Mechanical properties and soluble phosphorus solidification mechanism of a novel high amount phosphogypsum-based mortar

Phosphogypsum (PG) has great potential for recovery and utilization, but its effective utilization is greatly limited by the harmful impurities mainly composed of soluble phosphorus (SP). Based on excess-sulfate phosphogypsum slag cement (PPSC), a novel type of high amount phosphogypsum-based mortar (HAPBM) is proposed, which is an ideal solidification material. HAPBM has good compressive strength with the high amount PG. The mechanical properties of HAPBM and the solidification mechanism of phosphorus are studied and analyzed. With the changes in PG particle size and sand-cement (s/c) ratio, the influence of SP on the system is further explored. The solidification ability of HAPBM to phosphorus is further studied by adding different forms of SP. XRD analysis shows that in addition to the Brushite, there are also differences in the existences of insoluble phosphorus (ISP) formed by different forms of SP in HAPBM. The leaching results of SP indicate that through the solidification of HAPBM, all groups of leaching solution can meet the Class I (cI = 0.02 mg/L) or II (cII = 0.1 mg/ L) limitation of national standard (GB 3838-2002). The microstructure is characterized in detail using SEM images, and the distribution of hydration products and ISP is elucidated through EDS and Mapping results. This study provides possibilities and references for the large-scale recovery and utilization of PG and the solidification of harmful impurities SP.