Beyond carbon: An integrated LCA–MCDA framework for circularity measurement of ordinary and geopolymer concrete

Abstract

In recent years, circular approaches to concrete production have gained increasing attention, yet comparative evaluations between different circular concrete types remain limited and inconsistent. In this context, previous comparative studies between circular ordinary concrete (COC) and circular geopolymer concrete (CGC) have been hindered by biases, including a narrow focus on carbon emissions, neglect of service life differences, and inconsistent compressive strength (CS) comparisons. This study presents a novel integrated framework that combines life cycle assessment (LCA), circular economy strategies, and multi-criteria decision analysis (MCDA) to robustly evaluate the sustainability of COC and CGC across six CS ranges. The case study is based in Tehran, reflecting local material availability, environmental conditions, and priorities, influencing mixture designs and MCDA weightings. This underscores the necessity of region-specific approaches in sustainability assessments. Accordingly, circular mixtures were optimized using response surface methodology (RSM), service life was incorporated via the fib model, and a cradle-to-cradle LCA was performed. MCDA, informed by local expert opinions, prioritized environmental indicators. Results demonstrate that CGC consistently outperforms COC across all examined CS ranges (23–41 MPa), with its sustainability performance improving at higher CS. This advantage is attributed to CGC's lower sensitivity to CS-related environmental burdens and substantially longer service life. Moreover, circularity metrics confirm the benefits of circular designs over linear alternatives, with resource inflow circularity rates of approximately 88 % for COC and 71 % for CGC. This research provides a comprehensive decision-making tool by emphasizing the need for holistic and context-specific assessments to advance circularity in the concrete construction industry.