Gypsum mixtures: composition, top of the best, instructions for use and reviews. Gypsum-based dry building mixes The procedure for applying gypsum plaster

Site arrangement 29.08.2019

Site arrangement

Dry mortar is a multi-component dry powder, which, when diluted with water, turns into a plastic solution for the desired purpose. Gypsum-based mixtures are lightweight and easy-to-work compositions. The disadvantages include only the possibility of use only inside dry rooms.

Materials based on gypsum binders are characterized by high heat and sound insulation properties, fire and fire safety, lightweight, can be used as decorative elements for architectural solutions interior decoration premises. Usage gypsum materials for interior decoration provides a favorable indoor climate due to the ability of the material to "breathe" - it is easy to absorb moisture and give it away. AT last years materials of a new generation based on gypsum binders have been developed: composite, modified, with reduced water demand and high performance properties.

The main components of gypsum dry mixes are: gypsum binders, fillers, functional additives. Used as a binder in gypsum mixtures building plaster based on b- or a-calcium sulfate hemihydrate. Less often they are used in a mixture with anhydrite (especially for plastering) to ensure the necessary setting time. In the compositions of self-levelling mixtures, high-strength gypsum (a-hemihydrate) and anhydrite are used. The use of these types of gypsum binders in flooring compositions is explained by the requirements for such mixtures and hardened mortars - the necessary vitality and high early strength, providing a short time walking.

Gypsum is a quick-setting and water-absorbing compound. Polymers are introduced into gypsum-based mixtures to reduce water absorption and increase adhesion, as well as inhibitors that slow down the gypsum hardening reaction. Inhibitors include, in particular, food or technical citric acid. If, when mixed with water for 1 kg of gypsum, add 10-20 grams citric acid, the gypsum mass will slow down its hardening up to 30-40 minutes.

The filler is introduced to prevent cracking during operation, improve manufacturability during application. Used as fillers in gypsum mixtures quartz sand, as well as limestone flour, dolomite flour, chalk, ash. Perlite is used in the compositions of light plasters. Functional additives slow down the setting of the gypsum mixture, increase water retention, mobility, plasticity, adhesion strength, create a special porous structure, and reduce the risk of cracking. Setting retarders provide an increase in the survivability of the mortar gypsum mixture. It is known that gypsum binders set quickly, and the solution to the problem of increasing survivability lies in the correct choice of special additives - setting retarders. Water-retaining additives are introduced into gypsum mixtures to increase water retention, adhesion to the base, improve mixing, and impart viscosity and plasticity to the mortar mixture. Dispersants (plasticizers) - additives that are absorbed on the surface of the particles of the mortar mixture, reducing the formation of lumps during its preparation. Pore formers are additives used in plaster mixtures to create a special pore structure of the hardened material.

Gypsum mixes are divided into gypsum putties, gypsum plasters, grout mixes, gypsum-based mounting adhesives, and gypsum floor mixes.

Gypsum putties consist of a gypsum binder (we will call it gypsum, although a mixture of alpha gypsum and anhydride is used in the production), quartz or lime filler, a cellulose thickener and a redispersible polymer. Gypsum putties are applied with a layer of 1 mm to 1 cm. Gypsum putties are distinguished by high plasticity and whiteness. Used for plastering walls and ceilings inside dry rooms, with an improved and high-quality finish in the final application. Gypsum-based compositions are especially common today.

When working with gypsum mixtures, you need to know that gypsum is calcium sulfate. When painting a surface leveled with such a mixture, it is necessary to use acid-resistant paints. Do not forget about safety precautions: gypsum, even in a small wound, causes discomfort.

Gypsum plasters- dry mixes, which have gained particular popularity among builders. Mixtures are light, easy to use, do not shrink (unlike lime-cement-sand putties), harden quickly and have high performance - from 30 minutes to 1 hour. Dry plaster mixtures based on gypsum are designed for plastering walls and ceilings with different surface indoors with normal and high humidity(kitchens and bathrooms).

Simple gypsum plaster can be prepared independently. The composition (10 kg of gypsum, 1 kg of slaked lime, 50 g of citric acid) is mixed with water and mixed until the consistency of thick sour cream.

With the finished mixture, you can close up the strobes, level the walls or ceiling. Industrial plasters also contain fractionated sand, a cellulose thickener and a redispersible polymer. To give the plaster lightness and volume, light weightless sands are added to the compositions - expanded perlite or vermiculite. The average consumption of such plaster is 7 kg / sq.m when applied with a layer of 1 cm.

Gypsum-based mounting adhesives. Of particular interest are dry gypsum mixes for installation work, which are used for gluing sheet and tile materials(drywall, mineral insulation, foam sheets). The composition is similar to the composition of tile adhesive, only gypsum, not cement, is used as the main component.

Gypsum mixes for a floor. This group includes self-leveling (self-leveling) compositions for pouring floors in various layers. Dry mixes for self-leveling floors have a more complex composition and include such functional additives as superplasticizers, hardening accelerators, defoamers. Gypsum-based compounds are mainly used for indoor screeds.

The main components of gypsum dry mixes are: gypsum binders, fillers, functional additives.

As a binder in gypsum mixtures, building gypsum based on calcium sulfate hemihydrate is used. Less often they are used in a mixture with anhydrite (especially for plastering) to ensure the necessary setting time. High-strength (experts say “high-quality”) gypsum and anhydrite are used in the compositions of self-leveling mixtures. The use of these types of gypsum binders in flooring compositions is explained by the special requirements for the strength of such solutions.

