Plaster mortar: composition and preparation. Mortar for plaster How to prepare a mortar for plaster

Plaster or a layer of finishing material applied to the surface during construction work is a mandatory step prior to finishing.

This is a specially prepared one that, after drying, hardens, forming a hard, even surface, ready for final processing.

In most cases, it is used to correct any defects, as well as to seal technological channels formed during the repair process, for example, when laying new wiring. The surface becomes even, smooth and aesthetic.

The exact proportions of the mortar for wall plastering allow the prepared mixture to perform its function after drying and not crumble over time. To choose it correctly, you need to have a general idea of ​​the types of building mixtures and their purpose. Knowledge of their main components and application possibilities will allow you to easily navigate the existing range and correctly apply the solution for their use.

and their features

Wall decoration can be used outside or inside the room and is divided into three main types:

• standard, as protection against environmental influences (external walls) or correction of surface defects, including leveling, sealing cracks, technological channels and preparation for final finishing with finishing decorative coatings, as a rule, thin-layer;
• protective, acting as an insulator or screen, for example, suppressing noise, retaining heat, or preventing the penetration of radiation;
• decorative, used during the finishing coating (color, stone, Venetian, graphite).

Each type is characterized by a certain composition, the preparation of which requires the exact proportion of mortar for wall plastering.

What is building mix

To prepare a wall plaster mortar, the proportions must include the binder (cement, lime or gypsum), the aggregate, usually sand and water.

Depending on the amount of binder component, they are:

• skinny, characterized by the absence of cracks, but poor strength;
• greasy, able to crumble and shrink.

Skinny mixtures easily slide off the trowel, while greasy ones, on the contrary, stick to it. The task of any builder is to prepare a solution for plastering walls, the proportions of which will be optimal.

In addition, a plasticizer is necessarily added to the finished solution, which makes it easier to work with the mixture. The simplest option is ordinary liquid soap or laundry detergent, but there are also special industrial additives.

Number of layers

The application usually takes place in three layers, which have individual proportions of the wall plaster solution:

• the first (spray) is applied with a layer of at least 5 and no more than 9 mm when filling all the irregularities and looks like sour cream;
• the second (ground) is the main layer, which can be applied several times and has the density of the dough;
• the third (covering), is applied with a layer of no more than 4 mm, always on a damp surface, similar in consistency to a spray.

When preparing a mortar for wall plastering, the proportions differ in the amount of binder, most often cement. In the first layer there is very little of it, in the second the amount increases and in the third it becomes maximum.

Types of mixtures

When decorating walls, several basic types of compositions are used. Today, three mixtures are mainly used:

• cement, the most common and popular, is characterized by the greatest strength, but a long solidification period;
• clay, used during internal and external work in the processing of wooden surfaces;
• lime, an inexpensive analogue of a cement mixture, often used with gypsum, accelerating the setting period and increasing strength.

In addition, depending on the situation, other options may also apply:

• gypsum - the most rarely used due to the rapid (within a few minutes) initial solidification and complete fixation after half an hour;
• mixed - characterized by the use of several special components at the same time;
• special - used with a certain additive, depending on the goal.

One of the important indicators that determine the type of solution you need is the level of humidity. Depending on the microclimate, the desired composition is selected. The most versatile and common is the cement mortar for plastering walls, the proportions of which are known even to an amateur, and allow it to be successfully used both outside and inside the room.

cement mortar

The most reliable, simple and ubiquitous way. To do it, you must strictly follow the order.

Work begins with the preparation of all components and, first of all, sand. It must be dried, and then be sure to sift. Then carefully clean all lumps, especially clay ones. It is not advisable to use red or red sand, this lowers the quality of the finished mixture and its performance properties, and it is generally impossible to use unsifted and uncleaned sand.

After sifting, you can start preparing for plastering the walls. The proportions vary depending on the type of cement used. For example, using the M400 brand, 4 sand components are enough for 1 part of cement. If an M500 is used, the number of parts increases to five. Violation leads to loss of quality finish and is not allowed. Dry components are thoroughly mixed in a pre-prepared container. This can be done using a mixer inserted into a hammer drill, shovel or concrete mixer.

