RESEARCH ARTICLE

Potentiometric determination of free chloride in cement paste - An alternative method for low-budget laboratories

D.J. Delport^{I, *}; S.S. Potgieter-Vermaak^{II, III}; R.I. McCrindle^IV; J.H. Potgieter^V

^IDepartment of Chemical & Metallurgical Engineering, Tshwane University of Technology, Private Bag X680, Pretoria, 0001 South Africa
^IIDivision of Chemistry & Environmental Science, Manchester Metropolitan University, M1 5GD, UK
^IIIMolecular Science Institute, School of Chemistry, University of the Witwatersrand, Johannesburg, South Africa
^IVDepartment of Chemisty, Tshwane University of Technology, Private Bag X680, Pretoria, 0001 South Africa
^VChemistry and Materials Division, School of Biology, Chemistry and Health Sciences, Manchester Metropolitan University, All Saints Campus, Oxford Road, Manchester, Ml 5GD, UK

ABSTRACT

Corrosion of rebar in concrete is commonly associated with, and to a large degree influenced by, the free chloride concentration in the pore water. The amount of chloride in concrete is important because chloride can promote corrosion of steel reinforcement when moisture and oxygen are present. A potentiometric procedure that makes use of direct measurement with a chloride ion selective electrode has been developed to analyze free chloride in the pore water extracted from cement paste.¹⁶ The accuracy and reliability of this analytical technique has been checked against a certified reference material, Merck sodium chloride solution. Confidence levels (CL₀₉₅), of 0.03 and relative standard deviations of 0.2 % for chloride were determined for ordinary Portland cement (OPC) chloride binding capacity.

Keywords: OPC, free chloride, potentiometry

Full text available only in pdf format.

References

1 L. Tang and L. Nilsson, Cem. and Concr. Res., 1993, 23, 247-253.         [ Links ]

2 A.K. Suryavanshi, J.D. Scantlebury and S.B. Lyon, Cem. Concr. Compos. 1998, 20(3): 263-269.         [ Links ]

3 O. Kayali and B. Zhu, Construe. and Build. Mat, 2005.19: 327-336.         [ Links ]

4 K. Tuutti, Swedish Cement and Concrete Research Institute (CBI), 1982,4, 82, 263.         [ Links ]

5 M. Pourbaix, Pergamon Press, Oxford, UK, 1966.         [ Links ]

6 T.C. Rilem, Mat. and Struct., 2002. 35, 583-585.         [ Links ]

7 Q. Yuan, C. Shi, G. deSchutter, K. Audenaert and D. Deng, Construc. and Building Mat. 2009. 23: 1-13.         [ Links ]

8 J. Tritthart, Cem. and Concr. Res., 1989,19, 586-594.         [ Links ]

9 S. Diamond, Cem. and Concr. Aggregates, 1986, Chloride concentrations in concrete pore solutions resulting from calcium and sodium chloride admixtures. 8: 97-107.         [ Links ]

10 A.I. Vogel, A Textbook of Quantitative Inorganic Analysis, Longman, London, 1994.         [ Links ]

11 R. Jenkins and J.L. de Vries, Practical X-ray Spectrometry, Philips Technical Library, Eindhoven, 1967.         [ Links ]

12 M. Poznic,R. Gabrovsek and M. Novic, Cem. and Concr. Research, 1998, 29, 441-443.         [ Links ]

13 J. Koryta, Anal. Chim. Acta., 1972, 61, 329-411.         [ Links ]

14 A.M. Climent, E. Viqueira, G. de Vera, and M.M. Lopez-Atalaya, Cem. and Concr. Res. 1999, 29, 893-898.         [ Links ]

15 A.K. SuryavanshiI, J.D. Scantlebury, and S.B. Lyon, Cem. and Concr., 1996, 26, 263-281.         [ Links ]

16 J.H. Potgieter, D.J. Delport, S. Verryn, and S.S. Potgieter-Vermaak, S. Afr. J. Chem., 63, 2011, 108-114.         [ Links ]

Received 18 February 2011
Revised 18 November 2011
Accepted 30 November 2011

Submitted by invitation to celebrate 2011 the 'International Year of Chemistry'.
* To whom correspondence should be addressed. E-mail: delportd@tut.ac.za