Coatings for improving the durability of concrete: State of knowledge, code provisions, and research advances in nanocomposite systems

Concrete elements made from portland and blended cements such as bridge decks, pavements, parking slabs, slabs-on-ground, and piers, often experience premature deterioration due to physical and chemical attacks, including freeze-thaw cycles, carbonation, external sulfate attack, and chloride-induced reinforcement corrosion. Hence, limiting fluid transport through concrete surfaces is essential for enhancing concrete durability. Surface treatments such as coatings that effectively protect against intrusive fluids are considered a viable approach of reducing maintenance and repair costs for both new and aging concrete elements. This review article critically examines the current provisions of international codes and guides with respect to concrete coatings, while synthesizing state-of-the-art on plain coatings and research advances on nanocomposite systems. Emphasis is placed on laboratory and field studies that evaluate their effectiveness against key durability issues, including frost damage, chloride, sulfates, carbonation, acid attack, and alkali–aggregate reactions. By highlighting recent advances and identifying knowledge gaps/limitations, this study aims to provide a practical resource for researchers and practitioners, and to support the broader understanding and implementation of nanocomposite coatings in practice, while informing potential updates needed to relevant codes and standards.