The choice of method depends on the required volume. If you have to work independently, it is enough to use a large construction bucket of 15 or 20 liters, in which you can prepare a solution for plastering walls with your own hands, the proportions remain the same. If the work is done by several people, it makes sense to use a large trough or a concrete mixer.

Water is gradually added to the thoroughly mixed mixture, bringing the composition to a state of thick sour cream.

Features of lime mortar

In order to reduce costs, cement is sometimes replaced with slaked lime, which has almost no effect on quality. Moreover, the proportions of lime and cement mortar for wall plastering are almost the same.

Its peculiarity lies in the use of only It is quite simple to do at home at no special cost.

The acquired lime is poured with warm, but not hot water in a large container, and after the reaction is completed, it is filtered, usually through gauze. It can be used no earlier than a day later.

lime mixture

Preparing the solution also involves following the sequence.

First, lime is cleaned of lumps by stirring. The use of water or sand in small quantities is allowed. Having received a homogeneous composition, you can proceed to the preparation of the mixture.

The required composition is obtained if three sands, previously sifted and cleaned, are put on one part of the lime mass. Along with the sand, water is gradually introduced. This continues until the solution resembles a thick homogeneous mass. After that, it can be used for 12 hours.

Features of lime mortar during outdoor work

Usually lime mixture is used only in dry climates. If the processing time of the facade is limited, the proportions of the mortar for plastering the exterior walls include a small amount of gypsum.

This allows it to begin to harden within a few minutes, completely hardening in half an hour.

To make a solution, 1 kg of gypsum is added to 3 liters of ready-made lime mixture. But it is necessary to take into account the hardening period and the amount of work, otherwise it will harden ahead of time.

clay mortar

The use of clay is still quite common in wooden houses. To prepare a strong clay mortar for wall plastering, the proportions should include cement, lime or gypsum.

You will need alumina, preferably fatty, which is soaked for several hours. It is important to constantly stir the mixture and add water until it becomes thick.

The easiest way to prepare it is to add sifted sand in a ratio of one to three. But it is not particularly durable. This is corrected by adding 1/5 parts of cement to these components. At the same time, cement and clay, that is, binders, are first mixed, and only then sand.

Sometimes cement is replaced by lime, but with a mandatory increase in the part to 1/2. You can also add gypsum, but not more than 1/4.

Component ratio

The proportions of different components in the finished solution always differ, depending on the task and the type of layer. Typical ratios are shown in the table below.

The specified proportions are not constant and can be adjusted in each individual case.

Ready dry mixes

Today, almost all manufacturers provide a wide range of ready-made dry mixes. All that is needed before starting work is to take the required volume of water and the finished dry solution, after which everything is thoroughly mixed, usually twice. The mixture is ready to use. As a rule, they are always slightly more expensive than the cost of the included components if purchased separately.

Their main advantage is that there is no need to mix several different elements in the right proportions. In addition, the sale is made in large quantities, which is not always convenient. For example, it makes no sense to buy a bag of cement weighing 25 kg if you need to patch up a small hole in the wall. Therefore, with a small amount of work, a ready-made dry mix will be a good alternative.

Working with plaster

Properly selected proportions of mortar for plastering interior or exterior walls are one of the key points of any repair. But even the ideal ratio will be useless if the plastering is carried out in violation of the rules for applying to the surface. Therefore, it is necessary to pay attention to all stages without exception. Only in this case can a positive effect be expected.

The sequence, thickness and number of layers is as important as the composition. A mistake can lead to the most unpleasant consequences. The application is carried out with a special tool, with a mandatory time interval provided for each type of mixture.

With minimal experience in carrying out such work, it is recommended that a mandatory number of trial attempts be made in small areas in order to assess one's own capabilities.

