Reference cells are needed to measure the potential of embedded steel in cathodically protected, reinforced concrete members to ensure that the level of protection is neither too high nor too low. Embedded cells are more convenient than surface cells where access to the protected surface of the structure is difficult, and they are essential when potential-controlled rectifiers or remote monitoring systems are being used. This paper reports the results of a series of laboratory, outdoor exposure plot, and field tests to evaluate the suitability of candidate embedded reference cells for use in reinforced concrete. Zinc-zinc sulfate, silver-silver chloride, molybdenum-molybdenum oxide, lead-lead oxide cells, and graphite electrodes were evaluated. The graphite electrodes were found to be the most stable with time and the least influenced by changes in temperature or the chloride content of the concrete. They were also inexpensive. The only other cell considered suitable for embedment in concrete was a silver-silver chloride cell, although this type of cell was more affected by temperature and chloride content than was graphite. Large performance variations occurred in some cells of the same type from different sources.
Samenvatting