Effect of concrete alkalinity on chloride ion concentration at the colour change boundary during AgNO3 colorimetric measurement

Title: Effect of concrete alkalinity on chloride ion concentration at the colour change boundary during AgNO3 colorimetric measurement
Author(s): C. Shi, Q. Yuan, F. He
Paper category : conference
Book title: International Conference on Microstructure Related Durability of Cementitious Composites
Editor(s): W. Sun, K. van Breugel, C. Miao, G. Ye and H. Chen
Print-ISBN: 978-2-35158-065-3
e-ISBN: 978-2-35158-084-4
Publisher: RILEM Publications
Publication year: 2008
Pages: 1389 - 1397
Total Pages: 9
Nb references: 9
Language: English

Abstract: This paper investigates the effect of concrete alkalinity on chloride ion concentration at the colour change boundary during AgNO3 colorimetric measurement. Equivalent silver nitrate solution (i.e. Ag+ = Cl-) was added to mixed NaCl+NaOH solutions with different concentrations, then the amounts of precipitated AgCl and Ag2O were determined by chemical analyses, and the color of the precipitated products was determined. Results showed that the amount of AgCl formed decreased linearly as OH- concentration or OH- to Cl- ratio of the solution increased, which are in agreement well with the theoretically calculated values.
The colour of the precipitated reaction products changed from silver at low pH values to dark brown at high pH values. When 0.035 and 0.1 mol/L AgNO3 solutions were sprayed onto freshly split surface of mortar specimens after NT Build 492 testing, it was found that the colour changed depth using 0.035 mol/L AgNO3 was larger than that using 0.1 mol/L AgNO3.
Measured Cl- concentrations at the colour change boundary increased as the alkalinity of concrete increased.

Online publication: 2009-06-09
Publication type : full_text
Public price (Euros): 0.00