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| Confronting long reach, the contractor devised an installation method for the precast wing wall (below): the crane would hold one side, the excavator the other. Once the structures were set, early strength Rapid Set grout was flowed into keyways. The accelerated construction method represented a premium of less than 10 percent compared to a conventional approach, engineers estimate, and shrank a minimum seven-day construction window to 60-65 hours. |
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To limit downtime and inconvenience to Middletown residents, the Connecticut Department of Transportation aimed for a quick method to replace the short span Route 17 bridge over Long Hill Brook. Anchor Engineering Services, a civil and environmental consulting firm located in Glastonbury, Conn., decided that precast concrete would be the quickest solution. Its task was to design a replacement structure bearing on a foundation set in the stream bed’s variable rock base.
The accelerated bridge project was scheduled around a Friday evening start and Monday morning reopening. J. Iapaluccio, Inc., a full service civil/site contractor from Brookfield, Conn., kicked off work with excavation, brook diversion and demolition of the existing span. By midday on Saturday, crews finished removing all of the material, and began working on the project’s most innovative aspect: Placement of large super sacks of sand for use as the sub-foundation’s formwork/cofferdam. In each of two phases, crews set the 1-ton sacks around foundation perimeters and marked the correct elevation directly onto the canvas. The use of the sand sacks as stay-in-place forms curtailed potential problems attending removal of conventional plywood or steel alternatives.
To pace the cast-in-place concrete sub-foundation, Anchor Engineering selected a mix with Rapid Set Cement capable of developing 3,000-psi compressive strength in two hours. The concrete was produced in volumetric mixers, furnished by InTerra Innovations, and placed in the forms using conveyors stretching 100 to 150 feet. After approximately three hours, J. Iapaluccio placed precast foundation members on the newly cast sub-foundation, prepping a Rapid Cement concrete closure pour with small sand bags.
After approximately three hours of closure concrete curing, precast wing walls were erected, followed by nine sections of United Concrete Products’ 25- x 7-ft. precast concrete three-sided bridge were installed, followed by the installation of the precast eastern wing walls. United Concrete Products of Wallingford, Conn., supplied all precast for the Route 17/Long Hill Brook replacement bridge. — CTS Cement Manufacturing Corp., Cypress, Calif.; www.ctscement.com