Hierarchical Nanoengineered Matrix and Fiber Reinforcement for Sustainable Coal Mine Waste Rock Concrete

The large-scale application of coal mine waste rock (CMWR) in concrete is limited by a porous interfacial transition zone (ITZ), which reduces mechanical performance and accelerates fluid transport. This study introduces a hierarchical reinforcement approach that combines nano-silica (NS)-induced matrix densification with basalt fiber (BF) bridging. NS refines the pore structure and strengthens the ITZ, creating a low-permeability matrix that enables effective fiber anchorage and crack arrest. The hybrid mixture containing 0.5% NS and 4% BF achieved a 30.5% higher compressive strength, a 26.0% greater flexural strength, and a 41.5% reduction in water absorption compared to the control. These findings demonstrate that nanoscale matrix densification is crucial for activating microscale fiber reinforcement, providing a viable route to developing waste-based cementitious composites with enhanced resistance to fluid ingress and improved transport properties.