Development of Imbedded Sensors and Techniques for Chloride Determinations in Steel Reinforced Bridge Deck Structures

Abstract

Chloride ions, found in deicing chemicals, penetrate concrete causing corrosion of reinforcing steel. Corrosion in bridge deck and post-tensioned structures poses a great safety risk to the public. Furthermore, corrosion monitoring is very expensive. Time domain reflectometry is a method in which a high velocity pulse is sent down the length of a transmission line. Any imperfections along the line are reflected back, and the exact location of the imperfection can be determined. For our purposes, a sensor consisting of two parallel electrodes is placed at the end of a transmission line. The sensor is placed in differing chloride concentrations (0.1M, 0.5M, 1.0M NaCl) and reflected waveforms are analyzed and correlated using LabVIEW software. In our experiments, one electrode receives pulses from the time domain reflectometer (TDR) while the other electrode is held at ground. In order to study the initial redox chemistry of the electrodes, our focus has been on developing high-speed switching devices and software to accommodate the switches.