Every owner of a private house should know how to prepare concrete - this will help in arranging a house or summer cottage. Often there is no point in ordering just a couple of cubes of factory-mixed concrete, it is simply not profitable. To save money, the solution can be mixed manually and in significant quantities, if the necessary ingredients are available.
Tools
At home, a concrete solution is usually prepared manually for commercial buildings, but when building housing, this procedure must be approached very responsibly.
The main rule for preparing the solution: the grade of cement should be 2 times higher than the grade of concrete that is needed for pouring. Those. if M150 concrete is needed, then the cement must be at least M300.
For pillows under the foundation and preparation of work in dry soils, use a solution of B7.5 (M100) with a rigid consistency. Crushed stone 5–20 mm is used as filler. Stairs, steps are made from the same concrete, but more plastic, fences, paths, etc. are poured. For the same purposes, in wet soils it is recommended to prepare hard concrete B10 - B12.5 (M150). Both the subfloor and paths are made from a mixture of a hard consistency of this brand.
For laying a strip foundation and unloaded parts of a building, a rigid mortar B15 (M200) or B20 (M250) is suitable. It is the same, only a little more plastic, suitable for cesspools, settling tanks, and septic tanks. For the foundation of a good residential building you need to make concrete M300 (B22.5): this will be the best option and crushed stone is better to take fractions of 20–40 mm.
Concrete grades M350 (B25) and M500 (B40) are used for high-rise buildings, heavy-duty structures, storage facilities, laying runways and are not used in home construction - there is no need, and it is difficult to work with such a solution.
To mix the solution you will need:
- trough or concrete mixer;
- shovels;
- hammer (for crushing caked cement);
- buckets;
- sieve for sifting sand;
- containers for washing the filler.
Components
Before preparing concrete, you need to carefully control the quality of the components.
Water
The water should be as clean as possible, without impurities, dirt, clay, or soil. You cannot take wastewater from swamps, stagnant springs, or chemically contaminated wastewater. The solution simply will not set well. On average, water needs half the mass of cement.
Never add water to a ready-made solution.
Filler
There is a fine filler - sand, and a coarse filler - gravel, crushed stone. For light mixtures - expanded clay filler, slag, brick or limestone crushed stone. There is a rule: the strength of a coarse filler is two to three times greater than the design strength of the finished mortar. Crushed stone creates a kind of power skeleton for the mixture.
The filler should be as clean as possible, without soil, branches, soil, and especially clay. It is sometimes washed and sieved at the construction site. Allowable amount of impurities: 35% for crushed stone, 5% for sand. Organic impurities destroy the solution from the inside. It is recommended to sift, rinse and dry the filler before use.
Sand
It is advisable to take coarse sand, it is more versatile. There are 5 groups of sand: from 3.5 mm - with large grains; up to 1.2 mm – fine-grained. Builders recommend the latter only for lightweight concrete.
Checking the contamination of sand: 200 ml of it is poured into a bottle, water is poured, shaken, and poured out. Water carries away impurities, volume loss is more than 5% - poor quality. When mixing, take into account that dry sand contains 1% moisture, after rain - 10%.
The fractions used are small (up to 12 mm, up to 40 mm). Granite screenings or chips are taken for floor screed and non-volume work.
Crushed stone can be:
- granite is the best;
- gravel - standard for private construction;
- limestone - not recommended for buildings, as limestone becomes limp from moisture.
The most popular fractions: 5–20, 5–10, 10–20, 20–40 mm. The size of the material should not exceed a third of the width of the product in the narrowest part and 2/4 of the distance between the reinforcement. Crushed stone larger than 150 mm is not recommended.
It is advisable to use two fractions - fine (at least a third of the coarse aggregate) and coarse - this will make the concrete denser. Pebbles are categorically undesirable: they are smooth and do not bind the solution well. Expanded clay (3–5 cm in size) is suitable for light screeds in houses with wooden floors.
Cement. Rigidity
We will consider the characteristics of cement separately in close connection with the determination of its quantity in the mixture. Proper preparation of concrete is based on a harmonious ratio of components. Concrete must be used all at once - it is never left “for later”, so the amount of mixture must be carefully calculated.
