Evaluating the Sustainability of Ultra-high-performance Concrete Mixes: A Multi-criteria Life Cycle Assessment Incorporating Embodied Carbon and Energy

Ultra-high performance concrete (UHPC) represents a modern class of cementitious materials characterized by superior strength and durability. However, its comparatively high embodied carbon and energy, relative to normal concrete (NC), pose significant sustainability challenges. This study presents a comprehensive evaluation of 40 UHPC mixes through an integrated life cycle assessment (LCA), incorporating embodied carbon (EC), embodied energy (EE), and compressive strength (CS). The assessment includes raw material product stage (A1–A3), transportation (A4), and maintenance (B2–B5) stages. Both local and global material sourcing scenarios are examined. Findings show that UHPC produced locally in Saudi Arabia exhibits 3.28% to 8.21% higher embodied carbon and 1.33% to 4.34% higher embodied energy compared to global equivalents, highlighting the need for optimization in regional production practices. To evaluate sustainability from a performance-based perspective, an eco-strength index (ESI) is employed, capturing the trade-off between EC and compressive strength. The ESI values range from 7.3 to 14.9 kg·CO2/MPa. A case study involving a single-girder bridge constructed with both UHPC and NC demonstrates that, although UHPC exhibits higher impact per cubic meter, its superior mechanical performance enables material reduction, which in turn results in lower total emissions per meter of bridge length. These results emphasize that when structural efficiency is factored in, UHPC can offer a sustainable solution for high-performance infrastructure applications.