Development and performance analysis of a modified polyurea hydrophobic coating for improving water conveyance efficiency in concrete channel linings

The water conveyance capacity of a channel depends heavily on the roughness coefficient of the flow surface, which is challenging to maintain in concrete linings due to construction limitations, skill variability, and water erosion. Applying surface coatings has proven effective in reducing roughness, improving conveyance efficiency, and ensuring durability. This study aims to develop and evaluate a novel hydrophobic coating, the modified polyurea hydrophobic coating (MPHC), to overcome the performance limitations of traditional coatings. The MPHC was formulated using polyurea, polydimethylsiloxane, and silicon dioxide in a specific mass ratio and was designed to combine strong adhesion, high hydrophobicity, and excellent durability. The coating’s performance was assessed through contact angle measurements, tensile bond strength tests, and environmental pretreatment evaluations, including immersion, heat resistance, and freeze-thaw cycling. Experimental results reveal that the MPHC achieves a surface contact angle of 131.2°, demonstrating strong hydrophobicity. The coating incorporates a “binary structure” formed by the combination of polydimethylsiloxane and microsilica powder, which creates a hydrophobic-rough surface. This structure minimizes the flow-solid interface area and adhesion, enhancing drag reduction performance. The bond strength of the MPHC decreases by only 0.1 MPa compared to unmodified polyurea, demonstrating that polydimethylsiloxane minimally affects bonding performance. Furthermore, durability tests—including immersion, high-temperature exposure, and freeze-thaw cycles—show no significant deterioration in either the contact angle or bond strength, confirming the coating’s robustness. Drag reduction tests conducted on channel model linings demonstrate that the MPHC reduces the roughness coefficient by 10.0–11.6% compared to ordinary concrete and by 7.4–7.5% compared to ordinary polyurea coatings. In conclusion, the findings of this study highlight the suitability of the MPHC for channel concrete linings. Its superior hydrophobicity, durability, and drag reduction performance make it a promising solution for improving the water conveyance efficiency of concrete-lined channels.