Early 2008 we were contacted by Parchem to see if we would be interested in undertaking some Bridge refurbishment works for Melbourne Water.
This involved visiting each bridge with Melbourne Waters maintenance agent Thesis, Danlaid management visited each of the sites to appraise the scope of work required to bring each individual Bridge back to a suitable condition, this included the removal and repair of damaged and failing concrete to the bridge surfaces, the removal of previous repairs to the bridge decks and pylons.
At this stage plans were formulated as to how access was to be gained to perform certain parts of these works as several of the bridges were in tidal creeks with waist deep mud banks which would require some type of buoyant platform arrangement to gain access to the works area.
These works were also to utilise the new Parchem LJ Collar system to repair the pylons this was to be the first installation of this type in Victoria.
The works: the works entailed five bridges to be restored, Thesis undertook the first stages of these works that entailed the clearing of the brush and growth around the bridges, Thesis also arranged for the replacement of the hand rails on the bridges to compile with current requirements.
The first bridge was located beyond the tidal influences of Western Port Bay but did require the flow to be dammed and bypassed for the works to be undertaken. Works commenced with all surfaces being cleaned with high pressure water and grit blasting to remove all biological growth, grime and damaged concrete. The damaged areas were then repaired and coated to seal them from the elements.
The rest of the bridges were located within the tidal influence of Western Port Bay, each bridge required a different approach dependant on the amount of tidal influence that would need to be allowed for. This ranged from minor excavation and shoring to temporary dam walls being built with up to 50 tonnes of rock to stem the rising tides.
These bridges required the installation of the Parchem LJ Collars to all the pylons to affect the repairs and protect them from the encroachment of marine salts that corrode the steel reinforcement in all concrete structures in marine type environments.
The first step to these works required the removal of all the porous and damaged concrete in the pylons, the steel reinforcing was then inspected and repaired as required, and this entailed the creation of a continual circuit as the collars being installed rely on galvanic current to protect the structure. The pylons were then encased in the Parchem LJ collar units with the required connections to the steel reinforcing and anodes. These were then sealed and filled with a special grout mix that was pumped in to the collars.
The advantages to performing these works with comparison to the construction of new bridges included the reduced cost, little if any disruption to the use of the bridge and reduced environmental impact on the surrounding area and water way.
Other works carried out during these works entailed the construction of retaining walls and the sighting of beaching materials to stop the erosion of the banks of the water way.
All these works were conducted with minimal disruption to the bridge users.
The final stage of these works involved the removal of all waste materials and filling of all excavations to return the areas back to their natural state.