the article, you first need to know that the simplest type of concrete consists of cement and coarse sand. Such a solution is usually used as a substrate for the base of a building. In this case, a small amount of water is added to the composition so that the solution acquires a density similar to wet soil. If there is a need to prepare more durable concrete, you will need to use crushed stone as a filler, the fractionation of which varies from 3 mm to 35 mm.
Selection of proportions
Before mixing concrete, the proportions must be studied. For different purposes, you will need to prepare concrete of different compositions. For example, if you intend to form balusters, then when choosing a filler, you must prefer one that has a medium or fine fraction. The same applies to pouring garden utensils, decorative elements, and steps. The most common proportions for preparing concrete are 1:3:6, which applies to cement, sand and aggregate. Among other things, it is necessary to use half or one part of water, which will be determined by the desired fluidity of the solution.
If you are thinking about how to mix concrete, the proportions of materials should be taken into account, but it is also important to pay attention to the composition of the ingredients. Thus, if the sand has a higher humidity than usual, it should first be dried, since it will have a greater weight than that required to prepare the correct solution. The same applies to gravel.
Proportions for preparing a specific brand of concrete
In order to prepare M400 from cement, it will be necessary to use cement, sand and crushed stone in the following proportion - 1: 4.6: 7. But for the production of concrete grade M 150, it will be necessary to prepare all the same materials, but in a slightly different ratio, while cement should be used in an amount of one part, while sand will be used in a volume of 3.5, but crushed stone should be used in proportion 5.7. To prepare M200 concrete, it will be necessary to prepare the listed materials in a ratio of 1: 2.8: 4.8. In order to prepare a solution of grade M 250, you need to prepare materials in a ratio of 1: 2.1: 3.9. To prepare the solution, the master will have to take materials in a ratio of 1: 1.9: 3.7. Concrete grade will be obtained if you use the raw materials in the ratio 1:1.2:2.7. Concrete grade M 450 comes out if you apply the ratio 1:1.1:2.5.
Requirements for components
Before mixing concrete, the proportions must be carefully studied. But it is important not only to maintain the correct ratio, but also to take into account the requirements that apply to each component of the solution. For example, if you use cement grade M 400, and not the structure after hardening, it will not be so strong. In any case, manipulations with concrete cannot be carried out at temperatures below 16 0 C. If such a need arises, then it will be necessary to use plasticizers.
Before mixing concrete, study the proportions well. It is important to pay attention to the condition of individual components. Cement, for example, must be not only free-flowing, but also dry. You should not buy cement that contains lumps or has high humidity. You should not purchase a product that is not labeled. It is preferable to purchase cement immediately before starting work, since during storage it is capable of gaining moisture and losing its qualities. The recommended time to purchase cement is 2 weeks before the start of work.
Sand requirements
If you are thinking about the question of how to properly mix concrete, the proportions for its preparation can be seen above. It is necessary to take into account the quality of the sand that will be used in the work. It is preferable to use sand for concrete, the fractionation of which varies from 1.5 to 5 mm. It is recommended to use sand of uniform size and should not contain impurities. Make sure that there is no construction debris or plant debris in the sand. The presence of all these components can affect After you have found out in what proportions to mix concrete, you can begin work. But you should not use materials that have not been tested for quality. So, for reliability, it is preferable to pass sand through a sieve. It is recommended to use river sand for high-quality concrete, despite the fact that it is more expensive compared to what is called gully sand.
Fillers
If you are concerned about the question of how to mix concrete, the table will help you determine the proportions. It is also important to take into account the quality of the aggregates. They give strength to the concrete mixture after hardening. So, you should not use a regular one or one that has a smooth surface and does not guarantee adhesion to the solution. It is recommended to use material that has been crushed by nature. Among other things, expanded clay is used to prepare concrete, which is quite strong, but at the same time has little weight. When choosing gravel, you need to be guided by the fraction ranging from 8 to 35 mm. Larger fractional elements are used in production, which happens very rarely. In this case, it is also important to take into account that the aggregates should contain the smallest amount of foreign clay inclusions. If necessary, you need to free the raw materials from foreign debris. It is important to choose a filler that has the greatest roughness. This will guarantee high quality grip.
