High-capacity utilization of coal gangue as supplementary cementitious material, geopolymer, and aggregate: A review.

During coal preparation, a substantial volume of coal gangue (CG) is generated, leading to severe environmental and health concerns stemming from its massive accumulation. Comprehensive research has been conducted on the utilization of CG in various engineering applications. Transforming it into supplementary cementitious material (SCM), geopolymer, and concrete aggregate holds pivotal significance in engineering applications, aligning with the imperatives of sustainable development. However, there are notable deficiencies in current research related to the grading, categorization, and standardization of CG for its optimal utilization based on its basic properties, which need to be addressed for further study and development. This paper takes the mineral composition of CG as a starting point, delving into an analysis of physical and chemical characteristics determined by the composition. Based on these characteristics, the effects of five main activation methods including mechanical, chemical, thermal, microwave, and composite treatments are comprehensively reviewed with a focus on their interaction mechanisms with CG. Subsequently, the fresh properties, mechanical properties, and durability of cementitious materials and aggregates prepared by CG were summarized and analyzed. Research suggests that contingent upon the degree and purpose of treatment (activation), CG can be applied in SCM (partially replacing cement), geopolymer (completely replacing cement), and concrete aggregate, with distinct treatment conditions influencing its engineering characteristics. This paper offers a systematic perspective and insights into the high-capacity utilization and value-added applications of CG. It highlights the issues encountered in the utilization of CG while further providing novel perspectives for its scaled utilization in engineering. [Display omitted] • Utilization of coal gangue in engineering is an ecological and sustainable way. • The pretreatment intensity varies across different utilization methods. • Progressed coal gangue exhibits excellent engineering utilization effect. • Numerous issues were identified, and some suggestions were proposed. [ABSTRACT FROM AUTHOR]