Study on strength test and hydration mechanism of phosphogypsum based cemented backfill

Abstract In view of low early strength of phosphogypsum based slag cementitious material, exploration test of filling body strength is developed to get the optimal ratio of cementitious materials. Firstly, the physicochemical analysis of the test material was carried out; secondly, the cementitious material ratio and strength of waste rock coarse aggregate filling body was tested by orthogonal test and range analysis. In the end, the hydration products and microstructure of cementitious materials were analyzed by XRD and SEM. The results show that, for the slurry with waste rock coarse aggregate, 1:4 cement sand ratio and 80% mass concentration, the optimal ratio of cementitious materials is determined as phosphogypsum 30~33%, quicklime 5.5~6.0%, NaOH 1.5~2.0%, mirabilite 2.5~3.0%. The average particle size of cementitious material is - 16μm, and the early strength agent or synergist must be added, which could meet the requirements of the Jinchuan mine.