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Based on a studu of manu structures that have suff eredfrrom damage due to chloride-in duc ed corrosion of reinforced steel, it appears that even the more stringent limits on chloride now being proposed may be too lenient. Further, only determinations of total chloride may provide a basis for rea-sonable assurance against future corrosion.

SP102 As a designer you need the wealth of information presented in "Corrosion, Concrete and Chlorides -- Steel Corrosion in Concrete: Causes and Restraints," a compilation of 11 papers covering the corrosion phenomenon. Prompted by the nationwide corrosion problem with concrete, there have been extensive field and laboratory investigations into the specific phenomena that induce corrosion, methods for identifying the magnitude and extent of corrosion in structures, techniques for stabilizing corrosion once it has begun, and design of structures and concretes so that corrosion will not occur. Presenting an in-depth analysis into a variety of aspects dealing with corrosion, this state-of-the-art publication includes such topics as: the marked influence of chloride in causing corrosion, ways for controlling corrosion by using chloride-free accelerators, the reduction of chloride penetration through the use of pozzolanic blast-furnace slag as an admixture in concrete, and the conductive coating aspects of cathodic protection. "Corrosion, Concrete and Chlorides" provides important answers to a complex problem.

There was one point on which participants of the forum on The Chloride Issue: The New Limits at ACI’s annual convention last March in Denver agreed: We have a lot to learn about the influence of chloride ions in rein-forced concrete. Moderator Arthur L. Walitt, after being introduced by forum chairman Robert Henry, opened the forum by announcing that its purpose was to determine topics on which research is needed. A list of the topics which sur-faced during the forum accompanies this article. The forum, sponsored by ACI Committee 123, Research, opened with prepared presentations by Ted E. Webster, Bernard Erlin, and Richard Gaynor. Excerpts from Websters’s and Gaynor’s presentations appear here, followed by other forum highlights taken from an edited transcript

Usually concrete is an ideal environment for steel. Reinforcing Steel in most concrete structures is not subject to corrosioin. However, when salts (chlorides or sulfates) penetrate concrete and reach steel rebars, corrosion becomes active. Rust takes up a larger volume than the iron from which it is formed, developing pressure as great as 5000 psi within the concrete. This pressure causes cracking and spalling. Ultimately, failure occurs and major repair or replacement is needed. Once salts (from deicing, bleaching, marine environment, foreign aggregate etc.) contaminate concrete, corrosion progresses rapidly. Penetrants, sealants, surface coatings, and membrane barriers are useless in combatting the effects of salts already in concrete. The use of cathodicprotection to control corrosion on reinforcing steel in concrte is relatively reinforcing steel in concrete is relatively new. Although cathodic protection has been employed on pipelines, offshore cathodic protection has bee employed on pipelines, offshore platforms, ship hulls, buried tanks, etc. for more than 40 years, its use on concrete bridge decks was initiated only in the early 70's. Since the development of conductive coatings (1980-82) the effectiveness of cathodic protection has been enhanced.It has become easier to install and is now applicable to many different types of concrete structures (i .e ., docks; harbor facilities marine terminals; bridge substructures such as piers, pier caps, and beams; bulkheads; parking garages; industrial water and waste treatment plants; tunnels coastal buildings, etc. acceptance ofconductive coating cathodic protection continues to grow , new applications develop. This new form of an established technique holds extraordinary promise for large-scale preservation of concrete structures. (SP-102

A method for evaluation of the corrosion potential of chemical admixtures is presented. The method allows the direct measurement of the macrocell corrosion current between two layers of electrically connected reinforcing bars embedded in concrete. By ponding the specimens with chloride-free water, the potential of the chemical admixture to instigate corrosion can be evaluated. By using a chloride-containing ponding solution, in particular a 15% NaCl solution, it may be possible to assess the potential corrosion inhibiting effects of certain chemical admixtures. The test method was used to compare the corrosion activity in reinforced concrete slabs containing a normal dosage rate of calcium chloride, plain concrete and concrete containing two dosage rates of a multicomponent calcium nitrate based non-chloride accelerator. Only the slabs containing calcium chloride exhibited corrosion when ponded with tap water. When subjected to cyclic ponding with the salt solution, both the plain concrete and the concrete slabs containing the two dosage rates of the non-chloride accelerator exhibited corrosion. However, the slab containing the higher dosage rate of the non-chloride accelerator exhibited only 25% of the corrosion activity of the other two slabs. It is speculated that this reduction may be the result of corrosion-inhibiting effects of the non-chloride accelerator when it is added at sufficient rates.