Effectiveness and structural implications of electrochemical chloride extraction from reinforced concrete beams

The overall aim of this paper is to examine the effectiveness and structural implications of electrochemical chloride extraction when applied to reinforced concrete beams containing chlorides as well as chlorides and reactive aggregates. Twelve beams, 100 × 165 × 2300 mm, were altogether cast and tested. The main variables in the beams were water/cement ratio, chloride content and reactive aggregates. Four of the beams contained a reactive aggregate in the concrete mix. All the beams were kept dry, after initial curing, to see if the electrochemical process triggered alkali silica reactivity. The chloride extraction process used an anode system of oxide coated platinised titanium mesh and saturated calcium hydroxide solution as electrolyte. The applied cathodic current density was about 1 A/m2. Chloride analysis of the concrete in the beams was carried out before, during and after the electrochemical treatment, and the pH of the electrolyte and any alkali silica reactivity were regularly monitored. The beams were subsequently tested to failure at an age of about 400 days. It is shown that electrochemical treatment is an effective and efficient process to remove chlorides from the cover concrete and from the zone containing steel reinforcement without any adverse effect on structural strength, bond or shear. There was clear evidence that unlike cast-in chlorides, the chloride extraction process will be far more efficient in real structures where the majority of chlorides that would have penetrated into the concrete will be from the outside aggressive environment and which will remain mostly in the concrete cover zone. However, further research is needed to establish the long term effects of alkali silica reactivity initiated by the CE process, and the structural implications of carrying out CE in the field if the dead and live loads carried by the beams are not relieved.