All about cement-sand mixtures: composition, purpose, properties, advantages and disadvantages

When carrying out any construction and repair work, cement is almost never used in its pure form. The composition of any cement mortar, in addition to cement and water, must include other building materials, primarily sand.

We learn about cement-sand mixtures and their use from the article.

The preparation and use of cement-sand mixtures is regulated by GOST 28013-98 “Building mortars. General technical conditions".

Based on their main purpose, solutions are divided into the following types:

1. masonry (including for installation work);
2. facing;
3. plastering

The compressive strength of mortars at design age is characterized by the following grades: M4, M10, M25, M50, M75, M100, M150, M200.

Portland cement and Portland slag cement are used as binding materials in accordance with GOST 10178;

Sand is used as a filler for construction work in accordance with GOST 8736.

Types and areas of their use

Universal dry mixtures differ in composition and purpose, they have their own characteristics and characteristics.
You should pay attention to the marking, the number in which indicates the strength of the original product

M100

M100 products are intended for manual plastering and putty. The mixture is applied in an even thin layer, which leads to material savings. She is easy and pleasant to work with. The mixture retains its properties for two hours from the moment of dilution. Prices for M100 products are quite affordable.

M150

M150 products are the most popular of the varieties of universal mixtures. It is used in virtually all construction work using dry compounds. Unlike M300 and M400, it is used for masonry, plaster, and screed. Factory packaging is presented in 50 kg bags, less often they produce products in 25 kg packaging.

The universal mixture includes Portland cement, sand, mineral powder, plasticizers and other additives. The finished composition can only be diluted with cold water in the proportion indicated on the package.

M150 products are endowed with many advantages: they are reliable, frost-resistant, have good adhesion to various surfaces, high moisture resistance and vapor permeability. It is used in any climatic conditions.

The disadvantages of M150 include poor resistance to increased loads (no more than 150 kg per 1 cubic cm), therefore such a mixture is not used for work with the foundations of multi-story buildings.

The name “universal” speaks of the variety of applications of the M150 composition.

• The plaster mixture is designed for interior and exterior plastering work. Layer thickness can be applied up to 50 mm. After mixing, work should begin immediately: the mixture is in a pliable state for 2 hours. The plaster becomes completely dry and strong after 4 weeks.
• Using the M150 screed mixture, the floors in the rooms are leveled. Checking the level and setting the beacons, the floor is poured with a thickness of 1 to 10 cm. Thanks to the cement base, the floor acquires durable qualities that are resistant to temperature changes.
• The masonry mixture is used for laying gas silicate blocks and bricks of all types. M150 products can be used indoors and outdoors in cold or hot weather; weather conditions do not affect the quality of masonry. The dry mixture has proven itself well in rooms with high humidity.

M200

Product M200 is a masonry mixture. It consists of Portland cement, river sand and special additives. Designed for laying bricks, concreting flooring, constructing simple foundations, repairing walls and processing seams in concrete structures.

M200 can be used for laying garden tiles, as well as for plastering and puttying walls. It is available in bags weighing 50 kg.

M300

Sand concrete M300 appeared on the construction market not long ago, but has already gained popularity. Unlike the M150, it is designed for heavy loads. The products are durable and reliable, have a long service life, adapt well to weather conditions, are moisture resistant, environmentally friendly, and do not shrink. M300 consists of Portland cement, which contains gypsum, sand and crushed clinker. Products are packaged in 50 kg bags, less often in 200 kg bags for industrial scale.

Due to its special strength, the composition is used in all areas of construction work in all climatic conditions. During installation, they are used to install the foundation, floor screed, leveling walls and other surfaces. The product has proven itself well as a grout for cracks during work at emergency sites. The composition is used when laying garden paths, stairs, and borders. The mixture is used in the production of expanded clay concrete.

According to their properties, depending on the application, M300 products are divided into several subtypes.

• Coarse grain has incredible strength and long service life. With its help you can fill the foundations of high-rise buildings.
• Medium-grain is used for screeds, self-leveling floors, work with borders and garden paths. It is used wherever a medium-grained fraction of the mixture is required.
• Fine-grained is also reliable and durable; it is used for plastering work.

When choosing a universal dry composition, you should remember: the more famous the brand and the higher the grade of the product, the more expensive the product and the more reliable its technical properties.

For information on what dry building mixtures are, see the following video.

