Development of Corrosion Rate Monitors for Reinforced Concrete: Fid-Bau Portal

Development of Corrosion Rate Monitors for Reinforced Concrete

B. Dougherty / B. G. Pound

The corrosion of steel reinforcing bar (rebar) in concrete represents a serious threat to the nation's infrastructure. A corrosion rate monitor was assembled from commercially available instruments. Software was developed to control the monitor's operation and to analyze the impedance measurements. A test probe containing a reference electrode and counter electrode was developed for use with the monitor. Tests of the monitor and probe on reinforced concrete slabs gave corrosion rates that were sensitive to the degree of wetness with respect to time and location. Field trials were performed on four bridge decks. Three of them had been exposed to deicing salt and the rebar showed severe corrosion, whereas the fourth bridge was in good condition. The test on the fourth bridge was performed when the concrete was wet, and it showed that the monitor can provide meaningful corrosion rates on large scale, reinforced concrete structures. Corrosion rates obtained for this bridge were low, which was consistent with the corresponding corrosion potentials and the observed condition of the rebar. The corrosion rate monitor was shown to provide consistent, reliable data for concrete structures that have been thoroughly wetted. However, use of the monitor faces a problem common to all electrochemically based monitors: if the concrete is dry, the monitors cannot provide useful data, because electrochemical corrosion activity is nonexistent at the time of measurement. Thus, these monitors are most suited to bridge decks where the concrete and any overlay can either undergo prolonged wetting prior to the tests or are porous/cracked enough that, if necessary, they can be wetted through to the rebar shortly before measurements are made.