Comparison of Different Additives and Ages on Mechanical and Acoustic Behavior of Coal Gangue Cemented Composite

Abstract

Cemented backfill represents a significant trend in mine filling methods; however, it often exhibits high brittleness and limited resistance to failure, which can restrict its practical application. This study investigates the mechanical properties and damage evolution of fiber-reinforced coal gangue cemented materials (CGCMs) at various curing times using uniaxial compressive tests, acoustic emission (AE) analysis, and scanning electron microscopy (SEM). Specimens were created with different fillers, including carbon fibers (CFs), steel fibers (SFs), and carbon black (CB), and subjected to uniaxial compression until failure. Control specimens without fillers were also tested for comparison. The microstructure of the specimens was examined using scanning electron microscopy (SEM). The findings indicate that (1) the compressive strength of filler-reinforced CGCMs increases between 7 and 14 days of curing but decreases thereafter, with CB significantly improving early-age strength; (2) specimens reinforced with CFs and SFs exhibit significantly enhanced toughness in their post-cracking response; (3) AE events during specific stages can effectively identify the reinforcing effects of CFs and SFs; (4) the presence of fillers improves resistance to shear cracks, with CFs and SFs being more effective than CB; and (5) adding CB results in a denser and more stable hydration product structure, while CFs and SFs lead to a more porous structure with increased cracking.