Severe deterioration of a reinforced concrete cooling tower, which comprised pre-cast columns, beams, wall panels, and slab panels was noticed during the last few years. A diagnostic survey was conducted to identify the cause and extent of deterioration. The concrete deterioration was very advanced in some areas, particularly on the external side of the end walls and posing a safety hazard to plant personal. Internally, the level of defects was very low with only minor patches of delamination and cracks. Both chloride and sulfate ions were present in the concrete cover at rebar depth well in excess of their threshold levels. About 12% of the half-cell potential results indicated high (90%) corrosion risk and 53% of the results exhibited medium (50%) corrosion risk in all tested areas of the structure. The investigations concluded that deterioration of concrete has occurred mainly due to chloride- induced corrosion of the steel reinforcement. Patch repair and cathodic protection (CP) repair method was recommended to arrest the ongoing corrosion of the steel reinforcement. The CP system design, installation, and initial commissioning results are also described and discussed.
Key Words: concrete deterioration, delamination, chloride, sulfate, half-cell potential measurements, probability of corrosion, patch repairs, cathodic protection, titanium mesh anode.