The interference of OH- ions in the potentiometric determination of free Cl- in cement paste pore solution

Title: The interference of OH- ions in the potentiometric determination of free Cl- in cement paste pore solution
Author(s): M.A. Climent, C. Antón, G. de Vera, A. Hidalgo, and C. Andrade
Paper category : conference
Book title: International RILEM Conference on Advances in Construction Materials Through Science and Engineering
Editor(s): Christopher Leung and K.T. WAN
ISBN: 978-2-35158-116-2
e-ISBN: 978-2-35158-117-9
Publisher: RILEM Publications SARL
Publication year: 2011
Pages: 655 - 562
Total Pages: 8
Nb references: 22
Language: English

Abstract: The determination of free chloride concentration in the concrete inner pore solution is highly desirable for monitoring and control of corrosion of reinforcing steel in concrete. The nature of the above mentioned electrolyte implies that low chloride concentrations have to be measured in presence of high concentrations of the interfering hydroxide ion. The results of this work show that the interference of hydroxide ions upon the potentiometric response of a chloride ionic selective electrode, in alkaline solutions, similar to those present in the cement paste or concrete pore electrolytes, can be adequately modelized through the Nikolskii-Eisenman model. The limit of detection of the ISE, due to the abovementioned interference, varies with pH. For the studied media, and in the pH range from 12.3 to 13.7, chloride concentrations below 2•10-4 to 7•10-3 molal cannot be accurately determined by potentiometric measurements, due to the OH- interference. Taking into account these limits of detection, the free Cl- concentrations able to depassivate the steel, can be adequately determined by potentiometric measurements with calibrated ISEs in the expressed pore solutions of Portland cement concretes, without significant influence of OH- interference. Nevertheless, this effect can prevent the adequate measurement of low free Cl- concentrations, below the corresponding limit of detection value.

Online publication: 2011-10-31
Publication type : full_text
Public price (Euros): 0.00