EPFL scientists have built a footbridge made up of concrete blocks repurposed from walls of a building being renovated.
Said to be a world’s first, the scientists led by assistant professor Corentin Fivet first cut the blocks into individual pieces on site and then assembled them into a prestressed arch.
The scientists say that their initiative could substantially shrink the construction industry’s carbon footprint by helping them to adopt a more ‘circular economy’ approach.
“People are hesitant to reuse concrete due to a variety of concerns,” says Fivet, who heads EPFL’s Structural Exploration Lab (SXL) within the Smart Living Lab. “But we wanted to show that those concerns are largely unfounded.”
“Blocks of concrete that are selected for reuse are just as reliable and useful as new blocks.”
According to postdoc Maléna Bastien Masse – who conducted the research with PhD graduate Jan Brütting, the scientists gave themselves two months to find a source building in the region and a demolition company that would be interested in working with them.
This led them to Swiss construction company Diamcoupe, which had been commissioned to renovate a building erected less than 10 years ago.
“We asked Diamcoupe to cut the concrete into the sizes we needed and to drill holes through them for our prestressing cables,” says Bastien Masse. “These cables were provided by Freyssinet and used to build the arch.”
Thanks to this initiative, the engineers were able to obtain 20cm-thick concrete blocks for the footbridge.
They then added mortar in places to smooth out the slight differences in dimensions, which are inevitable anytime objects are reused.
According to Fivet, most buildings in Switzerland are made out of concrete, and producing this raw material accounts for 7% of CO2 emissions from anthropogenic activity.
What’s more, concrete makes up 50% of demolition waste. When the material reaches its end of life, it’s at best broken down into gravel or granulate to create recycled forms – but that consumes a lot of energy.
“If we were instead to cut up concrete blocks and reuse them, we could both prevent the need to produce more concrete and eliminate the inert waste,” opines Fivet.
“No other new concrete footbridge has a carbon footprint as small as ours.”
“Imagine if every obsolete concrete structure out there was cut into blocks and used to meet some of the global demand for new concrete. That would be a big step towards addressing some of the most pressing climate-change challenges.”
Image and content: EPFL