The filler is introduced to reduce the cost of the product, but most importantly - to prevent cracking during operation. In addition, its use improves the manufacturability during application. As aggregates in gypsum mixtures, quartz sand is used, as well as limestone flour, dolomite flour, chalk, and ash. Perlite is used in the compositions of light plasters - for example, in mixtures such as HYPER PLAST (the name of this mixture comes from a combination of the words Gypsum and PERLITE). In certain types of putty mixtures, the use of mica is recommended. The dispersion of aggregates is determined by the type of gypsum mixture: quartz sand and limestone sand are used with a dispersion of up to 0.8-1.0 mm. When choosing fillers Special attention given to the granulometric composition: there should be approximately the same ratio of aggregate fractions.

Hydrated lime Ca(OH)2 is added to gypsum mixtures to improve plastic properties, reduce shrinkage and slow setting.

Functional additives slow down the setting speed of the gypsum mixture, increase its water retention, mobility, plasticity, adhesion strength, and reduce the risk of cracking.

Setting retarders are important functional additives that provide an increase in the survivability of the gypsum mortar mixture. It is known that gypsum binders set quickly, and the solution to the problem of increasing survivability lies in the correct choice of special additives - setting retarders.

Cellulose fibers are introduced into the composition of gypsum mixtures to reduce cracking and shrinkage.

These are the lightest in weight and easy-to-work formulations. Their only drawback is the possibility of use only inside dry rooms.

Gypsum is known to be a fast-setting and hydrophilic (water-absorbing) compound. The same polymers are introduced into gypsum-based mixtures in order to reduce water absorption and increase adhesion (gluing strength), as well as inhibitors - substances that slow down the gypsum hardening reaction. The simplest example of an inhibitor is food or technical citric acid. If, when mixed with water for 1 kg of gypsum, you add 10-20 grams of citric acid, then the gypsum mass will slow down its hardening to 30-40 minutes.

Gypsum mixtures are divided into:

Gypsum putties

They consist of a gypsum binder (hereinafter we will call it gypsum, although a mixture of alpha gypsum and anhydride is used in the production), quartz or limestone filler, cellulose thickener and a redispersible polymer. Gypsum putties can be applied in layers from 1 mm to 1 cm.

Attention! Gypsum is calcium sulfate - CaSO4. When painting a surface leveled with such a mixture, it is necessary to use acid-resistant paints. And, accordingly, observe safety precautions: gypsum, even in a small wound, causes very unpleasant sensations.

Gypsum plasters

Dry mixes that have earned the highest recognition from professional builders. They are light, easy to use, do not shrink (unlike lime-sand-cement putties), quickly harden on the surface and have a fairly high performance - from 30 minutes to 1 hour.

You can make the simplest gypsum plaster in your kitchen: we take 10 kg of gypsum, 1 kg of slaked lime, 50 grams of citric acid, we shut it all with water and mix until the consistency of thick sour cream is obtained.

With the finished mixture, you can close up the strobes, level the wall or ceiling. Although industrially prepared plasters also contain fractionated sand, a cellulose thickener and a redispersible polymer. In some compositions, to give the plaster volume and lightness, expanded perlite or vermiculite is added - light, weightless sands. The average consumption of such a plaster is 7 kg / m2 with an application layer of 1 cm.

Gypsum-based mounting adhesives

If we want to glue a sheet of drywall to the wall, mineral insulation, foam sheet, gypsum-based mounting adhesive is best for us. The composition is similar to the composition of tile adhesive, with the exception of the main component: instead of cement, gypsum.

Gypsum floor mixes

Self-leveling (self-leveling) compositions for pouring floors in various layers. The composition and principle of action are discussed in the first part of the article (see also the article Leveling the floor).

Putties based on a polymer binder

They differ from the above types of dry mixes in that they do not contain either cement or gypsum. These are fillers, almost 100% consisting of aggregate - fine limestone or marble flour, cellulose thickener and redispersible polymer.

Putties of this type are very convenient in application and subsequent processing (sanding), suitable for subsequent painting or wallpapering. In diluted form, they have a working capacity of up to 24 hours. But these putties are not intended for leveling surfaces for laying tiles. Putties based on a polymer binder are used only inside dry rooms as a finishing layer for leveling the surface and are not used without further coating.

One of critical issues building materials industry is the development domestic production effective building materials based on harmonious and balanced activities in relation to environment, saving material and fuel and energy resources, maximizing the use of local and technogenic raw materials.

In this aspect, promising Construction Materials and products based on gypsum binders (GV). Gypsum binders and materials based on them have a number of valuable qualities. The production of gypsum binders is non-toxic, characterized by low specific fuel and energy consumption (approximately 4-5 times less compared to cement production). Gypsum materials have good heat and sound insulation properties, fire and fire safety, relatively low density, decorative effect.

In addition, the use of gypsum materials for interior decoration provides a favorable indoor climate due to the ability of the material to "breathe", easily absorb and release moisture. Research on the development of waterproof gypsum binders has expanded the areas of their possible application. Binders of a new generation based on gypsum binders, characterized by reduced water demand and high performance properties, have been developed.

In spite of undoubted advantages gypsum materials and products before materials based on other binders, the scale of their use in Russia is currently significantly inferior to products based on cement.

The range of gypsum binders produced in the country for construction works limited to building gypsum produced in accordance with GOST 1 25-79 with a strength range of 3 to 7 MPa.

Anhydrite binder, which is very promising due to the low cost of raw materials and low investment in processing, has not yet found sufficient distribution. Such a binder has the same positive properties as other gypsum binders, and even surpasses it in final strength. It can be used for the same purposes as gypsum binder, including for the production of dry building mixes.

