Smart fluorine-free nanocomposite protective coatings for mitigating water ingress and service life extension of fly ash concrete

Concrete, renowned for its robustness and longevity in the construction sector, is susceptible to strength degradation from water infiltration. One of the inherent drawbacks of concrete is its susceptibility to environmental causes like water infiltration, freeze-thaw cycles, and chemical attacks. Superhydrophobic coatings with self-cleaning, corrosion resistance, drag-reduction, anti-fogging, and anti-icing properties are making them suitable for various application fields. Developing functional, fluorine-free superhydrophobic surfaces is essential to comply with environmental regulations and safeguard architecture. The present study demonstrates the effectiveness of a novel, durable, fluorine-free superhydrophobic nanocomposite coating based on Al 2 O 3 nanoparticles and methyltrimethoxysilane (MTMS) for protecting fly ash concrete surfaces. The coating was prepared through a simple sol-gel method and spray coating technique was used to apply it. This created hierarchical micro or nanostructures with low-surface-energy methyl groups, which in turn lead to an increased water contact angle (CA) of 153° and a decreased sliding angle (SA) of 6°. Synthesis and surface modification of the fluorine-free nanocomposite coating were conducted through comprehensive characterization techniques, including contact angle measurements, particle size analysis, SEM, XRD, FTIR and XPS. Performance evaluation through water absorption, surface penetration, wet–dry cycling, acid resistance, droplet impact, and abrasion tests demonstrated significantly improved durability and mechanical robustness compared to untreated samples. The coating maintains stability under harsh environmental conditions, indicating strong adhesion and long-term effectiveness. These findings can support the preservation of the durability and efficiency of different fly ash concrete materials over time.