When time ravages from within

Will the reinforced concrete bridge still be standing for years to come, or has corrosion already set in? ETH scientists have discovered that previous concrete samples were too small to allow a reliable statement on the condition of reinforced concrete.

Taminabrucke opened in June this year following four years of construction. At 475 metres, the reinforced concrete bridge is the longest arch bridge in Switzerland. Reinforced concrete may enable architecturally impressive structures, but as both experience and numerous worldwide studies confirm, the material is prone to harmful environmental influences, such as CO2 in the atmosphere and de-icing salt in particular.

Over the years, chloride from the salt penetrates the concrete until it eventually reaches the steel reinforcement and the armouring iron begins to rust.

Reinforced steel structures are checked regularly to detect damage early and prevent corrosion – the destruction of steel by penetrating chlorides. This is a big and increasingly important job when all the bridges, tunnels and buildings made from reinforced concrete between the 1950s and the 1970s in Switzerland are taken into account. And the older the structure, the higher the risk that the reinforcing steel in the concrete will corrode.

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