BAM, Arup and Tarmac trial low-carbon flood defence


The Environment Agency, BAM, Arup and Tarmac have successfully trialled two low carbon concrete mixes for flood defence scheme. 

Hexham flood defence site.
Credit: Bam UK and Ireland.

As part of the Environment Agency’s Collaborative Delivery Framework Hub A, the firms trialled two types of low-carbon concrete mixes as part of the Hexham Flood Alleviation Scheme.

The concrete has been used across three panels totalling 27m of the £6.5 million Hexham flood defences, which comprises of 600m of flood walls and grass embankments. 

Hexham suffered considerable damage from flooding during Storm Desmond in 2015, and the scheme looks to protect around 90 properties from further damage posed by the River Tyne. 

The wider aim of the Environment Agency’s framework looks to deliver sustainable flood defences across North East England.

Low-carbon concrete 

Throughout the scheme’s permanent works, the trial involved the use of: 

  • Portland Limestone Ternary mix, developed by Tarmac, which saved 64% of carbon compared to cement-based concrete. 
  • Alkali Activated Cementitious Material (AACM) which reduced carbon emissions by 70% per cubic metre of concrete. 

Traditional concrete accounts for 7% of global carbon emissions, and the use of low carbon alternatives which retain the durability of traditional concrete looks to set a standard for sustainable concrete products. 

The firms have employed a rigorous testing regime on site to track the durability and suitability of the concrete mixes, with collated data determining its use in future low-carbon solutions. 

The scheme in Hexham is expected to complete in Summer 2023. 

“We are working closely with the Environment Agency, Arup and Tarmac, to ensure the materials can be approved for use and look forward to seeing these being used on more civil engineering schemes in the future,” said Ruth Young, the area carbon and sustainability lead for BAM. 

“We can’t afford to compromise on flood protection, so finding concrete which significantly reduces carbon emissions while maintaining robust defences represents an incredibly important milestone,” said Donald Daly, an associate at Arup. 

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