In tunnels, mainly metallic or synthetic fibres are used.
Metallic fibre for concrete reinforcement has a filament-like appearance with a hoop-like ending at the extremities. This design allows it to achieve greater adhesion to the concrete. They can be delivered in two variants, free or glued, and in different diameters and lengths.
The main quality of synthetic fibre is its resistance to water, thus increasing the long-term life of the concrete. It is very easy to apply and does not require specific equipment.