Sand to cement ratio

A high-quality cement-sand mixture that meets the requirements can be prepared at home. The main thing is to know what it is needed for and strictly follow the recommendations.

Brickwork

The recipe for this mixture is quite simple. However, the most popular type of DSP is masonry. For the mixture, use binder grades up to M400, sand of medium fraction (up to 2 millimeters) and as dry as possible.

Basic proportions of cement and sand:

• 1:5 – M25 solution
• 1:4 – mixture M50
• 1:3 – TsPS M75

For particularly strong load-bearing walls, bricks are laid on M50/M75, where the volume of sand is reduced and the volume of cement is increased. In addition, these solutions are used to make columnar foundations, in conditions of high humidity, to create houses from clinker bricks. The remaining tasks are performed using the M25 mixture. See below for information on how to mix this type of cement mortar.

Mixture composition per 1m3 of masonry:

• 268 kilograms of cement
• 1064 kilograms of sand
• 250 liters of water

Mix everything and you can start working.

Preparation of concrete

To prepare concrete, large fillers are additionally used to ensure a sufficient level of strength of the solution. The batch can use a ready-made dry mixture or different components in the required volumes. In addition, today in Moscow and the regions the required amount of concrete can be ordered and delivered from the plant to the site.

The technical characteristics of concrete directly depend on the quality and properties of the materials and their proportions.

It is very important not to skimp on cement - if you plan to prepare an M300/M400 solution, choose M500 cement. The grade of cement is always higher. After all, even if you take cement of a lower grade, but in large quantities, the quality of the concrete will still suffer.

Large fillers (crushed stone, gravel) are used to strengthen the material. The standard formula for preparing durable concrete is: 1 part cement, 2 parts sand, 4 parts crushed stone, 0.5 parts water. When adding additives, the volumes of components may change.

For plaster and floor screed

When thinking about how to make cement mortar for screed and plaster, it is worth remembering that we are talking about different properties. Floors are filled with relatively liquid solutions, while for plastering thick mixtures of pure sand, cement and water are prepared. The thickness of the plaster mixture depends on many factors.

The most common proportion used in preparing plaster is 1 part cement and 5 parts sand with enough water to obtain the desired consistency.

More durable mixtures are prepared for screeds, as they must withstand certain loads. Here you will need a minimum grade of TsPS 150, but it is better to make a cement-sand mortar M200 and higher. Materials must demonstrate a threshold strength of at least 10 MPa.

To understand how to properly dilute cement, you need to take into account the work and operating conditions. So, if the mixture is used to mask various utilities, it may be thicker. But to level the surface and strengthen the floor, liquid DSP is used. The thicker the layer, the higher the grade of concrete should be.

When a cement-sand mixture is used, the consumption of materials plays a major role and it is important to calculate it before starting work. Calculations are based on the cubic capacity of the site/room. Measurements are taken with a tape measure, the width is multiplied by the length and the area is obtained. Next, take the depth of the layer and calculate how much mixture needs to be poured. On average, for a screed 10 centimeters thick you need 50 kilograms of M400 solution per square meter.

To perform individual calculations, the values ​​are converted to cubic capacity to calculate the consumption of cement-sand mixture per 1 m2.

Performing calculations:

• For a room with an area of ​​100 square meters and pouring a screed 10 centimeters (0.1 meters) deep, you need 10 m3 of solution. On average, about 555-713 mixtures are consumed per 1 m3 (exact data can be found in the instructions on the packaging) - which means that for 10 cubic meters the figure needs to be multiplied by 10. The weight depends on the brand of cement - for a mixture based on M400, the weight is calculated to be within 700 kilograms , for M100 – already 500-600 kilograms.
• The consumption of CPS per 1 m2 is almost the same for preparing a solution from a ready-made mixture or individual components. So, if we are talking about the finished mixture, then it contains about 1.4 kilograms (specific gravity) in one liter. Therefore, to fill 10 cubic meters of screed you will need a dry mixture: (10 m3x650kg) x 1.4 = 9100 kilograms. Thus, to fill 10 m3 of mixture you need 9100 kilograms of dry powder or 6500 liters.

For the foundation

When considering the types of cement mortars, one should not overlook the rules for preparing the mixture for pouring the foundation. The building mixture includes the following components: cement, sand, crushed stone, water. The more crushed stone in the composition, the higher the strength. If you need to increase the elasticity of the mixture, you can add clay to the composition.

The proportion of cement and other components may vary, but there are standard values. Below is the ratio based on a calculation of 10 kilograms.

