Test analysis on spiral steel fiber reinforced concrete subjected to impact loads

Abstract

Many studies have demonstrated that adding steel fibers to concrete mixture is able to markedly increase the ductility and tensile strength and thus enhance the resistance of concrete structures against blast and impact loads. However, it is noticeable that in current construction industry, the popularly used steel fibers are mainly straight fibers or hooked-end fibers that are only able to provide bonding to concrete matrix in a 2D plane. Because concretes using these fibers are vulnerable to fiber debonding, the effectiveness of using these steel fibers to improve the blast or impact load resistance is strongly limited. The present study proposes spiral steel fibers to reinforce concrete material and carries out both split Hopkinson pressure bar (SHPB) tests to investigate the material properties under high-speed compression and split tension and drop-weight tests to study the behavior of spiral fiber reinforced concrete beams under centre-point impact loads. The test results show that compared with conventional steel fibers, the crack controllability, residual strength and strain rate sensitivity can be greatly enhanced by spiral steel fibers. The significant contribution of spiral steel fibers to the improvement of protective structures against blast and impact loads is demonstrated.