According to GOST 25192-82, concrete is called lightweight if its density does not exceed 1800 kg/m3. This is a sought-after building material, reducing the total cost of mixing the mortar by up to 20%, and labor intensity by up to 50. Its thermal insulation, high-quality and design parameters are very high, the bonus of application is the ability to process and cut after achieving strength. Lightweight concrete is divided depending on its components, structure and subgroups, united exclusively by reduced density. Some types are easier to buy than to prepare yourself, while others are quite suitable for kneading with your own hands.
The group includes mixtures based on porous fillers; weight reduction occurs due to a decrease in the proportion of cement and components from hard rocks. The size of large fractions is limited to 20 mm; in rare cases, gravel of no more than 40 is added. As a result, the material is 1.5 times lighter than gypsum mortars, and 2.5 times lighter than cement mortars. The effect is achieved not only by changing the filler, but also by porizing the binder, cellularity lightweight concrete reaches 40%. As a result, it is characterized by reduced strength and minimal thermal conductivity.
Composition, performance characteristics
The structure and volume of gas or air involved in concrete different types differ, they are divided into: dense, porous and coarse. In addition to cement, the following are added as binders: gypsum, lime, slag, polymers, roasting clays, industrial waste. Depending on the filler, there are mixtures based on expanded clay, perlite, agloporite, crushed stone from porous rocks, vermiculite, slag, and ash gravel. As a fine-grained filler, in addition to sand, marble chips, ground pumice, volcanic pouf and limestone are introduced into the compositions. The ratio of water plays an important role; lightweight materials based on aggregates that give porosity are less sensitive to its excess, but when a certain proportion is exceeded, they sharply lose strength. Modifiers and foaming ingredients regulate the volume of entrained air, frost resistance and protection of cells from moisture.
The introduction of porous aggregates into the composition leads to a reduction in the cost of concrete. When choosing a specific brand, they are guided by such properties and features as:
1. Average density, kg/m3.
2. Strength (depends primarily on the type of aggregate, and not on the brand of cement). The main indicator is the class: from B2 to B40. For high-strength grades, the compressive strength reaches 70 MPa, for ordinary grades it varies between 2–20.
3. Thermal conductivity: from 0.07 to 0.7 W/(m∙C). Depends on porosity and density; maximum thermal insulation is observed in concrete with the lightest aggregates (expanded with perlite).
4. Frost resistance: on average from F25 to F100. This characteristic depends on the type of binder (high grade Portland cement can withstand low temperatures best) and the base used. Maximum frost resistance is observed in concrete with the addition of pumice, expanded clay and agloporite.
5. Dry density or porosity is an important characteristic, ranging from D200 to D2000.
6. Water resistance: grades from W0.2 to W1.2.
Useful properties include fire resistance, lightness, ductility, almost all grades are suitable for reinforcement (to increase the load-bearing capacity).
Scope of application
Suitable for the production of finished products: building blocks, slabs for screeds and floors, wall panels, and for monolithic filling. Lightweight concrete mortars are convenient for filling voids in structures and holes in the ground. For private purposes, they are used for thermal insulation of buildings, external and internal fire protection, construction of partitions and load-bearing walls(subject to proper reinforcement). In industrial applications - for repairing tunnels, erecting supports, columns, small bridges, large-block apartment buildings. The use of specialized brands deserves special mention: high-strength ones are relevant when conducting construction work in seismically hazardous areas, light heat-resistant - for laying and lining furnaces.
The material puts minimal load on the foundation and, as a result, is recommended for restoration work, creating decorative and small architectural forms. For the same reason and because of its good thermal insulation properties, it is optimal for horizontal floors. With rare exceptions, lightweight concrete with porous aggregates is not used for pouring or laying foundations, this is explained not by a concession in strength to heavy grades, but by the risk of falling groundwater inside the cells and freezing.
External units made of large-porous concrete require plastering to enhance thermal insulation properties. But the material itself is not water-absorbing, when used in rooms with high humidity(baths, swimming pools, showers) problems do not arise. In general, lightweight concrete is a complete replacement for brick and conventional cement mortars when constructing walls, with the bonus of reducing the weight and thickness of structures.
Production technology
The process largely depends on the structure and composition of the material. The most difficult thing to prepare is foam and aerated concrete: special equipment is used: foam concrete mixers, autoclaves, steaming chambers and complex chemical reagents. In easy cellular concrete no coarse filler is introduced; some brands are completely sand-free.
