Starting small: upcycling bridges one by one
We began our journey as engineers and designers fascinated by a remarkable material: ultra-high-performance fiber-reinforced-cementitious composite (UHPFRC). For over a decade, UHPFRC has been used to extend the service life of bridges thanks to its exceptional mechanical and durability properties. In Switzerland and elsewhere, hundreds of bridges have been preserved by applying a thin UHPFRC layer to their concrete decks (the UHPFRC method), thereby extending their service life and improving their performance to meet current requirements. Each successful intervention was a significant achievement; we could preserve the historic, cultural, and technical values of a bridge at a fraction of construction costs and with minimal environmental impact compared to current traditional techniques.
Figure 1 UHPFRC method applied to the Riddes Viaduct in 2021.
These were individual success stories, solved bridge by bridge. Despite being satisfying each time, we found ourselves asking a larger question: could this individual solution become a systematic strategy for bridge network management? If so, how many bridges could potentially be saved with the UHPFRC method? What would be the environmental and economic benefits?
The Swiss federal bridge network: a comprehensive dataset to enhance our idea
The first challenge was to determine the applicability of the UHPFRC method to a bridge network. We wanted to research if it could be applied to the majority of bridges rather than only a select few. That meant examining an entire bridge network – thousands of structures of different types, sizes, and ages – and assessing how widely the UHPFRC method could be used.
The biggest hurdle was finding reliable, detailed data at that scale. Many countries lack comprehensive public datasets on the condition and characteristics of all their bridges. We were fortunate in the case of Switzerland: the Federal Roads Office maintained an inventory of its 3,903 bridges, and we collaborated with them to access this dataset, as well as their forecast of bridge replacements through 2100.
Using these datasets, we quantified the number of bridge replacements that could be avoided by the UHPFRC method. To do so, we first analyzed 100+ prior applications of UHPFRC to existing bridges in Switzerland. Then, we used their key attributes (bridge construction year, condition, size, material, structural type, number of spans) to determine whether a bridge could be strengthened using the UHPFRC. If a bridge with certain characteristics had already been strengthened, bridges with similar characteristics were labeled as compatible with the UHPFRC method. On this network, we found that 99% of bridges were compatible, demonstrating that this technical solution could be nearly systematically used as the “default option” for bridges that would otherwise be replaced.
Huge environmental and economic benefits
Once the broad applicability of the UHPFRC method was demonstrated, the next challenge was to quantify its environmental and economic gains compared with the deconstruction and reconstruction of a single bridge. We first worked at a bridge-scale level and collected information on 17 UHPFRC-method projects in Switzerland, including drawings, material quantities, and design assumptions. This allowed us to perform consistent life-cycle analyses and benchmark the results against new design datasets and Swiss references. The outcome was striking: on average, the environmental impacts of the UHPFRC method are 83% lower, and costs are reduced by 75% compared with a new bridge. This highlights a key advantage of the UHPFRC method, demonstrating that it is both sustainable and economically viable.
Once the savings of the UHPFRC method are quantified at a bridge level, the number of bridge replacements must be determined. We introduced scenarios for bridge replacements based on construction year, current asset-management practices, and deterioration-based predictions. Results range from 800 to 3903 replacements over the next 80 years. For each scenario, we combined data on the number of bridge replacements with the associated environmental and economic benefits, and computed the savings until 2105. Millions of tons of CO2eq emissions - between 1.7 and 7.7 MT depending on the bridge-replacement scenarios - and billions of Swiss francs - between 3.0 and 14.9 BCHF - can be saved on the Swiss federal road bridge network by upcycling bridges using UHPFRC rather than demolishing them. These results highlight the significant potential benefits of a paradigm shift in existing infrastructure management.
Swiss numbers, worldwide implications
While our study focuses on Swiss federal bridges, its significance extends beyond a single country. The saving numbers we calculated – the exact tons of CO2eq or Swiss francs saved – are specific to Switzerland’s context. But the rationale is widely transferable. Many nations have bridge networks that, as in Switzerland, were largely built in the mid-20th century and are now aging. Construction practices and materials are often similar, so the UHPFRC method could likely be applied just as broadly elsewhere. Of course, every network has its own specifics, and local life-cycle analyses would be needed. The core message of the article is that any bridge network has a significant opportunity to upcycle rather than replace deficient assets. Our findings are less about one Switzerland-specific infrastructure network and more about a new philosophy and approach of bridge management that anyone can easily adopt.
Looking Ahead: Embracing a new bridge-management approach
The real novelty of our work lies in reframing UHPFRC from a pioneering bridge-intervention solution to a mainstream asset-management strategy. The convergence of economic and environmental benefits supports the broad adoption of a bridge management approach in which existing assets are upcycled rather than replaced. We hope that we are at a turning point; the UHPFRC method should not be seen as a local solution but as a network-wide strategy. The education of engineers on UHPFRC, the training of construction companies, and appropriate asset-management processes are key levers behind this shift towards a systematic approach for sustainable and cost-effective infrastructure management.