Protective coatings for exposed concrete surfaces have become essential elements in construction projects, especially in harsh environments or for concrete surfaces subjected to any kind of harmful attack. Ingress of moisture into concrete may cause corrosion of steel reinforcement inside it which is harmful to concrete. Durability of even good quality concrete can suffer due to persistent chemical attacks, abrasion, freezing & thawing etc., if left unprotected. That’s where the relevance of protective coatings come into the picture. These coatings pose as shields between the concrete surface and the sorrounding environment and protect concrete from harmful affects.
Protective coatings are usually made of resins, pigments and solvents. There are solventless protective coatings as well. It is the resin component that provides the protection while pigments impart colours. Protective properties of coatings are sometimes further modified by adding suitable fillers depending on requirements. Some examples of protective coatings are epoxy coatings, polyurethane (PU) coatings, vinyle coatings, polyester coatings and so on.
Protective coatings are quite useful for varieties of structures such as bridge decks, abutments, heavy-duty industrial floors or industrial concrete surfaces subjected to chemical attacks or harsh environment, water & waste water tanks, marine structures, manholes, masonry work, dams, retaining walls, piles and any other structure likely to come in contact with adverse environmental or climatic conditions.
Desired characteristics or qualities of protective coatings may vary from work to work. The requirements of protective coatings for marine environment may not be exactly the same for protective coatings to be used in a bridge and so on. Some important quality requirements of protective coatings for various environments are:
the protective coating should be durable.
The coating material should have waterproofing or hydrophobic properties.
It should develope strong and lasting adhesion with the concrete surface.
It should provide relentless protection against chemical and other attacks.
The coating material should have good thermal resistance, ie it should be able to withstand high temperature and fluctuations in temp.
The coating material should have good resistance to impact and abrasion.
It should have good resistance against constant exposure to UV radiations from the sun.
It should be resistant to salts (e.g. chlorides, sulphates etc.), acids, alkalis, oils, grease etc.