Concrete containing short carbon fibers (in amounts as small as 0.2 volume- percent) was found to be an intrinsically smart concrete that can sense elastic deformation, inelastic deformation, and fracture. The signal provided is the change in electrical resistance, which is reversible for elastic deformation and irreversible for inelastic deformation and fracture. The presence of electrically conducting short fibers is necessary for the concrete to sense elastic or inelastic deformation, but the sensing of fracture does not require fibers. The fibers serve to bridge the cracks and provide a conduction path. The resistance increase is due to conducting fiber pullout in the elastic regime, conducting fiber breakage in the inelastic regime, and crack propagation at fracture. Applications include real-time damage assessment and dynamic load monitoring.