Rigidity
Rigidity is determined by slipping: if the mixture flows from a horizontal plane, it is too liquid, plastic; when sliding when tilting - medium-plastic; if it sticks without slipping, it is low-plastic; does not settle, remaining a lump - hard. Liquid concrete is easier to lay, but hard concrete is better in quality and strength.
The most popular brands of cement for private construction are M400, M500.
Table - Composition of concrete mixture per 1 m3 of concrete:
So, the amount of material M400 for 1 cubic meter of mixture:
- for concrete B7.5 – 180 kg;
- B10 – 200 kg;
- B15 – 260 kg.
The main quantity of cement sold on the market is Portland cement M500. If it is taken, then the above norms must be multiplied by 0.88. This and the following formula will be useful for purchasing the required amount of cement. The length, width, depth of the foundation is multiplied - the volume (cubic capacity) is obtained, based on the above proportions, you can find out exactly how much cement is required.
Nuances
Cement at home is often taken from stale cement, from leftovers from other construction. It must be taken into account that such a material does not have the necessary properties. To prepare the solution, you need dry, not expired material without lumps - this way the concrete will not crack. The shelf life of cement in original packaging is 90 days, in open packaging - no more than a week for dry conditions and no more than a day for wet conditions. The stale material must be thoroughly crushed with a hammer.
To prepare the solution manually, the popular grades of concrete are M100 - M350. All calculations are carried out by weight and are based on the mass of cement. The ratio of ingredients is calculated as their weight ratio to it.
The grade strength of the mortar is determined by the ratio of water and cement (WC). Less water – higher grade. But if there is a lack of it, the opposite effect can occur, so the rule “more cement – better (stronger) concrete” is erroneous. As mentioned above, the grade of cement should be 2-3 times higher than the design grade of the mortar. Knowing the water-cement ratio, you can increase or decrease the grade of the mixture.
Handmade recipe
Let's consider the option of how to prepare a concrete mixture for home construction manually, based on the proportions in the tables. Here are two tables, using which you can determine the proportions and number of components for 1 cubic meter of solution.
Table of water-cement ratio (average indicators of aggregates):
Table - Ratio of water and cement
| Concrete, brand | V/C | |
| Cement M400 | Cement M500 | |
| 100 | 1.04 | - |
| 150 | 0.86 | - |
| 200 | 0.70 | 0.80 |
| 250 | 0.58 | 0.66 |
| 300 | 0.54 | 0.62 |
Calculation of water for filler per cubic meter. m and the percentage of sand in it.
Table - Ratio of sand, crushed stone and water
You also need to know the approximate density of the fillers, weight in kg/m2:
- for gravel filler – 1600;
- for crushed granite – 1500;
- for quartz sand – 1500;
- for expanded clay - 600–800;
- for cement - 3000–3200 (bulk -1300 ÷ 1800).
Preparation of concrete M300 (1 cubic m). Ingredients:
- crushed stone with a fraction of 25 mm;
- medium-grained sand;
- Portland cement M400.
The first table determines W/C - 0.54; the second is the amount of water, with such a filler you need 196 liters. Cement: 196/0.54=363 l. Volume and percentage of filler: 1- ((363/3000)+0.196)=0.680 m3. We look at the percentage of sand according to the second table - 45%, which comes out to 680 × 0.45 = 306 liters of sand. Crushed stone: 680–306=374 l.
The volumes were determined in liters, so you can work with a 10 liter bucket. If the supplier measures fillers in tons, then it is easy to convert them into liters using the above weight-volume density values in kg/m2 (for cement you need to take the bulk density).
Other popular recipes and proportion options
The generally accepted proportions for preparing concrete at home are: 1 (C)/4 (W)/2 (P)/0.5 (V). In weight terms, it looks like this: 300/1250/600 kg, water - 180 liters.