Composition of the mixture for pouring the foundation:

• 10 kilograms of cement
• 30 kilograms of sand
• 40-50 kilograms of crushed stone/gravel
• Water - about half of the total mass of the solution

So, in the above example, up to 80-90 kilograms of dry mixture is obtained - which means you need to take about 40-45 liters of water. If you obtain a very dense solution, you can immediately dilute it with water, but you should not make it very liquid. Before diluting cement with sand, you need to study some nuances.

Things to remember:

• If the sand is damp, there is moisture in it, the material needs to be dried, otherwise add a smaller volume of water to the mixture.
• The sand must be clean - the fewer impurities, the better and faster the binder sets.
• It is better to take gravel/crushed stone in a small fraction (about 1-2 centimeters).
• You should not purchase cement before construction begins and store it. Over time, the characteristics of the binder change, which affects the strength and density of the cement-sand mixture. If you buy ready-made dry mixtures for work, it is also advisable to purchase them a week or two before the start.

Specifications

The technical characteristics of sand concrete determine the rules of its operation and resistance to external destructive factors. The composition and technical properties of the M300 mixture make it possible to use it both as a self-leveling compound (self-leveling mixture) and as a repair composition.

Compound

Any variants of M300 mixtures are gray in color. Its shades may vary depending on the composition. For such materials, Portland cement M500 is used. In addition, the M300 mixture, according to GOST, has the following proportions of the main components: one third of cement, which is the binding ingredient, and two thirds of sand, which is the filler.

Frost resistance

This indicator indicates the ability of the material to withstand multiple temperature changes, alternating thawing and freezing without severe destruction and reduction in strength. Frost resistance allows the use of M300 sand concrete in unheated places (for example, in permanent garages).

Frost resistance of mixtures with special additives can be up to 400 cycles. Frost-resistant repair mixtures (MRMs) are used for mixing construction compounds used in the reconstruction and restoration of concrete, reinforced concrete, stone and other joints, filling voids, cracks, anchors and for other purposes.

Compressive strength

This indicator helps to understand what tensile strength a material has under static or dynamic influence on it. Exceeding this indicator has a detrimental effect on the material and leads to its deformation.

Dry mixture M300 can withstand compressive strength up to 30 MPa. In other words, given that 1 MPa is approximately 10 kg/cm2, the compressive strength of M300 is equal to 300 kg/cm2.

Temperature range

If the thermal conditions are observed at the time of work, the process technology is not disrupted. The continued preservation of all the performance qualities of concrete is also guaranteed.

It is recommended to carry out work with M300 sand concrete at temperatures from +5 to +25? C. However, sometimes builders are forced to violate these recommendations.

Adhesion

This indicator characterizes the ability of layers and materials to interact with each other. Sand concrete M300 is capable of forming reliable adhesion to the base layer, which is equal to 4 kg/cm2. This is a very good value for dry construction mixtures. To ensure maximum adhesive performance, manufacturers provide appropriate recommendations regarding preliminary preparation work.

Bulk density

This indicator means the density of the material in its uncompacted form, taking into account not only the volume of particles, but also the space that has arisen between them. This value is often used to calculate other parameters. In bags, the M300 dry mixture is in bulk with a density of 1500 kg/m3.

If we take this value into account, it is possible to draw up an optimal ratio for construction. For example, with the declared density, 1 ton of material is 0.67 m3 in volume

In small-scale construction work, a 10-liter bucket with a volume of 0.01 m3 and containing about 15 kg of dry mixture is used as a measure of the amount of material.

Sand particle size

Factories produce M300 sand concrete using sand of different fractions. These differences determine the peculiarities of the technique for working with the solution.

There are three main sizes of sand used as raw material for dry mixtures.

• Small size (up to 2.0 mm) – suitable for street plastering work, leveling seams.
• Medium size (from 0 to 2.2 mm) – used for screeds, tiles and borders.
• Large size (more than 2.2 mm) – used for pouring foundations and foundations.

Mixture consumption

This indicator characterizes the material consumption with a layer thickness of 10 mm per 1 m2. For M300 sand concrete it is usually in the range from 17 to 30 kg per m2. It is worth noting that the lower the consumption, the more economical the work costs will be. In addition, manufacturers often indicate the consumption of sand concrete in m3. In this case, its value will vary from 1.5 to 1.7 t/m3.

