Self-localization of the flexural cracks of fiber reinforced concrete beams

•Self-sensing of crack localization of the concrete with macro fibers is studied.•Self-monitoring of the bending crack appearance and widening of concrete is investigated.•The relationship between Voltage and COD during the loading process of concrete is found.•The different resistivity of steel fiber and PP fiber may show different effect on the self-sensing ability of concrete crack. In order to localize the crack and to sense the crack widening of concrete, an alternative method is proposed in this study. The basic element of this method consists of six electrodes. To verify the validity of this method, four-point bending test is carried out on six types of fiber reinforced concrete beams with different fiber types. The voltage between two inner electrodes is used as the indicator for crack localization and widening. Both the voltage–time curve and the load-time curve can be divided into three stages by two turning points corresponding to the uncracked stage, the cracking stage and the crack propagation stage, respectively. In addition, the relationship between crack opening displacement (COD) and voltage may be established by an exponential function. The method is experimentally proved to be highly effective given that the voltage change and crack occur simultaneously. By increasing the number of electrodes, the method proposed in this paper can be applied to sense the crack appearance and widening in concrete structure. The method can be used to localize the cracks in fiber reinforced concrete beams.