Preparation of high-activity mineral powder from coal gangue through thermal and chemical activation

Abstract This study focuses on enhancing the cementitious activity of coal gangue through a two-step process involving thermal activation followed by chemical alkali excitation. The coal gangue was first treated via a self-heating sintering decarbonization process, which effectively increased its reactivity without the need for additional solid fuel. Following thermal activation, chemical activation was performed using activators such as hydrated lime and lithium silicate to further improve the reactivity of the decarbonized coal gangue. The effectiveness of combining ground granulated blast furnace slag (GGBS) with the activated coal gangue was also evaluated. Results revealed that incorporating 35–45 % GGBS with activated coal gangue significantly enhanced both early and long-term strength, achieving an activity index exceeding 100 % under optimal conditions. The addition of 5 % hydrated lime significantly increased the 28-day activity index of the mineral powder to 82.7 %. Optimization experiments showed that reducing the content of decarbonized coal gangue and fine-tuning the proportions of activators further enhanced the overall activity index, reaching up to 103.7 %. This study provides a comprehensive approach to improving the resource utilization of coal gangue through integrated thermal and chemical activation, paving the way for its application in sustainable construction materials.