Tensile response of ultra-high performance steel fiber reinforced concrete under moderate strain rates

This study presents the stress-strain response of different ultra-high performance fiber reinforced concretes (UHPFC) under direct tensile loading applied at moderate strain rates. Four UHPFC mixes incorporating two straight steel fiber types with different fiber volume fractions and hybrid combinations are tested under uniaxial tensile loading at a nominal strain rate of 0.000025 1/s and 0.01 1/s. The tensile tests were accompanied by non-destructive measuring technique using digital image correlation (DIC), in order to verify the obtained stress-strain information of the composite material. The strain rate sensitive changes in the mechanical response of the material, including crack formation and crack propagation are analyzed and described. Furthermore, relevant strain softening and hardening parameters, such as first and post-cracking strength, strain capacity, energy absorption capacity, as well as the dynamic increase factor (DIF) are determined and discussed to compose a consistent experimental data-base for UHPFC under moderate strain rates.