How to choose gypsum plaster for concrete?

Selecting the appropriate gypsum plaster is essential for finishing concrete walls. Gypsum plaster is a common option for both residential and commercial projects because it provides a smooth and long-lasting surface. However, choosing the best kind can be difficult due to the abundance of options on the market. Making an informed decision and getting the best results for your concrete surfaces will be made easier if you are aware of the important factors to take into account.

The kind of gypsum plaster is the first thing to think about. There are multiple types, such as dry powder and pre-mixed versions. Because pre-mixed gypsum plaster is ready to use, it’s convenient and simple to use. Conversely, dry powder forms need to be mixed with water, which can be changed to get the right consistency. Choose according to the particular requirements of your project and your degree of experience; each type has advantages.

The plaster’s setting time is another crucial component. Certain gypsum plasters have a quick set time, which makes them perfect for projects that must be finished quickly. Some set more slowly, giving you more time to make changes and add finishing touches. Choose a plaster that will work with your schedule after taking your project’s pace into account.

Adhesion is yet another important factor. A strong bond between the plaster and the concrete surface is necessary to guarantee durability and avoid future problems like peeling or cracking. Many gypsum plasters are designed specifically to improve adhesion; therefore, seek out products that guarantee a strong bond with concrete.

Finally, think about the outcome you hope to attain. Smooth, polished, textured, and other finishes are all possible with gypsum plaster. Consider the style you want for your area and select a plaster that can achieve that effect. Certain plasters are versatile in that they can be easily troweled or sanded to create different textures.

You can select the ideal gypsum plaster for your concrete surfaces by considering these factors. There is a product out there that will suit your needs, regardless of how important finish, adhesion, ease of use, or setting time are to you. The beauty and usefulness of your space will be enhanced by a high-quality, long-lasting finish that is ensured by careful selection and application.

Purpose

Gypsum plastering is intended for use in decorating low-humidity areas where people are present, such as homes, offices, and commercial real estate. Gypsum compositions, however, can also be utilized in bathrooms and kitchens. Deep irregularities can be easily removed with this type of finishing, which also pre-levels any surfaces to the point where they are ready for final finishing with other materials (tiles, wallpaper, etc.). Only after the concrete base has been meticulously prepared is the gypsum coating applied.

Features and Specifications

Due to the introduction of polymer additives into the composition, which increase the solution’s plasticity and adhesion to the base, the coating keeps a monolithic surface at a layer height of five to six centimeters. The material is lightweight and has a low density. Applying the solution to the wall causes it to set quickly and neither delaminate nor dehydrate. Without altering its properties, dried gypsum plaster draws in excess moisture from the air and releases it as the room temperature rises. There is no need for additional puttying when the plaster layer is prepared correctly.

Concrete with a gypsum coating has a 40-minute setting time (at room temperature plus or minus five to thirty degrees), which reduces finishing time and boosts output (10 to 15 m2 per shift at a 2 cm coating thickness). As a result, the building gains improved fire safety (the composition’s fire resistance matches concrete), hygienic qualities, sound and heat insulation, and aesthetic appeal.

The water-filled plaster must dry for several days in order to completely restore the surface’s aesthetic appeal. The direct "conflict" interaction between gypsum plaster solutions and concrete surface substances is a major drawback. Elevated levels of humidity (more than 5%) on the surface of the concrete, particularly lightweight concrete, lead to the release of moisture from the concrete into the gypsum plaster rather than its absorption from the solution.

Because of this, the material that makes up the plaster layer recrystallizes, which lessens its adherence to the concrete. Another risk is the years-long shrinkage of lightweight concrete brought on by a slow drop in the material’s humidity, which can cause stresses in the boundary layer and plaster finish cracking. This is how the coating detaches and breaks off from the base. In order to give good adhesive properties, a smooth concrete surface with an acceptable humidity level must first be coated with a deep penetration polymer primer because it absorbs moisture poorly.

