Cement gypsum mix proportions. Which plaster is better - gypsum or cement: characteristics of building mixtures. Dry mix cement based

Finishing work for leveling surfaces various materials. Depending on the location of the surface, the purpose of the room, environment compositions with different properties are needed.

What kind of plaster better fit plaster or cement, should be decided in each case individually. Correctly chosen qualitative composition provide long service life and aesthetic appeal plaster finish. How to choose suitable solution what are the advantages and disadvantages different formulations consider below.

Types of compositions

Plastered surface ready for finishing

Plaster mortar has various applications. The most obvious are:

surface leveling;
improvement of heat and sound insulation;
fire protection.

The modern construction market offers different kinds ready mixes for finishing of walls, ceilings, internal and external works. Plaster solutions are divided into 2 groups depending on the application layer:

regular or basic coverage. It is used when carrying out rough work;
decorative. Various mixtures to create a finishing touch.

The main way to classify plaster mixtures is the separation of solutions according to the constituent substance:

cement;
lime;
clay;
gypsum.

Of course, there are various modifications of the compositions, except for the 4 main ones. They are obtained by mixing the main components and adding various additives, additives and plasticizers.

Thanks to their practical properties, the most popular compositions are gypsum and cement plasters.

Quality criterion	Gypsum	Cement
Base material	gypsum	cement
at manual way drawing	10	17
with mechanized	8	12,5
Drying time	up to 7 days	up to 4 weeks
Shrinkage	No	1 - 2 mm/m

Characteristics of the cement mixture

Cement mixtures have high adhesion to the base

Convenience and optimality cement plaster It is difficult to overestimate, this type of solution is well-deservedly popular among both experienced craftsmen and novice builders:

Coating strength. This is the main quality of cement plasters, the surface is resistant to mechanical stress and reliable.
Excellent adhesion. Cement mortars fit perfectly on almost any base, it is enough to treat the surface with a primer.
Moisture resistance. Cement plaster is not afraid of impacts precipitation and high humidity, therefore they are often used in the repair of facades and surface finishing in specific wet rooms.
Price. This composition has a quite budget price tag compared to other compositions.

Given that this a budget option, you should not choose a solution based only on the cost of the goods: compare the material consumption and pay attention to the operational properties.

Main disadvantage cement mortar- This is a poor adhesion to wooden, plastic or painted surfaces.

Due to the serious weight of plaster, it is rarely used on ceilings.

For the same reason, the load on the walls of the building during finishing should be calculated.

The plastering process itself is quite labor-intensive, despite the fact that it takes place in several stages, each of which requires a pause in work.

Engage in plastering at positive temperatures

To make the plaster layer as strong as possible and serve long years, you should follow some rules in the work:

plaster the surface at a temperature of + 5 to +30 0 С;
be sure to treat the surface with a deep penetration primer;
to apply an additional layer, you should wait for the previous one to dry;
conduct plastering work on construction beacons;
do not take on large volumes if there is no experience in this area.

Gypsum-based mixture

Gypsum plaster mixture consists of gypsum itself and plasticizers. It is applied, as a rule, in 1 layer by hand or by machine. The scope of the gypsum solution is quite extensive, although it has limitations. This type of plaster is used when finishing:

brick walls and concrete slabs;
indoor dry rooms;
for leveling the surface for gluing or painting.

Finishing the surface with gypsum mortar will eliminate the need for puttying work. High-quality work with plaster makes the surface absolutely suitable for decorative finishing.

The advantages of working with this type of composition:

The material is warm and dries quickly, it takes a maximum of 3 days to complete the work.

The disadvantages of gypsum plaster include the impossibility of using the solution in rooms with increased level humidity.

The price tag is slightly higher than that of cement mortars, which is offset by the fact that there is no need to use putty.

Preparation of solutions

Dry ingredients are mixed first, then water is added.

It is not enough just to choose a cement or gypsum plaster, for use, it is necessary to properly prepare the solution. Each type of plaster has its own recommendations for the mixing process.

Bulk components cement composition mixed dry. Sand and cement are poured in thin layers, and then mixed.

After the dry ingredients are thoroughly mixed, water is added to them. Now the liquid mixture is thoroughly kneaded.

You can also prepare cement-gypsum plaster. This solution will set much faster, drying time will be reduced. But at the same time, the strength of the layer will also change, it will become more fragile. For more information on how to make a mixture, see this video:

Gypsum mortars are kneaded within a short time. It takes no more than 5 minutes to prepare a working portion of the composition. Usually, a gypsum dough is first prepared, which is subsequently diluted with water to the desired consistency.

