Chryso–Ecocem low‑carbon cement system: mix design notes for concrete engineers
Reviewed by Tom Sullivan

First reported on The Construction Index
30 Second Briefing
Saint-Gobain’s Chryso and Ecocem have launched a combined low‑carbon system pairing Ecocem ACT cement, which cuts cement emissions by up to 70%, with Chryso’s new superplasticiser EnviroMix 3150 ACT, formulated for this binder chemistry. The admixture–cement combination enables concrete mix designs achieving over 50% carbon footprint reduction, meeting GWR5 and above, while maintaining high flowability, low viscosity at low water–cement ratios, and workability retention beyond 90 minutes without segregation. On the former John Lewis HQ refurbishment in London, around 1,300 m³ of C20/25 and C30/37 ACT concrete is being pumped using EnviroMix 3150 ACT to validate performance under site conditions.
Technical Brief
- EnviroMix 3150 ACT is tailored to the specific binder chemistry of Ecocem’s reduced‑clinker ACT cement.
- The admixture is designed to maintain durability performance despite the altered hydration profile of low‑clinker systems.
- Robustness against water-content variation is a key design criterion, targeting consistent rheology under site batching tolerances.
- EnviroMix 3150 ACT extends Chryso’s EnviroMix range, which has been broadened to match evolving cement chemistries.
- Nearly 1,300 m³ of ACT concrete will be placed on the former John Lewis HQ refurbishment by year‑end.
- Two strength classes, C20/25 and C30/37, have been specifically developed around the ACT–EnviroMix 3150 ACT combination.
Our Take
Ecocem ACT has already been used on a UK infrastructure scheme by Murphy (our 15 April 2026 coverage), so its deployment on the former John Lewis headquarters signals a move from trial pours into mainstream commercial building work in London.
A claimed 50%+ carbon footprint reduction at C20/25–C30/37 strength classes is significant for UK clients because it aligns with typical concrete grades in commercial refurbishments, making it easier to decarbonise without redesigning structural frames.
Among recent Materials pieces tagged to Sustainability, there are only a handful involving London building projects, so this John Lewis headquarters reuse with low‑carbon mixes may become a reference case for other city-centre retrofit schemes in the UK.
Prepared by collating external sources, AI-assisted tools, and Geomechanics.io’s proprietary mining database, then reviewed for technical accuracy & edited by our geotechnical team.
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