Multi-scale influence mechanism of fine coal gangue on the mechanical properties of concrete

The aim of this study is to explore the feasibility of coal gangue (CG) fine aggregate replacing natural sand, and realize the resource utilization of solid waste in concrete materials. The coal gangue concrete (CGC) is prepared with the CG replacement of 0%, 5%, 10%, 15%, 20%, 50% and 100%, the influence of CG replacement on the slump, bulk density, compressive strength and pore structure of concrete is analyzed, and the influence mechanism is revealed combining with the scanning electron microscope (SEM), nuclear magnetic resonance (NMR) and X-ray diffractometer (XRD). The results shows that the optimal mechanical property is achieved with 10% CG replacement, which is 10.1% higher than that of the ordinary concrete. The influence mechanism is that it accelerates the hydration reaction of cement, improves the interfacial transition zone (ITZ), increases the harmless pores percentage and reduces the more harmful pores percentage. The research provides theoretical support for the high value utilization of solid waste in mining area.