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2015WinterShotcreteEMag

Thus, minimizing the out-of-service periods was crucial to the project’s budgetary concerns. The shotcrete application process allowed for a way to quickly make the repairs without sacrificing the quality and safety of the finished rehabilitation (refer to Fig. 3). The project consisted of the following primary activities: overhead beam strengthening, large spall repairs at interior beams and stairwells, and restoration of the exterior concrete façade. The overhead portion consisted of a tight lattice work of reinforcement with two horizontal No. 4 (No. 13) reinforcing bars at the top and two No. 7 (No. 22) reinforcing bars at the bottom of the beams, No. 4 (No. 13) stirrups at 12 in. (305 mm) on center, No. 4 (No. 13) reinforcing bar dowels at 12 in. (305 mm) on center with a 90-degree hook, and 5/8 in. (16 mm) diameter threaded rod at 18 in. (457 mm) on center horizontal through existing beams. The gap between existing beams was filled, creating a section totaling 13 in. (330 mm) thick and 12 in. (305 mm) wide between beams. Cores taken from repaired sections proved there was a solid bond between the new shotcrete and the Fig. 3: The final shotcrete rod finish minimized existing concrete of the structure (refer to Fig. 4). the amount of work at the face The vertical spall repair that occurred in the stair wells and on the exterior façade varied from Fig. 4: A core taken from an in-place test panel. Note near the top is a faint red line—this is the tile layer seen in previous photos. In the 13 in. (330 mm) thick overhead section, ACI Certified Nozzlemen were able to achieve a solid bond without any separation between the new shotcrete and existing material. Due to the length of the Fig. 5: The exterior façade that has been core, it was not possible to drill through the chipped back to sound material and reinforcing length without breaking during the extraction bar installed Shotcrete • Winter 2015 51


2015WinterShotcreteEMag
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