Nano-carbon black and carbon fiber as conductive materials for the diagnosing of the damage of concrete beam

The nano-carbon black (NCB) and carbon fiber (CF) as electric conductive materials were added into the concrete. The effect of the NCB and CF on the mechanical properties and on the fractional change in resistance (FCR) of concrete was investigated. The relationships among the FCR, the strain of initial geometrical neutral axis (IGNA) and the beam damage degree were developed. The results showed that the relationship between the FCR and IGNA strain can be described by the First Order Exponential Decay function, and the internal damage of concrete beam was reflected by the relationship between damage degree and resistance.

► The concrete beam with carbon black and fiber for damage diagnosis under bending was studied. ► The effect of conductive materials on the fractional change in resistance (FCR) of beam was studied. ► The relationship between FCR and strain of neutral axis of beam was suggested. ► The model of damage degree vs. FCR of concrete beam was established. ► We can evaluate the damage of concrete beam by measuring of the FCR.