Episode 48. AJ Climate Champions with Hattie Hartman and Joe Jack Williams. Structural engineer Eva MacNamara of Expedition Engineering explains how we can radically reduce our use of concrete and how to better understand the biodiversity impacts of material choices.

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; it is not going to go away but we can radically reduce our use of it. She describes a porposed slab design for the Eden Project site in Dundee which would achieve an 80% reduction in concrete volume.

MacNamara stresses that ‘using less’ is much more impactful 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.

McNamara 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% of biodiversity impacts occur off site and that the new biodiversity net gain requirements only address the 5% on site, so designers must look beyond a 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.

For show notes and to catch up on all AJ Climate Champions episodes, click here.

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