Influence of individual fiber characteristics on the achievable performance classes of steel fiber shotcrete

Shotcrete has been used for decades to reinforce and secure slopes, tunnels or mine tunnels. Until the 1970s, shotcrete was primarily reinforced with wire mesh or reinforcing steel mesh. Since then, steel fibers have increasingly been added to shotcrete. This simplifies the work processes (reinforcement work) and shortens construction times, in some cases considerably.

Particularly in the field of underground construction, the advantages in terms of quality and economy have increasingly increased the importance of steel fiber shotcrete. According to the current draft of the DAfStb guideline "Steel fiber reinforced concrete", steel fiber shotcrete is divided into performance classes. The manufacturer of the ready-mix concrete, usually the ready-mix concrete plant, must thus ensure the performance classes specified by the designer by specifically defining the fiber characteristics (shape, slenderness, steel grade and content of steel fibers). For steel fiber shotcrete, it is only in very rare cases that existing empirical values with conventional steel fiber concretes can be used.

In recent years, initial orienting knowledge has been gained on the influence of certain fiber characteristics on the achievable fiber concrete class of steel fiber shotcrete using the method of equivalent flexural tensile strengths in accordance with the DBV bulletin "Steel fiber concrete". However, they do not allow a generally valid assignment of different fibers to achievable performance capabilities of steel fiber shotcrete.