I can unequivocally answer this question, it is impossible to add gypsum to the cement mortar, even in small quantities. Although they say that in the production of cement into clinker, this is an intermediate product, a small amount of gypsum is added one or two percent, but I'm not strong in chemistry, I don't know. But I have extensive experience in plastering with cement-sand mortar with the addition of gypsum.

I even had to work for such unscrupulous foremen who, apart from this "ominous mixture", did not work with anything else. Why is this needed? The speed of work increases five to ten times, and as you know, the faster you hand over the object, the faster you get the money. And do not think that only small private traders are guilty of this.

The plaster layer made with a cement-gypsum mixture after a while, one to five days, depending on the base, begins to become covered with a web of very small cracks, they can be seen if the surface is well primed with a primer. It is possible to putty and forget only if the base is made of red brick, and the plastering work was carried out indoors. But in most cases, gypsum is added to cement when plastering. concrete bases, on red brick, plaster sets quite quickly even without gypsum.

The favorite excuse of such plasterers, if the cement-gypsum plaster layer is rubbed from above with a solution without gypsum or puttyed with facade putty, then everything will be in order. This is a pure lie, checked more than once, does not help.

Each layer of cement-sand plaster, on concrete wall, it will set from 5 to 10 hours, and there may be several such layers. The addition of gypsum allows the job to be completed in one pass, the plaster will become hard (but not dry) in 5 to 10 minutes. Such plaster will not last long, indoors up to 5 years, on the street it will not survive the first winter. If a metal mesh was stuffed under such plaster, it will begin to rust very quickly in 3-6 months. outdoors and for several years indoors (depending on humidity), and traces of rust will constantly appear on the surface.

Previously, 50 - 80 years, there was a practice, when plastering the ceiling, upper slope, etc., add gypsum to the cement - sand mortar, at that time it was only decision, even in the educational literature of that time you can find a recipe for this plaster. Currently, to increase the plasticity of the solution, plasticizers and a number of other additives are used to improve the setting of the solution, and gypsum is added to the composition of the cement-sand plaster mixture just to save money.

It is very difficult (long) to plaster the ceiling or the upper slope with cement-sand plaster, in such situations I add to cement-sand mortar tile adhesive (1 to 5 or 8). This facilitates the work of the plasterer and saves on plaster mixtures, but at the same time does not lower the quality of work.

Low cost plaster

In the construction of dwellings, gypsum mixtures have been used for many centuries. Ancient civilizations left us many architectural monuments, which widely used Construction Materials based on gypsum binders.

The use of compositions based on cement and gypsum is due to the mass of positive qualities that are characteristic of this particular group of binders. They practically do not precipitate during hardening, quickly gain strength when solidified, gypsum materials have impeccable sound-proofing and heat-resistant qualities, good fire resistance, and, most importantly, this is an environmentally friendly composition.

Low cost plaster

The use of mixtures based on gypsum and concrete for Russia is especially important in the construction and decoration of buildings and structures because: the lion's share of all the planet's reserves natural gypsum concentrated on Russian territory; the price of manufacturing a gypsum binder is very low (5 times) compared to the price of cement manufacturing; energy costs in the manufacture of 1 ton of gypsum are 3-6 times lower than in the production of a ton of cement.

Why Should You Use Supplements?

Despite the age-old experience of application and the abundance of positive qualities possessed by dry mixes of concrete or gypsum, these finishing materials are used in Russia only for plasters and putties on premises. The reason for this was low water resistance and low strength characteristics, since gypsum dissolves quite well in water, and when hardened, it has a high porosity. But, the solution to these problems was found. To eliminate such shortcomings, additives are used that, when interacting with gypsum, form compounds with lower solubility.

Modifiers

One of the ways to solve problems with the strength and water resistance of concrete and mortars based on gypsum concrete binders is the admixture of a special kind of impurities - modifiers.

Modifiers are a carefully selected combination of organic and mineral components, which are first subjected to special processing and optimized in composition. With the help of these dry modifiers, formations become more water resistant, a denser structure is formed. Thanks to such modifiers, the mixtures not only increased their compliance sanitary requirements, but also significantly improved moisture resistance, increased the speed of curing materials.

Quality improvement

The combination of these properties provides the following benefits:

increases the energy efficiency of buildings, due to a wide range strength characteristics, water resistance and frost resistance;
use materials based on which modified gypsum can be used not only as finishing materials in living quarters, in buildings for various purposes and number of storeys, in enclosing, load-bearing structures;
no need to use heavy construction equipment;
construction time is reduced several times, and the initial cost of construction is significantly reduced.

