Utilization Of Industrial By-product Gypsumand And Its Application In Architecture Powder Coating

Industrial by-product gypsum is also called chemical gypsum, generated by the chemical reaction in industrial production and calcium sulfated as the main component (contains 0 to 2 hydration water). It is a good renewable resource. Its utilization is conductive to protecting the environment and saving energy and resources. Building materials industry is very important in the development of recycling economy. The industrial by-product gypsum can be used as a substitute raw material and it can be contributed to building a resource conserving and environment-friendly building materials industry.However, the industrial by-product gypsum always contains impurities during the production process which have bad effects, and gypsum also has the technical choke of low strength, feeblish water-resistance and so on. These disadvantages are imperative problems of by-product gypsum. In this paper, the utilization of FGD and phosphogypsum has been investigated systematically, and attains some significant results and theories on the basis of a large number of experiments; the main tasks are as follows:(1) has studied the sintering temperature on the impact of gypsum and phosphogypsum and found that when FGD is calcined into semi-hydrated gypsum at about 150℃, the properties can achieve the national standards of GB/T 9776-88; when phospogypsum is calcined into anhydriteⅡat about 800℃, it can get good post-hydrated gypsum ability.(2) the semi-hydrated gypsum, the anhydriteⅡand the slag are prepared into gypsum-slag composite cementitious material, using CaO and white cement as activator respectively. The results show that the CaO and white cement can effectively improve the strength and water resistance of cementitious material; the white cement has better impact than CaO.(3)the microstructure analysis shows that both CaO and white cement can make the internal structure of cementitious material to be more density, so the strength and water resistance are improved, but the excessive quantity of CaO will produce gelatious ettringite which will expand the system and produce micro-cracks. The ettringite produced by white cement is the main factor of the material's strength. It plays an important role than C-S-H gel, but excessive ettingite will also expand the system and produce micro-cracks which will reduce the mechanical properties of the cementitious material.(4) the organic silig glue powder can improve the bond strength and water resistance, particularly in the 28-days post-hydration process, the polymer film produced by organic silig glue powder with various crystals and particles can form dense network structure, then fill the small holes of the material's interior system, improving the properties of the material.(5) has studies the preparation of powder coating by using composite cementitious material. The experiment results show that the polyvinyl alcohol and re-dispersible polymer powders both play an important role of the coating properties, they can improving the alkali resistance, freezing and thawing cycle resistance, dry rub resistance, scrubbing resistance, ect. The polyvinyl alcohol has a smaller consumption and better effects than re-dispersible powder.(6) by comparing the properties of powder coating and national standard of interior wall coating, the results show that it can be fully achieved the national standards or even better. The industrial by-product gypsum composite cementitious material based powder coating have many advantages, like excellent propeties, low price, environmental friendly, saving energy and using convenient, it's application has great market potential.