Phosphogypsum and desulfurization gypsum are industrial solid wastes with the largest storage capacity,and transforming them into hemihydrate gypsum as building materials is the best way for resource recycle.The α-hemihydrates gypsum was obtained by autoclave method from different industrial gypsum including desulfurized gypsum(FGD),phospho-gypsum(PG)and natural gypsum(NG)as a control group.The effects of crystal modifiers including sodium dodecyl ben-zene sulfonate(SDBS),aluminum sulfate[Al2(SO4)3]and compound crystal modifier(CM)on the morphology and strength of α-hemihydrates gypsum were investigated.The results showed that under autoclaved pressure at 135℃ for 5 h,α-hemi-hydrate gypsum could be prepared by three types of gypsum stably,three types of crystal modifiers had no impact on the phase composition of hemihydrate gypsum.0.4％CM could reduce the aspect ratio of crystals effectively.Based on T-test,the crystal modifiers had significant enhancing effect on the compression strength of α-hemihydrate gypsum prepared from FGD and NG,which was increased by more than 2 times to 13.59 MPa and 17.45 MPa,respectively.However,the strength of α-hemihydrates gypsum prepared by PG had no obvious change by adding crystal modifiers.The results exhibited that 0.4％CM could reduce the aspect ratio of crystals and improved compressive and flexural strength significantly of α-hemihy-drates gypsum prepared from FGD and NG.The crystal modifier had no obvious impact on α-hemihydrates gypsum pre-pared from PG due to impurities.The results of the study provided a certain degree of theoretical guidance for the industrial production of different gypsum.
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