Impact Test: Multiscale Fiber-Reinforced Concrete Including Polypropylene and Steel Fibers

Fourteen reinforced concrete beams of 6 x 10 in. (150 x 254 mm) in cross section are designed with a combination of multiscale fibers including nanoscale carbon, microscale polyvinyl alcohol, and two types of macroscale polypropylene/steel fibers to experimentally investigate the structural performance under impact loading. Based on falling-weight impact tests, multiscale fiber-reinforced beams significantly enhance the energy dissipation mechanism by prolonging the impact duration and increasing the toughness. Furthermore, they significantly reduce spalling and scabbing damage from an impacting projectile, which may in turn result in reduced fatalities from structural debris or airborne concrete fragments. It is concluded that fiber-reinforced concrete (FRC) members singly reinforced with nanofibers alone in conventional concrete-fiber mixtures do not significantly change the fracture-dominant failure mode, despite excellent nanomaterial properties. In contrast, nanoscale materials provided in combination with macroscale and microscale fibers positively alter the impact energy absorption mechanism.