Superhydrophobic concrete coating with excellent mechanical robustness and anti-corrosion performances

In this study, an environmentally friendly superhydrophobic surface for concrete (S-concrete) with excellent mechanical robustness and anti-corrosion performances was put forward. By introducing geopolymer material, a novel inorganic gelling material act as binders to enhance the stability of the S-concrete, the suspension based on stearic acid (STA) modified by micro diatomaceous earth (DE) and nano alumina (Al2O3) were intensely attached to the substrate. The structure morphologies, chemical compositions, surface wetting behavior of this S-concrete were systematically investigated by SEM, XRD, FT-IR and wettability measurements. The results showed that the S-concrete coating was successfully constructed by achieving a desirable static contact angle of 159.1° and a small slide angle 4.5°. The S-concrete features Cassie-Baxter phase contacts, liquids repellency, anti-fouling and self-cleaning properties. The S-concrete exhibited excellent resistance to chloride corrosion, which was reduced by about 2 orders of magnitude compared to ordinary concrete. What is more, this S-concrete coating showed remarkable robustness against sandpaper abrasion and tape-peeling, while retaining its superhydrophobicity even suffering 200 abrasion cycles and 60 tape-peeling. The improved durable mechanical robustness and interfacial bonding force can be attributed to the cross-linked three-dimensional hierarchical structures formed by the combination of geopolymer material and embedded DE/Al2O3@STA micro-nanoparticles.