Re:Crete – Reuse of concrete blocks from cast-in-place building to arch footbridge

About 9% of anthropogenic greenhouse gas emissions worldwide are due to the production of cement, key constituent of concrete. Concrete also contributes to a large share of demolition waste, usually coming from building structures that are discarded because of functional obsolescence rather than of technical deficiency. Current practice for treating end-of-life concrete is to landfill it or crush it into aggregates used in new concrete mixes. Instead, a little-explored strategy consists in extending the service life of concrete elements by reusing them in new constructions. Following this paradigm, this paper presents a proof-of-concept prototype that reuses blocks cut out of obsolete cast-in-place concrete walls for a new structural application: a 10 m-long post-tensioned segmented arch footbridge. The paper details the design, material sourcing, and construction processes while highlighting the unusual features of the approach. The structural behavior is verified with a finite element analysis model and validated by load testing. A comparative life cycle assessment shows that the arch construction presents a significantly lower global warming potential then recycled concrete (−71%) or steel (−74%) alternatives and is very competitive to a timber one (+9%). In conclusion, the project proves the feasibility of a new circular economy application for the construction industry, in which new and reliable concrete structures are built with little to no cement inputs.