Anti-corrosive superhydrophobic coatings for reinforcement protection: recycling of concrete garbage

• Published in: Anti-corrosion methods and materials Vol. 71; no. 5; pp. 514 - 528
• Main Authors: Wen, Xiaohu, Cao, Xiangkang, Ma, Xiao-ze, Zhang, Zefan, Dong, Zehua
• Format: Journal Article
• Language: English
• Published: Bradford Emerald Publishing Limited 12-07-2024; Emerald Group Publishing Limited
• Subjects: Cathodic protection; Cement; Chloride ions; Concrete; Construction; Contact angle; Corrosion; Corrosion prevention; Corrosion rate; Corrosion resistance; Corrosion tests; Design for recycling; Diffusion; Diffusion barriers; Diffusion coating; Diffusion rate; Electrochemistry; Electron microscopy; Ethanol; Fourier transforms; Galvanic corrosion; Garbage; Hydrophobic surfaces; Hydrophobicity; Infrastructure; Low carbon steels; Microparticles; Morphology; Nanoparticles; Nanotechnology; Rebar; Recycled materials; Recycling; Reinforcing steels; Silica; Silicates; Silicon dioxide; Slurries; Sodium; Sodium chloride; Sodium silicates; Spectrum analysis; Water uptake; X-ray spectroscopy; United States > US; Japan; Germany; Rebar corrosion; Water intake; Superhydrophobic coating; Concrete garbage; Chloride diffusion
• ISSN: 0003-5599; 0003-5599; 1758-4221
• DOI: 10.1108/ACMM-12-2023-2939

Purpose
The purpose of this paper was to prepare a ternary hierarchical rough particle to accelerate the anti-corrosive design for coastal concrete infrastructures.
Design/methodology/approach
A kind of micro-nano hydrophobic ternary microparticles was fabricated from SiO2/halloysite nanotubes (HNTs) and recycled concrete powders (RCPs), which was then mixed with sodium silicate and silane to form an inorganic slurry. The slurry was further sprayed on the concrete surface to construct a superhydrophobic coating (SHC). Transmission electron microscopy and energy-dispersive X-ray spectroscopy mappings demonstrate that the nano-sized SiO2 has been grafted on the sub-micron HNTs and then further adhered to the surface of micro-sized RCP, forming a kind of superhydrophobic particles (SiO2/HNTs@RCP) featured of abundant micro-nano hierarchical structures.
Findings
The SHC surface presents excellent superhydrophobicity with the water contact angle >156°. Electrochemical tests indicate that the corrosion rate of mild steel rebar in coated concrete reduces three-order magnitudes relative to the uncoated one in 3.5% NaCl solution. Water uptake and chloride ion (Cl-) diffusion tests show that the SHC exhibits high H2O and Cl- ions barrier properties thanks to the pore-sealing and water-repellence properties of SiO2/HNTs@RCP particles. Furthermore, the SHC possesses considerable mechanical durability and outstanding self-cleaning ability.
Originality/value
SHC inhibits water uptake, Cl- diffusion and rebar corrosion of concrete, which will promote the sustainable application of concrete waste in anti-corrosive concrete projects.