A significant quantity of tailings is produced during the development of different metal mines in China. In particular, fine-grained tailings pose challenges to the sustainable development of the mining industry. This study examines the utilization of finely ground tungsten tailings as a replacement for natural aggregates in self-leveling mortar (SLM). The study examined the impact of the aggregate-cement ratio, cement mix ratio, and varying substitution levels of different grain sizes of tungsten tailings on the flow properties, mechanical properties, and dimensional change rate of SLM. Additionally, the role of tungsten tailings in SLM was analyzed using XRD, FTIR, and SEM methods. The findings demonstrated that the utilization of sulphoaluminate cement (SAC) had a notable impact on improving the initial strength of the SLM. Additionally, a high aggregate-cement ratio negatively affected the fluidity of the SLM. The doping of tungsten tailings improved the grading relationship of the SLM. Substituting tungsten tailings of 38–75 μm grain size for natural aggregates in the preparation of SLM did not have a negative impact on its performance. In fact, substituting 60% tungsten tailings had a positive effect on the 28-day mechanical properties of the SLM. The compressive and flexural strengths of the SLM after 28 days were 26.53 MPa and 9.06 MPa, respectively, which were enhanced by 18.81% and 26% compared to the control group (C0). According to the environmental leaching test, SLM can effectively fix the heavy metal ions in tungsten tailings, and the leaching concentration of heavy metals is significantly reduced after long-term curing. The doping of finely fragmented tungsten tailings accelerated the process of hydration, resulting in the creation of hydrocalcium zeolite crystals in the latter phases of hydration. Furthermore, an increase in tailings substitution resulted in the production of a greater amount of hydration products, specifically C-S-H gels.
