Multifunctional superhydrophobic composite with mechanochemical stability for concrete protection

Chemical or electrochemical corrosion of the concrete-based facilities causes potential safety hazards. Endowing the concrete with a commercial superhydrophobic coating with designed surface topography and chemical composition is an effective way to prevent the corrosion of the internal rebars. Although several methods have been adopted to combat the corrosion problem, developing an equipment-free, low-cost and scalable strategy for fabricating a robust superhydrophobic coating on the concrete surface is still a challenge. In this work, a robust superhydrophobic epoxy fixed corundum-silica-polydimethylsiloxane (ECSP) composite is fabricated as the concrete modification coating through an "armour" protection methodology via a facile and low-cost dip-coating process. The as-prepared ECSP composite consists of corundum microparticles (MPs) confined in the epoxy (EP) adhesive layer and silica nanoparticles (SiO2 NPs) modified with a low-surface-energy coating. The corundum MPs with high rigidness and hardness function as a robust, protective "armour" structure, while the polydimethylsiloxane-modified SiO2 NPs reside within the "armour" structure to provide superhydrophobicity. Benefitting from the armoured structure, the ECSP composite coated concrete exhibits an excellent robustness under various harsh conditions including mechanical abrasion, knife scratching, tape-peeling treatment, water jetting, UV irradiation, temperature treatment and chemical corrosion. Importantly, the ECSP composite coating successfully prevents the concrete (with a rebar in it) from the chemical and electrochemical corrosion. The corrosion current density (4.8 x 10(-6) A.cm(-2)) of the ECSP coated concrete is two orders of magnitude lower than that of the unprotected concrete (1.17 x 10(-4) A.cm(-2)), exhibiting its excellent corrosion resistance. Besides, the superhydrophobic ECSP composite coating can retard the formation of ice on the concrete surface at the temperature of -20 degrees C, exhibiting good anti-icing performance. This work opens a new avenue for the fabrication and application of the multifunctional superhydrophobic coating for concrete protection.