Gypsum mix: types and applications in construction

Regardless of the choice of materials for finishing indoors, they all imply application to smooth walls. The easiest way to deal with coating imperfections is to use gypsum plaster. It is about its composition and performance characteristics, the subtleties of selection and application that will be discussed in this article.

Gypsum mixture is a dry composition for dilution with water. The main component of the mixture is calcium sulfate hydrate, known as stucco. It is obtained in the process of firing gypsum stone and its subsequent grinding to a state of fine chips (in a similar way - by crushing marble, a composition for the manufacture of artificial stone is obtained).

No shrinkage guarantees a smooth, high-quality surface without cracks, and high adhesion rates make it possible to abandon the use of a reinforcing mesh. It may be required only in newly built buildings, the structure of which shrinks. At the same time, the thickness of the gypsum plaster layer can be quite impressive - up to 5 cm.

But even with such a layer thickness, the weight of the coating is small, so it does not put excessive stress on the supporting structures, and therefore does not require strengthening the base.

Plaster-finished walls retain heat and sound better than concrete walls.

Finally, the surface to be treated is aesthetically pleasing, even, without grainy inclusions.

Some talk about the higher cost of a gypsum-based product compared to concrete-cement counterparts. However, this cannot be considered a minus, since 1 sq. m is consumed up to 10 kg of gypsum mixture and up to 16 kg - cement-sand. In other words, the higher price is offset by the lower specific gravity of the mixture and, accordingly, more economical consumption.

A noticeable disadvantage in some cases can be considered a more rapid setting of the gypsum. This fact must be taken into account when working - immediately smooth the applied plaster, do not dilute it in too large volumes.

In addition, the composition includes components such as:

• perlite, foam glass, vermiculite - reduce the heat transfer of the material, and at the same time its weight;
• lime, whitewash or metal salts, the task of which is to ensure the whiteness of the mixture;
• additives with the help of which the speed of setting and drying of the coating is regulated;
• strength-enhancing components.

The product is completely natural, which means it is environmentally friendly. In addition, the gypsum coating is hygroscopic, that is, it picks up and removes excess moisture from the room, which contributes to an optimal microclimate.

Features of the composition and properties of the product are regulated by GOST 31377-2008, according to which the compressive strength of the material is 2.5 Pa (dry). It has high vapor permeability and thermal conductivity, does not shrink.

The advantages and disadvantages of the product are due to the characteristics of the composition. So, due to its high plasticity, the material is characterized by ease of application. This process is significantly easier than a similar procedure when using other types of plaster.

There are the following types of gypsum-based compositions:

• plaster - designed for rough leveling of walls, coarse-grained;
• putty - light putty for interior work - for finishing walls leveling;
• assembly (dry) mixture - used for the installation of internal partitions made of gypsum boards, leveling of gypsum plasterboards and slabs;
• gypsum polymer - an assembly frost-resistant mixture with increased strength characteristics due to the presence of polymers in the composition;
• trowel mixture "perel" - composition for filling joints and voids;
• self-leveling mixtures for the floor - cement-gypsum mixture for the floor, its leveling.

For the convenience of storage, transportation and use, the dry mixture is packed in strong paper bags with a polyethylene inner layer - the so-called kraft bags. Their weight may vary from manufacturer to manufacturer. Bags of 15 and 30 kg are considered universal, they are most often purchased. However, there are also "intermediate" options - bags of 5, 20 and 25 kg.

The shelf life of the mixture in an unpacked bag is 6 months. After that, even while maintaining the tightness of the package, the gypsum composition absorbs water and loses its performance characteristics. Store the product in a dry place without damaging the original packaging.

In addition to the mixture, a construction mixer is required for work, with which the solution is mixed. Its use allows you to quickly get a homogeneous, lump-free mixture of the desired consistency. Correct mixing of the mortar is one of the components of the ease of application of the mixture and the quality of the coating.

A spatula is required to apply the solution, and a metal or plastic float is required for grouting and glossing the surface. If thin wallpaper is supposed to be pasted over the plastered surfaces, then you need to go over it with a trowel. It has a metal or rubber base.

When working with textured or embossed plasters, rubber rollers are also used, on the surface of which a pattern is applied. Improvised means - a broom, crumpled paper, cloth, brushes, etc. - also allow you to create an interesting texture.

