Cement production significantly consumes raw materials and emits greenhouse gases. The cement industry increasingly focuses on mitigating these impacts by integrating eco-friendly supplementary cementitious materials (SCMs) to produce low-carbon cement. Steel slag is gaining attention due to its wide availability among these. The slag presents an opportunity for an alternative binder, aligning with circular economy principles in the construction sector. Specifically, processed ladle furnace slag (LFS), a by-product of steel refining, offers potential for recycling as a newer binder due to its favourable physical and chemical properties, resembling traditional cementitious materials. The present study uses LFS, processed with sodium meta-silicate, to develop a sustainable binder. Two types of binder formulations were prepared, incorporating 0% and 30% processed LFS into ordinary Portland cement (OPC), and their properties, including strength and life cycle assessment (LCA), were evaluated. This work adopted a cradle-to-gate life cycle assessment (LCA) approach. The LCA of formulated binders was executed through SimaPro 9.5.0.1 software. The processed LFS-based binder improves compressive strength by 4.05% with energy savings of 22% over OPC at a 30% replacement level. The CO₂ emissions from the control binder were 245 kg (224 kg from OPC), reduced to 231 kg (55.3 kg from processed LFS) for 30% processed LFS-based composite cement. Moreover, environmental indicators, including ozone depletion, mineral use, land occupation, and climate change, are significantly improved by incorporating processed LFS in the composite cement. These findings underscore the potential of processed LFS as a sustainable resource for developing low-carbon, high-performance cementitious binders.