Re:Crete Footbridge
- Address 1 - street : Rte Cantonale / Rte de la Morge 1964 CONTHEY, Switzerland
- Diameter : 12
- Circular economy and waste management : Circular economy, Eco-Design, Reuse
-
67 000 €
- Builder
Ecole Polytechnique Fédérale de Lausanne (EPFL), Laboratoire d'exploration structurale (SXL)
This project won a "Technical Challenge" mention for the category "Outside the framework" of the Trophées Bâtiments Circulaires 2022.
Re:Crete, designed and built by EPFL's Structural Xploration Lab (SXL), is a footbridge made of concrete blocks saw cut from the walls of a building under renovation and reassembled into a post-tensioned segmented arch. Created as a research prototype, this footbridge demonstrates for the first time the feasibility of reusing concrete elements extracted from a cast-in-place structure in a new load-bearing structure. Concrete is the most widely used building material in the world and is a major source of the construction industry's environmental impacts. Reusing saw cut elements extends the use life of obsolete concrete. It avoids its premature crushing, while reducing greenhouse gases, demolition waste and raw material extraction.
In collaboration with the State of Wallis, in Switzerland, the prototype could be installed over the Morge river for a period of 2 years, where it is accessible to the public. The structure was therefore equipped with handrails, also made of reused materials. It is used for pedestrian mobility during the construction works on the adjacent road bridge.
The concrete blocks are extracted from the walls of the source building using a circular diamond saw. The sides of the blocks are then drilled to allow the passage of the post-tensionning cables. For the assembly of the arch, the blocks are placed on a timber centering and the post-tensioning ducts and cables are threaded through the side holes. Before tensioning the cables and removing the centering, the joints are filled with mortar to ensure contact between each block. To make the footbridge permanent and suitable for outdoor use, the exposed cut rebars were covered with an anti-corrosion paint, a hydrophobic impregnation was applied on the concrete faces and the joints were covered with waterproofing strips. However, the characteristic texture of sawn concrete, showing aggregates and rebars, remains visible on the side faces of the arch. The materiality of the bridge expresses both the source of the material, with its own history preceding that of the bridge, and the technique used to implement it. Finally, the railing was made with metal tubes from obsolete festival tents and steel wire meshes from shop furniture.
Besides providing a new design material for architects and engineers, the reuse of concrete elements is an effective solution to reduce the demand for cement, CO2 emissions and concrete waste. A detailed life cycle analysis shows that the Re:Crete footbridge has a lower environmental impact than similar solutions in reinforced concrete (-63%) or steel (-75%) and approximately similar to that of a solution in new timber (+9%).
Progress Status
Delivered
Data Reliability
Self-declared
Funding Type
Private
Website Enterprise / Infrastructure
https://www.epfl.ch/labs/sxl/index-html/research/reuse-of-concrete/Sustainable Development
- the cut reinforcement bars, visible on the cut faces of the concrete blocks, were protected with anti-corrosion paint;
- the exposed concrete faces were covered with a hydrophobic impregnation;
- the post-tensioning cable ducts were injected with mortar;
- the joints were covered with waterproofing plastic strips.
- Structural work
- Metalwork
- Concrete blocks: 2.43 m3
- Tie rod: 22 metres
- Steel posts and handrails: 40 linear metres
- Steel wire mesh: 44 m² (44 sq. ft.)
- Concrete blocks: sawn from the walls of a hotel basement under transformation in the canton of Vaud, reused as the structure of the arch. Supplied by the sawing company.
- Tie-rod: recovered from a structural testing hall at the EPFL in Lausanne, reused as posts and handrail.
- Steel posts and handrails: from an old tent used for festivals. Recovered from a material salvage centre (https://www.la-ressourcerie.ch/).
- Steel wire mesh: from old industrial shelves. Recovered from a recycling centre (https://www.ecocube.ch/).
Testimony / Feedback
- Minimization of transport distances for reused materials
- Verification of the properties of reused materials before their deconstruction or acquisition
- Minimization preparation work required on the reclaimed concrete elements
- Consideration of the durability of reused concrete through adequate construction details
What if I could do it again?