Application

To date, dry modified mixtures based on gypsum and cement are the most in demand compared to a number of other finishing materials. Dry modified mixtures are used in leveling walls, ceilings, flooring, in tiling, masonry work, and are also used not only for puttying and plastering, but also as tile adhesive, self-leveling floors, etc.

Thus, if we take into account the many shortcomings in the cement industry, and these are inflated prices for Portland cement, and the shortage of its supplies, then the use of mixtures based on gypsum and concrete with the addition of modifiers is the best choice in the range of finishing materials.

Good plaster lasts for decades. Now gypsum mixtures have replaced cement finishing coatings. But not all plasterers refuse the usual materials. Let's look at the strengths and weak sides gypsum and cement mixtures and figure out which plaster is better.

Features of cement-based plaster mixture

The word "plaster" comes from Italian term stuccatura, which denoted the finishing materials familiar to the Romans (lime, alabaster, gypsum). Under modern plaster refers to a hardened mortar intended for leveling walls. It is unambiguous to say which solution is better and which is worse. The composition of the optimal coating depends on many factors.

Plaster solutions have been used for thousands of years to decorate houses, apartments, building facades. The demanded finishing material has evolved along with humanity. In recent decades, when building and repairing houses, builders have mainly used cement coatings.

The mixture consists of cement (main component), sand (filler), plasticizers. As the latter, limestone, gypsum, or combinations thereof are used. Solutions are distinguished by the proportions of the components and depending on the surfaces to be finished. Cement-based coatings cover the walls outside, inside buildings. Moreover, in the latter case, the premises may be unheated and with high humidity.

To strengths cement finishing mortars include:

universality;
plasticity lasts for several hours - you can immediately prepare a large volume, spending it as needed;
strength of the finishing layer;
affordable price.

However, cement plaster is far from ideal. Masters note the following shortcomings:

the mixture does not fit well on the concrete base:
the layer dries for about 14 days, which reduces the pace of finishing work;
high humidity when working with the mixture - for the crystallization of cement particles, the surface to be trimmed must be sprayed with water;
the main component cement gives the finished surface an unsightly gray color;
at the final stage, finishing puttying is mandatory;
when working, a suspension of sand, cement, which enters the respiratory tract, rises into the air.

The main problem when working with cement coatings is a cracked finishing layer. In addition, as it dries, the composition will shrink, which will lead to irregularities. By the way, for this reason, it is not used for drying rooms. optional equipment(heaters, hair dryers, heat guns).

Thus, the cement finishing mortar is suitable for walls in technical rooms, facade works, in apartments with draft and.

Advantages and disadvantages of gypsum coatings

Despite all the advantages of cement mortar, with interior decoration gypsum plaster confidently competes with him. As the name suggests, the main component of the mixture is gypsum powder, made from a natural mineral. During the production process, after a long heat treatment, this powder is crushed. As a result, the finer the fraction (grain size), the better the treated surface.

In addition to gypsum, the composition of the solution includes natural or synthetic fillers, polymer additives. For leveling walls, the shape and size of the grains are of no small importance. In addition, fillers reduce the cost of the mixture and increase the strength of the finishing layer. And the polymer ingredients increase the adhesion of the solution, make it more elastic.

Based on the technical characteristics of the finishing coating, its advantages can be distinguished:

High adhesion - the solution falls on any base;
Leveling ability - the surface finished with gypsum coating is immediately ready for painting, whitewashing, wallpapering;
The consumption of this mixture is lower than that of cement. True, for this you need to follow the rules and technology of work;
Solid thickness of the finishing layer - sometimes it reaches 6 cm;
It is easy to work with the mixture - it fits well on the surface, leveled, smoothed;
The surface treated with such plaster acquires additional sound and heat insulation qualities.

Despite all their positive traits, gypsum coating is not used everywhere. There are reasons for this:

Price. Gypsum mixture costs 1.5–2 times more than cement;
Strength. The surface plastered with gypsum coating does not withstand mechanical damage;
The solution quickly seizes, therefore, in order to avoid overspending, it will have to be prepared in small batches;
The need to use additional materials. For example, when processing a concrete surface, it is necessary to use primer solutions, and plastering metal surfaces without a waterproofing layer is unacceptable. In addition, for this decorative coating tiling is not recommended. On contact adhesive composition with the finishing material, ettringite is formed - a mineral that destroys gypsum.

The main disadvantage of such a mixture is the undesirability of using it for surface treatment outside the house.

