What kind of concrete is needed for floors (concrete for floor screed)

Concrete is considered the most versatile material in construction. What brand of floor concrete should be used for arranging the foundations will be discussed below. Concrete floors are found in premises of various purposes: from garages to commercial and industrial facilities. The requirements for the floor base vary. And they are determined primarily by the load capacity. Because in some situations you need the ability to withstand fairly high loads. For example, in some places the concrete for the floor must be such that the floor can support a stacker with a total load of 10 tons. In other areas, the wear resistance of the coating is preferred.

Concrete floors are very popular due to their strength, durability and reliability.

The grade of concrete for pouring floors is usually selected based on a criterion such as compressive strength. Brands and classes depend on this parameter. Class means the level of guaranteed strength.

For floor screeding in an apartment, the choice of specialists stops at the grades of materials M100 (150) and M200. Grade M100 is used as concrete preparation for installing a reinforcement cage or during the construction of a foundation. It often finds its application in the construction of sidewalks and curbs. Suitable for installation of “warm floor”. The M150 brand is used in individual housing construction. Its use is acceptable in the absence of chemically aggressive substances.

Concrete floors: description

Concrete floors are a mixture of cement, fillers (sand, crushed stone, expanded clay, broken brick, etc.), and water. The proportions of the mixture vary depending on the different needs for the grade of concrete. Concrete grades, in turn, differ in strength and degree of frost resistance.

It is believed that concrete is the most practical material for subfloors. Concrete floors can withstand enormous mechanical loads and pressure, therefore they are often used in technical premises, such as production workshops, automobile service stations, various hangars, warehouses, etc.

Concrete floors are also laid in residential areas. In private housing construction, for example, concrete floors strengthen the entire foundation and give strength to the entire area of the room.

Concrete mix composition

Benefits of concrete floors

Fireproof.
High strength.
Do not require special care.
Easy to install.
Not afraid of mechanical and chemical influences.
Very long service life.
Not prone to the growth of fungus and mold.
Ideal base for ceramic tiles, parquet, laminate, carpet, etc.
High moisture resistance.
Over time it does not lose its properties.

Disadvantages of concrete floors

Large energy costs for installation and dismantling of the coating.
In residential premises it is necessary to lay additional covering on a concrete base.
Concrete floors are quite cold due to the high thermal conductivity of the material.
It is necessary to take into account the strength of load-bearing structures when installing a concrete floor in multi-story buildings due to the large weight of concrete.
Preparing to lay a concrete floor takes a lot of time.
It takes a long time for the concrete mixture to completely harden. The hardening time of standard concrete mixtures is about one month, but can vary significantly depending on the additives introduced.

What brand of concrete is suitable for the floor?

Concrete floors are very popular due to their strength, durability and reliability.

Floor screed type

The floor screed can be monolithic, sectional or floating.

Monolithic floor screed . Filled with one layer without the use of sound, heat, or waterproofing materials.
Sectional filling method. The concrete screed must be poured in a single layer, but there are situations when this is not possible due to the large volume. In such cases, the floor area is divided into sections and poured sectionally.
Floating floor screed. This type of screed does not come into contact with the walls and subfloors. A small distance between the screed and the walls serves as an expansion joint and is filled with any insulating tapes. Between the floating and rough screed, as a rule, sound, heat, and waterproofing materials are laid.

Requirements for industrial floors

Due to the specific nature of the operation of industrial floors, they are subject to special requirements:

strength;
wear resistance;
durability while maintaining qualities important for operation;
resistance to temperature changes;
resistance to humidity;
chemical resistance;
abrasion resistance;
tightness;
no dust;
fire safety;
antistatic properties.

Important!
Requirements for industrial floors are regulated by special documentation.

Floor screed thickness

There are several options for the thickness of the floor screed.

Screed up to 2 cm . This is basically a self-leveling mixture, or concrete for final leveling of the surface. Poured without the use of reinforcing materials.
Not less than 4 cm. It is believed that the minimum thickness of the rough screed should be no thinner than 4 cm, regardless of whether reinforcing material is used or not.
Screed up to 7 cm. In this version of the screed, reinforcement or reinforcing mesh must be provided.
Screed up to 30 cm. This screed thickness is used in production workshops and industrial premises. Pouring more than 30 cm of screed is not economically profitable; there will be no benefit from a thickness of more than 30 cm, but the material consumption and cost of work will increase significantly. It is advisable to use bedding to reach a screed thickness of up to 30 cm.

Characteristics of brands

Brand M150 is recommended for pouring foundations for fences or car parks. Therefore, such concrete is suitable not only for making screeds in an apartment, but also for arranging the floor surface in a garage, provided there are no significant loads.

Table of grades and classes of concrete.

Concrete for floors M200 is usually classified as medium-strength materials. Which is standardly equivalent to class B15. This is the best option for screeding. The duration of use is decades.