If you take M400 cement, you will get M250 concrete, if you take M500 cement, then you will get M350 mortar. For mortars of low grades, it is necessary to reduce the cement content. For solution B20 (M250) there is another recipe: 1 (C - M500) / 2.6 (P) / 4.5 (Sh) / 0.5 (V) or in kg: 315/850/1050, water - 125 l per cubic meter m.
More proportions (cement: sand: crushed stone; water - half of cement):
- 1:3.5:5.7 – M150 (for floors, paths);
- 1:2.8:4.8 – M200 (fences, foundations of garages and bathhouses);
- 1:1.9:3.7 – M300 (walls, strip foundations);
- 1:1.2:2.7– M400 (very durable, professional, quickly sets and hardens).
Simple secret
There is a simple way to determine proportions. Crushed stone is poured into an empty bucket and distributed evenly. Using a measuring cup (1 liter jar), add water until its level is equal to the edge of the crushed stone. The volume of liquid is the required volume of sand.
Next, the crushed stone is poured out, and in its place the same can of sand is poured in the same amount as there was water. Then water is poured in again until it covers the sand. This is how the required volume of cement is determined. The last component is water, its amount is 50–60% of cement.
The method is based on the principle that sand fills the voids between the crushed stones, and cement fills between the grains of sand. In this case, the strength of the solution will be approximately the same as that of crushed stone. This method does not take into account the expansion of the filler grains or some other parameters, but it is simple and can be used for non-critical structures.
Mixing methods
The preparation of concrete mixture is carried out in two ways:
- manually;
- using a compact concrete mixer (mechanical or automated).
Many people are mistaken in believing that kneading by hand requires a container - no, preparation is carried out using a board made of boards; they also use metal, tin boards, troughs with various materials, the concrete mixture is mixed even just on a flat, hard surface. If the shield is constructed from boards, they need to be tightly fitted and, ideally, covered with roofing iron, although you can simply knead it on a sheet of such iron with the edges slightly turned inward.
First, sand is poured in a heap along the length of the shield, a furrow is made in the center, cement is poured there, the sand is rolled in little by little from top to bottom, stirring gradually. Next, sand and cement are mixed 3-4 times using two shovels, then everything is moistened with water from a watering can and mixed again. Next, gravel is poured evenly, the mixture is stirred at the same time, and water is added little by little until the required consistency is formed.
Another sequence: cement - water - sand - gravel (crushed stone).
There are two types of these devices: with a gravitational or a forced mechanism. The simplest and most accessible first. This is a pear with blades inside, rotating in an inclined position. It takes about 2-3 minutes of rotation to knead.
Preparation is carried out in stages - this way the concrete mixture is well mixed:
- the mechanism always starts empty;
- water is poured in;
- pour half of the cement;
- fill in all the coarse filler;
- add the second half of the cement;
- sand is gradually poured in;
- rotation – 2–3 minutes.
Everything is poured only into a horizontally standing (maximally inclined) bowl. The more horizontal the concrete mixer, the better. After unloading the concrete, the bowl must be washed with water so that there is no frozen solution on it. There are small mechanisms, they are convenient, but they can mix no more than 4 buckets of crushed stone at a time; if you load more, you won’t be able to tilt the bowl, and the batch will be of poor quality.
In winter the order changes: first hot water, then - crushed stone, cement, sand. Potash (potassium carbonate) and antifreeze additives are added to the solution, but you need to know when to stop, they destroy the reinforcement.
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 a ready-made 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, and blind areas. 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 the gradual destruction of the concrete slab. For standard structures, 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 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 at low 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 matters - the higher it is, the less water is 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, lean concrete is made without adding crushed stone; for concreting paths and blind areas, crushed stone of medium and fine fractions is used; for the foundation of a house, medium-fraction crushed stone and high-quality cement are used. The table will help you find out the exact different brands.
Manual method of mixing concrete
Mixing the concrete solution is done manually or in a concrete mixer. If you need to fill a 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
It is difficult for someone who has never dealt with cement to understand what concrete mortar is and how to prepare it correctly. But even experienced builders do not always understand all the intricacies of working with it. In this article we will describe not only the process of preparing concrete mortar, but also the correct selection of its components.