There are three types of gypsum finishing coatings. The first is a fine-grained solution, it includes carefully ground sand. Such material is recommended to be applied in layers of 0.5–0.8 cm thick. For leveling, apply a second layer. The main area of application is the decoration of ceilings.

Medium-grained gypsum mortar is the most popular and, as a result, widespread. It is the main competitor of cement-based mortars. Allowable thickness 5 cm.

Coarse-grained gypsum plaster is used to hide significant surface defects. As a rule, broken slopes are repaired with its help, facades are updated. By the way, in the latter case, the selected mixture must be checked for resistance to water. Sometimes, despite the claims of manufacturers, it is better to play it safe and apply a protective layer.

Work with gypsum and cement plaster - a comparative analysis

The main factor determining which plaster is better and which is worse is the characteristics declared by the manufacturer. But along with them, secondary factors must be taken into account - ease of use, the need to use additional materials.

At first glance, the advantages of gypsum coatings are obvious - they are elastic, stick to any surface, and are easy to set. And the faster the layer hardens, the faster the work moves. But with insufficient skill, the prepared batch of plaster will dry out. It cannot be reused. In other words, the price of a mistake is an additional cost, and the cost of gypsum plaster is not affordable.

Cement plaster mortar dries for at least two hours, which allows you to cover in one go large areas. However, the adhesion of such a composition is lower and in some cases (ceiling, corners) the surface will have to be reinforced with a plaster mesh. On the one hand, this entails additional labor costs, on the other hand, the strength of such plaster is many times higher.

As you can see, the answer to the question of which plaster to choose will be ambiguous. For outdoor work the best option becomes cement plaster. But gypsum mortar is a great option for working inside the apartment (with the exception of the kitchen, bathroom,). In rooms with high humidity, you will have to cover the finished surface with varnish.

For leveling and finishing the walls, cement or gypsum plasters are most in demand. Both types of material have their advantages and disadvantages, which must be taken into account before starting finishing work.

In this article, we will consider the features of materials and tell you when it is better to use a gypsum-based mortar, and when you can not do without a cement-sand mixture.

What to look for when planning a finish:

basis for plastering;
indoor humidity;
air temperature;
deadlines for work;
finishing experience;
the cost of materials;
requirements for appearance finished surface.

All plasters according to their purpose are divided into two groups:

Ordinary - for leveling surfaces that have defects of various nature and size, significant deviations from the plane.
Decorative - for finishing the facade or internal walls, ceilings.

Below we will consider the features of conventional leveling compounds.

Properties of gypsum and cement plaster

The characteristics of cement-sand and gypsum plasters are very different. This is primarily due to the knitting base. Application conditions will be similar - at an air temperature indoors or outdoors from +5 to +25 C. Also, the time for complete drying of the solutions is close in value (indoors at an air humidity of no more than 70%).

The table below shows how these types of plasters differ.

Comparison of advantages and disadvantages

Advantages of cement plaster:

the solution can be prepared independently;
not afraid of moisture, does not absorb water, steam from the air, does not change properties when wet;
resistant to temperature extremes;
high adhesion (reliability of adhesion to surfaces), including natural, artificial stone, concrete, brick, cinder blocks;
strength is the highest of all types of plasters, suitability for finishing places with increased operational load;
the price is the lowest among all plasters;
universality - suitability for any surfaces, including in rooms with adverse conditions.

When choosing a mixture for outdoor work, it is necessary to pay attention to frost resistance. It is usually expressed in terms of the number of freeze-thaw cycles.

Advantages of gypsum plaster:

plastic;
gains strength faster than cement, even when applied with the thickest layer - no more than 1 week;
easy to apply, just to achieve perfect evenness, no experience in finishing work is required;
has no shrinkage;
the color is white, does not show through under the wallpaper or paint;
surface is smoother experienced craftsmen withdraw finishing layer to the level of putty;
it is possible to produce three-dimensional patterns and decorative relief;
light, there is no need to strengthen the foundation and walls;
does not need reinforcement (if the layer is up to 50 mm);
vapor permeability - walls plastered with gypsum mortar "breathe";
higher sound and heat insulation properties;
less material consumption;
faster repair times;

Let's continue the comparison of finishing materials and consider their weaknesses.

