Passive protection of reinforced concrete columns against stray currents and chloride attack

This study examines the effects of stray electric currents on corrosion in reinforced concrete and explores protective strategies. Field measurements of stray currents near urban rail systems were replicated in laboratory concrete column models, focusing on variables like concrete cover thickness, steel reinforcement, and proximity to the current source. Findings suggest that maintaining a minimum distance from stray current sources—50 m from subways and 300 m from ground-level trains—significantly mitigates corrosion risks, though achieving these distances is challenging in urban areas. Close to the current source (up to 7 m), passive measures, such as increasing cover thickness or using higher-strength concrete, proved ineffective, highlighting the need for active protection like cathodic systems. At intermediate distances (15–30 m), conventional chloride corrosion protection methods suffice. Stray currents also reduce the concrete's modulus of elasticity, affecting load-bearing capacity; however, thicker covers and higher-strength concrete can aid in recovery, enhancing resistance against corrosion over time.