IMPROVEMENT IN THE GRAPHITE REFERENCE CELL FOR REINFORCED CONCRETE

FOR CATHODIC PROTECTION SYSTEMS TO BE SUCCESSFUL IN MITIGATING CORROSION WITHOUT CAUSING HYDROGEN EMBRITTLEMENT OF PRESTRESSING STEEL, THE AMOUNT OF POLARIZATION OF THE EMBEDDED STEEL MUST BE VERY ACCURATELY CONTROLLED. PRESENTLY AVAILABLE EMBEDDED REFERENCE ELECTRODES DO NOT HAVE THE LONG TERM STABILITY OR RELIABILITY RE@UIRED TO MONITOR AND CONTROL THE AMOUNT OF POLARIZATION WITH THE ACCURACY REQUIRED TO AVOID HYDROGEN EMBRITTLEMENT. PREVIOUS STUDIES HAVE SHOWN THAT GRAPHITE ELECTRODES EXHIBITBETTER STABILITY IN SHORT-TERM TESTS AND ARE THE LEAST INFLUENCED BY CHANGES IN TEMPERATURE OR THE CHLORIDE CONTENTOF THE CONCRETE. HOWEVER, THEY ARE NOT PERFECTLY REVERSIBLE, THEIR LONG-TERM STABILITY IS UNKNOWN AND VARIABILITY BETWEEN DIFFERENT GRAPHITE ELECTRODES HAS BEEN NOTED. THE PRIMARY FOCUS OF THIS PROGRAM WILL BE ON EVALUATING AND IMPROVING THE GRAPHITE ELECTRODE. THE PRIMARY TECHNICAL QUESTION TO BE ANSWERED AS A RESULT OF THIS PROGRAM IS WHETHER OR NOT THE REVERSIBILITY, REPRODUCIBILITY AND STABILITY OF GRAPHITE AS A REFERENCE ELECTRODE IN CONCRETE CAN BE SIGNIFICANTLY IMPROVED VIA SELECTED MODIFICATIONS ANDTREATMENT METHODS. THE SECOND FOCUS OF THE PROGRAM IS TO COMPARE THE PERFORMANCE OF STANDARD AND MODIFIED GRAPHITE REFERENCE ELECTRODES TO COMMERCIALLY AVAILABLE AND OTHER RECENTLY DEVELOPED EMBEDDABLE REFERENCE CELLS IN CONCRETE.