A comprehensive review on coal gangue aggregate concrete: from raw material to structural behaviors

Abstract Coal gangue (CG), a massive by-product of coal mining, presents both environmental challenges and opportunities as a sustainable alternative to natural aggregates in concrete. However, its high porosity, variable composition, and inferior properties often limit the performance of coal gangue aggregate concrete (CGAC). This review provides a comprehensive and systematic analysis of recent advances in CGAC research, with a clear aim to bridge the gap between material characteristics and structural applications, covering the physicochemical properties of CG, mechanical behavior, durability issues, modification strategies, structural performance, and life cycle assessment. Key findings indicate that while raw CG aggregates generally reduce concrete strength and durability—especially in high-grade mixes—effective improvements can be achieved through matrix modification (e.g., fly ash, fibers, nano‑SiO₂) and aggregate treatment (e.g., calcination, coating). Structurally, CGAC in composite systems such as concrete-filled steel tubes retains over 95% stiffness even at full aggregate replacement. Life cycle assessment studies confirm that using CG sand in concrete can lower costs by 25%–30% and carbon footprint by 18%–22%, provided transport distances are optimized. The study concludes that CGAC represents a viable, eco-friendly construction material that supports waste valorization and resource conservation. Future efforts should focus on standardizing durability evaluation, advancing high-value applications, and promoting its integration into industrial practice.