Tools and specifics of individual surfaces

If the work is done by hand, you will need a certain construction tool:

• rule;
• Master OK;
• level;
• spatulas of different sizes;
• cord;
• grater for grouting.

The application of the first and second layers is carried out with a trowel, the third - with a spatula. Typically, the first layers are applied to an auxiliary mesh for reinforcement. When applying the finish coating, a gypsum mixture is used.

Surfaces with large differences are processed using special building beacons, which facilitate the process of applying and leveling the plaster.

Plastering is a traditional way of leveling the walls of buildings under construction and preparing them for finishing, which is mandatory in the construction of any premises, both internal and external. In the recent past, such work was carried out in the same way using the same materials. Today we have a wide range of materials for plastering work, and finishing technologies do not stand still. To avoid errors, it is necessary to prepare a quality solution for these purposes.

Types and characteristics of plaster solutions

For plastering, a solution is made consisting of a binder component and aggregate. Clay, lime or cement can act as a binder, the choice of one of them depends on the nature of the work to be done and the place where it is carried out (inside the task or outside). Sand is traditionally added as a filler. If aggregate is not added to the binders, the plaster will be fragile, and the surface treated in this way will become covered with cracks. So, the following plaster solutions are distinguished:

• cement and cement-lime - used for external facade plastering of the surface of walls and basement, subjected to constant moisture; for internal work - when working in rooms with high humidity - bathrooms, kitchens, toilets;
• lime, lime-gypsum and lime-clay - used for exterior decoration of walls that are not subject to systemic moisture, as well as for internal plastering of rooms in dry rooms;
• clay, clay mortar with cement and clay with gypsum - they are considered quite suitable for interior plastering of premises with an air humidity level not exceeding the norm, and for exterior plastering of wall surfaces in areas with a dry climate.

How to define quality

When preparing a good quality plaster mortar, the raw materials should first be sieved through a construction sieve so that it is not necessary to filter the already prepared mortar, which in itself is more time consuming. A high-quality mixture, ready for use, must have a uniform consistency, the necessary fat content, be well fixed on the plastered surface, and not crack when it dries.

Distinguish plaster mortars of high fat content, normal fat content and lean.

You should be aware that greasy solutions have an increased content of the binder component, this leads to a high degree of cracking and shrinkage of the plastered surface. Normal solutions are characterized by a balanced content of all components. And lean plaster mixtures are characterized by an excessive content of aggregate, leading to insufficient strength of the plaster layer, although the surface does not crack or shrink.

To determine the fat content of the working solution for plaster, you can use an oar to mix its components. To do this, by mixing the components, we determine how the plaster mixture behaves:

• sticks too much to the mixer - we got a greasy solution, filler should be added;
• the degree of sticking is medium - we have a composition with normal fat content;
• does not stick at all - we have a lean solution that requires the additional introduction of an astringent component.

Lime mortar

1. Lime mortar, which includes lime paste and sand in a ratio of 1: 3, is brought to the required condition by adding water with thorough mixing of the entire composition. When ready, it should resemble the consistency of a thick, viscous dough.
2. In order to give the plaster mortar strength, 1/10 of this volume of cement is added to a ten-liter volume of lime plaster mixture. Thus, a cement-lime mortar is obtained. The above-mentioned lime-based compositions harden slowly, which allows you to work with them for 2-2.5 days.
3. Lime mortar with the addition of gypsum (mix 5 parts to 1 part, respectively) is more durable, and it hardens after 6 minutes, full hardening occurs after half an hour. This creates certain difficulties and requires special skills, but the plaster will be durable.
4. Lime-clay mixture for plaster is prepared from clay and lime dough taken in a 1: 1 ratio with the addition of five parts of sand. This plaster is an order of magnitude stronger, both lime and clay.

clay based

1. Clay mortar for plaster is prepared in a special way, after wetting the binder component and covering it with a dense cloth. The swollen clay (1 part) is mixed with sawdust (3 parts) and, adding water, bring it to the desired consistency by stirring. The disadvantages of the clay solution are its fragility and instability to high humidity.
2. In order to make the clay mortar stronger, cement is added to it (1/10 of this volume of cement is introduced into a ten-liter volume of clay plaster mortar). In this way, a solution is obtained with the addition of cement.
3. Clay mortar with gypsum is obtained similarly to lime-gypsum, only clay dough is taken as the main binder component.