In the production of floor mixtures, in some situations grades M250 and M300 may be required. The grade of concrete M250 is resistant to the influence of precipitation and can withstand groundwater.

The leader among other brands of concrete for flooring is M300. This material is distinguished by high setting speed and wear resistance, increased moisture and frost resistance. The strength properties of M300 make it possible not only to use it for floor leveling, but also to use such concrete in road construction.

Professionals do not consider the use of highly resistant brands M350, M400 to be profitable in private housing construction. Therefore, the demand for these brands remains at a fairly low level.

Concrete screed for heated floors

Warm floors can be electric or water.

Water heated floor.

For a water heated floor, the thickness of the screed should be at least 30-35 mm above the upper edge of the pipe, optimally 40-45 mm. It is advisable to use the grade of concrete M 300 and class B 22.5. This thickness of concrete is recommended for use in residential premises using water-heated floors.

Electric heated floor.

It is poured with a layer of at least 30-35 mm , up to 40-45 mm, concrete grade M 300 and class B 22.5. For water and electric heated floors, a plasticizer is added to make the concrete elastic.

Order a solution to fill the floor or mix it yourself

In order for the floor to be reliable and to avoid the formation of voids and cracks, most often a ready-made solution is ordered. In the factory, you can maintain the correct proportion of components, add plasticizers and other necessary substances, and achieve ideal homogeneity of the solution. These factors greatly influence the quality of the future floor, and only if all the nuances are followed will it be possible to achieve a perfectly flat floor.

In addition, most often the floor is poured immediately, without dividing this work over several days. In this case, delivery of the ready-made solution will be more convenient and make the work more efficient.

Types of concrete mixtures

A concrete mixture is a finished product manufactured primarily at a factory in compliance with technology. This mixture is called BSG , which means ready-mixed concrete. BSG includes various types of concrete, which differ in volumetric weight.

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BST . The concrete mixture is heavy. Gravel, crushed stone, and granite serve as fillers for the mixture. It is used in the construction of industrial facilities, for the installation of rough screed. Density 1800-2500 kg/m3.
BSM . The concrete mixture is fine-grained. Heavy concrete using fine filler fractions up to 5 mm. The maximum density of the mixture is ensured by cement containing alite. Used for the construction of thin-walled structures and rough screeds. Unlike BST, it has better filling of cavities. Density 1800-2500 kg/m3.
BSL . The concrete mixture is light. This type of concrete is lightweight due to the low weight of the fillers. Mostly, the filler is expanded clay or some other porous filler. Such concrete has good sound and heat insulation properties. Density 500-1800 kg/m3.

Finishing

An important stage in the installation of an industrial concrete floor is finishing, which allows both to impart special strength to the floor and to create decorative effects (colored, mosaic floors, imitation marble or stone). The installation of industrial concrete floors without additional processing is now rare.

Finishing can be of the following types:

self-leveling floor;
coloring;
application of polymer coating;
topping.

Let's look at these types of processing.

Self-leveling floor

The floor is filled with an additional layer, which levels it, hides minor defects, providing a smooth surface without seams. The self-leveling floor is very resistant to both abrasion and stress, as well as water and aggressive chemicals, and it can be made aesthetically attractive.

Coloring

This option allows you to achieve the desired decorative effects and obtain floors that meet strict hygienic requirements, but is only suitable for rooms with low mechanical loads.

Application of polymer coating

The polymer coating allows you to give the floor special properties. For example, it can be used for sports fields.

Topping

A modern solution that allows you to get an attractive and at the same time durable, dust-free floor. The technology is that a dry mixture based on Portland cement with fillers and decorative additives (for example, pigments) is applied to the surface of the floor, which has not yet hardened, which allows one to obtain the necessary decorative effects.

Differences between floor screeds

Types of floor screeds

Single layer concrete for floor

The simplest type of concreting floors. The most common in private households and apartments. Mounted up to 250 mm thick in one layer. After complete hardening, a durable base with high mechanical properties is obtained.

Multilayer concrete for floor

It is used for the restoration of concrete floors with a concrete layer thickness of at least 250 mm , when reconstructing an existing rough foundation to add a hydro- or thermal insulation layer.

Reinforced concrete for floor

Reinforced concrete is poured in industrial premises with a minimum layer of 40 mm ; this type of concrete has the highest strength and resistance to high loads. Due to reinforcing materials, it is possible to slightly reduce the thickness of the concrete floor, reduce the weight of the entire structure, thereby reducing the load on the foundation, this is especially true when it comes to multi-story buildings. Metal or plastic reinforcement, metal or plastic mesh, and finely dispersed components are used as reinforcing materials.

The diameter of the mesh rods and reinforcement should be calculated based on the load on the concrete base. Thus, the diameter of the mesh rods ranges from 0.5-5 mm, the reinforcement 8-12 mm .

