## 4 Results and Discussions
### Analysis of Concrete Temperature Changes during the Pouring Process  
Owing to large forecasting errors existing in the initial stage, it was necessary to explore the main factors affecting the concrete temperature during this period. Data regarding the pouring temperature and placement temperature of the concrete were analyzed. In this study, the pouring temperature was the concrete temperature at 10 cm below the concrete surface after the concrete was put down and before vibration, whereas the placement temperature was the concrete temperature at 10 cm below the concrete surface after the concrete was vibrated and before the new concrete was covered. The first records regarding thirteen point-thermometers and the average pouring temperature and placement  
Figure 8: Comparisons of predicted and measured temperature for Wudongde dam: (**a–d**) the predicted and measured values of the four old concrete blocks, respectively. temperature in the same concrete layer are presented in Figure 9, showing that the initial records of the point-thermometers were basically between the pouring temperature and placement temperature. This indicated that the initial recording time of the point-thermometer was usually after the concrete was put down and before it was vibrated. Figure 9 also shows that the placement temperature was higher than the pouring temperature; the difference between these two temperatures was named the pouring temperature rise (PTR). The magnitude of the PTR may be related to both the environment and the hydration heat of concrete, and the duration of the heat exchange between the concrete and the external environment was related to the construction speed. However, the construction speed fluctuated within a certain range; under this condition, the main influencing factors of the PTR could be obtained based on a large amount of data. This study collected all relevant data from the Baihetan and Wudongde dams since construction started. The relationship between the PTR and the difference between air temperature and pouring temperature (DAP) is plotted in Figure 10, showing that the relationships for both dams are basically linear, thereby verifying the previous speculation of the influence of ambient temperature. Meanwhile, Figure 10 displays the trend line of each month, and the slopes of these trend lines are also plotted in Figure 11.  
Figure 10: Relationship between pouring temperature rise (PTR) and difference between air and pouring temperatures (DAP): (**a**) Baihetan dam; (**b**) Wudongde dam. Figure 9: Comparison of pouring temperature, placement temperature, and the first records of point-thermometers. Figures 10a and 11a show that the slope of the trend line for each month for Baihetan dam is divided into two sides. The slopes of the trend lines from April to September are relatively small, but are larger from October to March of the following year, following the variation law of hot and cold seasons. Figure 11a presents the monthly averages of the related temperature data during the concreting of Baihetan dam, showing that the pouring temperature of Baihetan dam was strictly controlled according to the season. From April to September, pouring temperature was low and air temperature was high; consequently, PTR was large, but the slope of the trend line was relatively small. This situation was reversed from October to March of the following year. Compared with Baihetan dam, the relevant data of Wudongde dam are irregular, as shown in Figures 10b and 11b; the pouring temperature of Wudongde dam was not strictly controlled according to the season, and the slopes of the trend lines do not change according to season. Ultimately, no correlation between the slope of the trend line and pouring temperature was observed. Through comparison, the influence of the hydration heat of cement was ruled out. During this period, the hydration rate was still slow and made few contributions to PTR, thus, the large error during this period did not affect the later prediction.