Gypsum-Plaster and Gypsum-Concrete Products

structural products made with a base of gypsum binding materials (primarily structural gypsum) and gypsum concrete. They include panels and slabs for partitions and walls, panels for floor foundations, sanitary facilities, ventilation units, and sheeting (plasterboard).

Although they have a number of positive characteristics (for example, fire resistance, good sound insulation, and comparatively low density), products made of gypsum plaster and gypsum concrete also have significant shortcomings (insufficient water resistance, comparatively low strength, and creep under load, especially under conditions of high humidity). Therefore, they are utilized mainly in nonsupporting or light-load structures that are protected from moisture. To increase their water resistance, these products are coated with waterproof protective paints or pastes; an increase in water resistance and a decrease in creep are also achieved by using cement-plaster-pozzolana binding materials. Gypsum-plaster and gypsum-concrete products may be solid or hollow (with no less than 15 percent of the volume occupied by hollow areas) and reinforced or nonreinforced.

Gypsum-concrete panels for partitions and walls are utilized in areas in which the relative air humidity does not exceed 60 percent. Solid panels, as well as panels with cutouts for doors and transom frames, are manufactured for residential buildings in sizes designed for a room or part of a room—up to 3 m high, 6 m long, and 80-100 mm thick. Gypsum concrete for panels must have an ultimate compressive strength of no less than 3.5 meganewtons per sq m (MN/m²), or 35 kilograms-force per sq cm (kgf/cm²). The sound-insulation and strength requirements for panels are met by gypsum concrete with a density of 1,250-1,400 kg/m³. Such panels are made primarily by the continuous-molding method on rolling mills. The magazine method of manufacture in vertical molds is also used. For walls and partitions that are exposed to moisture during their operation (for example, in sanitary units), panels made with a base of cement-plaster-pozzolana binding material are used.

Slabs for partitions and walls are made in either solid or hollow types; they are made of gypsum concrete or of gypsum paste (without aggregates) with dimensions of 800 × 400 mm and range in thickness from 80 to 100 mm. Rotary molding machines are used to form these slabs.

Panels for floor foundations are produced in sizes designed for a room or part of a room, with a thickness of 50-60 mm. They are made of gypsum concrete using a cement-plaster-pozzolana binder with keramzit or sawdust and are reinforced with wooden fillet frames. When it has dried to a constant weight, gypsum concrete must have an ultimate compressive strength of no less than 7 MN/m² (70 kgf/cm²) and a density of up to 1,200 kg/m³. These panels are placed on the reinforced-concrete flooring slabs with sound-insulation linings.

Sanitary units are three-dimensional elements made in vertical molds or assembled from individual panels. Gypsum concrete with a cement-plaster-pozzolana binder is used for the manufacture of these units. The walls of the units are reinforced with steel mesh. A reinforced-concrete slab faced with ceramic tile serves as the unit’s foundation and floor.

Ventilation units are slabs one story in height and 180 mm thick, with vertical holes 140 mm in diameter. They are made of gypsum concrete using a cement-plaster-pozzolana binder with a sand aggregate and are molded on mobile wheeled molds.

Sheeting (plasterboard) is a sheet material that is utilized for the interior finishing of walls and ceilings in areas with a relative air humidity of no more than 70 percent. The sheets consist of a gypsum core overlaid with laminated board; they are made on molding conveyers and are produced in lengths ranging from 2,500 to 3,300 mm and with a width of 1,200 mm and a thickness of 8-10 mm. Sheeting is fire-resistant and is easy to process. In addition to plasterboard, gypsum-fiber plasterboard (which is made without composition board) is also used; organic-fiber aggregates (ground wood, waste paper, and so on), which are added to the gypsum in amounts of up to 10 percent, are used as reinforcing material. Gypsum plaster and gypsum concrete with lightweight aggregates are also used in the manufacture of heat-insulation slabs and units and in the manufacture of fireproof products for facing metallic structures and elevator shafts.