Pilot project: Consortium led by ZÜBLIN uses steel fibre-reinforced tubbings in the construction of the U5
24 April 2026
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- First tunnel construction project in Germany secures approval on a case-by-case basis
- Steel fiber segments reduce steel content by around 60 percent
- Part of the CO2 reduction strategy for the U5 in Hamburg
The U5 has reached another milestone in climate-friendly underground construction in Germany: During the construction of the new underground line in Hamburg U5 GmbH is able to use steel fibre-reinforced concrete segments in tunnel construction for the first time in Germany. These prefabricated concrete components, which are used to line and stabilise tunnels from the inside, are characterised by their reduced steel content, with the traditional reinforcement of steel bars being replaced by finely distributed steel fibres in the concrete.
U5 has received a so-called ‘approval in individual cases’ (ZiE) from the technical supervisory authority for this application. The joint venture (ARGE) between ZÜBLIN and Wayss & Freytag can therefore install tubbings with a significantly reduced steel content in the machine-manufactured tunnel tubes on the first U5 construction section from 2027 onwards.
Steel fibre-reinforced segments reduce steel requirements by around 60 per cent compared to conventional segments, whilst maintaining the same load-bearing capacity, durability and safety. Particularly in tunnel construction, where material usage and emissions are of significant concern, this makes a tangible contribution to CO₂ reduction and thus becomes a key component in implementing the CO₂ reduction strategy for the U5.
U5 has received a so-called ‘approval in individual cases’ (ZiE) from the technical supervisory authority for this application. The joint venture (ARGE) between ZÜBLIN and Wayss & Freytag can therefore install tubbings with a significantly reduced steel content in the machine-manufactured tunnel tubes on the first U5 construction section from 2027 onwards.
Steel fibre-reinforced segments reduce steel requirements by around 60 per cent compared to conventional segments, whilst maintaining the same load-bearing capacity, durability and safety. Particularly in tunnel construction, where material usage and emissions are of significant concern, this makes a tangible contribution to CO₂ reduction and thus becomes a key component in implementing the CO₂ reduction strategy for the U5.
The use of steel fibre-reinforced tunnel segments is a further component of the CO₂ reduction strategy for the U5, through which the project aims to reduce its construction-related CO₂ emissions by around 70 per cent compared to conventional construction methods. Together with the experts from the construction consortium comprising ZÜBLIN and Wayss & Freytag, CO₂-reducing measures for the U5 are being systematically developed and pursued.
In addition to CO₂-optimised planning, CO₂-reduced reinforcing steel and low-clinker cements are already being used, and electric construction machinery is being tested in practical applications. In a next step, further reduction opportunities through the use of special concrete mixes for the tubbings are to be examined in more detail.
With this approval on a case-by-case basis, the U5 is taking on a pioneering role in German tunnel construction whilst simultaneously sending a further signal regarding the responsible use of innovative and climate-friendly construction methods.
In addition to CO₂-optimised planning, CO₂-reduced reinforcing steel and low-clinker cements are already being used, and electric construction machinery is being tested in practical applications. In a next step, further reduction opportunities through the use of special concrete mixes for the tubbings are to be examined in more detail.
With this approval on a case-by-case basis, the U5 is taking on a pioneering role in German tunnel construction whilst simultaneously sending a further signal regarding the responsible use of innovative and climate-friendly construction methods.