Prepare your own concrete mixture for pouring the foundation, small reinforced concrete structures, the paths are easy. You can knead it in any old bathtub, trough, box or knocked down wooden board. When producing a small amount of solution, the process can be mechanized using special attachments. If you need a lot of concrete, you will have to use an ordinary shovel, small garden fork, hoe or other suitable device for the case. But, before you start mixing, you should choose high-quality cement, crushed stone and sand.
Concrete components
Quality of the main component - cement
The strength of our mortar will be determined primarily by the quality of the cement, so it right choice especially important. There are many factories in Russia that produce similar products, and they usually sell them in neighboring regions. Therefore, you should focus not so much on the manufacturer, but on appearance cement.
You should definitely pay attention to the date of manufacture - over time, its activity decreases sharply. Fresh cement, when squeezed in a fist, does not turn into a lump, but easily spills between the fingers. High-quality, finely ground products lose their properties especially quickly during storage.
When counterfeiting it, dolomite dust, mineral powder, ash and other fillers are used. When they are mixed, naturally, the concrete will not only set more slowly, but after hardening it will also not be strong enough:
- the color of high-quality cement powder is darker;
- the solution from it sticks well and sets quickly;
- the color of dried concrete on the outside is slightly lighter, but if you knock off a corner, its inner surface is dark;
- After complete drying (after a month), it is very difficult to hammer a nail into the finished concrete.
NOTE: You can check the quality of purchased cement as follows. Mix a small portion of concrete in the required proportions, and after hardening, place a chisel on it and hit it with a hammer. On high-quality concrete, after an impact, only a light mark will remain. If the metal breaks off small pieces, the cement grade is 200. Did the chisel punch a half-centimeter hole in the concrete? Cement grade not higher than 100.
The strength of the mortar depends on the brand of cement. When designating it, the numbers after the letter M mean the ability to withstand a load of 1 cubic meter. cm. That is, M200 cement can withstand a load of 500 kg per cubic centimeter. Naturally, the higher the grade, the stronger the concrete will be. Special grades with a strength of 600-700 are rarely used, therefore, when working with complex or multi-tiered structures, it is better to use cement of the M500 grade.
The letters following the numbers indicate the presence of additives in it. For example, the product of the M500 B brand is quick-hardening, VRTs is waterproof, BC is white, intended for finishing. The designation BC20 will mean that it contains 20% brightening impurities. The most important additive for us - PL - makes it frost-resistant, so it is advisable to use it for street work, especially in the conditions of Siberia and the North.
At long-term storage The cement powder cakes, becomes compacted and its specific gravity increases. Therefore, if you bought it in advance, be sure to store it in a dry, draft-free place. It is advisable to additionally wrap paper bags with plastic wrap. Please note that after six months of storage, its quality will decrease by at least a third.
Which sand is better
The best sand is river sand. It is washed with water and, unlike quarry, does not contain impurities. When working in winter, it is better to use river water, completely free from clay inclusions. At sub-zero temperatures, their lumps do not dissolve well in water even with prolonged stirring, and the concrete surface will be uneven.
Selection of crushed stone
Dolomite and limestone crushed stone are most often used to create small, lightweight structures, the quality of which is not subject to increased requirements. Gravel or granite material is more durable and can withstand the coldest temperatures.
IMPORTANT: When purchasing, you should remember the most important rule. Dirty crushed stone or sand are the main enemies of good, high-quality concrete.
Let's prepare the solution
The proportions of the mixture directly depend on what brand of concrete (that is, what strength) we need. The most common proportion when using the M500 brand is 1:2:3 (i.e. you will need part cement, two sand and three crushed stones). The higher the grade, the less cement is used. Therefore, the proportions for the M350 will be different. In any case, the ratio of water and cement should be no more than 0.5.
