Smart carbon fiber reinforced concrete for structural health monitoring

Structural monitoring systems are important in civil engineering. However, traditional structural monitoring systems have disadvantages such as the shorter life span of sensors relative to that of the structure being monitored. The present study uses carbon fiber reinforced concrete (CFRC) as a structural monitoring sensor to extend the life of a sensor to match that of the structure. There are some known advantages of carbon fiber reinforced concrete, such as high tensile strength and high ductility which increases the seismic capacity and security of structures. However, CFRC has functionality similar to piezoresistive materials which can be used as a self-sensing material for strain measurement and damage detection. This property is based on the reversible effect of the strain on the volume of electrical resistivity and the irreversible effect of material damage on its resistivity. The strain sensing behavior is such that the resistivity decreases reversibly upon compression due to the slight inward push of crack-bridging fibers and the consequent decrease in the contact electrical resistivity of the fiber-cement interface. Similarly, the resistivity increases reversibly upon tension due to the slight outward pull of crack-bridging fibers and the consequent decrease in the contact resistivity. To consider the economic benefits, the fiber content is only 0.2 vol. % which is less than half of the amount used in other references (0.48 vol. %). The experimental results show that the conductivity of current materials is significantly improved by CFRC and that it can be used for strain measurement and damage detection with fiber content of 0.2 vol. %. Moreover, the experimental results of CFRC coated beams can be kept in a database for applications in the future.