Cathodic Protection and Repairs to Reinforced Concrete Bridge

thumb_hts_rochdalembc_queensparkbridge_cathodic_protection_fosrocQueens Park Road Bridge over the River Roch was built around 1932. The deck is in early reinforced concrete (Hennebique System) with a continuous slab between continuous longitudinal edge beams and a central stringer, all carried by massive cross beams cantilevering beyond the edge beams. The main span over the river consists of a single reinforced concrete open spandrel arch, approximately 39 metres clear between springings, with a tapering rectangular arch rib each side supporting vertical columns to the deck cross beams. The approach spans each side are supported by reinforced concrete braced trestles, the longitudinal edge beams are more substantial, spanning about 14 metres between the trestles and carrying the main cross beams.

Following testing work carried-out during previous years, HTS were contracted to undertake further concrete testing of the bridge in 2001/2002. All the data obtained was analysed using Colebrand’s “CorroScope” system in order to determine proposals for repair options. The final design called for “routine” concrete repairs and additionally, the installation of a Cathodic Protection (CP) system using sacrificial anodes as the most appropriate repair solution for both Queens Park Bridge and the Albert Royds Bridge (also installed by HTS). Acting as Main Contractor HTS successfully installed a range of “Galvashield” sacrificial anodes manufactured by Fosroc Ltd (who also designed the installation and monitoring system). Materials used included the linked anode system (“CC65” and “CC100”) along with individual “XP” anodes. This repair contract also included further concrete testing by HTS to provide data for the next phase of the repair works. Fosroc and RMBC client recognised that this project would provide valuable data of interest to others. Using the installed monitoring arrays to measure monthly changes in galvanic current a joint report has been produced for the Concrete Bridge Development Group (Clapham, Simpson and Ashley, CBDG Technical Paper No.11 , 2005).