Proportions for preparing concrete mixture at home

Is there a universal proportion for mixing concrete? Common recommendations “three parts sand to one part cement” or “part cement, 4 parts gravel, 2 parts sand, 1/2 part water” will produce a “certain” cement mortar. However, if it is necessary to make high-quality concrete with brand (or almost) characteristics, then a professional approach is needed to the proportions.

To make concrete, cement, crushed stone, sand and water are mixed in the correct ratio. Cement plays the role of a binder and hardener, crushed stone and sand increase strength, and water provides plasticity and facilitates mixing.

Speaking of proportions, it’s worth starting by analyzing the components of the concrete mixture.

Concrete is used to make large multi-storey buildings, paths and small sculptures

Concrete composition: components, dimensions and characteristics

Most concrete consists of three main components:

• The binder is most often cement, sometimes lime.
• Fillers - sand, crushed stone, pebbles.
• Water.

Different amounts of just three components give a wide range of qualities and characteristics. To impart special properties, various additives are still used, which further expands the scope of application of this material.

All these brands of concrete are made from the same components, but in different proportions

The main characteristic of concrete is its strength or load, which it can withstand for a long time without losing its strength characteristics. This is a key parameter when choosing a concrete grade for the foundation. Water permeability and frost resistance are also important. But these are the characteristics of the “ripened” material, which depend on the recipe. And when mixing, you may be interested in characteristics such as workability. It reflects the degree of concrete fluidity and depends on the amount of water in the composition. You can increase fluidity without adding water using additives, as well as increase frost resistance and water-repellent properties.

The strength of concrete depends on how accurately the recipe was followed, on the quality of the ingredients and on how thoroughly everything was mixed. Only with a homogeneous composition and high-quality components can design characteristics be achieved. Read more about what components can be used and the requirements for them at the end of the article.

Calculation of the required number of bags

Based on the above calculations, the amount of cement can be determined.

How many bags of cement are needed depends on how the manufacturer packages it. Cement can be sold in bags of 50 kg and 25 kg. In the latter case, the above number of bags is doubled.

How much cement needs to be added depends on what the concrete will be used for and how much mortar is needed. The project usually indicates how much concrete is needed, so you can calculate the proportion taking into account this figure, determining the amount of cement and other materials.

Principle of concrete marking

The main characteristics of concrete are its strength and compressive class. The compression class is indicated by the letter “B”, followed by class numbers from 3 to 40, the strength grade is indicated by the letter “M”, followed by numbers from 50 to 1000. They indicate the maximum load that this type of concrete can withstand. For example, the M300 brand means that the maximum load per 1 cm² cannot be higher than 300 kg.

In private construction, the most popular grades are M200-M250; for the foundations of two-story houses, M300-M350 concrete can be used; M400 is much less often poured - for heavy buildings on difficult soils. Higher ones are generally rare. Their area of ​​application is industrial construction and objects with special properties (piers, dams, roads, etc.).

The correspondence between concrete grades in terms of strength and compression is given in the table (used in private construction).

Specifications

Concrete grade 500 presupposes certain properties and indicators that the material must meet. Many parameters are significantly superior to the more popular cement brands in repair and construction work: M200 (concrete is not the strongest), M300 (concrete with average characteristics), M400.

Production of concrete mixture.

Main properties of M500 concrete:

• Strength - class B40, 51.73 MPa (the solution can withstand a load of 523.7 kilograms per cm2)
• Resistance to temperature changes – F200-F500
• Mobility (concrete on granite) – P2-P5
• Water resistance – W10-W16 (construction of structures to be used in water is allowed)
• Standard density of concrete M500 – 2298 kg/m3
• Weight of a cubic meter – 2298 kilograms
• Hardening time – 1-2 hours

Proportions of concrete of different grades

This entire range and range of qualities is obtained by using the same materials, just in different quantities. To achieve the required characteristics, the recommended proportions must be strictly observed.