Additional components
If you are thinking about how to mix concrete in a concrete mixer, the proportions presented above can be used by you. It is important to consider not only the ratio, but also the need for additional components. Among them is lime. It will be discussed below. It is necessary to use good quality water when mixing the solution. It must be clean and free from inclusions in the form of acids and alkalis. It is unacceptable to use untreated or river or lake water. Drinkable water can be used in the preparation of concrete.
Supplements
If there is a need to make concrete more convenient for laying, you can use lime during the mixing process. After laying the solution prepared using it, it will be easier to level the surface. But it is worth remembering that lime can interfere with the bond of cement with the aggregate contained in the composition, which can significantly affect the strength. Thus, it is up to the master to decide whether to use lime or not. You should not think that its use will be extremely difficult; you do not need to extinguish it yourself. Instead, you can use ready-made slaked lime, sold in building materials stores.
Finally
Before mixing concrete, the proportions (they are no different in a concrete mixer) must be carefully studied. This will allow you to obtain high-quality concrete, which, after hardening, will be highly durable.
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 concrete mortar hardens completely, it becomes stone. It is impossible to imagine a single construction project in which concrete would not be used.
However, the material must meet certain requirements. Only in this case can it be used to build a durable structure that will last for decades. To make the material as durable as possible, it should be manufactured using 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 is always used as a binding agent when creating a concrete mixture. It is manufactured in different variations. The choice of a specific brand of cement depends on the final purpose of the concrete product and the conditions of its use. Bonding quality 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, choose cement grade 500 or higher. When constructing structures that will experience severe loads, you should choose cement powder of a higher grade.
Cement powder has such a characteristic as shelf life. After a certain time, the material begins to lose its beneficial properties. If the cement is fresh, it is friable and does not have compactions or lumps. When various compactions are present in the powder, cement should not be used in the work. Such a powder has already absorbed a certain amount of moisture, which affected its binding properties.
Sand selection
Sand can have different characteristics. The strength of the final result will depend on how correctly it is selected. When preparing concrete mortar, different types of sand are used. One of the main conditions is the absence of dust or clay particles. If there are quite a lot of such inclusions, the mixture will be of low quality. This can be especially true for fine sand, which contains a high percentage of dust particles. It cannot be used to make concrete.
How not to make a mistake when choosing sand? After all, only by choosing a high-quality material can you make the most durable concrete possible. 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 preliminary cleaning. It usually contains a lot of tree roots, leaves and bark. Quarry sand must undergo washing and settling.
If any organic inclusions get into the concrete, it will lose a certain percentage of its strength. This is explained by the formation of voids in the finished solution when mixing concrete with dirty sand.
Another important factor is the moisture content 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 significantly decrease. The exact proportions for preparing concrete are chosen in accordance with the requirements for the final result. The differences between different grades of concrete are summarized in the table:
Gravel and crushed stone
The main fillers for concrete are often gravel and crushed stone. This material is a rock that has been crushed to a certain size. It can be classified depending on the size of the individual elements. Crushed stone can have a rough or smooth texture.
Crushed stone can be:
- very small - individual components range in size from 3 to 10 mm;
- small - stones have a diameter of 10-20 mm;
- medium - such crushed stone has a size from 20 to 40 mm;
- large crushed stone has a diameter of 40-70 mm.
To make concrete that will last for many years, it is necessary to choose crushed stone such 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 one more indicator - the voidness of the filler. It is determined by the amount of empty space between the stones. It is quite easy to determine. To do this, you will 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 voids of the filler are 30%.
This indicator affects the amount of sand and cement that will be used to create concrete. The less voidage, the less other components will have to be used to create the mixture.