Delamination

This indicator characterizes the connection between the lower and upper parts of the solution. The M300 mixture usually has a delamination rate of no more than 5%. This value fully complies with the requirements of the standards.

Number of PCB bags for brickwork and calculations on a calculator

Laying a brick wall should be done using a mixture with a grade corresponding to the brick. This structure is as durable and uniform as possible. In general, M100-M200 is used for masonry.

So it is necessary to take into account the quality and strength of the material (both the mixture and the brick). Using basic standards, approximately 250 kg of M100 mixture should be used per 1 m3 of wall.

Cement is the main and main component for most buildings and structures. Here's how to properly dilute cement.

The use of sand is a necessary measure when carrying out any construction or repair work. Here everything is about quartz sand.

Kitchen renovation is a very important and serious matter and must be approached with all responsibility. By clicking on the link, you will get acquainted with wall panels for the kitchen made of plastic with photo printing.

If you prepare the solution yourself, then the proportion should be 1 to 4. Liquid should be added to the CPS, which is usually half the total weight of the mixture.

Of course, the laying of a wall greatly depends on the thickness of the seams; as the space between the bricks expands, the amount of mortar per 1 m3 also increases. The thickness of the walls also plays an important role, so for facing bricks laid in 1 layer, significantly less cement is required than for load-bearing walls of 2-4 bricks.

Calculation for masonry

Regulatory documents contain detailed recommendations and the relationship between wall thickness and the amount of mortar used.

Examples are presented based on ordinary bricks and the required quantity per 1 m3:

• wall 12cm - 420 bricks and 0.19 m3 of mortar;
• wall 25cm – 400 bricks and 0.22 m3 of mortar;
• wall 38cm – 395 bricks and 0.234 m3 of mortar;
• wall 51cm – 394 bricks and 0.24 m3 of mortar;
• wall 64cm - 392 bricks and 0.245 m3 of mortar.

What is sand concrete made of?

The characteristics of sand concrete m300 (composition, proportions 1 m³) are standardized by GOST 7473-94.

High-quality dry mixture contains:

• Portland cement PC500 D20/PTs400 D0;
• fractionated dry sand, with a combined composition of fractions (particle size 0.80-4.0 mm);
• other additives (frost-resistant, microsilica, fiberglass) are introduced at the discretion of the manufacturer.

Sand concrete M300 can be used to construct wear-resistant, high-strength floors as a load-bearing covering in utility and residential premises, including garages, basements (with a load of 250-300 kg/cm²)

Depending on the sand used, M300 grade material is used to carry out certain work:

Composition of sand concrete m200

The composition of sand concrete is determined by GOST 31357 - 2007 “Dry mixtures for construction with a cement binder”. Each manufacturer can make small additions to the composition of the mixture, but there are key components and indicators that are standard.

Main components:

• Cement m400;
• Sand;
• Crushed stone;
• Water.

When creating, Portland cement M400 is mainly used; it is one of the most common, and its technical characteristics meet all specified standards. Sand is used in two types of fractions - fine-grained and coarse-grained, thoroughly cleaned of foreign impurities.

The composition and proportions of sand concrete m200 per 1m3 according to construction standards, the mixture consumption is:

• Portland cement - 265 (1 part);
• sand 860 (2 parts);
• crushed stone 1050 (5 parts);
• water 180 (? parts).

Tips and tricks

When planning to prepare a cement-sand mixture, you must immediately decide in what proportion the different components will be taken, what grade of strength is needed, and what the main properties are.

It all depends on the scope of application of the mortar - so, if M50 or M75 is suitable for brickwork, then for screed prepare at least a mixture of M150, 200 and higher. The composition of any CPS includes cement, sand, water, but the result is different depending on the ratio.

Some tips from the experts:

• To prepare a plastic mixture, you can add liquid soap to the solution, previously thoroughly mixed with water.
• You need to know how to properly dilute cement and other components: first, all the dry substances are mixed, then water is added in small portions so that you can control the thickness of the mixture and achieve the ideal consistency.
• When preparing, take into account the brand of building material from which the walls are built. It is desirable that the parameters coincide - then the wall will have a homogeneous structure, reliable and durable.

