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Home > Publications > International Concrete Abstracts Portal
Showing 1-5 of 12 Abstracts search results
Document:
SP102-10
Date:
September 1, 1987
Author(s):
B. Erlin and W. Hime
Publication:
Symposium Papers
Volume:
102
Abstract:
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.
DOI:
10.14359/9986
SP102-01
William G. Hime and Bernard Erlin
The wide variety of disciplines involved with the corrosion of steel in concrete has caused difficulties in communication. Each discipline has its own terminology; at times two disciplines use conflicting terms or explanations for the same phenomenon. This paper addresses some areas of such confusion, and presents chemical mechanisms to explain half-cell potentials and causes for chloride-induced corrosion. Examples of such corrosion are presented.
10.14359/1631
SP102-02
John Fraczek
Corrosion of steel in concrete proceeds at a far greater rate in the presence of chloride ions. Most researchers agree that chloride ions act as an essential part of the corrosion cell by 1) lowering the pH of the concrete pore water in contact with the steel, thereby dissolving the passive oxide film on the steel surface, or 2) penetrating the film to react with and trans-port the metallic iron into the electrolyte. In the latter process, the resulting iron chloride complex ion combines with hydroxyl ions to form ferrous hydroxide in solution and lower the pH. This, in turn, thins out the oxide film and speeds penetration of chloride ions. Eventually the continuing cor-rosive action results in a pit. To initiate corrosion, a threshold concentration of chloride is needed in excess of the amount immobilized by reaction with tricalcium aluminate in the cement. Investigation of the chloride ion content in concrete adjacent to corroding reinforcing steel shows the concentration to be 1.0 to 1.4 lb of chloride ion per cubic yard of concrete (0.59-0.83 kg/m3).
10.14359/1633
SP102-03
Philip A. Smith
Effects of two non-chloride accelerating agents -- sodium thiocyanate and calcium nitrate -- in time to achieve initial set of two brands of Type I cement were determined at 70 F (21 C) and 40 F (4 C). Results with these two non-chloride accelerators were compared with results with calcium chloride, the conventional accelerator. Tests show:Low or moderate dosages of the two non-chloride accelerators can reduce time to achieve initial set by l-2 hr.- Any one of the three accelerators may be more effective with one ce-ment than with another cement having similar setting characteristics without accelerators In general, all three of the accel-erators are more effective at 40 F than at 70 F.
10.14359/1635
SP102-04
Jens Holm
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.
10.14359/1637
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