Pull-out behavior of corrugated steel fibers

Abstract

Abstract The choice of a steel fiber to reinforce a cementitious matrix is often made with a misunderstanding of the real capabilities of the steel fiber. In spite of the sophisticated approaches in the case of straight steel fibers, the behavior of nonstraight fibers is much less understood. A very simple test, the pull-out test, allows us to evaluate these capabilities. An experimental program is presented that has investigated the effect of the length and orientation of a corrugated circular cross-section steel fiber anchored in different water to cement (w/c) ratio matrices with a new apparatus allowing one to pull-out any variety of steel fiber from concrete matrices. The analysis of the experimental results is at first qualitative and then statistical to objectively identify the significant parameters on the fiber pull-out behavior. Because w/c ratio appears to govern the failure mode, that is fracture or debonding of the fiber, it has only a slight effect on the fiber slipping behavior. In case of debonding, the fiber slips into the print of its initial geometry with minor matrix internal degradations and is straightened after complete extraction, dissipating a significant amount of cold work energy. Finally, length and orientation of the fiber interact and considerably affect the debonding behavior. In particular, a local matrix crushing in the crack plane delays the fiber mobilization by local unfolding.