Cut Costs With UHPC Ductal®: the Cudrex Viaduct example
Structural overlay with Ductal® concrete saved the Cudrex viaduct in Switzerland from being completely rebuilt.
Ductal®, a Simple, Effective and Low-cost Solution to Protect Engineering Structures
Built in 1968 in Bussigny, in the Swiss Canton of Vaud just outside Lausanne, the Cudrex viaduct transports 27,000 vehicles a day and is the canton's second most popular bridge. The weight-bearing bridge is under extreme pressure and the wear and tear of 50 years of use had rendered it in desperate need of repair. From May to October 2016, it underwent the construction work required for road serviceability. Although the prestressed concrete load-bearing structure was still in good condition, the expansion joints had seen their last days and the guardrails were no longer compliant with current standards. However, the interesting thing about this worksite was certainly the overlay using Ductal®— a fiber-reinforced ultra-high performance concrete (UHPC)—to seal the bridge's load-bearing structure. This state-of-the-art material, which is six to eight times more resistant than traditional concrete, also has better longevity, malleability and sealing properties.
Laying down of Ductal® - Cudrex Viaduct Switzerland - ARC Photo
A Race Against Time
Due to the location of the worksite in the midst of a major thoroughfare with no detour possible, traffic could not be disrupted more than absolutely necessary. The maximum time traffic could be blocked was from 8pm Saturday night to 4am Monday morning. From the moment the road was closed, workers started prepping the surface, using hydrodemolition, repairing damaged areas and fixing corroded metal rods prior to laying down the UHPC. To save time and effort, the Ductal® concrete was mixed onsite in a batching plant to keep UHPC transport to a minimum and customize the mix to suit conditions every step of the way.
The worksite ran like clockwork. It was mandatory that traffic be opened up a mere 18 hours after the sealing overlay. All construction was complete in less than six months and the casting of the Ductal® concrete over the 400-meter surface was finished in only eight nights. Since UHPC isn't normally used for surfaces with vehicle access, gravel was laid down to provide sufficient grip for through traffic. Then the gravel was coated to make the surface rougher and more sound-absorbent.
The Devil's In the Details
The load-bearing structure wasn't damaged but secondary structures were thoroughly degraded. The expansion joints were replaced and the drainage system—which was hard to maintain, inefficient and compromised as water penetrated the concrete—was replaced with an external suspended drainage channel.
The medians were in very poor condition and required frequent night construction to maintain, let alone the guardrails that were no longer to standard. As such, the medians were renovated and the guardrails replaced. The new perk? The Ductal® concrete overlay is now protecting the medians from wear and tear due to freezing and salt.
Fast and Efficient
Considering how important this work was, a fast, cost-effective solution with as little traffic disturbance as possible was essential. UHPC was the perfect solution. Ultra-high performance concrete is extremely dense and weatherproof and is much more resistant than traditional concrete. Its high metallic fiber content prevents cracking, completely protecting the load-bearing structure. Last, but certainly not least: Ductal® concrete requires only 18 hours from casting to be fully operational. A traditional sealing solution would have required blocking traffic for three weeks straight.
Layout of Ductal® - Cudrex Viaduct Switzerland
Pascale Wolff, Project Manager for the Direction générale de la mobilité et des routes du canton de Vaud (the department of transportation for the Canton of Vaud) is happy to be using UHPC. "It was the least cumbersome, most efficient and easiest in terms of managing traffic—by far the best solution," she highlighted in an interview last September with Batimag, a construction magazine. She also underscored the fact that they had thought of everything to try to reduce the impact on traffic—including building an interim bridge—and had exhausted all other options. But at the end of the day, that idea would have more than doubled the tab which, thanks to UHPC, amounted to a reasonable 5.75 million Swiss francs. The benefits of this new technology have "streamlined decision-making immensely," Wolff told Batimag.
Stakeholders in the worksite
Project owner: the Canton of Vaud – (DGMR)
Construction supervision: Daniel Willi SA
Company: Martin & Co
UHPC provided by: Ductal® LafargeHolcim
Replacing the Medians - Viaduct of Cudrex Switzerland
Timely preliminary studies on building material resistance
Just-in-time Ductal® cement delivery for worksites on a tight schedule
Advisory on building materials and technical project supervision