Washington USA based Triton Marine is working as subcontractor to Nova Group Construction to carry out renovations to Piers F12 and F13 on Ford Island at Naval Station Pearl Harbour. Areas of concrete in poor condition are being replaced to provide a better surface and ensure the piers’ longevity. The work involves the removal of spalled concrete and any corroded rebar followed by their replacement with new materials.

Triton Marine had previously always broken out concrete using labour intensive conventional methods with hammers but is coming to the view that in future hydrodemoloition will be the only way to remove concrete as other methods cause more damage.

Buying the Aqua Cutter for the Pearl harbour project has enabled staff to build familiarity with its operation. The work involves the removal of some 3,000 sq/ft of concrete from the decks of the two piers, in individual areas of varying shapes. The concrete as originally poured in the 1940s, when specifications and quality control were less stringent than today, and is thought to contain porous crushed volcanic stone. Over time it had broken up, allowing the ingress of water. A vacuum truck works with the Aqua Cutter, matching its pace with rapid removal of debris.

The HD-6000’s forward movement and the oscillation of its head can be easily adjusted to suit the area to be removed. In the weakest areas of the Pearl Harbour piers, only one or two passes of the high pressure jet head are needed to remove the concrete to he required depth. Triton Marine staff quickly built expertise in adjusting parameters such as cutting width, speed and angle of the jet.

The versatility of the HD-6000 avoids the unnecessary removal of sound concrete. The passage of the jet is determined by adjusting the travelling range of the lance roller and the distance moved by the robot’s tractor unit. This ensures that the hydrodemolition is carried out only on the damaged concrete, without harm tio surrounding areas.

The Aquajet robot can be adjusted quickly to take account of differing shapes and sizes of areas to be removed. Repairs were often narrower than the width of the machine head but this was catered for by using the HD-6000’s proximity switch adjustment which facilitates easy adaptation to suit varying widths. Magnetic stops determine how far the head goes before turning. The distance of tractor travel is also easily controlled through visual markers set outside the removal area.