On the corrosion risk presented by chloride bound in concrete

In previous work the influence of the solid phases of cement hydration on the pore solution chemistry during corrosion initiation has been discussed. It was noted that, because a fall in local pH is necessary for stable pits to develop on the passive steel, much of the chloride bound in concrete may participate in the process of corrosion initiation. At least two phases in hydrated ordinary Portland cement (OPC) will release such bound chloride before the pH falls to 11. In this work, these studies have been extended to include OPC blended with 10% calcium aluminate cement (CAC) and sulphate resisting Portland cement (SRPC). Evidence of a third phase that releases bound chloride was uncovered. Once again the data confirms that most of the bound chloride will be released by a relatively small reduction in pH. The release of chloride at such a high pH value compared to that required to sustain passive film breakdown suggests that the corrosion risk presented by bound chloride may be very similar to that presented by free chloride in concrete.

[1]  C. Hansson,et al.  The Threshold Concentration of Chloride in Concrete for the Initiation of Reinforcement Corrosion , 1990 .

[2]  O. A. Kayyali,et al.  THE C1-/OH- RATIO IN CHLORIDE-CONTAMINATED CONCRETE - A MOST IMPORTANT CRITERION , 1995 .

[3]  P. Francis,et al.  The Use of Synthetic Environments for Corrosion Testing , 1988 .

[4]  G. Glass,et al.  A method of ranking the aggressive nature of chloride contaminated concrete , 2000 .

[5]  F. P. Glasser,et al.  Friedel’s salt, Ca2Al(OH)6(Cl,OH)·2H2O: its solid solutions and their role in chloride binding , 1998 .

[6]  Stuart Lyon,et al.  CORROSION OF REINFORCEMENT STEEL EMBEDDED IN HIGH WATER-CEMENT RATIO CONCRETE CONTAMINATED WITH CHLORIDE , 1998 .

[7]  P B Bamforth,et al.  AN INTERNATIONAL REVIEW OF CHLORIDE INGRESS INTO STRUCTURAL CONCRETE , 1997 .

[8]  G. Glass,et al.  The inhibitive effects of electrochemical treatment applied to steel in concrete , 2000 .

[9]  P. Balkwill,et al.  Simulating the Pitting Corrosion of Steel Reinforcement in Concrete , 1988 .

[10]  G. Glass,et al.  Corrosion inhibition in concrete arising from its acid neutralisation capacity , 2000 .

[11]  C. Andrade,et al.  Chloride threshold values to depassivate reinforcing bars embedded in a standardized OPC mortar , 2000 .

[12]  C. Page,et al.  Corrosion of reinforcement in concrete , 1990 .

[13]  G. T. Burstein.  Revealing corrosion pits , 1991, Nature.

[14]  G. Glass,et al.  The influence of chloride binding on the chloride induced corrosion risk in reinforced concrete , 2000 .

[15]  G. Glass,et al.  Backscattered electron imaging of the steel–concrete interface , 2001 .

[16]  Nick R. Buenfeld,et al.  Differential acid neutralisation analysis , 1999 .

[17]  G. Glass,et al.  The presentation of the chloride threshold level for corrosion of steel in concrete , 1997 .

[18]  Adam Neville,et al.  Chloride attack of reinforced concrete: an overview , 1995 .

[19]  Nick R. Buenfeld,et al.  The participation of bound chloride in passive film breakdown on steel in concrete , 2000 .

[20]  Z. Szklarska‐Śmiałowska,et al.  Pitting Corrosion of Metals , 1986 .

[21]  T. Yonezawa,et al.  Pore Solution Composition and Chloride Effects on the Corrosion of Steel in Concrete , 1988 .