plaster
Gypsum is a mineral name, the main chemical composition is calcium sulfate (CaSO4), mainly the ancient salt lake or lagoon sediment. Gypsum is used as an agricultural fertilizer that can improve alkaline soils for general neutral or acidic soils that can improve the soil structure and supply calcium and sulfur components. Widely used in industrial materials, medical materials and building materials. Can be used for cement retarder, gypsum construction products, model production, medical food additives, sulfuric acid production, paper filler, paint filler, fracture fixation, but also as a blackboard with chalk. Natural dihydrate gypsum (CaSO4 · 2H2O), also known as gypsum, after calcination, grinding can be β-type semi-water gypsum (CaSO4 · 1 / 2H2O), that is, building plaster, also known as plaster, plaster. If the calcination temperature is 190 ° C, the model gypsum is available, and its fineness and whiteness are higher than that of the building gypsum. If the gypsum in the 400 ~ 500 ° C or higher than 800 ° C calcined, that is, floor gypsum, the condensation, hardening slower, but after hardening strength, wear resistance and water resistance are better than ordinary building plaster as well. ...