Comparison of the Corrosion Potential of Calcium Chloride and a Calcium Nitrate Based on Non-Chloride Accelerator

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Title: Comparison of the Corrosion Potential of Calcium Chloride and a Calcium Nitrate Based on Non-Chloride Accelerator

Author(s): Jens Holm

Publication: Special Publication

Volume: 102

Issue:

Appears on pages(s): 35-48

Keywords: accelerating agents; calcium chlorides; calcium nitrates; concrete slabs; corrosion; corrosion tests; reinforced concrete; Materials Research

Date: 9/1/1987

Abstract:
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.