Design Solution · Materials Science
Design Solution · Dream about it
Replace part of the cement with GGBS to cut concrete embodied carbon.
Ground granulated blast-furnace slag (GGBS), a by-product of iron-making, partially replaces Portland cement in concrete mixes. Roughly every 10% of GGBS substitution cuts the concrete's embodied-carbon value by about 9%, with a 25% replacement taken as a baseline for in-situ piling, foundations and structure.
Ground granulated blast-furnace slag as a partial Portland cement replacement is one of the most well-evidenced and commercially mature levers for reducing embodied carbon in concrete structures — an industrial by-product of iron-making that reduces clinker content and, with it, the process CO2 that makes cement the largest single embodied-carbon contributor in most buildings. The quantified relationship cited here — approximately 9% embodied-carbon reduction per 10% substitution — is consistent with published industry data and the 25% baseline referenced for in-situ work is a conservative and broadly accepted starting point. This record is at claimed status with no project-specific verification, but the technology itself needs no validation: GGBS concrete is specified routinely in UK and European structural engineering practice. The genuine value for a project pursuing embodied-carbon targets is that GGBS substitution requires no structural redesign, has established guidance (Concrete Centre, UKCA) for mix proportioning, and is commercially available through most readymix suppliers in industrial regions. The constraints to respect are practical: GGBS at higher substitution rates (above 50%) slows strength gain, which affects programme assumptions for striking formwork and loading; very high substitution (70%+) requires careful assessment of sulfate resistance in aggressive ground conditions; and GGBS availability is not uniform — it concentrates near steel-making regions and may be transport-constrained on remote sites. These are manageable engineering variables, not barriers, but they need to be addressed explicitly in the mix-design specification rather than assumed away.
#GGBS #concrete #cement replacement #embodied carbon