The main chemical component of gypsum is calcium sulfate (CaSO4) hydrate. Gypsum is a versatile industrial and building material. It can be used for cement retardant, gypsum building products, model making, medical food additives, sulfuric acid production, paper filler, paint filler, etc. The microporous structure and heating dehydration of gypsum and its products make it have excellent sound insulation, heat insulation and fire resistance.
Natural gypsum ore
The main variety of gypsum
1. Natural gypsum
Natural gypsum is gypsum in nature, the main component of natural gypsum is calcium sulfate, according to whether there is crystalline water and divided into two kinds of gypsum dihydrate and anhydrous gypsum. It also contains some clay impurities and attached water, and is an important non-metallic mineral with a wide range of uses, non-toxic and harmless to the human body.
Since ancient times, it has been used in food, medicine, building materials and other fields.
2. Industrial by-product gypsum (chemical gypsum)
Industrial by-product gypsum refers to the general term for by-products discharged from industrial production with calcium sulfate as the main component, also known as chemical gypsum or synthetic gypsum. It is currently widely used in the main raw materials of plastering gypsum, which is used in plaster: desulfurization gypsum, phosphorus gypsum, fluorine gypsum.
Desulfurized gypsum
Desulfurization gypsum is a substance with calcium sulfate as the main component obtained after the flue gas and the desulfurizer (limestone) slurry are reversed to generate calcium sulfite in the desulfurization reaction tower, and then after the forced oxidation reaction.
Phosphogypsum
Phosphogypsum is an industrial by-product of the wet production of phosphoric acid, each production of 1t phosphate produces about 4t ~ 5t phosphogypsum, its impurities are mainly phosphorus, fluoride, silica, organic matter and other impurities affect the performance of phosphorus gypsum after hydration and hardening. When using, we must pay attention to the harmless treatment of its impurities.
Fluoroglottash is a by-product of the preparation of hydrofluoric acid, each birth of 1t hydrofluoric acid has 3.6t anhydrous fluorine gypsum generation, the production of fluorine gypsum is type II anhydrous gypsum, of which calcium sulfate content of up to 90% or more. After long-term storage, it will be converted into fluoride gypsum dihydrate, and it should be dehydrated according to the requirements when used.
3. Construction plaster
Construction gypsum is a natural dihydrate gypsum or industrial by-product dihydrate gypsum heated and dehydrated at a certain temperature, made of β- calcium hemihydrate sulfate as the main composition of the gas-hard cementitious material. Its characteristics are fast condensation hardening, good fluidity, small expansion rate, long fire protection time, and is the only material with respiratory function among the three major cementitious materials, and its biggest weakness is poor dynamic solubility, which can only be used on the inside of the building.
4. Anhydrous gypsum
Anhydrous gypsum is also known as insoluble gypsum. It is obtained by calcination and dehydration by calcination at high temperature at 360 degrees to 1000 degrees, and is a stable final product at room temperature. Natural anhydrite that exists in nature also belongs to this category.
Because the hydration hardening of anhydrous gypsum is very slow, the gelling performance is difficult to exert. Therefore, when using it to prepare new building materials, it is necessary to activate the excitation and increase the hydration rate to achieve the desired material properties.
5. High strength plaster
High-strength gypsum is a powdery cementitious material with calcium sulfate hemihydrate obtained under certain temperature, pressure or transcrystalline agent conditions in saturated water vapor medium or liquid aqueous solution, and calcium sulfate hemihydrate obtained under certain temperature, pressure or transcrystalline agent conditions. Its drying compressive strength is generally > 40MPa, the advantage is high strength, small expansion coefficient. It can be used to produce lightweight plaster plaster with a bulk weight of less than 700kg/m3, self-leveling gypsum and other products.