At its groundbreaking, The Conti Group's Route 18 Rehabilitation project was the largest project ever undertaken by the New Jersey Department of Transportation (NJDOT). This extremely complex $215 million two-mile corridor safety and traffic improvement and revitalization project was located in the urbanized area of New Brunswick, NJ, serving New Brunswick, Rutgers University, hospitals, and major corporations. It runs along the city's Raritan River waterfront, accommodates 85,000 motorists daily and is a key component to the on-going civic redevelopment of the city's downtown core. Prior to rehabilitation, Route 18 was plagued with some of the worst traffic congestion in the state, threatening the economic vitality in the region.
The project was an extremely complex undertaking requiring the demolition, construction, or rehabilitation of six bridges, development of local and express lanes and 25 retaining wall structures, while keeping traffic flowing. At it's peak, the project construction workforce topped 200, which included Conti staff, crews and subcontractors. Construction commenced in Spring 2005, culminating in March 2010.
For this architecturally prominent project, the designer, Gannett Fleming, developed a Brunswick Shale cut stone look for large surface areas such as walls and bridge piers. Exterior parapets of bridges mimicked the look of a balustrade pattern common to many older bridges and walls in the New Brunswick area. Finally, they incorporated arch shapes similar to the historic Pennsylvania Railroad arch bridge that crosses Route 18 just north of the project. As a result, three major decorative concrete elements were incorporated into the project: Decorative cast-in-place, artificial rock surface treatments and pre-cast concrete arches supporting the George Street Bridge.
Cast-in-place Decorative Concrete: Re-usable form liners were installed on the concrete formwork to obtain an aesthetic finish of traditional concrete. Later application of the colored stain included handwork to detail the faux joint lines between the stones, as well as different colored splatters to achieve a natural finish. Most challenging was coordinating the desired pattern when attaching the liner to the forms. Assembling the liners was a giant jigsaw puzzle, ensuring all joint lines were properly aligned and the pattern of the "stones" in the liner was correct. In total, over 138,000 SF of cast-in-place concrete was stained, including 72,740 SF of concrete poured with a form liner treatment.
Artificial Rock Surface Treatments: Boulderscape® was utilized to maintain visual continuity with the natural rock outcroppings along the corridor, complimenting the antique architectural elements of Rutgers University's Douglass campus that overlooks the site. Conti and our subcontractor Boulderscape, Inc. used a specially formulated mix design of 4,500 PSI shotcrete that had special plasticizer, rock and sand ratios which were proportioned to be pumpable, durable, and pliable enough to create detailed carving and retained texture. Once additional concrete was placed over the structural shotcrete layer, the artisans began sculpting, carving and texturing the pliable concrete, following the mockup story board. During the staining process, the surface is highlighted with several natural colors to give it depth and variation, and incorporated fissures and fractures to resemble natural stone. Much of the Boulderscape was installed during the winter months, requiring special tents and heaters to be erected to raise the temperature of the steel and allow continued shotcrete progress to meet the schedule. The NJ DOT client was so pleased with the look of the final product on the first Boulderscape wall that it was decided to apply it to 3 additional walls.
Arches: The 593 ft George Street precast concrete barrel arch bridge features eight pre-cast arch barrels, each with a span of 66 feet and a rise of 20 feet, furnished by the Reinforced Earth Company. A total of 16 precast pieces were needed per barrel, and 128 pieces for the total bridge. The arch pieces were constructed using 5,500-pounds-per-square-inch concrete and were cast with crown ends to allow them to mate properly. Conti devised an innovative, first-ofits- kind installation technique that used temporary hydraulic structures to brace the first three arch segments until the forces were balanced out enough that they could be removed. These were the first similar structures in the world to be constructed with lightweight concrete fill.