Building mixes made on the basis of gypsum or anhydrite binders are called dry gypsum mixes (SGS).

A distinctive feature of mortars based on gypsum dry mixes, in comparison with cement mortars a similar purpose is the increased yield per unit mass of the dry mixture. The use of gypsum dry mixes for finishing provides a reduction in labor costs by more than 2 times, and the consumption of the mixture is almost 2 times lower than the cement mixture for the same area of processing.

SGS are homogeneous bulk materials optimal composition, consisting of carefully dosed and mixed dry components - gypsum binders, fractionated aggregates (fillers), pigments and modifying additives for various purposes.

In accordance with the existing classification, the GHS can be divided into the following main types:

plastering (including decorative and protective);
putty;
mounting;
adhesives;
grouting;
floor (leveling for flooring).

Mixtures based on non-water-resistant gypsum binders are used for interior decoration of buildings and structures with dry and normal indoor conditions, and GHS based on waterproof gypsum binders for finishing work in rooms with normal, wet and wet conditions, as well as when finishing facades of buildings in accordance with applicable regulations. regulatory documents SNiP 3.04.01-87, SNiP 2.03.13 - 88, SNiP P -3 - 79*.

Plaster gypsum mixes

Plaster mixtures are mortar mixtures of non-water-resistant gypsum binders of B- or a-modifications, anhydrite or mixtures thereof, coarse-grained aggregate with a fraction of not more than 2.5 mm and special chemical additives for various purposes. Such mixtures are intended for rough leveling of surfaces by single-layer plastering of walls and ceilings with different kind surfaces (concrete, masonry, cellular concrete, other rough and corrugated surfaces).

To the most known species plaster plaster mixes include: ROTHBAND, GOLDBAND, GIPSPUTZ HP 100, MASHI-NENPUTZ MP 75, ACOUSTICPUTZ, TEPLON, SILIN, FARVEST-Gypsum, GYPSUM white, GYPSUM gray, CONSOLIT 500, etc.

Gypsum plaster mixtures and solutions from them should be characterized by the following indicators:

bulk density of the mixture, kg/m3 -700...1100;
water-to-solid ratio (the amount of mixing water required to obtain a given mobility of the solution) -0.5 ... 0.b;
solution processing time, min. -50...100;
hardened mortar density, kg/m3 -800...1100;
compressive strength, MPa - 2.5 ... 7.0;
tensile strength in bending, MPa - 1.5 - 3.0;
adhesion strength with the base (surface to be treated), MPa - 0.4 ... 0.7;
storage period, months - 3...6

The indicators of these properties depend on the scope of the solution and its composition.

Putty gypsum mixes

Putty mixtures are dispersed mixtures of non-water-resistant gypsum binders of B- or a-modifications, anhydrite or waterproof gypsum binders (gypsum-cement-pozzolanic or composite gypsum binders), fine and finely dispersed fillers and targeted chemical additives.

Such mixtures are intended for fine and finishing leveling of the surfaces of walls and ceilings; for the final preparation of concrete and plastered surfaces for painting or wallpapering; for facing and restoration works. They are used for sealing longitudinal and transverse joints between GKL and GVL during interior finishing work, as well as seams during the installation of gypsum tongue-and-groove boards. They have good adhesion to various materials and practically do not shrink. The advantage of gypsum putties is their rapid hardening, which allows further Finishing work after several hours of curing.

The most famous types of gypsum putty mixtures include: UNIFLOT; FUGENFULLER; FUGENFULLER Hydro; FUGENFULLER GW; FUGENFIT; FINISHING; UNIS GSH; GSH Slide; UNICE Bleek; R-16 MONOLITH; R-1 7 MONOLITH; GLIMS-Gypsum; PETRO-MIX SHG; ShGL; ShGS; SHGU; KREPS GKL and others.

Gypsum putty mixtures are characterized by the following properties:

compressive strength, MPa - 4...1 0;
tensile strength in bending, MPa - 2.5 ... 5;
storage period, months - 3...6

Dry gypsum mixes (mounting)

Mounting mixtures are mortar mixtures of non-waterproof gypsum binders of p- and a-modifications or waterproof gypsum binders (gypsum-cement-pozzolanic or composite gypsum binders) with a specially selected complex of chemical additives.

Such mixtures are used in the installation internal partitions from gypsum tongue-and-groove slabs; when facing internal surfaces with plasterboard and gypsum fiber sheets, as well as when arranging floor bases from gypsum fiber boards.

The most famous types of gypsum assembly mixtures include: PERLFIX, ("KNAUF"), GIPSOKONTAKT ("Bolars"), VOLMA installation (JSC GIPS, Volgograd), etc.

The main physical and technical characteristics of some types of gypsum assembly mixtures are as follows:

bulk density, kg/m3 - 800...950;
water-solid ratio - 0.4...0.6;
solution processing time, min. - 60...120;
hardened mortar density, kg/m3 - 1300...1350;
compressive strength, MPa - 4...7.5;
tensile strength in bending, MPa - 1.5...5;
adhesion strength, MPa - 0.3 ... 0.7;
storage period, months – 6

Dry gypsum floor mixes (leveling)

Dry mixes for floor installation are mortar mixes of non-waterproof gypsum binders a-modification, anhydrite, estrich gypsum or waterproof gypsum binders (gypsum-cement-pozzolanic or composite gypsum binders) and a special set of chemical additives to increase the plasticity of the mortar while reducing the water content.

The most well-known types of gypsum mixtures intended for the installation of floor bases include ATLAS SAM 200 mixtures, self-leveling composition Alfa-Pol C, Quick-hardening floor (“Prospectors”), SV-210 floor mixture (Bolars), etc.

