The pull-out behavior of straight and hooked-end steel fiber from hybrid fiber reinforced cementitious composite: Experimental study and analytical modelling

This paper deals with the interfacial bonding performance of the steel fiber in the steel-polypropylene hybrid fiber reinforced cementitious composite. 42 groups of straight and hooked-end steel fiber specimens are investigated by the single-sided pull-out tests. The whole pull-out load-slip responses are captured, and the effects of hybrid fiber dosage, matrix strength and fiber embedded length are analyzed. Furthermore, the interfacial bonding mechanism and fiber reinforcing mechanism are revealed based on SEM images. Results show that the addition of hybrid fibers in the matrix contributes significantly to increasing the maximum and residual pull-out load as well as improving the pull-out energy dissipation capacity. The polypropylene fiber content is found to be the dominant factor for the variation of interfacial properties. For straight steel fiber, the enhancing effect of hybrid fiber on the chemical adhesion force is more pronounced than that on the sliding frictional force. For hooked-end steel fiber, the contribution of hybrid fiber is not significant on the hook mechanical interlocking. Finally, a theoretical model is developed to predict the pull-out behavior with the hybrid fiber effect taken into account. The predictions provide satisfactory correlation to the experimental results from both the current study and previous work.