What is this material and what is it used for?
Construction gypsum( alabaster) is an environmentally friendly, natural finishing material. Due to the properties of fast setting, it is used for the installation of electrical cables, for making such putty as gypsum putty, for installing beacons on plaster, for coating holes, for producing sheets of plasterboard. On strength, it is divided into three groups:
- 1 grade - compressive strength - 5.3 MPa;
- 2 grade - the limit is not less than 4.5 MPa;
- grade 3 - the limit is not less than 3.5 MPa.
This material in the dried state "breathes", that is, when the room is too much moisture, it absorbs it, when it is not enough, on the contrary, it gives. This makes the gypsum a natural regulator of the moisture level in the room. With different temperature processing, the material receives a variety of properties and is divided into building, molding, high-bending and technical.
Gypsum for plastering is necessary for the rate of solidification of the mixture. So, if you use three parts of gypsum and one part of putty, then the mixture will quickly grasp. The exact proportions for the mixture of gypsum and putty are not present, therefore it is done by experience.
Secrets of the preparation
Using the plaster cast in work, it is necessary to take into account its rapid solidification, as well as the fact that when it mixes with water it increases in volume and heats up. Gypsum, mixed with water, forms a plastic dough, which becomes firmer as it dries. The solidification moment comes in four minutes, and completely it hardens in six minutes.
For its kneading it is necessary to take two parts of gypsum and one part of cold water. It is important first to pour the water, and then, mixing, add gypsum. The finished mixture is not suitable for storage, so it immediately needs to use everything. Dry material is stored in tightly closed containers to limit air penetration. The recommended shelf life is not more than three months, since, after this time, it begins to lose its qualities.
Note! Tightly closed from the air, it is especially necessary to keep the moist gypsum, since it has very low water resistance.
To make the hardening process less intense, 0.5 to 2% of the water-soluble adhesive must be added to it. It can slow down the grasping process, but not for long. Lime mortar can also be added. Many people use ordinary washing powder for this purpose, dissolving one teaspoon per liter of water.
Rules for quality work
If you chose gypsum as a material for plastering, the question arises, how to plaster with gypsum? In principle, working with him is no different from working with any other putty. The only thing that must be constantly remembered is that it quickly grasps, so you should work quickly. Often this material is used for leveling walls and ceiling. Aligning the walls with gypsum is done in the following order.
The first step is to check the condition of the surface. All movable and loose elements on the surface will lead to flaking of the plaster, so they are fixed or removed. If the layer of old plaster is repaired, the damaged places are completely knocked down, and the wall under them is cleaned.
Remember that gypsum causes corrosion of metal elements, so all such parts must be covered with an anti-corrosion solution. Plastering of walls with gypsum necessarily requires preliminary priming of the surface. Also, a fiberglass mesh is fixed at the joints of various materials( concrete and ceramics, etc.).
The gypsum walls can be finished manually or mechanically. Focusing on the type of application, prepare a solution, for each of which there is a type. Gypsum mixture quickly hardens, so the master needs a clear organization of work and experience. The solution is applied in one layer, but if a nylon mesh is reinforced, another layer is applied.
Light solutions are used for the ceiling, and the thickness of the layer should not be more than 15 mm. The walls are plastered with a heavier composition, and the thickness should not be more than 20-25 mm. If you do not have experience with this material, it's best to entrust it to a specialist.