Flexural Characteristics of Tailings Cemented with Fiber-Reinforced Green Composite Cementitious Matrix

Backfilling mine goafs can significantly advance the mining industry; however, few researchers have used geopolymers reinforced with polypropylene fibers as filling materials. In this study, the flexural properties of fiber-reinforced green composite cementitious matrix-cemented tailings were examined, and the evolution mechanism of the internal structural properties of the prepared composite materials was determined. For this purpose, three-point bending tests, scanning electron microscopy, energy dispersive spectroscopy, and X-ray diffraction were performed on composite samples with different blending ratios, and discrete-element numerical simulations were conducted using PFC3D particle flow simulation software. The obtained results revealed that the flexural strength and fracture properties of the studied samples increased with increasing NaOH content, decreased with increasing water-to-solid ratio, and first increased and then decreased with increasing fiber content. At a fiber content of 0.6%, the reinforcement effect reached a local optimum. The higher the NaOH content, the more efficiently fly ash and slag formed polymerization products in an alkaline environment, which contained tailing sand aggregate particles, increasing the compactness of the composite structure. The fibers in the composite material were distributed both as a single inlay and as a three-dimensional network structure to form an effective wrapping and supporting system, which further improved the flexural performance of the sample. The PFC3D simulation data were consistent with the results of three-point bending tests, illustrating the sample degradation process. The findings of this work can provide a theoretical basis for the development of fiber-reinforced green sand filling materials for mine replenishment.