Corrosion inhibition of steel reinforcements in seawater sea sand concrete by alkali-activated slag based coatings

Chloride-induced corrosion is a severe problem for reinforced concrete structures exposed to marine environments. In such situations, the surface coating acts as a cost-effective means to inhibit the corrosion of steel reinforcement. In this work, the effectiveness of alkali-activated slag (AAS) coatings in inhibiting corrosion of steel reinforcement in seawater sea-sand concrete was assessed through a series of electrochemical tests. Two different types of AAS coatings (i.e., with and without latex polymer modification) were designed in addition to a conventional cement coating (i.e., for comparison purpose). It was found that AAS coatings are effective in preventing steel corrosion in both normal strength seawater sea sand concrete (NSSC) and ultra-high performance seawater sea sand concrete (UHP-SSC), which simulate a chloride contaminated concrete environment in short-term exposure. However, the protectiveness of conventional cement coating was valid only in UHP-SSC. The above protection effects were confirmed under both the fresh and hardened states of SSC, which were attributed to the coating-induced prepassivation of steel reinforcement and the coatings' chloride barrier effect. The corrosion inhibition mechanisms of the coated steel reinforcements in NSSC and UHPSSC are further elaborated.