Recall that gypsum binders are building binders obtained by roasting and grinding from two-water gypsum contained in sedimentary rocks.
Depending on the processing temperature, they are divided into two more groups: low-fired and high-fired. High-fired gypsum binders - this is the so-called anhydrite cement and extreme gypsum - actually high-fired gypsum. Low fired gypsum binders are a molding and high strength building gypsum.
We give a more accurate classification of gypsum binders. As a rule, all their diversity is divided into 12 grades according to tensile strength:
|Brand:||: Bending strength, MPa, not less|
Depending on the setting time, gypsum binders are divided into quick setting (start of setting - 2 minutes, completion of setting - 15 minutes), normal setting (beginning of setting - 6 minutes, completion of setting - 30 minutes) and slow-setting (start of setting - 20 minutes, completion of setting - not standardized). According to the degree of grinding, gypsum binders are divided into coarse, medium and fine grinding compositions.
Gypsum binders are used as an independent basis for building mortar or added to mixtures on other substrates - for example, in lime-sand mortars to increase their strength and accelerate setting. Adding gypsum binders to the plaster allows for better smoothness and whiteness of the surface. For the manufacture of building mixtures and products mainly gypsum grades from G-2 to G-7 are used. In the manufacture of products, gypsum binders are shut not only with water, but also with dispersions of polymers - in this way a polymer gypsum is obtained that is significantly superior to ordinary gypsum in many respects: in density, strength (up to 30 MPa), water resistance, volume constancy, abrasion resistance, and electrical insulation properties.
Gypsum binders, packed in containers, are transported in closed wagons and cars, stored in rooms that are reliably protected from moisture. With prolonged storage, even under normal conditions, the activity of gypsum binders decreases.