Gypsum is an astringent powder, indispensable in many branches of construction and medicine.
Gypsum has been known since antiquity, but still has not lost its popularity, even many modern materials cannot compete with it. It is used in the construction, porcelain, ceramics, oil and medicine industries.
Description of building material
Gypsum is made from gypsum stone. To obtain gypsum powder, the stone is fired in rotary kilns and then ground to form a powder. Most of all, gypsum is used in construction.
Walls plastered with gypsum mortar are able to absorb excess moisture and release it when the air is too dry.
Gypsum formula
The name gypsum comes from the Greek word gipsos. This material belongs to the class of sulfates. Its chemical formula is CaSO4?2H2O.
Specifications and properties
For all gypsum mixtures, the technical characteristics are very similar, let's dwell on the properties and features of building gypsum.
These include:
-Density. Gypsum has a dense fine-grained structure. The true density is 2.60-2.76 g / cm. In a loosely poured form, it has a density of 850-1150 kg / m, and in a compacted form, the density is 1245-1455 kg / m.
-How much to dry. The advantages of gypsum include fast setting and hardening. Gypsum seizes in the fourth minute after mixing the solution, and after half an hour it completely hardens. Therefore, the finished gypsum mortar must be used up immediately. To slow down the setting, water-soluble animal glue is added to the plaster.
-Specific gravity. The specific gravity of gypsum is measured in kg/m in the ICSC system. Since the ratio of mass is equal to the volume it occupies, the specific, volumetric and bulk density of gypsum is approximately the same.
-What temperature can it withstand (melting t). Gypsum can be heated to t 600-700°C without destruction. The fire resistance of gypsum products is high. Their destruction occurs only six to eight hours after exposure to high temperature.
-Strength. Building gypsum in compression has a strength of 4-6 MPa, high-strength - from 15 to 40 MPa or more. In well-dried samples, the strength is two to three times higher.
-Thermal conductivity. Gypsum is a poor conductor of heat. Its thermal conductivity is 0.259 kcal/m deg/h in the range from 15 to 45°C.
-Solubility in water. It dissolves in small quantities: 2.256 g dissolves in 1 liter of water at 0 °, 2.534 g at 15 °, and 2.684 g at 35 °; further heating decreases the solubility again.
