The Port of Auckland is a large container and international trade port on the Waitemata Harbour. Its 55 hectares of wharves and storage areas are mostly situated on reclaimed land.
History
Bledisloe Wharf was constructed in the late 1970’s using precast and pre-stressed I-beams, and panels between the beams as the base for the deck slab overlay. Piles and headstocks and the quayside beams were poured in situ.
Routine inspections in the late 1990’s discovered a severe chloride contamination, with the profile of the penetration extending inwards beyond the lower reinforcing strands and stirrups. There were many sites where corrosion was evident or rust stains were seeping out of the concrete.
Contamination Factors
Compounding the problem were two factors. A ship had regularly discharged bilge water with contaminants that effectively sealed the lower surfaces of the I-beams with a deposit in appearance similar to a varnish.
Secondly, tidal washing and splashing combined with salt-contaminated rainwater which was leaking through the deck and running down the sides of the beams caused moisture and chlorides to be encapsulated within the concrete by the impermeable coating of “varnish” on the lower flange of the beam.
Treatments
A cathodic protection system was installed on four of the most affected beams.
It soon became obvious that not only the beams but the quayside, piles and headstocks and rear wall as well as the balance of eighty beams and all the precast panels in the soffit were at risk. Although cathodic protection could protect the beams it was impractical and not a viable option when the cost was considered.
In 1999, the AQURON 7000 System was selected as the answer.
The bottom of the beams and piles etc were high-pressure water-blasted and with sand for the more difficult areas to clean. Then the AQURON solutions were applied to every exposed surface of the structure using high-pressure spray equipment and a barge below deck. The photos show the specialized boom equipment applying the AQURON solutions to the wharf deck.
Success
Tests conducted in 2008 showed the corrosion to have been arrested, and remaining dormant – proving the success of AQURON 7000 as a durability treatment for marine structures.
Free project brief download here.
