Mixture ratio of phosphogypsum in backfilling

Abstract

Filling the goaf with phosphogypsum can reduce damage to the environment due to phosphate mining. Research was conducted to test the feasibility of using phosphogypsum as a backfill aggregate, concentrating on the mixture ratio of filling materials and the filling process. First, the physical and chemical characteristics of phosphogypsum, fly ash and yellow phosphorus slag were determined. Then, two types of cement strength tests were conducted. One type of cementation was made up of phosphogypsum, cement and fly ash; the other was made up of phosphogypsum, yellow phosphorus slag, alkali activator and composite water reducer. The test results show that by adding fly ash, the characteristics of phosphogypsum change making it usable as a backfill aggregate. In addition, the curing agent of cement can be replaced by the yellow phosphorus slag, and a reasonable mixture ratio for backfill materials can be obtained. The new cemented backfill technology (in which the phosphogypsum is used as the main filling aggregate) was developed and used to fill the goaf of a phosphate mine in YongShaBa (KaiLin Group). Engineering practice has shown that the phosphogypsum filling technology can significantly reduce the environmental damage caused by phosphate mining, and significant economic benefits can be achieved.