Color Transition and Its Quantitative Characterization of Active Powder Material Prepared from Granular Coal Gangue

The coal gangue (CG) can be prepared into active mixture material after it was calcined at suitable temperature and then ground. However, due to the complex composition of CG, its color changed greatly after it was calcined. The application of large amount of calcined coal gangue (CCG) in cement-based materials will affect the color of cement-based materials. It is of great significance for the application of CG in cement industry if CCG active powder material with small color difference from cement-based materials can be prepared. In this paper, the influence of preparation process on the color of CCG active powder material was explored; the color of CCG active powder materials was quantitatively characterized and evaluated based on Red, Green, Blue value in PS software; the mechanism of color transition of active powder materials prepared from granular coal gangue was analyzed. The results showed that, during the thermal activation, the redder the color of CCG active powder materials and the higher their Red value were beneficial to the smaller of CG, the longer the holding time of thermal activation and the more sufficient the oxygen in the calcination environment. The oxidation degree of carbon and siderite in CG was the main reason that affects the color of CCG active powder materials. When the black carbon was removed sufficiently and siderite was oxidized to hematite, the color of the material was red, but when carbon was not removed sufficiently and siderite was oxidized to magnetite, the color of the material was black. © 2020, Materials Review Magazine. All right reserved.