Research on the performance of a novel type of cemented filler material for coal mine opening and filling

Abstract In this study, Inner Mongolia Chahasu Coal Mine is considered as the research object and new type of cemented filling material is developed based on gangue, fly ash, and cement. The aim is to systematically optimize its performance and investigate the influencing factors to improve the proportion of cemented filling materials used in the coal mine filling and mining process. Thus, the study seeks to reduce production costs and enhance the utilization rate of solid waste. In the literature, various studies have focused on optimizing the performance of cemented filling materials, particularly in terms of reducing environmental impact and improving cost-effectiveness. Research abroad has made significant progress in optimizing filling materials under specific geological conditions, such as varying mineral compositions and groundwater influences. However, the challenge remains in balancing the physical properties like compressive strength, flowability, and durability with the efficient use of industrial byproducts such as fly ash and gangue. Studies also indicate that while cemented filling materials have been extensively studied for their strength properties, the interaction effects of multiple factors, particularly in complex mining environments, are not well understood. In contrast, domestic studies primarily focus on the basic performance of filling materials under less variable geological conditions, with limited emphasis on how environmental complexities impact the optimization process. Furthermore, many studies do not fully address the role of gangue particle size and fly ash in improving the environmental sustainability and cost-effectiveness of filling materials. To fill this gap, this study combines the response surface methodology with optimization of the gangue particle size gradation to create a response model between cement, fly ash, solid content, and the filler body’s compressive strength. According to the test results, the filling materials’ strength and flowability were maximized when the grading factor of the gangue particle size was set at n = 0.5. A Box–Behnken experimental design was then used to examine the influence patterns of cement, fly ash, and solid content on the filling body’s strength at the early (3 days), middle (7 days), and late (28 days) stages, focusing on both single-factor and multi-factor interactions. The study found that the primary determinants of strength were the cement mass fraction and solid mass fraction, with fly ash’s contribution becoming more significant in the later stages of curing. The optimized ratios not only met the filling strength requirements but also significantly reduced cement usage and increased the utilization rate of fly ash, demonstrating the potential for both cost reduction and effective resource usage of solid waste.