Experimental Study on Repair Methods of Corroded Bridge Cables

Abstract

The cables and hangers of old suspension bridges and the stays of cable-stayed bridges often suffer from steel corrosion. It is important to repair them by proper methods to prevent the further progression of corrosion. In this paper six repair methods were proposed and applied to cable specimens. Then, the specimens were exposed to severe corrosion environments and the effectiveness of the proposed repair methods was compared. Two different types of test cables were used in this study: parallel wire strands and spiral strands. The first test group used parallel wire strand cables consisting of 19 nongalvanized steel wires. This test was aimed at the main cables of the suspension bridges. Six repair methods were applied to these cable specimens: coating with zinc-rich paint, coating with epoxy resin paint, coating with zinc powder paste, filling with epoxy resin, filling with oil, and a dehumidification method. Then, the specimens were accelerated to corrode in a laboratory for 15 months. By investigating the mass loss owing to corrosion and appearance during this period, the effectiveness of the six repair methods was compared. For the surface wires, the dehumidification method was the most effective followed by the epoxy resin paint and filling, the zinc powder paste, and the zinc and epoxy resin paint on the surface. The oil filling was not very effective compared with other repair methods. The corrosion of the inside wires was much less than for the surface wires. The second group test used spiral strand cables consisting of seven galvanized steel wires. This test was aimed at the hangers of suspension bridges and the stays of cable-stayed bridges. The same repair methods and corrosion acceleration methods were used. By investigating the mass loss owing to corrosion and the appearance of both inside and surface wires during the 16-month period, most of the proposed repair methods were very effective compared with those of unrepaired strands. This study proves that even if cables are corroded proper repair work is effective in preventing further corrosion.