Gypsum base self-leveling originated in Europe, as early as in the 1960s began to use gypsum base flat material, to the 1980s in Europe and the United States gypsum base self-leveling mortar has been very standardized and mature. Chinese gypsum base self-leveling began in the early 1990s, limited by production costs, the scale has not been expanded. In recent years, related enterprises have replaced natural gypsum with desulphurized gypsum and other industrial by-product gypsum, greatly reducing production costs, and related technologies are more mature. With the country vigorously promoting the comprehensive utilization of industrial solid waste, gypsum based self-leveling mortar has broad market prospects.The advantages of gypsum self-leveling
1, the use of self-leveling gypsum construction of the ground, accurate size, high levelness, no empty drum, no cracking; Easy and convenient operation, high efficiency; And can use pumping construction, the daily floor can reach 800~1000m2, than the traditional ground material construction speed is 5~10 times faster.2, used as "floor heating" leveling covering layer (floor heating compared with other heating methods, energy saving range is about 20%, such as the use of partition temperature control device, energy saving range can reach 40%), not like cement mortar layer, due to thermal expansion cold contraction cracking, drum phenomenon. 3. When self-leveling gypsum and cement mortar are used in the screed layer of the building ground, the final cost of the two materials is similar. If the use of self-leveling gypsum instead of cement mortar, thus reducing the amount of cement in the total cement output proportion is very small, less than 1%, basically will not affect the interests of cement production enterprises. Therefore, there is little resistance and great prospect in the application of self-leveling gypsum in our country's building materials market. 4, gypsum base self-leveling and hardening of the floor has a certain elasticity, feet feel warm and comfortable; And has a certain sound insulation effect.Anhydrite is mainly derived from natural gypsum, fluoropgypsum and calcined dihydrate gypsum. Anhydrite has poor hydration activity and low hardening strength, so it must be modified by grinding, heat treatment and adding activators. Previously, activators are generally used to change the solubility or dissolution rate of CaSO4, accelerate the formation rate of CaSO4·0.5H2O, increase the hydration and hardening ability of anhydrite and shorten the setting time. Activators mainly include: various sulfate (K2SO4, Na2SO4, Al2 (SO4) 3, FeSO4, CuSO4, alum, etc.), alkaline activators (cement, lime, etc.) and other salt activators (K2Cr2O4 and K, Na2Cr2O4). The activity of anhydrite is related to the type of activator, dispersion and surface defects. The anhydrite self-leveling mortar prepared by composite activator, water reducing agent, water retaining agent, admixture, aggregate, fiber and reducing agent has the compressive strength and flexural strength of 16.7MPa and 7.3MPa, bond strength of 0.57MPa, shrinkage rate of 0.045%, and the performance meets the standard requirements of Japan Housing Corporation.
