Flexural performance of RC beams with electric activation curing at subzero temperatures followed by 800-day natural exposure

Electric activation (EA) curing at subzero temperatures demonstrates significant potential for preventing early frost damage and enhancing curing efficiency in cold-region concrete construction. Current research predominantly focuses on cementitious material properties and early-term curing effectiveness, leaving critical knowledge gaps in structural component behavior, particularly regarding long-term mechanical performance. The effect of EA curing on the long-term performance of structural members is still unclear, and the absence of this key scientific issue has seriously constrained the engineering application process of this technology. This study addresses this scientific gap through 800-day natural exposure testing of reinforced concrete (RC) beams subjected to two-day EA curing at subzero temperatures, followed by cyclic wind-dry-wet conditions and large temperature fluctuations. Four-point bending tests revealed that EA curing beams maintained identical failure modes to standard condition (SC) curing counterparts, while the ultimate bearing capacity improved 15.3 % compared with the same age period beams. The treatment promoted crack dispersion and refined crack openings. Although 28-day energy consumption metrics showed significant improvements (95.2 % total energy and 31 % yield energy enhancements), these effects were comparable between EA and SC curing conditions after 800-day exposure. This suggests that EA curing improves the early strength of concrete. The convergence in long-term flexural performance is attributed to accelerated degradation of reinforcing steel and concrete matrix under environmental exposure. Field measurements and calculations confirmed 40 % higher energy efficiency of EA curing compared to steam curing. Long-term exposure tests show that EA curing has no significant negative effects on reinforced concrete structural performance, alleviating concerns about accelerated deterioration of members over time. These findings lay the theoretical groundwork for deploying this energy-efficient technology in cold region infrastructure.