Microscopic Evaluation of Environmental Properties of Cement-Cured Graphite Tailings Modified with Calcined Kaolin

Massive accumulation of graphite tailings (GTs) seriously affects the ecological environment. In the process of recycling and reutilization, there are problems such as restricted use pathways and low use quantities. To alleviate these problems, in this study, calcined kaolin (CK) was added as an auxiliary cementitious material to cement-cured GTs, and the effects of the addition of CK on the compressive strength, impermeability, and heavy metal leaching concentration of the GT-cured material were analyzed through experimental studies. The micromorphology of GT-cured material was analyzed using techniques such as electron microscopy (SEM), energy dispersive spectroscopy (EDS), and x-ray diffraction (XRD). The results showed that 5% was the optimal addition rate of CK in GT-cured compounds. After 28 days of maintenance, the GT-cured body with 91% sand content showed the greatest increase in compressive strength and impermeability, by 39.7% and 70.3%, respectively, with the addition of 5% CK. Compared with the raw material GT, the leaching concentration of heavy metal ions in the solidified body of GT prepared by adding CK meets the requirements of environmental protection. Microscopic analysis results indicate that appropriate addition of CK effectively promotes cement hydration without altering the type of hydration products; it also improves the pore structure of the solidified body, which is beneficial for enhancing the overall performance of the solidified material. This study provides a new approach for the environmentally friendly application of GT.