• Before you make your own cement for plaster, you should take care of purchasing perlite. If you replace some of the sand with it, you will be able to achieve higher thermal insulation characteristics.
• For work, we use exclusively fresh cement, without lumps, produced according to technology and stored in optimal conditions - in this case, it will be possible to achieve the most uniform mixing and high adhesion.
• Detergent or soap is also added to the cement (the proportions remain the same, it is simply mixed with mixing water) to increase adhesion.
• The solution is best prepared in a container made of metal, plastic or wood.
• To thoroughly clean the sand from impurities that can reduce its strength, you can soak it in water for a short time.
• The consistency of the finished cement-sand mixture is usually checked with a trowel: the solution should be distributed evenly over the tool, but not run off (it is worth remembering that this rule works in the preparation of standard mixtures; for some tasks other properties may be important).

• The finished DSP is used for an hour after mixing, until the solution begins to thicken and harden. Therefore, you need to immediately prepare the required volume - exactly as much as you can produce in an hour.
• It is forbidden to dilute an already hardened solution with water, as it immediately loses its properties and can cause destruction of the structure/building.
• When mixing a mixture in a volume greater than 2 cubic meters, no drills or attachments will help - only a concrete mixer or ordering the required volume at the factory.
• The solution, which is planned to be used where minimal loads and low mass are noted, can be prepared with a reduced volume of sand. But this approach is only possible on the condition that before properly mixing the DSP, the master has precisely determined the specifics of the application and the remaining solution will not be used for the implementation of any other tasks.
• Mixing the cement-sand mass should last at least 20 minutes - this way the solution will be homogeneous and of high quality.
• The ratio of the proportions of the components is looked at in GOSTs and SNiPs (the opinion of experienced craftsmen is allowed), as well as in the recommendations of the manufacturer of cement, dry mix, etc.

Cement-sand mixture is a universal material that can be used to perform a whole range of works, obtaining the most durable and strong structures. Provided you select high-quality materials and follow the technology for preparing the mixture for the task at hand, everything can be accomplished quickly and easily.

Types of compositions and requirements

Despite the fact that any CPS composition includes cement and sand, the final characteristics of the solution can vary greatly. The main parameter is strength, which depends on the ratio of components. The level of strength and resistance of the cement-sand mixture to various influences depends on the scope of application of the solution. Therefore, for different jobs, the DSP mixture is prepared according to a specific recipe.

Types

The proportion of cement and sand affects the characteristics of the mixture. As a rule, one brand of cement is used in conventional mortars. But the brand of cement is not the same as the brand of mortar. So, from M400 cement you can make a cement-sand mortar M150 or M300, taking the binder in a certain volume. On the other hand, to prepare concrete of the required grade, cement grades are taken an order of magnitude higher. The binder is supplied in bags of 25 kg or 50 kg.

Main brands of cement-sand mixtures:

• M100 – the greatest strength, from M200-M500 cement, with a certain volume of sand.
• M200 is the most common type of mixture, suitable for creating surfaces and paths in everyday life, withstands light loads, dries quickly and is not demanding on conditions.
• M300 - floor slabs and foundations of good strength are made from mortar.
• M400 - durable concrete prepared on the basis of M400/M500 cement, used for multi-storey construction, reinforced concrete floor slabs, etc.
• M500 is the most durable concrete that is used in private housing construction (there are also grades M600, M700, but they are prepared for special objects). Withstands high loads, retains its original properties for many years, and is not afraid of external negative factors.

In addition to the above, there are also intermediate grades - this can be a cement-sand mixture M 150, M250, M350, etc. But their characteristics do not differ significantly from those of the main grades of concrete.

Supplements

Before diluting cement with sand (choose the correct proportions, measure everything), you should think about the possibility of using additives that change the properties of the mixture. Additives are introduced into the composition to adapt the mixture to the required conditions and increase/decrease certain indicators. Thus, using additives, you can even obtain liquid glass used for plaster.

Dry cement mixtures, as a rule, do not need modification, but they are also more expensive. But if you decided to prepare the DSP yourself, then the list of possible additives and their properties will come in handy.

What can be added to the sand-cement mixture:

• PVA - makes the solution more plastic and increases adhesion to other materials. Before starting work, you need to select the correct proportions for the cement mortar.
• Lime - only slaked lime is used. The additive slightly increases strength and vapor permeability, but requires strict adherence to the ratios. Most often, lime is added to plaster solutions.
• Graphite and carbon black do not affect the physical properties of DSP, but are relevant in the form of dyes.
• Detergents - improve the plasticity of the solution, are introduced into the mixture after water in exact proportions.

You should think about additives before mixing the mixture, since not all substances can be added after adding water to the composition - some only at the stage of mixing the dry ingredients.

