Calcined Coal Gangue Fines as the Substitute for Slag in the Production of Alkali-Activated Cements and Its Mechanism

Nowadays, upcycling coal gangue into aggregates has become a popular method; nevertheless, the utilization of coal gangue fines (CGFs), a secondary waste generated during the production of coal gangue aggregates, is rarely concerned. This paper attempted to upcycle calcined CGFs at 800 degrees C as the partial substitution of slag to prepare alkali-activated cement (AAC). The variation in macroscopic compressive strength of AAC was studied, and the hydration mechanism of AAC was explored in depth by microstructure. AAC with CGFs shows tremendous advantages in compressive strength and hydration products. In the 10% calcined CGF content, the 3 d, 7 d, and 28 d compressive strengths of AAC displayed pronounced increases of 8%, 25%, and 13%, respectively. The study results showed that CGFs could replace the small amount of slag in AAC while providing a new theoretical guide and technical support for upcycling CGF into helpful material.