Damage indication by electrical resistivity measurement of carbon short fiber reinforced concrete in fatigue testing

The newly developed material carbon short fiber reinforced concrete (CSFRC) was investigated extensively in the last years. This material combines high tensile strength of the carbon fibers with ultra-high compression strength of concrete. The focus lies on orienting the fibers in order to gain the most possible tensile enhancement. This is achieved by admixing the carbon fibers in the wet concrete and extruding the paste throughout a small nozzle guided by a specifically designed concrete 3D-printer. Due to very high fatigue resistance of carbon fibers, this study is looking at bone shaped tensile specimens under high cyclic fatigue load, hi order to obseive the process of crack growth and the mechanics of fatigue failure, we combined measuring techniques as digital image correlation and electrical resistivity measurement. Carbon fibers are electrical conductive and they transfer this ability to the compound material and to the specimen. By measuring the voltage drop at several specific points 011 the specimen’s surface, allows to detect material degradation. The amount of electrodes and connection nodes were increased continuously in order to enhance accuracy and to obtain a localization of material degradation. Comparing the results with digital image correlation, both measuring methods show up parallels, meaning changes in strain are also visible in conductivity measurement.