When building your house, you want to do everything as best as possible, and therefore, when making concrete, you want to add more cement to make it stronger. This should not be done. It's unlikely to get better, but it could easily get worse. To gain strength, concrete needs a certain amount of water and other components. If there is little water, there is a lot of cement, bonds between particles are formed in insufficient quantities, which is why the concrete can crack and crumble. The same applies to the number of fillers. Both their too high and insufficient content negatively affects the qualities of concrete stone.

Concrete proportions are usually displayed in fractions. The amount of cement is taken as a unit, and the remaining components are prescribed in relation to it. The data is presented in the form of tables for the corresponding brands; the units of measurement must be indicated. You can see such a table of concrete components below.

Proportions of concrete of different grades from Portland cement M400 and M500

How to determine the required proportions of concrete using this table? In the second column, find the required grade of concrete. For example, you need an M250. Depending on which Portland cement you will use M 400 or M 500, choose one of two lines. The third column shows the proportions for concrete in kilograms: for 400 cement it is 1/2.1/3.9. This means this: to obtain concrete grade M 250, for 1 kg of Portland cement M400 you need to add 2.1 kg of sand and 3.9 kg of crushed stone. Similarly, determine the proportions for concrete M200 - the data for it in the table is slightly higher, or concrete M 300 - slightly lower.

The fourth column presents volume fractions: all components are given per 10 liters. They are selected in the same way.

Such tables do not indicate the amount of water. It depends on how thick the solution is needed. The water-cement ratio is given in separate tables. For example, below are data on the number of inputs in relation to a kilogram of cement, provided that medium-sized aggregates are used.

The amount of water to obtain concrete of the required grade when using medium-sized crushed stone and sand

For example, to obtain concrete grade M 300, the proportions of cement M 500 and water are defined as 0.61. This means that for 1 kg of cement, 0.61 liters of water (610 ml) are added to the solution. This produces a medium-plastic solution, which is used most often. >But when pouring foundations or other structures with dense reinforcement, a plastic solution may be needed. Then, when determining the amount of water, in addition to the brand of cement, it is also necessary to take into account the size of the aggregates and how fluid the solution should be. These data are presented in the table below.

The amount of water in concrete depending on the size of crushed stone/gravel and the fluidity of the solution

Sometimes it is necessary to determine how much cement you will need for a particular task. To do this, you need to know how much cement is contained in a cubic meter of concrete. Data on concrete and cement grades can be found in the table below.

Amount of cement per cube of concrete

Why should the grades of material and construction mixture be the same?

To obtain a solid masonry brick wall or foundation, it is necessary to match the brand of the finished product with the brand of the building mixture. If you use M100 brick during construction, then the building mixture should be of the same brand. As a result, the finished structure will be homogeneous and durable.

dilute the cement

For greater strength, when using M350 brick in construction, it is not necessary to prepare a mortar of the same brand; the use of PC115 will be sufficient. Cement and sand should be diluted in a ratio of 1 to 3.5, because Even for tiles, a solution of 1 to 7 is used.

Material consumption rates for preparing concrete 0.2 m 3

It is necessary to warn novice masons: it is not recommended to change these proportions. When they are reduced, for example, 1 part cement to 3 parts sand, the mixture becomes too fast-acting and it becomes impossible to work with it. When the proportions increase, for example, 1 part cement to 4 parts sand, the strength of the mixture decreases, so there is a high probability of it crumbling.

Areas of use

We have decided what materials are required for concrete in what proportions, but what brand is needed? This depends on the purpose of the structure and its operating conditions. It will be easier to navigate if you know which grades of concrete can be used for what (let’s name only those that are used in the construction of a private house, its renovation or landscaping).

M100 (B7.5). This is the so-called lean concrete. It is used to prepare sites for critical structures. For example, when building a strip foundation, a layer of lean concrete is laid on a gravel-sand backfill, and then reinforcement work begins. The same composition is used when laying curb stones, for example, when making paths or blind areas around the house.

M150 (B12.5). This composition is used in preparation for slab foundations, for screeds, pouring concrete floors or garden paths. This type of concrete can be used to make foundations for small lightweight buildings such as a wooden bathhouse or a small guest house made of timber or logs.

