Abstract
The waterproof and thermal insulation property of foamed concrete is very important. In this study, the ultrafine fly ash (UFA)-based superhydrophobic composite coating was applied onto foam concrete. The UFA-based base coating that closely adhered to the concrete initially improved the waterproofness of the test block, and the silane coupling agent-modified UFA-based surface coating further achieved superhydrophobicity. The UFA on the coating surface and the asperities on the surface jointly formed a lotus leaf-like rough micro–nanostructure. The 154.34° water drop contact angle and 2.41° sliding angle on No. 5 coating were reached, indicating that it was a superhydrophobic surface. The water absorption ratios of the composite coating block were 1.87% and 16.6% at 4 h and 7 days, which were reduced by 97% and 75% in comparison with the original foam concrete. The compressive strength and heat conductivity coefficient after soaking for 4 h of the composite coating block were higher than 4.0 MPa and 0.225 W·m−1·K−1, respectively. The UFA-based superhydrophobic composite coating proposed in this study and applied onto foam concrete is simple and cheap, requires no precise instrument, and can be applied in a large area.
Highlights
Lotus leaves and water skippers are well-known for their superhydrophobic surface [1,2].The superhydrophobic surface has a contact angle greater than 150◦ and a sliding angle lower than 10◦ [3]
The ultrafine fly ash (UFA)-based superhydrophobic composite coating proposed in this study and applied onto foam concrete is simple and cheap, requires no precise instrument, and can be applied in a large area
The superhydrophobic composite coating applied onto the foam concrete included two layers, ultrafine fly ash (UFA)-based superhydrophobic surface coating and waterproof base coating
Summary
The superhydrophobic surface has a contact angle greater than 150◦ and a sliding angle lower than 10◦ [3] It has received extensive attention in the development of self-cleaning materials, and it has been studied in natural and artificial systems. These “lotus effect” structures possess waterproofing and self-cleaning [4], anticorrosion [5], antifog [6], and anti-ice properties [7]. Given these advantageous functions, the application of superhydrophobic materials in daily necessities, public buildings, national defense, and aviation have been extensively studied in applied research. These methods are applicable to base materials, such as metal, glass, Polymers 2020, 12, 2187; doi:10.3390/polym12102187 www.mdpi.com/journal/polymers
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