In-Situ Detection of Chlorides in Capillary Water of Cementitious Materials with Potentiometric Sensors

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Title: In-Situ Detection of Chlorides in Capillary Water of Cementitious Materials with Potentiometric Sensors

Author(s): F. Svegl, K. Kalcher, and M. Kolar

Publication: Special Publication

Volume: 235

Issue:

Appears on pages(s): 241-256

Keywords: Ag/AgCl electrode; chloride ingress; concrete durability; corrosion; potentiometric sensors; reinforced concrete

Date: 3/22/2006

Abstract:
Among the harmful substances carried into reinforced concrete by water, none is potentially more damaging than chloride ions, which destroy the passivity layer on steel in alkaline environment leading to corrosion processes of reinforcement and loss of durability. In this work we present direct potetiometric measurements of chloride ions in the pore water of mortar samples by using Ag/AgCl indicator electrodes. The long-term stability of electrodes in highly alkaline environment of cementitious materials and selectivity to chloride ions were improved with the deposition of polymer membrane consisting of polyvinyl chloride matrix and chloride ionophore. The chloride ingress experiments were performed on cylindrical mortar samples with over 50 sensors embedded into the solid body of the sample. The ingress of dissolved chloride ions into the mortar sample was monitored for more than six months. The concentration profiles of chlorides at different places in the sample were determined and used for the evaluation of diffusion processes of chlorides through the pores of the microporous matrix.