A Critical Review of Geopolymer Concrete: Mechanisms, Mix Design Methodologies, and Circular Economy Potentials

Geopolymer concrete (GPC), recognised as a third-generation sustainable binder, presents a transformative alternative to ordinary Portland cement (OPC) by mitigating CO₂ emissions and valorising industrial/agricultural waste. This comprehensive review synthesizes the historical evolution, chemical mechanisms, mix design methodologies, and diverse applications of GPC. Formed through alkali activation of aluminosilicate precursors (e.g., fly ash, slag, metakaolin) below 100°C, GPC exhibits superior mechanical properties, exceptional durability in aggressive environments, and high thermal stability. Despite advances in mix design, which span target strength, performance-based, and statistical approaches, standardization remains a challenge due to precursor variability and curing dependencies. GPC’s circular economy potential is demonstrated through global infrastructural applications (e.g., pavements, precast elements, wastewater treatment) and waste encapsulation. However, barriers such as efflorescence, high activator costs, and longterm data gaps hinder widespread adoption. Future research must prioritize scalable production, lifecycle assessment, and codification to unlock GPC’s full potential as a cornerstone of sustainable construction.