Non-reinforced concrete for floor

Non-reinforced concrete is used in technical rooms with not very high mechanical load on the subfloor. These are mainly small workshops, mini boiler houses. The minimum thickness of the screed is at least 40 mm.

Concrete grades for floor screed

Table of ratios of classes and grades of concrete for floors

The grade of concrete (indicated by the letter M) is the strength of the product, indicating the load in kgf/cm2, a numerical value from 50 to 1000 units; concrete up to grade M 350 is used for pouring floors . Relatively speaking, the grade of concrete is the declared strength indicator based on production technology.

For the installation of concrete floors, the most often used brands are M 100, M 150, M 200, M 250. The brand is selected depending on the operating conditions.

Often several brands of concrete mix are used. For example, grade M 100 is used for a leveling pad, grade M 100 is used on hardened concrete, a reinforcing frame is mounted, then grade M 150-M 350 is used.

For concrete floors with increased mechanical load, it is necessary to use a concrete mixture of at least M 250 grade.

M 50. The weakest concrete available . M 50 is mainly used to prepare a preparatory layer before pouring the foundation and installing curbs.
M 100 . It is used as an underlying cushion for screeds and foundations. For filling cavities that do not experience stress.
M 150 . Concrete of this brand is used for rough screed in a house or apartment , pedestrian path on a personal plot.
M 200-250 . Sufficiently strong concrete for pouring strip foundations, blind areas, and open terraces. Stable under conditions of low mechanical load. Suitable for installing screeds in the garage.
M 300 . It is used for the manufacture of stairs both indoors and outdoors, for monolithic foundations and outdoor areas. Has good moisture resistance.
M 350 . It is used for the construction of monolithic houses, including floor slabs, for the foundation of multi-storey buildings supporting columns.

Floor concrete class

It is designated by the letter B and numbers from 1 to 60, and is measured in MPa. The class of concrete, this is the actual strength of ready-made concrete, has an approximate ratio to the grade of concrete in terms of strength of 13.5%. Tests are carried out after the material has completely hardened.

SNiP concrete for flooring

Building codes and regulations ( SNiP ), simply put, are the norms and rules that construction organizations must follow when performing construction work and calculations.

SNiP 31-06 . For residential and public buildings (repaired, reconstructed) up to 55 m high.
SNiP 10.03 . Standards for the construction of premises for keeping animals.
SNiP 2.03.11 . The standards are aimed at designing corrosion protection for concrete and reinforced concrete structures.
SNiP 31-05 . Design work in public buildings and sports facilities must also be carried out according to special rules.
SNiP 11.02 . Special requirements for concrete floors in refrigerated rooms.
SNiP 3.04.01 . Special requirements also apply to the ambient temperature during the installation of concrete floors.

Composition, brand and proportions of components for concrete on the ground

Well, now let's talk about what the concrete consists of, which is used to pour the screed on the ground. Let's start by describing the components that can be added to the mixture.

Concrete composition

The classic concrete recipe includes 4 components:

Binder
Coarse aggregate
Fine aggregate
Thinner (water)

The choice of these materials must be approached responsibly, because low-quality components can reduce the characteristics of concrete, and in some cases, even destroy it.

Binder

Here, they usually use Portland cement marked CEM I 32.5 N (corresponding to grade M400) or CEM I 42.5 N (corresponding to grade M500). Cement is sold in cans or bags of 2, 5, 10, 25 and 50 kilograms. If you plan to pour a large volume of concrete, you can buy cement in MKR - 1,000 kg each.

You should not buy cement in bulk, without packaging. The fact is that this building material has a limited shelf life - only 2 months. Then it gradually loses its properties, which negatively affects the strength of concrete. Cement in original packaging is always marked, as well as information about the production date.

When choosing cement, also pay attention to its appearance. It must be absolutely dry; the presence of lumps and stones in the total mass is unacceptable - this indicates that the material has already had contact with moisture and has set. It cannot be used to prepare concrete.

Lime or gypsum can also be used as a binder. However, they are not suitable for concrete screeds due to their low strength.

Coarse aggregate

Most often, crushed stone or gravel of a fraction of 5-10 or 5-20 mm is added to concrete. It is very important that the filler does not contain any clay or foreign debris. In this sense, the most suitable option is granite crushed stone. It is produced in quarries by blasting monolithic rock with further sifting and separation into fractions. The strength of this material reaches grade M1400, and frost resistance is F400. These are very good indicators.

In principle, you can use other rocks instead of crushed granite. For example, serpentinite and amphibolite are suitable; as a last resort - marble or quartz. You should not take crushed stone from gabbro rock: its grains are covered with a thin dust-like film, which reduces adhesive properties - that is, adhesion to other components of the mixture.

Gravel, despite its external resemblance to crushed stone, cannot boast of such high characteristics. Due to severe weathering, the gravel grains poorly preserved the structure of the original rock. Therefore, some stones literally crumble into fine sand with little pressure. However, this material can be used as coarse aggregate. However, you need to buy not natural gravel, but crushed gravel. It consists of crushed pebbles, cleared of clay and other impurities.