To fill the voids as much as possible, crushed stone of different fractions is used. Stones of both small, large and medium sizes are taken. It should be taken into account that fine elements must be used in 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 a filler. When creating ultra-light types of concrete, gases are used as filler. However, when producing such concrete, certain requirements must be observed. Otherwise, the finished product will not meet standard standards. Table of general requirements for concrete:
Fillers for concrete mixtures can be dense or hollow. Natural materials have less background radiation than artificial ones. Granite rocks have the lowest indicator. 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 negatively affect the strength of the concrete product. The basic rule when making a mixture is this: if water can be used for cooking, it is also suitable for mixing concrete. It is not recommended to use water from the swamp.
Each element of the solution has a certain moisture content. The moisture present in building materials is excess water that can spoil the finished concrete mixture. 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 plasticity of concrete. The plasticity of a 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 slides in the case of a slight tilt of the shovel, it can be considered medium-plastic. Concrete has low plasticity and will not slide even if the shovel is tilted strongly.
Strength gain
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 day of pouring can concrete become as strong as possible. Special requirements for this indicator are imposed when creating concrete for the foundation.
The calculation of concrete composition must be carried out taking into account certain data. Among them are:
- brand of cement powder;
- characteristics of the granulometric composition of crushed stone and sand;
- plasticity of concrete to be achieved;
- required grade of ready-mixed 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. The proportions of concrete to choose for the foundation should be determined according to the required grade of the finished product.
Calculation by weight
The composition can be calculated 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 purpose, the W/C indicator is determined. It represents the ratio of water and cement. This characteristic is determined experimentally or using 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. To simplify the calculations, it should be mentioned how much certain materials are contained in a 10-liter bucket:
- 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 method of such calculation is somewhat inferior to the methods used by professional builders. However, this method is still good for household purposes. In addition to using proportions by mass, proportions of the mixture composition according to volume are also used. This method is less accurate.
Proper mixing of concrete
Concrete can also be mixed manually, but mixers or concrete mixers are more often used for this work. In the first case, the finished mixture is small in volume. To properly mix the solution, you will need a container of a certain volume. Usually a tin trough is chosen for this purpose.
The proportions for preparing 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 method for creating concrete products in the homestead. 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 stripe is drawn in it in the middle. Cement is poured into the groove. Then these ingredients must be thoroughly mixed. After this, crushed stone is added. The resulting mixture is kneaded until each stone is covered with the solution. At the same time, add water a little at a time. Its quantity regulates the plasticity of concrete. When the mixture is homogeneous, the concrete can be poured.
When mixing by hand, it is important to pour the prepared solution as quickly as possible. If there is a short delay, the concrete will begin to delaminate. In this case, water begins to appear on top of the solution. It is better to mix the 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 added. 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 concrete pouring site. This condition must be observed so that the concrete does not lose its properties during delivery to the installation site. If you follow these simple rules, you can get a reliable and durable design.
Owners of private houses often carry out construction work on their own, without involving third-party specialists. And one of the most popular questions that faces them is how to properly and quickly prepare concrete with your own hands? You can answer it using a number of simple rules.
Cooking features
Before preparing concrete, you should determine the amount of material you will need for the work. The calculation is made based on the total volume of concrete structures, taking into account a small margin. In addition, there are several points to take into account:
- when mixing concrete in a concrete mixer, the crushed stone fractions should be within 10–20 mm, when using a shovel - of any size;
- for the construction of houses, the concrete solution must include cement grade M200 or M500;
- In order for concrete preparation to proceed correctly, it is necessary to use only clean water. If you also take it from under the filter, you can almost completely avoid the appearance of lumps during kneading;
- all ingredients must be fresh and clean, there should be no impurities or debris in their composition;
- In order to make high-quality concrete with your own hands, it is recommended to use river rather than quarry sand.
Materials and tools
Proper preparation of concrete mixture will not work without the following materials:
- crushed stone;
- cement;
- sand.
