The bridge in the photo is part of the Olskroken project in Gothenburg, Sweden.1 The project used alternative additives to decrease the amount of cement in the concrete bridges, supporting carbon-emissions reduction. Image © Trafikverket and Degree of Freedom
This article first appeared on the WSP website. We are very grateful for their permission to repost the article here.
Decarbonization is a challenge common to all sectors of the built environment. This high-priority issue involves both operational carbon (from the in-use phase of a structure) as well as embodied carbon; the latter includes carbon from the manufacture of materials and the transport and assembly of components used to produce a structure. In the following Q&A, we spoke with bridge engineers Daniel Ekström and Johan Lindersson, WSP in Sweden, to explore opportunities to reduce carbon emissions associated with bridges—focusing on material choices and approaches that support environmental sustainability.
Can environmentally friendly solutions strengthen resilience to the impacts of climate change?
Johan Lindersson: Climate-change impacts can be of various types, and we must take these impacts into consideration when developing the design. This need can, in turn, raise additional questions. For example, extreme cold can result in more ice that pushes against bridge supports, and this occurrence might increase the use of de-icing agents, which can shorten the technical lifespan of a bridge. One countermeasure is to include more concrete cover. Then the issue of using more material arises. Utilizing environmentally friendly additives in concrete to reduce the amount of cement therefore becomes even more important; making the bridge more resistant to de-icing agents or to the wear and tear of sea ice grinding on the supports could extend the lifespan of the bridge, and thereby generate benefits over the long term.
The effects from rising sea levels or from flooding after severe rain could be prevented by shifting the location of a bridge to a higher level, but that, in turn, could mean a longer road and longer travel requirements. One way of addressing increased water in rivers is making supports with much more erosion protection.
What are the key takeaways to move forward with decarbonization efforts?
Daniel Ekström: All professionals play their important part differently in the project lifecycle, but real change requires a holistic approach so that each contribution can add up to make significant impact in the carbon-reduction challenge. Again, it is important to understand the chain of interdependencies when creating bridge structures; one choice may have a large effect on possible choices for others and impact the ability to find the most sustainable solution overall.
As engineers, we have a great responsibility to both inform and influence our clients. The decision may not always be ours, but at least we have made our clients aware that there may be better choices to consider.
Johan Lindersson: Engineers have the potential to reduce far more CO2 than many other people in society by addressing the type and amount of material used in construction, refurbishment and repair.
The carbon emissions diagram helps us understand not only the impact of our design work but also, and perhaps even more significant, how much positive impact we as engineers can make to reduce carbon emissions.
While the approaches we have discussed are focused on bridges, it is essential that everyone involved in developing the built environment challenge their way of working, to include measures that will reduce each carbon footprint.
1 Trafikverket (The Swedish Transport Administration) – about the Olskroken Project
2 Ekström, D., Al-Ayish, N., Rempling, R. et al (2017), “Climate impact optimization in concrete bridge construction,” 39th IABSE Symposium, September 21-23 2017, Vancouver, Canada – Engineering the Future