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Specified for reduced embodied carbon, the new concrete formula was used across three panels, totalling 27 metres, of the £6.5m Hexham flood defence scheme.
The trial involved the first use in permanent works of a new Portland limestone ternary mix developed by Tarmac, which has delivered carbon savings of 64% compared to traditional cement-based concrete, it is claimed. Also tested was an alkali activated cementitious material (AACM) that is said to have reduced carbon emissions by 70%.
While traditional concrete production contributes an estimated 7% of global carbon emissions, in the UK that figure comes down to 1.5% because of progress here with lower carbon mixes, domestic concrete suppliers claim.
The Hexham flood defence trials have been delivered by the Environment Agency’s collaborative delivery framework Hub A, a collaboration between the Environment Agency as client, consulting engineer Arup and civil engineering contractor Bam Nuttall to deliver flood defence schemes across northeast England.
The flood defence scheme at Hexham is expected to complete in summer 2023. Approximately 600 metres of flood walls and grass embankments will help to reduce the flood risk posed by the River Tyne. The site will be monitored to demonstrate the long-term durability and suitability of the concrete mixes and with data collected providing insights into the future use of low-carbon solutions.
Ruth Young, area carbon and sustainability lead for Bam, said: “As the Environment Agency’s construction partner in the northeast, we are carefully considering how we can limit the environmental impact of the flood defence work we deliver without compromising the strength and resilience of these structures.
“We identified Tarmac’s new low-carbon concrete mixes as innovative products, which have the potential to reduce our overall carbon impact across the framework.
“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.”
Environment Agency operations manager Leila Huntington said: “We all have a role to play in tackling the climate emergency which is why the Environment Agency has committed to reaching net zero by 2030. To achieve this we have to adapt, try innovative approaches and ensure that climate and sustainability are at the heart of what we do.
“The trial of low carbon concrete in Hexham is a fantastic example of how we can work with our partners to continue to build flood defences to better protect communities from flooding, whilst also focussing on sustainability, the environment and reducing our carbon emissions."
Tarmac’s head of commercial engineering solutions, Robert Gossling, added: “This flood defence project in Hexham highlights the clear sustainability benefits which can be achieved when clients and contractors work in partnership, in this case engaging to help understand the benefits and reduce the concrete carbon footprint of the Environment Agency. The testing comparisons will help build confidence in these new products.
“Against the backdrop of a climate emergency, the use of these mixes marks another important step for the UK concrete and cement industry along its path to net zero. We’re committed to demonstrating innovation in low carbon solutions, and we hope that the success of this trial will help accelerate adoption of this and other types of new, sustainable concretes – delivering long-term benefits for the industry.”
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