Strength and environmental benchmarking of waste-derived activators in fly ash-slag alkali-activated concrete: A systematic and quantitative assessment

Commercial sodium silicate (CSS) remains a widely used activator in alkali-activated concrete (AAC), but its production can substantially contribute to the embodied environmental impacts of AAC. Although waste-derived activators (WDAs) synthesized from silica-rich wastes have received increasing attention, comparative evidence linking their mechanical performance, environmental impacts, eco-efficiency and low-carbon procurement potential remains limited. This study addresses this gap through a quantitative and environmental benchmarking assessment of CSS, sole WDA (SWDA) and hybrid WDA (HWDA) systems used in fly ash-slag AACs. A database of 40 AAC formulations from 20 studies was compiled. Life cycle assessment was combined with dataset-level statistical comparisons, strength-normalized environmental indicators, sustainability ranking, Pareto analysis and procurement-oriented benchmarking to establish an integrated framework for evaluating WDA technologies. The compiled WDA formulations achieved compressive strengths comparable to CSS formulations, indicating that selected waste-derived systems can achieve compressive strengths within the investigated structural-grade range. Simultaneously, the WDA systems reduced average global warming potential (GWP) by approximately 34% relative to CSS (95% CI: 19–49%) and exhibited lower GWP per unit compressive strength. Activator production remained the dominant environmental hotspot, contributing 75–82% of total GWP. Thermochemically synthesized waste glass (WGP-TMC) activators exhibited favorable strength-GWP trade-offs within the defined assessment framework, with the identified Pareto frontier consisting exclusively of SWDA formulations. Furthermore, several SWDA and HWDA formulations attained Market Beating embodied carbon classifications under the Low Carbon Concrete Group framework. The findings therefore indicate that selected WDA systems, especially WGP-TMC-based formulations, have promising potential for lower-carbon AAC production.