Rate Effects of Fiber-reinforced Concrete Specimens in Impact Regime

A study of the rate sensitivity of prismatic specimens of steel fiber-reinforced concrete (FRC) is carried out in this contribution. Experimental results are analyzed from impact tests carried out with an instrumented drop weight testing machine. FRC mixes with two types of fibers have been studied, namely short straight fibers and long hook-ended fibers. The experiments have included two amounts of fibers (volumetric fractions of 0.5% and 1.0%), and also companion unreinforced plain concrete specimens are studied. The analysis has focused on the bending properties of the studied mixes, i.e. bending strength and absorbed energy. The study shows that each particular mix of FRC has different rate sensitivity because the dynamic behavior is a consequence of the rate dependence of the mechanisms governing the interaction between fibers and matrix. For the impact strain-rate domain achieved in the tests (1-10 s-1), it is shown that the study has to be done in terms of the energy absorption capacity of FRC. According to the results, the rate sensitivity decreases as the amount of fibers increases and, furthermore, the rate sensitivity of FRC mixes with hook-ended fibers is smaller than that of FRC mixes with straight fibers.