Abstract：In this study, coal gangue was calcined under various conditions (temperatures of 500 ℃, 600 ℃, 700 ℃; durations of 10 min, 30 min, 50 min) using microwave and conventional methods to enhance the activity of coal gangue and investigated its activation mechanism. The mineral phase transformations and structural changes of coal gangue at activation temperatures were analyzed through X-ray diffractometry (XRD), Fourier Transform Infrared Spectroscopy (FTIR) and activity index experiments within the temperature range of 500 ℃ to 700 ℃. Cement paste was prepared by adding 30% activated coal gangue auxiliary cementitious material, and its mechanical properties were tested. Experimental findings showed that kaolinite in the coal gangue was gradually transformed into metakaolinite with increasing activation temperature. The 7 d compressive strength of gangue-cement paste activated at microwave 700 ℃ for 50 min as auxiliary cementitious material reached the highest, which increased by 23.63% compared with that of unactivated gangue-cement paste. This improvement can be attributed to amorphous SiO2 and Al2O3 present in activated coal gangue reacting with Ca(OH)2 produced during cement hydration process to form C-S-H, which enhances densification within cementitious materials thereby improving mechanical properties.
2025, Vol. 0 
