# Development of a Novel Concrete Curing Method Using Induction Heating System
## 1 Introduction
Insulated forms are required only to prevent the freezing of concrete during the presetting period and to minimize heat dissipation from surfaces where coils are not used. However, moisture loss by evaporation from unformed surfaces while using internal electric heating should be prevented. In addition, the system uses energy inefficiently and the inclusion of extraneous bodies in concrete can result in detrimental effects on the strength and durability. Accelerated concrete curing methods using microwave (MW) energy have also been introduced in previous research [3; 5; 6; 7; 8; 9; 10; 11; 12]. Curing of concrete with MW energy is mainly divided into two methods: (1) direct heating of concrete in the MW oven, and (2) heating of concrete using the transferred heat generated in the steel form. The first of these has been considered as a potential technique to improve the properties of concrete [7]. The mechanism of this method has been demonstrated to be as follows: When dielectric concrete materials are subjected to MW radiation, MW penetrates into the internal structure of concrete and induces polarization and depolarization switching of molecules of the concrete constitutes (especially water molecules). This causes a friction force near the surrounding molecules and generates heat from inside the materials [3; 7]. The key parameters investigated from the studies based on this method are MW power, application time, duration of MW heating, thermal run away, and overheating within the sample. Details of these studies are available in the literature [3; 5; 6; 7; 8; 9; 10]. It is noted that this method uses MW ovens for curing concrete and, therefore, its utilization in the construction field is still limited due to the applicable size of concrete members is restricted by the size of the MW ovens. The second curing method using MW energy has been developed relatively recently [11; 12]. In this method, specially designed steel forms incorporating MW absorbers are required and MW units are attached to these forms. The MW absorbers are initially stimulated using 2.45 GHz MW to generate heat, and this heat is transferred to the steel forms to cure the concrete inside these. This method can be utilized in various industrial fields both for precast concrete and in-situ concrete. The use of MW energy is considered a potential accelerated concrete curing method but the initial cost of the MW equipment may be high, and this curing method could have negative impacts on the performance of certain concrete mixtures. Furthermore, the applicable size of concrete is limited by the MW systems, and heavier and more expensive forms are required. In this paper, a new concrete heat-curing method using an induction heating system is proposed as an alternative solution to the aforementioned issues related to the current heat curing methods. Induction heating is a method of heating that converts electrical energy into thermal energy according to the law of electromagnetic induction. The induction heating method is commonly used in various applications such as domestic and commercial cooking, heat treatment, soldering, preheating for welding, melting, shrink fitting in industry, sealing, and brazing. The method uses the magnetic flux generated by the induction coil to induce a current called eddy current. The induced current flowing on the heated object produces heat. The proposed method is suitable for accelerated concrete curing because it directly heats only the induction object, metallic forms in concrete curing. Therefore, the heat loss is minimized and, in turn, results in high heating efficiency. Safety is also high owing to the non-contact heating. It should be noted that in a general heating system, heat is produced by a heating source and then transferred to the object. This results in significant heat loss as well as the possibility of fire.