Peculiarities

Dry mix M-300 is a ready-made masonry mixture, the components of which are selected in the required proportions. Before use, the composition is diluted with water in the volume specified by the manufacturer and mixed mechanically until smooth.

The mixture is sand concrete, since it is based on purified fine-grained concrete and Portland cement. The dimensions of the first do not exceed 3 mm; the Portland cement used has a grade strength of M-400 or M-500). To ensure certain characteristics (frost resistance, moisture strength, and so on), plasticizers are introduced.

Various reinforcing fibers may be present in compositions operated at subzero temperatures. To improve adhesion, a special type of clay, coarse sand, or granite chips are sometimes added.

Unlike conventional concrete mortars, M-300 sand concrete is distinguished by its ease of preparation, plasticity (suitable for laying in a thin layer, which is necessary for certain types of masonry), high strength, and economical consumption. The M300 mixture is a masonry mixture, that is, it is used for fixing bricks or masonry stones. In addition, it can be used as a concrete mixture for casting.

The composition is characterized by non-shrinkage, which allows it to be used as a floor screed. And thanks to its increased strength and wear resistance, the mixture is used even when organizing high-strength floors. The thixotropy of the composition allows it to be used also for leveling floors, as well as sealing cracks in concrete surfaces.

The material is suitable for both private housing construction and the construction of industrial and administrative facilities, as well as the installation of basements and garages. It is used when pouring the foundation, including in places where concrete and reinforcing sections meet. The mixture is also used to create paths in private suburban areas. In its properties, the material resembles fine-grained concrete, therefore it is used both outside and indoors.

Errors when using mixtures

Standard factory-produced mixtures balanced in composition provide the required result. But sometimes the desired result does not occur; This could be due to the following errors:

1. Stale mixture. With each month of storage, the properties of cement weaken, and the grade of the mixture decreases.
2. Wrong choice of brand of mixture, for example, a weak mixture for pouring the foundation.
3. Neglect of special conditions, for example, using a mixture without anti-freeze additives at low temperatures.
4. Violation of the conditions of finishing work (each subsequent layer must be equal or decrease in strength in comparison with the previous one).
5. Improper preparation of the base.
6. When preparing CPS yourself, failure to comply with the proportions, use of sand that is too fine or dusty, material contaminated with clay or cement that has lain for a long time.

General information

A characteristic feature of concrete is its composition, as well as proportions and preparation technology. It consists of cement, fine and coarse fillers, water and various additives. In addition, there are brands of concrete that do not contain coarse filler. There are different mixtures that are used for specific cases and also have different properties.

Designation and its interpretation

Concrete structures gain full strength within 6 months, and in 30 days concrete gains 70% strength. M300 is used in all structures that are subject to significant load, therefore, one of the main indicators is its strength. The MXXX designation template does not indicate a specific brand, but is an indicator of the maximum compression pressure.

In addition, there are other designation patterns, for example, FXXX and WXXX, indicating frost resistance and water resistance, respectively. The M300 class of concrete shows the totality of all grades whose ultimate strength is 300 kgf/sq.m. cm. The tensile strength is tested in laboratory conditions by applying force to parallel planes of a product cast from concrete, in the shape of a cube with a side of 150 mm. The grade of concrete in terms of strength is correlated with its class. These indicators should be selected for the construction and calculation of the finished structure at the maximum load that it can withstand.

M300 corresponds to class B22.5 with a coefficient of variation (CV) that is 13.5%. It shows the homogeneity of the mixture from which any brand of concrete is made. When this coefficient changes, the grade of concrete will also change, that is, if its value is low, the grade will increase and vice versa. If the concrete is M300, then with different values ​​of the coefficient its class will change:

1. At Kv = 5% the class is B25.
2. At Kv = 13.5% - B22.5.
3. At Kv = 18% - B15.

Main characteristics

Concrete is classified into grades, and this distribution is primarily related to the parameters of strength (B), density (D), water resistance (W), frost resistance (F) and workability (P). One of the best options for most construction work is M300 concrete, the characteristics of which are as follows:

1. Strength: B22.5 with an indicator of 295 kg/sq. cm.
2. Specific gravity of concrete M300: 1800−2500 kg/cubic. m.
3. Water resistance: W6-W8.
4. Frost resistance: F200-F300.
5. Mobility: P2-P4.