You may also come across recommendations that it makes sense to use broken brick, concrete, slate, and other construction waste as filler. On the one hand, this is quite logical: such materials can be bought for pennies at any construction site, and perhaps you already have them on your site. But you need to understand that construction waste does not have the same properties as crushed stone and even gravel. You will not be able to find out their strength or frost resistance; they do not have a clear fraction. Adding them to concrete is too risky: it can lead to destruction of the floor within the second or third month of use.

It is worth saying that coarse aggregate is not always used to fill screed. In many cases it is not added in order to obtain a more homogeneous mixture. But in this case, we are no longer talking about concrete, but about cement-sand mortar. Concrete always contains coarse aggregate.

Fine aggregate

The ideal option would be alluvial quarry sand. This is a natural material that has been cleaned from clay, silt and foreign matter. The big advantage is that the grains of quarry sand have a rough structure. This improves their adhesion. River sand is also suitable for these purposes, but its grains are more rounded. As for the fraction, here you need to choose a material with a particle diameter of no more than 2-3 mm.

Regular quarry sand will cost less than the alluvial variety. However, it does not go through the washing stage, so it may contain a lot of clay. When clay gets into the concrete mixture, it greatly reduces the strength of the finished structure. Thus, by saving on sand, you risk getting a low-quality screed, which will very soon become covered with cracks and become unusable.

You should also not take ephelium and quartz sand. These varieties are very small and will be difficult to work with. During the preparation of the solution, they precipitate and are unevenly distributed throughout the mixture.

Another material that can be considered as a fine aggregate is crushed stone screening. Outwardly, it is very similar to sand, but in terms of characteristics it is much superior to it. The screenings are stronger, their grains are rougher, and they never contain foreign inclusions. Another advantage is that screening in many regions is cheaper than sand. As for the rock and fraction, you should choose granite, serpentinite or amphibolite screenings with grains with a diameter of 0-5 or 0-10 mm.

There are two more materials that at first glance are ideal for concrete. These are PGS (sand-gravel mixture) and PShchS (sand-crushed stone mixture). They are a mass of grains of sand and gravel or sand and crushed stone. In theory, ASG or PShchS can simultaneously act as both coarse and fine aggregate. But actually it is not. These materials do not have a clear division into fractions. For example, PShchS 0-40 can contain both dust and grains with a diameter of up to 4 cm. However, their ratio is not standardized in any way. Using ASG or PShchS, you will disrupt the proportions of the components in the mixture, which will negatively affect the quality of concrete.

Thinner (water)

We won't say much here. Despite the fact that concrete plants use special water that meets the requirements of GOST 23732-2011, in private construction conditions the requirements for the mixer are much less stringent. It is enough to use clean running water of a transparent color, without sediment or strong odor. Water from a well or borehole is quite suitable.

Concrete grade

Another issue that we will address in this article concerns the strength of concrete. In short, not only the performance characteristics, but also the cost of the material depend on this parameter. Of course, you can fill the floors over the ground with heavy-duty concrete and not worry about its further safety, but this is an additional expense. It is important to maintain a balance between cost and quality. We will talk about how to do this in the continuation of the article.

Brands and classes of concrete

Let's start with an important disclaimer. The fact is that the strength of concrete is measured in grades and classes. The grade indicates what load (in kilograms per square centimeter) a particular concrete sample can withstand under laboratory test conditions. To do this, special concrete cubes measuring 10x10x10 centimeters are cast, which are then placed under a hydraulic press. For example, the M150 brand indicates that the sample could withstand a pressure of no more than 150 kg/cm2. There are 20 such brands in total: the lowest is M50, the highest is M1000.

In principle, this system of measuring strength is quite good, but it has one big drawback. During testing, only one specific sample is tested. Now imagine that you are pouring floors over an area of 20 square meters. You will probably have to make several batches of concrete for this. And each time the proportions of the components will be slightly different. Accordingly, there will be deviations in strength. But you will judge the strength of the entire screed by only one sample - a cube measuring 10x10x10 centimeters.

It is much more accurate to divide concrete into strength classes. The essence of the experiment remains the same, but the key factor here is how much pressure the sample can withstand in 95 percent of tests. And strength is measured not in kg/cm2, but in megapascals (MPa).

Let's take M300 concrete as an example. In theory, this figure indicates that the sample is able to withstand pressure of 275-325 kg/cm2. If we compare the M300 brand with the closest class, we get B22.5. In other words, such concrete is guaranteed to withstand a pressure of 22.5 MPa. This is called guaranteed strength.

There is a certain relationship between grades and strength classes of concrete.

