Abstract: Taking the desulfurized gypsum and the analytical reagent CaO as activator, Beijing Fangshan coal gangues are activated by three ways, and then the strength of cementitious materials with the activated coal gangue in different ways are detected and analyzed to study the effect of activator and mixed grinding on the thermal alteration and activation of test materials.The microscopic properties before and after the activation of coal gangue are characterized by the X-ray diffraction; the cementitious activity of cementitious materials with coal gangues are characterized by the mortar strength analysis and scanning electron microscopy (SEM).The results showed that the main activity of coal gangue sources from the clay minerals.And the kaolinite and chlorite in coal gangue are dehydrated and broken down at 700 ℃ calcined to generate the amorphous SiO₂ and Al₂O₃ which occurs the solid state reaction with CaO.In wet mixing process, the reaction is finished, and then two hydraulic active substances C₁₂A₇ and C₂S are generated, both of which own a high cementitious activity.

Key words: Coal gangues, Thermal alteration, Cementitious activity