Interstate 95 flows across the northern tip of Delaware and through Wilmington, then northward to Philadelphia, New York City and Boston. The highway is the busiest in the state, carrying 220,000 vehicles on an average day.
Delaware Department of Transportation (DelDOT) has identified four bridges in this area as particularly in need of repair. Although the bridge structures are in good shape, the bridge decks contain numerous patches and potholes. In addition, the approach slabs and deck joints need to be replaced.
Chance Malkin, area engineer of DelDOT, is leading the rehabilitation work. He told Construction Equipment Guide, "These repairs and maintenance improvements are necessary to extend the service life of the structures and maintain a safe, reliable roadway for the traveling public."
The busy 10 lanes of traffic are challenging to manage during construction. The project is expected to last two years and is approximately 40 percent complete. The cost of the project will be $42 million.
DelDOT photo
Workers are using an overlay of Ultra High Performance Concrete (UHPC), which is roughly four times stronger than traditional concrete. The concrete contains steel fibers, vastly increasing the strength of the concrete.
"This sturdy material will increase the life of the bridge deck as well as be more resistant to salt intrusion," said Malkin. "Managing traffic on this busy road is difficult, so this concrete should mean less repairs and disruptions in the future."
Workers are using a multiphase traffic control approach, including contraflow operations and several split traffic configurations. At the Churchman's Marsh Bridges (I-719 and I-720) engineers called for contraflow configuration. This enabled all five lanes of traffic to remain open by shifting one or two lanes onto the opposite side of the interstate, separated by a barrier.
DelDOT recognized that this complex traffic pattern can cause drivers to become confused. So, planners used important safety measures including advanced warning signage, special pavement markings and barrier protection between traffic and work areas.
So far, workers have performed four traffic shifts at the Churchman's Marsh section during extended weekend closures. The work team has been using hydrodemolition to remove some of the deteriorated concrete. This work naturally reveals some surprises, including "blow outs" or the need for full-depth deck replacements.
DelDOT photo
Eliminating Confusion
"At Bridges I-738, I-739 and on I-95 northbound, we needed to create additional construction workspace," said Malkin. "We had the lane numbers painted directly on the pavement and set up advanced signage so motorists would be guided about the split between I-95 and I-495."
In addition, the construction team members were transported into the area using mini-bus shuttles, which limited the number of construction vehicles entering the work zone. This helps prevent motorists from mistakenly following contractor vehicles into work zones.
One victory for the construction team was the proper placement of the UHPC on a superelevated bridge deck with a 7.5 percent slope along a horizontal curve. Contractor Greggo and Ferrara Construction (New Castle, Del.) performed a test pour, which proved successful. Workers then completed a Phase 1 test pour on the bridge deck.
DelDOT was forced to pause the work when a powerful winter storm hit the Eastern Seaboard, flattening trees across the state. Contractors sprang into action to clear the damage. Traffic was halted across much of the state, including in the Four Bridges project work zone.
DelDOT photo
Most of the equipment used for the work is standard highway equipment, including excavators, loaders, asphalt pavers, rollers and cranes. Specialized equipment used included UHPC placement and screening equipment and hydrodemolition machines used to preserve the bridges' steel skeleton while removing deteriorated concrete decks.
Work crews expect to lay down 15,000 tons of asphalt for the project. Additional asphalt might be used at the conclusion of the bridge work. In addition, work crews will use 130,000 lbs. of rebar and 2,000 cu. yds. of concrete.
Asphalt removed from the roadway will be recycled for future pavement production. Demolished concrete will be processed and used as base material in roadway construction.
As the project winds up next year, DelDOT hopes riders will experience a smoother ride for years to come.
"We are hoping that the UHPC overlay will extend the bridge deck's lifespan up to 50 years," said Malkin. "We want to make the numerous patches on the decks a thing of the past." CEG
(All photos courtesy of DelDOT.)
