Determination of the polarization resistance of steel in carbonated fly-ash concrete- effect of measurement technique
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The polarization resistance (Rp) of a metal gives an indication of the corrosion condition at a given time. The Rp of embedded reinforcement in concrete is usually determined using the linear polarization resistance or the galvanostatic pulse technique. The relatively high electrical resistivity of concrete is a challenging factor when determining Rp. The electrical resistance becomes higher when adding supplementary cementitious materials to Portland cement or upon carbonation. Reinforced concrete prisms with 16-mm carbon steel reinforcement and concrete cover 20 mm were prepared using Portland-fly ash cement. The prisms were sealed-cured for two weeks and subsequently completely carbonated. The Rp of the reinforcement was determined using the linear polarization resistance and galvanostatic pulse techniques, and electrochemical impedance spectroscopy. The possible influence of using an embedded or an external reference electrode was investigated. Overall, comparable Rp values were determined with the three investigated techniques using either the external or the embedded reference electrode.