LEADER
Scandi gris
There’s quite a Scandi vibe to this issue of Concrete Quarterly, with our cover story and innovation feature both highlighting examples from Denmark.
It’s not unusual for us to include projects from other countries – we actively seek out inspiration from around the world. This is particularly the case when it comes to sustainability, as cracking net-zero is absolutely a global issue. Local conditions may be unique, but designers and supply chains in every country face the same challenges.
Scandinavia is renowned as a leader in this field – it’s no coincidence that the world’s first cement plant to be fitted with industrial-scale carbon capture is in Norway, where Heidelberg Materials’ Brevik facility has reached mechanical completion. That can-do spirit is also on show in GXN’s (P)recast project, an ingenious way of extracting slabs from end-of-life public housing and using them as precast planks in new homes on the same site.
Both carbon capture and component extraction will be part of a net-zero concrete ecosystem, but they are long-term endeavours. Fortunately, there are plenty of opportunities to reduce carbon that designers can seize right now.
Calcined clay is a big one, and you can see it in action in Copenhagen, where architect BIG has used its own HQ as a test bed. Here, 30% of the cement in the in-situ concrete was substituted, reducing its embodied carbon by 25%. Clay is abundant in many places around the world, including as a waste stream.
It’s less energy-intensive to produce than cement, with no process emissions. It can already be specified in the UK under BS 8500, so the BIG HQ is a fantastic proof-of- concept that will hopefully be an inspiration to many. One of the barriers to using alternative cements is that they can take longer to reach strength requirements. Where programme constraints won’t allow this, technology can help: on the Capella building in London, contractor Laing O’Rourke used smart sensors to provide real-time data on how the concrete was curing. This revealed that the speed of strength gain was faster than expected, and enabled a tweak to the mix to use even more GGBS.
Material-efficient design is another area where apparently minor changes can make a big impact. Our Concept tool helps designers to quantify the impacts of early-stage decisions on grid spacing, loading and structural systems. These can be dramatic: in our theoretical example, the embodied carbon of the concrete structure of an office building is cut by 42% before the concrete specification is even considered, by reducing the imposed load and column spacing, and switching to a waffle slab.
Of course, an even more efficient way to design is to reuse an existing concrete structure. Uncovering the original waffle slab was the key to reinventing an unloved 1970s Liverpool tax office as a high-concept apartment building. So while it’s always nice to bask in a little Scandi style, we can also find plenty of inspiration closer to home.
Elaine Toogood, Director, Architecture and Sustainable Design, The Concrete Centre