## 4 Results and Discussion
### Effect of Deicing Salt Concentration  
To investigate the impact of the deicing salt concentration on the pavement surface temperature and the onset of icing, this study examined various combinations of wind speed and air temperature alongside deicing salt concentrations of 0%, 20%, 40%, 60%, and 80%. The deicing agent used in the experiment is sodium chloride, which is the most widely used deicing salt for roads due to its low cost, effective freezing point depression, and easy availability. In the experiment, the concentration of the deicing salt was defined by the ratio of the mass of salt applied to the surface to the mass of water present on the runway. The key findings are as follows. 1. Effect of Deicing Salt Concentration on Pavement Surface Temperature  
During the initial 10 min of the experiment, the effect of varying the deicing salt concentrations on the pavement temperature was minimal. However, as the time progressed--especially after 30 min--the pavement surface temperature with the deicing salt was significantly lower than without it, with the cooling effect becoming more pronounced at higher concentrations of deicing salt. For example, as shown in Figure 9(a), at an air temperature of \(-10\)\({}^{\circ}\)C and a wind speed of 2 m/s, the pavement surface temperature decreased by 1.8 \({}^{\circ}\)C and 4.63 \({}^{\circ}\)C for the 20% and 80% salt concentrations, respectively, compared to the absence of deicing salt. In contrast, Figure 9(b) indicates that at a lower air temperature of \(-20\)\({}^{\circ}\)C and higher wind speed of 6 m/s, the temperature drops were 1.66 \({}^{\circ}\)C and 6.83 \({}^{\circ}\)C for the 20% and 80% salt concentrations, respectively. Figure 10: _Cont._  
Effect of Deicing Salt Concentration on Icing Onset Time  
Figure 11 illustrates the icing onset time under varying deicing salt concentrations and wind speeds, while Figure 12 depicts the icing onset time with different salt concentrations and air temperatures. The experiment revealed that increasing the concentration of deicing salt significantly delayed the icing onset time. This effect was especially pronounced at lower air temperatures (\(-20\)\({}^{\circ}\)C) and higher wind speeds (6 m/s). For example, as shown in Figure 11a, at \(-3\)\({}^{\circ}\)C, increasing the salt concentration from 0% to 20% delayed the icing onset time by 221% to 543%, extending it by up to 76 min. Similarly, as indicated in Figure 11f, at \(-20\)\({}^{\circ}\)C, the delay ranged from 2252% to 6700%, extending the time by up to 67.55 min. Impact of Deicing Salt Concentration Under Different Conditions  
This study found that when the air temperature was constant, lower wind speeds result in a more significant effect of the deicing salt concentration on the icing onset time. For instance, as shown in Figure 11a, at \(-3\)\({}^{\circ}\)C and a wind speed of 2 m/s, increasing the salt concentration from 0% to 20% extended the icing onset time by 28 min and 13 s, representing a 256.6% increase. In contrast, at a wind speed of 6 m/s, the time was extended by 24 min and 18 s, reflecting a 303.7% increase. Under varying air temperatures, a higher deicing salt concentration also led to significant extensions in the icing onset time, as illustrated in Figure 12. Lower air temperatures exhibited a more pronounced effect, particularly at higher wind speeds. For example, at a wind speed of 2 m/s and an air temperature of \(-20\)\({}^{\circ}\)C, increasing the salt concentration from 0% to 20% extended the icing onset time by 30 min and 15 s, leading to a remarkable 1008.3% increase.