Estimating the microstructural bond mechanism of TRC structures by their electrical properties

The study presents a new methodology to assess the bond mechanism of textile-reinforced concrete (TRC) elements. Since changes in the electrical properties of carbon yarns are correlated to their microstructural bond mechanism, they can be indications of the shear-bond stress-slip relation. The study developed a new setup enabling sensitive electrical measurement without affecting the mechanical response, yet clearly capturing the microstructural mechanism. Carbon yarn is electrically characterized as an RL circuit, comprising a resistor (R) and an inductor (L) connected in series. The study offers to explore both properties by measuring the response spectrum of the impedance at a specified range of electrical current frequencies. Results demonstrated that changes in the electrical resistance and inductance in a localized cracked zone are directly correlated to the shear-bond stress (τ)-slip relation. It was found that the rate of changes (ROC) of both electrical properties reflect and follows the microstructural mechanism and, accordingly, provides new insights on the internal stress distribution. To quantitively estimate the τ-slip relation, a conversion factor (α), that correlates between the ROC and the τ-slip relation, was evaluated by adjusting the ROCs to the structural response from numerical model. It was found that, for the investigated composition, the conversion factor is α = 7.88 ± 0.97 [mΩ·mm/N], yielding that the ultimate shear bond stress is about τ_ultimate = 2.2 ± 0.32 [MPa] which is acceptable value. The proposed methodology can be easily implemented in various compositions and provides a useful method to estimate τ-slip relations.