Managing bridge deck joints is an ongoing challenge, and PennDOT continues to explore ways to use Bridge Deck Link Slabs as an innovative way to address this bridge maintenance issue.
Working through the State Transportation Innovation Council, PennDOT has developed a process to use a combination of Ultra-High Performance Concrete (UHPC) and reinforcing steel to connect bridge decks with a watertight connection, said Mark Nicholson, PennDOT District 1 bridge engineer.
He noted that with the normal bridge expansion and contraction, bridge joints fail over time and allow salt and brine from de-icing efforts to contaminate the bridge compartments.
In 2020, District 1 conducted a pilot with Bridge Deck Link Slabs on SR1009 bridge over Lake Wilhelm in Mercer County. The 181-foot long bridge has three spans and was built in 1969.
With an existing asphalt overlay, the bridge deck was scarified, and a high-pressure water process was used to remove the old deck surface and unsound concrete. This provided an excellent bonding surface for the new applications, which included a latex modified concrete overlay.
Existing joints over the first and second piers were removed, backer rod material was installed below the joint; and grout was installed to provide a smooth surface below the joint material. Gasket material was placed over the grouted surface to act as a bond breaker, preventing the UHPC from bonding to the underlying deck or beams. Then, a single layer of reinforcing steel was installed.
Chimneys were installed over the form work so the UHPC, which was mixed onsite with water and fiber reinforcement, could be poured to create a pressure head. That aided in filling the forms and eliminating voids in the concrete.
Forms were removed the following morning and then the new link was diamond grinded to match the grades with those on the bridge deck.
In the 28-day interim period until the asphalt overlay was applied, the link slab showed no signs of cracking or debonding from the adjacent deck.
The district plans another link slab bridge, on SR 2102 over Interstate 79, but funding issues have delayed that project until next year.
Nicholson did investigate using the innovation on the SR427 bridge in Venango County with the County Bridge Crew. "However, we did the design calculations and determined it was not a good candidate for our bridge crew to perform," he said. He added that he is now reviewing whether the approach can be used on the SR2104 bridge over Interstate 79.
The next steps for this innovation include developing standard design details and procedures. To aid in this process, $40,000 in Federal Highway Administration (FHWA) STIC Incentive Program funding was recently awarded to support the development of the design procedures and design tools for using Bridge Deck Link Slabs in Pennsylvania. Once that is refined and approved, that information will be included in PennDOT's standard drawings, specifications, and design manuals.