It is shown in the table below:

Concrete class	The most appropriate grade of concrete
B3.5	M50
B7.5	M100
AT 10	M150
B15	M200
IN 20	M250
B22.5	M300
B27.5	M350
B30	M400
B35	M450
B40	M500
B45	M600
B50	M700
B55	M750
B60	M800
B65	M850
B70	M900
B75	M950
B80	M1000

As you can see, knowing the brand of concrete, you can find out its class.

But why is such a dual system needed? It's simple: the strength class of concrete can only be determined in laboratory conditions. If you prepare the solution yourself, then you can only rely on the approximate brand that should be obtained when using certain components. Below in the article we will give specific recipes for preparing concrete of different brands.

You can read more about the strength of concrete in the article Type of concrete for floor screed.

Grade of concrete for floors on the ground

As we have already said, strength grades are mainly used in private construction. And if you prepare concrete with your own hands, then you need to understand what grade you will get as a result. Next, we will look at those brands (classes) that can be used for pouring screed on the ground.

Concrete M50 (B3.5) This is the lowest grade of concrete. Its use in construction is severely limited due to its low strength. Concrete M50 can only be used for the top (leveling) layer of the screed. In addition, this solution can be used to repair small cracks and other damage to the floor.
Concrete M100 (B7.5) This concrete is suitable for installing floors in ordinary residential premises. It cannot withstand too heavy loads (more than 125 kg/cm2), but it is very cheap.
Concrete M150 (B10) In terms of characteristics and cost, this concrete is not much different from the previous brand and is also suitable for pouring screed in residential premises. In principle, it can also be used for flooring in outbuildings, but only if there are no objects weighing more than 700 kg.
Concrete M200 (B15) This is a durable concrete that can be used to fill the floor in a garage, basement or shed. It is also suitable for residential premises, but only when very strong loads are applied to the floor (for example, from heavy furniture).
Concrete M250 (B20) is used for constructing floors in garages and other outbuildings. Capable of withstanding loads of up to 275 kg/cm2, which allows cars and other heavy objects to be placed on such a base.
Concrete M300 (B22.5) In general, SNiPs indicate that this kind of concrete should be used for pouring floors on the ground. But it must be said that this is a fairly high brand, and its use in private construction is not always justified.

M300 concrete can support the weight of a truck, but it is very difficult to work with. Low mobility makes it too difficult to manually knead and lay the solution. You will have to use special equipment - electric concrete mixers and deep vibrators.

Higher grades are practically not used in private construction because the cost is too high. In most cases, M200 concrete is sufficient for pouring a floor on the ground. At high groundwater levels, as well as when equipping basements, grades M250 and M300 are used.

Proportions of concrete for floors on the ground

As mentioned above, when you mix concrete yourself, you can predict its future strength in advance. To do this, you need to mix the components in certain proportions. We'll talk about how to do this further.

The tables below show the proportions for preparing concrete of various grades:

Proportions of components (in parts) when using M400 cement
Approximate grade of concrete	Cement	Sand	Crushed stone/expanded clay	Water
M50 (B3.5)	1	4	7	No more than 1
M100 (B7.5)	1	4,6	7	No more than 1
M150 (B10)	1	3,5	5,7	No more than 1
M200 (B15)	1	2,8	4,8	No more than 1
M250 (B20)	1	2,1	3,9	No more than 1
M300 (B22.5)	1	1,9	3,7	No more than 1

Proportions of components (in parts) when using M500 cement without coarse aggregate
Approximate grade of concrete	Cement	Sand	Water
M150 (B10)	1	4	No more than 55% by weight of dry ingredients
M200 (B15)	1	3	No more than 55% by weight of dry ingredients

Proportions of components (in parts) when using M500 cement
Approximate grade of concrete	Cement	Sand	Crushed stone/expanded clay	Water
M100 (B7.5)	1	5,8	8,1	No more than 1
M150 (B10)	1	4,5	6,6	No more than 1
M200 (B15)	1	3,5	5,6	No more than 1
M250 (B20)	1	2,6	4,5	No more than 1
M300 (B22.5)	1	2,4	4,3	No more than 1

As you can see, the more cement, the higher the grade of concrete. There should always be no more water than cement. On the one hand, it increases the workability of the mixture, and on the other, it reduces the strength of the future concrete. Therefore, it is better to add water gradually.

The output should be a plastic, but not flowing mass. You can check the consistency this way: if the mixture sticks tightly to the shovel, it means there is not enough water. If the solution is so liquid that it flows freely under its own weight, this indicates an excess of water. In this case, it is necessary to increase the content of cement and sand. However, this way you will upset the ratio of components. Therefore, it is better to mix cement, aggregates and water in advance in the proportions indicated above.

How to calculate the amount of concrete for floor screed

Calculating the volume of the required amount of concrete for pouring floors is not so difficult. To do this you need:

Measure the area of the room (length and width).
Recapture the horizon.
Find the lowest point and the highest point.
Measure both points.
Take the average value of the formation height.
Multiply all obtained values.

