The twin spans of the Delaware Memorial Bridge were showing their age by 2018, with more than 1 billion cars and trucks having rolled across their decks over the decades. Built in 1952, the deck of the older of the two spans was judged to be approaching the end of its service life.

Working with WSP USA, the Delaware River and Bay Authority opted for a new and cutting-edge approach to replacing the deck with the use of ultra-high performance concrete, or UHPC.

Photo courtesy WSP and UHPC Solutions North America

As the first use of UHPC on a suspension bridge in the world, the authority decided to first do a pilot project to test the new approach. This involved removing the top 3.75 in. of the deck on a 25,000-sq-ft section and replacing it with UHPC; the work incorporated “overlays on the main suspension bridge as well as on the deck truss and steel girder approach structures,” according to the project team.

One of the more complex and challenging aspects of the structural work involved taking out the longitudinal joint of the deck to create continuity. This called for a full-depth removal. The team, after a brainstorming session, chose hydro demolition to remove the reinforced concrete deck strip, with manual break methods needed to take out the centerline longitudinal joint area.

WSP was also able to draw upon in-house UHPC experts to help with the research needed in crafting the pilot project.

Photo courtesy WSP and UHPC Solutions North America

Overall, the initiative required a high level of collaboration and flexibility by WSP and its construction team to deal with ongoing traffic, a tight construction timetable and the complexities of using UHPC as an overlay material.

WSP and its construction, engineering and design team were able to complete the 29-month project at budget and on schedule. The project team says finishing the project on time was crucial given the need to get traffic on the bridge flowing freely again as quickly as possible.

Photo by John Baer - Building Images Photography

The UHPC overlay was completed in the fall of 2020 and set new milestones in the U.S., representing the “largest area of an UHPC overlay on a project to date and as the largest continuous pour of UHPC overlay.”

The work, which took place at the height of COVID-19 pandemic, also required close coordination to ensure all health requirements were put into place and followed.

The contractor, J.D. Eckman, conducted daily and weekly safety huddles with the aim of instilling “constant awareness” when it came to traffic control, personal protective equipment, fall protection, concrete demolition and hot works burning procedures, among other potential hazards.

The vigilance on COVID protections and on other hazards helped ensure the project’s completion with minimal safety issues.