Study on Performance Regulation and Mechanism of Quicklime and Biopolymer on Hemihydrate Phosphogypsum

In order to reduce the influence of impurities in hemihydrate phosphogypsum(HPG) on the environment and improve the workability of HPG, the effects of the content of quicklime and types of biopolymer (hydroxypropyl methylcellulose, xanthan gum, sodium polyacrylate(PAANa)) on the compressive strength, softening coefficient and ultrasonic velocity of HPG were evaluated. When the content of quicklime was 1.5% and the content of PAANa was 0.2%, HPG had the best mechanical properties and workability, its water retention rate can be increased by 5.8%, and unconfined compressive strength of 3 days increased by 10.3% and 7 days increased by 13.1%. Through the analysis of scanning electron microscope and X-ray diffraction, it was found that the hydration reaction of HPG was more sufficient, the pores size and number decreased, the number of impurities on the crystal surface decreased obviously, and CaF2 and other substances were formed by the reaction after the addition of quicklime. After adding quicklime and PAANa, the indicators of gypsum self-leveling mortar prepared by HPG meet the requirements of the standard.