The end of which life?

19 Jul 2023

When I was an architecture student, I used to make my models out of recycled Weetabix packets. It was only partly thriftiness – I also enjoyed the different qualities they could bring, which you just didn’t get using white Kapa board. Today, I’m still more excited about working with the layers of history and materials that an existing building presents than a greenfield site.

So I’m very excited to see the greater focus on circular economy principles, and treating our existing built environment as a resource that can be harvested for new construction. This will make an important contribution to reaching net-zero, as we retain the embodied carbon in the structures we already have, but it also has the potential to transform every aspect of how we create places. In this issue alone, we highlight three major projects that have revitalised outdated or unused spaces, as well as Cement2Zero’s ongoing industrial trials of a process that reactivates recovered cement paste.

We talk about “end of life”, but in the case of concrete, a key question is: the end of which life? When we do a life- cycle analysis of a building, there’s an understanding that we’re looking at a period of 60 years – although we know that a concrete structure can retain its integrity and its usefulness for much, much longer. After that, in the UK today the vast majority of concrete from demolished buildings is recycled, whether as aggregate or hardcore, and it goes on to have a second useful life at least as long as the first. Innovations such as the Cement2Zero project could provide an additional second life use.

Different strategies will work for different parts of a building. Materials are produced via myriad different processes – so why would we assume that they should all end their life in a similar way? Instead, we need to play to their potential. While designing for disassembly and reuse elsewhere might be the best route for a steel structure, for concrete it’s probably better to adopt the milk bottle strategy: reusing the structure as it is, keeping it at its highest value for longer and expending less carbon in the process. This is not a new idea but it would be further facilitated if all of the layers attached to it – facades, services, fit-outs – were designed for disassembly.

Working out the best end-of-life strategy for each building component may need case-by-case assessment, as new technologies evolve and market factors change. Better as-built data will undoubtedly help – we can only derive value from resources if we know they’re there.

A circular approach that prioritises reuse preserves not only the financial and carbon value in a building, but its social and cultural value too. I’ll be particularly interested to see how it might influence aesthetics – rather than coming up with a design and then choosing the materials to suit it, a more sustainable approach might be to base the design on the resources available. That’s perhaps the ultimate creativity, and it adds another level of problem- solving. As a former remodeller of Weetabix packets, I know that the possibilities are endless – and exciting!

By Elaine Toogood, Director, Architecture and Sustainable Design, The Concrete Centre