The following tools should be prepared for mixing concrete at home:
- concrete mixer;
- shovel;
- container;
- building level;
- three metal buckets with which you can make a solution (for cement, crushed stone and sand, as well as for water).
Concrete grades and their application
There are quite a few grades of concrete in terms of strength. Each of them is used to perform its own types of work. Although some are universal and can be used to perform various designs.
Concrete with low strength
Not too strong concrete M100 is usually suitable only for preparatory work. Sometimes they are used to make a road surface - as a bottom layer in certain areas. The stronger M150 grade will be an excellent option for a concrete floor in an industrial building. It is also used to make screeds and leveling fillers.
Medium brands
The most popular variety is M200, used in the formation of load-bearing structures of buildings. It has an almost ideal strength-to-cost ratio among all concretes, which is why it is popular for both commercial and private construction. And the M250 brand, which is also distinguished by good strength, will be a good option when performing monolithic work on the lower levels of buildings, as well as for creating foundations.
High strength materials
M350 concretes are necessary for the construction of complex structures of floors, beams with a high degree of load and specialized buildings at industrial enterprises. M400 is suitable and widely used for bridge construction. Although in some cases the use of the brand is determined by the special operating conditions of the building.
Component proportions
In order to prepare concrete with your own hands as correctly as possible, you must strictly follow the proportions. Only in this way will the resulting solution have the required consistency, and the hardened material will have the planned strength and density. The proportion of each component, including water, is of great importance.
Sand by volume should be equal to about a third of the total amount of materials. And the proportions of materials by weight are taken depending on what grade of concrete should be obtained.
For one of the most popular varieties, M200, the following composition is recommended:
- by volume, a liter of M500 cement requires the addition of 3.2 liters of crushed stone and 1.7 liters of sand;
- by weight, for 1 kg of cement take 3.7 kg of crushed stone and 1.9 kg of sand.
Proportions for other brands when using M500 cement:
If you take an insufficient amount of crushed stone, the solution will be smaller in volume (1 liter of cement is enough to produce approximately 4 liters of concrete mixture). If you add less sand to the composition, the material will not be dense enough, and too much of it will lead to a decrease in the strength of the concrete. The same applies to water, the share of which depends not only on the brand of material, but also on the moisture content of the components.
Although, as a rule, both the mass and volume of the liquid should be 2 times less than that of cement.
Kneading and laying out
In order to mix concrete correctly, you will need special equipment - a concrete mixer. Trying to do this manually using only a shovel or hoe is only possible for small volumes of product, because it is almost impossible to mix the solution uniformly. While a concrete mixer perfectly mixes all components, saving both effort and time.
Mixing methods
There are two main ways to mix concrete at home. At the first stage, cement is first added to a concrete mixer into which water has already been poured, and crushed stone and sand are poured into the resulting mixture. The second option involves adding all components in the required proportions, except liquid.
And only after that water is poured into the main composition, adjusting its amount depending on the required fluidity of the material. It is considered more rational to prepare concrete using the second method, which guarantees uniform mixing.
During the mixing process, the concrete mixer should be located not too far from the pouring site. This is required by the large mass that the resulting solution has. The small spacing prevents the concrete from setting or separating before it is poured into the mold.
Kneading rules
Before you mix concrete, you should determine how much of each material is needed for the concrete mixer you have. The composition is determined based on the proportion that is chosen depending on the desired brand. The average mixing equipment capacity is usually about 200 liters. That is, it will be enough for him to divide the proportions taken for 1 cubic meter. m, for five.
If the first mixing method is chosen, you first need to pour water into the concrete mixer, and then manually pour cement into it. Sand is added immediately after this. The sand-cement mixture is stirred for 1–2 minutes, and water is added to it if necessary. Now you can add crushed stone to the composition, pouring it in with short pauses for more uniform mixing.
At the last stage, plasticizers are added. The total kneading time should be about 10 minutes. A longer period may cause the solution to set. The concrete mixer should not be stopped rotating (or turned off if a motor is used for this) until it is completely free of material.