M200 (B15). One of the most popular brands of concrete. It is used to make foundations of any type for light houses on normal soils, screeds, stairs, blind areas, paths. Cement blocks are made from this brand of concrete at home, and it is also used in factories for the production of foundation and building blocks.

The ratio of cement and sand for concrete affects the strength characteristics

M250 (B20). The scope of application is almost the same, but in more difficult conditions. They make any foundations on difficult soils, or on normal ones, but for houses built from heavy materials. They make blind areas that will be used as paths, external stairs, concrete porches, fences, etc. It is also used to make floor slabs for light loads.

M300 (B22.5). Also suitable for all areas listed above, but under even more severe operating conditions. They make foundations for heavy houses on heaving soils, make monolithic walls, paths, waterproof blind areas, etc. This brand of concrete is mainly used to make floor slabs and grillages for pile-grillage foundations.

M350 (B25). The strength of this brand for private construction is generally excessive. This concrete is used for the construction of monolithic pool bowls or for the manufacture of foundations at high groundwater levels, for other structures that require high water resistance. This brand is already more often used in industrial construction.

M400 (B30). This is already an expensive brand of concrete, which is used in facilities with special requirements: for large swimming pools, dams, bank storage facilities, etc.

How to prepare 500 grade concrete yourself

To prepare a high-quality solution, you need to know the ratios exactly. The proportions of M500 concrete may depend on the type and quality of the material and change accordingly. But it is still better to adhere to the standards so that instead of the required mixture you do not end up with a mixture of the M350 brand (concrete with average performance) or M450. Indeed, when constructing structures that will withstand enormous loads and difficult operating conditions, even a small deviation from standard indicators can be disastrous.

Proportions of concrete M500 (1:1.1:2.2:0.5):

• Cement – ​​10 kilograms
• River sand – 11 kilograms
• Crushed stone – 22 kilograms
• Water – 5 liters

This ratio is considered the most optimal for preparing M500 concrete. It is almost impossible to make such concrete at home - so, if M400 (concrete also with fairly high characteristics) can still be prepared at home, then M500 is better to order at the factory. When ordering a dry mixture, you also need to carefully select a supplier, making sure that he has the equipment necessary for the production of the material and all quality certificates.

Otherwise, you can buy a mixture that, according to regulatory parameters, will correspond to much lower grades and, under certain conditions, will lead to deformation of the structure, demonstrate strength class B22-25 instead of B40, and provoke other problems, which is simply unacceptable.

Concrete M500 is a strong and durable material that is quite expensive. Therefore, it is usually used where there is a need for increased parameters and improved properties, which fully justifies the high price.

Preparation of concrete

For large volumes of work, it is better to order concrete from the factory. Making large quantities of mortar by hand or even using concrete mixers is a difficult task, and laying it in batches requires additional effort to ensure that the layers adhere well. However, you can prepare concrete manually. In this case, there are two sequences of actions:

1. First, concrete and sand are mixed dry. It is mixed until the color becomes uniform. Then crushed stone is poured in, everything is mixed again, and water is added last.
2. First, water is poured into it and cement is poured into it. When everything is mixed, add sand and then coarse aggregate.

The order of adding components for concrete during mixing may be different.

In the first option, there is a possibility that during manual mixing, unmixed composition will remain at the bottom, near the walls of the container, which will lead to a decrease in the strength of the concrete. The solution is to mix everything well and thoroughly. But you can’t spend too much time on this: the solution will begin to set.

The second option has its disadvantages: obtaining a homogeneous cement laitance (a mixture of water and cement) sometimes takes a lot of time. As a result, there is simply not enough of it to form bonds with the backfill: the cement “seizes” and the strength of the concrete also decreases.

All this is not so critical when using concrete mixers, but it is also not ideal. There is another difficulty here. Concrete is usually delivered to the construction site in carts. The entire volume does not fit into one, and the remainder is left to spin in a concrete mixer. This is better than leaving it just standing, but if you mix it too long, the solution may begin to delaminate, resulting in lower concrete strength. The solution is two carts and two people to carry them. The filling method - first or second - choose for yourself.

