Effect of pretreatment method on properties of excess-sulfate phosphogypsum slurry
Excess-sulfate phosphogypsum slag cement(PPSC)was prepared by four different pretreatment methods of phosph-ogypsum.The effects of various methods on the working performance and compressive strength of PPSC slurry were compared.The results show that the performance and compressive strength of the slurry prepared by phosphogypsum pretreatment are greatly im-proved.The flowability of the excess-sulfate phosphogypsum cement slurry produced by co-grinding method 3 is high,reaching 175 mm,the compressive strength of the slurry produced by wet grinding of phosphogypsum in method 4 has been significantly im-proved,reaching 35.7 MPa,an increase of 111.2％,but excessive treatment has little effect on the strength improvement.According to XRD and SEM analysis,the types of hydration products will not be changed by pretreatment.The hydration products of PPSC are mainly ettringite and C-S-H gel,and there are unreacted gypsum particles.The compressive strength of the test block is related to the composition of hydration products and the degree of coating phosphogypsum,and is also affected by the density of structure.
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