## 3 Early Behavior of Cement Concrete Pavement Panels Moisture Field
### Influence of Different Factors on the Moisture Field of Pavement Panels at Early Ages
#### 3.3.1 Effect of Cement Type  
It is well-established that different types of cement generate various amounts of heat during the hydration reaction, which affects the internal temperature of the panel and, thus, the humidity field inside the panel. This article selects five different types of Portland cement to analyze their impact on the humidity of cement concrete pavement panels. The cement components are shown in Table 2. Except for cement, all other materials, water-cement ratio, sand rate, etc., are the same in the concrete configuration. The silicate cement with different clinker fractions on the relative humidity at the top of concrete pavement panels \(h\) and the difference in humidity at the top and bottom of panels \(\Delta h\), as shown in Figures 8 and 9. Table 2 shows the composition of the cement clinker.  
Figure 7: Moisture distribution at 8 cm from the top of the plate.  
Comparing Figures 8 and 9, it can be observed that the effect of cement type on the humidity of concrete pavement slabs was minimal. The difference between the relative  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Number** & **C\({}_{3}\)S** & **C\({}_{3}\)A** & **C\({}_{2}\)S** & **C\({}_{4}\)AF** & **Specific Surface Area** \\  & **(\%)** & **(\%)** & **(\%)** & **(\%)** & **(\%)** & **(m\({}^{2}\)/kg)** \\ \hline Type I & 51.36 & 9.59 & 23.82 & 9.70 & 404 \\ \hline Type II & 53.28 & 9.31 & 21.80 & 10.59 & 408 \\ \hline Type III & 55.94 & 11.94 & 16.91 & 10.18 & 377 \\ \hline Type IV & 62.34 & 9.38 & 12.87 & 10.41 & 412 \\ \hline Type V & 52.34 & 3.89 & 24.93 & 13.87 & 357 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Mineral fraction content of cement clinker (mass %, %) and specific surface area.  
Figure 8: Effect of cement type on humidity at the top of the panel slab in Fuzhou.  
Figure 9: Effect of cement type on moisture difference.  
humidity h of the five types of cement on concrete pavement slabs was not more than 1%, suggesting that the type of cement has little effect on the moisture content of pavement slabs. The humidity of concrete pavement gradually increased along the depth direction, forming a positive humidity difference \(\Delta\)_h_, that is, the humidity at the top of the slab was generally smaller than the humidity at the bottom of the slab at the same age.  
We found that the effect of cement type on concrete humidity was mainly due to the difference in linker mineral content of the cement, which mainly affected the early internal temperature of the concrete panel due to the heat of hydration. However, since the internal and bottom humidity values of the early concrete were generally high and remained in a saturated state for a long time, the small difference in temperature had a relatively minor influence on the internal relative humidity of the panel.  
We adopted the environmental data from Fuzhou in July for the benchmark working conditions. This data showed fluctuations with age and was able to rapidly exchange humidity with the concrete on the top surface of the panel. As a result, the temperature and humidity at the top of the panel varied greatly, leading to a smaller difference in hydration heat produced by the type of cement in the range of the top of the panel and a smaller humidity difference \(\Delta\)h.