Beyond embodied carbon: a durability-based lifecycle sustainability framework for low-clinker precast concrete

Reducing the clinker content of cement lowers the embodied carbon of concrete but does not necessarily improve lifecycle sustainability if durability is compromised. This study proposes the Relative Lifecycle Sustainability Composite Index (Relative LCSI), a durability-driven framework that integrates service life, lifecycle greenhouse gas emissions, lifecycle costs, maintenance demand, and infrastructure availability into a unified sustainability assessment. Eighteen concrete systems, representing six baseline mixtures and two durability modification scenarios, combining three clinker contents (97%, 82%, and 62%) and three water-to-cement ratios (0.45, 0.65, and 0.70) were evaluated using literature-calibrated durability parameters under controlled manufacturing conditions. The proposed framework demonstrates that reductions in embodied carbon may be offset by shorter service life and increased maintenance requirements. By explicitly incorporating durability into lifecycle assessment, the Relative LCSI identifies sustainability tradeoffs that cannot be captured using embodied carbon alone and provides a reproducible engineering methodology for evaluating low-carbon concrete technologies and alternative infrastructure sustainability strategies.