Laying
When transporting the concrete mixture to the laying site, its temperature should not fall below +5 degrees. If this happens, the solution will lose mobility and the quality of the material will deteriorate. To avoid this situation, you can purchase heated concrete mixers or simply use warm water to make concrete with your own hands and lay it as quickly as technology allows.
The concrete solution should be poured continuously, ensuring an uninterrupted supply of material. After this, the mixture poured onto the surface or into an appropriate mold is compacted using a vibrating tool. At the last stage of laying, it is necessary to ensure the “ripening” of the concrete - cover it with polyethylene and either organize heating (for winter), or, conversely, water it with water to avoid drying out (for summer).
The time for complete drying of concrete structures is 28 days.
Supplements
Today there are many types of special additives for concrete. By adding plasticizers to the composition of the material, it is given additional characteristics - they improve layability, increase strength and grade, and prevent too rapid setting. Although sometimes such a substance, on the contrary, allows the solution to harden faster. Thus, using additives to make concrete with your own hands is much easier than without them.
When including plasticizers in the mixture, it should be taken into account that less water will be required, and in general all proportions change slightly. In addition, they also save cement (up to 20% by volume). It is for this purpose that additives are often used in the industrial production of concrete and concrete structures.
Concrete is a material used to construct buildings, where it is used to lay the foundation, construct walls, and construct the roof. Small piece objects are also made from concrete, such as paving slabs, garden vases and urns, balusters, and sometimes even countertops for kitchen tables.
Distinctive characteristics
Thanks to modern technologies that make it possible to make concrete of very high quality, this artificial material, in terms of its strength, stands next to natural marble and granite. Despite the fact that it is not as aesthetically pleasing as natural materials, it, unlike natural stones, does not emit background radiation, and it can be given a beautiful appearance using the latest processing technologies.
During the construction process, you can either make concrete with your own hands or buy a ready-made mixture at a hardware store. If you have chosen to prepare the solution yourself, you will need to figure out what components the concrete consists of and in what proportions they need to be mixed.
Concrete composition
Making concrete with your own hands involves combining the following components in a special container or concrete mixer.
- Cement is a key element and basis for the manufacture of both concrete and mortar. It contains limestone, which when mixed with water crystallizes and hardens.
- Ballast is a mixture of sand and gravel, also known as bulk mixture. In most cases, it is made in a 3:1 ratio, that is, one part of fine river sand is taken for three parts of gravel chips.
- Construction sand - sea, aeolian, lacustrine, alluvial or deluvial - resulting from the activity of reservoirs and watercourses, has a size from 0.1 to 5 mm. The shape of its grains of sand is round, and it is this fact that makes it easier to adjust bricks or concrete slabs to the desired level by driving them into the mortar. This sand also contains clay, which, when soaked, makes the solution more viscous.
- Crushed stone is crushed rock with a grain size of more than 5 mm.
When you make concrete with your own hands, to obtain a complete monolithic structure, the above elements must be mixed with water. When calculating the required quantity, it is necessary to take into account not only the ratio of water and cement, but also the initial moisture content of other materials and their ability to absorb moisture.
The basis in the production of concrete is mortar. It finds its application in kiln and plastering works, and is also used in the construction of brickwork. The composition of the mortar includes binding materials (cement, clay, etc.), of which no more than two are usually used, as well as a filler, which can be sand, sawdust or fine slag.
DIY concrete: proportions
The most common ratio of components included in concrete is 1:3:6, that is, one part of cement is three parts of sand and six parts of aggregate. Depending on how thick or thin the solution you need, add 0.5-1 part water. However, if you want to get a solution of the highest possible quality, make an accurate calculation of the proportions of the components, in which the density and binding characteristics of cement, aggregate and sand will play a significant role. You can find out these characteristics from the regulatory documents attached to the building materials.