The main condition of the technology is the distribution of the binder with maximum homogeneity, which is largely due to the reduction in the proportion of heavy cement in the total mass. For this reason, these solutions are mixed longer, more intensively and more thoroughly. Another requirement is the vibration of poured structures: lightweight, unlike heavy concrete, does not delaminate into heavy crushed stone and water, but if the layers are poorly compacted, its quality decreases.
How to do it yourself?
The process depends on the type of solution: it is almost impossible to prepare foam concrete at home, but mixtures with expanded clay or light porous additives are quite possible. The main problem concerns the choice of the W/C ratio; most aggregates are rough and absorbent. Therefore, the proportions are selected experimentally, a small portion is mixed, a test sample is poured and aged. The easiest way to prepare lightweight concrete with your own hands is based on expanded clay: pour water into a concrete mixer, add cement in portions (until it becomes milky) and only then filler, all components are mixed until homogeneous.
There is a constant risk when kneading at home uneven distribution astringent. For this reason, any modifiers are simply added to the water at the beginning of the batch (and not at the end, as with heavy concrete). The exception is fiber fiber; it is introduced into the composition last. Porous thermal insulation fillers require pre-wetting (such as perlite or vermiculite).
Manual mixing is not recommended; if you do not have a concrete mixer, you should use a drill or construction mixer. Lightweight porous concrete retains its structure well and is optimal for using slip formwork technology; the final strength gain depends on the composition.
Cost of ready-made solutions
| Name of product | Class | Strength grade | Price per 1 m3, rubles |
| P4 F50 W2 | 7,5 | M 100 | 3 500 |
| 12,5 | M 150 | 3 750 | |
| 15 | M 200 | 3 800 | |
| Expanded clay concrete F100W4/ D1600 | 7,5 | M 100 | 2 950 |
| 12,5 | M 150 | 3 100 | |
| 15 | M 200 | 3 250 | |
| 20 | M 250 | 3 350 |
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 - perfect option for preparing 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, minimum temperature the use of 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. Material that has lumps and is damp appearance, buying is not recommended.
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 from external environment moisture, odors 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 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- use of 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. Next moment- ensuring 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 quality characteristics 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 making flowerpots, garden elements, 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 the water into the right amount and pour it into a 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 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. Prepare concrete solution manual method impossible.
Before making a concrete path with your own hands, it is also recommended to prepare a solution in a concrete mixer. This device It 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. Optimal time It takes about two days for the solution to set. Complete drying of the solution takes about two weeks or more.
Make concrete with your own hands video:
How to make strong concrete (concrete mortar) with your own hands.
Mortars and concretes are man-made stone materials that are produced by mixing a binder (usually lime and Portland cement) and certain aggregates. When mixed with water, the binder forms a stone-like body, which is explained by the processes of setting and rapid hardening. The strength of the stone-like body is ensured by the filler (gravel, crushed stone, sand). Next, I will tell you about all the stages of the question of how to make concrete with your own hands.
Components for making the solution
1. Filler
For mortar, most often, fine sand or other fine aggregate is taken. For concrete mortar, you can take not only fine sand, but also coarse gravel or crushed stone. To make construction plaster or masonry mortar, it is best to use fine sand, the grains of which do not exceed 2 millimeters in diameter. If the plaster has a special texture, it is possible to add sand with a grain size of up to 4 millimeters. In our market, customers are offered two types of sand: river and ravine. River sand is considered medium-grained, it is quite expensive, but its purity facilitates its use as a component for concrete mixture. Gully sand can be fine-grained (from 0.5 to 1.5 millimeters), with big amount clay particles and other impurities. It is not suitable for good and strong concrete, but for mortars it can be used without fear.
For lean (light) cement concrete with strength class B7.5, only sand can be used as a filler. In concrete of greater strength, in addition to sand, you can also use crushed stone or gravel with a diameter of up to 31.5 millimeters. It is considered correct to use a crushed stone mixture of different fractions so that the finished concrete contains a minimum amount of voids between the stones.
Attention! The aggregate of concrete and mortars should not contain pollutants such as soil, glass, pieces of wood, peat, plants, dusty or silty soil. If contaminants are present, they should be removed by sifting gravel or sand through a sieve.
