CONCRETE REINFORCED WITH DEFORMED STEEL FIBERS .1. BOND-SLIP MECHANISMS

Bond-slip characteristics were investigated for three deformed steel f ibers bonded in concrete matrixes with different strengths. Fibers wer e aligned at 0, 15, 30, 45, and 60 deg with respect to the loading dir ection, and complete load-versus-slip curves were obtained. It was fou nd that the bond-slip characteristics of fibers aligned with respect t o the loading direction were significantly superior to those for incli ned fibers. Inclined fibers supported smaller peak pullout loads and a bsorbed less pullout energy than the aligned fibers. A high-strength m atrix often caused brittle fiber and matrix failures, and led to reduc tions in the energy-absorption capability. The paper provides interpre tations of the bond-slip curves based on various micromechanical proce sses in the matrix and fiber, and identifies the conditions that lead to a brittle response. The bond-slip information generated in this stu dy for the various deformed fibers will be correlated to the actual be havior of fiber reinforced concrete in the second part of this paper.