Abstract

The leading cause of deterioration in reinforced concrete structures is the corrosion of steel bars embedded in concrete in the aggressive environment. This includes carbonation of concrete due to high CO2 concentration, chloride rich regions such as in marine environments from the sea water or airborne chloride and the corrosive industrial zones. In the recent past, nano-materials have risen to lime-light as one of the promising class of materials providing good corrosion protection to reinforced concrete structures. This class of materials include nano-silica, nano-alumina, carbon nano-tubes, nano-clays, graphene oxide, nano-coatings, nano-inhibitors as well as nano-particles of metal oxides. The mechanism of action for these nano-materials depends on the type of material used. For instance, some may refine the pore structure of concrete and reduce the permeability of concrete. Others may enhance the interfacial transition zone between the steel reinforcement bars and concrete. All this helps to limit the ingress of harmful substances including moisture, chloride ions, carbon dioxide and oxygen. Yet some other types of nano-materials may provide a protective layer or barrier through absorption, adsorption or reaction with the steel rebar surface and/or improvement in the passive layer. Nanomaterials have a multi-functional role and may also improve the mechanical properties along with the improvement in corrosion related durability. They may also influence the electrical resistance and may provide a self-healing behavior as well. Despite all the advantages, some challenges remain to be overcome such as dispersion, long term effect, impact on environment, scale and cost-benefit ratio. 

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