Evaluation of geopolymer coatings for corrosion protection of steel reinforcement in concrete

Abstract

Durability of concrete structure is an important issue global wide among civil engineering community. The major factor responsible for loss of durability and service life is corrosion of embedded steel in concrete. Among the several methods to prevent corrosion of steel in concrete, application of coating to steel reinforcement is an effective method of corrosion control. The formation of electrochemical cell within the concrete leads to the failure of embedded steel by two major mechanisms such as (i) by chloride attack and (ii) carbonation of concrete. These two important corrosion mechanisms must be controlled by appropriate coating on steel rebars. Several anticorrosive steel rebars coatings proposed in the literature have the following limitations. Even though the Epoxy coatings reported as an impermeable barrier to water, oxygen, and chlorides, achieving a perfect epoxy coating is very much difficult. Holidays and handling damage are always present on epoxy-coated bars and can lead to corrosion. In the case of galvanized steel reinforcement, the coupling of uncoated steel rebars with coated steel bars should be avoided to realize the long-term corrosion protection performance of galvanized steel rebar. If a stainless-steel bar comes into contact with an uncoated steel bar, the uncoated steel bar may corrode in an accelerated fashion. For enamel coated reinforcement, the bond between the concrete and the reinforcement increases while the permeability of the coating-concrete interface decreases which promotes resistance of reinforcement against corrosion. To improve the performance of the coating by revisiting their basic characteristics of proper adhesion, resistance to water, chemical, abrasion, friction, cost and finally easy application, the present work was mainlyfocused on the application of geopolymer based coatings for steel reinforcement in concrete to achieve long-term corrosion protection capability. As reported in the literature, the geopolymer coatings have many advantages and are summarize