Industry reports document a surge in cement production in recent years, reaching 4.1 billion tonnes in 2022 and resulting in significant environmental burdens. While conventional supplementary cementitious materials often fail to meet construction demands, limestone calcined clay cements (LC³) offer a promising alternative, reducing reliance on traditional raw materials while using abundant resources. This study evaluates the sustainability potential of strain-hardening cementitious composites based on LC³ binders incorporating dispersed non-metallic synthetic fibers. A cradle-to-gate life cycle assessment in combination with an extended life cycle sustainable cost analysis was used to compare three clinker-to-binder weight ratios (50%, 35% and 25%) and three types of synthetic fiber: polypropylene, polyethylene terephthalate and ultra-high molecular weight polyethylene. This analysis also considers monetized environmental externalities. A mechanical performance indicator (work-to-fracture) was prioritized as the functional unit to meet the needs of engineering practice. This integrated framework revealed trade-offs and opportunities in material selection and optimization.