Based on cement

Cement-based plaster mortars are mainly used for the treatment of walls that are often exposed to moisture, both indoors and outdoors.

1. The cement mortar is prepared by mixing cement with sand in a ratio of 1:3, 1:4 (depending on the purpose of use), which are diluted with water and, actively stirring, bring to the desired condition. Use the prepared mixture for no longer than one hour. Exceeding this time of work with cement mortar leads to a decrease in its quality.
2. Cement-lime mortar is prepared by mixing one part of Portland cement marked M400 or M500, ½ of lime paste and two parts of washed sand.

This type of solution is prepared in two ways:

• after mixing the lime dough with sand, cement is added to the resulting mixture, after which, stirring the composition intensively, water is poured until the required consistency is obtained;
• having made a mixture of sand and cement, mix the solution thoroughly, add milk of lime (obtained by combining 1 part of water and 1 part of lime dough).

Use of modern materials

Today, more and more often, during construction or during repair work, high-quality dry mixes for plaster are used, the basis for which is Portland cement. These mixtures, as a rule, are enriched with various polymer additives that enhance the plasticity of the solution, its adhesion to the working surface and increase the strength of the plaster. Such characteristics of the dry mix provide it with a number of advantages:

• allow you to do without reinforcing mesh and significantly reduce the consumption of plaster;
• make the plaster elastic, which ensures its soft response to weather changes - temperature or humidity changes lead to a change in its shape, and not to deformation;
• allow plastered surfaces to pass air and not collapse from moisture penetration.

Building dry mixes intended for the preparation of plaster solutions were developed by technologists in laboratory conditions, which ensured the accuracy of the proportions of the incoming components, the homogeneity of the mixture and absolute readiness for use. For the average consumer, the opportunity to prepare a solution, guided by a clear instruction: "Add water and work", is worth a lot.

Modified dry mixes - the achievement of innovative technologies - allow the use of new thin-layer technologies, the preparation of a solution for plastering in the right volume as needed, which, in turn, makes it convenient to use and significantly reduces costs.

In each case, each surface requires its own type of plaster mortar. When making it, it is necessary to use high quality components, because the quality of the mortar depends on this, and ultimately the quality and durability of the treated surfaces.

Video: preparation of plaster

Plaster mortar is an indispensable material for repair, insulation, leveling and even decorative finishing of various surfaces inside and outside the building. But for each type of work, a certain composition is used.

For example, lime mortar for plaster is excellent for leveling internal walls (see how to make it correctly) - the proportions and ratio of all its components may be different. What do they depend on and how are they selected?

Types of plaster solutions

First, let's find out what components in general can be part of protective and leveling mixtures, and what they are. Mandatory ingredients are water and sand, which acts as a filler.

And the main properties depend on the binders, which can be cement, gypsum, lime or clay. Their proportion for plaster relative to water and filler determines the quality of the solution.

Component specifications

To understand why one solution is used for plastering the basement, another for facades, and a third for internal walls, you need to know the properties of the materials from which it is made:

• Sand. It differs in the size of the fractions and the place of production. Pure river sand is considered the best for plastering, but it is also sieved before use to remove impurities and large particles.
• Cement. After solidification, it acquires high strength, resistance to water and atmospheric influences, well resists serious mechanical loads.

For reference. Cement comes in different grades: 50, 100, 200, 300, 400, 500, 600, 800. These numbers indicate the material's resistance to compressive force, expressed in kg / cm 2.

• Lime. It can be slaked, quicklime, white, gray, etc. Durable, slow curing material showing good performance in dry areas. But not water resistant, poorly resists weathering.

