Highly efficient modified phosphogypsum building gypsum powder and environmentally friendly utilisation in self-levelling mortar

The stockpiling of phosphogypsum is a waste of land resources and also causes serious pollution to natural resources such as water and atmosphere. This paper explores the mechanism of efficiently modified phosphogypsum and constructs a model and evaluation system for heavy metal leaching and migration transformation. The modified phosphogypsum is used in self-levelling mortar to promote sustainable development within the phosphogypsum industry. It was shown that the phosphogypsum, first treated by ball milling for 5 min and then modified at low temperature of 165 °C, had a flexural strength of 2.35 MPa and a compressive strength of 4.28 MPa, which meets the requirement of strength of phosphogypsum of grade 2.0 in “Calcined gypsum” (GB/T9776-2008), and its flexural and compressive strength is 17.5% and 7% higher than 2.0 grade. This is due to the generation of better hydration activity of CaSO4・0.5H2O in the process of modification, which can hydrate to form more needle and columnar calcium sulphate dihydrate crystals, the crystals are interlaced, overlapped or overlapped with some lamellar structures, forming a network of gypsum dihydrate crystals, so that the gypsum blocks get good mechanical properties. The results of heavy metal environmental assessment and kinetic model fitting showed that there was no environmental and health risk for the high-efficiency modified phosphogypsum, and the Elovich model and second-level kinetic model were fitted to the leaching pattern of characteristic pollutants. Using ArcGIS and other interpolation, vertical distribution simulation, profiling with the increase of placement time of phosphogypsum in the content of heavy metal elements appeared to be a significant decrease, and the spatial distribution characteristics of heavy metals and altitude there was a negative correlation between modified phosphogypsum applied to self-levelling mortar, the flexural strength of 3.1 MPa, compressive strength of 8.9 MPa, met the standard requirements of “Gypsum based self-levelling compound for floor” (JC/T1023-2021). By analysing the LCA and carbon emission per tonne of self-levelling mortar based on the life cycle parity, it can be showed that terrestrial ecotoxicity, freshwater ecotoxicity, marine ecotoxicity, human carcinogenic toxicity were the main types of damages in all damage categories and the carbon emission in the raw material acquisition stage accounting for 79.8%.

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Opracowanie rekordu ze środków MNiSW, umowa nr POPUL/SP/0154/2024/02 w ramach programu "Społeczna odpowiedzialność nauki II" - moduł: Popularyzacja nauki (2025).