A comprehensive review of agro waste derived geopolymer concrete for sustainable construction focusing on strength durability and microstructural development

The utilization of agricultural residues as precursors in geopolymer concrete represents a promising strategy toward sustainable and low-carbon construction. This review critically synthesizes two decades of research on agro-waste ashes—such as rice husk ash, sugarcane bagasse ash, wheat and millet husk ash, wood ash, and teff straw ash—focusing on their chemical reactivity, mechanical performance, and environmental benefits. Rich in amorphous silica and alumina, these ashes actively participate in alkali activation, forming dense N–A–S–H and C–(A)–S–H gel networks that enhance matrix integrity. Experimental findings indicate that incorporating 10–30% agro-ash can increase compressive, flexural, and tensile strengths by 10–25%, while improving resistance to chloride ingress and water absorption by 15–35%. Microstructural analyses consistently reveal refined pore structures and homogeneous gel formation, particularly in systems utilizing silica-rich rice husk and sugarcane bagasse ashes. Beyond performance gains, life-cycle assessments show potential CO₂ emission reductions of 40–70% compared to ordinary Portland cement. Despite these advantages, large-scale adoption remains constrained by inconsistent feedstock quality, lack of standardization, and limited field validation. The review concludes by identifying research priorities centred on standardized characterization, ambient-curing formulations, low-cost activators, and comprehensive techno-economic analyses to advance agro-ash-based geopolymers toward commercial application.