Study on Pullout Resistance of Indent-Type Steel Fiber
Steel fiber reinforced mortar (SFRM) or concrete (SFRC) is one of the future promising composite materials and suits, for example, today's rapid excavation by a tunnel boring machine, a boom header or a continuous miner.
It is well known that SFRM is improved in toughness and crack resistance mainly by the pullout resistance of steel fibers. Though some pullout tests have been published, fundamental data concerning pullout resistance are still insufficient.
In this study, pullout tests were conducted pulling an indent-type steel fiber out of the mortar sample at a constant displacement rate by a servo-controlled testing machine. It was found that load-displacement curves obtained experimentally were not smooth with complicated shapes especially in the post-failure region (region after the maximum pullout resistance). The curves were classified into four patterns depending on the shapes. For every pattern, the maximum pullout resistance and the total pullout energy necessary to pull the steel fiber out of the mortar sample were obtained. Finally, the correlation between the maximum pullout resistance and the tensile strength of SFRM were discussed.
Key Words: Steel Fiber, Indent, Mortar, Pullout Test, Constant Displacement Rate, Pullout Resistance, Uniaxial Tensile Strength