A performance‑driven framework for designing low‑carbon binders for self‑compacting concrete

Self-compacting concrete (SCC) combines high flowability with good mechanical performance, but achieving this typically requires high binder contents, increasing its environmental footprint. This study investigates the design of low-clinker self-compacting mortars (SC-Mortars) in which limestone filler (LF) and waste glass powder (GP) partially replace Portland cement in a ternary binder system. A Central Composite Design (CCD) combined with Response Surface Methodology (RSM) was used to quantify the influence of the water-to-cement ratio, water-to-powder volumetric ratio, superplasticizer-to-powder ratio, and GP-to-cement ratio on fresh-state behavior, mechanical performance, and environmental impact. Flowability, compressive and flexural strengths at 28 and 90 days, drying shrinkage, and electrical resistivity were evaluated. Environmental performance was assessed using Global Warming Potential (GWP), Embodied Carbon Index, and Cement Strength Contribution Index. Across the design space, cement replacement levels of 27–51% produced stable fresh-state behavior and compressive strengths of 41–62 MPa. Six optimized mixtures were experimentally validated, achieving cement replacement levels of 52.2–56.7% while retaining 28-day compressive strengths of 37.6–43.9 MPa (41.6–48.4 MPa at 90 days). These mixtures reduced GWP by up to 44% (262–284 kg CO₂/m³) relative to the standard cement mortar (470.5 kg CO₂/m³), while meeting the target fresh-state criteria. The proposed framework allows mixture proportions to be selected directly from performance targets rather than by trial and error, balancing fresh-state, mechanical, and environmental requirements at the design stage. By linking mixture design, statistical modeling, and microstructural observations, this study provides a quantitative basis for transferring mortar-scale optimization toward SCC applications.