• Gypsum. A fast-hardening material with low strength and poor resistance to moisture - it quickly absorbs it, losing its properties. Can be added to lime to speed up setting, but not compatible with cement.

Types of solutions

The composition of the plaster is selected depending on where and on what surfaces it will be applied.

This takes into account the above properties of the components:

• Lime (see We prepare ourselves a solution for lime plaster). The proportions for the plaster solution depend on the fat content of the lime paste: two to five parts of sand are added to one part of it. First, these components are mixed in equal proportions, then water is added and mixed until lumps are eliminated, after which, if necessary, sand is poured in portions until a solution is obtained that resembles a viscous and thick dough in consistency.
• Lime-gypsum. In addition to sand and lime, it includes gypsum, which accelerates the hardening of the mortar and complicates working with it, but the surface also acquires greater strength. Gypsum is usually taken one part to five parts of lime.

Advice. If you are going to plaster with your own hands, remember that such a solution begins to harden after 5-6 minutes, so you need to prepare it in small portions and use it quickly.

• Lime-cement. Adding lime to cement mortar increases its heat-saving properties. The ratio of cement-lime plaster may be different depending on its purpose. They are listed in the table below along with the proportions for other plasters. But you should be aware that lime absorbs moisture from the solution, therefore, to prevent its rapid drying, the finished surface must be covered with plastic wrap, otherwise cracks will appear on it.

Note. Lime significantly prolongs the setting time of the cement mortar, it can remain viable for up to two days.

• Cement. This is the most commonly used plaster mortar with a wide range of applications. They finish the facades and plinths of buildings, walls in utility rooms, as well as in residential ones, characterized by high or unstable air humidity (see Let's consider how to plaster with a cement-sand mortar). It is worth talking about it in more detail.

What you need to know about cement plaster

The main thing to remember: the proportions of water-cement-sand in plaster depend primarily on the brand of cement. The higher it is, the less binder is required to prepare a solution of one brand.

As a rule, the instructions for performing a particular type of work contain information about which brand of plaster solution is required in a particular case. The highest M100 is obtained by mixing one part of M400 cement and three parts of sand. The amount of sand decreases with an increase in the grade of cement and increases with its decrease.

Since the price of high-grade cement is higher than low-grade, and sand is cheap or even extracted independently on the banks of rivers, it makes sense to buy binder of the most popular grades M300 and M400 to reduce costs while maintaining the required quality of plaster, rather than spend money on expensive material.

Failure to comply with the proportions leads to a change in the properties of the plaster:

• If there is too much cement (greasy solution) in it, then when it dries, it will shrink strongly with the formation of cracks;
• If you shift the sand (lean mortar), then most likely there will be no cracks, but the coating will not have sufficient strength either.

How to prepare a plaster mortar

The preparation of a plaster mortar is also not an easy task, it must be done according to the rules. If everything is clear with ready-made mixtures: they are simply poured with the right amount of water and mixed, then with self-production, everything is not so.

First you need to prepare the dry mix itself, determining the proportions for plastering brick, concrete or other surfaces, taking into account their location (inside or outside, in a dry or damp room).

So:

• Dry ingredients are poured into a mixing container. It can be a plastic, metal or wooden box with a flat, smooth bottom. And first, sand is poured, and astringents are poured on it in an even layer.
• All ingredients are thoroughly mixed with a shovel or trowel, if the volume is small.
• Then the mixture is leveled and look at its color. It should be homogeneous, without streaks and stains of the binder.
• If this is not the case, mixing is continued until an even color is obtained.
• Then the dry mixture is poured with water or lime milk, allowed to soak in and mixed well. You can do this manually or with a construction mixer.

It is important that there are no lumps left in the solution, and no unmixed dry matter in the corners of the container. The viability of a solution depends on its composition. The longest "live" cement-lime, and gypsum should try to use as quickly as possible.

Conclusion

Not a single repair or construction is complete without building mixtures, and the most popular is plaster. If you know how to prepare it correctly, then you will not have problems with either its application or the quality of the finished surface. To get more useful information on this topic, we recommend watching the video in this article.

