1 School of Architecture and Civil Engineering, Xi'an University of Science and Technology, Xi'an 710054, China 2 State Key Laboratory of Green Building in Western China, Xi'an University of Architecture and Technology, Xi'an 710055, China 3 School of Civil Engineering, Xi'an University of Architecture and Technology, Xi'an 710055, China
Abstract: In this study, high-temperature microwave radiation was used to stimulate the potential activity of coal gangue powder, so that it could be used as an admixture in cement-based materials. The temperature of coal gangue powder was measured by infrared thermometer. Further, laser particle size analysis, XRD and SEM were used to characterize the mineral composition and microscopic morphology of activated coal gangue powder. The flowability and mechanical properties of unactivated and activated coal gangue mortar were compared and analyzed, and the hydration mechanism of activated coal gangue powder was studied. The results showed that after microwave heating, the particle size of coal gangue powder decreased as a whole, and the particles were rounded and uniform. In addition, the high temperature of the microwave caused the structure of coal gangue loose and porous, the required free water added, and the flowability of mortar reduced. When the microwave tempe-rature was 500—600 ℃ and the content of coal gangue powder was 10%, 20% and 30%, the 28 d compressive strength of the specimen was 46.5%, 37.9% and 51.1% higher than that of the unactivated group, respectively. The C-S-H and C-A-S-H gels with good hydration activity were formed on the surface of coal gangue powder in the active coal gangue slurry, which played a pozzolanic effect, while the unreacted coal gangue powder was filled in the gap of the slurry, thus improving the mechanical properties of the mortar.
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