AJ Climate Champions podcast: ‘Over-specification of concrete is an industry addiction’

Structural engineer Eva MacNamara of Expedition Engineering explains how we can radically reduce our use of concrete and the biodiversity impacts of construction materials

In this episode, we dive into the tricky topic of concrete and unpick the widespread mantra that ‘concrete is bad’. Concrete is ‘an addiction’ that has led to an obese construction industry, says Expedition’s MacNamara. Concrete is not going to go away but we can radically reduce our use of it, according to MacNamara. She describes a proposed pad foundation design for the Eden Project site in Dundee which would achieve an 80 per cent reduction in concrete volume.

MacNamara stresses that ‘using less’ is much more beneficial than substituting low-carbon concretes and notes that she repeatedly sees practitioners over-specifying. We discuss some of the nuances of concrete use: which applications are most appropriate, how to reduce the volumes we use, and why low-carbon concrete – especially GGBS – is not a silver bullet. We also touch on upcoming innovations, including Seratech, ‘funnel’ slabs, and smart crushing.

MacNamara explains how to bring both carbon and biodiversity into the concrete procurement process. Highlighting findings from the recent report The Embodied Biodiversity Impacts of Construction Materials (Expedition/ICE, November 2023), she notes that 95 per cent of biodiversity impacts occur off site and that the new biodiversity net gain requirements only address the 5 per cent on site, so designers must look beyond the site’s boundary.

Finally, MacNamara advocates finding a place to innovate on every project. ‘We can make the most difference by using our projects as springboards for incubating innovation,’ she says.

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About Eva MacNamara

Civil and structural engineer Eva MacNamara is an associate director at Expedition Engineering and one of the authors of the concrete chapter in Materials: An Environmental Primer (RIBA Publishing, 2024). She is also a director of the Useful Simple Trust.

After four years at Atelier One, Eva joined Expedition in 2011. Her portfolio spans a wide range from bridges to Renzo Piano’s LEED Platinum Stavros Niarchos Foundation Cultural Center in Athens, to the modest Skip Garden in King’s Cross, built almost entirely with reused materials, an AJ Small Projects winner in 2016.

Eva has a strong interest in leadership and has taken part in the UK GBC Future Leaders programme, the Regenerative Design Lab, in 2022 and she is currently completing an online Power MBA.

Eva recently directed the research for the report, The Embodied Biodiversity Impacts of Construction Materials (Expedition/ICE, November, 2023). She is currently leading Expedition’s work on the Eden Project in Dundee with Feilden Clegg BradleyStudios.