The bridges, which were built in the 1980s, are showing increasing signs of fatigue and need to be repaired. Researchers and engineers from the Structural Engineering Department at the Swiss Federal Laboratories for Materials Science and Technology (Empa) in Dübendorf are working on new methods for renovating these bridges. For their experiments, they are using a bridge deck made of ultra-high-performance fibre-reinforced concrete (UHPFRC) reinforced with shape memory steel, according to a press release. This steel is an iron-based steel made from an alloy containing manganese, silicon and chromium, among other elements. The fibre-reinforced concrete is bonded to this steel. When heated, the steel contracts and closes any cracks that have appeared in the concrete.
The researchers led by Angela Sequeira Lemos and Christoph Czaderski carried out corresponding experiments in Empa’s construction hall. Five concrete slabs, each five metres long, simulate bridge elements. One of these remained unreinforced, while the others were reinforced with conventional reinforcing steel or shape memory steel. For the test, cracks were made in the slabs to simulate real-life wear conditions. The results showed that the combination of fibre-reinforced concrete and shape memory steel was more effective. It was able to close cracks and lift sagging bridge sections. “We were able to show that our system not only works, but can actually revive existing bridges,” Angela Sequeira Lemos is quoted as saying in the press release.
The research project was funded by Innosuisse and supported by OST– University of Applied Sciences of Eastern Switzerland, re-fer, a spin-off of Empa in Seewen, and the Swiss Cement Industry Association cemsuisse. A practical test on a real bridge could spark interest from industry. “And with increasing demand, material costs are also likely to fall – then this technology could bring about lasting change in bridge renovation,” Sequeira Lemos is convinced.