Disadvantages of cement-sand plaster mortars:

poor adhesion to wood, paint, ceramics; to increase adhesion with these materials, an abrasive primer, notches or reinforcing mesh are required, but these measures do not always give the desired strength;
take a long time to gain final strength - up to 4 weeks;
the application process is relatively complex, the solution under its weight is prone to sagging; experience with such material is necessary, otherwise it will not be possible to achieve a perfectly flat surface;
the finished surface is porous, requires grouting, grinding, an additional finishing layer from another material (this does not apply to decorative plasters);
an accurate calculation of the load on the wall and foundation is necessary, since cement plaster has a high density and significantly weights the walls; it is also undesirable for finishing ceilings;
shrinkage, possibly cracking.

Most of these disadvantages can be corrected by adding modifying additives - plasticizers to the composition.

The addition of lime also improves the properties of the mortar. Read more about cement-lime plaster and its properties in our article.

The appearance of cracks is prevented by applying three layers or puttying the plastered surface. If the cement mixture is used to decorate walls and ceilings for painting or wallpapering, then puttying is required.

Disadvantages of gypsum plasters:

they are afraid of high humidity, upon contact with water they swell and fall off;
low strength;
relatively high cost;
mainly ready-made gypsum mixtures are used; experience is required for self-selection of additives to gypsum and their proportions;
it is possible to prepare the solution only in small portions due to the rapid setting, adding water to the frozen mixture will not restore desired properties plaster, the coating will turn out to be fragile.

Where applicable

Cement plaster is used for:

internal or external work in any premises, even in unheated and damp ones, including basements, utility blocks, garages, porches, on balconies, loggias;
finishing facades, plinths, fences, especially those subjected to aggressive mechanical stress;
filling joints when laying walls from foam or gas blocks;
processing of concrete structures, in order to increase the heat-insulating properties;
restorations subject to compatibility with the previous material;
surface finishes exposed to temperature changes;
decoration of walls or ceilings where frequent repairs are impossible.

Gypsum plaster is used for:

leveling, finishing interior walls in rooms with normal humidity;
ceiling decoration;
alignment of walls with large differences, application in several layers is permissible;
surface finishes for which cement is unsuitable - wooden, painted, ceramic;
preparation of walls and ceilings for painting or wallpapering.

Important! For facade finishing gypsum mortars not suitable due to low moisture resistance. Not recommended without additional waterproofing for bathrooms, showers, kitchens.

Gypsum can be protected from moisture by applying acrylic primer. And if direct contact with water is possible, then the walls are covered with waterproofing mastic or tiled.

Combination of gypsum and cement

Can gypsum plaster or putty be applied over cement plaster? Yes, this is common practice. When finishing, the walls are often removed with a cement-based composition, and a smooth finish layer with Rotband is placed on top.

Important conditions: you need to wait until the base dries, then be sure to apply a primer between different layers.

But the application of cement plaster over plaster wall- bad idea. Plaster simply will not withstand its weight, and the entire finish will crumble.

It is worth noting that cement-gypsum compositions are on sale., combining the advantages of both types, for example, Prospectors MIXTER / MIXTER. According to the manufacturer, this gypsum-cement plaster is designed to interior spaces with normal and high humidity. This is a moisture-resistant vapor-permeable material, plastic and easy to apply.

Technical characteristics with this mixing turned out to be average between gypsum and cement plaster:

Consumption with a layer of 10 mm - 10-11 kg / m2
Water consumption - 0.36-0.42 l / kg
Setting time - 40 min
Adhesion to the base - 0.5 MPa
Layer thickness - up to 60 mm! without the use of plaster mesh
The price is 320 r per bag of 30 kg.

In addition to the main components, this mixture includes light filler and high-quality modifying additives.

Is it possible to mix cement and gypsum plaster on my own to get a plastic, durable and moisture resistant solution? No, that won't work. Gypsum and cement have different time drying, and if they are mixed by eye and without the addition of modifiers, then the plaster layer on the wall will become covered with cracks. It is better not to experiment with such works, so as not to waste time and money.

Let's summarize which one is better.

When choosing one or another type of finish, consider in which room the work will take place. Materials according to their characteristics must be suitable for the surface to be plastered.
Pay attention to specifications indicated on the packaging.
If desired, you can increase the plasticity of the cement or moisture resistance of the gypsum plaster mixture.
Cement mortars are best chosen for the facade and wet rooms. But they require plastering skills. With large volumes of work, it is easier if experienced craftsmen do the finishing.
Gypsum plasters are easier to apply. Their main task is finishing inside the building.
The cost and planned timing of repairs will also affect which plaster to choose.

As you can see, the choice of plaster depends on specific goals. Choosing one type of plastering or using both is decided in each case individually.

We hope this review was helpful to you. You can leave your comments and feedback in the comments below.

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