Thomas Brook Rail Bridge Replacement

Photo by Sebastian Bennage, courtesy of Sargent Corp.

Instead of doing most of the work during the shutdown, the team increased early phase activity to rehearse installation methods and confirm tolerances before the railroad shut down. Although more work was moved to the critical window, the method allowed crews to work at full efficiency during the shutdown of rail operations. Working continuously during the outage, crews coordinated the excavation, foundation preparation and placement of a 170-foot precast arch sewer system. A total of 67 precast concrete elements, fabricated off-site, were delivered and installed to sub-inch accuracy. Digital survey control and pre-pour dimensional checks ensured that each part fit as intended, eliminating field adjustments. The concrete was supposed to cure in 12 hours, said Brent Williams, Sargent project executive. “You pour it in and as soon as the water hits it, it sets,” he said. “You have about a minute and it’s ready to go.”

The schedule was nearly disrupted when the quick-strength concrete needed for the capping pour was not available days before use. Because the pours needed to reach a strength of 5,000 psi in hours to allow filling and restoration of the runway, the team quickly evaluated alternative mixes, verified performance through testing, and secured specialized miniature mixers to avoid premature setup to avoid downtime during the shutdown.