As self-levelling compounds known dry mixes for self-leveling floors: Flissestrich FE 80, Flissestrich FE 50, Flissestrich FE 25, which are produced by Knauf enterprises. Hardened solutions from these mixtures have high strength and practically do not shrink.

The main physical and technical characteristics of some types of gypsum leveling mixtures for flooring are as follows:

bulk density, kg/m3 - 600...700;
water-solid ratio - 0.48...0.6;
solution processing time, min. – 60...120;
hardened solution density, kg/m3 - 1100...1800;
compressive strength, MPa - 4...10;
tensile strength in bending, MPa-2.5,.,5;
adhesion strength, MPa - 0.3 ... 0.5;
storage period, months - 3...6

Raw materials

For the manufacture of SGS, the following basic materials and additives are used: gypsum binders grades G4-G7 according to GOST 125-79 (for plaster and putty mixtures in the production of finishing works):

high-strength gypsum grade not lower than I 3 according to GOST 125-79 (for high-strength putties and compositions for installation work, as well as in compositions for self-leveling floor screeds); waterproof gypsum binders according to TU 21 -0284757-1-90 (for dry gypsum mixtures used in rooms with wet and wet operating conditions, as well as for floor mixtures); anhydrite binders (from natural raw materials and industrial waste) according to TU21-0284747-1-90 (for plaster mixtures and leveling mixtures for flooring);
hydrated lime according to GOST 9179-77 (residue on sieve 02 up to 0.2% by weight). Humidity up to 0.5% by weight (in plaster compositions and in compositions of self-leveling mixtures for flooring).

Aggregates and fillers have a great influence on the properties of GHS. The choice of aggregate grain size is determined by the type of gypsum mixture: quartz and limestone sand are used with a fineness of up to 0.8 - 1.0 mm. When selecting aggregates, special attention is paid to the granulometric composition: there should be approximately the same ratio of aggregate fractions.

The GHS uses the following aggregates and fillers:

expanded perlite sand according to GOST 10832-91; residue on a sieve with a mesh size of 1.25 mm - less than 10% by weight. Bulk density - from 70 to 125 kg/m3; used in compositions of heat-insulating or lightweight plaster mixtures;
expanded vermiculite sand according to the current NTD;
quartz sands according to GOST 21 38-91, the residue on sieve No. 05 is less than 10% by weight. Moisture less than 0.5% by weight; used in the composition of plaster mixtures and in the composition of leveling mixtures for flooring;
mineral powder for asphalt concrete mixtures according to GOST 16557-78, the residue on sieve No. 0315 is less than 10% by weight. Humidity is not more than 0.5% by weight; used in the composition of plaster and putty mixtures.>

Chemical additives for gypsum mixtures must meet the requirements of GOST 24211-91. These include the following additives:

Water-retaining based on cellulose ethers (methylcellulose brand MTs-100 (Russia); ethyl hydroxyethyl cellulose, EOEC (Sweden); sodium carboxymethyl cellulose, (CMC), (Russia).
Based on cellulose esters (methylhydroxyethylcellulose, (MHEC), (Germany, USA); methylhydroxypropylcellulose (MHPC), ( South Korea);
Air-entraining anionic surfactants (Russia, Germany); olefin sulfonate (Germany);
Thickening agents based on starch ether (Russia, Germany); based on hectorite clays (Italy);
Plasticizing naphthalene-formaldehyde, for example C-3 (Russia); melamine-formaldehyde (Germany); polycarboxylate (Germany);
redispersion polymer powders: based on vinyl acetate copolymers (Germany, Switzerland, USA, France); based on styrene-butadiene latex (Germany); based on acrylate (Germany);
defoamers - additives, which are hydrocarbons and polyglycols on an inert carrier (amorphous silica).

In the manufacture of CGS, the correct choice of additives that regulate the beginning and end of setting, especially those intended for plastering, is of great importance. In this case, it is necessary to take into account not only the type of gypsum binder, but also the pH environment of the prepared gypsum mortar.

For a neutral environment of a gypsum mortar, citric acid, sodium citrate, polyphosphates, protein hydrolysates, gelatins - CMC (sodium salt of carboxymethyl cellulose), adhesives of animal origin, a mixture of lignosulfonates can be effective setting retarders. However, it should be borne in mind, for example, that retardane, being an active gypsum setting retarder, is very well suited for putty compositions. At the same time for plaster compositions it is not effective enough, because gives a short period between the beginning and the end of setting, which is undesirable in the production of plaster work.

For gypsum mortars with an alkaline environment, tartaric acid, as well as a retarder based on tartaric acid and plastretard, are effective retarders.

For a slightly acidic environment, for example, in plaster mortars based on gypsum binder from phosphogypsum, hydrated lime and sodium tripolyphosphate are used as a retarder.

To achieve the required delay in the setting of the gypsum mortar, it is advisable to use a complex additive. A typical example is pla-stretard - a mixture of citric acid with polyphosphates and gelatin.

To reduce cracking and shrinkage deformations, cellulose fibers are introduced.

Putty, grout mixtures and gypsum adhesives differ from plaster compositions, both in their component composition and in its dispersion. A feature of these compositions is that building gypsum with a particle size of less than 0.1 mm is used as a binder, the filler is limestone, dolomite flour, chalk with a grain size of less than 0.1 mm. In this regard, the number of water-retaining additives increases to 0.5-0.8%, while in plaster compositions - 0.16-0.3%.

