Abstract:

In order to control the construction cost of roadway pavement in the mine and realize the near-in-situ high-value utilization of bulk coal-based solid waste, the concrete material of roadway pavement with fly ash and coal gangue to replace cement and natural gravel aggregate of equal quality was developed in this study. Firstly, the working performance of the freshly mixed concrete was evaluated by the slump experiment. Then, the mechanical properties and volume stability of hardened concrete were studied by compressive strength, flexural strength, and drying shrinkage tests. Finally, the pore structure characteristics of the concrete were analyzed by NMR technology. The experimental results show that the slump is significantly reduced when the coal gangue content exceeds 40%, and the appropriate amount of fly ash can improve the fluidity, but part of the strength decreases. 10% fly ash can enhance the compactness of concrete, while 20% content will deteriorate the pore structure. The NMR results reveal the significant effect of fly ash content on micropores. Coal gangue increases drying shrinkage, but fly ash and an appropriate amount of triethanolamine (TEA) (the optimal content is 0.03%) can effectively optimize its drying shrinkage resistance.

Key words: coal gangue, fly ash, nuclear magnetic resonance (NMR), mechanical property, drying shrinkage