Ohmic heating curing of carbon fiber concrete beam in realistic cold weather: The influence of electrically insulated steel rebars

This work attempted to investigate the on-site application of ohmic heating curing method on the structural concrete with steel reinforcement. The steel reinforced carbon fiber concrete beams were cured by ohmic heating method in the realistic severely cold weather. It was found that steel rebars disturbed the electrically conductive network formed by carbon fibers, resulting in a reduced curing duration of 48 h and an abnormal temperature distribution with high corner temperature and low core temperature. Electrical insulation treatments (epoxy resin coating and heat-shrink tubing) were taken and evaluated based on the ohmic heating features and mechanical properties. The results showed that the epoxy resin coating had a limited insulation effect, with an electrical resistance of 3.9 Ω, which displayed a similar temperature distribution with the uninsulated beam. On the contrary, the heat-shrink tubing had a significant insulation effect with an electrical resistance of 36.5 Ω, leading to an average core temperature of 23.6 ℃ during 7 days of curing period. The average rebound strength of beams with epoxy resin coating and heat-shrink tubing was 34.0 MPa and 41.6 MPa, respectively, and the ultimate deflection of beams was 34.37 mm and 49.18 mm, respectively, which was in correspondence with the temperature distribution. Besides, the heat-shrink tubing increased crack spacing width of beam, while the epoxy resin had little influence on crack pattern. This work emphasized the importance of electrically conductive path of concrete for ohmic heating curing method and gained practical experience of this method on the structural concrete.