Additives used in plaster solutions give them certain properties and often reduce the consumption of high-quality binder. Depending on the properties, additives can be divided into active mineral additives, fillers, surface-active and special additives.

Active mineral additives are divided into natural and artificial. The natural ones include diatomite, gliezh, tuff, pumice, tras, while the artificial ones include blast-furnace granulated slags, belite (nepheline) sludge, and acid fly ash.

Active mineral additives are used to increase the density, water resistance of solutions, as well as for the preparation of heat-resistant solutions based on Portland cement (blast-furnace slag, fly ash, pumice).

A mineral additive is considered active "if it provides the end of the setting of the dough prepared on the basis of the additive and lime-

fluffs, no later than 7 days after mixing, the water resistance of a sample from this test - no later than 3 days after the end of setting £fo, the absorption of lime from lime mortar - within 30 days. The fineness of grinding should be such that the residue on sieve No. 008 does not exceed 15% of the mass of the sample.

Filler additives are used to impart density, workability to mortars, as well as to reduce cement consumption. They are divided into natural, obtained from rocks (limestone, igneous rocks, sands and clays), and artificial, obtained from industrial waste (blast furnace slag, fuel ash and slag).

The fineness of grinding of the filler additive should correspond to the residue on sieve No. 008, not more than 15% of the sample weight. Additives used only to thicken the solution may be coarser grinding. The greatest application in plaster solutions found additives-fillers in the form of clay. With such additives, solutions are prepared for plastering the outer and inner surfaces of wooden and stone walls of buildings erected in the dry zone of the USSR, with a relative humidity of air in the room not more than 60%.

Surface-active additives are substances that can change the relationship between water and the surface of the binder particles. They are divided into hydrophilic-plasticizing, hydrophobic-plasticizing and microfoaming.

Hydrophilic-plasticizing additives include sulfite-alcohol stillage concentrates. Concentrates are produced in liquid (KZHB), solid (CBT) and powder (CBP).

Hydrophobic-plasticizing surfactant additives include organosilicon liquid (GKZH-Yu, GKZH-11. GKZH-94), mylonaft, asidol and asidol-mylonaft.

Organosilicon liquids KGZH-Yu and KGZH-11 are a water-alcohol solution of sodium methyl and ethyl siliconates. 0.5-0.2% liquid by weight of cement is added to the solutions. Silicon-organic liquid GKZH-94 is a product of the hydrolysis of ethyl dichlorosilane. 0.05-0.1% of it by weight of cement is added to the solution.

Mylonaft is a water-insoluble organic acid soap. Store it in tanks, barrels, cans or glass bottles, protected from direct sunlight and precipitation. Mylonaft is used as a plasticizer for cement mortars. Its consumption is determined empirically. Usually it is about 3 liters per 1 m3 of mortar, or 0.05-0.1% by weight of cement.

Asidol - petroleum acids extracted from alkaline waste during the purification of oil and solar distillers. It is insoluble in water. Asidol is produced in two grades: A-1 (asidol 50) and A-2 (solar). 0.05-1% asidol by weight of cem'eite is added to the solution.

Asidol-mylonaft is a greasy, yellow or brown substance, poorly soluble in water, which is a mixture of free water-insoluble organic acids extracted from wastes of alkaline purification of kerosene, gas oil and solar oil distillers with their sodium salts. Three grades of asidol-myloiaft are produced. 0.05-1% of it by weight of cement is added to the solution.

Microfoaming additives include microfoaming agents BS and OS, as well as soap liquor. Microfoaming agent BS is a powder containing neutralized (saponified) fatty acids of animal or vegetable origin (protein waste from slaughterhouses, crop stalks, etc.). 0.05-0.1% BS is introduced into the solution by weight of cement. OS microfoaming agent - a mass of black color, containing from 10 to 45% saponified fats, is a waste of soap factories. It is used in the form of an aqueous emulsion with a composition of 1: 40, obtained by dissolving OS in water heated to a temperature of 90 ° C. It is added to solutions of 0.25-0.5% OS by weight of cement. Soap liquor - soap production waste containing from 0.5 to 3% fatty acids. Depending on the content of acids, the consumption of soap liquor ranges from 0.3 to 12 liters per 1 m3 of solution.

