Low-carbon cementitious materials are a family of hydraulicementitious binders and concrete constituents formulated or selected to reduce greenhouse-gasto reduce the embodied carbon dioxide emissions expressed as CO₂-equivalent assassociated with cement and concrete production, relative to a specified conventional baselineordinary Portland cement (OPC), while providretaining the binding performancefunction required for their intended applications structural concrete ^[1]. Emission reduction is can be aachieved 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 usisubstituting alternative binder chemistries, including — alkali-activated binders, calcium sulfoaluminate cements, belite-rich cements, and magnesium-based cements, which may — that require lower calcination temperatures or reduce reliance onavoid limestone calcidecarbonation ^[2]. Because conventional OPortland cementC production generates greenhouse-gas emissionsemits CO2 both from both ththe calcination of calcium carbonate and from fuel combustion during clinker productioin the kiln, the “low-carbon performance of a cementitious material is generally assessed by comparing” designation is defined by a reduction in life-cycle greenhouse-gas emissions with those of an appropriate baseline, using a defined system boundary and functionalper unit of binder, rather than by a single fixed composition or strength class unit ^[3][4][5]. SucTh comparisons should also consider equivalent performance requirements, including strength, durability, and expected service life, to ensure that emission reductions are evaluated on a functionally comparable basis. Low-carbone category is distinguished from conventional blended cementitious materials therefore do not correspond to a single composition,s by the magnitude of clinker- substitution level, or strength class, and conventional blended cements may also be considered lowand by explicit targeting of embodied-carbon when they demonstrate a meaningful rereduction in greenhouse-gas emissions relative to an appropriate reference systemn.