To apply phosphogypsum as a cement retarder,pre-treatment of phosphogypsum is carried out by water washing and other methods.Determine the optimal water consumption and washing time of water-washed phosphogypsum.The effects of natural gypsum,as-built phosphogypsum and modified phosphogypsum on the setting time and strength of silicate cement were compared and investigated.The effect mechanism of modified phosphogypsum on the hydration characteristics of silicate cement was analyzed by heat of hydration,XRD and SEM.The results showed that phosphogypsum has the best water washing effect under the condi-tions of liquid-solid ratio of 4 and washing time of 25 minutes,the compounding of quicklime,quicklime and bentonite showed better curing effect on soluble phosphorus and soluble fluorine in phosphogypsum:the washed modified phosphogypsum could effec-tively shorten the setting time and improve the early strength of cement,in which the washed modified phosphogypsum with quick-lime and bentonite compounded at 2∶1 was used for silicate cement,the initial setting time and final setting time of cement were shortened by 50％and 31％compared with the original phosphogypsum.The early hydration rate of cement prepared by modified phosphogypsum is normal,the cement solidification body structure is dense,with fewer defects and high early strength.
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