Special additives include cement hardening accelerators, binder setting retarders, additives that increase water resistance and improve the thermal properties of plaster. Hardening accelerators include calcium chloride, sodium chloride, calcium nitrate, potash, alumina sulphate, ferric chloride, building gypsum. They are used for solutions where cements are astringent (except for aluminous cement). Hardening accelerator additives are used in cases of plastering works at low temperatures.

Calcium chloride and sodium chloride give efflorescence on plaster, so their use is limited. The best supplement is Po-Tash. Powdered additives - calcium chloride, sodium chloride and potash - easily dissolve in water. Their consumption depending on the density is given in table. 2.

table 2

Acceptance of additives and chemicals is carried out according to a passport or certificate, which indicates the number and date of issue of the certificate passport, the manufacturer, the name and address of the recipient, the number, weight and date of dispatch of the batch, the number of the wagon and the waybill, the name of the additive or chemical, the date of manufacture, number of GOST or TU, batch test results, technical characteristics. When accepting chemicals, it is necessary to check that the packaging is not damaged and that the material is not contaminated. Additives should be stored in closed containers.

Binder retarding additives include gypsum, ferrous sulfate, and surfactants (animal glue, soap naphtha, etc.). Setting retarders are used when the rate of hardening of the solution without additive does not provide the necessary workability.

To slow down the setting of gypsum mortars and mastics, animal glue (mezdrovy or bone) is most often used. In this case, the setting delay is up to 40 minutes. How to obtain

gypsum setting retarder from animal glue is as follows: one part (by weight) is soaked for 15 hours in 5 parts of water. 2 parts of lime dough are added to this mass and the mixture is boiled. Before use, this concentrate is diluted with water at the rate of 9 liters of water.

1 kg of concentrate. It turns out a 10% retarder.

To make solutions waterproof, ceresite is usually used - a creamy or curd-like mass of white or yellowish color. For the use of ceresite in winter, in order to lower its freezing point, about 10% of denatured alcohol is introduced. Ceresite is supplied in wooden barrels. It must be stored in a cool place, protected from sunlight. In winter, ceresite should be stored in rooms with a temperature of at least 0 ° C.

To give color to decorative plasters, dry paints (mineral and organic pigments) are introduced into the solutions. They must have the following properties: do not dissolve in water, do not change color when mixed with a solution, slightly reduce the strength of the solution, be light-, alkali-resistant and non-poisonous.

Organic pigments are mainly used in the production of colored and textured plasters indoors. Such plaster cannot be subjected to moisture.

Plaster is an integral part of the finishing of walls and ceilings. How long we do not need cosmetic repairs depends on its quality. The quality of the plaster mixture itself, and then the plaster coating, depends on the composition.

Cement plaster mixes

Cement plaster mixtures can be divided into two types:

• Cement-sand, used for leveling and finishing any surfaces, except for concrete. Adhesion with such a base for cement plaster is poor.
• Cement-lime, used in the decoration of brick, concrete and ceramic surfaces

Both plaster compositions necessarily include special polymeric additives and mineral fillers, which make the finished mixture more plastic, heat and frost resistant, and enhance its astringent and adhesive properties.

We prepare plaster

You can make a plaster mortar from a ready-made mixture, or you can do it yourself. We add medium fraction sand and a little liquid soap to the composition of the cement mortar, which prolongs the time of working with the mortar.

