HS2 tunnels could use calcined clay cement

Skanska Costain Strabag joint venture has secured government funding to trial calcined clay as a low-carbon alternative to cement on HS2 London tunnels.The contractor will use the Innovate UK funding to continue developing a replacement for Portland cement with repurposed London clay.

Data from a preliminary trial funded by HS2 showed that calcined London clay excavated from tunnels and other construction activities could be a viable alternative to cement in concrete. Although results from the initial tests suggest that carbon reduction could be considerably reduced, more research is needed. 

SCS JV is working on this HS2 trial with technical lead Arup, concrete supplier Tarmac, the University of Leeds, Sika UK, Expedition Engineering and the Mineral Product Association.

Apostolos Tsoumelekas, SCS JV materials engineering manager who has been developing the product, said: “The clay that is excavated from the HS2 tunnels is essentially a waste product. We have developed a process which calcines the clay and grinds it to a powder, transforming it into a useful resource which can then be added to concrete replacing Portland cement. The results have been impressive and hopefully if it’s scaled up it could really help speed up the adoption of low-carbon concrete for commercial use.”