- Building Type : Other building
- Construction Year : 2022
- Delivery year : 2022
- Address 1 - street : Rte Cantonale / Rte de la Morge 1964 CONTHEY, Suisse
- Climate zone : [Cfb] Marine Mild Winter, warm summer, no dry season.
- Net Floor Area : 12 m2
- Construction/refurbishment cost : 67 000 €
- Cost/m2 : 5583.33 €/m2
Primary energy need :
(Calculation method : )
The Re:Crete Walkway, designed and built by EPFL's Structural Xploration Lab (SXL), is a pedestrian walkway made of concrete blocks sawn into the walls of a building under renovation and reassembled into a prestressed arch. Initially produced as a research prototype, this footbridge demonstrates for the first time the feasibility of reusing non-prefabricated concrete elements in new load-bearing structures. Concrete is the most widely used building material in the world and is the major source of the construction industry's environmental impacts. Its reuse by sawing elements offers a new extension of life to obsolete concrete, thus avoiding its premature crushing, while promising a great potential for reducing greenhouse gases, demolition waste and extraction of raw materials.
In collaboration with the State of Valais, a site was found to install the prototype and make it accessible to the public. The structure was therefore equipped with guardrails, also made of reused materials, and set up for a period of 2 years on the Morge river in Valais (Switzerland). It is used for pedestrian mobility during the duration of the works on the bridge of the adjacent cantonal road.
The concrete blocks are extracted from the wall using a circular saw with a diamond blade, then cored to allow the passage of the prestressing cables. The blocks are then placed on a wooden hanger by passing the sheaths and prestressing cables through the core drillings. Before tensioning the cables and removing the handlebar, the joints are filled with mortar to ensure contact between each block. In order to make the footbridge permanent and suitable for outdoor use, the exposed reinforcing steels were covered with an anti-corrosion paint, a hydrophobic impregnation was applied to the concrete faces and the joints were covered with strips of tightness. However, the characteristic texture of sawn concrete, patchworks of aggregates and reinforcement spacers, is kept 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 uprights and the handrail of the guardrail were made by recombining metal elements reused from an old marquee and the lattices are taken from old industrial shelves.
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 wood (+9%).
If you had to do it again?
This pioneering experience of reusing concrete elements extracted from a cast-in-place structure validated a new way of designing structures. The technologies used (e.g. concrete sawing and prestressing) proved to be appropriate for the reuse of concrete blocks to design a new structure. Nevertheless, we have identified various points to further increase the environmental benefits of the approach: - Minimization of transport distances for reused materials - Verification of the properties of reused materials before their deconstruction or acquisition - Minimization of the stages of preparation of the concrete elements to be reused - Consideration of the durability aspects of reused concrete through adequate construction details
See more details about this projecthttps://www.epfl.ch/labs/sxl/index-html/research/reuse-of-concrete/
Federal Polytechnic School of Lausanne (EPFL), Structural Xploration Lab (SXL)
CompanyDiamcoupe SA Guillaume Mittnacht (chef de région, Suisse Romande) The Diamcoupe company supplied and prepared the concrete blocks. It sawed blocks in the walls of the source building and drilled cores for the passage of prestressing cables.
CompanyFreyssinet SA Adrian Motte (directeur d'agence, Suisse) Freyssinet supplied the sheaths and prestressing cables. It proceeded with the tensioning of the cables and the injection of the sheaths.
Environmental consultancyBridgology SA Alexis Kalogeropoulos (fondateur et directeur) Bridgology carried out non-destructive measurements on the structure to determine the cover of the pre-existing reinforcing bars and check the condition of the concrete.
CompanySika Suisse SA Cédric Chetelat (ingénieur conseil, Suisse Romande) The Sika company supplied the products applied to the footbridge to protect it from water (anti-corrosion paint, hydrophobic impregnation, sealing strips).
CompanyEmil Egger Romandie SA Frédéric Marilley (chef de projet) Emil Egger transported the footbridge from its manufacturing site in Friborg (Switzerland) to its installation site in Conthey (Switzerland). It also carried out the lifting for the installation of the footbridge over the river.
- the cut rebars, visible on the cut faces of the concrete blocks, were protected with anti-corrosion paint;
- the exposed concrete faces have been impregnated with a hydrophobe;
- the sheaths of the prestressing cables were injected with mortar;
- the joints were sealed with glued plastic strips.
Construction and exploitation costs
- 67 000 €
- 25 900 €
Reuse : same function or different function
- Structural works
- Concrete blocks: 2.43 m3
- Sub-tie: 22 linear meters
- Steel posts and handrail: 40 linear meters
- Trellis: 44 m²
- Concrete blocks: sawn into the walls of a hotel basement undergoing transformation in the canton of Vaud, reused as the structure of the arch. Supplied by the sawing company.
- Sub-tie rods: salvaged from an EPFL structural testing hall in Lausanne, reused.
Reproductibility and Innovation
- Our October 23, 2021 post on building the prototype received over 1460 likes and was shared 164 times. The video was viewed more than 50,000 times.
- Our May 5, 2022 post on the installation of the Re:Crete footbridge in the Swiss Alps received more than 370 likes and was shared 12 times.
- 19 200 €
- 29 %
- 25,00 KgCO2 /m2
- 15,00 année(s)
- 25,00 KgCO2 /m2
Life Cycle Analysis
Reasons for participating in the competition(s)
The Re:Crete footbridge is an original project which integrates for the first time the structural reuse of concrete elements from an existing concrete building poured on site . It demonstrates the technical feasibility while using technologies known by the construction industry such as concrete sawing and prestressing. To guarantee the long-term durability of reused concrete elements, the structure was adapted, by simple methods, to outdoor use. The railings are also designed with recycled materials.
Confirming that sawn concrete is a new reusable structural material, this project extends the application of circular economy principles to the construction industry. A new field of activity is created, with the key to the reuse of sawn concrete elements for the construction of traditional buildings. In addition, this first prototype convincingly demonstrates that the approach can drastically reduce greenhouse gas emissions, construction waste and extraction of raw materials. Its generalization offers new perspectives to quickly contribute to the mitigation of global warming and increase the sustainability of the construction industry.