The strength indicator is the main characteristic and shows the maximum effect of forces during compression, at which the structure collapses. The specific gravity or density of M300 concrete depends on the type of coarse filler included in its composition. When using limestone, the D value is about 1800 kg/m3. m., and when using harder rocks (crushed granite, granodirite, etc.) it can reach a value of 2500 kg/cubic. m. Due to its high density, this type is classified as heavy. The density indicator depends on the presence of violations in the manufacturing technology and air cavities.

Water resistance (WXX) is a value indicating the water pressure in MPa to pass through 0.15 m of concrete. For concrete grade M300, this indicator is equal to W5-W6; at a pressure of 0.5-0.6 MPa (approximately corresponding to 5-6 atmospheres) it does not allow water to pass through at all. By adding hydrophobic cement, additives and carefully compacting the solution, it is possible to increase the waterproof rating.

Frost resistance is indicated in the form of the FXXX pattern and shows the number of defrost-freeze cycles without loss of strength. This characteristic can be increased in several ways:

1. The use of additives that prevent the formation of air bubbles.
2. Removing air from the concrete mixture using vibrators, as well as using various compactors.
3. Reducing the amount of water (impairs mobility).
4. Using solid fillers instead of crushed limestone.

Application in construction

Since M300 has good strength, frost resistance, water resistance and mobility, it is widely used in construction. In addition, its main indicators can be adjusted by changing the components included in the concrete mixture. It is advisable to use it for the following work:

1. Construction of platforms, roads and curbs.
2. Installation of walls and various supports.
3. Construction of stairs, landings and pouring of foundations in multi-storey buildings.
4. Production of reinforced concrete products and fences.
5. Production of sewer pipes that are constantly exposed to moisture.
6. Construction of objects that are affected by constant temperature changes.

Calculation of sand-cement dry mixture for screed

The screed is characterized by the presence of increased pressure on the finished site. This characterizes the increased need for screed strength. Therefore, a mixture of M300 or M400 should be used. In some cases, M200 is also used, but only where high strength is not required.

The main nuance when screeding is its depth; the deeper it is, the more mortar will be needed per 1 m2. In general, the screed rarely exceeds 30 cm; an additional layer of crushed stone or gravel is laid below to create a platform.

It is necessary to calculate the number of DSPs after forming a platform from bulk materials, if one is planned.

The required amount of materials can be calculated based on the parameter 1 m3. The area and depth must first be converted into this value. A room with an area of ​​50 m2 and a screed depth of 20 cm will require 50 m2 * 0.2 m = 10 m3.

Calculation for screed

Next, by selecting the grade of mixture required for the task, usually M200 or M300, you can determine the amount of material to be purchased. In addition to the brand, the weight per 1 m3 also depends on the manufacturer and the components that were used.

For M200 per 10 m3, it is necessary to use a flow rate of about 600 kg/m3 * 10 m3 = 6000 kg, while taking into account a draft of 1 to 1.4. That is, you should acquire 8400 kg of mixture for 10 m3 of screed.

For M300 the volume is slightly different: 650 kg/m3 * 10 m3 = 6500 kg. Taking into account some settling when preparing the mixture, the volume becomes approximately 9100 m3.

Regardless of the preparation method (manual or ready-made DSP), such a calculation will help to roughly navigate the amount of materials. But when producing the mixture manually, it is necessary to accurately determine the brand of the solution.

For more information on calculating screed materials, watch the video:

How to prepare TsPS?

Each ready-made mixture must be accompanied by instructions on the required amount of water; other components are usually not provided. When used as part of additional materials (dyes, reinforcing fibers), the proportions must be observed strictly in accordance with the instructions for the additive. The typical ratio of mixture to water is 5 to 1 (a bucket of water per 50 kg bag of mixture), the share of dyes is 0.1%, the share of fiber fiber is 1%.

When making it yourself, the proportions of water and sand to cement are taken depending on the type of work being carried out, strength requirements, and the degree of moisture content of the sand:

1. The thickest mortar required for masonry is the water/cement ratio of no more than 0.8.

2. For screed and plaster, sour cream-like compositions with a W/C ratio of 0.8–1.2 are used.

3. When spraying and grouting, dilute the solution even more, up to W/C - 1.5.

4. Mixtures with W/C less than 0.6 are used when it is necessary to obtain a quick-drying high-grade cement-sand mortar (M300 and higher), or for concrete.

