The $4.6 million contract to rehabilitate a bridge on Interstate 190 near Grand Island, New York allowed 18 months for construction. Based on a visual inspection of the bridge, the contract called for the removal of 14,000 square feet of bridge deck. Deteriorated surface concrete was to be removed to a depth of at least 1 inch below the top reinforcing steel. After Sevenson Construction Corporation of Niagara Falls was awarded the contract, though, they took half cell potential tests of the bridge and discovered that 75,000 square feet of the concrete bridge deck was unsound and needed to be removed. Despite this 500 percent overrun, Sevenson completed the entire project in only 4 months--14 months sooner than the contract required. This almost miraculous speed was due largely to the high-pressure waterblasting machine that was used to remove the deteriorated concrete.
The waterblasting machine consists of three parts: a power unit, remote control, and a robot. The robot does the actual cutting. A special water jet nozzle runs back and forth on a horizontal bar at the front of the machine. The high-pressure water jet cuts grooves in the pavement surface and at the same time breaks away the concrete between these grooves.