2. Cement
Cement is a general name for binding powdery substances based on marly, calcareous and clayey rocks and various additives. The most commonly used type of cement is Portland cement, which takes its name from the British peninsula of Portland. This cement contains a large amount of calcium silicates. Under construction country house Two types of Portland cement can be used.
Type I – does not contain additives, or their content does not exceed 5 percent. The European classification for such cement indicates the name CEM I.
In Russian practice, the presence of cement additives is indicated by the letter D and a number in the marking code, which follows the brand. For example, if you see the marking PC 500-D20, then it means the presence of 20 percent of additives in grade 500 Portland cement. As we have already found out, this characterizes type II cement. As for the DO designation, it characterizes type I cement, that is, a material without additives.
To prepare plaster and masonry mortar, you need to take cement of classes M400 (32.5) and M500 (42.5). Portland cement is ideal for preparing concrete mixtures that will be used at low temperatures (daily average below 10 degrees Celsius). If the temperature is high, for example, in the heat, then it is better to use Portland slag cement or type III cement (the European classification indicates the name CEM III). It is well suited for making masonry and plaster solutions, used for fences and floors.
Attention! Cement can only be purchased in bags with appropriate markings. Immediately before purchasing, you need to check whether the cement is damp or caked. If all the signs are present, it is recommended to refuse the purchase. Only a trusted, reputable manufacturer who has been selling the solution for several years can guarantee compliance with the brand of cement stated on the packaging or bag. By the way, the main difference good manufacturer What makes it underground is not the cost of ready-mixed concrete, but the availability of a high-quality delivery service.
3. Lime
Lime is required for the production of cement-lime mortars. In addition, it is used to increase the workability of the solution. Today, to prepare solutions, it is no longer necessary to slak lime. Instead, you can buy slaked (hydrated) fluffed lime at a low price, which is sold packaged in bags already in finished form. Alternatively, instead of a dry mixture, lime can be sold in buckets in the form of lime paste. It is added to cement-lime plaster and masonry mortars to improve their workability.
Attention! If you decide to use lime as part of the question of how to make concrete at home, be extremely careful, since lime has strong corrosive properties. It is recommended to carry out work wearing protective gloves, remembering to ensure that the material does not get into your eyes or skin. The same applies to the use of dyes, as well as subsequent work on grinding and polishing the product.
4. Additives
The composition of a concrete mixture or mortar may contain certain additives that can either improve or simply change their certain properties.
Plasticizers or plasticizing additives can increase the fluidity of the mixture, as a result of which builders receive a solution with a more liquid consistency. This solution is much easier to apply.
Thinning additives or superplasticizers can reduce the amount of water poured for mixing.
In addition, their use makes it possible to improve the workability of the mixture, increase the strength, frost resistance and water resistance of the mortar or concrete.
Certain additives allow you to accelerate the hardening of a concrete mixture or solution.
Also, there are additives that make it possible to carry out work in the temperature range from 10 degrees below zero to 35 degrees hot.
There are special additives on the market that slow down the hardening of the concrete mixture, which is useful when concreting in hot conditions.
Air-entraining or aerating additives increase frost resistance and reduce the moisture capacity of the solution in the hardened state.
Typically, supplements are sold in plastic containers in liquid form. The packaging must contain information about dosage, quantity and basic properties. Additives in mass ratio should not exceed 2 percent of the total mass of cement.
5. Water
The quality of water used for mortars and concretes is regulated by GOST standards. In particular, water must meet drinking standards and must not contain foreign impurities, including sugar, oil, alkalis and acids. It is prohibited to use poorly cleaned swamp and wastewater. It is better to be guided by the principle that you can use any drinkable water to stir the solution. If you prepare a concrete solution using water from a lake or river, you will have to check the suitability of such water in a special construction laboratory.
Composition and proportions
Before you start considering the question of how to prepare concrete or reinforced concrete, I would like to draw your attention to the fact that the composition and proportions will directly depend on its main purpose. That is, it is correct to use strong concrete for the foundation high density, while for pouring the fence you can choose lighter grades. Once you have decided on the ingredients, choose the right brand. In most cases, for imported concrete and mortars created by yourself, it is better to choose grades M300 or M400. As for proportions, the components “cement/sand/crushed stone” should be used in proportions of 1/3/5. This means that per cube of concrete, one part of cement requires the addition of three parts of sand and five parts of crushed stone or gravel. If we talk about water, then its amount should be half the weight of other fillers. For example, if you have 100 kilograms of dry mixture, then you need to take 50 liters of water.
