Reinforcement effect and mechanism of carbon fibers to mechanical and electrically conductive properties of cement-based materials

In this paper, carbon fibers with hydrophilic surface modification were added into cement mortar through ultrasonic treatment. The mechanical and electrical properties of carbon fiber filled cement mortar were tested to examine the reinforcing effect of carbon fiber. In order to understand the underlying modification mechanisms of carbon fibers to cement mortar at micro scale and in theory, scanning electron microscope (SEM) observation and theoretical calculations were carried out. Test results indicate that the adding of carbon fibers into cement mortar enhances the mechanical strength (especially compressive strength), and decreases the electrical resistivity of carbon fiber filled cement mortar. SEM results show that the enhancement of the properties of carbon fiber filled cement mortar owes to fiber ability of restraining the growth of microcracks and absorbing energy by overcoming its pulling out. The enhancing mechanism of carbon fibers on the properties of cement mortar analyzed by the calculated fiber numbers per unit volume, average center distance between two carbon fibers and the critical pull-out length well matches the experimental results.