Detection of CFRP-concrete interfacial defects by using electrical measurement

In carbon fiber reinforced polymer (CFRP)-strengthened reinforced concrete (RC) structures, bonding defects at the CFRP-concrete interface may cause serious structural safety problems. To effectively detect interfacial bonding defects, this paper proposes a defect detection protocol based on an electrical measurement method. A total of 40 CFRP-concrete composite specimens, varying concrete type, number of defects, defect length, defect distribution, electrode arrangements and defect resistances, were prepared and tested to assess the feasibility of the proposed protocol. Experimental results indicated that the proposed electrical measurement method is practical for identifying bonding defects at the CFRP-concrete interface. The location and quantity of the interfacial defects at the CFRP-concrete interface were effectively characterized by analyzing the extreme values of electrical resistance in the resistance distribution curves. The results also showed that the resistance of concrete and defects had little effect on the detection results, while the detection efficiency and accuracy of the electrical measurement were significantly improved by using an applicable electrode arrangement. To estimate the detailed location and length of interfacial defects, an analytical model was established with the help of data regression. A comparison between the experimental and predicted results demonstrated the favorable detection accuracy of the proposed model. The outcomes of this study can serve as a possible methodology for evaluating the bond defects between CFRP and concrete.