Example: room area is 10 x 10 m, the thickness of the future layer at the lowest point is 7 cm, at the highest point 3 cm, on average it will be 5 cm (0.05 m).

Multiply: 10 x 10 x 0.05 = 5 cubic meters. The required volume of concrete mixture is 5 cubic meters.

Types of industrial floors by purpose

Industrial floors are divided into the following types according to their intended purpose:

for production and warehouse premises, terminals;
for industrial premises with high (increased) humidity levels;
for rooms and areas with increased constant load;
for public institutions (educational, medical, catering organizations);
for industrial refrigerators and freezers;
for decontaminated buildings and sanitary checkpoints in the nuclear industry;
fire- and explosion-proof, antistatic floors;
polyurethane floors for sports fields.

Concrete floor technology

Find the lowest point. Before starting work with concrete floors, it is first necessary to carry out geodetic work, find and mark the zero (horizon).
Prepare the base. On the ground. Before installing a concrete screed, it is necessary to prepare the base for the concrete floor; to do this, you need to compact the soil and make a cushion in the form of a sand bedding.

On a monolithic base. Concrete floors are installed after the foundation has been repaired, if required. Cracks and potholes are filled with a mixture of cement and sand, i.e. brand 50.
Installation of waterproofing. Concrete takes a long time to gain strength; while the mixture is hardening, it should not be allowed to dry out. Therefore, waterproofing is used; it prevents liquid from escaping from the concrete.
Installation of formwork. Formwork is wooden, metal, plastic panels, with the help of which you need to give the necessary shape to the future layer.
Formation reinforcement. If technology requires it, the base is reinforced before pouring concrete floors. This is done to increase the strength of the concrete base.
Installation of concrete floors. Before carrying out work with concrete, you need to objectively evaluate the entire scope of work. The fact is that concrete should be poured in one layer; pouring floors in 2-3 stages with large intervals of several hours or more is a gross violation of the technological process. Therefore, situations often arise when it makes sense to order ready-made concrete from a concrete mixer. If the object is located at a height or in a place that is difficult for a concrete mixer to reach, there is a concrete pump.
Actions during concrete work. To perform the job efficiently, the mixture must be leveled and compacted. For this, various tools are used, such as a vibrating screed and a vibrator. Using a vibrator, air is expelled from the concrete mixture, and using a vibrating screed, the concrete mixture is evenly distributed over the surface.
Vibrating screed.
Concrete vibrator.
Grouting concrete floors. After 6-8 hours after completion of work, the concrete base should be cleaned with a special trowel (if the area is not large, you can rub the screed manually using a polyurethane float). It is recommended to repeat the procedure every few hours.
Hardening of the concrete floor. After cleaning the surface, you need to let the base get stronger for several days. All this time, the concrete floor must be irrigated with water.
Expansion joint. No later than 72 hours after finishing work, it is necessary to cut the expansion joint with an angle grinder. This must be done if a large load on the floors is expected, for large areas. Any base makes a movement invisible to the human eye. This happens due to the acting load from the mass of the structure itself, the equipment on it, thermal expansion during heating or contraction during cooling, and seismic movements. An expansion joint will avoid destruction of the concrete floor. The depth of the expansion joint is usually 1/3 of the total layer thickness.
Treatment of expansion joints. After the seams have been cut, they must be treated with any sealing material. This will prevent water and debris from getting into the seams.

The article was written for the site.

Tags: Concrete, Self-leveling floor

Common Mistakes

Poor preparation of the soil or sand and gravel cushion - if the layers are not compacted well enough, the concrete floor will be weak and may even deform the finishing floor covering.
Poor quality of fillers - if the gravel or sand is not washed, the floor will be weak even if high-quality cement is used in large volumes.
Incorrect reinforcement - if the mesh or reinforcement is laid directly on the base, the frame will not fulfill its task. It increases the strength of the structure and ensures that the floor and the finishing layer of laminate or linoleum laid on it will not sag, only if it is completely filled with screed on all sides.
Failure to comply with technology, saving on materials - all this leads to deterioration in performance characteristics and a decrease in the service life of the concrete floor.

It is quite possible to pour a concrete floor over the ground in a private house with your own hands. By paying attention to all the important points and strictly following the technology, working with high-quality materials, you can create a strong, durable and reliable floor.

What measures are used to ensure the reliability of concrete elements?

Some developers have concerns that they will have exactly this 5% that does not meet the quality of the concrete floor screed. The result is premature destruction, the need for unscheduled repairs, etc. There is no need to be afraid, such problems cannot arise in principle, everything is foreseen at the design stage. For example, for concrete M 350, class according to table B 30, the following precautions are used.

Testing concrete for strength

In total, the safety factor increases the parameters of concrete structures at least three times. Accordingly, financial costs increase within the same limits.

