Study on the influence of coal-based solid waste on performance optimization of roadway pavement concrete

Traditional concrete materials are expensive and ecologically detrimental, presenting significant challenges in balancing construction cost control with durability requirements for underground roads. To enable near-site, high-value utilization of bulk coal-based solid waste while optimizing coal mine roadway concrete performance, a fly ash-coal gangue concrete is developed in this study. In this material, natural crushed stone aggregates are substituted with coal gangue and cement is replaced with fly ash. Using coal gangue replacement rates (0%, 20%, 40%, 60%, 80%, 100%) and fly ash content (0%, 10%, 20%) as experimental variables, fresh concrete workability was assessed via slump tests; Strength characteristics and drying shrinkage behavior of hardened concrete were evaluated through compressive and flexural strength testing; Pore structure characteristics were analyzed using nuclear magnetic resonance (NMR); The optimization effect of triethanolamine dosages (0%, 0.01%, 0.03%, 0.05%) on drying shrinkage and mechanical properties was investigated in high-fly-ash-content concrete. The results demonstrate that concrete slump is significantly reduced by coal gangue content exceeding 40%, whereas workability is enhanced by appropriate fly ash addition; Concrete strength is diminished by elevated coal gangue content, necessitating a maximum dosage of 40%; Concrete compactness is improved and pore structure is refined by 10% fly ash content, while pore structure integrity is degraded by 20% fly ash; Drying shrinkage is increased by coal gangue but effectively mitigated by fly ash incorporation; Both drying shrinkage resistance and mechanical strength of fly ash-coal gangue concrete are substantially optimized by adding 0.03% triethanolamine.