Basic additives for preparing concrete
In order to make concrete of higher quality and improve some of its characteristics, one or another special additives that are widely used in modern construction can be mixed into the solution. When making concrete with your own hands, depending on what quality indicator you want to improve, you can add the following components to it:
- Plasticizers are used to make concrete more plastic to improve the ease of laying it.
- Hydraulic seals - isolate concrete from excess moisture entering its structure.
- Dust removers - increase the strength of the material and reduce the risk of abrasion.
- Accelerators and retarders of hardening - are used to control the hardening time of the solution.
- Antifreeze additives - allow you to work with concrete in the cold at temperatures below zero.
The use of additives significantly improves the quality of the solution when you make concrete yourself. When purchasing additives, pay attention to the fact that some of them can improve the quality of not one, but several characteristics of concrete, that is, produce a complex effect on it. At the same time, some of them may not be combined with others, so be sure to carefully read the instructions before purchasing the supplement.
Also, often additives change the amount of water required to make a solution to a lesser extent. If the new proportions are not indicated in the instructions for use, then add water very carefully, gradually and in small parts.
Making concrete for the foundation
Let's look at a few rules, following which you can make good concrete for the foundation with your own hands.
The consistency of the solution, from which concrete for the foundation will later be made, should be as thick as possible. After the mixture is laid out in pre-prepared formwork, it must be compacted. This is done using a special vibrator, but if it is not available, you can use a regular reinforcement rod.
Compaction should be carried out until the so-called laitance of cement appears on the surface of the concrete - a liquid mixture of cement and water that occurs when the solution reaches its maximum density. Tamping is necessary in order to remove air bubbles from the concrete and thereby increase its strength.
The standard shrinkage of concrete is 2-3 centimeters. You can check it using a cone made of metal with a base width of 20.3 cm and a height of 30.5 cm. The resulting solution must be poured into the cone and turned over, and then monitor how the material spreads and settles.
In cases where you do not know which mixture composition will be optimal for the foundation, use m400 or m500. Use gravel, crushed stone or sand as its filler. You should not use broken brick and limestone for this: the concrete will not be strong.
Tools for making concrete
Do-it-yourself concrete preparation can be done using tools such as shuffle shovels, electric and manual concrete mixers and hand-held electric mixers. Despite the fact that the quality of material mixed by hand is higher than that produced by mechanization, doing this with a shovel is a very long and tedious task that will delay construction and require a lot of your strength.
In order to make concrete for the foundation with your own hands, it is recommended to use a concrete mixer. In addition to optimizing the manufacturing process, it also prevents possible poor mixing of the solution, which could reduce the density of the final product.
- If the concrete is poured unsuccessfully, small voids are formed inside it, which can only be removed with the help of a deep vibrator. If, taking into account all the shortcomings and errors, you get concrete of grade 100, it will be able to withstand a load of 100 kg/cm², which will be quite enough to build a small house. A foundation pillar made of such material, having a cross-section of 200 × 200 mm, can withstand a load of 40 tons, and five such pillars can withstand a load of 200 tons.
- If you want to make a strip foundation, keep in mind that in this case the weight of the structure will be distributed over a greater density. Accordingly, even if you make small mistakes and deviations from construction rules when laying the foundation, it will still be able to withstand the weight of the structure. But do not forget that the official standard for strip foundations is concrete grade M200 and higher.
- Do not pour the strip foundation during cold weather: in this case, you will have to constantly heat the mixture. If water freezes inside concrete, its volume will increase, causing the product to break down from the inside.
- When pouring the foundation in the summer, moisten it for two to three days so that the concrete does not crack and sets evenly over the entire surface.
Heat-resistant concrete
Heat-resistant concrete is a product that is able to maintain its physical and mechanical characteristics and properties when exposed to very high temperatures (about 16,000 °C). Its use in construction usually occurs in the construction of chimneys and blast furnace foundations.
A special feature of heat-resistant concrete is the use of liquid glass or Portland cement as one of the main elements in its production. To ensure that concrete does not collapse when heated and cooled, chromite ore, magnesite brick, fireclay and andesite are also added to its composition.
