【文章內(nèi)容簡介】 te and its replacement with a repair material, even the best one, may result in accelerated rebar corrosion due to macrocell formation. The subject of this paper is also devoted to several confusing issues and attempts to establish the facts concerning the protection of reinforcement from premature corrosion in concrete repair, particularly that offered by corrosion inhibitors. How can we expect repaired concrete structures to be durable if the testing 8 methods, design and specification of corrosion protection methods, are relying on an inadequate assumption that electrochemistry in a repair system is similar to that occurring in new construction? There are significant differences between new construction and repair jobs。 there are often different factors leading to corrosion of reinforcement in new an repaired concrete structures and, therefore, in the methods of protection. It is not the intent of this paper to criticize existing methods and materials for additional protection of reinforcement in repairs, or to discuss in depth the merits or demerits of one protection system against another. The author can offer no panacea, or at least express a reasonably objective view of the right and wrong way to protect reinforcement in repaired structures. Much to our regret, this is not so. The problem is too plex because the existing knowledge is not sufficient to offer a panacea. The consequence and probability of repair failure due to the premature corrosion of the reinforcing steel is not necessarily a single simplistic solution as may be appropriate for newly constructed structures. Our success in the repair field may depend on our ability to resolve the controversies, to differentiate sense from nonsense. The nonsense will be abundant, no matter what we do: this field, due to the lack of proper education, is presently well positioned to import a lot of misconceptions。 any field where education and research are inadequate is going to have great trouble getting rid of the prevailing misconceptions. The author realizes that some statements will not be shared by many since it hits at the crux of the controversy. But in this case, much more than a hair, perhaps, divides concepts from misconcepts. 2. A glimpse of corrosion problem According to published data, steel reinforcement in concrete and in concretelike materials is, in general, well protected from corrosion by the alkaline nature of the cementitious matrix surrounding it. In general, this is true, it is protected, and it is not supposed to corrode. But such concrete in general may only exist as labcrete, in a small specimen. In the real world, reinforcing and prestressing steels are subject to corrosion due to carbonation and chloride ion attack. Steel reinforcement in concrete does not corrode because the surface of the steel in the alkaline environment is passivated。 steel in concrete corrodes 9 when its surface is depassivated during the manufacturing of the structure, or bees active during service. Corrosion is the electrochemical reaction, and the important factor affecting a corrosion cell is the difference in potentials of the metal. The driving force for current and corrosion is the potential development. Since the structure of steel and the contact layer of concrete are both heterogenous, the requirement for potential difference between the separate portions of the metal surface (the electrochemical inhomogeneity) is always satisfied. Concrete is a permeable material, where aggressive agents diffuse (micropermeability) through it and reach the reinforcing steel, causing its depassivation and corrosion, when water and oxygen are available. Corrosion by this mode however, is a relatively lengthy process. Concrete is a brittle material and always contains microcracks. When these microcracks bine in a work with macrocracks, the prevailing transport mechanism is not diffusion, it is the permeation of water and aggressive agents via water through the cracks to the reinforcement (macropermeability). Why enter through the closed door, when an open door is nearby? High permeability of concrete and other cementbased materials affected by cracking is truly responsible for the lack of durability. For corrosion to occur, it is necessary that both the passivating .lm on the steel is destroyed and that there exists a differential electrochemical potential within the steel–concrete natural protection of steel by the high alkalinity of cement matrix is disturbed due to the following reasons: chemical reaction between the products of hydration of cement and carbon dioxide which diffuses from the atmosphere (carbonation). Carbonation by diffusion is a very lengthy process: approximately 1 mm of concrete cover carbonates in a year. Cracks in the concrete, on the other hand, allow carbon dioxide easy permeation through the concrete cover, and carbonation occurs rapidly. level. Chloride ions may perate into the concrete due to one of three processes: diffusion due to a concentration gradient, absorption from salt solutions form, and/or by flow of the solution through the cracks. The differential electrochemical potential may develop due to the dissimilarities in the chemical environment of steel, such as the result of nonuniformed carbonation, the variation in the rate of peration of chlorides, 10 moisture, oxygen, etc. Reinforcing steel in the variety of a crack starts to corrode from a localized depassivation of steel because of the weakened steelcementmatrix conta