Below are the proportions of cement mortar for plaster. The composition of the cement-sand mixture:

• 1 part cement;
• 3 parts sand;
• water to the consistency of thick sour cream;
• liquid soap

The composition of the cement-lime mixture:

• 1 part cement;
• 3 - 5 parts of sand;
• 1 part of lime dough (one part of quicklime + three parts of water. Pour lime with warm water, wait for the reaction to start, add more water and mix. Close and let ripen for one day. Then dilute with water to a liquid state, drain into the prepared pit, in a day we pour sifted sand on top, and on top of the earth. The maximum layer of sand and earth is half a meter. In the pit, lime is aged from 15 to 20 days, after this period, lime dough is obtained, which is used in the preparation of plaster cement-lime mortar.);
• liquid soap or soap solution.

The preparation of a cement mortar for plaster consists in mixing sand and cement in the required proportions. The resulting dry mixture is gradually poured either into water or milk of lime, add liquid soap. By appointment, we adjust the amount of liquid - for spraying walls, a weaker solution is required, for rough plastering of walls after spraying - a thicker one.

To prepare a cement mortar for wall plastering, it is enough to know the exact proportions of cement, filler and liquid, as well as follow simple rules.

1. We take a clean box with a flat, smooth bottom.
2. We pour clean sifted sand to the bottom.
3. Pour cement on top.
4. Thoroughly mix the dry mixture, then level it with a rake.
5. We repeat point 4 several times.
6. We carefully look at the finished mixture, it should be a uniform color.

Advice. Prepare the working mixture in small quantities. After forty to fifty minutes, it will seize and begin to lose its properties, and the coating will turn out to be of poor quality.

There are three types of ready-made plaster mixes prepared from factory dry ones. Their quality is determined by the trowel lowered into the container with the finished mixture.

1. Fatty. Too sticky, strongly sticks to the trowel. As it dries, it will crack and shrink. We adjust the ratio of the finished mixture and the filler, adding it and stirring thoroughly until we get the desired consistency.
2. Normal. A thin layer of cement mortar remains on the trowel.
3. Skinny. The presence of the mixture is barely noticeable on the trowel. In this case, the ratio of dry mix and liquid must be corrected towards cement by adding it and stirring thoroughly.

In the photo in this article you can see how to properly knead the solution.

Advice. When preparing this kind of mixture for plaster, use only slaked lime. Quicklime, when water is added, will enter into an uncontrolled reaction with it and it is not a fact that it will be completely extinguished. In the future, the remaining pieces of unslaked lime will come into contact with moisture, which will lead to gaps in the plaster coating.

Plaster mixtures, where there is little cement and too much sand, have little plasticity and are very inconvenient to use, therefore the optimal ratio of cement and sand is 1: 3. We use cement brand M400, it gives the best result.

Application of cement plasters

Cement-based plaster mixtures are considered universal, as they can be used for both indoor and outdoor work, they are resistant to moisture, and have good vapor permeability. You need to know that such a mixture dries for about 4 weeks. But it must be processed no later than an hour after application.

Advice. The layer of plaster on the outer walls of the building should be twice as thin as on the inner ones. Thus, the normal vapor permeability of the walls is observed, fungus does not form on them and condensate does not collect.

In addition to the correct composition and kneading of the plaster mixture, it is necessary to properly prepare the base, otherwise all the work will go down the drain and everything will have to be started all over again.

Here are some tips for preparing the base (using a brick wall as an example).

1. It is necessary to level the surface and peel off the dried cement (if any).
2. Then we carefully embroider the seams of the brickwork (if there are any voids and recesses, we leave it as it is).
3. We remove dust, if there are greasy stains - wash them off, wipe the surface with a damp sponge and let dry.
4. We cover the base with a primer and let it dry.
5. We prepare the mixture for plaster and proceed to the application. We work from the bottom up and from right to left.
6. After about 40 minutes, we proceed to the final alignment.

Advice. It is not recommended to work at temperatures above + 25 and below +5 degrees, as well as in rainy weather. If you still had to plaster in hot weather, it is recommended to moisten the finished surface regularly to avoid premature drying and cracking.

Starting to repair, you need to decide for yourself how much effort you are willing to spend on it. Perhaps the best solution for you would be to buy ready-made cement mixtures from well-known manufacturers.