Study on freeze-thaw damage mechanism of coal gangue-based concrete

Coal gangue is a hazardous solid waste associated with the coal production process that is rich in silica and aluminum phase and has potential cementing properties. To promote the application of activated coal gangue materials in concrete engineering in cold regions, this paper uses mechanical grinding and microwave irradiation to active the coal gangue powder. The time-dependent evolution law of the macroscopic properties of concrete under freeze-thaw cycles (FTCs) was used as indicators to study the frost resistance of CGBC (coal gangue-based concrete) with mass substitution rates of 0%, 10%, 20%, and 30%. The damage mechanism of CGBC under FTCs was also revealed. The results show that activated coal gangue powder (ACGP) can enhance the frost resistance of concrete. The 10% and 20% content of ACGP significantly increased the compressive strength, splitting tensile strength. Microscopic experimental results show that the filling effect and secondary hydration of ACGP can improve the pore structure of concrete by refining harmful macropores and reducing pore connectivity to the greatest extent, and can also reduce the thickness and enhance the microhardness of the interfacial transition zone (ITZ).