Antonella Sardinella and Mariaenrica Frigione of University of Salento have provided an overview of the bio-based/sustainable materials proposed for the development of original coatings to protect concrete works in their recent review.
Traditional coatings involve the use of synthetic materials that are often toxic for human beings and the environment. Research is going on around the world for the development of new sustainable coatings made with bio-based or non-toxic materials using green technologies.
Following are qualities of a good coating:
- Chemical inertness against substrates.
- Good stability against acids, alkalis, UV radiations, heat, and oxidation.
- Permeability to water vapor (the underlying concrete must still “breathe”).
- Adequate adhesion to the substrate.
- Non-toxic and non-dangerous to the environment and human beings.
In the field of construction, the sustainable products proposed as potential protective coatings for concrete substrates can be divided into: (i) geopolymers and (ii) natural bio-based substances, such as agricultural waste, oil, wax, cellulose and others.
Geopolymers The low curing temperatures of geopolymers and their ability to be produced from a wide range of raw materials, including industrial waste (also known as secondary raw materials, or SRM), make them sustainable materials. Reusing (or recycling) solid waste, such as fly ash (FA), slag, and other active byproducts, can actually produce geopolymers by the alkaline activation of aluminosilicate precursors.
Coatings Based on Agricultural Waste Agricultural organic waste, i.e., products that are constantly generated, can be profitably exploited for different purposes, giving an economic value to the waste and reducing the costs of its disposal.
Vegetable Oil and Fatty Acids Recently, vegetable oils have been used in technologies meant to preserve a substrate (like concrete), which can be a viable substitute for synthetic materials and a sustainable approach. The chemical structure and film-forming properties of oil and its derivatives actually make them useful in this field.
Proteins Very recently, proteins have been proposed to develop coatings with good hydrophobic characteristics. Lysozyme, for instance, is composed of a microfiber network containing amyloid which, when applied to the surface of a metal, adheres to it and increases its resistance to corrosion.
Cellulose Cellulose, the most abundant natural polymer on earth, is a low-cost renewable resource: it is generally recognised as a potential candidate for the production of green superhydrophobic coatings.
Plant-Based Wax Coatings Starting from materials of vegetable origin dispersed in water, Morrissette et al. developed superhydrophobic self-cleaning coatings for different applications.
Advantages of These Coatings These are harmless to humans and the environment. They can be applied using the same techniques and methods as for traditional coatings, without additional costs. Waste materials can be used. Additionally, the studies carried out so far have especially highlighted the excellent protective properties offered by these materials, not considering any difficulties in the production processes and possible increased costs.
Challenges in Commercial Application Higher production costs, scale-up problems, demand for high quantities of bio-based raw materials, competition with food and feed for the supply of raw materials, technological barriers, and including industrial conversion for new productions are some of the barriers that slow down the introduction of these materials to the market.
You can refer below article for more details:
Antonella Sarcinella and Mariaenrica Frigione, Sustainable and Bio-Based Coatings as Actual or Potential Treatments to Protect and Preserve Concrete, Coatings 2023, 13(1), 44; https://doi.org/10.3390/coatings13010044
IMAGE FROM: The Concrete Beneath the M32 Flyover, Inset, Some of the Corrosion Found During Safety Checks.
