Electrochemical Realkalisation of Reinforced Concrete Using a Conductive Mortar Anode

Abstract

Carbonation causes concrete acidification that brings in the loss of the steel rebar's passive layer, which in turn will allow initiation of an active corrosion process. A nondestructive technique to revert this condition is the electrochemical realkalisation (ER) that consists in applying a direct current between the steel bars and an external auxiliary electrode placed on concrete surface with the aim of restoring the alkalinity loss. In the present work is studied the use of a conductive mortar as anode in the electrochemical realkalisation of concrete. Carbonated reinforced concrete specimens with a water/cement ratio of 0.65 were evaluated. ER was applied by 5 days period with a current density of 2 A/m2 and using as anode a layer of modified mortar (add 25% graphite powder by cement weight) saturated with a 1M Na2CO3 solution. The pH in the concrete was determined by the phenolphthalein test and potentiometric titration. After the ER treatment the pH value of the carbonated concrete samples had increased from 8 to 11.95.