Study on temperature distribution of three-cell box girder during the hydration process

After the box girder was poured, the cement hydration generated heat and produced a large temperature difference in the girder, which may lead to the cracking. In order to study the hydration heat distribution and cracking risk of three-cell girder after pouring, the scale model of box girder was poured, 258 temperature sensors, solar radiation sensors and wind speed sensor were embedded in the model. Data receiving frequency was once every 30 min, and wireless acquisition module for data collection was used. After 96 h’ observation of temperature, the temperature field distribution of hydration heat of three-cell concrete girder was obtained. The finite element model of temperature field considering solar radiation and atmospheric convection was established. The maximum temperature change due to solar radiation was 29.8% of temperature change of hydration heat. The space and time model of vertical temperature difference during heat of hydration of concrete three-cell box girder was proposed for the first time. Based on response surface model and finite element model, the maximum vertical temperature difference of different web was proposed and was verified at the Wangjiahe Bridge. The predicted values of the Wangjiahe Bridge were in approximately agreement with the measured values. Compared to the initial concrete temperature of 35 °C without geotextile cover, the initial concrete temperature of 15 °C with 8 mm geotextile reduced the vertical temperature difference to 24.7% at most.