Pull-out behavior of steel fiber embedded in flowable RPC and ordinary mortar

The aim of this research is to investigate some of the factors which affect the steel fiber-matrix bond characteristics by means of pull-out test. Ordinary mortar (OM) and reactive powder concrete (RPC) were used as main matrices. The effect of parameters such as end condition of fiber (smooth or hooked-end), embedment length, water/binder ratio, paste phase of RPC, steel-micro fiber, and curing conditions on fiber-matrix pull-out behavior were determined. The fiber-matrix bond characteristics improved as the embedment length of fiber increased, especially for smooth fiber. Low W/C ratio, which enhances the bond strength, reduces the importance of embedment length of the hooked-end fiber. Furthermore, the pull-out peak load and debonding toughness increased as the W/C ratio decreased in the all curing conditions. Microstructural investigation revealed that the congestion of hydration products in fiber-matrix interface improves pull-out behavior remarkably.