As COP29 is now well underway and climate change is once again under the spotlight, our Sustainability Committee thought it would be a good opportunity to share their thoughts and experiences on areas where the construction industry can make a difference with some examples of this in practice.
Ahead of this mini-series that we will be posting next week, our Head of Sustainability, Aidan Wingfield, is sharing his thoughts following a visit to Holcim’s Innovation Centre in Lyon on the future of one of the single largest sources of global emissions: concrete.
“Last week I had the genuine pleasure of being invited by Aggregate Industries to visit the Global Innovation Centre of their parent company, Holcim, in Lyon.
Aside from the nice weather, good food, and fascinating conversations with fellow guests from across the UK construction industry, it was brilliant to see the progress Holcim and Aggregate Industries have been making in pursuit of genuinely sustainable concrete, and some of the innovations which are just around the corner.
For the past ten years, my work on sustainability has been centred around the measurement and reduction of embodied carbon in structures. Over that time, embodied carbon has gone from a somewhat fringe topic to a key consideration through its inclusion in industry targets, building assessment methodologies, national and international standards, and even planning requirements. Focusing specifically on reinforced concrete in the UK, some of the highlights over that period include:
- Comparatively low embodied carbon cement replacement materials have been increasingly utilised to lower the embodied carbon of cement mixes. This has been widely understood across the industry, to the extent that specification and use of fly ash or blast furnace slag in concrete mixes steadily expanded to become the default option in most cases.
- Secondary and recycled aggregates have seen increased attention and use.
- Concrete demolition waste has become widely downcycled into sub-base materials, piling mats, reducing demand for virgin materials.
- Reinforcement is largely sourced from recycled steel and produced in electric arc furnaces, reducing associated emissions to as little as ¼ of what they otherwise could have been.
As I will cover in more detail in another post which will close out our sustainability series next week, these factors have combined to significantly reduce the embodied carbon of reinforced concrete structures particularly. In recent years though, we have noticed that these reductions have plateaued, and even reversed. A popular example of this has been the dwindling, and now exhausted, domestic sources of the most common UK cement replacement materials, and the implications of importing them.
It was therefore inspiring to see the potential for how the industry may be transformed in another ten years if even just a few of the innovations Holcim showcased were to become standard practice. While it would be easy to write a few essays on each of these topics, a few of my key open questions and takeaways on this optimistic view for the future for the industry are:
Could the lower embodied carbon, calcined clay concrete be the most common mix in the UK in another ten years?
In my view, calcined clays, and multi-component clay and limestone mixes, must be how we transition away from reliance on imported GGBS. Not only is there continued potential for embodied carbon reduction in this, particularly if domestic clay sources can be utilised, but the technology that companies like Holcim are investing in to decarbonise production, from heat recovery to carbon capture, has the potential to further drive down their associated carbon emissions in the future.
In ten years, could we be reflecting on net zero (or negative!) embodied carbon cements being the new default?
There have often been claims in the industry around cement-free alternatives with concrete, or ultra-low carbon cements, of which I have typically been sceptical. Either due to doubts about future approval for structural uses, or how genuinely sustainable chemical alternatives really are. In Lyon, a clear picture was painted for an affordable route to genuine sequestration of carbon in cement on the horizon.
Will circularity have been embraced, such that UK Construction could be delivering concrete mixes with little to no virgin material constituents in ten years?
Arguably even more so than was the case ten years ago with embodied carbon, the construction industry’s focus needs to pivot to Regenerative Design, mitigating waste, restoring nature positive solutions, and delivering circularity. Reuse of construction demolition materials has been something of a holy grail for those of us interested in sustainable concrete, but it always seemed like an impossible mountain to climb. Keeping with that analogy, I was surprised to find how close Holcim are to reaching the peak; 100% reuse of concrete is technically possible, theoretically infinitely circular, and crucially could have a pathway to practical implementation and be scalable.
I echo the views of Nick Powell, of Aggregate Industries, that collaboration with the whole supply chain is vital in the pursuit of sustainable concrete in the UK. However, with developments such as reinforcement-free 3D printed concrete bridges, carbon fibre concretes, carbon capture and storage, decarbonised production techniques, and the reuse of concrete and cement, companies like Holcim and Aggregate Industries have done the ‘Lyon’s’ [sic] share of the work, it is incumbent on us to help with the next steps to make the vision of truly sustainable concrete a reality.
I would like to repeat my thanks to Nick Powell and Aggregate Industries for the invite, and to Madhura Joshi and Holcim for hosting my fellow attendees and me. The hard work of everyone at the Innovation Centre is mapping out a pathway to eliminating one of the biggest sources of global emissions, without sacrificing the use of a versatile material which is, quite literally, the foundation of the modern world.”