Using concrete containing calcined clay to lower the carbon footprint of construction projects

Product: Concrete containing calcined clay

Main contractor: Sir Robert McAlpine

Specialist contractor: Getjar Limited

Overview 

Heidelberg Materials UK has worked in close collaboration with Getjar Limited and Sir Robert McAlpine to supply concrete containing calcined clay to reduce the carbon footprint of the new London Museum in Smithfield as well as a separate project with BAM near Liverpool Street.

Project description

Calcined clay is a supplementary cementitious material (SCM) that can be used to replace some of the CEMI within concrete reducing its carbon footprint. It is a type of clay that has been heated to a high temperature activating its pozzolanic properties, which allows it to react like a cement.

The London-based projects used C32/40 and C40/50 concretes containing 30 per cent calcined clay supplied by Heidelberg Materials’ Greenwich concrete plant.

The material has been used to create a permanent reinforced concrete beam at the new London Museum in Smithfield, where a number of historic buildings are being remodelled.

London Museum has strong sustainability goals and collaboration between Sir Robert McAlpine, Getjar and Heidelberg Materials UK led to the development of a lower carbon concrete containing calcined clay, which was discussed, developed and placed in just over two weeks.

To achieve targets relating to circularity, the concrete supplied to London Museum also incorporated recycled crushed concrete aggregates (CCA), reducing reliance on primary aggregate and supporting the circular economy.

“This is a great example of the speed at which new innovative solutions can be implemented through supply chain collaboration,” said Simon Leek, Company Carbon Manager, Sir Robert McAlpine Ltd.

The second project is Broadgate Tower, a newly redesigned commercial space in the heart of the City of London, refurbished by BAM for British Land. Here, concrete containing calcined clay has been used to cast slabs on an exposed roof area on the 34th floor which houses utilities such as ventilation equipment.

Daniel Clayton, Concrete Technical Director at Heidelberg Materials UK, added: “Feedback from both projects proves that concrete containing calcined clay provides excellent consistency and compaction, with no delays in striking times.

“Subsequent laboratory trials have also shown that replacing up to 30 per cent of 
Portland cement content with calcined clay achieves strengths equivalent to GGBS at 28-days.”

Lowest carbon concretes
Heidelberg Materials offers a wide range of SCMs, including a secure supply of GGBS to achieve the lowest carbon concrete possible. The company’s Greenwich plant is able to supply the full range including evoBuild or evoZero CEMI, calcined clay, GGBS, limestone filler, carbon cure technology as well as recycled CCA. The site also operates as an evoHub venue, providing customers with a lower carbon supply point and training facility.

For more information about calcined clay or other SCMs, please contact our concrete technical team.