OSAKA -- West Japan Railway Co. is considering a new method by which neutralized concrete along its bridges and tunnels can be repaired to undo the effects of erosion, company sources said Thursday.

JR West has experienced 47 incidents in which concrete slabs have fallen off along its Sanyo Shinkansen Line since fiscal 1996, and there is a pressing need to find an effective way to repair these structures.

The new method involves using a direct electrical current to enable an alkaline solution to seep into the concrete and restore its alkalinity. The main factor behind concrete erosion is believed to be neutralization, caused when alkalinity is reduced due to exposure to the air.

JR West has been experimenting with the direct current method, developed in Norway, since 1993 to fix elevated bridges along its maintenance tracks, and its effectiveness has been confirmed through inspections, the sources said.

According to JR West, the neutralization of concrete along elevated tracks also makes it easier for the steel frame inside to rust and expand, leading to cracks in the concrete's surface. Chlorine is also believed to be a reason the steel erodes quickly.

Under the direct current method, the surface of the concrete is covered with fiber, and an alkaline solution is sprayed on. Lead wires with negative polarity are then connected to the steel inside, while those with positive polarity are attached to the concrete's surface.

The electric current causes negative chlorine ions to move toward the surface, while the alkaline solution penetrates toward the steel, thus correcting the neutralization.

Although the process is cumbersome and costly, JR West is considering using it in points most in need of repairs, the sources said.