Interstate 895 Patapsco River Flats Bridge

The I-895 bridge over the Patapsco River Flats near the Baltimore Harbor Tunnel required replacement of its aging superstructure while preserving the existing substructure located in environmentally sensitive marshland. Because the original foundations had limited load capacity, engineers needed a lightweight structural solution capable of maintaining full highway load requirements.

To meet these constraints, the project team designed a superstructure system using galvanized grid deck panels with a partially filled concrete grid and an ultra-lightweight structural concrete deck produced with Stalite Lightweight Aggregate. The deck system utilized 4,500 psi lightweight concrete with a density of approximately 100 pounds per cubic foot, allowing the finished deck to remain under the specified weight limit of 50 pounds per square foot while still providing a durable 2-inch integral concrete overfill.

Construction was performed in stages to maintain traffic on this critical Baltimore transportation corridor. Crews replaced the superstructure using a leap-frog approach, first diverting traffic onto one side of the bridge while replacing the opposite spans. The design’s repeating two-span continuous units, approximately 110 feet long, allowed McLean Contracting to replace one section at a time while maintaining steady progress.

Approximately 177,000 square feet of prefabricated galvanized grid deck panels were installed as part of the accelerated construction approach. All work was conducted from the bridge deck itself, minimizing environmental disturbance to the marshland below and allowing the contractor to maintain traffic flow during construction.

The lightweight structural concrete produced with Stalite Lightweight Aggregate reduced dead load on the existing bridge foundations while enabling a durable deck system that could be installed quickly with minimal disruption to traffic.