title: In situ measurement of Cl- concentrations and pH at the reinforcing steel/concrete interface by combination sensors.
abstract: This paper presents an in situ, nondestructive method of monitoring Cl- concentrations and pH values at the steel/concrete interface. The Ag/AgCl electrodes prepared by the electrochemical anodization and the Ir/IrO2 electrodes prepared by thermal oxidation in carbonate served as Cl- concentration and pH sensors, respectively. The potentiometric response of the Ag/AgCl electrode to the logarithm of Cl- concentrations ranging from 1 x 10(-4) to 2 M in saturated Ca(OH)2 solution simulating the inner electrolytic medium of concrete shows good linearity. The Ir/IrO2 electrode also exhibits an ideal Nernstian response in the range of pH 1-14. The Ag/AgCl and Ir/IrO2 electrodes were combined into a multiplex Cl-/pH sensor, and the sensor was embedded in concrete close to the steel/concrete interface to realize an in situ and long-term measurement of Cl- concentrations and pH values. The results indicate that the combined sensor is robust and sensitive enough to in situ measure Cl- concentrations and pH quantitatively at the steel/concrete interface, which is of indispensable importance to the study of corrosion and protection of the steel in concrete.
authors.affiliation: State Key Laboratory for Physical Chemistry of Solid Surfaces, Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, Fujian 361005, P. R. China. rgdu@jingxian.xmu.edu.cn
authors.forename: Rong-Gui
authors.initials: RG
authors.lastname: Du
authors.forename: Rong-Gang
authors.initials: RG
authors.lastname: Hu
authors.forename: Ruo-Shuang
authors.initials: RS
authors.lastname: Huang
authors.forename: Chang-Jian
authors.initials: CJ
authors.lastname: Lin
mesh_terms: D002712:Chlorides / Q000032:analysis*; D003252:Construction Materials; D004563:Electrochemistry; D004566:Electrodes; D006863:Hydrogen-Ion Concentration; D007495:Iridium / Q000737:chemistry; D012680:Sensitivity and Specificity; D012834:Silver / Q000737:chemistry; D012996:Solutions / Q000737:chemistry; D013232:Steel / Q000737:chemistry*; D013499:Surface Properties; D013997:Time Factors
chemical_list: D002712:Chlorides; D012996:Solutions; D013232:Steel; D012834:Silver; D007495:Iridium