## 1 Introduction
In contrast, dielectric heating can achieve uniform internal heating and, if necessary, the location of the electric field can be specified [36, 37]. However, the dielectric constant of a heated object may vary significantly during heating. Further, because dielectric heating requires a higher frequency power supply than induction heating, power converters such as inverters are required [38]. Therefore, dielectric heating systems are expensive, and there is a risk of inductive and radio wave interferences due to the harmonic waves generated by power converters. To avoid the inductive failure of the power supply system, the supply line providing power to the dielectric heating furnace and other power supply systems are kept independent, and an active filter is also used [39]. Furthermore, to overcome the possible interference with other radio devices, a power source in a frequency band provided exclusively for dielectric heating is used. However, owing to problems associated with high frequencies (short wavelengths) and the required equipment, the efficiency of use for dismantling structures is relatively poor compared to induction heating methods [40]. Weakening mechanisms have been applied in the manufacturing of recycled aggregates with the aim of removing deposited mortar on the surface of aggregates. However, heating methods involving external heat sources exhibit a low energy efficiency and high energy consumption, and result in the generation of greenhouse gases during the regeneration processes [41, 42, 43]. Dielectric heating can be performed through uniform internal heating and, if necessary, by selecting the location of the electric field [44, 45]. However, the dielectric constant of an object may vary significantly during heating. Because dielectric heating requires a higher frequency power supply than that of induction heating, power converters, such as inverters are required [46]. Therefore, the use of dielectric heating systems in facilities is considered to be expensive; these systems also pose a risk of inductive interference and radio wave interference due to the generation of harmonic waves by power converters. To overcome such cases of inductive failure of the power supply system, a separate power supply system is used for the dielectric heating furnace alone, and an active filter is used to reduce the interference [47]. Furthermore, radio wave interference with other radio devices can be overcome by using a power source in the frequency band provided exclusively for dielectric heating. However, owing to challenges faced with high frequencies (shortening wavelengths) and the required equipment, the use of dielectric heating methods for dismantling structures is considered to be less effective than that of induction heating methods [48]. Therefore, this study adopts a high-frequency induction heating mechanism wherein the most commonly used reinforcing steel inside concrete is considered as a conductive resistor and is heated [49]. The actual reinforced concrete structure uses a variety of different diameters of reinforcements depending on its shape and characteristics. Moreover, because the concrete is reinforced with varying thicknesses of the coating layer, the heating efficiency varies significantly depending on the diameter of the reinforcement. In this study, the most commonly used reinforcing bars were used, and the heating efficiency based on the diameter of the reinforcing bars and the penetration efficiency based on the thickness of the coating were determined. The effects of the frequency used and the maximum heating area to be heated based on the temperature distribution were simultaneously and comprehensively examined to verify the feasibility of the heating system technology. Based on the various heating patterns, which depended on the back-reinforcement state and heating position of the reinforcing steel to be heated, we attempted to establish a methodology to achieve the optimum efficiency of the temperature-raising mechanism through high-frequency induction heating.