The Effect of SHCC Strengthening Layers on the Impact Behavior of SFRC Short-Beams

The addition of fibers, such as steel, as randomly dispersed reinforcement in concrete is effective in improving the behavior of structural elements subjected to impact loads, reducing the formation and propagation of cracks, spalling, and mass loss. Moreover, it is possible to consider the use of external thin strengthening layers as strain-hardening cementitious composites (SHCC), where their high energy dissipation through the formation of multiple cracks further contributes to the impact resistance and structural integrity maintenance after high strain rate loadings. In the present work a drop-weight impact test machine with energy up to 2.5 kJ was designed and instrumented with piezoelectric loading cells, piezoelectric impact accelerometers, and a data acquisition system with a capacity of 2 million samples per second. This impact machine, allied with a digital image correlation (DIC) system with two high-speed cameras, was used to acquire the strain and displacement data to understand the steel fiber reinforced concrete (SFRC) behavior under impact loading. The addition of steel fibers to concrete reduces crack formation and deflections after impact loads, reducing damage and maintaining the SFRC specimen’s integrity when compared with ordinary concrete’s impact resistance. Short-beam SFRC specimens were molded and subjected to an impact three-point bending test using state-of-the-art drop-weight equipment with a strain rate of 4.2 s−1. Poly-vinyl-alcohol (PVA) SHCC thin strengthening layers were added to undamaged and pre-cracked short-beam SFRC at the top or the bottom face of the specimens to evaluate their contribution to reduce the crack formation and propagation under impact loading.