Influence of the C-S-H amount on [Cl^-]/[OH^-] ratio of simulated concrete SPS and the corrosion susceptibility of steel

Abstract

Two kinds of simulated concrete pore solutions (SPSs) were treated with different amounts of synthetic calcium silicate hydrate (C-S-H). The variation of the [Cl^-]/[OH^-] ratio in SPS was measured and the corrosion susceptibility of carbon steel in the SPS was investigated with potentiodynamic polarization, EIS and weight lose tests. The experimental results showed that for the SPS at pH 12.5, as the amount of C-S-H increases, the [Cl^-]/[OH^-] ratio increases thereby causing an increase in the corrosion susceptibility of the steel. While for the SPS at pH 9.7, with increasing C-S-H amount, the drop amplitudes of both [Cl^-]/[OH^-] ratio and steel corrosion rate first decrease and then increase, and a 3% C-S-H addition shows the best inhibition effect. XPS results demonstrate that after C-S-H treating in pH 12.5 SPS the [Fe³⁺]/[Fe²⁺] ratio in the film on steel surface is reduced while in pH 9.7 SPS the [Fe³⁺]/[Fe²⁺] ratio is increased. The different effects of the C-S-H amount on the two SPSs and the steel corrosion behavior result from the influences of C-S-H on the SPS pH, which is related to the composition of the SPS.

Keywords

C-S-H / concrete SPS / [Cl^-]/[OH^-] / corrosion / carbon steel

References

[1] Saremi M, Mahallati E. A Study on Chloride-Induced Depassivation of Mild Steel in Simulated Concrete Pore Solution[J]. Cement and Concrete Research, 2002, 32(12): 1915-1921.

[2] Moreno M, Morris W, Alvarez M G, et al. Corrosion of Reinforcing Steel in Simulated Concrete SPSs Effect of Carbonation and Chloride Content[J]. Corrosion Science, 2004, 46(11): 2681-2699.

[3] Plassard C, Lesniewska E, Pochard I, et al. Investigation of the Surface Structure and Elastic Properties of Calcium Silicate Hydrates at the Nanoscale[J]. Ultramicroscopy, 2004, 100(3–4): 331-338.

[4] Reardon E J. Problems and Approaches to the Prediction of the Chemical Composition in Cement/Water Systems[J]. Waste Management, 1992, 12(2–3): 221-239.

[5] Yuan Q, Shi C, De Schutter G, et al. Chloride Binding of Cement-Based Materials Subjected to External Chloride Environment-A Review[J]. Construction and Building Materials, 2009, 23(1): 1-13.

[6] Tang L, Nilsson LO. Chloride Binding Capacity and Binding Isotherms of OPC Pastes and Mortars[J]. Cement and Concrete Research, 1993, 23(2): 247-253.

[7] Hong SY, Glasser FP. Alkali Binding in Cement Pastes: Part I. The CSH Phase[J]. Cement and Concrete Research, 1999, 29(12): 1893-1903.

[8] Richardson I G. The Nature of the Hydration Products in Hardened Cement Pastes[J]. Cement and Concrete Composites, 2000, 22(2): 97-113.

[9] Viallis H, Faucon P, Petit J C, et al. Interaction Between Salts (NaCl, CsCl) and Calcium Silicate Hydrates (CSH)[J]. Journal of Physical Chemistry B, 1999, 103(25): 5212-5219.

[10] Tang YM, Miao YF, Zuo Y, et al. Corrosion Behavior of Steel in Simulated Concrete Pore Solutions Treated with Calcium Silicate Hydrates[J]. Construction and Building Materials, 2012, 30: 252-256.

[11] Tritthart J. Chloride Binding in Cement II. The Influence of the Hydroxide Concentration in the Pore Solution of Hardened Cement Paste on Chloride Binding[J]. Cement and Concrete Research, 1989, 19(5): 683-691.

[12] Suryavanshi AK, Scantlebury JD, Lyon SB. Mechanism of Friedel’s Salt Formation in Cements Rich in Tri-Calcium Aluminate[J]. Cement and Concrete Research, 1996, 26(5): 717-727.

[13] Hausmann DA. A Probability Model of Steel Corrosion in Concrete[J]. Materials Performance, 1998, 37: 64-68.

[14] Ghods P, Isgor OB, Brown JR, et al. XPS Depth Profiling Study on the Passive Oxide Film of Carbon Steel in Saturated Calcium Hydroxide Solution and the Effect of Chloride on the Film Properties[J]. Applied Surface Science, 2011, 257(10): 4669-4677.

[15] Ying W, Shi YX, Wei BM, et al. A XPS Study of Rebar Passive Film and Effect of Chloride Ions on It[J]. Journal of Chinese Society for Corrosion and Protection, 1998, 18(2): 107-112.

[16] Ghods P, Burkan Isgor O, Bensebaa F, et al. Angle-Resolved XPS Study of Carbon Steel Passivity and Chloride-Induced Depassivation in Simulated Concrete Pore Solution[J]. Corrosion Science, 2012, 58: 159-167.

[17] Huet B, L’Hostis V, Miserque F, et al. Electrochemical Behavior of Mild Steel in Concrete: Influence of pH and Carbonate Content of Concrete Pore Solution[J]. Electrochimica Acta, 2005, 51(1): 172-180.

[18] Liu LW, Hu Q, Peng JX, et al. The Relationship of CO2 corrosion of Carbon Steel with the Surface Film Structure in Neutral Aqueous Solution[J]. Materials Protection, 2001, 34(1): 6-7.