Winter Construction of 60 m Precast Railway Box Girders: An Investigation into Efficient Thermal Insulation Strategies

Large-scale concrete box girders are prone to early-age cracking because of the hydration reaction. To expedite the winter construction of large-scale precast box girders while mitigating the risk of thermal cracking induced by hydration heat, this study performs in situ temperature field monitoring and investigates the strength development of concrete under various curing conditions. The temperature field is numerically simulated using finite element analysis software ABAQUS and the secondary development of the subroutine. A parametric analysis is conducted to evaluate the influence of insulation rooms, insulation temperatures, and concrete placing temperatures. The results indicate that thermal insulation during winter construction effectively accelerates the development of concrete strength and enhances production efficiency. Compared to natural curing conditions, elevated insulation temperatures increase the temperature difference between the web core and inner surface, while reducing the early-stage temperature differences between the web core and outer surface. To minimize excessive temperature differences in large-scale box girders caused by hydration heat and thermal insulation during winter construction, it is recommended to maintain the concrete placing temperature below 19 °C and the insulation temperature within the range of 15–20 °C.