Availability of Epoxy-Coated Rebar Keeps Project on schedule

By: John Prentice

The Marquette Interchange is an $810 million construction project in Milwaukee, Wis., with a 50-year history. Initial plans were presented in December 1952; the exchange was opened in December 1968. After 30 years of service, the Wisconsin DOT determined that it was time for reconstruction of the interchange, with the goal of building it better at a lower cost. It will also be reconfigured. Consisting of six phases, construction of the first phase began in April 2004. Completion of the entire project is scheduled for November 2008.

Reconstruction was necessary for a number of reasons, including deteriorating bridges, traffic congestion, traffic safety and the economic well being of the state. The project connects most of the area’s freeways, which link about one-third of the state’s freeway traffic to the rest of the country. These highways, I-94, I-794 and I-43, are the cornerstones of the southeastern Wisconsin freeway system. The exchange serves approximately 300,000 vehicles a day.

The project has many unique constraints. Many of the highways are not at grade, but are elevated or below grade. The project will make extensive use of bridges, retaining walls and short tunnels. In total, 152 bridges will be reconstructed close to the existing maximum height of 120 ft. Other project constraints include the reconfiguration within the existing footprint, reconstruction under traffic and an aggressive project schedule that requires construction during the winter season.

The original cost estimate was $1.4 billion, but by fine tuning the design, the total cost was reduced by $600 million. The project will require about 11,500 tons of steel reinforcing bars. In the first phase, 750 tons of reinforcing bars were used (150 epoxy-coated and 600 black bar). In the second phase, 3,100 tons were used (350 epoxy-coated, 2,750 black bar). Chosen for their ability to reduce corrosion, epoxy-coated reinforcing bars will be used in concrete piers, girders and decks. Originally these portions of the structure were to be built with stainless-steel clad reinforcing bars. However, due to the lack of availability and the tight construction schedule, epoxy-coated steel reinforcing bars became the material of choice.

Owned by the Wisconsin Department of Transportation, the project was headed up by Milwaukee Transportation Partners and HNTB. The contractor on these phases was Walsh Construction Chicago. Toltec Steel Services, Kankakee, Ill., supplied all epoxy-coated and black reinforcing bars. Toltec also did the coating of the epoxy-coated steel reinforcing bars.