Very often, in various finishing works, such material as building gypsum is used. Even people who are far from repair and design know this name. For many centuries, it has been an ideal material for the reconstruction and renovation of premises.
Very finely ground building gypsum does not create a difference between new and old wall and ceiling coverings. It has an excellent structure and does not crack. Working with plaster begins with mixing it with water. With the right consistency, this material perfectly fills cracks and takes the shape of even small parts.
Building gypsum has a porous structure, so all surfaces treated with this material are able to absorb sound waves well, thereby providing soundproofing of the room. The white color of this material allows it to be used without additional coloring where perfect whiteness of coatings is required.
How do you get this building material? Natural gypsum stone, which has a crystalline structure, is processed at high temperatures. In this case, the loss of ¾ of the water contained in it occurs, and the mineral itself turns into a hemihydrate, which, when mixed with wateragain takes on the structure of natural stone. Since no more than 1% of other organic substances are added to the natural material during the production of gypsum, it is environmentally friendly for people and animals. This building material is fireproof, therefore it plays an important role in protecting the premises from fire. In addition to all the above properties, it is able to absorb excess moisture in the premises when it rises and release moisture when its level drops.
Gypsum is produced in several varieties. Conventional building materials are used for the manufacture of gypsum concrete and gypsum products, dry plaster, panels and partition boards, gypsum-lime plaster mortars. High-strength molding gypsum is produced by special mechanical processing of ordinary building material, subjecting it to cleaning and additional grinding. Stucco and other decorative products for interiors and facades are made from it. Building gypsum is divided according to the time of its hardening: 2-15 minutes - quick-setting; 6-30 minutes - normally setting; over 20 minutes - slow setting.
The strength of this material is determined by its grades, which differ in the limit of its compressive strength (G-2, 3, 4, 5, 6, 7, 15, 10, 19, 16, 22, 25). Plaster of grades G-10, 16, 15 is considered to be molding. This material contains virtually no impurities and is highly durable.
When working with this material, remember that it hardens rather quickly, so do not cook immediatelya large amount of diluted gypsum. The amount of water required to obtain a mixture of normal density, as a rule, is 50-80% (for construction work) and 35-45% for creating various products. Excess water may remain in the pores of the hardened material, after which it evaporates. As a result, the porosity of the building gypsum will be about 50-60%. It is important to remember that the less water used to dilute the gypsum, the denser the finished product or coating will be and the higher its strength. An increase or decrease in temperature is bad for the strength of the hardened material. To increase the strength of building gypsum, about 5% slaked lime is sometimes added to it.
For medical use, the so-called polymer plaster is produced, which is easily applied to the patient's injured body with a bandage. It perfectly follows the contours and has increased extensibility. This material has a high porosity, so the human skin continues to breathe freely, which prevents itching. Sometimes such bandages are applied so that patients can perform certain movements. This material does not interfere with medical procedures and X-ray examinations.
