Steel fiber reinforced concrete (SFRC) is a composite material made of hydraulic cement, fine and coarse aggregate, others components/admixtures commonly used in concrete and a dispersion of discontinuous small steel Fibers. It has been used in concrete since the early seventies and for different applications like slab on ground, pavements, bridge decks, shotcrete for repairs and underground linings and precast elements. In the common usage for slab on ground, the length of fibers varies from 25mm to 75mm and the diameter from 1,3rnm to 0,5mm. Steel fibers can have different shapes like flat and wavy or round with hooked ends. There are produced mainly from four different manufacturing processes and, generally speaking, high performance fibers are mainly made using the cold hard drawn process. For slab on ground, the usual amount of steel fibers ranges from 15 kg/cubic meter to 45 kg/cubic meter. The main effect of adding steel fibers to concrete is the improvement of ductility.
However, the main effect of adding steel fibers in concrete, that is also the main advantage of SFRC and the most useful regarding design of hyperstatic construction (like slab on ground), is its post-crack behavior or toughness of SFIRC. Steel fibers in concrete start acting when the first crack appears and have the ability to absorb and redistribute the loads (or energy), so that the SFRC will still be able to bear loads even after the formation of cracks. In fact, SFIRC has a ductile behavior or toughness and therefore, that surplus of flexural capacity from the plastic phase (post-crack ductility) can be used for design of structure when deformation must be controlled like slabs or for structures where deformations controlled the design like underground linings.
It is the reason why, for the same thickness, a SFRC slab on ground can support higher loads than a conventional concrete slab.