Concrete sample during testing

Conclusion. The reliability of the structure is ensured by a significant increase in concrete consumption, an increase in the estimated cost, etc. If you want to build high-quality and relatively cheap buildings, it is recommended to purchase concrete only from those manufacturers who have the most modern high-precision equipment for preparing concrete mixtures of various brands.

Cement consumption for screed

If you decide to mix the screed mortar yourself, you need to decide on the amount of cement you will need. It can be calculated based on the found volume of solution. There are tables that show the consumption of cement for screed depending on the brand of mortar and binder.

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The amount of cement in one cubic meter of screed mortar

Let's calculate the amount of cement for one cube of M150 sand concrete screed. If we use M400 cement, 400 kilograms of cement will be needed per cube (according to the table). To find how much cement will be needed for the example described above, you need to multiply the found volume of solution by the norm: 0.6 m³ * 400 kg = 240 kg. That is, for this room you will need 240 kilograms of cement. To determine the number of bags, divide this figure by the mass of cement in the bag.

Other packaging also exists, but is rare. Once you decide on the brand and manufacturer, you can accurately calculate the number of bags of cement for the floor screed.

How to calculate the amount of cement per cubic meter of sand

You can also calculate the cement consumption based on the available amount of sand. You never know. Maybe someone will buy sand and so that there are no leftovers, it must all be used up.

Source

About concrete hardening

When working with all types of concrete, we remember the following:

The maximum strength of high grade concrete is achieved after 6 months. That is why it is better to build private houses a season after pouring the foundation.

It is important to ensure uniform, natural drying of the concrete, and at elevated temperatures it is necessary to pour (wet) the drying concrete for a week and cover the concrete with polyethylene for the entire time it gains strength.

Source

CemThermo

A specialized highly effective plasticizing and strengthening additive for pouring heated floors.

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Step 4. Grout

Grouting work performed with special equipment allows you to obtain a flat, smooth, glossy floor surface, increases strength, and eliminates dust. At this stage it is also possible to apply toppings.

Step 5. Varnishing and cutting seams

After polishing is completed, a special polyacrylate varnish is applied to the floor surface, which protects the concrete from drying out and makes the surface more durable.

On the 3rd day, temperature-shrinkage seams are cut to compensate for shrinkage processes. The seams are then sealed with polyurethane sealant.

Industrial floors are an important part of the building. They carry increased loads and must meet high demands. Installing industrial floors is a labor-intensive and large-scale task that requires special equipment and high costs. Saving time, money, labor and at the same time obtaining an industrial concrete floor of the highest quality is a real task if you take advantage of the developments of the modern chemical industry: CemThermo CEMMIX concrete additive and CEMMIX fiber.

You can buy CemThermo, basalt fiber CEMMIX without leaving your home, with discounts from 5 to 33%!!!!

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Buy at Leroy Merlin

Brand of cement-sand mortar for screed: choice of strength

What brand of cement-sand mortar is used for screed? Previously, they could put M50 or M75. Now the minimum is M150. Why? Because, first of all, the finishing requirements were much lower. What was previously considered normal - small holes, cavities, cracks - is now unacceptable. And this is not just “aesthetics”. To a greater extent, these are the requirements of finishing coating manufacturers. They require an almost ideal surface that does not generate dust, and only a solution with a strength of at least M100 can provide this.

The brand of cement-sand mortar for screed is selected based on the floor covering being laid

There are other reasons why a higher brand of solution is used. First. No one is sure of the quality of cement, so they prefer to play it safe than to redo it all over again. Secondly, modern coatings require a flat, solid base and the screed mortar must be durable. And thirdly, you simply cannot install a low grade under self-leveling compounds or modern tile adhesives with polymer additives. To prevent the two parts of the coating from delaminating, the difference in strength should be no more than 50 units. That is, if the leveling mixture has a strength of M250, the floor screed solution must have a strength of M200 and not lower. Same thing with tile adhesive. So pay attention to this.

Proportions of a classic DSP screed

The classic mortar for floor screed, as already mentioned, is cement with sand diluted with water. The proportion (the amount of sand per unit of cement) depends on the required strength of the screed and the brand of cement used. To make the floor surface durable, use expensive Portland cement grade M400 and higher.

Proportions of mortar for floor screed for M150, M200 and M300 when using different grades of cement

For screeding floors in utility rooms, you can also use the cheaper M300. It will cost a little more, but there will be savings. It is better not to use such cement for the foundation of a house or apartment under modern coatings. The rework will require significantly more savings on cement.

Beginners in the construction business think that if you take more cement, there will be a stronger screed. But no. For strength, the correct ratio of all components is important, and an excessive amount of cement can cause a decrease in strength. If you want a stronger screed, use high-quality cement and accurately measure the proportions. By the way, you shouldn’t take more water either. This will increase the fluidity of the solution, but will increase the number of shrinkage cracks. So once again: in order to get strong and reliable concrete, you need to strictly observe the proportions.

