Low-carbon cementitious materials are a family of hydracementitioulics binders and concrete constituents formulated to reduce the embodied carbon dioxideor selected to reduce greenhouse-gas emissions assexpressed as CO₂-equivalent associated with cement and concrete production, relative to ordinary Portland cement (OPC)a specified conventional baseline, while retainproviding the binding functionperformance required for structural concrete their intended applications ^[1]. Emission reductions iscan be achieved primarily by lowering the Portland-clinker fraction through partial replacement with supplementary cementitious materials, such as fly ash, ground granulated blast-furnace slag, silica fume, metakaolin, and calcined clay, or by substitutiusing alternative binder chemistries —, including alkali-activated binders, calcium sulfoaluminate cements, belite-rich cements, and magnesium-based cements — that, which may require lower calcination temperatures or avoidreduce reliance on limestone decarbocalcination ^[2]. Because Oconventional PCortland cement production emits CO2 bothgenerates greenhouse-gas emissions from thboth the calcination of calcium carbonate and from fuel combustion in the kilduring clinker production, the “low-carbon” designation is defined by a reduction in life-cycle performance of a cementitious material is generally assessed by comparing greenhouse-gas emissions per unit of binder, rather than by a single fixedwith those of an appropriate baseline, using a defined system boundary and functional unit ^[3][4][5]. Such comparisosition or ns should also consider equivalent performance requirements, including strength class, durability, and ^[3]. Thexpe category is distinguished from conventional blendedted service life, to ensure that emission reductions are evaluated on a functionally comparable basis. Low-carbon cements by the magnitude ofitious materials therefore do not correspond to a single composition, clinker -substitution and by explicit targeting of embodiedlevel, or strength class, and conventional blended cements may also be considered low-carbon rewhen they demonstrate a meaningful reductionn in greenhouse-gas emissions relative to an appropriate reference system.