The mixture is intended for interior decoration. The most common types of coverings are walls and ceilings. The main purpose of the material is to level surfaces, eliminate small defects and differences in surface heights.

The mixture is intended for use in rooms with normal humidity, it is not used for external cladding of facades. However, with additional priming, the composition is suitable for application in the bathroom and in the kitchen. For more humid rooms, it is better to choose a hydrophobic coating.

In general, the material is versatile, as it fits perfectly on the following surfaces:

• cement plaster, concrete walls (however, they are pre-treated with concrete contact);
• clay walls;
• brickwork;
• on cellular concrete blocks (foam and aerated concrete), expanded clay concrete;
• old gypsum plaster, subject to the requirements for its high strength.

Gypsum mortar can be applied by machine or by hand. When leveling the walls in an apartment, they usually resort to manual application.

The layer thickness is 3-5 cm, the next layer can be applied only after the previous one has dried. The alignment of the coating is carried out according to the beacons, that is, the thickness of the gypsum layer is equal to the height of the beacons. Grouting allows smoothing surfaces and hiding transitions between layers.

After drying, the plastered surfaces are subject to application of a primer, which will strengthen the layer and eliminate its shedding. If the plastered walls are to be painted or wallpapered, they must be covered with a layer of putty. During the drying of the layer, drafts in the room, exposure to direct sunlight are unacceptable.

If necessary, the gypsum mixture can be prepared with your own hands, especially since the recipe is quite simple. The main components are stucco and water.However, if you use only them, the mixture will quickly harden, making it impossible to work with it.

The introduction of plasticizers allows the reaction between the components to be slowed down. The latter can be lime, PVA glue diluted in half with water, citric or tartaric acids or special liquids. They can be found in hardware stores. In addition to increasing the setting time of the mass, their use allows you to avoid cracking of the plastered surface.

There are several recipes for preparing a gypsum mixture, while in all proportions of the main components are identical. Usually, for 1.5 kg of gypsum (gypsum-lime powder), 1 liter of water is taken, after which a plasticizer is added (5-10% of the total volume).

It is possible to make waterproof plaster, or rather, to give it moisture-resistant characteristics, by applying a deep penetration acrylic primer on top of it. If the plaster is used under a tile, then its moisture resistance can be ensured with the help of a concrete contact.

Knauf "Rotband", "Prospectors", "Volma Lay" mixtures are popular among domestic consumers. In general, the formulations are similar in quality and performance, only some of them cannot be used in rooms with high humidity.

Knauf universal mixes have won the trust of buyers from a German brand with more than half a century of history. The Rotband product is supplied in 5, 10, 25 and 30 kg bags and is a dry mix.

Other mixtures of this manufacturer ("HP Start", "Goldband"), according to user reviews, are quite dense, which complicates the process of working with them.

The demand for the product is due to its versatility: it is suitable for concrete, expanded polystyrene, brick surfaces. Moreover, it can be used in the kitchen and bathroom. The maximum permissible layer thickness for the ceiling is 1.5 cm, for walls and other coatings - 5 cm; minimum - about, 5 cm. Consumption of the composition is average, not too large - about 8.5 kg / m2, provided that it is applied in 1 layer (2 times less than when using sand compositions).

The color of the mixture can be either snow-white or grayish, pinkish. The shade of the product does not affect its performance in any way. The composition also contains additives responsible for improved adhesion. Thanks to this, the mixture demonstrates good adhesion even on the ceiling with a layer thickness of up to 1.5 cm.

Special compounds of the composition help to retain moisture in the coating, so that during the drying process, even at high temperatures, the material does not crack.

When buying a mixture, make sure that the shelf life of the composition is no more than 6 months. Due to its high hygroscopicity, it absorbs moisture from the environment. After six months of storage, the material saturated with moisture loses its technical properties, crumples, which complicates installation. It is important that the bag is hermetically sealed.

Finishing gypsum plaster can be coated with interior paint. The surface can be perfectly flat or textured. In this case, the relief is applied over wet plaster. Depending on the materials used, a tap or other texture is obtained.

If you use special application techniques and special tinting, you can get surfaces that imitate natural materials - wood, concrete, brickwork.

The plastered and painted surface looks interesting, reminiscent of textiles - velvet, leather, silk.

Plaster mix is ​​widely used in arts and crafts. For example, the decor of cans and bottles allows you to turn them into stylish interior accessories.

For information on how to properly prepare a gypsum plaster mixture, see the next video.