Workability of geopolymer concrete and mortar materials: a systematic review of influencing parameters and optimization for sustainable construction materials

Workability is one of the most decisive yet least investigated parameters influencing the successful implementation of geopolymer concrete (GPC) and geopolymer mortar (GPM) in sustainable construction. This review provides a systematic and quantitative evaluation of 113 peer-reviewed studies published between 2003 and 2025, highlighting the key chemical and physical parameters that govern fresh-state behaviour. The research identifies the critical influence of activator molarity (1–16 M), water-to-binder ratio (0.30–0.50), and sodium silicate-to-sodium hydroxide ratio (1.5–3.0) on slump flow and viscosity, demonstrating that optimized formulations can achieve slump values of 180–250 mm and compressive strengths above 55 MPa without segregation. By integrating statistical comparisons and sustainability analysis, this work introduces a novel framework that links rheological parameters with carbon footprint, material efficiency, and constructability performance. A comprehensive life cycle assessment (LCA) framework is presented, evaluating multiple environmental impact categories including global warming potential, water consumption, acidification, eutrophication, resource depletion, and toxicity indicators across the full production-to-end-of-life spectrum. Results show that improving flowability through appropriate activator design and superplasticizer dosage (3–7 wt%) can reduce energy consumption during mixing and compaction by 10–20%, while maintaining or enhancing strength and durability. The review further compares application-specific requirements in 3D printing, precast systems, and sewer rehabilitation, where controlled workability ensures structural integrity and rapid placement. Overall, this study establishes a foundation for developing geopolymer-specific workability standards and provides practical guidelines to balance processability, mechanical performance, and environmental benefits for next-generation low-carbon infrastructure.