A study on the efficiency of electrochemical realkalisation of carbonated concrete

In this paper, the efficiency of electrochemical realkalisation of a carbonated concrete is investigated. The realkalisation width, pH value nearby the rebar, the open circuit potential and the instantaneous corrosion rate are used to evaluate the performance of electrochemical realkalisation. In addition, several mechanical properties including compressive strength, elastic modulus and bond strength are determined to check whether the electrochemical realkalisation process degrades them. Water absorption test and four-probe electrical resistivity are measured to investigate the densification of pore structure. It is found that all properties show apparent trends with respect to the influence parameter, defined by the product of the realkalisation current density and the realkalisation period. As the influence parameter increases, pH value increases and the realkalisation width expands. Consequently, the open circuit potential indicates that the realkalisation successfully rebuilds the passive film on rebar and the instantaneous corrosion rate decreases dramatically. Compressive strength, elastic modulus and bond strength for realkalised specimens all decrease compared to the carbonated specimens due to the degradation effect from the cathodic current. However, they still exceed those of the control specimens due to the carbonation product. The resistivity and water absorption demonstrates that the realkalisation further condenses pore structure.