If you get too thick (dense) mixture, you can add a little more water. The consistency should be such that you do not need to exert much effort to stir the solution with a shovel. For wet sand there should be less water. If work is carried out in the cold, the water and concrete must be heated, which will protect the composition from premature setting and loss of strength. For work, it is better to use a purchased concrete mixer or devices/mixers and containers made by yourself. You can read what material and what components they consist of (pumps, molds, vibrating screeds, etc.) in another article.
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Concrete mortar is the most important component in the construction of foundations, and the durability of the entire structure depends on its quality. It is not always possible to order ready mixture, and therefore it is advisable to know how to make concrete with your own hands. Here it is important not only to maintain proportions, but to select the components correctly, otherwise the strength of the solution will not be high enough.
Characteristics of concrete
Strength
Concrete mortar is a mixture of cement, sand, filler and water in certain proportions, which vary depending on the purpose of the concrete and the brand of cement. If necessary, plasticizers are added to the solution. The most important characteristic of concrete is its compressive strength, which is measured in MPa (mega pascals). It is based on this indicator that concrete is divided into classes. But the grade of concrete indicates the amount of cement in the solution.
| Concrete class | Average strength of this class, kg s/sq.cm | Nearest brand of concrete |
|---|---|---|
| AT 5 | 65 | M 75 |
| B 7.5 | 98 | M 100 |
| AT 10 | 131 | M 150 |
| At 12.5 | 164 | M 150 |
| At 15 | 196 | M 200 |
| IN 20 | 262 | M 250 |
| At 25 | 327 | M 350 |
| At 30 | 393 | M 400 |
| At 35 | 458 | M 450 |
| At 40 | 524 | M 550 |
| At 45 | 589 | M 600 |
| At 50 | 655 | M 600 |
| At 55 | 720 | M 700 |
| At 60 | 786 | M 800 |
M100 and M150 (B7.5 and B12.5) are most often used as a layer under the main foundation, for the manufacture of screeds, and concreting paths. Concrete M200-M350 is most in demand: it is used in the construction of foundations, for the manufacture of screeds, concrete stairs, blind area. Mortars of higher grades are used primarily in industrial construction.
Plastic
An important characteristic of concrete is its plasticity. The more plastic the solution, the better it fills the formwork structure. When the mobility of concrete is low, unfilled areas remain in the screed or foundation, which leads to gradual destruction concrete slab. For standard designs Concrete with plasticity P-2 or P-3 is used for formwork complex shape and in hard to reach places It is recommended to use solution P-4 and higher.
Waterproof and frost-resistant
Water resistance depends on the amount and brand of cement in the solution. The higher the grade, the more resistant the concrete is to moisture. Frost resistance of concrete is achieved by adding plasticizers to the composition. It should be noted that these set very quickly; if you incorrectly calculate the amount of mixture or use it at a low temperature, the concrete will turn into a monolithic block right in the container.
Concrete components
Cement performs a binding function for all other components of the concrete mortar, and the strength of the concrete itself directly depends on its quality. In private construction, cement grades M400 and M500 are most in demand. When purchasing cement, you should be aware that it loses its qualities if stored for a long time or improperly. Already a month after production, the binding properties of cement decrease by 10%, after six months - by 50%, after a year it is not recommended to use it at all. But even fresh cement will become unsuitable for use if it becomes damp, so it must be stored in a dry place.
Sand is the second most important component of concrete mortar. In rare cases, it is replaced with slag, while standard concrete is always mixed with sand. It is best to use coarse river sand without various impurities. If only ordinary fine sand is available, it should not contain clay, earth or silt, which reduce the adhesion of the solution to the filler. Before mixing, the sand must be sifted to remove all excess.
Aggregate
The best aggregate for concrete mortar is considered to be in sizes from 5 to 35 mm. Often crushed stone is replaced with gravel, and a little less often with expanded clay. It is very important that the surface of the aggregate is rough, then its adhesion to the cement will be as strong as possible. To compact the mixture, you need to take aggregate of different fractions. Like sand, the aggregate must be clean, so it should be poured onto a prepared and compacted area or on a spread tarp.