For small volumes, concrete can be mixed by hand

So after all, how to prepare concrete. The choice is yours. If the volumes are small, you can knead by hand. Just do it carefully. To pour the foundation, it is better to order a mixer, but you can also use a concrete mixer (or two, depending on the volume). And to solve problems with the heterogeneity of the mixture (although it is better that it is good), treat the concrete being laid with a vibrator. Most of the problems will go away.

Next, we will talk about the requirements for concrete components, their sizes and qualities.

How to calculate and find out the volume of concrete

The actual amount of concrete used is measured in cubic meters. to calculate the amount of concrete for the foundation .

To calculate the volume of concrete and formwork, we multiply its depth by its width and length. This result is the amount of concrete required for pouring.

To calculate the proportions of components (cement, sand, crushed stone, water) for preparing concrete , you should refer to the following “recipe”.

If you need to prepare 10 cubic meters of concrete, and M500 grade cement is used for its production, then you should take 1 part cement, 2 parts water, 4 parts crushed stone. From the resulting seven parts, 10 cubic meters of ready-made concrete will be made, which means 10÷7 = 1.42 m3. This volume accounts for each part of the concrete components. Respectively:

1. sand 1.42 m3 × 2 parts = 2.84 m3;
2. cement one part, 1.42 m3;
3. crushed stone 4 parts 1.42 m3 × 4 = 5.68 m3.

Approximate weight of materials (kg/1 m3): cement – ​​1500, sand – 1800, crushed stone – 1400.

The optimal amount of water is half the volume of cement used to prepare concrete (in this case, ½ part). More water will result in a worse consistency of the mixture.

Requirements for cements for concrete

For most construction work, cement concrete is used, where Portland cement is used as a binding component. There is also limestone, but its scope of application is limited mainly to finishing work, which is done “the old fashioned way.”

Types of Portland cement and their storage

There are several types of Portland cement: Portland slag cement, aluminous cement and pozzolanic cement. They all differ slightly in characteristics, but any are suitable for private construction. The difference can only affect the setting time: slag Portland cement takes the longest to harden - up to 12 hours, followed by standard Portland cement - up to 10 hours, and aluminous binder hardens the fastest - no more than 8 hours.

Cement for concrete must be dry, free-flowing and fresh

Cement is demanding on storage conditions, and especially humidity. For the manufacture of important structures - foundations, floors, etc. It is advisable to use fresh one, recently released from the factory. Within a month it loses up to 10% of its properties, and after 6 months they deteriorate by 30-35%. Therefore, for example, when pouring a foundation, it is better to take it a maximum of two weeks ago and purchase it shortly before use.

Store in a dry, ventilated area. If there is no room, they are stored under a roof or wrapped in several layers of film to protect them from moisture. Please note - wrapped, not covered. And preferably not on the ground, but on a wooden floor. The thing is that when moisture gets in, even in a vapor state, the cement becomes lumpy, which greatly worsens the characteristics of concrete. If there is an abundance of moisture, it simply becomes a stone and there is no way to use it. Therefore, take care of a place to store cement in advance.

Cement marking

What brand of cement should be used is usually indicated in the concrete recipe. It is designated by the letter M and numbers that indicate the maximum concrete strength that can be achieved with this binder. For example, with M400 grade cement you can get maximum concrete grade M400, as well as lower ones.

Next comes the letter “D” and numbers indicating the amount of impurities. M400 D15, means that there are 15% impurities in the binder. For construction work, this figure should not be more than 20%.

Maturing of concrete and gaining proper strength

Traditionally, all work with concrete is carried out in the warm season at above-zero air temperatures. In this case, water reacts with cement and the composition hardens qualitatively. When pouring concrete in cold weather, water can turn into ice, which will cause the bud to lose strength and collapse from the inside.

