## 1 Introduction  
Corrosion of steel reinforcement is one of the main problems in traditional concrete structures, which severely affect its safety and serviceability. Several corrosion protection measures, including but not limited to cathodic protection, epoxy-coated bars and galvanized steel reinforcements have been implemented in the past; however, they have only managed to delay corrosion rather than eradicating it [1]. The most promising alternatives available that could entirely stop the process of corrosion within concrete is the use of fiber-reinforced polymer (FRP) bars/strands [2; 3; 4; 5; 6]. Depending upon the types of reinforcing fibers used, the FRP bars/strands can be classified as GFRP (Glass-FRP), CFPR (Carbon-FRP), BFRP (Basalt-FRP) and AFRP (Aramid-FRP) bars, respectively for glass, carbon, basalt and aramid fibers. The FRP bars are resistant to all the elements that leads to corrosion in steel reinforced concrete (RC) structures, such as reduction of pH of the concrete from carbonation, chloride contamination of the concrete and diffusion of halides and chemicals [7; 8]. The use of FRP bars for reinforcing new structures is even more preferable because they also have 1.5-2 times higher tensile strength than their steel counterparts [9; 10; 11]. In addition, although the initial cost of FRP bars is higher than that of the conventional steel bars, their life cycle cost analysis indicates that it can be quite economical in the long term [12]. Given these circumstances, the embedded FRP bar is gradually becoming a trusted material in civil engineering. To ensure construction quality and continued structural reliability, the necessity for innovative non-destructive testing (NDT) methods or research on the feasibility of existing NDTs becomes more apparent with the rise in use of unique structural materials such as FRP bars. Although higher durability and performance are associated with the FRP bars in some respects when compared to steel, concerns still remain regarding damages and defects in this material, many of them rather unique, such as debonding, delamination and aging from UV exposure. It is equally important to understand the damages and defects associated with the use of FRP bars as it is for other structural materials. Further, it is even more crucial to identify the signs of possible failure of structures reinforced with FRP bars at the earliest because they are not as ductile as conventional constructions [13] and do not display any exterior warnings of damage until they break [14]. However, there has only been minimal or non-existing work carried out for assessment of FRP embedded within concrete. The only available comprehensive guide for the inspection of FRP application in civil engineering is the NCHRP report 564 [15], which is limited to the inspection of FRP bridge decks. Currently, there is no guide or manual for the inspection of FRP-reinforced concrete elements [16; 17]. This is in most part because of the lack of research on non-destructive testing and inspection of such elements. Most FRP bars are undetectable or have low detectability and therefore cannot be effectively located in the inspection, which makes detection of their damages difficult. The use of FRP material in highway construction has increased consistently [18; 19; 20; 21], but the lack of methods for condition assessment of FRP-RC has noticeably dampened the proliferation of FRP use. Bridge owners are not comfortable with products that cannot be detected properly and whose condition cannot be effectively assessed for maintenance purposes. Hence, there is a strong need for research on the means and methods of condition assessment of FRP-RC, the availability of which will have exponential effects in increasing the use of FRP in future constructions. The main objective of this paper is to determine the feasibility of the most common NDT methods in detecting embedded FRP bars/strands, which would act as an initial step for propelling future studies on the nondestructive testing of FRP bars/strands.