## 5 Discussion and Conclusions  
### Analysis and Discussion  
Based on the above studies, the basic characteristics of the 3D humidity field in the early age period of road panels can be summarized as follows.  
(1) The environment significantly influences the surface humidity of the concrete panel. The humidity trend of the concrete panel at 2 cm depth after pouring and completion exhibited a similar pattern to the fluctuation trend of environmental humidity when it reached its lowest value during the early age period. As shown in Figure 24, the trend was not significantly affected by cement hydration in the first three years, but after three days, the fluctuation trend of humidity inside the board was completely consistent with that of environmental humidity.  
(2) The humidity at the top of the early cement concrete panel decreased rapidly with age, and the humidity difference at the bottom of the panel was always negative, and this trend increased with age since the top of the panel was the main area of moisture loss while the bottom surface remained mostly saturated (with a humidity of 100%). The surface moisture loss caused the moisture difference between the top and bottom of the panel to remain negative and to gradually increase. This difference will cause horizontal shear stress in the board, which may induce horizontal interlayer peeling disease. Prolonging the moisturizing and curing time can reduce such diseases.  
(3) The sensitivity of concrete panel surface humidity to the environment varied depending on the location. Based on simulation and humidity monitoring results, it was found that the corner of the panel was the most sensitive to the environment, followed  
Figure 24: Fluctuation between humidity inside the board and ambient humidity in the first 7 days.  
by the edges, while the middle of the panel was the least sensitive. This conclusion is consistent with other studies [10; 28].  
The difference in sensitivity of concrete panel surface humidity to the environment could be attributed to variations in humidity on each diffusion surface. Due to diffusion, nodes closer to the surface experienced greater internal and external humidity gradients. The concrete water loss was faster when there was a large humidity gradient and the moisture balance between the concrete and the environment was maintained. This phenomenon was observed in areas with high humidity gradient diffusion surfaces. Specifically, there were three high humidity gradient diffusion surfaces in the corner of the board, two on the edge, and one at 2 cm depth of the plate. The number of high-humidity gradient diffusion surfaces in each position was directly proportional to the balance between the humidity of the concrete and the environmental humidity in that area.  
(4) The humidity distribution in road panels was highly heterogeneous, with humidity concentrations in the middle and bottom regions of the panel. During the 28-day period, there was a significant difference in humidity between the top surface of the panel at depths of 2 cm, 4 cm, and 6 cm, and the maximum humidity difference occurred in the middle of the panel (1.3%, 2.3%, and 2.9%, respectively).