This pioneering experience of reusing concrete elements extracted from a cast-in-place structure confirmed a new way of designing structures. The technologies used (e.g. concrete sawing and post-tensioning) proved to be appropriate for the reuse of concrete blocks to design a new structure. Nevertheless, we have identified ways to further increase the environmental benefits of the approach:
Governance
Etat du Valais
Regional Authority
Ecole Polytechnique Fédérale de Lausanne (EPFL), Laboratoire d'exploration structurale (SXL)
Other
Project owner
State of Valais
Contact :Jean-Baptiste Luyet (engineer for engineering structures and exceptional transport)
Project manager
École Polytechnique Fédérale de Lausanne (EPFL), Structural Exploration Laboratory (SXL)
Contact :Corentin Fivet (professor and head of the Structural Exploration Laboratory (SXL))
Company
Diamcoupe SA
Guillaume Mittnacht (Regional Manager, French-speaking Switzerland)
Diamcoupe supplied and prepared the concrete blocks. It sawed the blocks in the walls of the source building and drilled the cores for the post-tensioning cables.
Company
Freyssinet SA
Adrian Motte (branch manager, Switzerland)
Freyssinet supplied the ducts and the post-tensioning cables. It carried out the tensioning of the cables and the injection of the ducts.
Other
Bridgology SA
Alexis Kalogeropoulos (founder and director)
Bridgology carried out non-destructive measurements on the structure to determine the cover of the pre-existing reinforcing bars and to check the condition of the concrete.
Company
Sika Switzerland Ltd
Cédric Chetelat (consulting engineer, French-speaking Switzerland)
Sika supplied the products applied on the footbridge to protect it from water (anti-corrosion paint, hydrophobic impregnation, waterproofing strips).
Company
Emil Egger Romandie SA
Frédéric Marilley (project manager)
The company Emil Egger transported the footbridge from its manufacturing site in Fribourg (Switzerland) to its installation site in Conthey (Switzerland). It also carried out the lifting for the installation of the bridge over the river.
Total cost: 67,000 €
Financial aid: 25,900 €
Total amount of work dedicated to reuse (excluding study costs: AMO, MOE, CT, etc.):19 200 €.
% reuse on total cost of the operation: 29%
As the project was carried out within the framework of academic research activities, the design costs have not been quantified. Financial aid comes from internal funding at EPFL as well as corporate sponsorship.
The reuse was estimated to result in an approximately 30% increase of cost compared to a conventional alternative. However, we believe that this additional cost is mainly due to the novelty of the method. Optimization of the sourcing, assembly and rehabilitation processes should provide a reduction in costs. Moreover, these costs are compared to a conventional alternatives whose aesthetics are not the same. Replicating an aesthetic similar to the Re:Crete footbridge with conventional materials would likely increase costs.
Sustainable Solutions
- Diamcoupe SA
- Guillaume Mittnacht
Sawing
Diamcoupe supplied and prepared the concrete blocks. They carefully saw cut the blocks in the walls of the source building directly to the desired size. The small size of the blocks allowed them to be easily removed from the deconstruction site. Diamcoupe then drilled the side of the blocks to allow the passage of the post-tensionning cables for the new structure. The re-use of these blocks on a new project allowed the company to save on landfill costs.
The approximate cost of sawing, preparing and transporting the 25 concrete blocks was around 15,000 euros.
For the sawing company Diamcoupe, this is a revaluation of their work. They become a supplier of materials, at the beginning of the value chain. The solution was therefore well received by the workers, especially as it did not fundamentally change their methods.
- Freyssinet SA
- Adrian Motte
Post-tensioning
Freyssinet supplied the ducts and prestressing cables that run through all the concrete blocks. These were inserted into the holes directly when the concrete blocks were placed on the centering. Freyssinet then proceeded to tension the cables and inject the ducts.
The post-tensioning ensures the structural safety of the structure under all live load configurations.
The approximate cost for the supply of the docts and cables as well as the post-tensioning is approximately 5,000 euros.
Post-tensioning is a very well known and widespread method. Its use in this case makes it possible to recycle materials that were originally destined for landfill. The solution was therefore well received by the workers, especially as it did not fundamentally change their methods.
Photo credit
École Polytechnique Fédérale de Lausanne (EPFL), Structural Xploration Lab (SXL)
Maléna Bastien Masse
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