Sustainable and Bio-Based Coatings as Actual or Potential Treatments to Protect and Preserve Concrete

The durability of reinforced concrete strongly depends on the environment in which it is located; in any case, the concrete and the reinforcing bars it contains are constantly subject to slow deterioration processes. The protection of concrete structures is, therefore, essential to increase their service life, reducing the costs for their repair and maintenance. The commercial widely used coatings are mainly based on petroleum derivatives (i.e., resins, solvents): increased sensitivity and attention to human health and the protection of the environment pressed research to find alternatives to synthetic products, identifying safer materials with a low environmental impact to employ as protective coatings. In this review, new sustainable products already used or potentially suitable to act as protective treatments for concrete were analyzed and presented. These are natural (bio-based) or waste materials, in which the use of synthetic resins and hazardous solvents, for humans and the environment, are minimized, exploiting waste materials or by-products of other processes, if possible. The main properties and characteristics of these new products are illustrated, highlighting the potential advantages over commercial products also in terms of performance.