Often, steel fiber-reinforced shotcrete (SFRS) linings are applied in underground construction. In some areas of high tensile stresses, it is necessary to use additional ordinary reinforcement (reinforcing bar/mesh). It may be inefficient to switch to non-fibrous shotcrete for these regions. Are the shadowing problems to be expected in that case (SFRS with additional ordinary reinforcement) more severe and how can they be resolved?

It is not uncommon to encapsulate lattice girders or steel sets in fibrous shotcrete. The skill of the nozzleman, the size and density of the reinforcing, and the characteristics of the mixture and the accelerator are the most important factors in achieving good encapsulation of reinforcing bar or these more complicated applications around lattice girders or steel sets. With welded-wire reinforcement, you should have a 4 x 4 in. (100 x 100 mm) or greater spacing. With reinforcing bar, you should use the minimum diameter possible at a minimum spacing of around 6 in. (150 mm). Preconstruction mockups should be considered to prove the competency of the nozzleman and the mixture. Please note that the best nozzleman cannot succeed without a good, workable mixture.