HS2 JV trials calcinated clay as low carbon alternative to cement

The HS2 Skanska Costain Strabag joint venture has secured funding to trial modified “waste” London Clay as a low carbon alternative to cement

The JV is working with Arup, Tarmac, the University of Leeds and Sika UK along with Expedition Engineering and the Mineral Product Association on the trial funded by Innovate UK to help accelerate the decarbonisation of the concrete industry.

The trial involves using “calcinated” London Clay, excavated from the tunnel activities, as a replacement for Portland Cement in concrete for the HS2 permanent works.

Calcinating involves heating to temperatures in excess of 600°C which breaks down some of the minerals and changes the structure, making the clay more reactive.

Potentially calcined clays can improve the durability, strength, and performance of concrete, while increasing resistance to chemical attacks and reducing permeability.

Apostolos Tsoumelekas, Skanska’s Materials Engineering Manager who has been heavily involved in developing the product said, “This innovation was first sparked by a discussion with an expert in Arup who had been researching the applications of calcined clays in concrete. Working together with our customer and the supply chain we have been able to help turn this idea into reality.

“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.”