Table - Concrete made from M500 cement
Required grade of concrete | Proportions of cement, sand and crushed stone (CxPxShch), kg | Concrete yield from 10 liters of cement |
To make a garden path, M200 concrete and small fillers (pebbles or crushed stone) are sufficient. Good and durable asphalt will be obtained from grades 300 and higher. The foundation naturally requires a more durable structure. Ideal option will become M500. On average, one cubic meter of mixture will require 6-7 bags of M500 cement.
IMPORTANT ! Remember that the prepared mixture hardens very quickly, so it must be used within half an hour. Under no circumstances should you try to dilute it with water once it has hardened.
To avoid the formation of unmixed lumps, water is added only after mixing the cement with sand. The mixture for plastering work must be sifted through a sieve with mesh sizes of 5 mm; for ordinary work, larger meshes can be used.
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 kitchen table tops.
Distinctive characteristics
Thanks to modern technologies, allowing you to make concrete of very high quality, this artificial material In terms of its strength, it 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 latest technologies processing.
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 total 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 - crushed rock, having 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 liquid solution you need, add 0.5-1 part of 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 regulatory documents, attached to 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 for construction 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 do strip foundation, please note 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 must 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.
Instructions on how to mix concrete are necessary for anyone doing construction or repairs.
After all, even the most modest construction cannot be carried out without a foundation.
The main components of the foundation of a building are concrete and reinforcement.
These components allow the construction of impeccable architectural structures that can withstand excessive loads, strong winds and vagaries of weather.
Concrete is made from dry ingredients.
The mixture can be stored in a closed container for a long time without adding water. But before use, water is added to the concrete components.
A self-made solution hardens in a couple of hours, so it is better to use it right away. The foundation concrete turns to stone, providing strength to the foundation.
It is worth making concrete with your own hands when building the foundation of a frame house and concrete stairs.
Frame structures do not need a massive foundation, since they are not heavy in weight. Just before doing this, you need to find out how many and what ingredients you need.
The main components of concrete mortar are water and cement that bind all components. They are supplemented with crushed stone and sand.
Powdered cement is made from ground limestone, chalk, gypsum and marl. Cement dust is harmful when inhaled as it settles in the lungs.
Contact with cement may cause skin irritation. Therefore, all construction operations with cement are carried out with gloves and a respirator.
Cement grades differ in strength; the higher this indicator, the higher the number in the name.
Popular brands – M400, M500. The volume of the components of these mixtures is one to four and one to five - for one part of cement there are four or five parts of sand.
Natural raw material - sand, is classified according to the degree of granularity, it can range from 0.5 to 2 millimeters.
Sometimes a little clay is poured into the sand to make the future solution more viscous. Sand with an excess of clay must be cleaned with water and dried.
Crushed stone is produced by grinding granite to five-millimeter particles. As a component for concrete mortar, it must be washed and free of clay and soil.
The main condition for the water that will be used for mixing the mixture is purity. That is, it should not contain salts and acids that can change the characteristics of the solution.
To improve quality performance characteristics sand concrete, additives are used. Some modifiers affect plasticity and fluidity.
Others slow down the curing process, which is necessary in hot weather. Still others provide increased water resistance or protect against low temperatures.
Since the fate of the entire future construction depends on sand concrete, it is important to know how much to use of certain components and in what order they should be mixed in order to properly prepare the liquid composition with your own hands.
Preparing concrete by hand
Concrete for pouring a stepped foundation is very easy to prepare by hand if you have a small construction area.
Factories producing construction mixtures do not deliver to the site a product less than one cubic meter of concrete.
The best solution would be to make concrete yourself if pouring occurs periodically, as happens when forming a pile-beam foundation.
You can also do this in conditions of great distance from the manufacturer and inaccessibility of access to the construction site of the automixer.
The process of making concrete for a foundation or other purposes with your own hands is not simple, so it must be done in parts, alternately mixing the necessary ingredients.
To properly knead manually, you must first make “ballast”. It is important to calculate how much ingredients to take.
Ballast is prepared from stone chips and sand in a ratio of 3:1. You can take a bucket for one serving.
For kneading, prepare a deep container and a shovel. In the old bathtub that everyone has summer cottages, holds less than one cube, approximately 0.3.
