Brief 

The western section of a so-called “super sewer” tunnel being constructed under the River Thames includes high-strength interlocking concrete blocks composed of excess building material. Engineers on the project are also making use of concrete with partial slag- and fly-ash-based replacements to portland cement whenever possible.

 

Insight

Utility Week Innovate pores over the large-scale recycled concrete innovation at the Thames Tideway Tunnel.

According to the Paris agreement, carbon emissions from cement – which accounts for approximately 8% of global CO2 emissions, is the second most used material on earth and the most widely used man-made material – need to fall by at least 16% by 2030 for the world to reach its target of keeping global warming within the limit of 1.5oC.

In 2021, 40 members of the Global Cement and Concrete Association (GCCA) affirmed their commitment to net zero concrete by 2050 and agreed to an ambitious intermediate goal of preventing five billion tonnes of CO2 emissions by 2030 – bringing together companies from the Americas, Africa, Asia – including India and China – and Europe in the process.

The UK cement industry has cut its emissions by 53% since 1990, with utilities attempting to build on this at large scale infrastructure projects such as the Thames Tideway Tunnel – the £4.2 billion project to create a 7.2m diameter tunnel winding for 25km at depths of up to 70m beneath the capital.

 

Cutting volume of new concrete

Dan Webster, environmental manager on the western section of the Tideway project, tells Utility Week Innovate that the team at Tideway’s Carnwath Road site in Fulham has integrated the production of high strength interlocking concrete legato blocks from surplus building material into business as usual.

“This surplus concrete comes from the concrete lines and transportation bullets used to transport the concrete to the shutters from the batching plant on the surface,” he explains.

 

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