Effect of Calcium Ion Concentration in Wastewater on Failure Behavior of Mine Waste Backfill Material

The arid western region, characterized by minimal rainfall and limited water resources, is further burdened by the accumulation of solid waste and high-calcium wastewater, a byproduct of mineral resource extraction and industrial activity. In the hope of safeguarding water resources and realizing comprehensive treatment of solid waste and high-calcium wastewater, laboratory simulation was conducted in this study. To be specific, mechanical testing and microanalysis were performed on samples with the aid of a universal testing machine, an acoustic emission monitoring system, a scanning electron microscope, and an X-ray diffractometer. On this basis, a novel method of enhancing the solid waste-based paste filling materials (SWBPFMs) with high-calcium wastewater was proposed. The following findings were obtained. High-calcium wastewater serves to facilitate the production of Friedel’s salt within SWBPFMs, and Friedel’s salt acts to enhance the microstructure of SWBPFMs by reducing their porosity, thereby improving their performance. Besides, Friedel’s salt exhibits the most substantial reinforcing effect on SWBPFMs (increase their strength by approximately 8.56 times) under a mass concentration of 78%, a gangue dosage of 58%, a cement dosage of 10%, a fly ash dosage of 10%, and a Ca ²⁺ concentration of about 29.3%. The proposed method not only offers a viable solution for the transformation of solid waste and wastewater but also addresses the industrial water shortage in the western region. It paves the way for the recycling of waste resources and promotes sustainable development.