Which sand to take

It is better to take river sand, washed, of at least two fractions: coarse and medium. Why river? Because it has sharp edges, and this reduces the likelihood that it will settle into the lower layers. This is understandable. Why washed? It contains minimal dust. The less dust, the higher the strength of the solution. Sand is also needed in different sizes so that the strength of the solution is normal.

To screed the floor you need sand: washed river sand, two fractions (not fine)

If you are going to lay an expensive coating on the floor with high requirements for the strength of the base (parquet, parquet or engineered boards, vinyl tiles), it is better to take this kind of sand. There will be fewer problems.

Kneading sequence

When making a floor screed solution, first mix the dry ingredients - cement and sand. When mixing manually (in a trough), there is not much difference between what to throw in first - cement or sand. If you use a concrete mixer, immediately add sand and spin it for a couple of minutes without cement. Then, gradually, usually with shovels, cement is added. After each portion, wait until it is more or less evenly distributed, then add the next one. After adding the entire amount of binder, mix until a uniformly colored mixture is obtained.

You choose how to prepare the solution yourself: order it at the factory/workshop, mix it yourself

When the dry ingredients are mixed until a homogeneous gray mass is obtained, add water little by little. It is calculated based on the amount of cement. Usually 0.45-0.55 parts of water are taken for 1 part of cement. Why don't they indicate exactly? Because the amount of water depends on the moisture content of the sand. It is advisable to pour a minimum amount of water: this way there will be fewer cracks when drying.

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Ready-made mortar or sand-cement mixture

Those who have at least once mixed DSP or concrete on their own are more often inclined to buy ready-made concrete. And not a mixture of sand and cement in bags, but concrete from a concrete mixer. Yes, it costs more money, but it requires much less time and effort. Another advantage of this solution: filling without cold seams. This means fewer cracks and problems in the future. The next plus is that concrete mixers can deliver the solution to the desired floor. Imagine that you have to move a couple of tons of sand and cement. Even if there is a freight elevator, it is not easy. It can also be costly if you pay helpers. Climbing stairs “on your shoulders” is generally a problem.

So that you do not care about the proportions of cement and sand, you can buy ready-made mixture in bags

What are the advantages of buying ready-made sand-cement mixture in bags? The fact is that the proportion is kept exactly, sand is used in several fractions and in the right quantities. That is, the screed is guaranteed to have the required strength. The downside is the price. You can buy the same amount of cement and sand for a much smaller amount. This is if you don’t bother with sand fractions. If you take care of this, the savings will become smaller: not all factions are cheap.

Answers on questions

How to determine the quality of a concrete solution by eye?

This question interests almost all novice builders. The test recipe is very simple. There is no need to make any cubes, especially since to test their strength you need to have special laboratory equipment. Checking the concrete is simple - if after an hour clear water appears on the surface, then there is not enough cement, you need to increase its volume or reduce the percentage of other ingredients. It is better to remember the number of shovels of cement, sand and gravel per mixer, and then use the practical proportions available.

How to get high-quality concrete solution

How long can ready-mixed concrete be left in place?

Another problem of interest to beginners. But they need to know that concrete hardens not because the water completely evaporates. This opinion is fundamentally wrong. Concrete hardens through chemical reactions between cement and water, which begin from the moment the mixture is prepared. If water is added to hardened concrete and mixed, its strength will decrease significantly; a significant part of the cement has already bonded with the liquid and no longer affects the parameters of physical strength.

Video – Tips for mixing concrete

Basalt fiber

Basalt fiber (from roving) is intended for volumetric reinforcement of concrete, mortars and composite materials.
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We recommend studying: Increasing the strength of concrete

Step 3. Filling

For pouring industrial floors, concrete of at least B22.5 strength class with entrained air of no more than 3% is used.

Work must be carried out continuously; otherwise it is necessary to arrange seams. Since the areas to be poured are usually large, the concrete mixture is supplied using a concrete pump. The concrete mixture is compacted using vibrators or a vibrating screed.

The use of special additives for concrete, for example, CemThermo CEMMIX additive, makes it possible to save energy and human labor costs.

The CemThermo CEMMIX additive is ideal for floors because it combines the qualities of a plasticizer and a water repellent and provides the concrete mixture with the following properties:

increased workability;
increased density and strength of concrete;
prevention of crack formation;
increasing the waterproofness of concrete;
reducing the water requirement of the mixture by 10–20%;
the ability to save up to 15% of cement without reducing strength.

The additive is supplied ready-made and is easy to dose and introduce into the concrete mixture. Considering that it is very easy to buy CemThermo wholesale from the manufacturer or in retail chains, for example, in Leroy, and the additive itself is inexpensive and is used at the rate of 0.5–1 liters per 100 kg of cement, there are also cost savings. Each liter of CemThermo can save up to 30 kg of cement, which for large-scale work (such as pouring floors) provides noticeable savings.