Performance and mechanism of sand stabilization via microbial-induced CaCO3 precipitation using phosphogypsum

Phosphogypsum is a solid waste generated during the production of phosphoric acid. Effective utilization of phosphogypsum resources is a complex challenge. In this research, an innovative and eco-friendly sand consolidation technique, i.e., microbial-induced CaCO3 precipitation using phosphogypsum (MICPP), is applied to achieve phosphogypsum mineralization and sand stabilization. Phosphogypsum is employed as a calcium source for sand consolidation. To elucidate the efficiency and the mechanism of sand consolidation through MICPP, a series of experimental tests on the sand columns using varying phosphogypsum dosages and consolidation methods are conducted. The results show a positive correlation between the increase in phosphogypsum dosage and the increase in the compressive strength of the specimens. Concurrently, As the amount of phosphogypsum increased, the permeability coefficient of the sand columns decreased and the production of CaCO3 increased. Notably, the immersion method exhibits a superior curing effect compared to the stirring method. The MICPP-treated specimens significantly mitigated the risk of environmental contamination. The CaCO3 precipitated by the microbial action is predominantly in the form of calcite that effectively fills the voids, bond surfaces, and bridge gaps in the sand columns, thereby substantially enhancing the performance of sand columns. © 2024 Elsevier Ltd