Pearl Harbor Concrete Repairs

Edited by Loren Faulkner | September 28, 2010

A hydrodemolition robot from Aquajet Systems is helping Triton Marine Construction to achieve high production rates in the removal of spalled concrete from two piers at Pearl Harbor, in Oahu, Hawaii. The Aqua Cutter HD-6000's high-pressure water jet system takes just a minute to remove a cubic foot of the weak 1940s concrete — equivalent to a cubic meter in about half an hour.

"Its performance is incredible," says Triton Marine Construction superintendent Brett Gordon. This is Triton Marine's first project using its newly purchased HD-6000 and other projects are already lined up. "We feel that hydrodemolition will soon be specified on every job and we decided to purchase the equipment now so that we are set up for that movement into the future."

Triton Marine, based in Bremerton, Washington, is working as subcontractor to Nova Group Construction to carry out renovations to Piers F12 and F13 on Ford Island at Naval Station Pearl Harbor. Areas of concrete were in poor condition and so are being replaced to provide a better surface and ensure the piers' longevity. The work involves the removal of the spalled concrete and any corroded rebar followed by their replacement with new materials. It has been taking just one minute to remove an area of 3 square feet to a depth of 4 inches.

"The concrete was originally poured in the 1940s, when specifications and quality control were a lot less stringent than today," says Gordon. Over time, areas of the old reinforced concrete had become broken up, allowing the ingress of water.

The aggregate is a black, porous crushed stone, which is believed to be volcanic. It gave a very soft concrete which the HD-6000 has been able to remove very quickly, says Eric Zimmerman, general manager of Putzmeister's Water Technology division. "This is an exceptionally high production rate — about three to four times higher than normal," he adds.

The Aqua Cutter HD-6000 robot was supplied to Triton Marine by Putzmeister America's Water Technology Division, which also provided a two-day course in its operation and servicing, followed by further training at the job site on Ford Island.

Triton Marine had previously always broken out concrete using labor-intensive conventional methods with hammers. The decision to buy the HD-6000 was taken with a view to upcoming contracts, including a major highway project where time pressures will be intense. "We looked at the closures that will be allowed there and the manpower that would be needed for conventional methods," says Gordon. "We feel that hydrodemolition will soon be seen as the only way to remove concrete ..."

(Editor's Note: Information provided by Putzmeister Water Tech.)