Consumption of gypsum plaster

Within 20 to 30 minutes, the prepared solution must be consumed. A 15–20 liter bucket’s worth of work can be completed by one worker. To prepare, add cold water to which the mixture is added. 500–700 g of water for every kilogram of dry mixture is an approximate ratio (15–21 liters of solution are made from 15 kilograms of the material). The final mixture is thick and homogenous, similar to sour cream.

Once prepared, let it sit for five to seven minutes before recombining and working it out. Plastering approximately 3 m2 of surface (with a layer height of 1 cm) is possible with the solution’s considered volume, which is twice as much as plaster made of cement (50 kg bag). Consequently, 8.5 kg of gypsum mixture material will be used for every square meter of surface.

How to apply correctly?

The concrete surface (with a maximum moisture content of 5%) is prepared in the following ways: it is thoroughly primed, cleaned (to remove paint, dirt, and whitewashing), a shallow notch is made, exposed, roughness is created (cement "milk"), and stucco mesh is packed. Then, at a distance of 160 to 180 cm (for a 2-meter rule), metal guides-beacons are strictly installed vertically (along the entire length) on the mortar using a level. Using a stretched cord, the plaster layer’s depth is ascertained. The verticality and plane of the wall covering are set with 0.5 mm accuracy. Time is allowed for the solution to solidify.

Work begins with the area between the guides (the middle of the wall), then they move on to the corner fragments. The mixture is quickly applied with a spatula from the bottom up in a continuous layer to a height of about 100 cm (the maximum thickness of one layer is 6 cm). Then it is pulled out and leveled with a rule, moving it along the guides from the bottom up with simultaneous sequential movements to the left and to the right. The gaps and voids in the surface are filled with mortar, and the pulling is repeated until a satisfactory result is achieved. The possible chopping of the surface is eliminated by pulling the layer with the rule.

Plaster is poured into and removed from the following section in the same manner. Extra material is put to use. After 40 to 50 minutes, the surface can start to smooth. following the layer’s removal. The formed surface is smoothed using circular motions using a sponge that has been soaked in water and fixed on a board. A wide spatula and a trapezoid ruler are used to create the perfect level surface.

Using a plastering plane, the corners are cleaned. Following a fifteen-minute wait, the wall (or ceiling) should be glossy again by grouting with a damp sponge and using a steel trowel (spatula) with sweeping motions. Three to four repetitions of this procedure should be made during the day (but not before five hours have passed). Plastering the ceilings in a single layer at the same time involves moving the completed mixture in the direction of the ceilings. If a layer of gypsum greater than 2 cm in thickness needs to be applied to the ceiling, reinforcement in the form of a metal galvanized net should be used.

If more finishing is required, it is applied after the first layer has solidified. However, first the initial layer, which hasn’t dried yet, needs to be primed and combed with a comb to create some unevenness. The process is guaranteed to accelerate with the use of machine plastering technology. The completed mixture is supplied under pressure to the plastering area in order to do this. Then, the procedures are comparable to those previously mentioned.

How long does gypsum plaster dry?

At a temperature between plus 5 and 30 degrees, the composition dries and sticks to the concrete base while the windows are closed and there are no drafts. The room can be ventilated after a day to guarantee that any excess moisture is removed. Depending on the recipe, drying conditions, and the height of the laid solution, the material will finally gain strength in 6 to 14 days. However, this time is greatly increased in rooms with inadequate ventilation. The plaster surface turns light in color during the drying process.

Examples of manufacturers

The operational reliability of coatings is determined by the components’ purity and the quality of gypsum grinding. The production and usage technologies of dry mixtures are continuously being improved by their manufacturers.

Master Isopro

Gypsum plaster mixture (starter) up to a single layer’s maximum depth of five centimeters. continues to be environmentally friendly, shrink-resistant, and abrasion-resistant. increases the degree of sound and heat insulation in rooms and has a high vapor permeability.

