Synergies between coal-gangue activation and LC3 systems: From raw-material characteristics to durability

The resource utilization of coal gangue provides substantial environmental benefits by reducing pollution, conserving natural resources, and supporting "dual carbon" goals and sustainable development. Limestone Calcined Clay Cement (LC3) has emerged as a promising low-carbon alternative to ordinary Portland cement, enabling up to 50% clinker reduction while achieving comparable performance. Activated coal gangue, an abundant industrial solid waste with latent pozzolanic activity, serves as a cost-effective supplementary cementitious material (SCM) that can effectively substitute calcined clay in LC3 systems, simultaneously addressing waste management challenges and sustainable construction demands. However, systematic studies on its activation mechanisms, compatibility with LC3, and long-term durability remain limited. This review synthesizes recent advances in the synergistic incorporation of activated coal gangue into LC3 binders, emphasizing applicability, hydration mechanisms, and performance characteristics. Particular focus is placed on the cooperative formation of C-A-S-H gels and calcium carboaluminate phases, which refine pore structure and improve durability. The influence of various activation methods (thermal, mechanical, chemical, and combined) on reactivity, mechanical properties, and long-term performance is critically evaluated. This work offers theoretical foundations and practical guidance for designing coal gangue-based low-carbon cements, thereby facilitating solid waste valorization and advancing sustainable construction practices. • The study highlights the role of C-A-S-H and calcium carboaluminate phases in coal gangue-based LC3 systems. • The study provides insights into activation mechanisms and performance of coal gangue-based low-carbon cement. • Coal gangue can serve as a low-cost alternative in the LC3 system and support sustainable development.