A study on refined curing control of precast segmental concrete for prefabricated railway bridges

To ensure the prefabrication quality of concrete segmental beams for assembled railway bridges, this study investigates the main factors affecting the casting and curing of such beams. Using the Zheng-Xu regional railway bridge as a case study, this study analyzes the impact of environmental temperature, formwork materials, formwork thickness, pouring temperature, wind speed, and prestressed ducts on the thermal-structural coupled stresses in the beams, based on meteorological conditions at the prefabrication yard. A detailed concrete curing control plan is proposed. The research results show that formwork materials and pouring temperature have a significantly greater influence on the early thermal effects of prefabricated concrete segmental beams than other factors. Formwork materials exhibit the highest sensitivity to temperature and temperature stress, with sensitivities of 17.8% and 36.1%, respectively, followed by pouring temperature, which has sensitivities of 12.7% and 21.7% to temperature and temperature stress, respectively, and is positively correlated with peak temperature and peak stress. Wind speed and prestressed ducts are sensitive to temperature stress, with their sensitivities being less than 5%. Prestressed ducts promote internal heat dissipation in concrete segmental beams, reducing the internal peak temperature and the temperature difference between the interior and exterior, thereby lowering the risk of cracking. The better the thermal insulation performance of the formwork materials, the later and higher the temperature peak. Additionally, the thickness of the formwork materials has a greater impact on the temperature and stress of the segmental beam concrete. Based on the identified temperature field and thermal stress patterns for each significant factor, this study proposes detailed curing plans, including winter steam curing and summer spray curing. These strategies effectively reduce the internal-external temperature difference, minimize surface stresses, and mitigate the risk of cracking. The quality of prefabricated concrete segmental beams confirms the scientificity and rationality of the fine-curing control plan, which can serve as a reference for the detailed control of prefabrication and curing.