New low-carbon concrete mixes with biochar and calcined clay enter the market

Concrete makers are moving low-carbon mixes from labs to real projects. Holcim has started using biochar made from forestry waste and coffee grounds in test pours with Canary Wharf Group, producing what they call net-zero concrete. The company says biochar is no longer a niche additive but a high-performance material that can cut emissions while keeping strength. Calcined clay is also being scaled as a replacement for scarce materials like fly ash, halving cement's CO2 footprint. Researchers are also testing desert sand mixed with wood particles to create Botanical Sand Concrete, or Sandcrete. The lignin in the wood acts as a natural binder, avoiding cement hydration. Early results show it is strong enough for paving stones, but further work is needed to test cold weather performance and to solve the transport problem of shipping desert sand long distances. Both approaches show that construction materials are shifting toward lower carbon footprints, but scaling and logistics remain open questions.