The density of freshly laid concrete will depend on the choice of one of these materials: fireclay will give a density of 2200 kg/m3, andesite - 2400 kg/m3, magnesite - 2600 kg/m3, and chromite - 3000 kg/m3. As it hardens, its density usually decreases by 150-200 kg/m3. The filler in the case of heat-resistant concrete is sand or heat-resistant crushed stone from rocks.
If you plan to build a large structure, then you need to take crushed stone, the grain size of which will be at least 40 mm. For the construction of less massive structures, crushed stone with a grain size of about 20 mm is suitable. The choice of material must be made taking into account the operating conditions of the future building.
Production of heat-resistant concrete
Making heat-resistant concrete with your own hands is quite easy if you adhere to the established rules and strictly observe the proportions of mixing its components. There are two main ways to produce high-temperature-resistant concrete: it can either be made from a ready-made mixture sold in hardware stores, or you can create it yourself by mixing the required ingredients in prescribed proportions.
Naturally, the most preferable is to use a ready-made mixture, since this guarantees exact adherence to the proportions of the components and protects the mixture from contamination during its production: it is enough to simply dilute it with water, and the concrete will be ready.
When purchasing a ready-made mixture, make sure that it was made by a certified manufacturer. It should be accompanied by instructions that indicate the method of preparing the composition and the conditions for its use. Prepare concrete as recommended. The finished mixture should be stored in a dark place.
Now that you have learned how to make your own concrete, you can start building.
To obtain high-quality concrete, you need to strictly adhere to the recommendations for the technology of its production, as well as take into account the quality of the constituent materials and compliance with the required proportions. The initial composition and properties of concrete depend on the purpose of the structures made from it.
What you need for cooking
Most often, cement of the M400 and M500 grades is used for the production of concrete. So, M200 concrete recipe requires cement of at least grade M400.
In addition to cement, various fillers are added to concrete: sand, crushed stone, ASG, screenings, expanded clay; in some types of concrete various plasticizers and other additives are used.
How does the calculation work?
When calculating the correct proportions of concrete, you need to take into account many seemingly insignificant factors: the grain size of crushed stone or screenings, the sand fraction, the purity of the sand and the amount of water when mixing the cement mixture. The qualities that need to be given to concrete are also taken into account: elasticity, resistance to deformation, frost and moisture resistance, and others, and all this can be used to prepare M 300.
Proportion on proportion
Each grade of cement has its own proportions to get the grade of concrete you need. So, to prepare M200 concrete from M400 cement, the proportions should be as follows: 1 part cement, 2.8 parts sand and 4.8 parts crushed stone. In this recipe, as in subsequent ones, the mass ratios of materials are indicated.
Proportions of concrete M250:
- 1 part cement,
- 2.1 parts sand
- and 3.9 parts of crushed stone.
With this proportion, from 10 liters of cement you will get 43 liters of concrete.
M300 concrete can be prepared from M400 cement; the proportions of the materials are as follows: as before, 1 part cement, 1.9 parts sand and 3.7 parts crushed stone. 
The proportions of M500 concrete assume a high cement content, which determines the high strength of this brand of concrete. In general, this brand of concrete is used quite rarely. Yes, and according to the passport it is called concrete M550, but among the people the name M500 has firmly established itself behind it for unknown reasons.
Where is it used?
Concrete of this grade is used for the construction of bridges, hydraulic structures, reinforced concrete structures, dams, dams and other structures with increased requirements. It is made only from granite crushed stone using the highest grade of cement.
I would also like to say something about the crushed stone fraction. To ensure high-quality concrete of any brand, you need to use crushed stone with a grain size of 5-20 mm. Sand for concrete should be as clean as possible and free from all impurities in the form of silt, clay or limestone; screenings can also be used.
When preparing a cement mixture, try to ensure that the cement completely absorbs the water so that it is not in a free state. Then your concrete structure will be durable and will serve you for many years.
