Western basin wharf front beam - installation and performance of a concrete cathodic protection system

摘要

Western Basin Wharves 3 & 4, owned by Newcastle Port Corporation (NPC), were built circa 1968 of conventional reinforced-concrete construction on precast and prestressed concrete piles. In the early 1990's, the front and rear beam soffits showed severe damage exhibited as cracking, rust staining, delamination and spalling. Conventional patch repair was carried out in 1994-1996 on the rear beams. The front beam (also known as the "crane beam") carries heavy loads and is structurally more significant. Following extensive investigations and consideration of available repair options, a decision was taken to install an impressed current cathodic protection (CP) system to the front beam soffit. A CP system was installed to Wharf 3 front beam in 1997- 1998. The anode system used was a mixed-metal-oxide (MMO) coated titanium ribbon mesh. The CP system was commissioned in November 1998. This paper describes the background to, installation of, and the monitoring and performance of the CP system. Performance of the CP system has been assessed by potential shift and potential decay criteria. The monitoring results are presented and assessed against each of the criterion. The monitoring results, for up to 21 months since commissioning, indicate that adequate protection is being provided to the front beam soffit reinforcement.