A high performance water resistance agent KD-3 prepared from OPC cement, fly ash, slag and additives was used for the modification of hemi-hydrate desulphurization gypsum. Various factors on gypsum block were investigated. The prepared gypsum block possesses excellent water-resistance, good operating property and high mechanical strength. The optimized results was obtained: calcined gypsum 74.9%, KD-3 25%, retarder 0.1%, curing temperature 60°C and curing time 16h.
The condition of preparing α-hemi hydrate gypsum from FGD gypsum at atmospheric pressure is easy to achieve. It acquires atmospheric pressure and low heating temperature. This paper introduces two different methods of preparing α-hemi hydrate gypsum, aqueous salt solution method and dry dehydration. Use the microscopic characterization of α-hemi hydrate gypsum to identify the product. Observe the crystal of product by stereo microscope and characterize the compounds with Fourier transforms infrared spectroscopy. Investigate the factors’ effects between the two methods.
A kind of FGD gypsum from Ningbo Beilun Power Plant of China and fly ash were used as the raw materials with which a complex cementing material was made. Effect of the related factors such as water proportion, mineral admixtures and chemical activators on characteristics of Hemi-hydrate FGD gypsum-fly ash complex cementing material is studied through a number of single factor experiments. The experimental results show that an appropriate amount of admixtures can effectively improve the strength of the Hemi-hydrate FGD gypsum–fly ash complex cementing material presented here. It is concluded that the strength of HFGD-FACM is best as the ratio of HFGD gypsum and fly ash is 1:1 and proper water aggregate proportion is 0.45~0.50.
Theoretical Interpretation of the Existence at 40℃ of an Absolute Maximum of the Hydration Rate of Calcium Sulphate Hemi Hydrate under Microwave Irradiation