Effect of the Cement–Tailing Ratio on the Hydration Products and Microstructure Characteristics of Cemented Paste Backfill

Cemented paste backfill (CPB) has been widely incorporated into mining practice as an ideal way to protect the environment and eliminate hidden dangers in mines. In this study, the feasibility of CPB was validated using full tailings from the Xianglushan Tungsten Mine. Through a microexperiment of CPB with different C/Ts, digital images of pores were obtained, and the hydration products were identified for processing with the particle and pore identification and analysis system. The evolution of hydrated products under different cement–tailing ratios (C/Ts) was analyzed. Then, microquantitative indices, such as the porosity and fractal dimensions, were used to analyze the evolution of the pore structures under different C/Ts. The results showed that CPB slump of different proportions ranged between 196 and 232 mm, and its flowability met the basic principle of pumping. When the C/T of the CPB mixture was increased from 1:12 to 1:4, the backfill changed from a nonuniform structure with sparse pores to a dense network structure with a few holes and pores. The C/T had a significant effect on the quantitative characteristics. With an increased C/T, the porosity and average pore area generally decreased, resulting in a decrease in the porosity and enhanced mechanical characteristics. The C/T of the CPB also influenced the fractal dimension and roundness. When the C/T increased from 1:12 to 1:4, there was a decreasing trend in the fractal dimension and roundness. Additionally, the size difference between the pores decreased, and the pores were round, resulting in increased uniaxial compressive strength of the CPB. The probability entropy values of the backfill with different C/Ts were all greater than 0.93, and the pore distribution had no obvious orientation.