Compressive strength and ductility of steel fiber reinforced concrete

It is known that Steel Fiber Reinforced Concrete (SFRC) has advantages over plain concrete. In particular, fiber reinforcement makes concrete tougher and more ductile. Although these attributes are appealing for earthquake resisting structures, design codes do not yet incorporate specifications relative to the use of SFRC for structural applications. Recent developments have indicated a good potential for SFRC in structural and seismic applications. In the first part of this paper, the beneficial effects of SFRC in the seismic design of columns are briefly reviewed. The paper then presents an overview of an ongoing research project on column strength and ductility in which 18 columns were tested in uniaxial compression. The variables considered were the fiber content of 0%, 0.5% and 1.0% per volume, the amount of transverse reinforcement for confining the column core, and the confinement provided by the fibers in the cover. It is shown that SFRC improves significantly the post-peak behavior of columns for all hoop spacings and that SFRC can be juxtaposed with reduced traditional confining reinforcement under the same seismic design philosophy. Although SFRC in the cover delay its spalling, no noticeable confining contribution of the cover was observed. Fibers do not really confine concrete, but rather change the failure mode by limiting the progression of cracks and enhancing the aggregate interlock along failure planes.