Damaged concrete bridges
‘Smart’ steel to seal cracks and extend service life
Researchers at Empa have developed a material that can stabilise dilapidated concrete bridges. The steel contracts when heated, helping to seal cracks and strengthen the structure.
Many bridges date from before the 1980s and are reaching the end of their service life – the new system is designed to extend the service life of reinforced concrete bridges.
The method relies on a combination of two special materials: a layer of ultra-high-performance fibre-reinforced concrete (UHPFRC) with reinforcing bars made of an iron-based shape-memory alloy (Fe-SMA). This steel has the property of ‘remembering’ its original shape.
Self-healing effect
After installation, the steel bars are heated to around 200 degrees. They attempt to return to their original shape, thereby generating tension in the concrete and helping to close cracks and reduce deformation.
Tests on damaged concrete slabs showed that the load-bearing capacity at least doubled. In everyday use, too, the method proved more effective than conventional reinforcement.
Use in cases of severe damage
The structure becomes stiffer, and permanent deformation is delayed. Cracks visibly close when heated. Due to high costs, the method is particularly suitable for severely damaged bridges. A first practical application is being sought.
