Influence of chemistry of chloride ions in cement matrix on corrosion of steel

Ha Won Song, Min Sun Jung, Chang Hong Lee, Sang Hyo Kim, Ki Yong Ann

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Abstract

To assess the resistance of steel against corrosion, mortar specimens were manufactured with a centrally located steel reinforcing bar. The mortars were formulated by combining ordinary portland cement (OPC) with a single supplementary cementitious material. The proportions were 30% pulverized fuel ash (PFA), 60% groundgranulated blast-furnace slag (GGBS), or 10% silica fume (SF) by weight. In addition, a pure OPC mortar was prepared. The mortar specimens contained chlorides from 0.0 to 3.0% by weight of binder to accelerate the corrosion process. Then, the corrosion rate was measured by a polarization technique to determine the chloride threshold level for corrosion in concrete. The buffering capacity of the cement matrix to a pH reduction was quantified by measuring the acid neutralization capacity. The suspension consisting of distilled water and paste powder was exposed to nitric acid to characterize a decrease in the pH. As a result, the chloride threshold level for corrosion was dependent on binders, with values of 0.74 to 0.93%, 0.48 to 0.59%, 0.29 to 0.44%, and 0.63 to 0.78% by weight of binder for OPC, 30% PFA, 60% GGBS, and 10% SF, respectively. It was found that an increase in the buffering capacity resulted in an increased threshold value, of which characteristics were used for a new representation of the chloride threshold. The threshold ratio of[Cl -]:[H+] for acidification to a pH value of 10 at corrosion accounted for 0.0063 and 0.0082, irrespective of binder type, at 1.0 and 2.0 mA/m2 (6.50 × 10-4 and 1.29 × 10-3 mA/in.2) of the corrosion rate, respectively.

Original languageEnglish
Pages (from-to)332-339
Number of pages8
JournalACI Materials Journal
Volume107
Issue number4
Publication statusPublished - 2010 Jul 1

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All Science Journal Classification (ASJC) codes

  • Civil and Structural Engineering
  • Building and Construction
  • Materials Science(all)

Cite this

Song, H. W., Jung, M. S., Lee, C. H., Kim, S. H., & Ann, K. Y. (2010). Influence of chemistry of chloride ions in cement matrix on corrosion of steel. ACI Materials Journal, 107(4), 332-339.