Of great importance in SSS, including SGS, are water-retaining additives based on cellulose ethers. Studies have shown that due to the weak intermolecular interaction with water molecules, these polymers have excellent water-holding capacity. Each polymer molecule can hold up to 20,000 water molecules. The energy of this interaction is comparable to the energy of evaporation and capillary diffusion into the substrate, which is an obstacle to the escape of water. In turn, this energy is somewhat less than the diffusion energy of water during cement hydration, which allows it to take this water.

In fact, the water in the solution is replaced by a homogeneous jelly-like solution of methylcellulose, in which particles of cement and aggregate are suspended. The high water-retaining capacity of such a system contributes to the complete hydration of the cement and allows the mortar to gain the required strength even with thin-layer application. After leaving the water, the polymer in the form of the thinnest film remains on the surfaces between the cement stone and the filler, without affecting in any way mechanical characteristics hardened solution. Thus, the addition of a small amount (0.02-0.07%) of water-soluble cellulose ethers to cement-sand mixtures leads to a significant increase in open time and allows the solution to hydrate evenly throughout the volume, and also provides a significant increase in adhesion to the base and improvement surface quality. Similarly, the action of methylcellulose in gypsum mixtures.

Dispersion powders, which, unlike water-soluble cellulose derivatives, do not form solutions when mixed with water, but two-phase systems consisting of polymer particles (based on copolymers of vinyl acetate and ethylene, vinyl chloride, styrene acrylate, etc.) dispersed in water . The addition of these compositions to construction chemicals allows you to actively influence the characteristics of the final material and provides results that are unattainable using only traditional mineral binders. First attempt at modification cement mixtures polymers consisted in adding to the mixing water a dispersion of vinyl acetate, known as PVA glue. In gypsum mortars, this application turned out to be very effective, while in cement mortars (due to increased shrinkage from the use of PVA) they were quickly abandoned. The next step was the use of two-component compositions consisting of a cement-sand mixture prepared at the factory and a polymer dispersion supplied in liquid form, which are mixed on construction site. Two-component solutions are still used, but the aqueous dispersion loses its properties when it freezes, therefore, in the cold season, its transportation and preparation of the working solution cause certain difficulties. The beginning of the production of one-component dry building mixtures dates back to 1953, when the specialists of the Wacker company (Germany) managed to obtain a dry redispersible powder, which, after mixing with water, forms a two-phase system that has the properties of the original polymer dispersion.

Dispersions differ from methylcellulose in their mechanism of action. As water is consumed, it concentrates in the pores of the cement stone and the dispersion is concentrated there, forming “elastic bridges” that work in tension and bending incomparably better than cement. The combination of mineral and polymeric binders makes it possible to manufacture building chemistry products that have not only increased strength properties and improved adhesion (including to such “problematic” substrates as metal, wood, plastic, glazed tiles, etc.), but and controlled rheological (thixotropy, plasticity) and special (hydrophobicity, fluidity) characteristics. For example, leveling mortars for floors contain a combination of special dispersion additives with organic and synthetic plasticizers, the presence of which determines such specific properties of these materials as the ability to spread and the smoothness of the resulting surface. Dispersion modifiers included in the composition adhesive compositions for tile work, improve working conditions, prolong the "life" of the closed solution and increase the thixotropy (the ability to thicken at rest and liquefy when mixed) of the material. They help increase adhesion to complex substrates.

The development of dry mix formulations is a complex and lengthy process that requires the participation of qualified personnel and the obligatory availability of a modern laboratory for research and testing samples of solutions from dry mixes, equipped with modern equipment.

10.02.2009

Gypsum dry mixes

One of the most important problems of the building materials industry is the development of domestic production of efficient building materials based on harmonious and balanced activities in relation to the environment, saving material and fuel and energy resources, and maximizing the use of local and technogenic raw materials.

In this aspect, building materials and products based on gypsum binders (GB) are promising. Gypsum binders and materials based on them have a number of valuable qualities. The production of gypsum binders is non-toxic, characterized by low specific fuel and energy consumption (approximately 4-5 times less compared to cement production). Gypsum materials have good heat and sound insulation properties, fire and fire safety, relatively low density, decorative effect.

Despite the undoubted advantages of gypsum materials and products over materials based on other binders, the scale of their use in Russia is currently significantly inferior to cement-based products.

The range of gypsum binders produced in the country for construction work is limited to building gypsum produced in accordance with GOST 1 25-79 with a strength range of 3 to 7 MPa.

Building mixes made on the basis of gypsum or anhydrite binders are called dry gypsum mixes (SGS).

A distinctive feature of mortars based on gypsum dry mixes, in comparison with cement mortars of a similar purpose, is an increased yield per unit mass of the dry mix. The use of gypsum dry mixes for finishing provides a reduction in labor costs by more than 2 times, and the consumption of the mixture is almost 2 times lower than the cement mixture for the same area of processing.

SGS are homogeneous bulk materials of optimal composition, consisting of carefully dosed and mixed dry components - gypsum binders, fractionated aggregates (fillers), pigments and modifying additives for various purposes.

In accordance with the existing classification, the GHS can be divided into the following main types:

plastering (including decorative and protective);

putty;

mounting;

adhesives;

grouting;

floor (leveling for flooring).

Mixtures based on non-water-resistant gypsum binders are used for interior decoration of buildings and structures with dry and normal indoor conditions, and GHS based on waterproof gypsum binders for finishing work in rooms with normal, wet and wet conditions, as well as when finishing building facades in accordance with current regulatory documents SNiP 3.04.01-87, SNiP 2.03.13 - 88, SNiP P -3 - 79*.

