By Arghavan Akbarieh
Are we too enchanted with the promises of circularity and reuse in construction? How can we recalibrate our expectations? asks Arghavan Akbarieh, PhD student in Circular, Sustainable, Digital Construction at University of Luxembourg
Arghavan attended the CIRCuIT summer school hosted by Hamburg University of Technology in July 2022. Following four educational site visits during the school, she shares her observations around some of the barriers hindering the uptake of circular construction approaches.
1. Demolition sites – overcoming reclamation obstacles
We arrived at the demolition site to learn that a demolition contractor had refused a contract from another company asking them to perform a material reclamation (bricks, in this case) for reuse instead of demolition. They cited the following reasons for their refusal: a lack of in-house expertise on how to complete the task effectively, and a disagreement on offering the deconstruction and reclamation service for the same price and within the same time limit as a typical demolition project. Taking bricks out without damaging them would require serious effort, including further labour and procedures needed for cleaning and protecting the bricks from any performance drop before delivery.
This got me thinking: why did the service requester think that a deconstruction and reclamation service should (or could) be done within the same price and time constraints as a demolition service? Is it because we generally perceive second-hand products to have lower prices? If so, are we still treating the reclaimed materials as second-hand products, and should we instead treat them as first-hand products since we expect the same performance from them?
2. Reclaimed materials storage solutions - the role of urban planning
Urban planners cite the lack of storage space for reclaimed materials as a major barrier. Land is expensive and it's not cost-effective for storing materials on a potentially long-term basis, with no guarantee that they’ll even be reused. Should the local government or city provide a storage site in every urban area? We have recycling centres, so why not storage spaces for reclaimed construction materials? This might not always be feasible in existing urban areas or historic city centres, but should cities trial some initiatives?
If we are going to redesign our whole approach towards engineering, architecture and procurement in circular construction, perhaps it is time for other actors to step up and provide land and spaces owned by the city to enable this – starting with integrating storage solutions into our urban planning.
3. Designing with reusable structural elements – future considerations
We visited a co-op which has plans to build a multifunctional social housing development in place of a decommissioned multistorey car park. They had intended to reuse the lower parts of the structure, cut some openings in the middle for lighting and build on top of the slab of the first floor. However, chloride had infiltrated the concrete slabs and columns, rendering them unsuitable for structural reuse, and consequently the whole building needed demolishing. We learned that the concrete slabs were directly exposed to air for over 60 years - a protective layer would likely have prevented the chloride intrusion. The Design for Deconstruction (DfD) guidelines advise avoiding adding extra layers to make the elements more usable for the future. However, in this case, the situation seemed to be the opposite; protection could have potentially saved the concrete. Should we rethink the power of protective layers against exposure instead of completely neglecting them for the sake of future reuse? Not having protective exterior layers could backfire on us in a future where we expect more extreme climate events, higher temperatures, pollution, and acid rain. My conclusion was that more effort should be directed towards creating sustainable protective layers instead of completely removing them from the equation.
4. Recycled concrete aggregates – learnings and challenges
On the final day we visited “Die MusterBude,” a beautiful demonstrator of how recycled concrete can be used in new buildings. Intriguingly, they had used recycled materials in different structural elements to test the performance of this recycled concrete with conventional cast-in-place concrete. Here’s what I learned:
Recycled concrete aggregates are usually rough, meaning its interaction differs physically and chemically from natural aggregates because it has already been once active.
The performance of recycled concrete differs from conventional concrete. This is why its use is so far limited to walls, pavements etc. but not for the foundation.
Easy access to natural resources could be an anti-driver for using recycled aggregates. As long as raw materials such as sand and gravel are easily attainable, the momentum for creating robust concrete with recycled concrete aggregates will not increase.
Finally, my most valuable lesson: the dilemma of fly ashes. They’re good replacements for cement (not completely). Adding them to the concrete mix can reduce the environmental impact of concrete. However, fly ashes are by-products of coal-burnt power plants. As we transition away from burning coal in favour of green, renewable energy sources, we’ll no longer have access to fly ashes - quite a trade-off.
This blog is an abridged version of Circularity vs. Reality, first published by the author on LinkedIn. Read the full article here.
Comentarios