Strain Rate Dependent Tensile Behavior of Ultra-High Performance Fiber Reinforced Concrete

Abstract

Ultra High Performance Fiber Reinforced Concretes (UHP-FRC) can be designed to resist increasing tensile loading after first matrix cracking, which results from strain hardening tensile characteristics accompanied by multiple cracking. Previous investigations carried out under static loading conditions have clearly shown that matrix composition, fiber material and geometry as well as fiber volume fraction and fiber orientation influence the strain hardening tensile behavior. This paper describes research that was conducted to study the direct tensile behavior of UHP-FRC loaded at various speeds. A hydraulic test machine was used to apply load up to 10³ times faster than static loading, i.e. up to a strain rate of $\dot{\varepsilon}$ = 0.1 s^− 1. The test setup was designed to permit reliable measurement of direct tension test results at the different loading speeds considered, taking into consideration a reasonable gage length for multiple crack development while minimizing the inertial effects associated with the specimen and attached measurement equipment. The strain rate dependent tensile behavior is analyzed in terms of peak strength, strain at peak strength, hardening modulus and energy absorption capacity prior to softening. The results show the strain rate sensitivity of each of these parameters at fiber volume fractions of 2, 2.5 and 3%.