Pull-Out Mechanisms of Polypropylene Fibers Embedded in Cementitious Materials

This research aims to study the pull-out mechanisms of different types of polypropylene (PP) fibers embedded in cementitious materials. Single fiber pull-out test was used to study the bond. All prepared samples had half dog-bone shape with 25x25 mm in cross section and 100 mm in length. The main result of this pull-out test was the relationship between the pull-out load and the slip at the tip of fiber. The variables in this study included: 3 types of polypropylene fibers defined as PP1, PP2, and PP3; 3 levels of embedded lengths of the polypropylene fiber; and 3 levels of compressive strengths of mortar. It was observed that each type of PP fibers gave the similar results of the pull-out behaviors. Linear behavior was observed at the beginning of pull out. After peak pull-out load, the pull-out load dropped continuously having wavy shape until the fiber was pulled out from mortar corresponding to the surface textures of each fiber. Moreover, it was found that a decrease in the size of fibers, an increase in the embedded lengths of fiber, and an increase in com pressive strength of mortar would lead to the better the pull-out strength index or the bond performance of fibers under pull-out.