Plaster gypsum mixes

Plaster mixtures are mortar mixtures of non-water-resistant gypsum binders of B- or a-modifications, anhydrite or mixtures thereof, coarse-grained aggregate with a fraction of not more than 2.5 mm and special chemical additives for various purposes. Such mixtures are intended for rough leveling of surfaces by single-layer plastering of walls and ceilings with various types of surfaces (concrete, brickwork, cellular concrete, other rough and corrugated surfaces).

The most famous types of gypsum plaster mixtures include: ROTHBAND, GOLDBAND, GIPSPUTS HP 100, MASHI-NENPUTS MP 75, ACOUSTICPUTS, TEPLON, SILIN, FARVEST-Gypsum, GYPSUM white, GYPSUM gray, CONSOLIT 500, etc.

Gypsum plaster mixtures and solutions from them should be characterized by the following indicators:

bulk density of the mixture, kg/m3 -700...1100;

water-to-solid ratio (the amount of mixing water required to obtain a given mobility of the solution) -0.5 ... 0.b;

solution processing time, min. -50...100;

hardened mortar density, kg/m3 -800...1100;

compressive strength, MPa - 2.5 ... 7.0;

tensile strength in bending, MPa - 1.5 - 3.0;

adhesion strength with the base (surface to be treated), MPa - 0.4 ... 0.7;

storage period, months - 3...6

The indicators of these properties depend on the scope of the solution and its composition.

Putty gypsum mixes

Gypsum putty mixtures are characterized by the following properties:

hardened solution density, kg/m3 - 1100...1800;

compressive strength, MPa - 4...1 0;

tensile strength in bending, MPa - 2.5 ... 5;

storage period, months - 3...6

Dry gypsum mixes (mounting)

Such mixtures are used in the installation of internal partitions from gypsum tongue-and-groove slabs; when facing internal surfaces with plasterboard and gypsum fiber sheets, as well as when arranging floor bases from gypsum fiber boards.

The most famous types of gypsum assembly mixtures include: PERLFIX, ("KNAUF"), GIPSOKONTAKT ("Bolars"), VOLMA installation (JSC GIPS, Volgograd), etc.

The main physical and technical characteristics of some types of gypsum assembly mixtures are as follows:

bulk density, kg / m 3 - 800 ... 950;

water-solid ratio - 0.4...0.6;

solution processing time, min. - 60...120;

hardened mortar density, kg/m3 - 1300...1350;

compressive strength, MPa - 4...7.5;

tensile strength in bending, MPa - 1.5...5;

adhesion strength, MPa - 0.3 ... 0.7;

storage period, months - 6

Dry gypsum floor mixes (leveling)

As self-levelling compounds known dry mixes for self-leveling floors: Flissestrich FE 80, Flissestrich FE 50, Flissestrich FE 25, which are produced by Knauf enterprises. The hardened solutions from these mixtures have high strength and practically do not shrink.

The main physical and technical characteristics of some types of gypsum leveling mixtures for flooring are as follows:

bulk density, kg / m 3 - 600 ... 700;

water-solid ratio - 0.48...0.6;

solution processing time, min. - 60...120;

the density of the hardened solution, kg / m 3 - 1100 ... 1800;

compressive strength, MPa - 4...10;

tensile strength in bending, MPa-2.5,.,5;

adhesion strength, MPa - 0.3 ... 0.5;

storage period, months - 3...6

Raw materials

hydrated lime according to GOST 9179-77 (residue on sieve 02 up to 0.2% by weight). Humidity up to 0.5% by weight (in plaster compositions and in compositions of self-leveling mixtures for flooring).

The GHS uses the following aggregates and fillers:

expanded perlite sand according to GOST 10832-91; residue on a sieve with a mesh size of 1.25 mm - less than 10% by weight. Bulk density - from 70 to 125 kg/m3; used in compositions of heat-insulating or lightweight plaster mixtures;

expanded vermiculite sand according to the current NTD;

quartz sands according to GOST 21 38-91, the residue on sieve No. 05 is less than 10% by weight. Moisture less than 0.5% by weight; used in the composition of plaster mixtures and in the composition of leveling mixtures for flooring;

mineral powder for asphalt concrete mixtures according to GOST 16557-78, the residue on sieve No. 0315 is less than 10% by weight. Humidity is not more than 0.5% by weight; used in the composition of plaster and putty mixtures.

Chemical additives for gypsum mixtures must meet the requirements of GOST 24211-91. These include the following additives:

water-retaining based on cellulose ethers (methylcellulose brand MC-100 (Russia); ethyloxyethylcellulose, EOEC (Sweden); sodium salt of carboxymethylcellulose, (CMC), (Russia).

Based on cellulose esters (methylhydroxyethylcellulose, (MHEC), (Germany, USA); methylhydroxypropylcellulose (MHPC), (South Korea);

air-entraining anionic surfactants (Russia, Germany); olefin sulfonate (Germany);

thickening based on starch ether (Russia, Germany); based on hectorite clays (Italy);

plasticizing naphthalene-formaldehyde, for example C-3 (Russia); melamine-formaldehyde (Germany); polycarboxylate (Germany);

redispersion polymer powders: based on vinyl acetate copolymers (Germany, Switzerland, USA, France); based on styrene-butadiene latex (Germany); based on acrylate (Germany);

defoamers- additives, which are hydrocarbons and polyglycols on an inert carrier (amorphous silica).

For a neutral environment of a gypsum mortar, citric acid, sodium citrate, polyphosphates, protein hydrolysates, gelatins - CMC (sodium salt of carboxymethyl cellulose), adhesives of animal origin, a mixture of lignosulfonates can be effective setting retarders. However, it should be borne in mind, for example, that retardane, being an active gypsum setting retarder, is very well suited for putty compositions. At the same time, for plaster compositions, it is not effective enough, because. gives a short period between the beginning and the end of setting, which is undesirable in the production of plaster work.

