The Woodrow Wilson Memorial Bridge carrying I-95 over the Potomac River near Washington, DC opened six lanes for northbound Outer Loop traffic on June 10, 2006. In May 2008, six lanes of southbound Inner Loop traffic were opened, almost eight years after this monumental construction project began. However, this was not the first time the Woodrow Wilson Memorial Bridge faced a major transformation.
As originally built between 1959 and 1962 at a cost of $12.2 million, the 
Woodrow Wilson Memorial Bridge had six traffic lanes and was 5,900 feet (1,798 m) long. The structure was built as a bascule bridge to allow large, ocean-going vessels access to the port facilities of Washington, DC.[1] The bridge suffered the ravages of weather, salt deterioration and heavy use causing serious maintenance problems. It underwent continuous patchwork maintenance beginning in the 1970s.[2] It was completely re-decked from 1982 to 1983.[3] By 1977, the original normalweight concrete decking was beginning to crumble and needed to be replaced and widened without adding weight to the substructure.
In one of Carolina Stalite Company’s earliest high-profile structural concrete projects, lightweight aggregate was used to fulfill rigid specifications of strength, weight and durability. Greiner Engineering Sciences, Inc. designed the new re-decking system. The system consisted of 1,026 post-tensioned panels and parapet walls of precast lightweight aggregate concrete produced by Shockey Brothers, of Winchester, Virginia. Believed to be one of the first applications of lightweight concrete in full-depth, precast concrete deck panels, the precast concrete mixture design for the Woodrow Wilson Bridge called for a dry unit weight of 115 lb/ft3 (1840 kg/m3), a 28-day compressive strength of 5,000 psi (34.5MPa) and a maximum water-cement ratio of 0.44[4]. The system allowed the bridge to be widened from 89’-0” to 93’-2 ½” while maintaining traffic of 110,000 vehicles per day. Cianbro
Corporation of Pittsfield, Maine was the low bidder for the bridge deck replacement/widening contract at $23.726 million. This was approximately 72% of the 1982 estimate for the project. The first panels were set into place in December 1982. Cianbro could work only at night and had to maintain traffic 24 hours a day. Panel placement was completed in August 1983, well ahead of the full bonus date in January 1984. Each panel was 46’-7 ¼” wide, 10 to 12 feet long, and 8” thick with a 5” haunch at the exterior girder. The panels were post-tensioned transversely at Shockey’s plant prior to transportation to the job-site. To eliminate transverse joints, the deck system was post-tensioned longitudinally in segments from 140’ to 285’ long and separated by steel expansion plates.
Designed to handle 75,000 vehicles a day, the bridge became extremely overcrowded. At the time, the Woodrow Wilson Memorial Bridge Replacement Project started in 2000, the lightweight concrete continued to perform, even though it was handling 200,000 vehicles a day, more than 2.6 times the original design capacity.[5] The benefits of structural lightweight concrete for bridge decks include not only reduced dead load, but also greater freeze-thaw resistance and internal curing that helps prevent early age shrinkage (reducing early age cracking), and increases hydration of cementitious materials throughout the concrete resulting in longer service life.
1) “New Span Bids Open On June 30”, The Washington Post. June 22, 1958. p. B3.
2) Reid, Alie; Fehr, Stephen C. (April 26, 1998). “The Rush Hour of Decision On Replacing Wilson Bridge”, The Washington Post. p. A1, A21-A22.
3) Feaver, Douglas B. (July 6, 1980). “Major Rebuilding Set for Wilson, Cabin John Spans”, The Washington Post. p. A1; “Wilson Bridge Lanes to Close For Re-decking”. The Washington Post. November 14, 1982. p. B1; “Wilson Bridge Repairs to Be Finished Tonight”. The Washington Post. September 21, 1983. p. C4.
4) “Material Investigation of the Full-Depth, Precast Concrete Deck Panels of the Old Woodrow Wilson Bridge”, http://www.virginiadot.org/vtrc/main/online_reports/pdf/08-r2.pdf
5) Fehr, Stephen C. (December 20, 1991). “Fixed Schedule Proposed for Wilson Bridge Drawspan”. The Washington Post. p. C3.