But if the construction is small, a basin and a trowel will suffice.
1 part of cement and 5 parts of ballast are combined in a container, mixing thoroughly and achieving homogeneity of the mass. Basically, these proportions are observed, but sometimes only cement is used.
To make the concrete more durable, use cement grade M500. Of course, the higher the grade of cement, the more expensive it costs.
If we talk about how much cement it is advisable to buy, then a bag weighing 50 kg is the most optimal option.
I make a hole in the center of the resulting mixture and pour a little water into it by eye. Stirring is carried out from the walls of the container to the middle, where the water is.
When combining the dry mixture with water, you need to reach to the bottom to thoroughly mix the components.
After preparing the composition by hand, pay attention to its consistency. If the proportions are chosen correctly, the solution will be liquid, but not flowing.
An overly liquid mixture will lose its strength properties. Excessive density will also negatively affect the quality of construction.
Checking the consistency is simple. Use the blade of a shovel to cut out a small square section in the concrete. Then they monitor its edges. If they crumble, then not enough water has been added.
If water seeps through the concrete composition made by yourself, then there is too much of it. It is necessary to additionally mix the concrete and add it to the previously prepared composition, mixing thoroughly again.
Note: water is poured into the prepared powder mixture. This sequence of actions when mixing sand concrete with your own hands prevents the appearance of lumps.
Concrete of the correct consistency should be easily lifted out of the container with a shovel, and not uprooted with great force.
At the end, plasticizers and crushed stone are added as needed to improve the properties. Do-it-yourself concrete mortar is delivered to the construction site in buckets.
In the case of large-scale construction, making sand concrete manually will become a grueling process.
You can quickly get concrete without wasting effort using a concrete mixer.
Making concrete in a concrete mixer
Nowadays there are many machines that can facilitate the production of concrete. It is easier to prepare the composition in a concrete mixer than to produce it in parts for large volumes of construction.
How much material will be needed? If we convert the proportions into kilograms, then a cube of sand concrete will need 300-350 kilograms of cement.
Also, for a cube of popular building material you will need to spend 600-700 kg of sand, 1100-1200 kg of crushed stone, and 150-180 liters of water.
The difference in each proportion is due to the unequal quality of the ingredients. For example, crushed gravel is characterized by a higher strength index than limestone.
That is why it is customary to use it in smaller proportions.
To make a cube of construction raw materials, it is easier to use buckets. If you pour components into buckets, you need to know that they do not have the same weight.
For example, cement in one bucket weighs about 16 kg, and gravel weighs about 17 kg. So, when measuring the proportions in buckets, they proceed from the ratio: 9 parts of gravel, 5 parts of sand, 2 parts of cement.
The solution is prepared correctly in a concrete mixer as follows. The bulb of this apparatus is installed at a 45-degree angle. Pour sand inside.
We load the cement into the concrete mixer gradually, turning on the mixing mechanism after the next addition.
After mixing sand and cement in a concrete mixer, water is poured in portions. Adding a certain amount of water little by little, turn the concrete mixer.
The next component that needs to be added to the mass in the concrete mixer is crushed stone. It also needs to be added in small batches to ensure even mixing.
Although, when making a construction product in a concrete mixer, you can deviate a little from the strict sequential mixing procedure, as when working with your own hands, but be sure to maintain all proportions.
Allows you to put all the components into the device at once: half a bucket of water, four buckets gravel mixture and one bucket of cement.
Without stopping the kneading progress, add two more buckets of water. The solution should be swirled in a concrete mixer for a couple of minutes. The consistency of prepared concrete is compared to liquid clay.
Other options
If you understand that you will not be able to prepare the foundation for pouring the foundation of a frame house or other small structures with your own hands, then seek the help of professionals.
Without racking your brains over how many components to take and how to mix them, you can buy a cube of concrete, which should be enough for a small construction project.
A cube of this construction product costs from 2,400 rubles. This figure applies to the lowest grade. A medium-strength cube (M400) costs from 3,200 rubles. The most expensive and reliable brand is M600.
A cube of such concrete will cost 4 thousand.