Life cycle-based sustainability assessment of optimized 3D printable concrete mixes incorporating SCMs and recycled aggregates

• Optimized SCM–RFA 3DPC cuts GWP by ∼32% at cradle‑to‑gate. • Tri‑SCM blend (FA+GGBS+SF) retains printability and strength. • CED falls ∼30%; fossil and mineral scarcity drop ∼30–33%. • Proxy-driven toxicity trade‑offs flagged for data refinement. • Method couples mix optimization with multi‑method LCA. Ordinary Portland cement (OPC) in 3D-printable concrete (3DPC) has a high embodied-carbon burden. While SCMs and recycled fine aggregates (RFA) hold promise, the mix optimisation to make it extrusion-friendly has scarcely been quantified under cradle-to-gate life-cycle assessment (LCA). This research establishes that gap and compares an optimised SCM–RFA 3DPC (fly ash, GGBS, silica fume; with polypropylene fibres) to an OPC reference point m ixes met printability and mechanical specifications; environment was modelled in openLCA 2.4.1 with CML-IA (Baseline/Non-Baseline), ReCiPe 2016 Midpoint (H), Cumulative Energy Demand (CED) and Crustal Scarcity Indicator. Optimisation reduced important burdens compared to reference: Global Warming Potential by 32.15% (3252.02 → 2206.37 kg CO₂-eq), Abiotic Depletion (fossil fuel) by 30.46%, Acidification by 17.94%, and CED by 30.49% (38,062.75 → 26,456.32 MJ). Trade-offs were found with some ecotoxicity indicators, due to proxy inventory selection for by-products and recycled sources, and are explained with corresponding sensitivity analyses. In total, including SCMs and RFA in extrusion-compatible 3DPC achieves considerable climate and energetic advantages at cradle-to-gate, with areas of toxicity categories identified to set research agendas on dataset refinement and future durability-inclusive LCAs.