Preparation of Super-Hydrophobic Anti-Icing Coating for Asphalt Pavement and Evaluation of Its Anti-Icing Properties

Ice formed on asphalt pavement in winter reduces the skid resistance of the pavement surface, which would likely cause traffic accidents. To guarantee driving safety, a super-hydrophobic anti-icing coating on asphalt pavement was studied. First, suitable materials were selected, and the sol–gel preparation method was adopted; thus, a super-hydrophobic coating slurry was produced and coated on asphalt mixture slab specimens for evaluation. Second, the corresponding evaluation criteria, such as contact angle, rolling angle, and film formation of the super-hydrophobic coating, were measured and analyzed to determine the optimum composition and preparation technology. Third, the functional groups and micromorphology of the coating were investigated to analyze the formation and hydrophobic mechanisms. Finally, anti-icing indicators such as freezing delay time, freezing amount, and ice–pavement adhesion strength of the coating were adopted to evaluate their anti-icing properties. Meanwhile, the effect of coatings on skid resistance of asphalt pavement and their economy and practicality were also analyzed. Based on the test results and analysis, an optimum formulation ratio of super-hydrophobic coating slurry is recommended: silane coupling agent/high hydrogen silicone oil at 25%, deionized water/high hydrogen silicone oil at 130%, and tin catalyst/high hydrogen silicone oil at 20%. Microscopic experiments showed that the micro-nanostructure on the coating surface is fundamental to achieving super-hydrophobicity. The anti-icing effect test results showed that, with the formation of a super-hydrophobic coating on the pavement, the beginning freezing time of water on the pavement surface was delayed by 100–30 min, and the complete freezing time was delayed by 120–30 min, respectively, at $-2°\mathrm{C}$ to $-10°\mathrm{C}$. Compared with common pavement, the adhesion strength between ice and pavement surface coated with super-hydrophobic coating was reduced by more than 60% at $-2°\mathrm{C}$ to $-6°\mathrm{C}$. Even at $-8°\mathrm{C}\text{to}-10°\mathrm{C}$, 100 kPa reduction can be obtained. In addition, spraying the siloxane coatings has little effect on the skid resistance of the pavement. From these results, it can be concluded that the super-hydrophobic coating developed has excellent anti-icing properties and economic benefits, and it can prevent vehicle sliding and reduce ice removal labor.