# Study on Microwave Deicing of Carbon-Fiber-Modified Concrete under Multi-Factor Coupling Effect
## 3 Results
### Effect of Microwave Irradiation Height on Deicing  
Based on the above ice-free test, 0.6 CFC3 specimens were selected for deicing tests under microwave irradiation at different heights (10 mm, 20 mm, 40 mm and 60 mm). The ice thickness on the upper surface of the specimens was maintained at 10 mm, and the temperature increase curves and deicing effects were obtained at four heights. The results are shown in the Figures 7-9. Regardless of the height, the inflection point of the temperature increase curve is about 50 s, i.e., the water layer is completely formed, indicating that the height does not affect the time to form a complete water layer on the concrete pavement. Because the time to form a water layer on concrete is considerably affected by the absorption and heat performance of water, the height has a considerable influence on the absorption and heat performance of carbon fiber concrete but has little influence on the absorption and heat performance of water. As the height increases, the temperature gradually increases, reaching its maximum value when the height is 40 mm. In the first half of the temperature increase curve, the temperature change rule under the height of 20 mm is similar to that under the height of 40 mm. However, after 85 s, the temperature at the center point (T\({}_{0}\)) on the surface of the specimen with a height of 40 mm increases significantly, indicating that the deicing efficiency is better at a height of 40 mm. There was no obvious deicing effect on the highly irradiated specimen surface, especially with a microwave source height of 40 mm. When the temperature was increased to 34 \({}^{\circ}\)C, ice did not form, indicating a good deicing effect on the 0.6 CFC3 specimen and a more horizontal temperature transfer, as opposed to vertical heating of the ice. The temperature change results obtained in this experiment are similar to those reported by [PERSON] et al. with respect to heating height in absorbance tests [14] for deicing of carbon fiber concrete on the basis of a microwave frequency of 2.45 GHz. Figure 5: Temperature increase curve at the center point (T\({}_{0}\)) of modified concrete samples with different carbon fiber contents and lengths. Figure 6: Temperature increase rate at the center point (T\({}_{0}\)) of modified concrete with different carbon fiber contents and lengths. For further comparison, the deicing area was measured at different heights. With increased height, the shape of the deicing area gradually changed from a dumbbell shape to an oval shape; the width of the center line gradually increased; the width of the left and right semicircles gradually decreased; and the ratio of the width of the left and right semicircles to the width of the center line gradually decreased. When the height is 10 mm, the width of the middle line is 6.39 cm, the width of the left semicircle is 12.06 cm and the width ratio is 1.89. When the microwave source trumpet is 20 mm, the ratio decreases to 1.51. When the height of microwave source trumpet is 40 mm, the ratio decreases to 1.08, and the width is almost the same. When the height is 60 mm, the width of the center line is larger than the length of the center line for the first time, and the absorbing heating surface is oval. Therefore, from the perspective of shape, at a microwave source trumpet height of 40 mm, the shape of the deicing area approximates a rectangle under the irradiation of multiple microwave emission sources, resulting in an improved arrangement of the deicing area. Figure 8: Deicing effect of specimens at different heights. Figure 7: Temperature curves of specimens at different heating heights over time. Figure 9: Temperature increase rate at the center point (T\({}_{0}\)) of concrete specimens with different carbon fiber contents and lengths. position. With increased height, the deicing area first increases first and then decreases.