Supplements
To give concrete frost resistance, water resistance and other beneficial properties plasticizers are used. They ensure the setting of the solution when negative temperatures, increase its plasticity or, conversely, impart viscosity. They should be used only if it is really necessary, and you should strictly adhere to the instructions for their use and observe the proportions.
If a thin or unstable screed is required, reinforcing fibers are mixed into the concrete solution. They are made of polyvinyl chloride and polypropylene; they have low strength, but are excellent at avoiding cracking of concrete. In standard foundations and screeds, reinforcing substances are not needed.
Prices for cement and basic mixtures
Cement and base mixtures
Solution proportions
To make high-quality concrete yourself, you need to know in what proportions to mix the components. Most often, the ratio of cement, sand and crushed stone is used as 1: 3: 6; In this case, half as much water is taken as the total weight of the dry ingredients. It is recommended to add water not all at once, but in several portions, this makes it easier to control the density of the solution. The humidity of the sand also has its own meaning - the higher it is, the less water required. All components must be measured in one container, for example, a bucket. When using containers of different sizes, it will not be possible to achieve the desired proportions.
When mixing, the purpose of the solution should be taken into account. For the substrate under the screed they make skinny concrete without adding crushed stone, medium and fine crushed stone is used for concreting paths and blind areas, medium-fraction crushed stone and cement are used for the foundation of a house High Quality. Find out the exact different brands The table will help.
Manual method of mixing concrete
Mixing the concrete solution is carried out manually or in a concrete mixer. If you need to fill large area, the first method is not suitable, as it will take too much time and physical effort. If you need a little solution, it is more convenient to knead it by hand.
Step 1. Preparation
To prepare the solution, you will need a low, wide container, for example, a large metal trough, a picking shovel, a bucket and a regular hoe.
Step 2: Dry Mixing
A bucket of cement is poured into the container, then 3 buckets of sifted sand and 5 buckets of crushed stone. The dry ingredients are thoroughly mixed with a hoe. The proportions may be different, depending on the required brand of solution.
Step 3: Adding Water
If all ingredients are mixed evenly, you can add water. First, pour out 7-8 liters and begin to intensively stir the contents with a hoe. This process will require effort, but you need to stir it very well. It is advisable to lift the bottom layer and run the hoe into the corners where dry lumps may remain. If the solution is very thick and sticks to the hoe, you need to add a little water. Properly prepared concrete slides off the shovel slowly and does not delaminate.
There is another mixing option: first, water is poured into the container, then cement is poured. For 2 buckets of water you need 2 buckets of cement. Thoroughly mix the cement with water and add 4 buckets of sand. Mix well again until smooth. Lastly, add crushed stone in the amount of 8 buckets and mix again. There is no clear opinion on which method is better, so it’s worth trying both and determining the most optimal one for yourself.
Find out the correct proportions, how to make them yourself, from our new article.
If the resulting concrete is too thick, add a little cement to the remaining water, mix well and pour into a concrete mixer. It is not recommended to stir the solution for more than 10 minutes, otherwise the cement will begin to set. Ready concrete is poured directly onto the site or into a wheelbarrow if the concrete mixer is located at a distance. It is advisable to pour out the entire solution at once, but if this does not work, leave part of the mass in the turned on concrete mixer. It should be used as soon as possible.
Prices for popular models of concrete mixers
Concrete mixers
Video - How to make concrete with your own hands
Sometimes in construction it is necessary to reduce the load on supporting structures. For example, a plank subfloor that needs to be leveled with concrete mortar for cladding ceramic tiles. It is clear that the concrete layer has a fairly large weight, which wooden structure may not stand it. In this case, experts recommend using lightweight concrete.
What it is?
This special type concrete mixtures in which porous materials are used as fillers: expanded clay, expanded perlite, foam balls and waste various industries. It is these fillers that reduce the weight of the concrete itself, hence the name “light”.
There is a certain classification of concrete solutions, one of the categories of which divides them by density (and, accordingly, by mass). The density of lightweight concrete with porous aggregates is determined by the range from 500 to 1800 kg/m³ compared to conventional ones, the values of which range from 2000 to 2500 kg/m³.
Properties of lightweight concrete
The main characteristics of the solution are as follows:
- reduced density (mass);
- convenience of construction work;
- getting more economical option by reducing the percentage of cement;
- high strength of the material.
Subtleties of manufacturing
The most difficult thing in preparing lightweight concrete with porous aggregates is to correctly and accurately select the recipe for the raw mixture, especially the water-cement balance. It is this that influences the strength of the material and its convenient use.