Used to level surfaces made of brick, concrete, plaster, and sand-cement before painting or applying wallpaper. positioned atop a thoroughly cleaned base that has been primed with "Master Universal" and "Master Inner" compounds; "Master Hydrostop" emulsion is used to prime the concrete. The mixture should be ready in 90 minutes, with 20 degrees being the ideal temperature for use. A thickness of 1 mm requires 1.4 kg per square meter.

Knauf MP-75

With polymer fillers, ready mix. primarily applied to any solid base using a machine. 30 kg of packaging with a 0.5-year shelf life. 8–50 mm is the application thickness. 30 liters of solution are produced from 30 kg of dry mix.

10 kg of dry composition are needed to cover 1 m2 (thickness = 1 cm). In seven days, a 20 mm-high layer of gypsum dries at a temperature plus 20 degrees and 60% humidity. The base’s brick surface is primed beforehand using the mixture "KNAUF Rotband-Grund," "KNAUF Grundirmittel" (diluted 1/3 with water), and "KNAUF-Betonokontakt" primer (which dries in a day). Using the rule, the completed mixture is leveled along the beacons.

Knauf Rotband

Adhesion is improved by adding additives to a universal dry mix. It is meant to be applied manually to a variety of indoor hard surfaces, including those with elevated humidity levels. Packed in 5, 10, and 30 kg containers with a six-month shelf life. Pre-primed absorbent surfaces of the base are coated with "KNAUF Rotband-Grund," "KNAUF Grundirmittel" (diluted 1/3 with water), and "KNAUF-Betonokontakt" primer (which dries in one day) for concrete.

The plastered layer has a maximum thickness of 5 cm. Thirty kg of dry mix yields thirty-six liters of finished solution. For every square meter of surface, 8.5 kg of the final mixture are used (the solution’s height is 1 cm). Two centimeters of layer dries in seven days at room temperature and relative humidity.

Others

The market is overflowing with other manufacturers’ gypsum compositions for plastering surfaces. They are designed to be applied to the base by both machines and humans. Khabez, for instance, Osnovit, Volma, Starateli, Hercules, Rotgips, Volma-Sloy, Bystroy, Etalon, Bergauf, Teplon, etc.

Your walls and ceilings’ durability and appearance can be greatly affected by the gypsum plaster you choose for your concrete surfaces. You may choose the option that best meets the requirements of your project by being aware of the important variables, which include the type of concrete surface, the space’s intended use, and the unique qualities of the gypsum plaster.

The state of your concrete’s surface should be taken into account before choosing a gypsum plaster. A thinner layer of plaster may be sufficient for well-prepared, smooth concrete, but a thicker, more durable layer may be needed for uneven or rough surfaces. Selecting a plaster that offers a seamless finish and adheres well will be made easier if you are aware of the type of concrete and its current condition.

Another important consideration is the area where the plaster will be applied. Use moisture-resistant gypsum plaster in places like kitchens and bathrooms where there is a lot of moisture exposure or high humidity. This guarantees durability and avoids problems like mold growth or deterioration of plaster over time. Standard gypsum plaster can be adequate for living areas and bedrooms, providing a smooth and attractive finish.

Last but not least, the application procedure and drying period are crucial factors. Certain gypsum plasters dry more quickly and are easier to work with, which makes them perfect for last-minute renovations. Others might offer a better finish, but they might take more time and skill. Examine your degree of experience and the project schedule to select a plaster that fits your timetable and skills.

To sum up, the process of choosing the appropriate gypsum plaster for concrete necessitates an evaluation of the surface condition, environmental aspects, and application specifications. You can obtain a superior finish that amplifies the allure and longevity of your concrete surfaces by considering these factors.

It’s important to take the type of concrete surface, the desired finish, and the particular application requirements into account when selecting gypsum plaster for concrete. Seek for a plaster that is simple to apply, offers durability, and sticks well to concrete. Consider the working time, suitability for the intended use, and compatibility with the surrounding environment. You can improve the look and functionality of your concrete surfaces with a smooth, long-lasting finish by choosing the correct gypsum plaster.

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