Very often, for various finishing works , such material as building gypsum is used. Even people far from repair and design know this name. For many centuries, it has been an ideal material for the reconstruction and repair of premises.
Very finely ground gypsum for construction does not create a difference between new and old coatings of walls and ceilings. It has an excellent structure and does not crack. Work with gypsum begins with mixing it with water. With the right consistency, this material perfectly fills cracks and takes the form of even small parts.
Building gypsum has a porous structure, so all surfaces treated with this material are capable of absorbing sound waves well, thereby ensuring soundproofing of the room. The white color of this material allows it to be used without additional staining where perfect whiteness of coatings is required.
How do you get this building material? A natural gypsum stone having a crystalline structure is processed at high temperatures. In this case, of water is lost, and the mineral itself turns into hemihydrate, which, when mixed with water, again takes on the structure of natural stone. Since in the production of gypsum no more than 1% of other organic substances are added to the natural material, it is environmentally friendly for people and animals. This building material is fireproof, therefore it plays a big role in protecting the premises from fire. In addition to all of the above properties, it is able to absorb excess moisture in the rooms when it increases and to give moisture when lowering its level.
Gypsum is available in several varieties. Conventional building materials are used for the manufacture of gypsum concrete and gypsum products, dry plaster, panels and partition walls, gypsum-lime plaster mortars. High-strength molding gypsum is produced by special mechanical refinement of ordinary building material, subjecting it to cleaning and additional grinding. Stucco molding and other decorative products for interiors and facades are made of it. Building gypsum is divided by the time of its hardening: 2-15 minutes - quick setting; 6-30 minutes - normally set; over 20 minutes - slowly setting.
The strength of this material is determined by its grades, which differ in their compressive strength (G-2, 3, 4, 5, 6, 7, 15, 10, 19, 16, 22, 25). Gypsum grades G-10, 16, 15 are considered molding. Such material is practically free of impurities and is highly durable.
When working with this material, it should be remembered that it hardens rather quickly, so you should not immediately cook a 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 the creation of various products. Excess water may remain in the pores of the hardened material, after which it evaporates. As a result, the porosity of building gypsum will be about 50-60%. It is important to remember that the less water used to breed gypsum, the denser the finished product or coating will be and the higher its strength. An increase or decrease in temperature has a negative effect on 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 gypsum 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 increased porosity, so human skin continues to breathe freely, which prevents the occurrence of itching. Sometimes these dressings are applied so that patients can perform some movements. This material does not interfere with medical procedures and x-ray examination.