The thing is that porous fillers quickly absorb water, leaving practically no water for the cement to set. Therefore, experts recommend selecting the recipe during the production of the concrete solution itself.
Particular attention must be paid to the cement-water ratio, but the porosity of the filler will also have to be taken into account.
Example of recipe selection
There are several options for selecting the density of lightweight concrete. One of them is the preparation of experimental mixtures.
Cement and fillers
To do this, take the standard recipe used for ordinary concrete. This is one volume of cement and six volumes of aggregate. If a combination of two or three types is used as fillers, for example, expanded clay and expanded perlite, then 4 parts are added to the coarse fraction (expanded clay), and 2 parts to the fine fraction (perlite).
Water
It is more difficult with water; here you will have to adjust its quantity to the purpose of the concrete mixture. If the solution will be used for screeding, it is better to make it liquid.
Checking workpieces
Then lightweight concrete is poured into a container, usually a cube. After drying, the workpiece is tested for strength. The same preparations will have to be made from solutions prepared according to other recipes. For example, you can increase the amount of expanded clay or, conversely, perlite, reducing the volume of cement added. In this case, you will have to increase the volume of water.
The strengths of all workpieces are compared with each other. The indicator that meets the requirements of the structure being poured is determined. But the economic component must be taken into account. For example, of two suitable formulations, it is better to choose the cheapest composition.
Classification of mixtures
The classification of lightweight concrete mortars is based on the use of various fillers in the composition and the scope of application.
Simple composition
Ordinary lightweight concrete is made according to the recipe described above. That is, it contains both large and small fillers. In this case, the volume of air between all materials should not exceed 6%.
Porosity
The composition may differ in the nature of porosity:
- Sandless (large-porous) – complete absence of fine filler. Air volume 25%.
- Porous - obtained when added to cement mortar materials that form pores.
Purpose
There is another type of classification based on the purpose of lightweight concrete:
- thermal insulation properties (density 500 kg/m³, thermal conductivity 0.25 W/m*K);
- structural properties (density 1400-1800 kg/m³, strength M15, frost resistance not lower than F15);
- structural and thermal insulation (density up to 1400 kg/m³, strength not less than M35, thermal conductivity - no more than 0.6).
The first group is used for pouring screeds and making heat-insulating boards. The second is used in load-bearing structures. The third is in self-supporting enclosing structures or in load-bearing ones.
Material consumption
As for the consumption of concrete mass, everything will depend on the type of filler used, its porosity and quantity. But there is average value– this is 200 kg per cubic meter. In this case, cement consumption varies from 70 to 150 kg per cubic meter of concrete solution.
Manufacturing methods
Lightweight concrete with porous aggregates is prepared according to different technologies, which depends on the type of additive.
Mixture based on expanded perlite
Making lightweight concrete with your own hands is quite simple. First of all, perlite is wetted with water. It is a hygroscopic material, so it quickly absorbs it. Then 30% of the filler and the entire volume of cement are placed in a concrete mixer. And this solution is thoroughly mixed.
Gradually, water is poured into it, to which plasticizers and modifiers have been added in advance. Thorough stirring should cause the mixture to rise. This is a signal that you can start adding the remaining perlite to it. It is better to do this in small portions.
If you make the solution yourself without using a concrete mixer, then it is better to do it in a clean bucket using a mixer or drill. You can also use a shovel, but the uniformity of the components in the mixture may be low.
Fiber fibers are often added to a mixture of concrete and perlite as a reinforcing composition. They must be added to the concrete when the bulk of the filler is poured.
Composition with expanded clay
First, cement and water are thoroughly mixed until cement laitance forms on the surface. Please note that first water is poured into the container (concrete mixer drum), then cement is poured in portions.
After this, expanded clay is added in portions. Here it is important, as in the first case, to achieve a uniform distribution of the solution components throughout the entire volume.
Foam concrete
Making foam concrete with your own hands is not easy. To do this, you need a foaming agent and a foam generator (special equipment that prepares foam). Let's just designate the production technology.
A solution of sand and cement is prepared in a concrete mixer, into which a certain amount of water is poured.
While the mixture is being prepared, a foaming agent is added to the generator, which turns into foam inside the container. Using sediment, it is added to the semi-finished solution, where pores form. The foam is supplied using a pump.
