In electrified railways the the steel catenary structures are supported by concrete footings to which they are secured with anchor bolts. For safety reasons, the catenary structures are grounded to the return rail. At times when trains are in the immediate vicinity of the catenary structure, a potential of as much as 25 volts may exist between the structure and the ground. If direct current is used for power, a current flow from the structure through the anchor bolts and concrete into the ground results from this potential. The anchor bolts become corroded from this current flow and the resulting expansion due to the increased volume of the rust cracks the concrete, which permits water to contact the steel, further accelerating the deterioration.
The research staff of Association of American Railroads was asked to investigate this condition a few years ago. The first work was to excavate around several footings...
