Flexural response of SFRC under impact loading

Resumen

The research presented in this paper deals with the impact behavior of steel fiber-reinforced concrete (SFRC). An experimental campaign on unnotched prismatic specimens has been carried out, covering three types of steel fibers (smooth, hooked and prismatic), two volumetric contents (0.5 and 1%), and companion unreinforced plain concrete specimens. Impact tests have been performed with an instrumented drop weight testing machine recently installed at the Technical University of Madrid (UPM), Spain. According to experimental results, the peak strength and fracture energy of tested SFRC mixes are strain-rate dependent, showing dynamic increase factors (DIF) well larger than 1. On the one hand, the analysis has shown that the DIF of the peak bending strength of SFRC reinforced with smooth and prismatic fibers is higher than the DIF of the tensile strength of plain concrete and increases with the fiber content. SFRC reinforced with hooked fibers presented higher DIF with 0.5% fiber content than with 1.0%. The influence of rate-dependent size effect in the former results is discussed in the paper. On the other hand, the DIF of the fracture energy showed the highest rate sensitivity for plain concrete specimens and decreases with the addition of fibers due to the rate dependence of the mechanisms involved in the fiber matrix interaction.