For gypsum mortars with an alkaline environment, tartaric acid, as well as a retarder based on tartaric acid and plastretard, are effective retarders.

For a slightly acidic environment, for example, in plaster mortars based on gypsum binder from phosphogypsum, hydrated lime and sodium tripolyphosphate are used as a retarder.

To reduce cracking and shrinkage deformations, cellulose fibers are introduced.

In fact, the water in the solution is replaced by a homogeneous jelly-like solution of methylcellulose, in which particles of cement and aggregate are suspended. The high water-retaining capacity of such a system contributes to the complete hydration of the cement and allows the mortar to gain the required strength even with thin-layer application. After leaving the water, the polymer in the form of the thinnest film remains on the surfaces between the cement stone and the filler, without affecting the mechanical characteristics of the hardened mortar. Thus, the addition of a small amount (0.02-0.07%) of water-soluble cellulose ethers to cement-sand mixtures leads to a significant increase in open time and allows the solution to hydrate evenly throughout the volume, and also provides a significant increase in adhesion to the base and improvement surface quality. Similarly, the action of methylcellulose in gypsum mixtures.

Dispersion powders, which, unlike water-soluble cellulose derivatives, do not form solutions when mixed with water, but two-phase systems consisting of polymer particles (based on copolymers of vinyl acetate and ethylene, vinyl chloride, styrene acrylate, etc.) dispersed in water . The addition of these compositions to construction chemicals allows you to actively influence the characteristics of the final material and provides results that are unattainable using only traditional mineral binders. The first attempts to modify cement mixtures with polymers consisted of adding a vinyl acetate dispersion, known as PVA glue, to the mixing water. In gypsum mortars, this application turned out to be very effective, while in cement mortars (due to increased shrinkage from the use of PVA) they were quickly abandoned. The next step was the use of two-component compositions consisting of a cement-sand mixture prepared at the factory and a polymer dispersion supplied in liquid form, which are mixed at the construction site. Two-component solutions are still used, but the aqueous dispersion loses its properties when it freezes, therefore, in the cold season, its transportation and preparation of the working solution cause certain difficulties. The beginning of the production of one-component dry building mixtures dates back to 1953, when the specialists of the Wacker company (Germany) managed to obtain a dry redispersible powder, which, after mixing with water, forms a two-phase system that has the properties of the original polymer dispersion.

Dispersions differ from methylcellulose in their mechanism of action. As water is consumed, it concentrates in the pores of the cement stone and the dispersion is concentrated there, forming “elastic bridges” that work in tension and bending incomparably better than cement. The combination of mineral and polymeric binders makes it possible to manufacture building chemistry products that have not only increased strength properties and improved adhesion (including to such “problematic” substrates as metal, wood, plastic, glazed tiles, etc.), but and controlled rheological (thixotropy, plasticity) and special (hydrophobicity, fluidity) characteristics. For example, leveling mortars for floors contain a combination of special dispersion additives with organic and synthetic plasticizers, the presence of which determines such specific properties of these materials as the ability to spread and the smoothness of the resulting surface. Dispersion modifiers, which are part of adhesive compositions for tile work, improve working conditions, prolong the “lifetime” of the closed solution and increase the thixotropy (the ability to thicken at rest and liquefy when mixed) of the material. They help increase adhesion to complex substrates.

State Unitary Enterprise "NIIMosstroy" develops the formulation of gypsum dry mixes according to the orders of enterprises, tests all types of dry building mixes, including certification ones. To this end, the laboratories of the institute are equipped with modern instruments and equipment, incl. for testing binders according to European standards. Besides. Certification Center NIIMosstroy certifies products and quality management systems.

Dry gypsum mixes are a fairly popular type of finishing materials and are widely represented on the construction market. Popularity is explained by the ideal ratio of price and quality, ease of preparation and use, as well as the wide availability of formulations.

Peculiarities

Dry gypsum mixtures are presented in the form of homogeneous bulk materials, consisting of gypsum binder, fractionated filler, modification additives and pigments. The role of the binder component is building gypsum, which is based on calcium sulfate hemihydrate.

Anhydrite is added to high-quality gypsum for the manufacture of particularly strong mixtures. These two components are responsible for the working qualities of the composition, providing a quick setting and high strength of the material. The brand of gypsum used for the manufacture of dry mixes is regulated by GOST 125 79, which allows changing the strength range of the component from 3 to 7 MPa.

As a fractionated aggregate, limestone and dolomite flour, ash, chalk or quartz sand are used. These components significantly reduce the cost of the composition and help prevent cracking of the hardened mixture during its operation. In the production of light plaster compositions, perlite is often used, and mica is added to putty products. The particle size of the dispersion components depends on the type of mixture and ranges from 0.1 to 1.0 mm.

Modifying additives are introduced into the composition of the material to improve its performance and ease of use. Thus, the addition of hydrated lime Ca (OH) 2, as well as the use of cellulose fibers, significantly increases the plastic properties and mobility of mixtures, provides good adhesion, and also significantly reduces shrinkage deformations and the risk of cracks.

Setting retarders also play an important role. Their use significantly increases the survivability of the mixture, promotes convenient application and makes it possible to correct the formed layer.

If, despite the presence of additives, gypsum mortar seizes too quickly, add 10 to 20 grams of citric acid per 1 kg of dry mix. This will slow down the setting of the composition by 30 minutes.