If a concrete mixer is used for mixing, it is recommended to carry out the work in the following order:

• Pour water into the untwisted drum and add additives.
• Add 2 buckets of sand.
• Add a bucket of cement and wait for it to mix.
• Add the remaining sand and add water if necessary.

When kneading by hand, water is poured into the dry mixture. If you do the opposite, water forms a film of cement on the surface of small lumps of the mixture, which will slow down the process many times over. If the composition is made from its own components, it is advisable to mix them dry before adding water.

Once prepared, the solution must be used before it begins to harden - from 15 minutes to several hours, depending on the use of additives, cement concentration and temperature. The usual solution M150-M200 at a temperature of 20 ° C begins to harden an hour after mixing.

Consumption

To plan the mass of the CPS in advance, you need to approximately calculate the required volume of solution and multiply it by the cost per 1 m3 indicated in the description of the mixture. Most often they are indicated in the format “mixture consumption per m2”, meaning a layer 1 cm thick. To get the costs per 1 m3, just multiply the indicated value by 100.

The usual consumption values ​​for sand-cement mixture are 1800 kg/m3, for high-quality compositions - up to 2200 kg/m3, for lightweight plasters with lime - 1200-1600 kg/m3.

Calculating the volume of consumption of mortar for plastering work and screed is not particularly difficult, but the cost of material for masonry depends on the skill of the particular performer. If you strictly follow the technology, the solution consumption will be 25% of the total volume of the wall, but in practice this value can be either up to 35% (thick seams, losses due to splashes) or below 20% (waste masonry, use of poor-quality techniques to speed up work ).

What is a cement-sand mixture?

A cement-sand mixture is a building material consisting of cement and graded sand, usually including additives such as plasticizers or reinforcing fibers. The use of ready-made, factory-made CPS in dry form in bags reduces labor costs for preparing construction mixtures and ensures the correct ratio of ingredients. Due to their ease of use, ready-mixes have become popular among builders.

Interesting!

Fractionated sand is natural or artificially produced sand, sifted through a system of sieves to separate fractions by size: medium, fine, very fine, dusty. The size of the particles matters. For the preparation of cement-sand mixtures, medium-sized sand is preferable.

Dry mixes are sold ready-made, but sometimes they are made independently by mixing sand and cement in a given proportion.

Interesting!

Manufacturers produce dry DSP in bags.

Unlike factory materials standardized according to GOST, when mixing yourself, it is almost impossible to prepare the same mixture twice; Each batch will be slightly different.

Interesting!

For large-scale construction, CPPS is ordered in bulk form with specified characteristics. Factory mixtures may contain coarse sand.

The composition of mixtures is regulated by GOST 28013 “Construction Mixtures” and the international DIN standard.

Peculiarities

Cement mortars with sand are used to perform a wide variety of work during the construction, finishing, and renovation of buildings. It’s not difficult to make a mixture with your own hands, but you need to know the exact proportions of cement, sand and water. The easiest way to mix is ​​to use a concrete mixer, renting or purchasing one.

Before making a solution of cement and sand, it is necessary to decide on the scope of application, since the proportions differ within significant limits. The most popular is considered to be DSP for brickwork: cement-sand mortar is used to create load-bearing walls, and with the addition of lime for internal walls.

The composition of the cement mortar largely depends on the working conditions and operation. If work is carried out in frosty conditions, then special anti-freeze additives are added to the composition to prevent the CPS from freezing. But they are suitable for working in frosts below -20 degrees (it’s better not to do anything at all, but to wait for warmer weather), since they will not be flexible and flexible enough.

If a cement solution is prepared for use in monolithic hearths with an open fire source, in the construction of a furnace or firebox, then heat-resistant fire-resistant mixtures are created: from cement of at least M400 grade, with crushed brick, fine fireclay sand.

For each type of task and working conditions, a solution is prepared from basic materials, but in different proportions and with the addition of additives and plasticizers. As a rule, additives change one parameter - this could be the rate of hardening, mobility, frost resistance, etc. Each master determines priority tasks and performs calculations before preparing the cement mortar.

Advantages and disadvantages of cement-sand mixtures

The popularity of DSPs is due to the advantages that their use provides:

1. Reducing the number of necessary operations when mixing the solution.
2. Convenience in the preparation of solutions (no need to calculate components).
3. The presence of additional additives that provide the required properties of concrete, added in the required percentage.
4. Standardized composition with predictable characteristics.

The disadvantage of CPS is its higher price compared to sand and cement purchased separately.