The concrete “sets” within 12 hours, hardens during the first week, after two weeks the concrete gains almost 80% of its strength, and becomes fully ready for use only after a month (provided the ambient temperature is about 20°C). If you used special types of quick-hardening concrete for pouring, the “maturation” period may be shorter.

Fillers - crushed stone and sand

The composition of concrete is determined by the functions and characteristics of concrete that are necessary during its operation. The most common are sand and crushed stone. They are subject to no less stringent requirements than the quality of cement. Sometimes pebbles are used, but only if they have sharp edges and not round ones. In the presence of broken lines, the adhesion of the aggregate to the solution is better, as a result, the strength of the concrete is much higher.

Sand

Construction sand can be river or quarry sand. River water is more expensive, but it is usually cleaner and has a more uniform structure. It is best used when preparing concrete for pouring foundations and screeds. For masonry or plastering, it is appropriate to use cheaper quarry sand.

In addition to its origin, sand is distinguished by fractions. For construction work, large or medium ones are used. Small and dusty ones are not suitable. The normal size of sand grains is from 1.5 mm to 5 mm. But optimally in solution it should be more homogeneous, with a difference in grain size of 1-2 mm.

The sand must be clean, preferably with the same grain sizes

The cleanliness of the sand is also important. It should definitely not contain any foreign organic inclusions - roots, stones, pieces of clay, etc. Even the dust content is standardized. For example, when mixing concrete for a foundation, the amount of contamination should not exceed 5%. This is determined empirically. 300 ml of sand is poured into a half-liter container, everything is filled with water. After a minute, when the grains of sand settle, the water is drained and refilled. This is repeated until it is transparent. After this, determine how much sand is left. If the difference is no more than 5%, the sand is clean and can be used when mixing concrete for the foundation.

For those jobs where the presence of clay or lime is only a plus - when laying or plastering - there is no need to take special care of the cleanliness of the sand. There should be no organic matter or stones, and the presence of clay or lime dust will only make the solution more plastic.

Crushed stone

For critical structures - floors and foundations - crushed crushed stone is used. It has sharp edges that adhere better to the mortar, giving the structure greater strength.

Crushed stone fractions are standard:

• extra small 3-10 mm;
• small 10-12 mm;
• average 20-40 mm;
• large 40-70 mm.

In the batch, crushed stone is used in several fractions - from small to coarse

Several different fractions are used simultaneously in concrete. The largest fragment should not exceed 1/3 the size of the smallest element of the structure being poured. Let me explain. If a reinforced foundation is being poured, then the structural element that is taken into account is the reinforcement. Find the two elements closest to each other. The largest stone should not be more than 1/3 of this distance. In the case of pouring a blind area, the smallest size is the thickness of the concrete layer. Choose crushed stone so that it is no more than a third of its thickness.

Fine crushed stone should be about 30%. The remaining volume is divided between medium and large in arbitrary proportions. Pay attention to the dustiness of the crushed stone. Lime dust is especially undesirable. If there is a lot of it, the crushed stone is washed, then dried, and only then poured into concrete.

Aggregate storage

It is clear that a construction site is not the cleanest and most organized place, and sand and crushed stone are often dumped directly onto the ground. In this case, when loading, you must ensure that no soil gets into the mix. Even a small amount will negatively affect the quality. Therefore, it is advisable to pour aggregates onto solid areas.

It is also necessary to protect them from precipitation. In concrete formulations, the number of components is given based on dry components. You learn to take into account the moisture content of components with experience. If you don’t have one, you have to take care of the condition and cover the sand and gravel from rain and dew.

Components

Before preparing concrete, you need to carefully control the quality of the components.

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.

Mixing methods

The preparation of concrete mixture is carried out in two ways:

• manually;
• using a compact concrete mixer (mechanical or automated).

Manual kneading

Many people are mistaken in believing that mixing by hand requires a container - no, preparation is carried out using a board made of boards; they also use metal, tin boards, troughs made of 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).

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.

For reinforced structures, not very hard concrete with fine and medium aggregate is recommended.

Cement

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.