Pros and cons

The high consumer demand for dry gypsum mixtures is due to a number of positive properties of these compositions:

A characteristic feature of gypsum mixtures is the high yield of the finished solution per unit mass of the dry product. This allows you to reduce material consumption by more than two times, in comparison, for example, with cement mortars. So, for plastering one square meter of surface, only 9 kg is required. gypsum plaster, while the consumption of cement for finishing the same area will be about 18 kg.
The high plasticity of the mortars makes the process less complicated and time-consuming, in comparison, for example, with cement compositions.
The uniformity and smoothness of the formed layer allows you to immediately start applying a decorative coating.
No shrinkage.
Excellent adhesive properties make it possible to produce plastering work without the use of reinforcing mesh. The exception is the walls of new buildings, in which movements are possible due to shrinkage of the new building.

High sound and heat insulating properties of dry mixes guarantee reliable protection rooms from cold and extraneous noise.
The low weight of gypsum-covered walls noticeably reduces the load on bearing structures building.
The fast speed of primary setting and complete drying can be attributed to both the advantages and disadvantages of gypsum mixtures. The assessment of this quality depends on how professionally plastering or puttying work is performed, as well as on how quickly it is necessary to complete the installation.
Dry mixes are environmentally friendly and non-flammable, which allows them to be used in residential areas and public buildings no limit.
Gypsum materials are well ventilated and quite hygroscopic. This gives them the opportunity to release accumulated moisture and reduces the risk of mold and mildew on the walls.

The disadvantages of dry mixes of gypsum include the impossibility of their use in outdoor work., as well as in rooms with air humidity above 60%. The rapid setting of the composition can also be attributed to the disadvantages. To avoid premature hardening, dilute the mixture in small portions and use setting retarders, for example, a mixture of citric acid with polyphosphates and gelatin. Another disadvantage is the low strength of the gypsum layer, which can be easily scratched or chipped. The price of gypsum mixtures is usually 15-20% higher than the cost of cement-sand compositions.

Kinds

Dry gypsum mixes are available in several versions, and differ in composition, purpose, place of application and cost.

On the modern market a huge selection of plaster, putty, mounting, grouting compounds, as well as self-leveling mixtures and adhesives.

Plaster mixtures are a very common type of dry compositions and are used in finishing interior spaces. Plaster on plaster base very easy to use: the formed layer is not prone to slipping and cracking, the installation process is very simple and anyone can do it. The average output per day can reach 40 square meters surfaces, which is a very good indicator and provides a significant reduction in repair time. Among the minuses of plaster, there is a low resistance to moisture, which does not allow work to be carried out on the street. The disadvantages can be added to the low frost-resistant properties of the material, as well as the rapid setting of the finished solution.
Mounting mixtures are used in the construction of internal partitions, during cladding with GKL or gypsum-fiber boards, as well as for laying the foundation when laying the floor from GVL. The material also does not tolerate well. high humidity and is not recommended for outdoor use.

Putty mixtures are represented by non-water-resistant dispersed compositions and are intended for finishing and leveling the bases, for the preparation of plastered or concrete walls for painting, for cladding and restoration of household items, elimination of butt joints when finishing with GKL and GVL sheets. This light finishing putty has excellent adhesion, does not shrink and dries quickly.
Gypsum-based glue is indispensable if drywall is used during installation, tongue-and-groove slabs and GVL. The material has low waterproof performance, so its scope is also limited to dry and warm rooms. To ensure high adhesion and increase the bonding strength, 12 hours before applying the adhesive, the surface must be thoroughly cleaned of dust and primed. Only in this case, you can count on the reliability of the connection and its durability.

Self-leveling compounds are used as self-leveling floors and are characterized by high strength and smooth surface. The material is easy to prepare and install, does not shrink and dries quickly.
Grout mixtures are represented by finely dispersed compositions and are designed to eliminate minor defects in working bases. The material has good adhesion, high ductility and low cost.

Scope of application

Dry gypsum mixes are widely used in construction and repair. With their help, floors and walls are leveled, tiles are glued, cracks, chips and other base defects are eliminated. Gypsum compounds can be plastered on almost any surface: brickwork and clay walls, concrete bases and cellular foam concrete, gas and expanded clay concrete and an old plastered wall. In addition to repair and construction work, gypsum compositions can also perform a decorative function.

They are actively used in the manufacture artificial stone, for decorating bottles and cans, decorating rooms, creating stucco moldings and bas-reliefs. Mixtures are indispensable in the construction of internal partitions, for the construction of which metal profiles and drywall are used.

With the help of assembly and grout mixtures, it is possible to completely hide the gaps between sheets and achieve a perfectly even and uniform surface.

Manufacturers

Gypsum dry mixes are produced in many countries of the world.

The most famous and recognizable manufacturers are the German concern Knauf and Russian companies"Volma" and "Prospectors". Knauf products account for about a third of the total volume of dry mixes on the domestic market. The company has been known to the Russian consumer since 1993 and produces the entire line of gypsum compounds, including plasters, grouts, masonry mixtures and adhesives. Every year, the company's sales volumes increase by 35%, which indicates the high quality and demand for German products. The production facilities of the company are located in more than 250 countries of the world, the production of mixtures is carried out on high-tech equipment with strict control over the quality of the compositions.

Volma company occupies an honorable second place in the construction market after Knauf, and is engaged in the production of putties, plasters, levelers, tile adhesives, assembly and self-leveling compounds. The company operates in 5 factories and owns three gypsum quarries. "Prospectors" are also well known to the Russian buyer. The company has four branches, 15 production lines, and is considered the largest producer of dry mixes in our country. No less popular are the products of the Gypsopolymer and Perel companies. Enterprises produce the entire line of gypsum mixtures, which are of high quality and low price.