Memoria tratta da "The New Boundaries of Structural Concrete: Session B – Controlled-performance concrete", ACI IC - Bergamo 2013
In structural elements steel fibers can be used instead of or in addition to reinforcing bars, in order to bear tensile loads. The addition of steel fibers to plain concrete changes its mechanical behavior, since, depending on the type and amount of fibers, an increase in ductility can be achieved. Hooked steel fibers were employed for reinforcing concrete at different dosages in order to evaluate their effect on the post-cracking behavior of concrete. The fiber reinforced concrete was characterized at the fresh state by means of slump test, and after hardening by means of compression, tensile and bending tests. In every case, for equal strength class mixtures, the same first cracking strength was obtained whichever the dosage of fibers. On the other hand, softening or hardening post-cracking behavior was detected depending on the amount of fibers. In order to quantify this effect, toughness was calculated for each mixture, with the aim of identifying the critical volume of fibers.