1. Use of corrosion inhibitors
A schematic drawing of using corrosion inhibitor in repair concrete is shown in (b) of Table 1. The most commonly used corrosion inhibitor Is calcium nitrite, which is added to the repair concrete mixture as an additive. The inhibitor protects the steel from chloride-induced corrosion by reacting with ferrous Ions to repassivate the reinforcing steel surface. This method has good performance history and has been widely used, provided the nitrite and chloride ratio is In an appropriate range per manufacturer’s recommendations.
Another form of applying corrosion inhibitor Is to use a penetrating corrosion inhibitor (also known as surface- applied corrosion inhibitors or migrating corrosion inhibitors). These materials are applied over existing concrete surfaces and Intended to penetrate into the concrete. Effectiveness varies depending on the application condition and location, how the product is applied, the particular proprietary product, the actual concrete cover thickness, and the in-place concrete properties. Penetrating corrosion inhibitors remain controversial, with some studies demonstrating effectiveness while other studies show little or no effectiveness (EFC 38).
2. ProtectIve barrier coating or waterproofing membrane on concrete surfaces
Applying a coating or waterproofing membrane on the concrete surface, as shown in (c) of Table 1, is an effective means to reduce moisture and chloride ion penetration into concrete, thereby minimizing corrosion of the embedded reinforcement. There are different types of commercially available membranes, ranging from the commonly used polyurethane to polyurea and other systems such as a composite systems that uses an epoxy top coat with a polyurethane main coat (ACT 546.3k). These products should be selected with input from licensed design professionals and the material manufacturers. Appropriate maintenance of these barrier systems is required to prevent the penetration and accumulation of water in damaged areas.
3. ProtectIve coating on the exposed surfaces of the reinforcement
Zinc-enriched coating, epoxy AC1 364.3T), and cementltious products are commonly used coatings that can be applied over the reinforcing bars or tendons, as shown In (d) of Table 1. The coating forms a barrier, stopping the chloride ions, moisture, and oxygen from reaching the steel and isolates the steel electrically Irom the surrounding concrete, thereby reducing the corrosion potential.ACI 364.13T pdf download.