## 3 Early Behavior of Cement Concrete Pavement Panels Moisture Field
### Influence of Different Factors on the Moisture Field of Pavement Panels at Early Ages
#### 3.3.3 Influence of Structural and Construction Parameters  
(1) The effect of pavement panel thickness. According to the traffic and highway grades, the concrete panel surface thickness was generally between 180 and 300 mm. We next analyzed the influence of the panel thickness on the relative humidity h and humidity difference \(\Delta\)h of the concrete panel roof. Figures 16 and 17 show the influence of different surface thicknesses on the humidity field. Figure 16: Effect of ambient temperature on the moisture content of concrete panels. Figure 15: Effect of solar radiation on humidity difference of pavement panels. As shown in Figures 16 and 17, the effect of panel thickness on both panel humidity and humidity difference was not significant. The relative humidity at 2 cm was not affected by the pavement thickness, and the difference in relative humidity between different thickness cases did not exceed 1%. The humidity difference was positively correlated with the thickness of the pavement panel, but the difference in humidity between panels of different thicknesses was not significant, as it did not exceed 1%. Therefore, it was concluded that the variation in slab thickness had little impact on the moisture field distribution during the early age of concrete. (2) The influence of paving time  
It is widely thought that the initial environment to which concrete pavement panels are exposed can significantly impact the panel's moisture diffusion behavior. Next, we analyzed the influence of paving time on the relative humidity of concrete panel roof h and humidity difference \(\Delta\)h. We selected four construction periods, 1:00, 7:00, 13:00, and 19:00, and analyzed the influence of paving time on concrete humidity (Figures 18-21). Figure 17: Ambient temperature on pavement. Figure 18: Effect of laying moment on the moisture content of concrete panels. As shown in Figures 18-21, the paving time had a significant impact on the humidity field of the panel during its early age period within the first 24 h, and the extent of the influence gradually decreased with age, mainly due to the following characteristics:  
1) The maximum humidity difference at the top of the panels with different paving times at the same time is 1%. The humidity of the road panels decreased with age in all four construction periods, with fluctuations in a cycle. After reaching the peak, the humidity slowly declined. For the road panels constructed at 1:00, the humidity dropped sharply and then decreased slowly to reach the second peak point. For the road panels constructed at 7:00, the humidity decreased the fastest and reached the first peak point. For the road panels constructed at 19:00, the humidity dropped more slowly and reached the second peak point. For the road panels constructed at 13:00, the humidity dropped quickly to the first peak point, but the peak point was lower than that of the road panels constructed at 7:00. 2) Different paving times had a maximum impact of 1% on the panel's humidity difference at the same intervals, and the influence gradually weakened with age. Typically,  
Figure 19: Effect of laying moment on the difference of humidity at the top and bottom. Figure 20: Effect of laying moment on the moisture content of concrete panels. the humidity difference between panels constructed during the daytime was greater than those constructed during the nighttime. 3) There were significant differences in panel humidity and humidity differences across different paving times for the same age period, which could reach up to 3%. It could be concluded that the paving time indirectly impacted the internal humidity field of the panel through the environmental temperature, humidity, and solar radiation. At 7:00, the hydration reaction and the environmental factors almost reached their strongest state, resulting in a coupling effect that caused the panel humidity to drop faster and peak at a higher level.